This will be presentation from Fluke’s RF Calibration. Welcome to this Seminar from Fluke...

This will be presentation from Fluke’s RF Calibration.

Welcome to this Seminar from Fluke Calibration…..

Spectrum Analyzer Calibration Essentials

©2010 Fluke Corporation Fluke Calibration Web Seminar 2

WelcomeWe are very pleased to bring you this presentation, from Fluke Calibration’s RF.

This Seminars from Fluke Calibration aim to help you in your daily RF Calibration and Metrology applications and are based on Fluke’s extensive experience in:

• the use and design of Calibration Instruments and MET/CAL Software

• our understanding of the unique problems faced when performing RF metrology

Thank you for your time, we hope you find the seminar both valuable and useful.

The Fluke 9640A series RF Reference Sources.

The key component in any RF & Microwave calibration system

and so, lets begin....

Welcome to this Seminar from Fluke Calibration…..

The game is changing ……

simplifying and streamlining RF & Microwave calibration

Presenter:

Bill GaviriaRegional Product Manager, Electrical, RF and SoftwareFluke CalibrationOffice: +1.321.574.0728Direct: +1.425.446.6031Cell: +1.321.626.7845 Email: [email protected] Web: www.flukecal.com (UTC/GMT-5)


mailto:[email protected]

http://www.flukecal.com/

RF and Microwave Calibration Fundamentals

Spectrum Analyzers represent one of the most common RF & Microwave calibration workload items, with calibration procedures among the most complex.

A typical spectrum analyzer calibration procedure includes around 20 tests totaling in excess of 400 test points.

Welcome to this Fluke Calibration Web Seminar …..

Todays topics:• Examining key tests required for a complete & adequate calibration

• Relating tests to typical analyzer architectures and applications

• Simplifying test setups & accelerating procedures with purpose-designed calibration equipment


What is a Spectrum Analyzer?

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Center 500 MHz Span 500 kHz50 kHz/

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Date: 10.JAN.2005 12:11:38

Low Cost Traditional Analog Modern High Performance Handheld Real Time

MixerIF Gain IF Filter Det/Log

AmpVideo Filter

Atten

Local Osc Sweep

Display

(RBW) (VBW)

….a measuring instrument for representation and assessment of the frequency spectrum of a signal in terms of frequency and level.

….allowing users to determine whether signals are free from harmonics, or to separate and weight the components of a modulated signal at different frequencies, etc…

• Somewhat simplified, similar to an AM superheterodyne receiver

– Tuning is swept to display the required frequency range. – The mixer frequency-shifts (down-converts) the input

signal to an intermediate frequency (IF) for processing– IF or Resolution Bandwidth (RBW) filter provides ability to

distinguish (resolve) signals close in frequency

• Most modern spectrum analyzers use two or three down-convertors and digitize the signal.

• Some of the IF filtering and logarithmic conversion can be implemented in digital signal processing.

Frequency extension

• LO Harmonics mixed with the input signal

• Direct conversion to the low IF

• Preselection bandpass filter ensures only desired range of input frequencies mix with LO to avoid false indications

• Band changes automatic, providing continuous frequency sweep display

Harmonic Mixer IF Gain IF Filter Log Amp/Detector

Video Filter

Attenuator

Local Oscillator

SweepDisplay

(RBW) (VBW)

Tunable Preselector

Filter

Example: HP8563 26GHz Analyzer30Hz – 2.9GHz Band 0 = Normal operation, high 1st IF2.75GHz – 6.46GHz Band 1 = Preselected, low 1st IF5.86GHz – 13.2GHz Band 2 = Preselected, low 1st IF, LO 2nd harm12.4GHz – 26.8GHz Band 3 = Preselected, low 1st IF, LO 3rd harm

Microwave spectrum analyzer

Generalized architecture

• Signal digitised after analog IF processing

• Synthesized Local Oscillator

• IF digitized directly by fast ADC for FFT RBW filters and Log conversion

• Cursors, trace storage, remote interface

• ‘Real Time’ architecture similar, signal digitized over wide BW with DSP frequency domain conversion

Mixer IF Gain IF Filter

Log Amp/Detector

Video Filter

Attenuator

Local Osc Synthesizer

Display

(RBW) (VBW)

Freq Ref

Processor Controller

ADC

10MHz

(Simplified block diagram. Practical implementations use double or triple conversion with high 1st IF frequency, and with preselector/harmonic mixer for frequency extension. Also often include optional preamp for increased sensitivity).

Low Cost Traditional Analog Modern High Performance Handheld Real Time

Why calibrate?

• Spectrum analyzers are sophisticated measuring instruments– High performance, tight specifications– A multitude of measurement features– Applications require numeric data– No longer ‘indication only’

• So, calibrate the underlying analyzer performance, on which these measurement features/personalities depend

• Need confidence that measurements are true indication of signal characteristics, not artefacts or impairments introduced by the analyzer itself

Spurious close to carrier measurement3GPP WCDMA adjacent channel leakage ratio measurement

WCDMA code domain power measurement

Calibrated parameters

• Our analysis of spectrum analyzer cal procedures for 15 models from 5 manufacturers found 80 different tests described...

• 20 tests performed on majority of models in study

• In general, common tests are:– Frequency Accuracy– Level Accuracy– Frequency Response– Attenuator Response– Display Linearity– Displayed Average Noise Level– Resolution Bandwidth Accuracy– Resolution Bandwidth Selectivity– Resolution Bandwidth Switching Accuracy– Sweep Time Accuracy– IF Image Response – Noise Sidebands – Residual FM– Residual & Spurious Responses– Harmonic Distortion– 3rd order Intercept (TOI)– Tracking generator tests

(Manufacturers often use specific test names and groupings, but most are similarly titled)

Also including other spectrum analyzer calibration standards documents:German VDE VDI/VDE/DGQ/DKD 2622 Part 11Chinese JJG501-2000

Typical procedure analysis

Calibration Test Test Signal Frequency/Range Tested at LF Only Tests include HF

Frequency Span Accuracy 300MHz - 1.5GHz √

Frequency Readout Accuracy 1.5GHz - 21GHz √

Level Accuracy 50MHz √

Frequency Response 9kHz - 26.5GHz √

Attenuator Switching Accuracy 50MHz √

Display Linearity 50MHz √

Displayed Average Noise level 10MHz - 26.5GHz

Resolution Bandwidth Accuracy 50MHz √

Resolution Bandwidth Selectivity 50MHz √

Resolution Bandwidth Switching Accuracy 50MHz √

Sweep Time Accuracy 500MHz √

Spurious Responses 2GHz - 21.6GHz √

Noise Sidebands 1GHz √

Residual FM 1GHz √

Harmonic Distortion 300MHz - 3.1GHz √

3rd Order Intercept (TOI) & Gain Compression 50MHz - 14GHz √

No input required

E4407B 26 GHz

Analysis of published calibration procedure for a 26GHz analyzer:

Example: The calibration guide published by Agilent Technologies for its ESA series spectrum analyzer product range is 640 pages long!

This tables summarizes tests and test point frequencies for the E4407B model, totalling over 400 individual test points.

Majority of testing is at lower frequencies: 80% of testpoints <3GHz

Frequency performance

• Frequency reference determines basic frequency accuracy

– Reference accuracy & drift/ageing measured directly

• LO synthesiser performance influence frequency span & readout accuracy

– IF (RBW) filter group delay can cause centre frequency shift during sweeping

– LO synth resolution, frequency stepping regime, etc..

• Other Freq Ref & LO Synth influences– Phase noise, residual FM

– Not strictly ‘x-axis’ effects, but still key characteristics

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Mixer IF Gain IF FilterLog

Amp/DetVideo FilterAtten

LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

The display ‘X-axis’.....

Amplitude performance

• Majority of calibration tests & test points relate to amplitude performance

– And the majority of those are performed at frequencies well below the analyzer upper frequency limit

• Amplitude performance is related to many elements within the analyzer, eg:

– Absolute accuracy related to the entire input-ADC chain– Frequency response related to the ‘front-end’ attenuator and

mixer– Harmonics, intermodulation and spurious responses mainly

related to the mixer– Linearity (scale fidelity/log conformance) related to log amp

& detector and/or the ADC

• IF circuits and ADC common to all measurements– Enables many parameters/characteristics to be tested at a

single low frequency, where measurements are easier and uncertainties are smaller

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MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

The display ‘Y-axis’.....


Any questions so far …..

Use the WebEx Chat or Q&A features, please send your questions/comments to the session host……

Frequency/Span Accuracy

• Test of frequency span and readout accuracy

• Frequency reference accuracy generally tested directly– 10MHz Ref O/P measured with counter, and frequency standard

• Displayed Center Frequency & Span affected by other factors

– LO synthesizer resolution, IF BW centre frequency alignment, IF filter group delay, etc

– Tested with accurate (calibrated) frequency synthesizer, locking analyzer and frequency source to common 10MHz reference

– Ref locking not used if frequency readout accuracy tested via displayed signal frequency accuracy alone

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

Frequency/Span Accuracy

• Test of frequency span and readout accuracy

• Frequency reference accuracy generally tested directly– 10MHz Ref O/P measured with counter, and frequency standard

• Displayed Center Frequency & Span affected by other factors

– LO synthesizer resolution, IF BW centre frequency alignment, IF filter group delay, etc

– Tested with accurate (calibrated) frequency synthesizer, locking analyzer and frequency source to common 10MHz reference

– Ref locking not used if frequency readout accuracy tested via displayed signal frequency accuracy alone

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

The 9640A frequency counter feature replaces the counter traditionally needed for the UUT Freq Ref accuracy test. The 9640A can be locked to

an external frequency standard if additional accuracy is required

10MHz Ref O/P

9640A Reference SourceUUT Spectrum Analyzer

10MHz Ref O/P

9640A Counter I/P

10MHz Ref I/P

Displayed Average Noise Level (DANL)

• Test of noise floor over the analyzer’s frequency range– Input terminated with 50Ω– Tested at higher RBW setting and normalised to 1Hz or 10Hz to reduce test time

• Residual/Spurious responses often included with DANL tests as the same setup is required

TerminationMixer

IF Gain IF Filter

Log Amp/Det

Video FilterAtten

LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

UUT Spectrum Analyzer


The 9640A ‘output off’ (STBY) condition provides a convenient alternative to a 50Ω terminator, reducing the

number of items and setup changes required.

Frequency Response

• Test of amplitude response at fixed level over the analyzer’s frequency range, relative to its response at a reference frequency

– May be tested at a number of levels/attenuator settings

• Requires accurate signal level at the analyzer input– Signal generators do not provide sufficient accuracy, even for low-

performance analyzer models– Covering the frequency range (few Hz to many GHz) can be challenging,

traditionally requiring multiple generators and techniques

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

Using a power sensor and splitter at higher frequencies (>4GHz)

Using the 9640A, with its leveling head connected directly to the UUT input


The 9640A provides accurately levelled outputs directly to the UUT input, from 1mHz to 4GHz

Display Linearity/Scale Fidelity

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

This test is much simpler and faster with the 9640A– 9640A features provide the UUT error directly without any need

for calculations or use of attenuator calibration corrections


• Test of amplitude linearity over wide dynamic range at fixed input attenuator and reference level (IF gain) settings

– Tested at single frequency, typically 50 MHz– Logarithmic scale, and also linear scale for many UUTs– Traditionally a level generator with high precision attenuation linearity or calibrated step

attenuators used as calibration standards

RBW Filter Bandwidth & Shape

• Test of IF (RBW) filter 3 dB and 60 dB response for each of the available filter bandwidth settings

– RBW (resolution bandwidth) accuracy tests 3dB BW– Shape factor = 60dB BW / 3dB BW

• Tested at single input frequency, usually 50 – 100 MHz

60dB

3dB • Many procedures use analyzer cursor measurements, relying on calibrated performance for linearity and frequency span

– Simply requiring a stable input signal

• Other procedures require input of accurate attenuation and frequency signals, effectively calibrating the specific characteristics during the test

– Traditionally requiring calibrated step attenuators– The 9640A provides a simpler, faster alternative

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz


10MHz Ref O/P10MHz Ref I/P

RBW Switching

• Tests that filter gain remains constant when changing filter bandwidth setting

• Tested at single input frequency, usually 50 – 100 MHz

∆dB

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

• Procedure simply requires a stable input level– UUT and source often share common frequency reference

to avoid displayed frequency errors at narrow spans


10MHz Ref O/P10MHz Ref I/P


Any questions so far …..

Use the WebEx Chat or Q&A features, please send your questions/comments to the session host……

Sweep Time Accuracy

• Test of sweep timing accuracy• Tested in zero span mode where display horizontal axis is time

– Like an oscilloscope

• AM modulated signal produces time domain display

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz


The 9640A triangular AM feature is purpose designed for spectrum analyzer sweep time calibration, providing a simpler faster alternative to the traditional RF signal

generator modulated by a function generator

IF Image Rejection

• Tests for unwanted response at IF image frequencies– The analyzer responds to input signal at frequencies fLO + fIF and fLO - fIF

– The analyzer design and choice of IF and local oscillator (LO) frequencies are intended to ensure correct display of input signal content at only one frequency

– However, some residual response remains at the “image” frequency

• Test frequencies are dependant on the particular analyzer design– Can be complicated with 2 & 3 stage downconversion– Use manufacturers test frequency recommendations

IR

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

• A signal is input at f1 with the analyzer center frequency also set to f1 to correctly display the signal at a specific level

• The signal and analyzer center frequencies are then both set to the IF image frequency f2

• The change in displayed signal level corresponds to the analyzer IF image rejection

The IF image response test is often included with other tests of unwanted/spurious responses: “Image, Multiple, Out-Of-Band, responses”, “Other Input-related spurious

responses”, “Immunity to Interference”, etc

Noise Sidebands & Phase Noise

• Test of ability to discern close-in signals, related to local oscillator phase noise

– Noise sidebands: “noise level at frequency offsets above and below the carrier”

• Test of phase noise measurement capability– An important measurement feature in modern analyzers, at low and high offset frequencies

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz 9640A Reference SourceUUT Spectrum Analyzer

The 9640A provides low phase noise signals capable of testing most spectrum analyzers, with the 9640A-LPNX for the high-performance models

• Tested at a single input frequency (usually 1GHz)

– Requires low phase noise signal generator(s) used as reference standard

– Typically using UUT analyzer phase noise measurement features

– Phase noise usually normalised to 1Hz bandwidth, and expressed as ratio to fundamental (carrier) signal (dBc/Hz), for a given offset (∆f) from the signal frequency.

To avoid noise correlation the signal source and UUT analyzer must not share a frequency reference.

Residual FM

• Test for any residual FM present on the analyzer local oscillator

• Tested at single input frequency (usually 1GHz)

– Requires low residual FM signal generator as reference standard

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz


The 9640A provides low residual FM signals capable of testing most spectrum analyzers with

the 9640A-LPNX for the high-performance models

• Test method uses linear portion of RBW filter as FM slope demodulator

– RBW filter slope determined using marker features with normal sweep display

– Peak-peak residual FM displayed in zero-span mode, adjusting center frequency to obtain on-screen display

– Measure displayed signal pk-pk with markers, and convert to FM by applying RBW filter slope detection sensitivity

Harmonics

• Test for any input signal harmonics generated internally by the analyzer– Typically analyzer harmonic suppression is quoted at a specific mixer level

• Requires low harmonic content input signal– Signal generators require low pass filtering to obtain sufficiently low harmonic content

• A signal is input at f1 with the analyzer center frequency also set to f1 to correctly display the signal at a specific level

• Without changing any other settings, the analyzer center frequency is set to the 2nd harmonic frequency f2

• The change in displayed signal level corresponds to the analyzer 2nd harmonic suppression (rejection)


The 9640A provides low harmonic content signals capable of testing the majority of spectrum analyzer models

without the need for low pass filters

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

Note: Second harmonic intercept (SHI) is a mixer level independent specification of harmonic performance, calculated from the harmonic suppression and mixer level. Testing SHI allows use of higher signal

levels, relaxing signal source harmonic content requirements.

3rd Order Intercept (TOI)

• Test for unwanted intermodulation products generated internally by the analyzer

– TOI is mixer level independent intercept value

• Tested with two equal level signals with a small (50kHz) frequency difference

– Signals applied via a splitter or directional coupler

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz

f2

f1

Using a directional coupler/bridge. Signal levels are adjusted to account for differing coupler/bridge port losses.

f1 f2

Using a power splitter

IR3

2f2 - f12f1 - f2

f1 f2

Gain Compression

• Tests for reduction in gain caused by increasing signal amplitude

• Tested by measuring change in displayed level of a small signal when a large signal is also applied to the input

– Signals traditionally applied via a splitter or directional coupler– Smaller signal around 35dB < larger signal at UUT I/P

f1 f2

f2

f1

MixerIF

Gain IF FilterLog


LO Synth

Display

(RBW) (VBW)

Freq Ref


ADC

10MHz Using a directional coupler/bridge.

Using a power splitter

Using purpose designed equipment

• Typical 26GHz analyzer calibration procedure requires 24 equipment setups

– Employs 6 individual signal sources– Many are obsolete or presenting maintenance & support

difficulties, usually the lower frequency sources

• Cost effective alternative: deployment of a 9640A Reference Source as core of spectrum analyzer calibration system

– 24 setups reduced to 4 for a typical 26GHz analyzer– Majority of testing addressed by a single source– Automated system capacity increased up to 25%– Automated system operator intervention significantly

reduced, 90mins “walkaway” time in a 2 hour run– Operator efficiency greatly improved, by up to 60%

Fluke 9640A RF Reference Source

Using purpose designed equipment

• Frequency Accuracy

• RBW Accuracy• Filter Shape• RBW Switching• Display Linearity• Attenuator

Accuracy• Image Responses

• Displayed Noise Level• Residual Responses

• Noise Sidebands• Phase Noise• Residual FM

• Harmonics

• Level Accuracy• Frequency Response

• Display Linearity• Attenuator Accuracy

• 3rd Order Intercept• Gain Compression

• Sweep Time Accuracy

31

Further related information

©2011 Fluke Corporation

• Visit www.flukecal.com/products/rf-calibration , selecting the ‘Knowledge and information’ tab from the 9640A RF Reference Source page for related technical papers and application notes, including:

– Spectrum analyzer harmonics calibration– Phase noise in RF calibration– Attenuator calibration– Precision modulation measurement– RF & Microwave calibration fundamentals– Etc....

• These technical papers contain further useful references – Including conference proceedings, technical journals and

other industry sources, etc...

• Visit www.flukecal.com/rfvideos for several brief RF demonstration videos, including

– Spectrum analyzer calibration automation– Spectrum analyzer scale fidelity testing– Power sensor linearity testing– Benefits of the 9640A over traditional RF Cal methods– Other 9640A applications and features.....

White papers, application notes, etc, relevant to spectrum analyzer and other RF and microwave calibrations....

http://www.flukecal.com/products/rf-calibration

http://www.flukecal.com/rfvideos


Calibration and metrology trainingCalibration and metrology training• Instructor-Led Classroom Training

– MET-101 Basic Hands-on Metrology – MET-301 Advanced Hands-on Metrology – MET-302 Hands-on Metrology Statistics – Cal Lab Management for the 21st Century – Metrology for Cal Lab Personnel (A CCT prep course) – MET/CAL Database and Reports – MET/CAL Procedure Writing – MET/CAL Advanced Programming Techniques – On-Site Training – Product Specific Training

• Instructor-Led Web-Based Training– MET/CAL Database Web-Based Training – MET/CAL Procedure Development Web-Based Training

• Self-Paced Web-Based Training– Introduction to Measurement and Calibration – Precision Electrical Measurement – Measurement Uncertainty – AC/DC Calibration and Metrology – Metrology for Cal Lab Personnel (A CCT prep course)

• Self-Paced Training Tools– MET/CAL-CBT7 Computer Based Training – MET/CAL-CBT/PW Computer-Based Training – Cal-Book: Philosophy in Practice textbook

More information: www.flukecal.com/fluketraining/courses

Thank you.

For material related to this session, visit our web site:http://www.flukecal.com

http://www.flukecal.com/

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