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Optimizing the Stimulus to Maximize System Performance.

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1 Optimizing the Stimulus to Maximize System Performance

2 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 2 Agenda Overview System functionality test and troubleshooting Amplifier test Frequency conversion system test considerations Baseband system test considerations Summary Agenda

3 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 3 Superheterodyne radio architecture x IF LO 90 deg 0 deg Symbol Decode r RF LO LNA Filter I Q IF FILTER ADC Decoder ADC Filter Preselecting filter Baseband FIR Digital signal processor/FPGA RECEIVER RECEIVER Frequency conversion Amplificati on + IF LO 90 deg 0 deg Symbol Encode r x RF LO PA I Q IF Filter TRANSMITTERTRANSMITTER Encoder DAC Filter FIR Digital signal processor/FPGA x x x x Overvie w Baseband Frequency conversion Amplificati on

4 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 4 Baseband DSP IF RF Digital Analog IF LO RF LO Baseband DSP RF Digital Analog RF LO DAC DSP Baseband to RF Digital Analog Superheterody ne Zero IF Direct digital conversion Receiver architecture progression Overvie w ADC

5 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 5 Common stimuli test points 5 x IF LO 90 deg 0 deg Symbol Decode r RF LO LNA Filter I Q IF FILTER ADC Decoder ADC Filter Preselecting filter FIR Digital signal processor/FPGA RECEIVER RECEIVER + IF LO 90 deg 0 deg Symbol Encode r x RF LO PA I Q IF Filter TRANSMITTERTRANSMITTER Encoder DAC Filter FIR Digital signal processor/FPGA x x x x Overvie w Denotes test points

6 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 6 Agenda Overview System functionality test & troubleshooting Amplifier test Frequency conversion system test considerations Baseband system test considerations Summary Frequency conversio n section Amplificati on section Baseband section System Functionality Test & Troubleshooting

7 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 7 Transmitter Receiver Fading Interferers BER/PER analysis What is system functionality test ? transmission channel System Functionality Test & Troubleshooting

8 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 8 Why is system functionality testing important? WLAN PCMCIA card WLAN Tx Interference WLAN cards are inexpensive Rework increases price “Perfect” quality is expected Satellites are expensive Rework may not be possible A/D applications must be reliable System Functionality Test & Troubleshooting

9 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 9 How to perform system functionality tests DUT (Rx) DUT (Rx) DUT (Rx) Commercial fader Field test Record the test signal & play it back System Functionality Test & Troubleshooting Record Play back

10 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 10 Field trial considerations Advantages Expensive Inefficient Non-repeatable Limited: cannot cycle through full range of conditions Rework may not be possible Disadvantages Real operational conditions System Functionality Test & Troubleshooting

11 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 11 Fading considerations Interference Multiple RF/MW channels Fading Profiles & Multiple Paths Required bandwidth increases as the number of paths increase System Functionality Test & Troubleshooting

12 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 12 Waveform recording & streaming considerations Memory depth Impacts recording time (signal analyzer) Impacts play back time (PC and signal generator) Converter Resolution Impacts quantization noise, fidelity, and dynamic range Signal analyzer’s ADCs Signal generator’s DACs Bandwidth Wide enough for capture & playback Frequency Amplitude Sample time Amplitude System Functionality Test & Troubleshooting

13 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 13 Agenda Overview System functionality test and troubleshooting Amplifier test Frequency conversion system considerations Baseband system considerations Summary Frequency conversion section Amplificati on section Baseband section Frequency conversion section Amplificati on section Baseband section Amplifier Test

14 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 14 Why is amplifier characterization important? Amplifier Power In Power Out In- channel distortion Out-of- channel distortion Amplifier Test Amplitude Frequency Amplitude Frequency

15 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 15 How to characterize nonlinear distortion StimulusResponse Traditional stimulus/response test Two-tones, multitone, noise TOI, IMD, NPR Complex stimulus/response test Digitally modulated single and multicarriers ACPR, SEM, EVM Amplifier Test

16 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 16 Test narrow band components Two- tone TOI & IMD Amplifier Test f1 f2 2f2-f1 2f1- f2 f1 f2 DU T... 3rd order IMD In- band Amplitude Frequency

17 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 17 Test broad band components Amplifier Test Out-of-band tests In-band tests Multitone test Noise power ratio test Amplitude Frequency Amplitude Frequency

18 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 18 Complementary cumulative distribution curves Before: Non- compressed signal AWGN (referenc e) After: Compressed signal from distortion Amplifier Test Probability Peak/Average dB

19 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 19 Multitone: phase relationship impacts CCDF Equal phase set: crest factor = dB Random phase set: crest-factor = 6.70 dB Amplifier Test

20 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 20 Multitone test setup: CW sources DUT LPF Combiner IsolatorAMP 1 CW source needed for each tone Amplifier Test Denotes isolators Spectrum analyzer CW source

21 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 21 Advantages Established test procedure Common test equipment Disadvantages Complicated test setup Time-consuming to change signal parameters Difficult to generate repeatable random tones Expensive Amplifier Test Multitone test considerations: CW sources

22 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 22 1 vector signal generator creates many tones DUT Isolator Reduce cost Simplify test procedure Save time Repeatable test setup Accurate test results Control signal parameters Utilize digital predistortion (DPD) capabilities of the multitione signal creation software Amplifier Test Spectrum analyzer Multitone test setup: vector signal generator Vector signal generator

23 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 23 IMD products from DUT Low IMD reduces test uncertainty Minimize test stimulus IMD … even at the output of an external power amplifier! Non-linear distortion measurement Vector signal generator Spectrum analyzer Multitone: example DUT Amplifier Test Signal Studio for enhanced multitone software

24 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 24 Before & after digital predistortion 25 dB improvement Before … Amplifier Test …and After

25 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 25 Images Amplifier Test Images resulting from I/Q skew v I/Q skew of baseband waveform Q I Time, ns time skew, Q leads I Minimize images by adjusting the I/Q skew

26 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 26 Advantages Simple test setup and procedure Easy to modify signal parameters Improved signal quality Repeatable and accurate test results Save time and test equipment cost Disadvantages Output power distributed Carrier feedthrough Multitone test considerations: vector signal generator Amplifier Test

27 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 27 What is noise power ratio (NPR)? Amplifier Test Noise generated By DUT Notch Noise Stimulus DUT Amplitude Frequency Amplitude Frequen cy

28 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 28 NPR test setup: CW and noise source LO RF IF Up converter Noise Source Band Stop Filter DUT CW source Spectrum analyzer NPR stimulus requirements Amplifier Test

29 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 29 NPR test setup: vector signal generator DUT Vector signal generator Spectrum analyzer NPR stimulus requirements LAN or GPIB Signal Studio for NPR software Amplifier Test Save time with simplified test setup Accurate test results Movable notch without analog filters Better dynamic range Repeatable results Phase and CCDF

30 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 30 Advantages of pseudo-random tones over analog noise Amplifier Test Better dynami c range Better signal-to-noise ratio Steeper filter Flatter amplitude Better signal-to-noise ratio Steeper filter Flatter amplitude Analog noise Pseudo-random tones Amplitude Frequency Amplitude Frequency

31 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 31 Complex stimulus/response Amplifier Power In Power Out ACPR, SEM, EVM Digitally modulated single and multicarrier Amplifier Test Amplitude Frequency Amplitude Frequency

32 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 32 Timing and phase offsets impacts the crest factor Multicarrier W-CDMA with no offsets applied AWGN signal (used as a reference) Amplifier Test Apply timing & phase offsets for CDMA Randomize code channels for CDMA Apply phase offsets for multicarrier Apply timing & phase offsets for CDMA Randomize code channels for CDMA Apply phase offsets for multicarrier 18 dB crest factor!

33 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 33 Use clipping to limit the signal peaks Amplifier Test Gaussia n noise Signal after clipping Signal before clipping

34 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 34 Rectangular Clipping Circular Clipping Amplifier Test Common techniques to clip waveforms Peak power without clipping (clipping set to 100%) Peak power without clipping Clipping set to 80% Clipping applied Baseband waveform Vector representati on of clipped peak I waveform Q waveform Vector representati on of clipped I & Q

35 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 35 Agenda Overview System functionality test and troubleshooting Amplifier test Frequency conversion system considerations Baseband system test considerations Summary Frequency conversio n section Baseband section Frequency conversion section Amplificatio n section Baseband section Amplificatio n section Frequency Conversion System

36 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 36 Frequency Conversion System Vector signal generator Amplificatio n section Baseband section Frequency conversion system impacts measurements Vector signal generator Baseband section Amplificatio n section Level accuracy Spectral Purity Bandwidth

37 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 37 Frequency Conversion System What is level accuracy? Absolute Amplitude (dBm) Frequency Amplitude Frequency -10 dBm -100 dBm f1 Relative level accuracy (dB) Amplitude -10 dBm Repeatability (dB) Amplitude Frequency -10 dBm f1 A f2 f1 B Linearity (dB) Frequency 24 dB 1 dB Frequency Amplitude f1 Attenuator hold on

38 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 38 Why is level accuracy important? Frequency Conversion System Case 1: Source has +/-5 dB of output power accuracy. -110dBm spec. -114dBm actual -115dBm setting Power Output -110dBm spec. Power Output dBm actual -111dBm setting Case 2: Source has +/-1 dB of output power accuracy. Frequency Passes test Should pass but fails Fails test

39 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 39 What impacts level accuracy? Automatic level control (ALC) Flatness Crest factor Frequency Conversion System ALC/Burst Modulator ALC Driver ALC Detector Output Attenuator from frequency conversion section Power Frequency Flatness Entire frequency range

40 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 40 How to control level accuracy? Frequency Conversion System For non-bursted signals Use the ALC For bursted signals Use ALC hold Use ALC hold with RF blanking Use power search ALC/Burst Modulator ALC Driver ALC Detector Output Attenuator from frequency conversion section

41 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 41 ALC considerations Frequency Conversion System Amplitude frequency ALC BW =10 kHz ALC BW =1 kHz ALC BW =100 Hz ALC degrades EVM Depends on loop bandwidth chosen and bandwidth of modulated signal ALC detector bandwidth smaller than what it is trying to detect, otherwise level accuracy suffers The smaller the ALC BW, the less it impacts EVM ALC/Burst Modulator ALC Driver ALC Detector Output Attenuator from frequency conversion section Modulated signal

42 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 42 Level control for bursted signals using the ALC Frequency Conversion System Bursted signal Amplitude, V time Marker route to ALC hold or Pulse/RF blank time ALC hold: ALC power is held for this duration ALC is on during this time Pulse/RF blank: ALC is held for this duration and the RF output is blanked, thus resulting in a greater on/off ratio Logic level time Power, dBm RF power envelope of the bursted signal Average power ALC on: ALC will try to correct the power of the off period Marke r 1 2 3

43 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 43 Frequency Conversion System Power flatness affects accuracy of wideband signals f1=2500 f2=270 0 BW=200 MHz As bandwidth increases, the more power flatness impacts level accuracy

44 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 44 Flatness varies by frequency & I/Q source type Frequency Conversion System Absolute level accuracy Power Frequency Flatness Entire frequency range

45 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 45 How level accuracy is impacted by the crest factor Crest factor = 10.5 dB Average (RMS) power – 23.5 dBM Peak power –13 dBm Frequency Conversion System Amplitude time

46 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 46 What is spectral purity? Frequency Conversion System frequency Amplitude time Amplitude Phase noise is expressed as jitter in the time domain Harmonic Spur Non-Harmonic Spur Broadband noise Phase Noise CW signal 2f 0 f0f0

47 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 47 Why is phase noise important? Frequency Conversion System Blocking signal Desired signal Impacts blocking tests Impacts ACPR tests frequency Amplitude Adjacen t Channe l Channel Separation frequency Phas e nois e

48 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 48 Phase noise degrades signal quality Frequency Conversion System Q I Constellation Phase Noise Ideal Signal Error Vector Phase Error Test Signal  Phase noise results in rotation of the constellation  RMS

49 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 49 Phase noise versus offset frequency from carrier Frequency Conversion System A B C A= B= C= 30 dB/decade 20 dB/decade CW only dB/decade D Digital modulation on f      d   Frequency, offset from carrier 10 L(f), SSB phase noise (dBc,/Hz) f  4 f      d  

50 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 50 What does the source’s phase noise do to my signal? Frequency Conversion System  RMS = (  2 L (f) df )  ½ f2f2 f1f1  RMS = Root mean square angular deviation A B ideal low pass filter radians L(f), SSB phase noise (dBc,/Hz) Frequency, offset from carrier 10 Error Vector Test Signal   RMS Ideal Signal (9.87 x °)

51 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 51 1 GHz Ref What improves phase noise performance? Multiple phase locked loops Multiple cascaded phase locked loops PLL’s oscillator YIG or VCO Reference oscillator TCXO or OCXO Frequency Conversion System Reference Oscillator Phase Detector Frac- N  Phase locked loop 1 phase locked loop 30 dB improveme nt Primary Oscillator

52 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 52 Harmonics & non-harmonics Contributes to distortion ACPR dominated by distortion products Reported on data sheet as a single value for a particular frequency range Distortion products contribute to ACPR Frequency Conversion System

53 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 53 Why is bandwidth important? Frequency Conversion System BW m m m m m 3 rd order spectral regrowth 5 th order spectral regrowth Amplified 4 carrier W-CDMA 20 MHz 60 MHz 100 MHz Example: enough bandwidth to transmit 3 rd, 5 th order distortion products for a 20MHz wide 4 carrier W-CDMA signal = 100 MHz

54 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 54 Frequency Conversion System What is bandwidth? -20 MHz+20 MHz 0 Hz frequency 40 MHz occupied bandwidth Baseband bandwidth RF bandwidth Amplitude 3 dB bandwidth

55 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 55 Agenda Overview System functionality test and troubleshooting Amplifier test Frequency conversion system test considerations Baseband system test considerations Summary Frequency conversion section Baseband section Frequency conversion section Amplificatio n section Baseband section Amplificatio n section RF system Baseband System

56 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 56 Mechanical connection Bus configurati on Logic type Stimulus requirements Sample clock FPGAs, DSPs, & ASICS ADC Clock sourc e Data format What is needed from the test equipment? Memory Baseband System

57 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 57 Stimulus requirements Mechanical connection Bus configuration Logic type Sample clock FPGAs, DSPs, & ASICS ADC Clock source Data format Memory Stimuli provided by various baseband generators Function generator simple test stimulus sinusoid, ramp, pulse, triangle Pattern generator pseudo-random bit patterns custom data pattern Waveform generator Complex “real-world” test stimulus 1 Baseband System

58 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 58 Waveform generators Two types of waveform generators Real-time baseband generator Arbitrary waveform generator (AWG or arb) Waveform generated Waveform played in real- time Waveform generated Waveform stored to memory Compact disc Waveform played back from storage medium Real-time generation Baseband System Waveform generation with an arb

59 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 59 Waveform generator hardware considerations Bandwidth wide enough to transmit: desired signal 3 rd and 5 th harmonics Waveform play back memory Enough to play back desired signal Waveform storage memory Large enough to conveniently store your test signals frequency Amplitude Baseband System

60 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 60 Signal creation software considerations Waveform signal creation Commercially available software Create your own waveform Frame header Payload PreambleSync Word Trailer Payload header PayloadCRC Address Type Length ACK NACK FEC Baseband System

61 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 61 Test the baseband system with a complex stimulus Test the baseband system with the same complex stimulus used by the RF system Identify baseband problems before RF integration Avoid costly rework Reduce uncertainty Use same test equipment for baseband & RF tests Vector signal generator Baseband section Vector signal generator Digital outputs Baseband section Receiver test Transmitter test Frequency conversion section Amplification section RF system Digital inputs Frequency conversion section Amplification section RF system Baseband System

62 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 62 Complex stimulus versus PRBS W-CDMA test signal PRBS signal (supplied by pattern generator) 18 dB crest factor! Baseband System

63 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 63 Mechanical connection Short interconnect Variety of break-out- boards Data integrity Bus configuration Logic type Stimulus requirements Sample clock FPGAs, DSPs, & ASICS ADC Clock source Data format Memory Mechanical connection 2 Short interconnect cable Digital outputs Baseband section Vector signal generator Variety of break-out boards Baseband System

64 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 64 Clock source Provides timing between clock & data Need to adjust for any skew Need a variety of clock sources available From device under test, test equipment, or other clock source Flexible clocking Skew adjustments are needed to meet sample and hold criteria of device Mechanical connection Bus configuration Logic type Stimulus requirements Sample clock FPGAs, DSPs, & ASICS ADC Data format Memory Clock sourc e 3 Data after Data before Clock Baseband System

65 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 65 Data format 2’s complement, offset binary, 4-16 bit word size, MSB, LSB Bus configuration Serial, parallel Logic type TTL, CMOS, LVDS Configurable test equipment Flexible enough to test current & future designs Logic type 6 Bus configurati on 5 Adaptabilit y Stimulus requirements Sample clock FPGAs, DSPs, & ASICS ADC Clock source 1 3 Memory Data format 4 Baseband System

66 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 66 Conclusio n Optimizing the Stimulus to Maximize System Performance Realistic stimulus helps to ensure your radio will work in in its operating environment Stimulus requirements have changed for amplifiers Traditional specifications are different for digital modulation Digital baseband system needs a complex stimulus Agilent has flexible test equipment to meet all your stimulus needs Summary

67 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 67 RF and Microwave Vector Signal Generation Agilent’s Vector Signal Generators E4438C ESG Vector signal generator Frequency to 6 GHz Bandwidth up to 160 MHz E8267C PSG Vector signal generator Frequency up to 20 GHz Bandwidth up to 1 GHz For Further Information

68 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 68 Agilent Baseband Studio N5110A Baseband Studio for waveform streaming Virtually unlimited playback memory N5115A Baseband Studio for fading Optimize number of paths versus bandwidth Up to 48 paths or 30 MHz bandwidth N5102A Baseband Studio digital signal interface module Digital I/Q & digital IF output Extremely flexible For Further Information: studio

69 Thank You for Attending

70 Optimizing the Stimulus for Maximum System Performance ©Agilent Technologies, Inc Page 70 [1] “RF Source Basics”; CD # EE [2] “Digital Modulation in Communications - An Introduction”; application note 1298: # E [3] “Characterizing Digitally Modulated Signals with CCDF Curves”; application note: # E [4] “Agilent Signal Generator Spectral Purity”; application Note 388: # References


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