Control System for Electromagnetic Environmental Testing of Electronics …398251/... ·...

Control System for Electromagnetic

Environmental Testing of Electronics with

Reverberation Chamber

Erik Olofsson, Jonny Jakobsson

February 13, 2010Master’s Thesis in Physics, 30 credits

Supervisor at Combitech AB: Tony Nilsson, Mats BackstromExaminer: Bertil Sundqvist

Umea UniversityDepartment of Physics

SE-901 87 UMEASWEDEN

Abstract

A reverberation chamber is a highly conductive cavity in which it is possible to generatehigh electromagnetic fields that can be considered statistically homogeneous. Reverbera-tion chambers have existed as a resource for electromagnetic compatibility (EMC) testing formore than 30 years. Working to promote international co-operation on standardization, sev-eral organizations have published various EMC standards. At Combitech AB in Linkopinghave a chamber that is commercially used for different types of measurements. To makethe chamber more attractive and versatile it is within their interest to get a system whichis compatible with the latest standards. The project aimed to develop a control system forthe reverberation chamber at Combitech and to equip it with functionality enabling it tomake measurements according to current EMC standards. Using the programming softwareAgilent VEE a program was developed to communicate with the supporting equipment andmanage test routines. Within the program software lies functionality directly associate withmode stirring and mode tuning procedures for standards DO-160F and MIL-STD. Duringmeasurements the program has abilities for skipping frequencies, pause/continue the currentsweep, executing preset events and adding commented markers to the plot window. Someother usable functionality implemented is project save/load, help section, directory selectionand data export abilities. The system holds functionality enabling measurements accordingto the standards in question, though future work will be needed to be able to carry througha proper and correct measurement routine.

Acknowledgements

The thesis project is a mandatory and graduating part of the 4,5 year master programmein Engineering Physics programme at Umea University. The project extent is 20 weeks andwas carried out at Combiteh AB in Tannefors, Linkoping, Sweden.

We would like to thank Combitech for giving us the opportunity to carry out this project.Many thanks to everyone working at Combitech, for helping us and making the time therevery enjoyable.

We would especially like to direct a warm thank you to the following people: our supervisorsTony Nilsson and Mats Backstrom for supporting the work during the project, Tomas Nilzonfor helping us in the laboratory and our examiner Bertil Sundqvist at Umea University.

i

Contents

1 Introduction 1

2 Problem Description 32.1 Problem Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.3 Purposes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.4 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.5 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.6 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.7 Restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3 Theory 73.1 Electromagnetic compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2.1 Spectrum analyzer (spectral analyzer) . . . . . . . . . . . . . . . . . . 83.2.2 Signal Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2.3 Electronic Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2.4 Receiving/Transmitting antennas . . . . . . . . . . . . . . . . . . . . . 93.2.5 Field probe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.2.6 Stirrer System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 Reverberation chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.4 Field Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.5 Antenna factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.6 Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.7 E-Field in the Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.8 Requirements and test procedures . . . . . . . . . . . . . . . . . . . . . . . . 16

3.8.1 RTCA/DO-160F Standard . . . . . . . . . . . . . . . . . . . . . . . . 163.8.1.1 Radiated Susceptibility (RS) Test; Alternative Procedure -

Reverberation Chamber . . . . . . . . . . . . . . . . . . . . . 163.8.1.1.1 Calibration (Mode Tuning) . . . . . . . . . . . . . . 16

3.8.1.1.1.1 Procedure . . . . . . . . . . . . . . . . . . . . 163.8.1.1.2 Chamber loading . . . . . . . . . . . . . . . . . . . . 193.8.1.1.3 Test Procedure (Mode Tuning) . . . . . . . . . . . . 20

3.8.1.2 Radiated Emissions (RE) Test; Alternative Procedure - Re-verberation Chamber - mode stirring . . . . . . . . . . . . . 21

3.8.1.2.1 General requirements . . . . . . . . . . . . . . . . . 213.8.1.2.2 Insertion Loss . . . . . . . . . . . . . . . . . . . . . 223.8.1.2.3 Radiated RF Emission test . . . . . . . . . . . . . . 22

iii

iv CONTENTS

3.8.1.2.4 Equipment categories for RF emission . . . . . . . . 233.8.2 MIL-STD-461F Standard . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.8.2.1 Test Procedure - Reverberation chamber (mode-tuned) . . . 243.8.2.2 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243.8.2.3 EUT testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 253.8.2.4 Thresholds of susceptibility . . . . . . . . . . . . . . . . . . . 263.8.2.5 Chamber time constant . . . . . . . . . . . . . . . . . . . . . 26

3.9 Agilent VEE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273.9.1 Developer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273.9.2 Visual programming language (VPL) . . . . . . . . . . . . . . . . . . . 273.9.3 Dataflow programming . . . . . . . . . . . . . . . . . . . . . . . . . . . 273.9.4 Dataflow functionality in VEE . . . . . . . . . . . . . . . . . . . . . . 283.9.5 Integrated Matlab Engine . . . . . . . . . . . . . . . . . . . . . . . . . 283.9.6 .NET Framework Integration . . . . . . . . . . . . . . . . . . . . . . . 28

3.9.6.1 Common language runtime (CLR) . . . . . . . . . . . . . . . 293.9.6.2 .NET Framework class library . . . . . . . . . . . . . . . . . 30

3.9.7 Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4 Results 334.1 Drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334.2 RC software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

4.2.1 Welcome screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374.2.2 Main window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374.2.3 File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

4.2.3.1 New project . . . . . . . . . . . . . . . . . . . . . . . . . . . 404.2.3.2 Open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404.2.3.3 Save . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404.2.3.4 Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4.2.3.4.1 RF Generator . . . . . . . . . . . . . . . . . . . . . 404.2.3.4.2 Spectrum Analyzer . . . . . . . . . . . . . . . . . . 414.2.3.4.3 Pre Selector . . . . . . . . . . . . . . . . . . . . . . 42

4.2.3.5 Sweep events . . . . . . . . . . . . . . . . . . . . . . . . . . . 434.2.3.6 Center marker . . . . . . . . . . . . . . . . . . . . . . . . . . 444.2.3.7 Sweep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444.2.3.8 New Sweep . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.2.3.9 Power On/off . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.2.3.10 Sweep Frequency list . . . . . . . . . . . . . . . . . . . . . . 494.2.3.11 Exit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.2.4 Stirrer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504.2.4.1 Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504.2.4.2 Reset Controller . . . . . . . . . . . . . . . . . . . . . . . . . 524.2.4.3 Run Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . 524.2.4.4 Connect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524.2.4.5 Disconnect . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534.2.4.6 Run Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

4.2.5 Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544.2.5.1 Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544.2.5.2 Frequency List . . . . . . . . . . . . . . . . . . . . . . . . . . 554.2.5.3 Skip Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . 56

CONTENTS v

4.2.5.4 Go to Value . . . . . . . . . . . . . . . . . . . . . . . . . . . 574.2.6 Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

4.2.6.1 Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584.2.6.2 Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604.2.6.3 Adjust strength . . . . . . . . . . . . . . . . . . . . . . . . . 614.2.6.4 Go to value . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634.2.6.5 Step up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634.2.6.6 Step down . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

4.2.7 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644.2.7.1 DO160-F/MIL/IEC . . . . . . . . . . . . . . . . . . . . . . . 64

4.2.8 Plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644.2.8.1 Export data . . . . . . . . . . . . . . . . . . . . . . . . . . . 644.2.8.2 Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644.2.8.3 Close All . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

4.2.9 View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654.2.9.1 Toolbar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654.2.9.2 Status Bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

4.2.10 Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654.2.10.1 Program content . . . . . . . . . . . . . . . . . . . . . . . . . 65

4.2.11 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664.2.11.1 Instrument communication . . . . . . . . . . . . . . . . . . . 664.2.11.2 Stirrers communication . . . . . . . . . . . . . . . . . . . . . 67

4.2.12 Software to Controller communication . . . . . . . . . . . . . . . . . . 68

5 Conclusions 715.1 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 725.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

References 75

A Tables 77

B Figures 81

C Work Distribution 85C.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85C.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Chapter 1

Introduction

Combitech AB is one of Sweden’s largest consultancies and is an independent companywithin the Saab group. Combitech is combining technology with environment and securityawareness. The company has approximately 800 employees which operate in twenty citiesin Sweden, but also in Norway and Germany. Areas of work for Combitech are: Informa-tion security, System integration, Mechanics, Systems security, Systems development andLogistics. The part of Combitech where we have done our project is located in Tannefors,Linkoping. This group is mainly targeted against electromagnetic compatibility (EMC).The company says: ”Today is EMC a part of our everyday work”. This means that they areworking as a support to all parts in the chain that compound today’s project development:from specification of requirements to verification and validation. Combitech aims to havecompetence and facilities to meet today’s and future challenges on the EMC-area. Theyoffer services within counseling, analysis, testing, design support, education and simulations.

One of the resources at Combitech is a reverberation chamber. The chamber is a largemetal cavity which works almost as a microwave oven. It is used for testing different typesof electromagnetic compatibility. The main advantage with the cavity is that from a lowinput power is it possible to get high field strength due to resonance of the electromagneticwaves. Combitech is in need of a new control system for the chamber that fulfills both civiland military standards. The aim of the project is to create a program software that controlsthe stirrers in the chamber, the field generator and the measuring devices. The programshould be able to run a test sweep, collect information and present it, all with a user friendlyinterface. Flexibility is important when instrument setup often changes.

The first part of the report is the problem description which states the problems that theproject will solve. It also covers goals, purpose and methods for the project. In the theorychapter is an explanation of the concepts and theory behind a reverberation chamber andhow to perform a test. This chapter also covers the theory behind basic equipment whenconducting EMC tests. The result chapter explains how the developed program softwareworks, what it can do and how it communicates with stirrers and instruments. The lastpart is the conclusion where the result is discussed and future work is suggested.

1

2 Chapter 1. Introduction

Chapter 2

Problem Description

2.1 Problem Statement

Reverberation chamber techniques came primarily as a result of poor repeatability and mea-surement accuracy in shielded-room EMC testing. With enhanced theoretical models thereverberation chamber has, during the latest decade, become a useful tool supported byseveral EMC standards. The current system for conducting tests with the reverberationchamber at Combitech does not hold the possibility to make tests according to the newercivil and military requirements. There are limitations within the current program softwareand no newer commercial software options are available. There are also equipment compat-ibility limitations and the knowledge around the software structure is not entirely withinthe company.

2.2 Goals

The project goal is to develop a new control system for the reverberation chamber at Com-bitech, with the intention to increase the number of different types of measurement pro-cedures available for the chamber and thereby make it more attractive to customers. Themain goals of the project can further be listed as follows:

• Program software should be flexible and have a user-friendly and logical user interface.

• Working communication between program software and equipment/instruments.

• Working communication between program software and stirrer controller.

• Integrate two out of three standards into the program software.

2.3 Purposes

Procedures and theory regarding reverberation chambers are under constant discussion. Thecontent and procedures in the standards can therefore be expected to be updated in the nearfuture. If a total reformation of the system with external competence would be expensivethen the project is a good compromise to following the development of the standards butminimizing the risk of ending up with an expensive system that could soon be out of date.

3

4 Chapter 2. Problem Description

The main purpose of the project is to update the old system and to create a new systembase consisting of solutions and procedures required by newer standard requirements forEMC testing. The knowledge around the system is also intended to be integrated withinthe department rendering the possibility of adding routines and updates to the system tofollow the future development of standards.

2.4 Methods

Within the project access is given to the entire test facility together with documentationof standards. The main tool during the project is the new programming software AgilentVEE used to set up overall control and link together communication of the system. Theold system used an ISA interface connection between the personal computer and the stirrercontroller. The new system should use a newer interface (LAN) and so the connectionand communication is to be rebuilt. Another communication interface introduced is GPIB(general purpose interface bus), where connection should be established between the softwareand supporting equipment and instrumentation. In Agilent VEE we will have to builda whole new program with a user friendly GUI (Graphical user interface) and to equipit with suitable procedures and logical functions. Influences to program layout, routinesand procedures are mainly found in older program software’s and documents describingstandards.

2.5 Related Work

As the reverberation chamber has been used with EMC applications for more than 30 years,extensive theoretical research has been done on the subject during the years and you cantoday find various reverberation chambers with different shapes for different applications.The first standardized methodology using reverberation chamber was the MIL-STD (Mil-itary standard) 1377, which came in 1971 [1] and handled shielding effectiveness of cablesand enclosures. Up until today standards have arisen and been revised to follow the theo-retical progress. When it comes to reverberation chamber measurement systems, they canvary a lot in chamber form, equipment and program software. Influences for this projectwill mainly be previous measurement systems and softwares for the reverberation chamberat Combitech.

2.6 Limitations

An issue is the ability to maintain the chamber as a commercial resource while rebuilding thesystem. During the development it should be easy to switch back and run tests accordingto the old setup. The reverberation chamber and equipment will also be inaccessible for usduring time used by customers. Delivery time for the new controller will result in partialcode generation without being able to test its compatibility with the controller system.The system is required to be flexible in the ability to change supporting equipment, whichrestricted parts of the program software.

2.7. Restriction 5

2.7 Restriction

As the chamber at test generates dangerously high field strengths there are restrictions andprecautions needed when running tests and handling certain equipment.

6 Chapter 2. Problem Description

Chapter 3

Theory

This chapter covers the theory needed to understand electromagnetic compatibility (EMC)testing. The basic concept of EMC is first presented. Then follows a description of theequipment needed, theory on how the electric field is created, statistical properties in thechamber and factors needed to adjust the measured field. The last part of the theory is asummary of how to perform a test according to MIL and DO-160F standards.

3.1 Electromagnetic compatibility

The phenomenon that spark gaps generate electromagnetic waves rich in spectral contentwhich can cause interference or noise in various electric devices is commonly known. Elec-tronic devices functioning with other electronic equipment in the surroundings without gen-erating or being vulnerable to interference is considered to be electrically compatible withthe environment. The conditions for a system to be electromagnetically compatible are [2]:

1. It does not cause interference with other systems.

2. It is not susceptible to emissions from other systems.

3. It does not cause interference with itself.

Electromagnetic energy transfer can be further divided into several subgroups: radiatedemission, radiated susceptibility, conducted emission and conducted susceptibility. The im-portance of meeting the EMC requirements is not just satisfactory performance, but thereare also legal requirements to be able to distribute equipment commercially.

To limit the electromagnetic emission of electric systems there are standards publishedin document form. The performance specifications in a standard are generally the minimumrequirements for an adequate function within the permitted design tolerances when workingin their proposed environment. In most countries there are national agencies suppressingstandards or regulations concerning electromagnetic emission, with the military being moredetailed and strict. In a growing fraction of European countries standards concerning elec-tromagnetic emission and immunity to electromagnetic emission are compulsory even fornon-military applications for commercial use.

7

8 Chapter 3. Theory

3.2 Equipment

The equipment involved in basic EMC testing and calibration with a specified reverberationchamber is:

1. Spectrum analyzer (spectral analyzer)

2. Field probe

3. Transmitting/Receiving antennas

4. Electronic amplifier

5. Stirrers

Here follows a short description of the individual equipment:

3.2.1 Spectrum analyzer (spectral analyzer)

A spectrum analyzer is mainly used to reproduce spectral composition or power spectrumof some connected signal [3].

The analog spectrum analyzer can either use a variable band-pass filter which is auto-matically tuned over a range of frequencies that corresponds to the measurement spectrum.A superheterodyne receiver can also be used. A local oscillator signal tuned over a rangeof frequencies is then mixed with the input signal, to convert the processed signals to moreconvenient frequencies.

A digital spectrum analyzer (FFT Analyzer) mathematically processes a sampled wave-form into its frequency spectrum with a Discrete Fourier Transform (DFT). Some can evenmix the above described techniques; one example is the real-time spectrum analyzer. Theprocessed signal is first down-converted in frequency using heterodyning and then analyzedwith Fast Fourier Transformation (FFT) techniques.

3.2.2 Signal Generator

Signal generators produce repeating or non-repeating electronic waveform signals in eitherdigital or analog form [4]. Newer generators produce waveforms with digital signal pro-cessors and use a digital to analog converter (DAC) to create an analog output. Signalgenerators have the ability to produce sine wave signals in the range from low frequencyup to many GHz. Typical features of a signal generator are attenuation, modulation andsweeping.

3.2.3 Electronic Amplifier

The electric amplifier takes a signal from a power supply and generates a new high poweredsignal together with waste heat by matching the output signal with the input signal [5].Amplifier manufacturers always strive to reduce the resistance of the amplifying circuitelement. This increases efficiency and minimizes power waste, which allows transistors,tubes or other amplifying parts to run cooler and hence be more reliable.

3.3. Reverberation chamber 9

3.2.4 Receiving/Transmitting antennas

Antennas are used for transmitting or receiving electromagnetic waves in the chamber.The most important property for the receiving and transmitting antenna in a reverberationchamber is the bandwidth. The bandwidth is the range of frequencies where the antenna canradiate or receive energy properly. Other properties like directivity, gain and polarizationare lost in the chamber due to the resonance phenomena.

3.2.5 Field probe

A field probe consists of three independent broadband antennas oriented orthogonally whicheach measures one component of the electric field. The signal from the probe is transmitteddigitally through a fiber optical link to a read out unit or computer. The RMS (root meansquare, effective value) value for the three components of the field represents the summedtotal field [6].

Compared to antennas connected to a spectrum analyzer where the analyzer differentiatesbetween frequencies, the field probe responds to all active frequency components. Conse-quently a clean signal in an immunity testing setup is vital, particularly the harmonic fieldgenerated by a power amplifier.

3.2.6 Stirrer System

The stirrers are large metallic reflectors whose main purpose is to change the boundarycondition inside the reverberation chamber. The design of the tuners can also alter thelowest usable frequency for the chamber. During the rotation of the stirrers the standingwave pattern in the chamber will be altered and every point in the working volume will besubjected to the same maximum, minimum and average electromagnetic field. The chamberfulfilling this condition is called well-stirred hence granting a statistically isotropic field forEMC/EMI testing.

3.3 Reverberation chamber

A reverberations chamber (Figure 3.1) is a highly conductive cage, which is electricallyshielded from the outside. Highly conductive implies that the material of the chamber hasa low absorption of the field. Because of the shielded environment it is possible to get highfield strengths from a relative low input power. The electric field in the chamber is mixedby stirrers to get a uniform field. A uniform field is reached when almost every point in thechamber, over a complete rotation of the stirrer, is exposed to the highest field strength. Anisotropic field has the drawback that the information about polarizations and directionalproperties is lost. Reverberation chambers are useful in electromagnetic compatibility testsfor several reasons. Some of the advantages are: it is easy to get strong fields from lowinput power, good repeatability for several tests, cost effective test procedure and wellknown statistics, which means that errors can be calculated. There are also drawbacks witha reverberation chamber. One is that it is sometimes hard to relate the environment in thechamber to the real world. Another one is that the lowest usable frequency (LUF) is relativehigh, which can be a problem when the lower frequencies are important.

10 Chapter 3. Theory

Figure 3.1: A computer model of the reverberation chamber at Combitech AB

Reverberation chambers can differ in size. Smaller chambers have the advantage of higherfield strengths than the larger chambers, but the disadvantage of higher LUF. Larger cham-bers have lower LUF but also lower field strength compared to a small one. The LUFdepends on the chamber dimensions and its quality factor. To derive this relation it isnecessary to understand how the field is created in the chamber.

Constructive interference will occur for frequencies that match with chamber dimensions.Resonance frequencies for a rectangular chamber can be derived by using solutions for thecorresponding waveguides given by Maxwell’s equations. The equation for the propagationconstant for TE (transverse electric) and TM (transverse magnetic) modes is

β2nm = k20 −

(nπa

)2−(mπb

)2, (3.1)

where n, m are constants and a and b are two dimensions of the chamber [7]. k0 is theangular wave number

k0 =2π

λ=

2πf

c, (3.2)

where λ is the wave length, c is the speed of light and f is frequency [8].

A resonance wave arises when the wavelength matches the length of the chamber. This iswhen the length of the chamber is a multiple of half of the wavelength. From this comes arequirement that the propagations constant has to be the ratio between a multiple of thehalf wavelength and the length of the chamber in the propagation direction d as

βnm =lπ

d, l = 1, 2, 3... (3.3)

3.3. Reverberation chamber 11

[7]. Solving for k0 in equation 3.1 together with equation 3.3 to get the angular wavenumbers corresponding to the resonance frequencies gives

kmnl =(mπb

)2+(nπa

)2+

(lπ

d

)2

. (3.4)

The resonance frequencies(fr) are derived by using equation 3.2 together with 3.4 as

fr = fmnl =c

2

√(mb

)2+(na

)2+

(l

d

)2

(3.5)

where m, n, l are constants, and at least two have to differ from zero. a, b, d are the chamberdimensions.

The electromagnetic signal that is transmitted into the chamber can create a standing wavepattern (a mode) if it is a resonance frequency or close to one. One mode can be consideredexcited if the transmitted frequency is inside a 3 dB bandwidth from a resonance frequency.This frequency area is given by the frequency band (∆f) and depends on the quality factor(Q) for the chamber as

∆f =frQ

(3.6)

[9]. The quality factor Q is a measure of how well the walls reflect the signal power trans-mitted into the chamber. A large Q value gives a small band of frequencies that will beexcited but on the other hand a good reflection of the strength. A small Q value gives a wideband of excited frequencies but less reflected field strength. The Q-value for a reverberationchamber can be calculated as

Q =16π2V

λ3

⟨PrPt

⟩(3.7)

.[9] The function of a reverberation chamber is dependent on the number of possible modesthat can be excited around the transmitted signal. The neighboring resonance frequencieshave to be close enough to each other for the modes to overlap (overmoded). When thishappens it is likely to get high and constant field strength inside the chamber. In the case oflow or no overlap (usually for lower frequencies and high Q value) there is a high probabilityto get large differences in field strength between different points in the chamber. Frequen-cies close to a resonance frequency will cause large field strength while other frequencies willproduce an almost zero field strength.

The criterium for a sufficient amount of modes (N) is usually satisfied by saying that thereshould be at least a certain number of modes up to the lowest usable frequency,

N =8πV

3

(f

c

)3

− (a+ b+ d)

(f

c

)+

1

2(3.8)

where V is the volume.[9]

The density of modes that is excited for a given frequency are obtained by taking thederivative of equation 3.8 as

dN

df=

8πV

c3f2 − (a+ b+ d)

1

c≈ 8πV

c3f2. (3.9)


Using df = ∆f from equation 3.6 gives the number of modes that are simultaneously excitedas

Ns =8πV f3

c3Q. (3.10)

3.4 Field Statistics

When NS is considered large (overmoded) the chamber is very large compared to the wave-length and the number of modes is sufficient. When deriving statistical distributions forthe chamber NS →∞ is assumed. As stirrers are introduced in the reverberation chambertheir movement alters the boundary conditions. The result is an electric field where theamplitude in every given position is a sum of multipath plane waves with random phases.A three dimensional electric field vector

E = Ex + Ey + Ez (3.11)

consists of a real as well as an imaginary part according to

Ex,y,z = Re(Ex,y,z) + iIm(Ex,y,z). (3.12)

Stirrer movements generate a large collection of waves in different directions. The real andimaginary components of the wave can, according to the central limit theorem, be considerednormally distributed. Considering the chamber to be ideal and taking into account that thereal and imaginary parts of the rectangular components are non-correlated, the mean andmean square fields has relations

〈Re(Ex,y,z)〉 = 〈Im(Ex,y,z)〉 = 0 (3.13)

and

〈Re(Ex,y,z)2〉 = 〈Im(Ex,y,z)2〉 ≡ σ2. (3.14)

From statistical theory the variance of a random variable can be derived as

σ2 =1

N

N∑i=1

(xi − 〈x〉)2 (3.15)

[10]. Taking into consideration the relations in equations 3.13 and 3.14, the variance ac-cording to equation 3.15 becomes

σ2 =1

N

N∑i=1

(Ei − 0)2 =E2

0

6. (3.16)

E20 is the mean square of the electric field magnitude E. All six parameters are normally

distributed around a zero mean with a variance σ2, which consequently makes the squareof the magnitude of the field chi-square (χ2) distributed and the magnitude of the resultantfield chi (χ) distributed. Six random parameters lead to both distributions having six de-grees of freedom.

3.4. Field Statistics 13

From statistical theory a χ2 distribution with n degrees of freedom can be derived as

fY (y;n) =1

σn2n/2Γ

(12n

)y(n/2)−1e−y/2σ2

(3.17)

[11], for y ≥ 0. Y have the relation Y = X2 where X is a Gaussian random variable. Γ isthe Gamma function defined as Γ(n) = (n − 1)! if n is a positive integer. Hence with sixdegrees of freedom the respective probability density function become

fY(|E|2

)=|E|4

16σ6exp

[−|E|

2

2σ2

](3.18)

and

fY (|E|) =|E|5

8σ6exp

[−|E|

2

2σ2

](3.19)

[12]. Measurements are commonly taken with a linearly polarized antenna which resultsin one rectangular component and two parameters of the electric field. The χ distributionwill in this case hold two degrees of freedom and the probability density functions havethe characteristics of a Rayleigh distribution. The Rayleigh probability density function isdefined as

f(x;σ) =x

σ2exp

[−x2

2σ2

](3.20)

[13] for x ∈ [0,∞), with cumulative distribution function

F (x;σ) = 1− exp[− x2

2σ2

]. (3.21)

Hence the density functions become

f (|Ex,y,z|;σ) =|Ex,y,z|σ2

exp

[−|Ex,y,z|

2

2σ2

](3.22)

and

F (|Ex,y,z|;σ) = 1− exp[−|Ex,y,z|

2

2σ2

](3.23)

respectively [12].

The chamber electric field uniformity is related to the discrete number of stirrer positions asit generates new uncorrelated fields. An E-field measurement at a given position can ideallybe considered distributed according to statistical distributions either by stirrer movement orby placing the measurement point at a new position. In a correctly working chamber envi-ronment where this condition is fulfilled the electric field is considered statistically isotropic.A χ2-hypothesis test is a relatively easy procedure that can be used to test probability mod-els. This is often used to verify the chambers’ ability of demonstrating isotropic behaviorwith a series of uncorrelated E-field measurements at a given position.


3.5 Antenna factor

The Field strength inside a chamber is measured by an antenna and transmitted to ameasuring device. The value measured is the voltage over the antenna, but the value ofinterest is the magnitude of the field per meter. Conversion between the measured fieldstrength and the field strength per meter can be done by using the antenna factor(AF ),

AF =E

UA, (3.24)

where E is the total electric field in the chamber and UA is the average voltage over theantenna.(Equations used to derive the antenna factor are only valid for the average electricfield in a reverberation chamber.)

The total electric field in the chamber is derived by using the receiving cross section for anantenna as

σr =λ2

4πGrpq, (3.25)

where λ is the wavelength, Gr is the gain of the receiving antenna, p is the polarizationfactor and q is the impedance mismatch factor [9].

The average power received (Pr) by the antenna is given by multiplying the receiving crosssection(σr) by the power density S of the chamber.

Pr = σrS =λ2

4πGrpqS (3.26)

The power density is calculated by dividing the electric field with the impedance (Zc) of thechamber [14].

S =E2

Zc, (3.27)

The average power received by the antenna is calculated by taking the average measuredvoltage (U) from the antenna and dividing that by the system impedance (Zs) as

Pr =U2

Zs. (3.28)

Equations 3.27 and 3.28 are substituted into equation 3.26 as

U2

Zs=λ2

4πGrpq

E2

Zc. (3.29)

Equation 3.29 may now be solved for EU and substituted into 3.24 to get a new expression

for the antenna factor as

AF =

√Zc4π

Zsλ2Grpq. (3.30)

3.6. Losses 15

The wavelength can be rewritten as λ = fc .The impedance of the chamber Zfreespace can

be assumed to be the impedance for free space which is approximated by 120π. The polar-ization is assumed to be p = 1

2 for a reverberation chamber because it is either zero or onewith an average of 1

2 . There is no gain in an isotropic environment, so Gr is equal to one.q is assumed to be one.

The final expression for the antenna factor in a reverberation chamber is an approxima-tion for the maximum total field instead of the average total field and is

AFtotal =

√960π2

Zsystem

c

f. (3.31)

It should be noted that this is not a good approximation, which is showed in [15].

The rectangular component of the maximum total field is given by taking AFrectangular =1√3AFtotal (the square root is because it is an squared relationship between power and

electric field, P = E2) as

AFrectangular =1√3

√960π2

Zsystem

c

f=

√320π2

Zsystem

c

f. (3.32)

It has been shown that the equation 3.32 is a good approximation for the rectangular com-ponent of the antenna factor for the maximum electric field [15].

The electric field in the chamber can now be calculated by taking the measured voltagemultiplied by the antenna factor as

Echamber = UA ·AF. (3.33)

3.6 Losses

The signal in the chamber is received by an antenna which has internal losses. The signalis then transmitted from the chamber to a measuring device. This is done through cableswhere the signal also loses strength. These losses have to be corrected for by multiplyingthe E-field equation 3.33 by a loss term L as

Echamber = UA ·AF · L. (3.34)

3.7 E-Field in the Chamber

The E-field in the chamber is often presented in decibel instead of in voltage per meter. Theconversion of equation 3.34 is done as

Echamber,dB = 20 log (UA) + 20 log (AF ) + 20 log (L) . (3.35)


3.8 Requirements and test procedures

This section covers an interpretation of the two standards RTCA/DO-160F and MIL-STD-461F. It should be read as an overview of the standards where the focus has been onprocedure and instrument setup.

3.8.1 RTCA/DO-160F Standard

This standard is an updated version of the EMC requirements for commercial avionics thatare intended to reflect the “state of the art in aviation technology and EMC testing method-ology” and could be related to every type of aircraft in use today. The update was made byRTCA (Radio Technical Commission for Aeronautics) Special Committee 135 in an attemptto meet FAA (Federal Aviation Administration) or other international regulations regard-ing equipment that is installed on commercial aircraft. During creation and modificationthere was collaboration with the European Union version of RTCA, EUROCAE which hasreleased the standard under the name EUROCAE/ED-14F [16].

3.8.1.1 Radiated Susceptibility (RS) Test; Alternative Procedure - Reverber-ation Chamber

The test is intended for susceptibility measurements between 100 MHz to 18 GHz and aimsto simulate and qualify equipment for natural occurring RF-levels. In certain cases moretests can still be appropriate.

The theory of chapter 3.8.1.1 is derived in more detail in the document by RTCA [17].

3.8.1.1.1 Calibration (Mode Tuning)

For the field to be considered uniform requirements for the number of discrete stirrer stepshas to be fulfilled. Verification must be done with an empty chamber after constructionor major modifications. The Lowest test frequency (fs) is 100 MHz and field uniformityshould be verified over one operational decade from any chosen start frequency above fs.It will be usable from the frequency where uniformity is first shown (LUF = Lowest usablefrequency). The test should be carried out at 9 test locations for all spatial axes (x, y andz), so in total 27 measurements points are to be considered. Operation with continuoustuning rotation (mode stirring) is not allowed.

3.8.1.1.1.1 Procedure

1. The working volume must first be cleared. (i.e. conductive test bench should beremoved)

2. The receiving antenna can be mounted at any location within the working volume,see Figure B.1.

3. The amplitude measurement instrument is then to be set on monitoring the frequencyfor the receiving antenna.

4. The optimum direction of the transmitting antenna is against one of the corners, asit shall not directly illuminate the working volume. It should be fixed at the sameposition during calibration and tests.

3.8. Requirements and test procedures 17

5. The E-field probe should be mounted on the border edge of the working volume ac-cording to Figure B.1

Note:

Surfaces of the working volume should not be distanced below 0.75 meter(λ/4 of the lowest test frequency) from chamber surfaces, stirrer assemblyor field generating antenna. This distance is also the lower limit for distancebetween probe and receiving antenna, i.e. every new measurement locationshould at least have this distance to any previous location. It may be re-duced provided that the separation distance is larger than λ/4 for the lowestfrequency, though below 1/4 meter is not recommended.

6. Starting at fs appropriate power (Pt) from the RF-source should be passed to thetransmitting antenna. The RF-source must be in frequency band of transmitting- andreceiving antennas. The antennas should both be linearly polarized.

7. Stepping stirrer(s) 360◦ in discrete steps is recommended as the field uniformity canhence be determined for fewer tuner steps. This enables altering the number of stepsfor tests depending on if possible high field or fast test time is of importance. Thesteps should still be sufficiently large to generate a new uncorrelated field at each stepand the number of positions should always secure the field uniformity requirements.Sufficiently long dwell time is important so that measurement instruments and E-fieldprobe can respond correctly.

Quantities measured over one stirrer rotation is:

7.1 Maximum magnitude of received power Pr,Max

7.2 Average magnitude of received power Pr,Rec (Watt)

7.3 Maximum field strength EMaxx,y,z for every axis of the E-field probe (27 mea-surements below 10fs and 9 above 10fs).

7.4 Total maximum field strength ETotal (root sum squared of the rectangular com-ponents).

7.5 Average transmitted power Pt,Ave (at least equal amount of samples as steps).

Note:

Calibrations are antenna specific and antenna efficiency (ratio of power ac-cepted to the total power at the measurement location) is required.

8. Measurement procedures in step 7 should be done in log spaced frequency steps ac-cording to Table A.1. The steps can in ascending order be calculated as

fn+1 = fn ∗ 10(1/t), (3.36)

where n is the current frequency, (n+ 1) the next and t the number of frequency stepsper decade. The number of steps m required between the start frequency f1 and endfrequency fm can hence be calculated as

m = 1 + t ∗ log(fm/f1). (3.37)


9. The procedure should be repeated for nine probe- and antenna positions until 10fs.Measurement positions should be spaced as in Figure B.1. Only three locations areneeded above 10fs, though one measurement position should always be in the centerof the working volume.

10. Measurement procedures in step 7 should then be carried out for the rest of thecalibration frequencies according to Table A.1.

Note:

Receiving antenna must be moved to a new location every time the probe ismoved. The antenna need also be rotated at least 20◦ around every chamberaxis (x, y, z) for each location.

11. With data from step 7 every maximal E-field measurement from the probe should benormalized by taking the square root of the average transmitting power according to

Ex,y,z =EMaxx,y,z√

Pt,Ave(3.38)

and

ETotal =EMaxTotal√

Pt,Ave. (3.39)

EMaxTotal is the total maximum of the total E-field from each probe measurementlocation. (9 measurements under 10fs and 3 above).

Receiving antenna calibration factor ACF should also be calculated for all frequenciesas it is later used for comparison with a loaded chamber. It is calculated as the ratioof average received power to input power as

ACF =

⟨Pt,AvePt,Ave

⟩n

, (3.40)

where n represents the number of measurement positions used at the current frequency(9 under 10fs and 3 above).

Note:

Pt,Ave for equations 3.38 and 3.39 is calculated as the average transmit-ting power during the stirrer lap when respective maximum (EMaxx,y,z andEMaxTotal) was measured.

12. For every calibrated frequency under 10fs the average normalized maximum is calcu-lated for every axis of the E-field as

〈Ex〉9 =(∑

Ex

)/9 (3.41)

and in the same way for 〈Ey〉9 and 〈Ez〉9.

The average of the normalized maximum of all 27 E-field probe measurements iscalculated as

〈E〉27 =(∑

Ex,y,z

)/27. (3.42)


13. Step 12 should be repeated for every frequency over 10fs. Because of the three mea-surement positions 9 should be replaced with 3 and 27 with 9 in equations 3.41 and3.42 respectively.

14. Confirming field uniformity is made by calculating the standard deviation from theaverage value of the maximum values gathered at each measurement position duringone stirrer rotation. Only frequencies below 10fs are to be considered.

14.1 Standard deviation is calculated as

σ = α ∗

√√√√∑(Ei − 〈E〉

)2n− 1

, (3.43)

where n is the number of measurements, Ei is a specific measurement of theE-field and α is 1.06 for n ≤ 1 and 1 for n ≥ 20. Expressed in dB the standarddeviation corresponds to

σ(dB) = 20 ∗ log

[σ + 〈E〉〈E〉

]. (3.44)

14.2 To establish field uniformity the standard deviation of the field components(σx,y,z) must not exceed the standard deviation specified in figure B.2 for morethan two frequencies per octave (within 3dB over 400 MHz and fall linearly from6 to 3 dB from 100 MHz to 400 MHz). The standard deviation for all vector com-ponents (σ27) must also not exceed specified standard deviation. If the chamberdoesn’t fulfill the terms it can’t be used at lower frequencies, though with a lowmargin it may be possible to get uniformity by

• Increasing the number of stirrer steps by 10 - 50 %

• Normalizing data against the chamber net input power (Pnet = Pt,Ave −Preflected)

• Reducing the size of the working volume.

With a confirmed uniformity condition the number of stirrer steps can be reduced,but not below 12 steps.

Note:

After modifications of the chamber setup (for instance added absorbent)or calibration, it is important that configuration/procedure stays the sameduring following tests for the calibration to be considered valid.

3.8.1.1.2 Chamber loading

This procedure should be run prior to test to check if the EUT has loaded the chamber.The EUT should not occupy more than 8 % of the chamber volume. The number of stirrersteps should be equal to the number chosen for the later equipment test procedure butthe frequency range with logarithmic steps should be the same as for the calibration. Thechamber calibration factor CCF is the normalized average received power over one stirrer


rotation and with EUT and other equipment present. It should be calculated at everyfrequency as

CCF =

⟨Pr,AvePt,Ave

⟩n,f

, (3.45)

where n is the number of antenna locations (only one is needed) and f the number offrequencies the value is averaged over. The chamber loading CLF factor is then calculatedas

CLF =CCF

ACF, (3.46)

and when calculated for a given frequency the ACF and CLF data sets can be averagedover up to 4 of the closest frequency values on both sides. If the magnitude of the chamberloading factor becomes too large the uniformity check has to be done again with an objectloading the chamber equally as the current EUT.

3.8.1.1.3 Test Procedure (Mode Tuning)

1. The transmitted power for every test frequency should be decided from the electricfield intensity category level in Table A.1 and equations

Pt =

[ETest

〈ETotal〉n ∗√CLF

]2(3.47)

and

Pt =E2Test

|ET |2max ∗ CLF. (3.48)

The categories determine the radio frequency test levels and may be prescribed bythe equipment performance standard. The choice of equation to be used dependson whether a measurement probe or a receiving antenna is used as calibration datareceiver. In equation 3.47 ETest is the demanded field strength (V/m) and 〈ETotal〉nthe average of the normalized maximal E-field. Interpolation between the calibrationfrequency points will be needed to get the normalized E-field calibration (E) for thetest frequencies.

In equation 3.48 |ET |2max is the squared maximum magnitude of the E-field defined as

|ET |2max =

⟨PAveRecPt ∗ ηrx

⟩∗ 8πη

λ2∗R, (3.49)

where R is the maximum to average ratio of the square magnitude of the E-fieldtabulated in table A.2. ηrx is the antenna efficiency factor which can be presumed tobe 0.75 for a log periodic antenna and 0.9 for a horn antenna. η is the wave impedanceof free space (120π) and λ the wave length (m).

2. The number of stirrer steps used for the test has to be considered, the minimumnumber of steps, still with a uniform field, will result in the highest input power butshortest test time.

3. Field strength is derived from Pt in step 3.47 and verification is made by noting thevalue from the receiving antenna.


4. The Frequency interval should be stepped through until the upper limit with appro-priate modulation, the carrier modulated according to field level categories as:

• Category R→From 100-400 MHz: 20 V/m CW and 20 V/m with 1 kHz squarewave modulation (at least 90 % depth).From 400 to 8 GHz: 150 V/m pulse modulated (4% duty cycle) and 1 kHz pulserepetition frequency. At 1Hz rate and 50% duty cycle switch off and on signal tosimulate the effect of rotational radars.

• Category S, T, W and Y→ CW from 100 MHz to the upper frequency (S = 2GHz, T = 8 GHz, W and Y = 18 GHz) and 1kHz square modulation (at least 90% depth). Additional modulations associated with the EUT can be considered.

• Category B, D, F, G and L→ From 100 MHz to 18 GHz when testing suitingSW/CW with accordance to table A.1: CW and 1 kHz square modulation (atleast 90 % depth). Additional modulations associated with the EUT can be con-sidered.From 400 MHz - 4 GHz: Pulse modulated (PM) test level with at least 4 µs pulsewidth and 1 kHz pulse repetition frequency.From 4 GHz - 18 GHz: Pulse modulated (PM) test level with at least 1 µs pulsewidth and 1 kHz pulse repetition frequency. For EUT with low frequency re-sponse consider switching the signal off and on at a 1 Hz rate and 50 % dutycycle

• All categories→ Above 1 GHz: Allowed to use SW modulation at 1.42*CW fieldstrength requirement to meet CW and SW requirements at the same time.

Dwell time has to be at least one second excluding equipment settling time. Additionaldwell time may as well be needed for ”off time” at low frequency modulation and forthe EUT to do internal operations.

5. While dwelling apply necessary measurements and evaluate functionality for EUTunder applicable performance standards.

3.8.1.2 Radiated Emissions (RE) Test; Alternative Procedure - ReverberationChamber - mode stirring

Radiated emission tests are done to ensure that the EUT doesn´t emit undesired RF noiseto the surrounding. Different equipment categories (see 3.8.1.2.4) have different limits (seeappendix B) for RF noise. The chamber must meet the field uniformity requirements ofsection 3.8.1.1.1 at or above 100MHz.

The theory of chapter 3.8.1.2 is derived in more detail in the document by RTCA [18].

3.8.1.2.1 General requirements

Important parts of the general requirements:

1. The peak detector time constant must be lower than or equal to 1/bandwidth. Videobandwidths should be equal to or greater than the resolution bandwidths.

2. For detecting time-varying emissions the dwell, sweep and measurement times may bechosen to a longer time than specified in Table A.4.


3. Recorded data should provide a minimum frequency resolution of 1% or twice themeasurement receiver bandwidth and minimum amplitude resolution of 1 dB.

3.8.1.2.2 Insertion Loss

It is necessary to make a measurement of the insertion loss before a radiated emission test.This measures how much of the input power that is lost from the transmit antenna to thereceiving antenna due to chamber properties and loading of the chamber. This measurementis done with the EUT in the chamber together with all support equipment. The EUT andother equipment should be turned off. The measurement of the insertions loss follows theprocedure below.

1. The spectrum analyzer should be in peak detector mode and the display set for peakhold

2. The RF generator should be set to sweep a range of frequencies given in Table A.4.The chosen minimum time for sweeping the frequency band should be divided by 100to get the spectrum analyzer sweep time. The Spectrum analyzer should use a 1 MHzIF BW. Time for one tuner rotation is calculated by multiplying the signal generatorsweep speed by 100. Signal generator sweep speed is calculated by dividing minimumsweep time for the frequency band by the frequency range.

3. The RF source should transmit a known input power (Pt) into the transmit antennaand record it in dBm.

4. The tuner should be rotated one revolution so that the measurement receiver capturesthe maximum power for every frequency.

5. The measurement receiver should save the maximum power measured (Pr) for everyfrequency.

6. Insertion loss (IL) for the reverberation chamber is calculated by

IL = (Pt − Lloss + (10log(η))− Pr) (3.50)

where Lloss=Transmit antenna line loss in dB, η=Transmit antenna efficiency. Theantenna efficiency can be assumed to be 0.75 for a log periodic antenna and 0.9 for ahorn antenna.

3.8.1.2.3 Radiated RF Emission test

Total RF emission is calculated by adding insertion loss from calibration to the measuredRF emission power. During the test the EUT and support equipment shall be powered andhad time to stabilize. Before starting, the EUT should be tested for normal operation.

1. Operating mode of the EUT should be chosen to be the one that produce maximumemission.

2. The transmitting antenna should be terminated outside the chamber with a 50 ohmload.

3. The measurement receiver should monitor the receiving antenna at the bandwidthspecified in Table A.4.


4. The measurement receiver should be in peak detection mode and the display on peakhold.

5. The sweep time for the measurement receiver should be set to the value specified inTable A.3 for the minimum sweep time of the frequency band. Sweep time of themeasurement receiver should be multiplied by 200 to obtain the time for one tunerrotation.

6. The stirrer should be rotated one full rotation so that the measurement receiver cap-tures the peak power from the receiving antenna across the chosen range of frequencies.

7. EUT RF emission power should be calculated by using

Pt =10(Pr+IL)/10

1000, (3.51)

where Pr=max power in dBm from the receiving antenna, IL=insertion loss in dB.

8. Electric field strength E should be calculated by using

E =

√DPt377

4π, (3.52)

where E is the field strength in volts per meter, D=1.64, which is the directivity ofthe EUT and is assumed to be equivalent to that of a half wave dipole antenna.

9. Electric field emissions (dbuV/m) should be calculated as

dBuV/m = (20log(E)) + 120 (3.53)

where E=field strength in volts per meter.

10. The emission measured should then be checked by applying the appropriate limit fromfigures: B.3, B.4,B.5 and B.6 for the different categories 3.8.1.2.4.

11. the ambient radiated RF (EUT ”off”’ and test support equipment ”on”) should thenbe measured to check if emissions are higher than the selected category 3.8.1.2.4 limitminus 3 dB. It is desirable that the ambient emissions should be at least 6 dB belowthe selected category limit.

3.8.1.2.4 Equipment categories for RF emission

1. Category B:For equipment where interference should be controlled to tolerable levels.

2. Category L:For equipments that is located far from apertures and a radio receiver´s antenna.Suitable for equipment and associated interconnecting wiring located in the electronicbay of an aircraft.

3. Category M:For equipments and interconnected wiring located in any areas where apertures areelectro-magnetically significant and not directly in view of radio receiver´s antenna.Suitable for equipment and associated interconnecting wiring located in the passengercabin or in the cockpit of a transport aircraft.


4. Category H:For equipment that is located in areas which are in direct view of a radio receiver´santenna. Applicable for equipments outside the aircraft.

5. Category P:For equipments and associated wiring located in areas close to high frequency, VHF, orGPS radio receiver antennas, or where the aircraft structure provides little shielding.

3.8.2 MIL-STD-461F Standard

Military standards MIL-STD-461 and MIL-STD-462 make a multifaceted collection of stan-dards in electromagnetic compatibility which was first introduced in 1967-68. MIL-STD-461refers to EMI/EMC stipulations for electrical, electronic, and electromechanical equipmentand subsystems [19]. MIL-STD-462 handles test process and detailed events to meet theterms for MIL-STD-461. Both documents have during the years been revised from D uptill today’s F version. The standard is mainly used by the U.S. Department of Defense, butmany other countries follow it closely or with slight variation. The EMI control levels withinthe standard should ensure electromagnetic compatibility for extensive hardware integrationbetween subsystems. Within the standard, tolerable levels concerning conducted emission,susceptibility and immunity to conducted emissions, radiated emission, and susceptibilityand immunity to radiated emission are presented.

3.8.2.1 Test Procedure - Reverberation chamber (mode-tuned)

This procedure is suitable to use for the frequency range from around 200MHz to 40GHz.MIL-STD-461F has the recommendation that if number of possible modes is less than 100for a given frequency, the chamber shouldn’t be used at or below that frequency. See equa-tion 3.8 for how to calculate number of possible modes [20].

The MIL standard specifies the maximum scan rate and the maximum step size for differentfrequency ranges which are shown in Table A.4. Both scan rates and step sizes are definedfrom f0 which is the start frequency for a sweep. It also specifies the number of stirrerpositions for different frequency ranges, as seen in Table A.5. A lower frequency gives ahigher number of stirrer positions, and a higher frequency gives a lower number of positions.This is because there have to be enough modes in the chamber to ensure that every pointin the chamber has the highest field value for some stirrer position.

3.8.2.2 Calibration

Calibration of the chamber is done to determine how much RF power that is needed to createdesired field strength inside the chamber. There is two types of calibration depending onwhatever a receiving antenna or an electric field probe is used.

• Receiving antenna procedure

1. An appropriate unmodulated input power (Pt) should be transmitted into thechamber at the start frequency.

2. The stirrers should be rotated one revolution with a minimum number of stepsgiven in Table A.5. The stirrer should dwell at each step longer than 1.5 timesthe response time for the measurement receiver. At each step should the field


strength be measured and the highest recorded field strength should be saved,Pr,max.

3. The calibration factor (V/m) is then calculated from the transmitted power andthe recorded maximum field as

Calibrationfactor =Er,max√

Pt=

8π

λ

√5Pr,maxPt

. (3.54)

4. This should be repeated for frequency steps of maximum 2% of the precedingfrequency until 1.1 times the start frequency is reached. After that, the stepsshould be a maximum of 10% of the preceding frequency.

• Electric field probe procedure

1. An appropriate unmodulated input power (Pt) should be transmitted into thechamber at the start frequency.

2. The stirrers should be rotated one revolution with a minimum number of stepsgiven in Table A.5. The stirrer should dwell at each step longer than 1.5 times theresponse time for the measurement receiver. At each step should each element ofthe probe be measured and the highest recorded field strength should be savedEx,y,z,max.

3. The calibration factor (V/m) is then calculated from the transmitted power andthe recorded maximum field as

Calibrationfactor =

√√√√(Ex,max+Ey,max+Ez,max

3

)2Pt

. (3.55)

4. This should be repeated for frequency steps of maximum 2% of the precedingfrequency until 1.1 times the start frequency is reached. After that, the stepsshould be a maximum of 10% of the preceding frequency.

3.8.2.3 EUT testing

The same antennas as used during the calibration should be used during EUT testing.

1. Measurement equipment should be turned on and allowed to stabilize.

2. The RF source should use a 1 kHz pulse modulation with a 50% duty cycle and beset to the start frequency.

3. Calculate the amount of RF power (Pt) needed to create the desired field strength (Er)by using the calibration factor from the calibration. Interpolation between calibrationpoints is required.

Pt =

(Er

Calibrationfactor

)2

(3.56)

It should be verified that the desired field is present

4. The stirrers should be rotated one revolution with a minimum number of steps givenin Table A.5. The stirrer should dwell at each step by the time specified in Table A.4.As the stirrers rotate, the transmitted power should be maintained to produce thedesired field levels.


5. The required frequency range should be swept as specified in 4 for each frequency.Monitor the EUT performance for susceptibility effects.

6. If susceptibility is noted, the threshold level should be determined by the procedurein section 3.8.2.4 to verify that it is above the limit.

3.8.2.4 Thresholds of susceptibility

If susceptibility is noted, the threshold level should be determined. This level is when thesusceptible condition is no longer present. The threshold is determined by the followingprocedure,

1. If a susceptibility condition is noted then the transmitted power should be reduceduntil the EUT recovers.

2. The transmitted power should then be reduced another 6 dB.

3. Increase the transmitted power until the susceptibility condition is noted again. Thatlevel is then the threshold of susceptibility.

4. Record threshold power level, frequency range swept, frequency and level of greatestsusceptibility and other test parameters.

3.8.2.5 Chamber time constant

The chamber time constant is a constant determining how long time it takes to build up afield in the chamber. This is important when using pulsed waveform testing. If the timeconstant is too large relative to the pulse, then it can be difficult to reach the desired fieldstrength. In order to assure that the chamber is fast enough the following procedure couldbe used.

1. Calculate the chamber Q using

Q =

(16π2V

ηTxηRxλ3

)(PaveragePinjected

)(3.57)

where ηTx and ηRx are the antenna efficiency factors for the transmit and receiveantennas, respectively, and can be assumed to be 0.75 for a log periodic antenna and0.9 for a horn antenna, V is the chamber volume (m3), λ is the free space wavelength(m) at the specific frequency, Paverage is the average received power over one tunerrotation, and Pforward is the forward power input to the chamber over the tunerrotation at which Paverage was measured.

2. By using the Q-factor in equation 3.57 is the time constant, τ is calculated as

τ =Q

2πf. (3.58)

3. The chamber constant is not allowed to be greater than 0.4 of the pulse width. In caseof greater value is it necessary to add absorber material into the chamber or increasethe pulse width.

3.9. Agilent VEE 27

3.9 Agilent VEE

3.9.1 Developer

Agilent VEE is a development environment created by Agilent Technologies based on avisual and data flow programming language. VEE is the short form for what was originallycalled Visual Engineering Environment, but now days it is officially named just ”VEE”.

3.9.2 Visual programming language (VPL)

The main feature of a visual programming language is that programs are created by ma-nipulating program elements graphically rather than specifying them textually. A VPLutilizes programming with visual expressions and spatial arrangements of text-graphic sym-bols, representing elements of syntax or secondary notation. Within the frame of the visualprogramming environment the user is able to structure the iconic elements according tosome specific structure for program construction. Interpretation of element structure thendefines the data distribution of the program. Commonly boxes or other objects represententities with the connecting relations represented by arrows, lines or arcs.

Visual expressions for naturally visual languages are inherent with no textual equivalence,where as a non-visual language having a superimposed visual representation is called visu-ally transformed.

Classification of the programming language can be broken down further, according to thetype and extent of visual expression used, into icon-based languages, form-based languagesand diagram languages.

The principles of visual programming under chapter 3.9.2 is more extensively explainedat the internet reference [21].

3.9.3 Dataflow programming

The majority of programming languages are imperative, meaning that the program is ex-ecuted as a sequence of instructions and the system is constantly in a certain ”state”. Astate can be seen as the measure of various conditions in the system and execution of eachinstruction can modify it.

The lack of visualization of the states in imperative programming is a problem as the infor-mation needs to be shared across multiple processors in parallel processing machines.

Data flow programming implements data flow principles and architecture between oper-ations and were introduced to simplify parallel programming and to structure languagesbetter suitable for numeric processing.

The logical execution flow of data is represented by nodes on a block diagram that areconnected to one another. These nodes can be reconnected in any way to or from differentapplications without the need for internal change. The execution order of utilities on theblock diagram depends on the movement of data through the nodes which changes emphasisfrom sequences of instructions to conversions performed on streams of data.


Operations run when all inputs are valid and will be ”ready” at the same time withouttracking of hidden states, so the language is logically parallel. The asynchronous processmakes the time for events hard to predict, but as it turns out this isn’t necessary.

As data flow programming is highly visual and resembles more a real life processes, and itis often used in hard real time problems. It can be pictured as a factory, where items travelfrom station to station, undergoing various changes. Still it can be hard to work with flowbased programming without having an instantaneous map of the project.

The principles of dataflow programming under chapter 3.9.3 is more extensively explainedin the document by Paul J. Morrison [22].

3.9.4 Dataflow functionality in VEE

Programs in Agilent VEE are built by connecting objects that represent different datasources. The data flows sequentially into an object from the left, gets treated and then theresulting data flows out of the right side terminal. The sequence of execution is of the formleft to right, top to bottom and objects will execute when all input terminals have receivednew data.

The ability to control the sequence of execution is possible because the objects have asequence input terminal on the top and a sequence exit terminal at the bottom. By wiringthe input sequence terminal on a specific object the user can “hold off” execution as it willnot execute until the object with the corresponding wire connected to its sequence outputterminal is executed. In this case despite having data on all data inputs the object will waitfor the sequence input terminal to be pinged. When data leaves the data output terminalsthe object actively monitors the downstream objects, and not until they have all been exe-cuted it will execute its own sequence output (bottom) terminal. A typical object structurein VEE can be seen in Figure 3.2.

3.9.5 Integrated Matlab Engine

VEE has an integrated MATLAB R© (MathWorks R©) engine with built in functions includinganalysis and visualization functions from the MathWorks Signal Processing Toolbox [23].With the object based MATLAB Script the user can reach roughly 1800 common MATLABfunctions.

3.9.6 .NET Framework Integration

VEE supports .NET automation and Windows Forms controls which can be run on anyMicrosoft Windows operating system.

The framework is designed to fulfill the following objectives [24]:

• To provide a consistent object-oriented programming environment whether object codeis stored and executed locally, executed locally but Internet-distributed, or executedremotely.

• To provide a code-execution environment that minimizes software deployment andversioning conflicts.

3.9. Agilent VEE 29

Figure 3.2: Typical sequential data flow between objects in VEE.

• To provide a code-execution environment that promotes safe execution of code, in-cluding code created by an unknown or semi-trusted third party.

• To provide a code-execution environment that eliminates the performance problemsof scripted or interpreted environments.

• To make the developer experience consistent across widely varying types of applica-tions, such as Windows-based applications and Web-based applications.

• To build all communication on industry standards to ensure that code based on the.NET Framework can integrate with any other code.

The Common Language Infrastructure (CLI) is an open specification by Microsoft thatdescribes the executable code and runtime environment that form the core of the Microsoft.NET Framework. A visual description of the CLI structure can be seen in Figure 3.3.Two foundations of the Framework are the common language runtime and the .NET Frame-work class library.

3.9.6.1 Common language runtime (CLR)

The CLR generally works as an application virtual machine that manages code at executionproviding services as remote-controlling, memory- and thread management, compilation andsafety verification. Auto immunization of layout, reference handling and releasing objectssolves frequent errors of memory leaks and invalid memory referencing.

Enforcing strict code accuracy verification with a system called common type system (CTS)and exception handling contributes to security and forcefulness. Depending on the parts of


Figure 3.3: Visual description of the CLI structure [25].

a section it is given a degree of trust limiting the ability of operations. Code access securityis also inflicted by the runtime.

Users are able to take full advantage of the runtime, the class library and components fromother languages, and still be programming in their own language. Any compiler vendorintegrating the runtime offers all existing code access to the .NET Framework simplifyingmigration for applications.

Including managed and unmanaged code gives a possibility to make use of COM elementsand DLLs. An attribute called just-in-time enhances performance while executing by run-ning managed code in the native machine language. During this process fragmented mem-ory and memory locality-of-reference is also managed to enhance performance even further.Figure 3.4 illustrates how the common language runtime and the class library relates to anapplication and to the overall system.

Microsoft R© SQL ServerTMand Internet Information Services (IIS) can host the runtime.

3.9.6.2 .NET Framework class library

The class library is an object oriented set of reusable types from which the user can managecode to develop functionality. Third party mechanisms can flawlessly be integrated with

3.9. Agilent VEE 31

Figure 3.4: Relationship of the common language runtime and the class library to an applicationand to the overall system. The illustration also shows how managed code operates within a largerarchitecture [24].

the .NET Framework with a possibility to develop collection classes with a set of interfaces.The class library is versatile with programming features such as string management, datacollection, database connectivity and file access. Development of the subsequent applicationsand services are also possible:

• Console applications.

• Windows GUI applications (Windows Forms).

• Windows Presentation Foundation (WPF) applications.

• ASP.NET applications.

• Web services.

• Windows services.

Programs based on the .NET Framework can be run in software environments that host theprogram’s runtime.

3.9.7 Capabilities

The ability to control a large amount of instrumentation together with high level program-ming constructs in VEE is a strength. For example file I/O is managed with task orientedTo/From objects and memory allocation is controlled by the program.

Other capabilities are [26]:


• Instrument Connectivity via:

◦ VXI plug & play drivers

◦ IVI - COM drives

◦ NI - DAQMX

◦ SCPI via the DirectIO object

• Built-in math and statistics including FFT and windowing functions

• Visual displays such Strip chart, Waveform, Polar & Smith charts

• Wide array of input controls for building operator user interfaces

• ActiveX Automation

• ActiveX Controls

• Socket IO via the To/From Socket object

Chapter 4

Results

The result of the project is a new control system for the reverberation chamber at Combitechand is named RC. The program is designed to be able to fulfill the different requirementsfrom both civil and military standards. The program uses driver files for all communicationwith the stirrers and instruments. This is done to fulfill the need of a program that operatesin a changing environment where instruments often change. The system is created withAgilent VEE 9.0 as the platform, but interfaces are done with the help of .NET Frameworkand some calculations uses the Matlab engine.

The basic flow of the program is divided into three blocks which are drivers, RC and equip-ments, as seen in Figure 4.1

Figure 4.1: Basic flow of the program divided into three blocks which is drivers, RC and equip-ments.

4.1 Drivers

The driver files are written as regular text files which are read by the program. Thesefiles contain everything needed to use the program or to do a test. A driver file is usedby the program to: save and load program parameters, set instruments, communicate withinstruments and stirrers, read help files. There is a different formatting of the text filesdepending on what they are used for.

• Drivers for menu options: Menu options are read into records when starting theprogram. This record collects the different parameters for a menu into one group,for example FrequencySaveOptions.MindB where FrequencySaveOptions is the recordand MindB is the parameter. Every option uses two lines in the driver file, the first isthe parameter and the second is the value for that parameter.

33

34 Chapter 4. Results

• Drivers for instrument communication: The communication driver for the re-spective instrument contains all GPIB commands that the instrument can send. Thefile is divided into groups for different instrument actions. An action to pre-set theRF generator could look like this in the driver file:

[PreSetRfGenerator]∗ RSTDISPLAY:STATE ON:OUTput OFF:POWer ]StrengthOptionsStrengthSaveOptions.MindB][/PreSetRfGenerator]

[text] is the group name for the sequence of commands needed to pre-set the RFgenerator. This is the start line for the action when the program reads the driver file.If a text is surrounded by ]text] it is read by the program as a global variable. If thetext between ]] contains a dot ”.” the variable is interpreted as a record. Every actionneeds to end with the line [/text].

• Drivers for instruments: Instrument drivers contain a list of instruments that theuser can choose between in the program.

• Drivers for strength adjustment: These files contain two columns, the first onecontains x-values[Hz] and the second one is strength[dBm]. The two columns need tobe separated by a tab.

• Drivers for stirrers: Code representing controller routines and controller setupcommands are loaded from text files on to the controller. Among them the setupfiles are static in the way that the code never changes between the times it is loadedto the controller. However, when the user changes stirrer parameters like accelerationand velocity in the program, the code for the stirrer movement must be changed. Thesolution was to use the .NET functionality ”Stream writer” in Agilent VEE to exporttext into text files. As the user saves settings the stirrer parameters are set by globalvariables representing the user specified value as the whole code is streamed out tothe text file. An object in VEE that streams controller program code to a text filewhen being executed can be seen in Figure 4.2.

4.1. Drivers 35

Figure 4.2: Object in VEE that when being executed streams controller program code to a textfile.

The file is then instantly loaded to the controller memory replacing the old program.

The files used are:

◦ OneMaster: This is one of the setup files that are loaded to set up the controllerwith one ”master” in control of both stirrers. This setup is used for all settingsexcept when a time based move in mode tuning is considered.

◦ TwoMaster: This setup file is loaded to the controller to set the controller tohave one ”master” controlling each stirrer. This is only necessary in mode tuningand using time based movement.

◦ Setup: Setup is the file loaded when resetting the controller and resets the basicsetting for the controller.

◦ Prog0: This is the file holding the current program to run settings except whena time based move in mode tuning is considered.

◦ Prog1: This file is loaded to the controller when using time based move in modetuning. We then need two programs using each to control one master and henceone stirrer.

◦ Defines: The file holds the controller internally defined variables.

• Drivers for help files: Except for plain text the help files can have tab items,captions, and headings. For example, when writing the heading in a help file the userstarts the line with the heading text with the command ”heading”. In the same wayfor a tab item or a caption the user writes ”tab” or ”caption” for the respective formaton the following text. When the user presses a help button or enters the ”ProgramContent” menu in the program, help files will be presented to the user in a text boxobject with the correct formatting. Figure 4.3 shows the text of a driver help file.


Figure 4.3: Text file with commands and the corresponding text which is loaded when displayingstirrer help text in the program.

Other formats can easily be added to the program if desired by the user.

4.2 RC software

RC is divided into several menu categories where the user has the ability to save data, loaddata, change parameters or interface appearance and perform tests. The structure of theprogram is complex and hard to show with a flow diagram. A simplified diagram of theprogram structure is shown in Figure 4.4

Figure 4.4: A simplified diagram of the program structure.

4.2. RC software 37

4.2.1 Welcome screen

This menu works as the welcome screen (Figure 4.5). The user has here the possibility totype in the name, choose a standard to follow and a test to do. Choices made in this menuaffect the options available in the program.

Figure 4.5: Welcome screen in RC.

• Standard: This is where the user can chose between the standards MIL and DO-160F.If none is selected, then all functionality in the program is available

• Measurement: This is where the user can choose between the measurements radiatedsusceptibility and radiated emission. If none is selected, then all functionality in theprogram is available

The user can use the ”Quit” button to exit the program. If there are any concerns about theparameters the ”Help” button is supposed to give information regarding this. The ”OK”button takes the user to the main page of the program.

4.2.2 Main window

The architecture of the main window (Figure 4.6) is intended to have a commercial layoutand a logical structure with easy overview of chamber outputs.


Figure 4.6: Main window in RC.

At the top are the different menus with submenus for configuration and communication withthe program. Under the menu is a control bar with buttons giving easy access to importantfeatures. The different plot windows can be hidden and shown through the buttons on thecontrol bar. The control bar at the bottom gives information about chamber outputs whenperforming a sweep.

The ”Main” tab of the control bar is divided into the sections: Stirrers, Frequency, Markersand Actions.

Within the ”Stirrers” section the user receives instantaneous data output regarding stirrermovement during a sweep. There are also three buttons for fast interactions. Within thefrequency section the user receives instantaneous data output regarding frequency steppingand time consumption.

Within the ”Markers” menu there is one button to generate a marker note within thestrength plot window and one button to clear all marker notes generated during the currentsweep. When running a sweep a constant marker can be scrolled along all strength mea-surements in the plot window. When pressing the ”Set Marker” button a dialog windowpops up for the user to enter a message. When the message is entered data from that pointwill be saved together with the message. Visually an ”X” marks the point where the markernote was placed.

Then there is an ”Action” section with buttons enabling the user to stop, break or continuea sweep. For example, the user can stop a sweep and save it as well as load a sweep andcontinue it.

There is also an ”Additional” tab on the control bar that is indented to hold outputs and

4.2. RC software 39

interactive features of less importance. Right now buttons enable stepping with the markerin the strength plot window, but if expanding the program leaves possibilities to implementmore options.

In the bottom of the main window is status strip giving information about time and date,user, standard, type of measurement and data at the current marker position.

Figure 4.7: Setting a marker and making comments regarding q specific measurement value.

4.2.3 File

The file menu holds general functionality controls for the program. The user can start anew, or open and old project, and save projects. Other submenus like devices, sweep eventsand start sweeps are also found here.

Figure 4.8: The file menu and its selectable submenues.


4.2.3.1 New project

The program basically restarts as settings are reset and the welcome menu is displayed.

4.2.3.2 Open

The open function lets the user load projects through a file browser. The executable fileis in the form of a text file. If the project was saved during a sweep the program willautomatically set up equipment and take all necessary actions enabling a continuing sweep.If the load is aborted the user is alerted with a ”Nothing loaded” message.

4.2.3.3 Save

The user can at any time decide to save the current project, even in the middle of a sweep.The user is asked where to save the project and the name of the project run file. If the folderdoesn’t exist the program will also ask if that folder is to be created. In the designated foldertogether with the project file the program will make a folder containing text files holding allinformation about program setup and data at the time the project was saved. If the save isaborted the user is alerted with a ”Nothing saved” message.

4.2.3.4 Devices

In the devices menu there are options for the different instruments shown. The user herehas the ability to change parameters that specify how to communicate with the instrument.The menu is divided into three tabs which are the different types of instrument available tothe user; these are a RF Generator, Spectrum analyzer and a Pre Selector.

4.2.3.4.1 RF Generator

Figure 4.9 shows the RF Generator tab. This is where the user can change the name, GPIBaddress and file address from where the RF generator GPIB commands are read.

4.2. RC software 41

Figure 4.9: RF Generator tab in the device menu is where the RF Generator can be configured.

• Instrument Name: This list specifies the different RF Generators that are availableto the program.

• GPIB Address: Sets the GPIB address which will be used by the program to com-municate with the instrument.

• Instrument driver: Specifies which driver file that will be used by the program.This file contains the GPIB commands for doing actions with the RF generator.

• Text box: The contents of the chosen driver file will be presented in this text box.

If nothing is to be changed, the ”Exit” button can always be used to close the menu. If thereis any concerns about the parameters the ”Help” button is supposed to give informationregarding this. If any parameter is changed the ”Save and exit” button should be used whenexiting the menu.

4.2.3.4.2 Spectrum Analyzer

Figure 4.10 shows the spectrum analyzer tab, where the user can change the name, GPIBaddress and file address from where the Spectrum analyzer GPIB commands are read.


Figure 4.10: The spectrum analyzer tab in the device menu is where the Spectrum analyzer canbe configured.

• Instrument Name: This list specifies the different Spectrum Analyzers that areavailable to the program.


• Instrument driver: Specifies which driver file that will be used by the program.This file contains the GPIB commands for doing actions with the spectrum analyzer.


If nothing is to be changed, the ”Exit” button can always be used to close the menu. If thereis any concerns about the parameters the ”Help” button is supposed to give informationregarding this. If any parameter is changed the ”Save and exit” button should be used whenexiting the menu.

4.2.3.4.3 Pre Selector

Figure 4.11 shows the pre selector tab, where the user can change the name, GPIB addressand file address from where the Pre Selector GPIB commands are read.

4.2. RC software 43

Figure 4.11: The pre Selector tab in the device menu is where the Spectrum analyzer can beconfigured.

• Instrument Name: This list specifies the different Pre Selectors that are availableto the program.


• Instrument driver: Specifies which driver file that will be used by the program.This file contains the GPIB commands for doing actions with the pre selector.


If nothing is to be changed, the ”Exit” button can always be used to close the menu. If thereis any concerns about the parameters the ”Help” button is supposed to give informationregarding this. If any parameter is changed the ”Save Settings” button should be used whenexiting the menu.

4.2.3.5 Sweep events

In the sweep events (Figure 4.12) menu the user can specify events that will happen duringa test. Events can either be a GPIB or a message event. A message event will cause theprogram to pause at the chosen frequency and show a message defined by the user. Theprogram continues as before the pause when pressing OK on the message. A GPIB eventwill cause the program to send a GPIB command to the instrument address, both specifiedby the user. The chosen event will happen before the specified frequency.


Figure 4.12: The sweep events menu is where different events can be specified.

• Frequency column This column contains the different frequencies specified at whichthe event will happen.

• Message/GPIB This column specifies the type of event. This is done by writingeither Message or GPIB in the field.

• Address This column sets the address to the instrument that will receive the GPIBcommand. If ”message” is chosen in the column before then this is irrelevant.

• Message This is where the user can write the message/GPIB command to send eitherto the screen or to the instrument.

The ”Add row” button adds a row to the list and the ”remove row” button removes one row.If nothing is to be changed, the ”Exit” button can always be used to close the menu. If thereis any concerns about the parameters the ”Help” button is supposed to give informationregarding this. If any field in the list is changed the ”Set list” button should be used whenexiting the menu.

4.2.3.6 Center marker

This menu centers the marker in the strength plot.

4.2.3.7 Sweep

Procedures for both mode tuning and mode stirring are available within the program thoughthey should be seen as tests of the functionalities of the system as they do not fulfill standardrequirements yet. The program flow for the mode tuning procedure can be seen in figure4.13.

4.2. RC software 45

Figure 4.13: Program flow for a mode tuning sweep.

First the RF-generator and the spectrum analyzer are preset to initiate measurements ac-cording to user specified settings. The field strength is then tuned with the RF-generatorto match the user specified initial value and the frequency is set to its initial value. Thefrequency is then updated, i.e. increased or decreased. However, the first time the frequencystays constant as the first strength measurement is taken at the initial frequency. As theuser has the possibility to arrange the program to skip frequencies a check is then madeif the frequency should be skipped, if this is the case the program loops back to yet againupdate the frequency.

Another feature implemented is an event handler where the intention is to have a list ofactions that are executed at certain frequencies. This is checked immediately after the fre-quency update. Actions are in the form of changing settings for instruments, pause thesweep and giving messages to the user.

The strength level is then checked to be within preset limits at the current frequency. It ispossible to set up advanced limit conditions within the frequency interval. If not within thelimits the strength is adjusted until within the given limits.

Then the stirrer procedure is started and the program loaded to the controller initiated.First the stirrer(s) are stepped to the first position. As the stirrer(s) come to a halt theprogram dwells for a given time and then reads the current field strength. Then the pro-cedure starts over again until the stirrer(s) have made one full rotation and with strengthmeasurements corresponding to the number of discrete steps of the stirrer(s). Then thehighest strength is saved as it is the only one interesting for further evaluations.


Finally the GUI is updated so that the user can follow the proceedings of the sweep withcomprehensible data.

If the current frequency is not the final frequency initially set by the user the program willloop back to update the frequency and eventually retrieve a maximal strength value for thatfrequency.

Figure 4.14: The main window and the field strength plot during a mode tuning sweep.

4.2. RC software 47

Figure 4.15: The main window and the power output plot during a mode tuning sweep.

The program flow for the stirring procedure can be seen in figure 4.16

Figure 4.16: Program flow for a mode stirring sweep.


This procedure is very similar to the tuning procedure but with some small modifications.When stirring the paddles should be in constant motion and so this is the first thing thatis initiated. All checks and updates then follow the tuning procedure until the strengthmeasurement. The strength is measured just once at each frequency while paddles are inconstant movement. Finally, like in the tuning procedure, the GUI is updated and theprogram loops back to the frequency update state.

Figure 4.17: The main window and the field strength plot during a mode stirring sweep.

4.2. RC software 49

Figure 4.18: The main window and the power output plot during a mode stirring sweep.

4.2.3.8 New Sweep

This submenu resets any earlier sweep by clearing values and vectors needed to start a newsweep.

4.2.3.9 Power On/off

This functionality lets the user control the frequency and the field strength in the chamberby moving the marker. The marker position in x-direction sets the frequency for the RFGenerator and the position in y-direction sets the target level for the field strength in thechamber. The user can at any time set the power off or on. Stirring is the only availableoption for this function. The procedure when starting the ”power on” submenu is that:First the RF-generator and spectrum analyzer are preset to initiate measurements accordingto user specified settings. The field strength is then tuned with the RF-generator to matchthe limits specified by the user, around the initial marker position(y-direction) and thefrequency is set to the initial position of the marker(x-direction).The program will then loop a sequence where it sets the frequency and tunes the fieldstrength dependent of the marker position. This is done until submenu ”Power off” ispressed which ends the RF generator transmission into the chamber.

4.2.3.10 Sweep Frequency list

The sweep frequency list is a functionality which lets the user sweep a specific list of frequen-cies. The list is set in submenu ”frequency list”(See section 4.2.5.2) under ”frequency”. Theprogram flow for this function is almost the same as the program flow for tuning/stirring ina sweep (See figure 4.2.3.7). The only difference is that the dashed box (skip frequency) is


erased. Skip frequency (See 4.2.5.3) is unnecessary when every frequency swept is specifiedby the user.

4.2.3.11 Exit

This menu will exit the RC program.

4.2.4 Stirrer

The stirrer menu (Figure 4.19) consists of five submenus that all have to do with communi-cation or settings for stirrer movement.

Figure 4.19: The stirrers menu and its selectable events and submenus.

4.2.4.1 Options

Under this menu settings for stirrer movement can be set. Figure 4.20 shows the openedmenu in the program software. Values are pre set with regards to the type of standardchosen at start up. When a project is loaded the values under stirrer options will changeaccordingly with the values at when the project was saved. Below follows explanations ofeach parameter:

4.2. RC software 51

Figure 4.20: The stirrers options menu.

• Mode: Selection of run mode of paddles. Eligible modes are tuning or stirring.

• Acc: Acceleration for the paddle(s) during stepping and jogging. Unit is degrees/s2.

• Dwell Time: Time of paddles’ stand still before measurement(s). The unit is seconds.

• Steps/Rev: Number of discrete measurement steps per revolution of paddle(s).

• Revolutions: Number of revolutions per measurement frequency.

• Velocity: Paddle(s) target velocity during stepping and jogging. Unit is degrees/s.

• Dec: Deceleration for the paddle(s) during stepping and jogging. Unit is degrees/s2.

• Step Time: Time for each paddle step when time based move is active. Can onlybe active in tuning mode. Limiting values for velocity and acceleration restrict thepossible input. The unit is seconds.

• Time Based Move: Activate time based move. Can only be set in tuning mode.

• Main Paddle Active: Enable main paddle stepping and jogging.

• Second Paddle Active: Enable second paddle stepping and jogging.

• Percent of Main: If both paddles are enabled, this value represents the reduction inspeed for the second paddle as a percentage.

If nothing is to be changed you can always exit the menu by using the ”Exit” button. Ifthere are any concerns about the parameters the ”Help” button is supposed to give infor-mation regarding this.


If any parameter is changed the ”Save Settings” button should be used when exiting themenu. As this button is pressed the program will flash the controller memory with a newprogram in accordance with the parameter values set. As this is done a progress bar will bedisplayed on the screen indicating the amount of data transferred (Figure 4.21).

Figure 4.21: The main window when flashing program code to the controller.

4.2.4.2 Reset Controller

The basic setup of the controller is specific for the application and can be flashed to thecontroller memory like any other program. This option is implemented with the intentionthat the controller could be used in other applications which hence need a different setup.When switching from another application the user will have to run ”Reset Controller” toreset and set up the controller correctly.

4.2.4.3 Run Setting

This option is implemented with the intention that the user wishes to control the stirrerswith the program developed but take measurements with other software. This is currentlymainly of interest when running mode stirring tests. When ”Run Settings” is executed thecurrent program flashed on to the controller is executed.

4.2.4.4 Connect

Before being able to communicate with the controller, the user will have to actively connectto it. This is mainly because it contributes to a higher stability and a larger program accesswithout controller connection. When the controller is connected a ”Connected” messageis displayed on the screen (Figure 4.22). If any routine demanding the controller to beconnected is executed with a non connected controller, the user should be alerted about thisthrough warning messages.

4.2. RC software 53

Figure 4.22: The main window when successfully connected to the controller.

4.2.4.5 Disconnect

The program is always started with the controller disconnected, though when connectedthe user always has the option of disconnecting the controller. When the controller isdisconnected the user is alerted with a ”Disconnected” message displayed on the screen(Figure 4.23).


Figure 4.23: The main window when successfully disconnected from the controller.

4.2.4.6 Run Setting

This option is implemented with the intention that the user wishes to control the stirrerswith the program developed but take measurements with other software. This is currentlymainly of interest when running mode stirring tests. When ”Run Settings” is executed thecurrent program flashed on to the controller is executed.

4.2.5 Frequency

The frequency menu is divided into six submenus. The first three are where the user canadjust parameters that have effect on the frequencies in the chamber. The last three controlsthe marker(x-direction) in the strength plot. Figure 4.24 shows the frequency menu.

Figure 4.24: The frequency menu and its selectable events and submenus.

4.2.5.1 Options

The frequency options (Figure 4.25) are parameters such as stop and start frequency, stepsize, sweep direction and scale set.

4.2. RC software 55

Figure 4.25: The frequency options menu is where parameters connected to the frequency can bechanged.

• Min Frequency: Sets the minimum frequency for a sweep. This is the start frequencyin normal direction and the stop frequency for inverse direction of a sweep. The unitis [Hz].

• Max Frequency: Sets the Maximum frequency for a sweep. This is the end frequencyin the normal direction and the start frequency for the inverse direction of a sweep.The unit is [Hz].

• Scale Frequency: Scales the frequency axis (x) on the strength plot in either linearor logarithmic[%].

• Step size: Sets the type of frequency step for a sweep. Choose linear for takingthe same length over the whole sweep. The unit is [Hz]. Choose logarithmic fortaking logarithmic steps during the sweep, this means that the next step length is apercentage of the current frequency.

• Inverse Frequency: The default setting is to sweep from min to max frequency. Ifthis box is checked the sweep goes from max to min.

If nothing is to be changed, the ”Exit” button can always be used to close the menu. If thereare any concerns about the parameters the ”Help” button is supposed to give informationregarding this. If any parameter is changed the ”Save and exit” button should be used whenexiting the menu.

4.2.5.2 Frequency List

In the frequency list (Figure 4.26) menu the user has the ability to create a list of specificfrequencies that are desirable to test. These frequencies are swept from the sub menu ”sweepfrequency list” under the ”file” menu.


Figure 4.26: The frequency list menu is where a list of specific frequencies to sweep can be specified.

• List of frequencies: This is where a list of frequencies to sweep can be specified.The unit is [Hz].

”Add row” button adds a row to the list and the ”remove row” button removes one row. Ifnothing is to be changed, the ”Exit” button can always be used to close the menu. If thereare any concerns about the parameters the ”Help” button is supposed to give informationregarding this. If any field in the list is changed the ”Set list” button should be used whenexiting the menu.

4.2.5.3 Skip Frequencies

In skip frequencies (Figure 4.27) menu the user has the ability to specify a list of frequencyintervals that the program will skip during the sweep.

4.2. RC software 57

Figure 4.27: The skip frequencies menu.

• From: This list specifies the start frequencies of the intervals that will be skippedduring a sweep. The unit is [Hz].

• To: This list specifies the end frequencies of the intervals that will be skipped duringa sweep. The unit is [Hz].

”Add row” button adds a row to the list and the ”remove row” button removes one row. Ifnothing is to be changed, the ”Exit” button can always be used to close the menu. If thereare any concerns about the parameters the ”Help” button is supposed to give informationregarding this. If any field in the list is changed the ”Set list” button should be used whenexiting the menu.

4.2.5.4 Go to Value

The go to value menu is for moving the marker to a specific value on the frequency axis (x).Figure 4.28 shows the menu.


Figure 4.28: The frequency go to value menu is used for moving the marker to a specific value onthe x-axis.

• Step up: Moves the marker by one step up with the amount specified in frequencyoptions. See section 4.2.5.1

• Step down: Moves the marker by one step down with the amount specified in fre-quency options. See section 4.2.5.1

4.2.6 Strength

The strength menu (Figure 4.29) is divided into six submenus. The three first is where theuser can adjust parameters that affect the strength in the chamber. The last three controlsthe marker (y-position) in the strength plot window.

Figure 4.29: The strength menu and its selectable submenus.

4.2.6.1 Options

Strength options are divided into two different tabs, strength and power. In the strengthtab, options for controlling the field strength limits and appearance of the strength plot canbe found.

4.2. RC software 59

Figure 4.30: The strength options menu is where parameters connected to the field strength andpower can be changed.

• Min Strength: This is the minimum strength that is shown in the strength plot.

• Max Strength: This is the maximum strength that is shown in the strength plot.

• Tolerance max: Max tolerance level by which the electric field strength can exceedthe target value. The target vector is set in menu 4.2.6.2.

• Tolerance min: Minimum tolerance level by which the electric field strength can bebelow the target value. The target vector is set under menu 4.2.6.2.

• Strength scale: Scales the Strength axis (y) in the strength plot as, either linear orlogarithmic.

• Step size: Type of step to take when power is on. Linear is chosen for taking a specificstep length each step. Logarithmic is chosen for taking logarithmic steps during thesweep. This means that the next step length is a percentage of the current strength.The unit is [dBm].

In the power tab, options for controlling the input power to the chamber from the RFgenerator are found. Figure 4.31 shows the power option tab.


Figure 4.31: The power options menu and the strength tab.

• Min power: This sets the minimum power for the RF Generator. It is also the initialpower from which the Generator starts when starting a sweep. The unit is [dBm].

• Max power: This sets the maximum power that the RF Generator is allowed to give.The unit is [dBm].

• Max Step: This is the maximum step that the RF generator is allowed to take. Theunit is [dBm].

• Step size: This is the step size for the RF generator when adjustment of the strengthis done. The unit is [dBm].

If nothing is to be changed, the ”Exit” button can always be used to close the menu. Ifthere is any concern about the parameters the ”Help” button is supposed to give informationregarding this. If any parameter is changed the ”Save and exit” button should be used whenexiting the menu.

4.2.6.2 Target

In the target menu (Figure 4.32)the user has the ability to create a target vector that theprogram will aim for during a test. How close to the target line the strength needs to be isset in strength options (Section 4.2.6.1) by the min/max tolerance level. The target vectoris created through points that are specified in this menu and then interpolated to a vector.

4.2. RC software 61

Figure 4.32: The strength target vector menu.

• Frequency: List of points on the frequency axis. The unit is [Hz].

• Strength: List of points on the strength axis. The unit is [dBm].

The ”Add row” button adds a row to the list and the ”remove row” button removes onerow. If nothing is to be changed, the ”Exit” button can always be used to close the menu. Ifthere is any concern about the parameters the ”Help” button is supposed to give informationregarding this. If any field in the list is changed the ”Set list” button should be used whenexiting the menu.

4.2.6.3 Adjust strength

It is necessary to adjust the strength measured by the antenna from voltage to field strengthby using the antenna factor. Other adjustments necessary could be losses in the antenna,cables and other losses. This menu lets the user choose up to four files which contain valuesto adjust the field strength. Figure 4.33 shows the adjustment menu.


Figure 4.33: The adjust strength options menu is where the user can add files to adjust the fieldstrength.

Every file has two columns which contain frequency(x) and strength(y) values. The loadedvalues are plotted in the adjustment plot (Figure 4.34). Regression between the points isthen done during the sweep to find out what value to add to the measured strength.

Figure 4.34: The main window with the adjust strength plot shown.

4.2. RC software 63

• Antenna factor: A correction needed is to convert the measured voltage to voltageper meter. This is done by adding a file with antenna factor adjustment values. SeeChapter 3.5 for antenna factor theory.

• Cable loss: Transmitting the power received by the antenna to the measure deviceis done through cables where the signal loses strength. This is adjusted by adding afile with cable adjustment values.

• Antenna loss: The antenna usually has internal losses. This is adjusted by adding afile with antenna adjustment values.

• Other: ”Other” can be used for adding other adjustments values if necessary.

4.2.6.4 Go to value

The go to value menu is used for moving the marker to a specific value on the strength axis(y). The menu is shown in 4.35

Figure 4.35: The strength go to value menu is used for moving the marker to a specific value onthe y-axis.

4.2.6.5 Step up

Moves the marker by one step up with the amount specified in strength options (Section4.2.6.1).

4.2.6.6 Step down

Moves the marker by one step down with the amount specified in strength options (Section4.2.6.1).


4.2.7 Calibration

Under this menu the user can choose to open specific PDF documents within the program.The idea is to have documents with simplified procedures for conducting calibrations andmeasurements according to the different standards. These could then be used as guide lineswhen using the system.

Figure 4.36: Calibration menu with information from previously conducted calibrations and stip-ulated procedures for current standards.

4.2.7.1 DO160-F/MIL/IEC

The documents are revised versions of the standards that could be used as guidance whencalibrating the chamber or running tests.

4.2.8 Plot

The menu (Figure 4.37) consists of four submenus enabling export of sweep data, settingsfor saving and plotting and closing of all plot windows.

Figure 4.37: The plot menu and its selectable events and submenus.

4.2.8.1 Export data

Under ”Export Data” the user has the possibility to export measurement data to either atext or Excel document. When exporting data to an Excel file the program automaticallystarts, sets up columns with measurement data and generates a plot. This makes it easy toswitch between quantities in the plot window and compare results.

4.2.8.2 Settings

Under the ”settings” menu are three tabs with settings for saving measurement data. Un-der the one called ”Markers” the user can choose the directory and file name for markerinformation gathered during chamber runs. Stored data are field strength, frequency andcomments for each marker set in the plot window. Filename and directory can also bechosen for the text file under the second tab. Under the third tab the user can choose thetitle and label for the plot that is generated when exporting data to Excel.

4.2. RC software 65

4.2.8.3 Close All

The menu option ”close all” closes all open plot windows. There is also a fast button forthis on the tool bar next to the plot buttons.

4.2.9 View

The view menu (Figure 4.38) gives the possibility of hiding or showing tool bar and menustrip.

Figure 4.38: Menu enabeling hide/show option for tool bar and status strip.

4.2.9.1 Toolbar

The user can choose whether to hide or show the tool bar.

4.2.9.2 Status Bar

The user can choose whether to hide or show the status bar.

4.2.10 Help

The menu (Figure 4.39) gathers help files and information around the program and itscontent.

Figure 4.39: The help menu and its selectable submenus.

4.2.10.1 Program content

Here .NET can really show its potential in the form of a search application for the helpfiles. The help files are written in external text files which at start up are loaded into theprogram. Under the menu ”Program Content” there is a text box gathering all the helpfiles together in one scrollable textbox. To the left there is a list with the topics of all thehelp files. By selecting the topic in the list and pressing the ”Show” button, the text boxautomatically scrolls down to the specific help file topic. The same thing can also be doneby just double clicking the topic in the topic list.

If the user is looking for a specific word or sentence the search field can be used. If theuser, for example, makes a search for a sentence and it is found, the textbox automaticallyscrolls down to the line where that sentence was first found. At the same time, if any of the


words in the sentence are found within the text, they are marked with the color blue. If thesentence is found on another line the user can just press the search button again and thetextbox will scroll down to the next line. When there is nothing more to be found in thetext the user will be alerted with a ”Search Ended” message and the textbox will scroll upto the top. If the user wishes to clear the search field and reset the text box, the ”Clear”button can be used. The application can be seen in Figure 4.40.

Figure 4.40: Help menu to view and search through help files.

4.2.11 Equipment

4.2.11.1 Instrument communication

The following instruments are used during the project:

• RF generator - HP E8257D:

• spectrum analyzer - HP 8566B:

• Pre selector - HP 85685A:

All communication with the instruments was carried out with GPIB commands. GPIBstands for general purpose interface bus and is designed to connect computers with instru-ments, which is supported in VEE 9.0. Sending GPIB commands to an instrument throughVEE is done by using an object given in VEE to send instrument commands. Figure 4.41shows the instrument communication object.

4.2. RC software 67

Figure 4.41: Instrument communication object i VEE.

By using this object it is only the address and the actual command that needs to be set.RC is using the same object for all instrument communication by dynamically changingthe address to the wanted instrument before sending the command. Figure 4.42 shows theinstrument communication flow.

Figure 4.42: Instrument communication flow in RC.

4.2.11.2 Stirrers communication

The control system running the stirrers (excluding the actual paddles) consists of an ACR9000Motion Controller communicating with a Packaged Microstepping System, both manufac-tured by the company Parker Hannifin. The control function is through high-level commandsdistributed from the host controller, in our case a desktop computer, to the motion con-troller. The motion controller in a multi-axis system may then control several drives andmotors. The Packaged Microstepping System consists of a stepper drive together with theactual motor. Generally, the task of the drive is to supply electrical power to the respectivemotor after interpretation of low-level signals from the controller.

• ACR9000 Motion Controller

The ACR9000 is a compact motion controller for controlling servo and stepper drives.The indexer/controller determines the motor actions like speed, distance, direction,and acceleration rate. It is designed to enable direct panel-mounting and supplyingmultiple connection options.

Main features of the controller are:

◦ Up to 8 axes of servo or stepper control

◦ Advanced Multi-tasking of up to 24 simultaneous programs


◦ interpolation of 8 axes in any combination

◦ 10/100 Base-T Ethernet

◦ USB 2.0

◦ Ethernet/IP compatibility

◦ Absolute Encoder support via SSI

◦ ACR-View Software Development Kit

◦ 24 VDC optically isolated onboard inputs and outputs

◦ CANopen expansion I/O

◦ 120/240 VAC power input

◦ CE (EMC & LVD), UL, cUL approval

• S, SX & SXF Series Packaged Microstepping System

The packaged standalone drive/indexer system can perform registration moves as wellas complex move profiling.

Main features of the system are:

◦ Torques from 65 to 1,900 oz-in

◦ Speeds to 50 rps (3,000 rpm) continuous

◦ 16 user selectable motor resolutions to 50,800 steps/rev

◦ Three-state current control for reduced motor heating

◦ User-selectable current waveform for smooth operation

◦ Zero phase input resets phase currents to the power up positions

◦ Fault output for remote signaling and diagnostics

◦ Optically isolated step and direction, shutdown and zero phase inputs

◦ Anti-resonance eliminates mid-range instability

4.2.12 Software to Controller communication

As stated above there is a versatility of server connections for the controller. For this ap-plication we have used Ethernet to communicate with the ACR9000. A .NET wrapper (bythe controller manufacturer denoted ”Motion COMponents”) is then used to synchronizethe programming software and controller to gain access to a DLL (ComACRsrvr.dll) file.

A wrapper is a subroutine that translates a library’s existing interface into a compatibleinterface which ultimately enables cross language communication with the DLL file. A DLL(Dynamic linked library) file is a Microsoft ”shared library” file which in this case holds sub-routines for communication with the controller. A restriction for the application software isfor it to be compatible with Microsoft protocol OLE (Object Linking and Embedding) andCOM (Component Object Model) interface standard.

The concept of interaction between the programming software and the control system isillustrated in figure 4.43

4.2. RC software 69

Figure 4.43: Diagram showing the interaction between application and controller.

In communication with the controller, specific actions can be initiated both through func-tion calls and through direct communication with the controller terminal.

As the controller holds a flash memory it can store code segments and programs which thencan be actively executed. There are routines which enables uploading of code from a textfile to the controller memory. The internal programming language for the controller is called”AcroBASIC” and consists of simple ASCII mnemonic commands to interact with controllerparameters and bits.

Chapter 5

Conclusions

Looking back at the major parts of the goals there was definitely a satisfactory outcomeregarding the instrument and stirrer communication, as well the look and functionality ofthe user interface. The achievement of implementing two out of three standards in the pro-gram can be discussed, as the program cannot execute a real measurement yet, but fulfillsa lot of criteria to do it. Not being in the position to be able to use the program for a realmeasurement at the end of the project was obviously unsatisfying.

The instrument communication works as planned. It fulfills the demand of a flexible solu-tion where instruments often change. It uses driver text files for the GPIB commands wheresequences of commands can be specified. This lets the user prepare driver files for differentinstruments and just change the driver file within the program. The RF generator driver filehas been extended to include limitations for certain instrument parameters, which needs tobe included for other instrument driver files. During the project three types of instrumentshave been implemented and tested. The standards require use of more instruments whichshould be easy to implement into the program with the use of current functions.

The system in its current form flashes a program into the controller memory which is thenexecuted when initiating a frequency sweep. The execution of the program located on thecontroller is controlled by direct communication with the controller terminal. In the sameway as there are function commands for loading programs from text files into the controllermemory there are several other usable functions and terminal commands for extracting dataand direct stirrer movement. Hence it should be possible to control all movement of thestirrers with function calls and direct terminal commands and to have the whole programsequence within Agilent VEE. However, during program development this generated unex-pected errors to the extent that it became excluded.

The interfaces tested with the controller are USB and Ethernet. To be able to access acontrol function one has to connect to a class defining that control. To communicate withthe controller terminal one has to connect to it as well. A difference between USB andEthernet is that with Ethernet the program can stay connected to all classes and the ter-minal simultaneously when communicating with the controller. Using USB the programcan only stay connected to one class or the terminal at any time. This forces the programto connect and disconnect, respectively, before and after the controller command. As seenduring the program development, running a series of commands rapidly with USB connec-

71

72 Chapter 5. Conclusions

tion tends to generate unexpected errors, probably because of communication delays. Thisis mainly the reason why the code for the program is only compatible with Ethernet inits current form. Hence, to be able to use a USB connection, connect and disconnect com-munication must be added to the program at the cost of stability and maybe program speed.

One of the settings for the stirrers is the number of steps per revolution. Choosing foursteps per revolution will result in four steps taken each being 90 deg. The user can alsochoose the number of revolutions to run per frequency which literary multiplies the num-ber of steps with the revolution number. The reverberation chamber at Combitech AB isequipped with two stirrers. If tuning is run and both stirrers are active the stirrers willtake turn in stepping. This means that when choosing four steps per revolution with twostirrers the stirrers will step only half of a physical revolution per revolution set in the pro-gram software. Hence getting one full rotation for both stirrers per frequency would in thiscase require the user to choose two revolutions. Taking odd steps per one revolution andfrequency with two stirrers will result in the starting stirrer taking the first and last step ateach frequency. To alter the starting paddle for every frequency would consequently requirethe code to be changed from its current appearance.

5.1 Discussion

Time planning has definitely been an issue during the project as we were very optimisticabout how much to be able to accomplish within the 20 weeks. Projects during earlierstudies always have a solution and when running into trouble there are always answers andexplanations within short reach. In a real working environment you are far more indepen-dent and this is a lesson that has been very valuable and something that will be consideredwhen planning projects in the future. There are a lot of unforeseen events that can occurduring a project, for instance, delivery time for new components is one example that hap-pened during this project.

Considering the goals maybe they should early have been broken down into more par-tial goals which would have made the work feel more rewarding when reaching them. Thiscould also have led to a better overview of project requirements and the time consumptionneeded for implementation.

There was not an extensive knowledge around Agilent VEE and its program flow at thebeginning of the project. As we have large experience on Matlab and it is partially inte-grated within VEE we believed it to be very usable, but we soon discovered that Matlabis not that compatible with VEE and could not be used as planned. Instead it was the.NET Framework integration that became really useful. As the project was coming to anend we could see that more or less the whole program is .NET except for the equipmentconnections. Considering this it maybe would have been better to use some other program-ming environment better suited for .NET programming and not using VEE at all. AgilentVEE is probably not designed to be used for project this extensive. Its strength is in thesimplicity of quickly setting up connections with instruments and to extract data throughActiveX objects and thread programming. An indication for this is the fact that there isnot a lot of documentation, code or previous work to be found online. The reason for thismay also partially be that it is hard to document the code in a reasonable way.

5.2. Future Work 73

5.2 Future Work

There is no doubt that the current system, including program software, has the capacityand ability to be expanded to fulfill measurements stipulated in the EMC standards in ques-tion. Getting there still demands the program to update the handling of sequential dataflow within Agilent VEE in an effective way. With sequential execution the problem comesof running parallel events and VEE:s answer to this is to divide code into different threadobjects. Though handling threads and parallel events was definitely not as simple as firstexpected, resulting in a lot of unexpected errors and communication problems. When run-ning threads you can’t have code within the thread that is too dependent on code outside, asit should run independently of other parts of the program. This adds a lot of complexity tothe programming and, as the documentation is limited, a good solution to handle this issuewas never really found. The way of handling communication with thread objects has beenthrough global objects but there are still questions as to how independent the thread objectsneed to be. Trying to use the Matlab engine within thread objects only led to unexpectederrors.

Before the program software can be considered ready for live measurements, extensive er-ror test should be done to secure that there are no bugs or loose threads. This is crucial,as measurement and testing equipment can be very sensitive and valuable, and the fieldstrength within the chamber can reach dangerously high levels. As the program software isconnected with the amplifier stage and the corresponding sending antenna, caution shouldalso be taken as theoretical assumptions have been made to calibrate the software to theamplifier. Logical updates to the program code, enhancing the speed of finding the desiredfield strength with the amplifier, can be made. Future live measurements with subsequentupdates and adjustments are also important.

The user-interface for the program is well-developed though there is always room and abil-ities for updates. The current program layout lets the user choose standard and type ofmeasurement at start up. The intention was to have the program automatically adjustsettings that are crucial to the standard chosen. However, setting the values has not beenimplemented yet because of lacking time. As Agilent VEE lets the constructed programbe run as an executable the thought was to link to all drivers and files in reference of theexecutable file. This would mean that the program could be installed with one install fileon any computer having the runtime version. Some work is still needed, mainly in changingand generalizing links within the program code.

74 Chapter 5. Conclusions

References

[1] M. Backstrom; O. Lunden; P.-S. Kildal. Reverberation Chambers for EMC Susceptibilityand Emission Analyses. Wiley-Interscience, John Wiley & Sons, Inc, New York, 2002.Review of Radio Science 1999-2002, Chapter 19.

[2] Paul R. Clayton. Introduction to Electromagnetic Compatibility. John Wiley & Sons,Inc, 1992.

[3] Staffan Johansson; Per Carlsson. Modern elektronisk matteknik. Liber AB, first edition,1997.

[4] ZTEC Instruments Inc. Waveform generator fundamentals. Internet, 2009. http:

//www.ztecinstruments.com/waveform-generator-fundamentals.

[5] Tom Harris. How amplifiers work. Internet, 2008. http://www.howstuffworks.com/

amplifier.htm.

[6] Zhong Chen. Emc antenna fundamentals. Internet, 2007. http://www.conformity.

com/artman/publish/printer_49.shtml.

[7] Robert E. Collin. Foundations for microwave engineering. McGraw-Hill, Inc, 1966.

[8] Carl Nordling; Jonny Osterman. Physics Handbook for Science and Engineering. Stu-dentlitteratur, Lund, seventh edition edition, 2004.

[9] M. Backstrom; J. Loren; G. Eriksson; H-J Asander. Microwave Coupling into a GenericObject. Properties of Measured angular Receiving Pattern and its Significance for Test-ing. in Proceedings of the 2001 IEEE International Symposium on ElectromagneticCompatibility, Montreal, Canada, .

[10] Richard L. Scheaffer; James T. McClave. Probability and Statistics for Engineers.Wadsworth Publishing Company, fourth edition, 1995.

[11] Seemant Teotia. Saddlepoint approximation for calculating performance of spectrum-sliced wdm systems. Master’s thesis, Virginia Polytechnic Institute and State Univer-sity, Blacksburg, Virginia, July 1999. Appendix B:93-94.

[12] Harima Katsushige; Sugiyama Tsutomu; Yamanaka Yukio; Shinozuka Takashi. Totalradiated power of radio transmitters measured in a reverberation chamber. Journal ofthe National Institute of Information and Communications Technology, Vol.53 No.1:71–73, 2006.

[13] Gilbert M. Masters. Renewable and efficient electric power systems. Wiley-Interscience,John Wiley & Sons, Inc, New Jersey, 2004.

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[14] John D. Kraus. Antennas. McGraw-Hill, Inc, second edition, 1988.

[15] O. Lunden; M. Backstrom. Pulsed Power 3 GHz feasibility study for a 36,7 m3 ModeStirred Reverberation Chamber. IEEE International Symposium on EMC, Hawaii, USA,July 8-13 2007.

[16] Prasad V. Kodali. Engineering Electromagnetic Compatibility : principles, measure-ments, technologies, and computer models. Institute of Electrical and Electronics En-gineers, Inc, 2001.

[17] RTCA, Inc. RTCA/DO-160F : Environmental Conditions and Test Procedures forAirborne Equipment, December 6 2007. Section 20, Radio Frequency Susceptebility(Radiated and Conducted).

[18] RTCA, Inc. RTCA/DO-160F : Environmental Conditions and Test Procedures for Air-borne Equipment, December 6 2007. Section 21, Emission of Radio Frequency Energy.

[19] Michel V. Ianoz; Torbjorn Karlsson; Frederick M. Tesche. EMC Analasis Methods andComputational Models. John Wiley & Sons, Inc, 1997.

[20] Department of Defence, United States of America. MIL-STD-461-F : Interference Stan-dard, December 10 2007. Requirements for the control of electromagnetic interferencecharacteristics of subsystems and equipment.

[21] dmoz open directory project. Visual programming launguages. Internet, 2009. http:

//www.dmoz.org/Computers/Programming/Languages/Visual/.

[22] Paul J. Morrison. Flow-based programming. Internet, 2009. http://www.

jpaulmorrison.com/fbp/index.shtml.

[23] Inc Agilent Technologies. Information and data on agilent vee. PDF, September 1,2008. http://cp.literature.agilent.com/litweb/pdf/5989-9641EN.pdf.

[24] Microsoft Corporation. .net framework conceptual overview. Internet, 2009. http:

//msdn.microsoft.com/sv-se/library/zw4w595w(en-us).aspx.

[25] Chancey Mathews. Common language infrastructure. Internet, June 62007. http://en.wikipedia.org/wiki/File:Overview_of_the_Common_Language_

Infrastructure.png.

[26] Inc Agilent Technologies. Information and data on agilent vee. PDF, October 1, 2008.http://cp.literature.agilent.com/litweb/pdf/5989-9833EN.pdf.

Appendix A

Tables

Frequency Range Number of required log spaced frequenciesfs to 4fs 50 per decade4fs to 8fs 50 per decadeAbove 4fs 20 per decade

Table A.1: Reverberation test criterion [17].

Tuner Steps R9 1.95710 212 2.0818 2.2520 2.324 2.3830 2.4736 2.5440 2.5945 2.6460 2.7690 2.92120 3.04180 3.2

Table A.2: Maximum to average ratio of squared magnitude of E-field [17].

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78 Chapter A. Tables

Frequency Band 6dB Band-width(BW)

Minimumsweep timefor fre-quency band(seconds)

Minimum mea-surments time foranalog measure-ment receivers

0.150 - 30 MHz 1KHz N/A 0.015 sec/KHz30 - 100 MHz 10KHz N/A 1.5 sec/MHz100 - 400 MHz 10KHz 9 1.5 sec/MHz0.4 - 1 GHz 100KHz 1 0.15 sec/MHz1 - 6 GHz 1MHz 1 15 sec/GHz

Table A.3: Susceptibility scanning [18].

Frequency Range Analog Scans Maximum Scan Rates Stepped Scans Maximum Step Size30 Hz - 1 MHz 0.0333 f0/sec 0.05 f0

1 MHz - 30 MHz 0.0667 f0/sec 0.01 f030 MHz - 1 GHz 0.00333 f0/sec 0.005 f01 GHz - 40 GHz 0.00167 f0/sec 0.0025 f0

Table A.4: Susceptibility scanning [20].

Frequency Range (MHz) Tuner Positions200-300 50300-400 20400-600 16

above 600 12

Table A.5: Required number of tuner positions for a reverberation chamber [20].

79

Figure A.1: Radiated susceptibility test levels versus category [17].

80 Chapter A. Tables

Appendix B

Figures

Figure B.1: Suitable probe location for chamber calibration [17].

Figure B.2: Standard deviation curve for field uniformity confirmation [17].

81

82 Chapter B. Figures

Figure B.3: Maximum Level of Radiated RF Interference - Category B and L [18].

Figure B.4: Maximum Level of Radiated RF Interference - Category M [18].

Figure B.5: Maximum Level of Radiated RF Interference - Category H [18].

83

Figure B.6: Maximum Level of Radiated RF Interference - Category P [18].

84 Chapter B. Figures

Appendix C

Work Distribution

C.1 Theory

General theory has been divided in the sense that each of us has taken responsibility ofgathering the necessary information and writing about his part. However getting an overalltheoretical understanding is important and there has been a lot of discussion and collabo-ration in order to understand major concepts of the theory. Erik has been responsible fortheory around basic concepts of EMC, chamber statistics, stirrers and programming lan-guage and software. Jonny has been responsible for theory regarding basic concepts of areverberation chamber, instruments used and theory around antenna measurements. Thefirst intention was to study one standard each. While working through the standards itbecame clear that the standard DO-160F was more extensive than anticipated and harderto interpret. This resulted in Erik taking care of the radiated susceptibility part of theDO-160F standard and Jonny covering the radiated emission part of the same standard.MIL-STD standard was also covered by Jonny as this gave us an even work load and cov-ered theory. More specifically, chapter responsibilities are:

Erik

• Chapter 3.1 - Electromagnetic compatibility

• Chapter 3.2.6 - Stirrer System

• Chapter 3.4 - Field Statistics

• Chapter 3.8.1.1 - Radiated Susceptibility (RS) Test; Alternative Procedure - Rever-beration Chamber

• Chapter 3.9 - Agilent VEE

Jonny

• Chapter 3.2 (except for 3.2.6) - Equipment

• Chapter 3.3 - Reverberation chamber

• Chapter 3.5 - Antenna factor

• Chapter 3.6 - Losses

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86 Chapter C. Work Distribution

• Chapter 3.7 - E-Field in the Chamber

• Chapter 3.8.1.2 - Radiated Emissions (RE) Test; Alternative Procedure - Reverbera-tion Chamber - mode stirring

• Chapter 3.8.2 - MIL-STD-461F Standard

C.2 Results

The main result is a program software built up by functions and other elements that hasbeen built and updated by both students throughout the project. Generally, functions andmenus that regard stirrer communication and movement have been Erik’s responsibility,whereas functions and menus regarding instrument communication have been Jonny’s re-sponsibility. On many levels there are functions and routines that are connecting the twoareas which make it difficult to specifically say who has done what on a programming level.Menus that are directly related to the instruments are ”Strength” and ”Frequency” whichare under Jonny’s responsibility. Menu ”Stirrers” is in the same way directly related to thestirrers and under Erik’s responsibility. The ”Help” menu is also developed mainly by Erik.More specifically, chapter responsibilities are:

Erik

• Chapter 4.2.4 - Stirrer

• Chapter 4.2.10.1 - Help

• Chapter 4.2.11.2 - Stirrer communication

Jonny

• Chapter 4.2.3.4 - Devices

• Chapter 4.2.5 - Frequency

• Chapter 4.2.6 - Strength

• Chapter 4.2.11.1 - Instrument communication

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