Agilent PSA Series Spectrum Analyzers Flexible Digital Modulation
Contents
1. 1 Enter gt Agilent Digital Modulation Ch Freq 1 60000 GHz Modulation Analysis Alpha BT 1 00 IF Hide QPSK Completed 1 Q Measured Polar Vector Demod Modulation Format QPSK Meas Filter Root Nyquist RRC Ref Filter Nyquist Alpha BT 1 00 Symbol Rate 3 840000 MHz Meas Interval 256 symbols Figure 6 Polar vector diagram of a QPSK signal with incorrect filter alpha Instructions On the PSA Keystrokes Change view to EVM versus symbol window and zoom in View Trace I O Error Quad View Next window Zoom To see the wrong filter alpha impact on EVM between symbols zoom in on the X axis scale Span Scale Div 1 Symbol Increase the Y axis scaling to see the peaks of the EVM signal going off the vertical scale with incorrect filter alpha Figure 7 Amplitude Scale Div 5 it Agilent Digital Modulation Ch Freq 1 66606 GHz Modulation Analysis pha BT 1 00 IF Hide Co QPSK na rt im HIH ina ry a to Demod Modulation Format QPSK Meas Filter Root Nyquist RRC Ref Filter Nyquist RC Alpha BT 1 00 Symbol Rate 3 840000 MHz Meas Interval 256 symbols Figure 7 EVM versus time symbols of a QPSK signal with incorrect filter alpha Incorrect alphas also show up markedly in CCDF curves Baseband filtering errors cont d Another way to visually identify baseband f2. signal analysis 40 80 MHz Bandwidth Digitizer Technical Overview literature number 5989 1115EN Vector Signal Analysis Basics Application Note 150 15 literature number 5989 1121EN Using Extended Calibration Software Jor Wide Bandwidth Measurements PSA Option 122 amp 89600 VSA Application Note 1443 literature number 5988 7814EN PSA Series Spectrum Analyzer Performance Guide Using 89601A Vector Signal Analysis Software Product Note literature number 5988 5015EN 89650S Wideband VSA System with High Performance Spectrum Analysis Technical Overview literature number 5989 0871EN Measurement personalities and applications Phase Noise Measurement Personality Technical Overview literature number 5988 3698EN Noise Figure Measurement Personality Technical Overview literature number 5988 7884EN External Source Measurement Personality Technical Overview literature number 5989 2240EN Flexible Modulation Analysis Measurement Personality Technical Overview literature number 5989 1119EN W CDMA and HSDPA Measurement Personalities Technical Overview literature number 5988 2388EN GSM with EDGE Measurement Personality Technical Overview literature number 5988 2389EN cdma2000 and 1xEV DV Measurement Personalities Technical Overview literature number 5988 3694EN 1xEV DO Measurement Personality Technical Overview literature number 5988 4828EN cdmaOne Measurement Personality Technical
3. 400 at 101 80 mHz 36 88 mHz sed 56 55 dB 58 70 dB 15 0 11 0 03 dB 0 01 dB Demod Bits Min 40 21 dB 40 75 dB Min 0 99990 0 99992 More 0 00 dBm 56 23 dBm 1 of 2 Figure 17 Numeric result table calculated for maximum and averaged values Agilent Trace View I Q Measured Polar Graph Digital Modulation Ch Freq 200 000 kHz IF Hide Completed Modulation Analysis QPSK 1 Q Error 1 0 Measured Polar Vector Quad View Eye Quad View Numeric Results Demod Bits More 1 of 2 Figure 18 Demodulated bits stream with EVM versus time trace and IQ measured polar vector PSA Series Key Specifications Flexible digital modulation analysis measurement personality Description Specifications Supplemental information Signal acquisition Frequency range2 Specified range 10 MHz to 3 GHz Operational range 3 Hz to 50 GHz Maximum frequency for each PSA model Analysis bandwidth Without 444xA 122 1238 Range IFBW 1 kHz to 10 MHz Flat top IF frequency response 0 12 dB nominal IFBW 10 MHz Phase linearity 1 peak to peak nominal IFBW 6 4 MHz With E444xA 140 1233 Range IFBW 1 kHz to 40 MHz Flat top IF frequency response Supplemental information Please refer to the IF frequency response specifica tions in the 80 40 MHz BW digitizer chapter of PSA the Specification Guide Data block length 10 to 20000 symbols Variable based on samples per symbol Samples per symbol 1 2 4
4. 5 or 104 Symbol clock Internally generated Carrier lock Internally generated Lock range wide Symbol rate or 1 5MHz smaller of nominal for BPSK QPSK OOPSK DOPSK 160AM 640AM 2560AM Symbol rate 2 or 750 kHz smaller of nominal for 8PSK D8PSK Lock range narrow Symbol rate 7 nominal for BPSK Symbol rate 12 5 nominal for QPSK DOPSK 2 4 DOPSK Symbol rate 200 nominal for OOPSK Symbol rate 25 nominal for 8PSK Symbol rate 46 nominal for DBPSK Symbol rate 40 nominal for 160AM 320AM Symbol rate 56 nominal for 640AM Symbol rate 125 nominal for 1280AM Symbol rate 360 nominal for 2560AM See PSA Series spectrum analyzer data sheet for more details literature number 5980 1284E 2 Specified range is the frequency range of all specifications applying Operational range is the frequency range of the personality being operated on each PSA model 3 For wideband modulation analysis up to 80 MHz E444xA 123 is necessary to get maximum performance out of Option 122 at frequencies above 3 05 GHz 4 2 4 or 10 when modulation format is set to OOPSK 5 Clean signal with random data sequence carrier lock is set to wide When the EVM of the signal is not good the automatic carrier lock may find the false spectrum for the carrier frequency In that case the automatic carrier lock works better with the carrier lock set to normal with narrower locking range
5. Overview literature number 5988 3695EN Bluetooth is a trademark owned by the Bluetooth SIG Inc cdma2000 is a registered certification mark of the Telecommunications Industry Association Used under license WLAN Measurement Personality Technical Overview literature number 5989 2781EN NADC PDC Measurement Personality Technical Overview literature number 5988 3697EN TD SDCMA Measurement Personality Technical Overview literature number 5989 0056EN Agilent N5530S Measuring Receiver System Technical Overview literature number 5989 1113EN BenchLink Web Remote Control Software Product Overview literature number 5988 2610EN IntuiLink Software Data Sheet literature number 5980 3115EN Programming Code Compatibility Suite Technical Overview literature number 5989 1111EN Options PSA Series Spectrum Analyzers Video Output Option 124 Technical Overview literature number 5989 1118EN PSA Series Spectrum Analyzers Option H70 70 MHz IF Output Product Overview literature number 5988 5261EN Back to basics Optimizing Dynamic Range for Distortion Measurements Product Note literature number 5980 3079EN PSA Series Amplitude Accuracy Product Note literature number 5980 3080EN PSA Series Swept and FFT Analysis Product Note literature number 5980 3081EN PSA Series Measurement Innovations and Benefits Product Note literature number 5980 3082EN Spectrum Analysis Basics Application Note 1
6. descriptions in this document subject to change without notice Agilent Technologies Inc 2007 2004 Printed in USA January 9 2007 5989 1119EN Agilent Technologies
7. lt 10 kHz 0 4 rms 0 5 rms 0 4 rms 0 5 rms Symbol rate lt 100 kHz 0 4 rms 0 5 rms 0 4 rms 0 5 rms Symbol rate lt 1 MHz 0 5 rms 0 6 rms 0 4 rms 0 5 rms Symbol rate lt 6 MHz 1 5 rms 1 5 rms 0 8 rms 0 8 rms Phase error Symbol rate lt 10 kHz 0 5 rms 0 5 rms 0 4 rms 0 4 rms Symbol rate lt 100 kHz 0 4 rms 0 4 rms 0 3 rms 0 3 rms Symbol rate lt 1 MHz 0 5 rms 0 5 rms 0 3 rms 0 3 rms Symbol rate lt 6 MHz 1 2 rms 1 2 rms 0 7 rms 0 7 rms Frequency error Symbol rate 500 000 tfa nominal l Q origin offset 60 dB nominal 160AM 320AM 640AM 1280AM 2560AM Symbol rate gt 10 kHz Residual errors 0 2 lt a lt 03 01 lt a lt 02 0 2 lt a lt 03 O01 lt a lt 0 2 typical typical 1 Meaningful operational range is limited by the maximum symbol rate For best EVM results the spectrum must be inside of the instrument analysis bandwidth venter frequency Res BW 2 2 Determined by the IFBW and the excess bandwidth factor a of the input signal The entire signal must fit within the selected IFBW 3 These specifications apply to the signal without an input overload message RF input power input atten gt 25 dBm random data sequence and temperature 20 to 30 C Meas filter root nyquist ref filter nyquist results length 150 symbols For modulation formats with equal symbol amplitudes tfa transmitter frequency x frequency reference accuracy Meas f
8. measurement personality requires B7J and BAF E444xA 202 GSM w EDGE measurement personality requires B7J E444xA B78 cdma2000 measurement personality requires B7J E444xA 214 1xEV DV measurement personality requires B7J and B78 E444xA 204 1xEV DO measurement personality requires B7J E444xA BAC cdmaOne measurement personality requires B7J E444xA BAE NADC PDC measurement personality requires B7J E444xA 211 TD SCDMA measurement personality E444xA 217 WLAN measurement personality requires 140 or 122 123 1 Options not available in all countries General purpose measurements E444xA 226 Phase noise measurement personality E444xA 219 Noise figure measurement personality requires 1DS E444xA 241 Flexible digital modulation analysis measurement personality E444xA 266 Programming code compatibility suite E444xA 215 External source control Hardware E444xA 1DS 100 kHz to 3 GHz built in preamplifier E444xA B7J Digital demodulation hardware E4440A 122 80 MHz bandwidth digitizer E4440A only excludes H70 E444xA 140 40 MHz bandwidth digitizer E4440A 43A 45A only excludes 122 H70 E444xA 123 Switchable MW preselector bypass E4440A 43A 45A only excludes AYZ E444xA 124 Y axis video output E444xA AYZ External mixing E4440A 46A 47A 48A only excludes 123 E4440A BAB Replaces type N input connector APC 3 5 connector Amplifiers E444xA 1DS 100 kHz to 3 GHz built in preamplifier Input
9. r 3 00 deg Modulation Analysis QPSK g 10 Y Scale Div 3 00 deg Ref Value et BO 0 00 deg Ref Position Top Ctr Bot Scale Coupling On OFF Figure 5 Zoomed phase error trace with phase modulation interference of 45 kHz at 0 03 7 radians Table 1 Calculating the PM interference No of oles No of Symbols Frequency of PM interference symbol second cycles second In this case 5 frequency of PM interference 3 cycles 3 84 x 10 symbols 256 symbol 1 second 45 kHz The peak deviation is easily determined by looking at the amplitude scale There are about five divisions of peak phase modulation at one degree per division These both correspond to the interference generated with the ESG signal generator Baseband filtering errors Filtering errors are among the most common problems in digital communication design Typical filtering errors can be due to errors in filter alpha wrong filter shape or problems such as incorrect filter coefficients and incorrect window ing In all cases these errors result in increased inter symbol interfer ence and overshoot or undershoot of the baseband signal Alpha defines the sharpness of the filter In fact the lower the alpha the sharper the filter is in the frequency domain and the higher the overshoot in the time domain Conversely the larger the alpha the smaller the overshoot is in the time domain In many communication systems when using Nyquis
10. 50 literature number 5952 0292 8 Hints for Millimeter Wave Spectrum Measurements Application Note literature number 5988 5680EN Spectrum Analyzer Measurements to 325 GHz with the Use of External Mixers Application Note 1453 literature number 5988 9414EN EMI Application Note 150 10 literature number 5968 3661E ia Agilent Email Updates www agilent com find emailupdates Get the latest information on the products and applications you select Remove all doubt Our repair and calibration services will get your equipment back to you performing like new when promised You will get full value out of your Agilent equipment throughout its lifetime Your equipment will be serviced by Agilent trained techni cians using the latest factory calibration procedures automated repair diagnostics and genuine parts You will always have the utmost confidence in your measurements Agilent offers a wide range of additional expert test and measurement services for your equipment including initial start up assistance onsite education and training as well as design system integration and project management For more information on repair and calibration services go to www agilent com find removealldoubt For more information on Agilent Technologies products applications or services please contact your local Agilent office The complete list is available at www agilent com find contactus Product specifications and
11. Agilent PSA Series Spectrum Analyzers Flexible Digital Modulation Analysis Measurement Personality Technical Overview with Self Guided Demonstration Option 241 The PSA Series is Agilent Technologies highest performing spectrum analyzer family From millimeter wave and phase noise measurements to spur searches and cellular communications con formance tests the PSA Series offers a leading edge combination of speed accuracy and dynamic range R amp D and manufacturing engineers in cellular commercial and emerging wireless communi cations aerospace or defense can now easily quickly and accurately perform flexible modulation analy sis on digitally modulated signals with Agilent s new measurement personality Agilent Technologies Flexible Digital Modulation Analysis Inside Agilent PSA Series Spectrum Analyzers A single analyzer for spectrum and modulation analysis The Agilent PSA Series spectrum analyzers with the flexible digital modulation analysis measurement personality Option 241 provide the flexibility of general purpose spectrum analysis combined with the ability to analyze signal modulation quality This powerful troubleshooting combination enables you to quickly identify and quantify impairments on digitally modulated signals for all major modulation formats Now you can perform spectrum and vector measurements using one comprehensive measurement tool By adding this option you can reduce the n
12. Format Meas Filter Root Nyquist RRC Ref Filter Nyquist Symbol Rate 50 000 kHz Meas Interval 256 symbols Figure 11 1 0 polar vector at center frequency 200 kHz Agilent Digital Modulation Ch Freq 200 000 kHz Modulation Analysis IF Wide QPSK Completed X Scale Scale Div 2 088 Sym Ref Value 6 008 Sym Ref Position ft Ctr Right 2 Scale Coupling On Off Figure 12 EVM versus time symbols trace of 20 symbols 12 Using the equalization filter cont d Adaptive equalization Adaptive equalization identifies and removes linear errors from I Q modulated signals by dynamically creating and applying a compensat ing filter These errors include group delay distortion frequency response errors and reflections or multipath distortion You can also uncover DSP errors such as miscoded bits or incorrect filter coefficients Equalization is a tool that designers can use to identify and correct linear errors Pre distorting a signal to correct linear errors can be simpler faster and cheaper than modifying hardware to make corrections Furthermore some wideband signals are almost impossible to measure without adaptive equalization Instructions On the PSA Series Keystrokes Turn equalization on Figure 13 Meas Setup More Equalization EQ Filter On Check the EVM result improvement with EQ filter in numeric result table Next Window Switc
13. The entire spectrum including the frequency offset must fit inside of instrument analysis bandwidth center frequency res BW 2 The automatic carrier lock does not adjust the center frequency 6 Clean signal with random data sequence carrier lock is set to normal The entire spectrum including the frequency offset must fit inside of instrument analysis bandwidth center frequency Res BW 2 Description Specifications Supplemental information Trigger Source Trigger delay Range Repeatability Trigger slope Trigger holdoff Range Resolution Auto trigger Time interval range RF burst trigger Peak carrier power range at RF Input Trigger level range Bandwidth Video IF envelope trigger Range Measurement control Data synchronization Supported data formats Carrier types Modulation formats Single button pre sets Mode for BTS and MS Free run immediate video IF envelope RF burst IF wideband ext front ext rear frame 100 ms to 500 ms 33 ns Positive negative 0 to 500 ms 1 us On Off 27 dBm to 40 dBm 0 to 25 dB 30 dBm to noise floor Single continuous restart pause resume Continuous pulsed burst such as TDMA FSK 2 4 8 MSK type 1 type 2 BPSK QPSK 8PSK OQPSK DOPSK D8PSK 7 4 DOPSK 37 8 8PSK EDGE QAM 16 32 64 128 256 DVBOAM 16 32 64 128 256 W CDMA cdmaOne cdma2000 NADC EDGE GSM PDC PHS TETRA Bluetooth
14. ZigBee 2450MHz VDL Mode3 APC025 Phasel For video RF burst ext front ext rear 0 to 10 s nominal Does an immediate trigger if no trigger occurs before the set time interval IF wideband for repetitive burst signals Relative to signal peak gt 15 MHz nominal User selected synchronization words Single carrier single code channel only Description Specifications Supplemental information Filtering Measurement filter types Nyquist raised cosine root nyquist square root raised cosine IS 95 compatible gaussian EMF EDGE rectangle none Reference filter types Nyquist raised cosine root nyquist square root raised cosine IS 95 compatible gaussian EDGE rectangle half sine User selectable alpha BT Range 0 01 to 1 0 Resolution 0 01 Symbol rate Range IFBW Narrow 1 kHz to 10 MHz nominal IFBW Wide with E444xA 122 123 10 kHz to 80 MHz nominal IFBW Wide with E444xA 140 123 10 kHz to 40 MHz nominal Maximum symbol rate IFBW 1 a 2 Accuracy BPSK QPSK 8PSK DOPSK D8PSK 7 4 DOPSK Symbol rate gt 1kHz Residual errors a 20 3 02 lt a lt 0 3 a 20 3 0 2 lt a lt 03 typical typical Error vector magnitude EVM Symbol rate lt 10 kHz 0 8 rms 0 9 rms 0 7 rms 0 7 rms Symbol rate lt 100 kHz 0 7 rms 0 7 rms 0 6 rms 0 6 rms Symbol rate lt 1 MHz 0 9 rms 0 9 rms 0 6 rms 0 7 rms Symbol rate lt 6 MHz 2 1 rms 2 1 rms 1 2 rms 1 2 rms Magnitude error Symbol rate
15. a magnitude and phase component Magnitude error I O error magnitude Phase error I O error phase Measured signal Ideal signal reference Figure 1 The error vector Instructions On the PSA Series Error vector Keystrokes Access to EVM measurement Figure 2 Measure Modulation Analysis Agilent Digital Modulation Ch Freq 1 00000 GHz Modulation Analysis IF Hide QPSK Figure 2 Polar vector view of EVM measurement Reported EVM is the root mean square rms value of the error vector over time at the instants of the symbol clock transitions It is an acutely sensitive measure of quality Measure Modulation Analysis Spectrum Freq Domain Waveform Time Domain An I Q polar vector display of the signal should appear on the analyzer screen similar to that shown in Figure 2 This is one of the many views of the modulation analysis personality Important related metrics are listed in a table to the left of the vector display Digital modulation analysis troubleshooting 1 0 impairments The following radio signal errors are investigated in this section Symbol rate errors e In channel phase modulation PM interference e Baseband filter errors Symbol rate errors Small deviations in the symbol clock can result in significant modulation errors Even these small errors cause a significant spread of the constellation points and a
16. as filter none ref filter Gaussian results length 148 symbols Meas filter root Nyquist ref filter Nyquist results length 150 symbols 0 6 rms 0 8 rms 0 6 rms 0 9 rms 1 2 rms 1 3 rms 0 2 rms 0 5 rms 0 4 rms 0 6 rms 0 9 rms 0 9 rms 0 3 rms 0 6 rms 0 4 rms 0 6 rms 0 9 rms 0 9 rms Symbol rate 500 000 tfal nominal 60 dB nominal 60 dB nominal 0 7 rms nominal Operated with E4440A 122 or 140 IF path wide and 123 preselector OFF a 0 22 nominal 0 4 rms 0 4 rms 0 6 rms 0 8 rms Operated with E4440A 122 or 140 IF path wide and 123 preselector OFF a 0 22 nominal 0 6 rms 0 7 rms 0 8 rms 1 2 rms Operated with E4440A 122 or 140 IF path wide and 123 preselector OFF a 0 22 nominal 1 4 rms 1 3 rms 1 6 rms 1 9 rms Ordering Information PSA Series spectrum analyzer E4443A 3 Hz to 6 7 GHz E4445A 3 Hz to 13 2 GHz E4440A 3 Hz to 26 5 GHz E4447A 3 Hz to 42 98 GHz E4446A 3 Hz to 44 GHz E4448A 3 Hz to 50 GHz Options To add options to a product use the following ordering scheme Model E444xA x 0 3 5 6 or 8 Example options E4440A B7J E4448A 1DS Digital demodulation hardware E444xA B7J Digital demodulation hardware required for cellular communication measurement personalities Wireless communication measurements E444xA BAF W CDMA measurement personality requires B7J E444xA 210 HSDPA
17. e 8 EVM versus time symbols of a QPSK signal with incorrect filter alpha Trace View 1 Q Measured Polar Graph Agilent Digital Modulation Ch Freq 1 00000 GHz Modulation Analysis Alpha BT 22 IF Hide Completed QPSK i 8 170 Error Quad View Eye Quad View Numeric Results Demod Bits w More Symbols 1 of 2 1 This is true for two level decision For a three level decision there will be two thresholds Figure 9 EVM versus time symbols of a QPSK signal with correct filter alpha The eye diagram illustrated in Figure 9 has a full opening at the midpoint of the eye Since the midpoint of the eye represents the sampling instants of each pulse where the pulse amplitude is a maximum without interference from any other pulse ISI is at a minimum ISI and channel noise will cause deviation of the pulse amplitude values from their full scale by differing amounts during each trace This causes blurring at the decision points since the traces are superimposed The decision threshold as to which symbol 1 or 0 is transmitted is the midpoint of the eye This means that for zero ISI the system can tolerate noise up to one half the vertical opening of the eye Because the ISI reduces the eye opening it reduces noise tolerance This is a useful tool not only for determining the presence of noise but also for determining the robustness of the system 10 Configuring modulation analysis paramet
18. eed for additional equipment help increase measurement accuracy and minimize development time Flexible modulation formats Option 241 supports a wide variety of digital modulation formats including industry standard formats such as IS 95 cdmaOne cdma2000 W CDMA EDGE GSM NADC PDC PHS TETRA Bluetooth ZigBee APCO25 phasel and VDL mode3 If customized formats from existing cellular standards are developed you can easily configure the digital format filter symbol rate and meas urement interval to meet your needs Otherwise you can set up your own custom modulation formats MSK PSK FSK QAM DVBQAM etc and parameters to suit your application Symbol rate errors page 5 In channel phase modulation PM interference Available measurement results The flexible digital modulation analysis measurement personality allows you to measure error vector magnitude EVM the most widely used modulation quality metric in digital communications systems EVM related metrics includes I Q magnitude I Q phase I Q frequency and I Q offset carrier feed through Various traces include I Q polar vector and constellation I and Q eye diagrams magnitude error versus symbol phase error versus symbol and EVM versus symbol For more in depth analysis use the following new PSA capabilities demodulated bits error vector spectrum and EQ channel response frequency and phase For an even more ex
19. ers We ve already seen the importance of modulation parameters for correct modulation analysis To configure and check the complicated parame ters the PSA Series provides user friendly form for easier setup This exercise shows how to configure parameters in the setup form Instructions On the PSA Series Keystrokes Select form to check the current signal configurations Figure 10 Meas Setup Meas Setup Move selected item from modulation format to other parameters Use lt and gt keys below PSA display Digital Modulation Hide r m Modulation Format QPSK Completed 5 Mod Format Average On Avg Number 10 Average Mode Repeat Trace Avg Type RMS FFT Window Type Flat Top Trig Source Free Run Carrier Lock Normal Sync None Burst Search Th 39 99 cB Search Length 10 900AAA ms Sync Word Length 14 symbols Sync Offset symbols i Agilent Ch Freq 1 00000 GHz IF Modulation Analysis QPSK Modulation Format QPSK Heas Filter Root Nyquist Ref Filter Nyquist Alpha BT 8 22 Symbol Rate 3 840800 MHz Meas Interval 256 symbols IF Band Width 15 36 MHz IF Band Width Mode Auto EQ Filter o o o EQ Filter Length 5 EQ Convergence 1 000000 EQ Hold oo o oo Sync Ptrn fooga Figure 10 Convenient format to configure modulation parameters for the target signals Using the equalization filter Thi
20. ffset Rho Mean power Eye diagram Mag error vs time Phase error vs time EVM vs time Equalization filter ON OFF EQ channel response frequency and phase Error vector spectrum RF spectrum Demodulated bits Required options 503 504 or 506 frequency range up to at least 3 GHz 601 or 602 baseband generator 122 or 140 wide bandwidth digitizer Not mandatory for this demo If these options are installed on the PSA use Option 123 as well 241 flexible digital modulation analysis measurement personality Keystrokes Set the carrier frequency to 1 GHz Preset Frequency 1 GHz Set amplitude to 20 dBm Amplitude 20 dBm Select custom mode Mode Custom Real Time 1 Q Baseband Set modulation parameters Data PN Sequence PN23 Filter Select Root Nyquist Filter Alpha 0 22 Enter Return Symbol Rate 3 84 Msps Return Modulation Type Select PSK QPSK Return Turn on the signal Custom On Turn on RF output Instructions On the PSA Series RF On Keystrokes Enter digital modulation analysis mode in the analyzer Preset Mode Digital Modulation Set center frequency to 1 GHz FREQUENCY 1 GHz Change the span to see the measured spectrum Span 10 MHz Demonstration start Error vector magnitude EVM An effective way to quantify modulation accuracy is to compare the
21. formation e Related literature Baseband filtering errors page 8 Using equalization filter page 11 More useful displays page 14 Measurement Capabilities Demonstrations and Explanations Demonstration preparation The following options are required for the ESG and the PSA Series in order to perform this demonstration All demonstrations use the PSA Series and the E4438C ESG vector signal generator Key strokes surrounded by indicate hard keys located on the front panel while key names surrounded by indicate soft keys on the right edge of the display To configure these instruments connect the ESG s 50 Q RF output to the PSA Series 50 Q RF input with a 50 Q RF cable Turn on the power in both instruments Now set up the ESG to generate a QPSK signal Modulation formats MSK GSM EDGE EDGE BPSK QPSK OOPSK DOPSK W CDMA 1 4 DOPSK cdma2000 8PSK D8PSK 32 8 8PSK Bluetooth FSK 2 4 8 NADC QAM 16 32 64 128 256 PDC DVBOAM 16 32 64 128 256 PHS IS 95 TETRA ZigBee 2450 MHz APC025 phase 1 VDL mode3 Model number E4438C Product type ESG vector signal generator PSA Series spectrum analyzer E4440A E4443A E44450 E4446A E4447A E4448A Instructions On the ESG Predefined standards Results displays and analysis tools 1 0 vector amp constellation EVM RMS peak Magnitude error RMS Phase error RMS Frequency error 1 0 origin o
22. h view to eye diagram View Trace Eye Turn EQ filter off and on to find the differences of eye diagram shape Figure 14 Meas Setup More Equalization EQ Filter Off and On Agilent Digital Modulation Ch Freq 200 000 kHz Modulation Analysis X Scale Div IF Hide QPSK Figure 13 EVM versus time symbols trace of 20 symbols with EQ filter ON Completed Equalization EQ Filter 10 On OFF EQ Filter Length 5 EQ Convergence 1 000000 EQ Hold On OFF Reset EQ Filter Agilent Digital Modulation Ch Freq 200 000 kHz Modulation Analysis IF Hide QPSK Figure 14 Eye diagram with EQ filter ON Note Completed Trace View 1 Q Measured Polar Graph 170 Error Quad View Eye Quad View Numeric Results Demod Bits More 1 of 2 The cause of the poor EVM at 200 kHz is the low frequency cut off filter in the ESG signal generator This filter removes low frequency signals and noise and thus the ESG is not specified below 250 kHz The adaptive equalization filter is able to compensate for the tilt low frequency rolloff of this filter and dramatically improve the modulation quality Using the equalization filter cont d Instructions On the PSA Keystrokes Switch the view from eye diagram to EQ filter Trace View Equalizer quad view Figure 15 Note When the EQ filter is turned Off the trace cannot be seen in the eq
23. he PM interference on EVM of QPSK signal with changing view trace The I Q polar constellation should be the first step in identifying the in channel PM problem To view this on the PSA Series spectrum analyzer as shown in Figure 4 follow these steps Instructions On the ESG Keystrokes Change the symbol rate Symbol Rate 3 84 Msps from 3 8415 to 3 84 Msps Go to frequency and phase modulation menu and select phase modulation FM oM toggle M highlighted Set frequency of the internally generated phase modulation signal to 45 kHz M Rate 45 kHz Set phase modulation deviation to 0 03 2 radians or approximately 5 5 degrees M Dev 0 03 pi rad Turn on the phase modulation Select 6M On Instructions Keystrokes On the PSA Series Check the signal with constellation Display 1 Q Polar Type Constellation only display Figure 4 Display 1 0 Points 256 symbols Agilent Digital Modulation Ch Freq 1 06600 GHz IF Wide Completed Modulation Analysis OPSK 10 1 0 Points Offset symbols I Q Measured Polar Constin Pts Symbol 4 I Q Polar Type Constellation 1 0 Rotation 45 0 deg On Off Figure 4 Polar constellation view of QPSK signal with a phase modulation interference of 45 kHz at 0 03 7 radians Note the variation of the phase around the ideal symbol reference point This variation is due to the measured symbols preserving the
24. ilter root nyquist ref filter nyquist results length 800 symbols Noon 18 Description Specifications Supplemental information Error vector magnitude EVM Symbol rate lt 100 kHz 0 7 rms 0 9 rms Symbol rate lt 1 MHz 0 8 rms 1 0 rms Symbol rate lt 6 MHz 2 1 rms 2 7 rms Magnitude error Symbol rate lt 100 kHz 0 3 rms 0 5 rms Symbol rate lt 1 MHz 0 5 rms 0 7 rms Symbol rate lt 6 MHz 1 5 rms 2 0 rms Phase error Symbol rate lt 100 kHz 0 4 rms 0 6 rms Symbol rate lt 1 MHz 0 6 rms 0 7 rms Symbol rate lt 6 MHz 1 5 rms 1 8 rms Frequency error l Q origin offset MSK2 Symbol rate 200 to 300 kHz BT 0 3 Residual errors Phase error 0 3 rms Frequency error 5 Hz tfa l Q origin offset 16 32 64 128 256DVBOAM Symbol rate 6 9 MHz Alpha 0 15 Residual errors Error vector magnitude EVM Frequency 1 0 GHz aPsk3 Symbol rate 5 MHz Residual errors Error vector magnitude EVM Frequency 5 0 GHz Frequency 10 0 GHz Frequency 15 0 GHz Frequency 20 0 GHz aPsk3 Symbol rate 15 MHz Residual errors Error vector magnitude EVM Frequency 5 0 GHz Frequency 10 0 GHz Frequency 15 0 GHz Frequency 20 0 GHz QPSK3 Symbol rate 30 MHz Residual errors Error vector magnitude EVM Frequency 5 0 GHz Frequency 10 0 GHz Frequency 15 0 GHz Frequency 20 0 GHz w tfa transmitter frequency x frequency reference accuracy N Me
25. iltering errors is with the eye diagram view Eye diagrams are commonly used in troubleshooting digital communication systems and can help identify problems such as ISI inter symbol interference and jitter An eye diagram is the display of the I real or Q imaginary signal magnitude versus time that is trig gered by the symbol clock To build the eye diagram the analyzer draws the first trace then overlays the second trace the third trace and so on until the number of symbols specified by Measure Interval is displayed The second trace is a continuation of the first trace the third trace is a continuation of the second trace and so forth In other words the analyzer draws one trace to the end of the display and then wraps it back to the begin ning of the display to start the next trace To create a complete eye dia gram the I or Q signal must alter nate between all states Instructions On the PSA Keystrokes Switch view to eye diagram and zoom out View Trace Eye Zoom Figure 8 Change the filter alpha back to 0 22 Meas Setup Demod Alpha BT 0 22 Enter Restart measurements and compare the Restart differences on eye diagram Figure 9 ii Agilent Digital Modulation Trace View Ch Freq 1 00000 GHz IF Hide Completed ibd ERN Modulation Analysis QPSK Alpha BT 1 00 1 Q Error Quad View Eye Quad View Numeric Results Demod Bits More Symbols 1 of 2 Figur
26. large increase in peak EVM This gives you an idea of what a typical receiver will have to deal with in its attempt to demodulate the incoming signal The effect of symbol rate errors on the different measurements depends on the size of the error If the symbol rate error is too large the instrument cannot demodulate the signal let alone make an EVM measurement Consequently the modulation analysis option is most useful in troubleshooting small symbol rate errors To troubleshoot circuits with a large symbol rate error look at the signal s channel bandwidth To perform this operation use the instructions on this page to set the ESG C for a QPSK signal with a symbol rate of 3 8415 Msps This is a symbol rate error of 0 0015 Msps over the predefined symbol rate This exercise demonstrates the symbol error impact on EVM of signal modulated in QPSK with changing display The power of the flexible digital modulation analysis measurement personal ity is its ability to characterize the radio signal for transmitter troubleshoot ing This section illustrates how to interpret the data to identify symptoms of problems in radio signals with the Agilent PSA Series with Option 241 Instructions Keystrokes On the ESG Change the symbol rate from 3 84 to 3 8415 Msps Symbol Rate 3 8415 Msps Instructions Keystrokes On the PSA Series Change the view menu from vector amp constellation to the constellation
27. only Figure 3 Display 1 Q Polar Type Constellation Agilent Digital Modulation Display 1 0 Points 256 symbols 1 0 Points Offset symbols Ch Freq 1 00000 GHz IF Hide Completed Modulation Analysis QPSK 10 1 Q Measured Polar Constin Pts Symbol 4 1 Q Polar Type Constellation 170 Rotation 45 0 deg On Off Figure 3 Polar constellation view of QPSK signal with a symbol rate error Notice the spreading of symbol decision points and the large value of EVM for a symbol rate error of only 0 0015 Msps 04 In channel phase modulation PM interference When integrating a communications system many signals digital baseband IF and RF are present The close proximity of the compo nents is an invitation to cross talk and can lead to unwanted signals in the signal output These spurious signals are usually too small to be seen in the frequency domain However the modulation analysis personality has the capability to easily highlight the presence of such interference The interfering signal causes the amplitude or phase of the transmitted signal to be different each time the signal passes through the same state PM interference causes a variation of the phase around the ideal symbol reference point In this section set the ESG to generate a phase modulating inter fering signal at 45 kHz and deviation of 0 03 m radians or 5 5 degrees as shown This exercise demonstrates t
28. right amplitude but varying in phase Also note that the average phase error is larger than the magnitude error With the interference identified as a PM interference the next step is to identify the frequency and peak deviation of this PM signal In channel phase modulation PM interference cont d To identify the frequency of the phase modulating signal turn on the phase error versus time display on the PSA Series spectrum analyzer If the number of cycles can be accurately determined the frequency of the phase modulating signal can be determined Refer to Table 1 To do this it could be useful to adjust the scaling using the span and amplitude keys if necessary It may also be helpful to pause the measurement to easier determine the number of cycles Use the Meas Control key to pause the measurement Instructions Keystrokes On the PSA Series Change the measurement view menu View Trace I O Error Quad View Note the regular modulating waveform of the interfering PM signal in the phase error versus time plot If the plot is random it indicates phase noise Move selected windows in quad view Next window below PSA display Select phase error versus symbol window and zoom on Zoom Change the Y scale to see the detail on phase Y Scale Amplitude Scale Div 3 error trace Figure 5 Symbols Agilent Digital Modulation Y Scale Ch Freq 1 00000 GHz IF Hide Completed Somer tly
29. s and outputs E444xA H70 70 MHz IF output excludes 122 140 E444xA H26 Highband preamplifier requires 1DS Connectivity software E444xA 230 BenchLink Web remote control software E444xA 233 N5530S measuring receiver software and license E4440A 235 Wide bandwidth digitizer calibration wizard Accessories E444xA 1CM Rack mount kit E444xA 1CN Front handle kit E444xA 1CP Rack mount with handles E444xA 1CR Rack slide kit E444xA 015 6 GHz return loss measurement accessory kit E444xA 045 Millimeter wave accessory kit E444xA 0B1 Extra manual set including CD ROM E444xA 0B0 Delete manual set Warranty and service Standard warranty is 36 months R 51B Return to Agilent warranty and service plan Calibration R 50C 011 3 Inclusive calibration plan 3 year coverage R 50C 013 3 Inclusive calibration plan and cal data 3 year coverage E444xA OBW Service manual assembly level E444xA UK6 Commercial calibration certificate with test data N7810A PSA Series calibration application software Product Literature PSA in general Selecting the Right Signal Analyzer for Your Needs Selection Guide literature number 5968 3413E PSA Series Brochure literature number 5980 1283E PSA Series Data Sheet literature number 5980 1284E PSA Series Configuration Guide literature number 5989 2773EN Self Guided Demonstration for Spectrum Analysis Product Note literature number 5988 0735EN Wide bandwidth and vector
30. s exercise shows how to eliminate linear error component in baseband filter with equalization filter function Switching the equalization function on and off allows post equalization and pre equalization error measurements to be compared Instructions On the ESG Keystrokes Change the signal frequency from 1 GHz to 200 kHz Frequency 200 kHz Modify the symbol rate from 3 84 Msps to 50 ksps Mode Custom Real Time 1 Q Baseband Symbol Rate 50 ksps Return Instructions On the PSA Series Keystrokes Change the symbol rate to the captured signal Meas Setup Demod Symbol Rate 50 kHz Adjust the center frequency to 200 kHz Frequency 200 kHz Switch view to 1 Q polar vector to check the EVM Figure 11 View Trace I O Measured Polar Graph Display I O Polar Type Vec amp Constellation Change screen view to I Q error quad view for more detail information View Trace 1 Q Error Quad View Move selected window from mag error vs time to EVM vs time to zoom in Next Window Zoom Change X scale to see EVM trace of 20 symbols in detail Figure 12 Span X Scale Scale Div 2 Enter Agilent Digital Modulation IF Hide QPSK Ch Freq 200 000 kHz Modulation Analysis RMS EVM 6 75 PKEVM 14 17 12 95 ane 39 Z Completed C QPSK __1 Q Measured Polar Vector Demod Modulation
31. signal being measured to an ideal signal Figure 1 defines the error vector a measure of the amplitude and phase differences between the ideal modulated signal and the actual modulated signal EVM can be calculated and reported as RMS and peak values and can be measured at multiple points during each symbol time or at symbol times only This is the error vector magnitude EVM EVM is a common modulation quality metric widely used in digital communications CDMA based formats which rely on correlation as part of their operation use another parameter called rho p Rho is a measure of the correlated power to the total power The correlated power is computed by removing frequency phase and time offsets and perform ing a cross correlation between the corrected measured signal and the ideal reference Rho is important because uncorrelated power appears as interference to a receiver Measurement When an EVM measurement is performed the analyzer samples the transmitter output to capture the actual signal trajectory This operation can be performed using the instructions below The signal is demodulated and given knowledge of such functions as symbol clock timing and baseband filtering parameters a corresponding ideal or reference signal is derived mathe matically The error vector is the vector difference at a given time between the ideal reference signal and the measured signal It is a complex quantity that contains
32. t baseband filtering the filter response is shared between the transmitter and the receiver The filters must be compatible and correctly implement ed in each The constellation diagram provides the first indication of baseband filtering errors The smaller overshoots due to an increased alpha is shown by the trajectories between the symbol points This reduces the required peak power and reduces the power requirements of the transmitter Note A lower peak overshoot can also be caused by signal com pression like that in an overdriven amplifier stage To illustrate this error set the PSA Series spectrum analyzer with an incorrect filter alpha as follows The analyzer will display the screen shown in Figure 6 Another useful way to identify baseband filtering errors is by looking at the EVM versus symbol time display Set the filter alpha value to a larger value to demon strate what baseband filtering errors look like in the EVM versus symbol time display Instructions On the ESG Keystrokes Turn off phase modulation of the current signal FM oM select OM Off On the PSA Series Change the measurement view to 0 measured polar graph View Trace I O Measured Polar Graph Change from constellation only to polar vector display Display I O Polar Type Vec amp Constellation Enter the wrong filter alpha to lower the overshoot Figure 6 Meas Setup Demod Alpha BT
33. tensive and flexible set of digital modulation analysis measurements consider combining a PSA Series spectrum analyzer with the Agilent 89600 Series vector signal analysis software 0 99997 0 99997 Soon nnn i page 6 Key features e Analyze and visualize I Q modulation with confidence and simplicity Detect the most common errors with the help of intuitive measurement displays and symbol dot feature Expedite troubleshooting and easily define errors with the various quantitative RMS and peak measurements available in the comprehensive results table Increase productivity and reduce user error with one button setups Minimize training with easy to use display tools eye constellation and vector diagrams Distinguish between linear and non linear sources of error by using the built in adaptive equalizer function Increase measurement confidence with guaranteed specifications below 3 GHz Perform flexible digital modulation analysis on millimeter wave signals up to 50 GHz by adding Option 241 to the PSA E4448A Select from three modulation bandwidths 10 MHz standard PSA 40 MHz PSA E4440A 43A 45A with Option 140 or 80 MHz PSA E4440A 43A 45A with Option 122 Option 123 preselector bypass is recommended to add to Option 140 and 122 for higher performance over 3 GHz This technical overview includes e Measurement capabilities e Demonstrations and explanations e Key specifications e Ordering in
34. ualizer quad Go to error vector spectrum view with EQ filter ON Trace View Error Vector Spectrum quad view Turn off the EQ filter to see the difference between Meas Setup Equalizer EQ Filter Off IQ measured polar vector and IQ reference polar vector trace Figure 16 gt Agilent Digital Modulation Equalization EQ Ch Freq 200 000 kHz IF Hide Completed Filter Modulation Analysis QPSK 0 Convergence 1 000000 Figure 15 Equalizer view with channel frequency response channel phase response and impulse response with EQ filter ON Agilent Equalization EQ Ch Freq 200 000 kHz IF Hide Completed Filter Modulation Analysis QPSK 2 On off EQ Filter Length 5 Digital Modulation 70 Measured Polar Vector EQ Convergence 1 699080 EQ Hold On Off Hz kHz Reset EQ Filter Error Vector Spectrum Figure 16 Error vector spectrum view with EQ filter OFF 14 More Useful Displays Instructions On the PSA Keystrokes Find the statistic result table in Result Metrics Figure 17 Trace View Numeric Results Access to the demodulated bits stream Figure 18 Trace View Demod Bits ii Agilent Digital Modulation Trace View Ch Freq 200 000 KHz IF Hide Completed E ETAS Modulation Analysis QPSK 1 Q Error Avg Q Quad Yiew RMS EVM A 0 92 Eye Peak EVM 2 37 2 02 at Quad View R Error 0 70 0 64 Z 2 25 ats 0 02 at 41 0 37 1 200 0
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