Experiment2-NewVectorNetworkAnalyzer Measurement. · 2.3 ReﬂectionandTransmission Reflection...

Experiment 2 - New Vector Network Analyzer

Measurement.

Dr. Haim Matzner & Shimshon Levy.

August, 2008.

CONTENTS

1 Prelab Students Preparation and Report 7

2 Background Theory 92.1 Transmission Line Basic . . . . . . . . . . . . . . . . . . . . . . 92.2 Component Characteristics . . . . . . . . . . . . . . . . . . . . . 92.3 Reflection and Transmission . . . . . . . . . . . . . . . . . . . . 102.4 Network Analyzer System Elements . . . . . . . . . . . . . . . 122.5 Operator Calibration . . . . . . . . . . . . . . . . . . . . . . . . 16

2.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.5.2 Calibration Reference Plane . . . . . . . . . . . . . . . . 182.5.3 When a Calibration Is Necessary . . . . . . . . . . . . . 192.5.4 When a Calibration Is Not Necessary . . . . . . . . . . . 19

2.6 Purpose and Use of Different Calibrations . . . . . . . . . . . . 192.6.1 Normalization or Response . . . . . . . . . . . . . . . . . 192.6.2 Response and Isolation . . . . . . . . . . . . . . . . . . . 192.6.3 Transmission . . . . . . . . . . . . . . . . . . . . . . . . 202.6.4 Reflection . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3 Experiment Procedure 213.1 Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . 213.2 Front Panel View . . . . . . . . . . . . . . . . . . . . . . . . . . 213.3 Entering Frequency Range . . . . . . . . . . . . . . . . . . . . . 233.4 Entering Source Power Level . . . . . . . . . . . . . . . . . . . . 233.5 Scaling the Measurement Trace . . . . . . . . . . . . . . . . . . 243.6 Calibration for Reflection measurements . . . . . . . . . . . . . 243.7 Make a Reflection Simulation and Measurement . . . . . . . . . 25

3.7.1 Reflection Simulation . . . . . . . . . . . . . . . . . . . . 253.7.2 Reflection Measurement of a Coaxial Cable and Terminator 263.7.3 Reflection Measurement of an Elliptic BPF . . . . . . . . 27

3.8 Make a Transmission Simulation and Measurement . . . . . . . 283.8.1 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . 283.8.2 Measurement Procedure . . . . . . . . . . . . . . . . . . 293.8.3 Insertion Loss Measurement of BPF . . . . . . . . . . . 30

3.9 -3 dB Band Width . . . . . . . . . . . . . . . . . . . . . . . . . 303.10 -20 dB and -35 dB Band Width . . . . . . . . . . . . . . . . . . 313.11 Reflection Measurement . . . . . . . . . . . . . . . . . . . . . . 313.12 Final Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

CONTENTS 3

4 CONTENTS

OBJECTIVES

Upon completion of the study, the student will become familiar with the fol-lowing topics:

1. Get acquainted with the major function of the network analyzer.2. Using the Network Analyzer to measure reflection ,Standing Wave Ratio

(SWR) , reflection coefficient, and impedance.3.Using the Network Analyzer to measure transmission, attenuation, gain,

insertion phase.4. Display the device under test parameters (SWR, return loss, reflection

coefficient, impedance) in various formats: linear, log, polar, amplitude-phase,real-imaginary and Smith - chart.

5. Basic knowledge on network analysis measurement and concepts.6. Verification of the calibration of the Network Analyzer.

CONTENTS 5

6 CONTENTS

1. PRELAB STUDENTS PREPARA-

TION AND REPORT

1. Refer to Figure 3 and describe the signal flow when measuring the SWRand the attenuation of the attenuator.

2. Define the following parameters: Reflection Coefficient, S-parameters,Return Loss and SWR.

3. Which measurement the network analyzer perform under Reflection andwhich under Transmission?

PRELAB STUDENTS PREPARATION AND REPORT 7

8 PRELAB STUDENTS PREPARATION AND REPORT

2. BACKGROUND THEORY

2.1 Transmission Line Basic

Electronic circuits which operate at high frequencies present some unique chal-lenges for a proper characterization. At high frequencies the wavelengths ofoperation become similar in dimension to the physical properties of circuit ele-ments. This results in circuit performance that is distributed in nature ratherthan describing the voltage and current at a specific circuit node. It is moreappropriate to describe how waves in a transmission medium respond to a com-ponent in their path. Network analyzers are a class of instruments that havebeen developed to characterize Radio Frequency (RF) components accuratelyand efficiently as a function of frequency. Network analysis is the process ofcreating a data model of the transfer and/or impedance characteristics of alinear network through stimulus-response testing over the frequency range ofinterest. At frequencies above 1 MHz, lumped elements actually become circuitconsisting of the basic elements plus parasitic elements like stray capacitance,lead inductance and unknown absorptive losses. Since parasitic depend on theindividual device and its construction, they are almost hard to predict. Above1 GHz, component geometries are comparable to a signal wavelength, inten-sifying the variance in circuit behavior due to device construction. Networkanalysis is generally limited to the definition of linear networks. Since linearityconstrains networks stimulated by a sine wave to produce a sine-wave output,sine-wave testing is an ideal method for characterizing magnitude and phaseresponse as a function of frequency. This chapter discusses the key parametersused to characterize RF components, the types of network analyzer techniquesused to make measurements and the considerations to be made in obtainingthe most accurate results.

2.2 Component Characteristics

RF (frequencies less than 3 GHz) or microwave (frequencies in the 3 to 30 GHzrange) energy can be likened to a light wave. Incident energy on a DeviceUnder Test (DUT) (for example, a lens) is either reflected from or transmittedthrough the device (see Figure 1). Bymeasuring the amplitude ratios and phasedifferences between the two waves it is possible to characterize the reflection(impedance) and transmission (gain) characteristics of the device.

BACKGROUND THEORY 9

2.3 Reflection and Transmission

Reflection

Insertion Loss

Gain

S21

Transmission

Group delaySWR

S11

Reflection Coefficient

Impedance

Return loss

Reflected wave

Transmission

3dBAttenuator

50Ω

Load

Incidentwave

2 portsdevice

Transmittedwave

Figure 1 - Reflection and Transmission measurement

There are many terms used to describe these characteristics. Some useonly the magnitude information (scalar) and others include both magnitudeand phase information (vector). If an incident wave on a device is described asVINCID, the ratio of VINCID and IINCID is called the transmission system char-acteristic impedance Z0, and a device terminating a transmission system hasan input impedance called a load impedance ZL, then the device characteristicscan be defined by:

Reflection terms:

Γ =VREFLECT

VINCID=ZL − Z0ZL + Z0

−1 < Γ < 1

where Γ = As the device reflection coefficient(complex).VINCID = As the incident wave on a test device.VREFLEC = reflected wave from a test device.Z0 =Transmission medium characteristic impedance.ZL =Load impedance of test device.

ρ = |Γ|

0 < ρ < 1

10 BACKGROUND THEORY

Where ρ = magnitude of reflection coefficient.

Re turn Loss (dB) = −20 log ρ

S ≡ SWR =1 + ρ

1− ρ1 < S <∞

Where SWR = Standing-Wave Ratio of current or voltages on a transmissionmedium. The load impedance is connected to the reflection coefficient by therelation

ZL =1 + Γ

1− ΓZ0

Transmission terms:

Transmission coefficient =VTRANS

VINCID

Insertion loss (dB) = 20 log(| VTRANS |

| VINCID |)

Gain(dB) = 20log(| VTRANS |

| VINCID |)

Insertion phase = ∠VTRANS −∠VINClD

Where < VINCID = vector relative phase angle of incident wave on a DUT.

< VTRANS = vector relative phase angle of transmitted wave through aDUT.

Scattering (S) Parameters

Many component measurements are two-port networks, such as amplifiers, fil-ters, cables and antennas. These component characteristics are typically usedto determine how a particular device would contribute as a part of a more com-plex system. To provide a method that models and analyzes a full two portsdevice in the RF environment, scattering parameters (S parameters) were de-fined (see Figure 2).

REFLECTION AND TRANSMISSION 11

Reflected wave

3dBAttenuator

50Ω

Load

Incidentwave

2 portsdevice

Transmittedwave

a1

b1

b2

a2=0

0Re

2

1

1

11=== a

a

b

Incident

flectedS

01

1

2

21=== a

a

b

Incident

dTransmitteS

Figure 2 - S-parameter measurement of two port element.

This is a characterization technique similar to a lower-frequency Z or Y model-ing, except that it uses incident, transmitted and reflected waves to characterizethe input and output ports of a device as opposed to using voltage and currentterms which are impossible to measure at high frequencies. The S parameterterms are related to other parameters with certain conditions. For instance,S11 is equivalent to a device input reflection coefficient ΓIN under the conditionthe device has a perfect Z0 match on its output. S parameter characterizationof devices plays a key role in the ability of measuring, modeling and designingcomplex systems with multiple components. By definition, S parameters canbe measured with a network analyzer.

2.4 Network Analyzer System Elements

A network analyzer measurement system can be set of four major parts: a sig-nal source providing the incident signal, signal separation devices to separat theincident, reflected and transmitted signals, a receiver to convert the microwavesignals to a lower Intermediate Frequency (IF) signals, a signal processor anda display section to process the IF signals and display detected information, asshown in Figure 3.


R ef

R1

R e fR

2

A B

L O

R F

S ou rc e

R F sw i tc h

S p l it te r S p l it te r

Directio

nal C

ouple

r

Direct

ional C

ouple

r

T e s t

po rt 1

T e s t

po rt 23 d B

A tte n u ator

R ec e iv e rR e c e iv e r

T ran sm itedR e f le c ted

T ran sm ite d R e f le c te d

Figure 3 - The major elements of a Network Analyzer.

The receiver perform the full S parameters which defined as:

S11 =ref lected wave

Incident wave=A

R1

S22 =ref lected backward wave

Incident backward wave=B

R2

S21 =Transmitted wave

Incident wave=B

R1

S12 =Transmitted backward wave

Incident backward wave=A

R2

Signal Source

The signal source (RF or microwave) produces the incident signal used tostimulate the Device Under Test (DUT). The DUT responds by reflecting partof the incident energy and transmitting the remaining part. By sweeping thefrequency of the source the frequency response of the device can be determined.Frequency range, frequency stability, signal purity, output power level andlevel control are factors which may affect the accuracy of a measurement. Thesource used for the network analyzer measurements, is a synthesizer, whichcharacterized by stable amplitude frequency and a high frequency resolution(less than 100 Hz at microwave range).

Signal Separation

The next step in the measurement process is to separate the incident, reflectedand transmitted signals. Once separated, their individual magnitude and/or

NETWORK ANALYZER SYSTEM ELEMENTS 13

phase differences can be measured. This can be accomplished through the useof wideband directional couplers, bridges or power splitters.

A directional coupler is a device that consists of two coupled transmissionlines that are configured to couple energy to an auxiliary port if it goes throughthe main port in one direction and not in the opposite direction. Directionalcouplers usually have relatively low loss in the mainline path and thus presentlittle loss to the incident power. In a directional coupler structure (see Figure 3)the coupled arm samples a signal traveling in one direction only. The coupledsignal is at a reduced level and the relative amount of reduced level is calledthe coupling factor. For instance a -20dB directional coupler means that thecoupled port power level is 20 dB below the input, which is equivalent to 1%of the incident power. The remaining 99% travel through the main arm. Theother key characteristic of a directional coupler is directivity. Directivity isdefined as the difference between a signal detected in the forward directionand a signal detected in the reverse direction (isolation between the forwardand reverse signals). A typical directional coupler will work over several octaveswith 30 dB directivity.

The two-resistor power splitter (see Figure 3) is used to sample either theincident signal or the transmitted signal. The input signal is split equallybetween the two arms, with the output signal (power) from each arm being6dB below the input (power). A primary application of the power splitter isfor producing a measurement with a very good source match. If one side of thesplitter output is taken to a reference detector and the other side goes througha DUT to a transmission detector, a ratio display of transmitted to incident hasthe effect of making the resistor in the power splitter determine the equivalentsource match of the measurement. Power splitters are very broadband, haveexcellent frequency response and present a good match at the DUT input.Separation of the incident and reflected signals can be accomplished usingeither a dual directional coupler or a splitter.

Receiver

The receiver provides the means of converting and detecting the RF or mi-crowave signals to a lower IF or DC signals.There are basically two receivertechniques used in network analysis (see Figure 4).


LO

Harmonics

generator

LO

FundamentalMixing

HarmonicMixing

IF IF

Figure 4 - Fundamental and harmonics mixing receiver

The receivers are broadband tuned receivers that use either a fundamen-tal mixing or harmonic mixing input structure to convert an RF signal toa lower-frequency IF signal. The tuned receivers provide a narrowband-passIntermediate-Frequency (IF) filter to reject spurious signals and minimized thenoise floor of the receiver. The vector measurement systems (tuned receivers)have the highest dynamic ranges, are less suspect from harmonic and spuriousresponses, they can measure phase relationships of input signals and providethe ability to make complex calibrations that lead to more accurate measure-ments.

Analyzing and Display

Once the RF signals have been detected, the network analyzer must process thedetected signals and display the measured values. Network analyzers are mul-tichannel receivers utilizing a reference channel and at least one test channel.Absolute signal levels in the channels, relative signal levels (ratios) between thechannels, or relative phase difference between channels can be measured by thenetwork analyzer. Relative ratio measurements are usually made in dB, whichis the log ratio of an unknown signal (test channel) with a chosen referencesignal (reference channel). For example, 0 dB implies that the two signal levelshave a ratio of unity, while +/—20 dB implies a 10: 1 voltage ratio betweentwo signals. All network analyzer phase measurements are relative measure-ments, with the reference channel signal considered to have zero phase. Theanalyzer then measures the phase difference of the test channel with respect tothe reference channel.

NETWORK ANALYZER SYSTEM ELEMENTS 15

2.5 Operator Calibration

2.5.1 General

All real measurement systems are affected by three types of measurement er-rors:

* Systematic errors.

* Random errors.

* Drift errors.

Calibration is a set of operations which improve measurement accuracy.The calibration procedure compensation for systematic measurement errors(repeatable measurement variation), such as:

Systematic Errors

In our case, systematic errors are caused by non-perfect devices. We assumethat these errors do not vary over time, therefore they can be characterizedand mathematically removed during the calibration process. Systematic errorsare related to (see Figure 5):

* Frequency response errors during transmission or reflection measure-ments.

* Signal leakage within or between components of the system, directivityand crosstalk errors.

* Impedance mismatch due to unequal input and output impedance of theDUT and the network analyzer.

Manufacturers assume that the operator takes care of random errors thatare caused by connectors repeatability and by the cables.


Power ratioRef

AC

Directivity error

Network Analyzer

DUT

Crosstalkerror

Source

mismatcherror

Load

mismatch

error

NetworkAnalyzer

RF in

Frequency response errors* Reflection measurement*Transmission Measurement

Figure 5 - Error correction due to calibration

Random Errors

Random errors vary randomly as a function of time (amplitude and phase).Since there is no way to predict them, they can not be removed. Sources ofrandom errors are:

* Internal noise of the instrument.* Connector and adapters.* Cables.As it mention above it is impossible to remove these errors, but it is possible

to minimize their effects by:

Internal noise * Increasing source power.* Narrowing IF filter.* Using trace averaging.

Connectors and adapter care Connector repeatability is a source of ran-dom measurement errors. For all connectors and adapters, you have to fre-quently do the following :

* Inspect all the connectors for damage or visual defect.* Clean the connectors.Use high quality, well known and preserved connectors and adapters.

Cables Care Coaxial cables connecting the DUT to the analyzer. Cables

can cause random errors, you have to frequently do the fallowing :

OPERATOR CALIBRATION 17

* Inspect for unusual lossy cables.

* Inspect for damage cable connectors.

* Inspect for cables which change response when flexing (this may indicatefor damage near the connectors).

It is strongly recommended to use known high quality and well preservedcables, if high accuracy measurement is needed.

Drift Errors

Drift errors occur when the test results of measurements change, after calibra-tion has been performed. They are primary caused by temperature variation.This errors can be minimized by frequently calibration or use the equipmentin a controlled temperature range, such as 25±5C.

2.5.2 Calibration Reference Plane

Reference plane is where you actually connect your DUT. In most cases, youwill not connect your DUT directly to the Analyzer’s port. More often you willconnect your DUT to the analyzer’s port via some adapters and cables (seeFigure 6).

Network Analyzer HP-8714

RFIN

RF

OUT

Calibration

Reference

Plane

AdaptersCables

DUT

Figure 6 - Calibration reference plane

It is important to remove the effects of the cables and adapters, by performingthe calibration process at the calibration reference plane.


2.5.3 When a Calibration Is Necessary

. You need the best accuracy possible.· You are adapting to a different connector type or other impedance.· You are connecting cables between the DUT and the analyzer test ports.· You are measuring a narrow band or electrically long device.. You are connecting any attenuator or other device on the input or output

of the DUT.

2.5.4 When a Calibration Is Not Necessary

If your test setup meets these conditions, you do not need to perform anyadditional calibrations, however without a user-calibration, the analyzer is notguaranteed to meet its published measurement port specifications.· Your test doesn’t require the best accuracy possible.· Your DUT is connected directly to the reflection part. with no adapters

or intervening cables.· Your DUT impedance matches the impedance of the analyzer.

2.6 Purpose and Use of Different Calibrations

2.6.1 Normalization or Response

Normalization is the simplest type of calibration. The analyzer stores data inits memory and divides subsequent measurements by the stored data to removefrequency response errors. Standard devices are used, Thorough (High qualitycoaxial cable) for transmission, an Open or a Short for reflection.

2.6.2 Response and Isolation

This method of calibration is only necessary when trying to achieve maximumdynamic range (>100 dB) when performing crosstalk measurement or highinsertion loss devices (such as a band pass filter). A response and isolationcalibration uses loads to both ports and Thorough cable to connect them.These measurements are used to remove systematic errors caused by crosstalkin transmission.

PURPOSE AND USE OF DIFFERENT CALIBRATIONS 19

2.6.3 Transmission

Transmission calibration removes systematic errors, caused by source mis-match, frequency response. This calibration requires an Open, a Short anda Thorough standard devices (Enhance mode).

2.6.4 Reflection

This type of calibration removes systematic errors, frequency response, direc-tivity and source mismatch. This calibration requires three standard devices:an Open, a Short and a Load.

Note

All the above calibrations may be slightly different, depend on a specific modelor manufacturer.


3. EXPERIMENT PROCEDURE

3.1 Required Equipment

1. RF Network Analyzer E5062A

2. Type N calibration kit HP - 85032E

3. Band Pass Filter Mini - Circuit BBP - 10.7 MHz

4. Terminator 50Ω NTRM - 50

5. High quality coaxial cable HP-8120-6469

6. 10 m RG-58 coaxial cable

7. Agilent ADS simulation software

3.2 Front Panel View

Refer to Figure 7:

1. Standby Switch -Allows the switch between power-on and standbymode on the E5061A/E5062A.

2. LCD Screen - Displays measurement traces, instrument setting condi-tions, menu bars, the Visual Basic Editor, etc. Consists of a 10.4-inchTFT color LCD.

3. ACTIVE CH/TRACE Block - A group of keys used for selecting theactive channel and active trace.

4. RESPONSE Block - A group of keys used for the selection of a mea-surement parameters/data formats ,displaying, calibration, etc.

5. STIMULUS Block - A group of keys used for specifying the setup forsignal sources, trigger, etc.

6. Floppy Disk Drive - Stores/installs from/to the E5061A/E5062A thefiles containing the instrument setting conditions of the E5061A/E5062A,measurement data, compatible with 3.5-inch, 1.44 MB, DOS (Disk Op-erating System) formatted floppy disks.

EXPERIMENT PROCEDURE 21

2 51 4 3 6 7

891013 12 11

RF

IN

RF

OUT

Figure 7 - Front panel view

7. NAVIGATIONBlock - A group of keys used for the movement/selectionof the focus in menu bars/softkey menu bar/dialog boxes and for manip-ulating markers.

8. ENTRY Block - A group of keys used for entering numeric data on theE5061A/E5062A settings.

9. INSTR STATE Block - A group of keys used for specifying the setupfor controlling and managing the E5061A/E5062A such as executingprinting measurement results, executing VBA macros, and presetting(initializing) the E5061A/E5062A.

10. MKR/ANALYSIS Block A group of keys used for analyzing measure-ment results through markers, the limit test function, etc.

11. Test Port - While the signal is being output from a test port, the yellowLED above the test port lights up. The connector type adopted is the50 ?-based N-type (female) connector.

12. Front USB Port - Used to connect a printer, or an ECal module com-patible with the USB (Universal Serial Bus). Using a USB port allows theaccessories to be connected after the E5061A/E5062A has been poweredon.

13. Ground Terminal - Connected to the chassis of the E5061A/E5062A.You can connect a banana type plug to this terminal.

22 EXPERIMENT PROCEDURE

3.3 Entering Frequency Range

1. Connect the BPF to the network analyzer, as shown in Figure 8.

2. Press the green buttyon Preset, and the Enter key, to start measure-ment.

3. At the STIMULUS Block press Start and insert 5 M/µ (MHz), pressStop and insert 20 M/µ (MHz).

4. You can also set the frequency range by using the Center and Spansoftkeys. For instance if you set the center frequency to 12.5 MHz andthe span to 15MHz, the resulting frequency range would be 5 to 20 MHz.Now you can see the return loss of the filter in the pass and stop band,according to the graph.

What happen to the incident power, at 4 to 7 MHz, and 9 to 12 MHz?

RFIN

RFOUT

10.7

MH

z

BP

F

Figure 8 - Entering frequency range measuring BPF

3.4 Entering Source Power Level

1. Press the Sweep Setup softkeys and then choose Power option and setpower level to 0 dBm.

ENTERING FREQUENCY RANGE 23

3.5 Scaling the Measurement Trace

1. Press the Scale key from RESPONSE block to access the scale menu.

2. To view the complete measurement trace on the display, press Au-toscale.

3. To change the scale per division to 10 dB/division press Scale/Div, 10,dB/division and press Enter.

4. To change the reference value to 0 dB, press Reference Value, Enter0 Enter (dB) .

5. To move the reference position to 9th position, press Reference Posi-tion, Enter, 9, Enter. Figure 9 shows how each reference position isidentified.

2

3

4

56

7

89

10

01

Figure 9 - Reference position numbering

3.6 Calibration for Reflection measurements

When you are required for the best accuracy, or you adapting to a differentconnector type, or you are connecting a coaxial cable to the analyzer test port,it is strongly recommended to perform proper calibration.

1. Connect the system as indicated in the Figure 10.

2. Press Preset and OK .

3. Press CAL key and then choose Calibrate, 1- Port Cal.

4. Connect an open to the reflection port and press Open(f).


5. Connect a short to the reflection port and press Short(f).

6. Connect a load to the reflection port and press Load. When the cali-bration ends press Done.

7. Disconnect the load (50Ω termination) and return the standards devicescarefully to their box.

RFIN

RFOUT

50Ω

Load

open

short

Figure 10 - Calibration for Reflection measurement

3.7 Make a Reflection Simulation and Measure-

ment

In this part of the experiment you will measure the Reflection Coefficient mag-nitude |Γ| measured in dB, the Return Loss of a coaxial cable and the ReturnLoss of a 50Ω termination. Under Reflection measurement you will measureReflection Coefficient magnitude and phase, Return Loss, SWR and impedancemagnitude and phase of passive elements.

3.7.1 Reflection Simulation

1. Draw a network analyzer, using ADS software (see Figure 11 from part2 and Figure 3 from Part 1).

MAKE A REFLECTION SIMULATION AND MEASUREMENT 25

• Assume that the measured date is done at RF frequency (you don’t needa mixer and a LO).

• Assume that the network analyzer operate in the frequency range of300kHz to 1 GHz and the Coupling of the coupler is 10 dB.

• Connect a 10m cocaxial cable to your simulation of a network analyzerterminated with 50Ω Load and simulate S11(Vref/Vinc). Verify that thedata trace falls completely below -16dB. Save the data.

• Replace the coaxial cable with a 25Ω "Term4", simulate S11 compare theresults with your calculation and explain the difference.

V t r a n

Vr e f

V in c

A C

A C 1

S t ep= 1 MH z

S t op= 1 GH z

S t a r t =30 0 kH z

AC

C o up le rSi ng l e

C O UP 1

ZR e f= 50 . Oh m

D ir e c t1 =10 0 dB

Lo s s1 =0 . dB

C V S W R 1= 1 .

M VS W R 1=1 .

C o up li n g= 10 . d B

2

31

C OA X

T L1

R ho =1

T an D =0 .00 4

E r= 2 .2 9

L =10 m e t e r

D o= 3 m m

D i= 0 . 9 m m

Te rm

Te rm2

Z=50 O hm

Nu m=2

T e rm

T e rm 4

Z =50 O hm

N um =4

T e rm

T e rm 3

Z=5 0 Oh m

N um= 3

Pw rS p l it2

PW R 1

S3 1=0 .7 07

S2 1=0 .7 07P _A C

P O R T1

F r eq =f r eq

P ac = po la r (d bm t ow (0 ) , 0 )

Z =50 O hm

N um =1

Figure 11 - Simulation of a coaxial cable connected to a network analyzer.

3.7.2 Reflection Measurement of a Coaxial Cable and Terminator

1. Connect a 10m coaxial cable RG - 58 to the network analyzer, terminatedwith a 50Ω Load as indicated in Figure 12.

2. Press MEAS, choose S11, Press Scale, set 10dB/div and press Enter.

3. Set Freq Start 0.3 MHz, Stop 1GHz. The return loss of the coaxialcable is displayed.

4. Verify that the data trace falls completely below -16dB. Save the dataon your media.


5. Disconnect the cable with a load and connect only the 50Ω terminationdirectly to the RF OUT port, as shown in Figure 12.

6. Measure S11, verify that the data trace falls completely below -30dB.Save the data.

7. Measure the impedance of the termination using Smith chart, by choos-ing Format, Smith, R+jx. Save the data on your media.

RFIN

Coaxial cable

50Ω

Load

RFout

50Ω

Load

Figure 12 - Network Analyzer Agilent E5062A

8. Connect two 25Ω load to the network analyzer and measure S11, comparethe results to your simulation.

3.7.3 Reflection Measurement of an Elliptic BPF

Reflection Coefficient

1. Connect a BPF with center frequency of 10.7 MHz to the network ana-lyzer, as shown in Figure 8.

2. Set the frequency range by pressing Start 5 MHz and Stop 25 MHz.

Press Scale, Autoscale. The reflection coefficient |Γ| in dB as a functionof frequency is displayed. Save the data on your media.

3. Press Format, Lin Mag, To get the absolute value of the reflectioncoefficient (|Γ|) as a function of frequency.

Save the data on your media.

MAKE A REFLECTION SIMULATION AND MEASUREMENT 27

4. Press Polar to get absolute amplitude value and phase of the reflectioncoefficient (|Γ|∠ θ), as a function of frequency. Save the data on yourmedia.

Standing Wave Ratio and Impedance

1. Press Format and SWR. The SWR as a function of frequency is dis-played. Save the data on your media.

2. Press Format, Smith Chart and R+jx for the real and imaginaryvalues of the impedance as a function of frequency. Set the start frequencyto 9 MHz and the stop frequency to 13 MHz, verify that the impedanceof the filter is about 50Ω in the pass Band. Save the data on yourmedia.

3.8 Make a Transmission Simulation and Mea-

surement

In this part of the experiment you will measure the insertion loss (attenuation,S21) of a RG-58 coaxial cable and an ellptic BPF as a function of frequencyusing transmission measurement.

3.8.1 Simulation

1. Set the simulation according to Figure 11.

2. Simulate S21. Verify that the data trace falls completely below 9dB.Save the data.

3. Replace the coaxial cable with an BPF_Elliptic, according to Figure13.

Set the BPF to:

• Center frequency 10.7 MHz

• Bandwidth of the passband 3.6 MHz.

• Ripple 0.1 dB.

• BWstop = 10MHz.


• Astop = 20dB.

Vtran

Vref

Vinc

AC

AC1

Step=1 MHz

Stop=20 MHz

Start=5 MHz

AC

BPF_Elliptic

BPF2

Astop=20 dB

BWstop=1.2 GHz

Ripple=0.1 dB

BWpass=3.6 MHz

Fcenter=10.7 MHz

CouplerSingle

COUP1

ZRef=50. Ohm

Direct1=100 dB

Loss1=0. dB

CVSWR1=1.

MVSWR1=1.

Coupling=10. dB

2

31

Term

Term2

Z=50 Ohm

Num=2

Term

Term4

Z=50 Ohm

Num=4

Term

Term3

Z=50 Ohm

Num=3

PwrSplit2

PWR1

S31=0.707

S21=0.707P_AC

PORT1

Freq=freq

Pac=polar(dbmtow(0),0)

Z=50 Ohm

Num=1

Figure 13 - BPF Simulation.

3.8.2 Measurement Procedure

Transmission Calibration

1. Connect a coaxial cable to the network analyzer.

2. Set the frequencies range to 300kHz - 1GHz.

3. Press Preset, Ok and Measurement, S21.4. Press CAL, calibrate, Response(Thru), Thru, Done.

Procedure

1. Connect a 10m length coaxial cable to the network analyzer, as indicatedin Figure 14.

2. Press Preset, MEAS and choose S21. Press Scale and Autoscale.

Save the data on your media.

MAKE A TRANSMISSION SIMULATION AND MEASUREMENT 29

RFIN

RFout

Coaxial cable

Figure 3-1 Figure 14 - Transmission measurment using coaxial cable

3.8.3 Insertion Loss Measurement of BPF

In this part you will verify that the Insertion Loss of the BPF in the pass band(9.5-11.5 MHz) is less than 1.5dB.

1. Reconnect the BPF to the reflection port of the network analyzer, asindicated in Figure 8.

2. Set the frequency range to start frequency 5MHz stop frequency 20MHz.Save the data on your media.

3. Press Scale, Autoscale.

4. Press Marker Search, Max verify that the center frequency of thefilter is about 10.7 MHz and fill Table-1.

5. Set the marker to 9.5 MHz and 11.5 MHz by pressing Marker 9.5 MHz, and then 11.5 MHz, verify that the insertion loss is less than 1.5 dB.

Center Frequency [email protected] MHz [email protected] MHz

[email protected] [email protected]

Table-1

3.9 -3 dB Band Width

In this part you will verify that the maximum -3 dB bandwidth of the BPF is2.8 MHz (8.9-12.7 MHz).


1. Press Marker and Marker Search, Max Search to find the CenterFrequency.

2. Press Marker and Marker Search, Target Value -3dB, SearchLeft, Search Right and fill Table-2.

Center Frequency Freq.@-3dB Freq.@-3dB

Table-2

3.10 -20 dB and -35 dB Band Width

Use a similar procedure as in the ’-3 dB Band Width’ section and fill [email protected] MHz IL@15 MHz [email protected] MHz IL@50-1000 MHz

Freq.@-20dB Freq.@-20dB Freq.@-35dB Freq.@-35dB

Table-3

3.11 Reflection Measurement

3.12 Final Report

1. Draw a graph with two traces of the insertion loss (S21) of a coaxial cableRG-58 as a function of frequency. One trace is of the real measurementand the second is of the simulation. Find the maximum of Insertion Lossof the cable.

2. Draw a graph with two traces of the return loss (S11 in dB) of a coaxialcable RG-58 as a function of frequency. One trace is of the real measure-ment and the second is of the simulation. Calculate the worst SWR ofthe cable.

3. Draw a graph with two traces of the return loss (S11 in dB) of a 50Ω ter-mination as a function of frequency. One trace is of the real measurementand the second is of the simulation.

a. Use the model of high frequency resistor (see attenuator experiment realresistor), find the value of the capacitor and inductor at frequencies 10,30,100,300and 1000 MHz, based on the smith chart data (real and imaginary part).

-20 DB AND -35 DB BAND WIDTH 31

b. Find the two equations that describe the value of the capacitor and theinductor as a function of frequency.

c. Simulate S11in dB of the termination using ADS software (use frequencyas the independed element)

d. Compare the graphs of simulation and measurement of the S11 in dB.

1. Refer to the specification of a Band Pass Filter at table-5 and the mea-sured data. Draw a graph of the insertion loss of the filter, as a functionof frequency and answer the following questions:

Center Passband 3dB Band. Stop BandModel Freq IL<1.5dB Typical IL>20dB IL>35dBN0 (MHz) (MHz) (MHz) at MHz at MHz

BBP-10.7 110.7 9.5-11.5 8.9-12.7 7.5&15 0.6&50-1000

SWR At Passband<1.7:1SWR At Stopband>16:1

Table-5a. What is the maximum insertion loss of the filter in the passband?b. What is the measured 3dB bandwidth?c. What is the measured frequencies of 20dB and 35dB insertion Loss of

the filter.d. Compare the result of pharagraphes a,b,c to the specification in table-5.5. Using the stored data of the Band Pass Filter, draw the following graphs:a. Return loss as a function of frequency.b. Reflection Coefficient as a function of frequency.c. Polar plot Absolute amplitude and phase of Reflection Coefficient as

a function of frequency.d. SWR as a function of frequency.


Experiment2-NewVectorNetworkAnalyzer Measurement. · 2.3 ReﬂectionandTransmission Reflection...

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