1. December 2002 Generation and Conditioning of Multitone Test Signals

2. Generation & Conditioning of Multitone Test Signals Agenda Linear vs. nonlinear behavior Nonlinear distortion Methods to characterize nonlinear distortion Two-tone measurements Multitone measurements Noise power ratio (NPR) measurements Summary

3. Output Linear versus nonlinear behavior Linear behavior: l input and output frequencies are the same (no additional frequencies created) l output frequency only undergoes magnitude and phase change Frequency f 1 Time Sin 360 o * f * t Frequency A phase shift = t o * 360 o * f 1 f DUT Time A t o A * Sin 360 o * f (t - t o ) Input Output Time Nonlinear behavior: l output frequency may undergo frequency shift (e.g. with mixers) l additional frequencies created (harmonics, intermodulation) Frequency f 1

4. Nonlinear distortion Linear behavior V in = V a cos(w a t) Amplifier [A] V out = AV in AA Linear behavior Vs. Non-linear behavior V in = V a cos(w a t) Amplifier [A] V out = AV in + A 1 (V in ) 2 + A 2 (V in ) 3 +… harmonic distortion AA 2A3A 2 nd harmonic 3 rd harmonic

5. 5 th order IMD Nonlinear distortion Amplifier In Out (3A-2B) (2A-B) (3B-2A) 2 nd harmonics 3 rd harmonics 2B2A f AB 3 rd order IMD typical channel bandwidth (2B-A) 3A 3B AB 2 nd order IMD AB (B-A) Intermodulation distortion 3 rd order IMD 5 th order IMD

6. Methods to characterize nonlinear distortion ACPR AM - AM AM - PM NPRMultitoneTwo-tone

7. PSA performance spectrum analyzer PSG CW signal generators Two-tone measurements DUT LPF Combiner IsolatorAMP Attenuator 2 nd & 3 rd harmonics IMD products

8. 2nd 3rd f Q V GS I DS V Input 1st, 2rd, 3th, etc. harmonics mix together forming IMD Power source cannot supply current I Output Clipped sine waves Fourier transform Rate of compression determines harmonic amplitude & IMD Tones P Output P Input Two-tone IMD

9. Amplifier linearity behavior & common metrics IP 3 or TOI P Output P Input linear Linear amplification Saturated power Gain compression Power at 1 dB of compression Two-tone intermodulation (IMD) Third order intercept point (TOI) P sat. P 1dB P 3rd P 5th Amplifier Power In AB AB Power Out

10. Multitone IMD Why use multitone test signals? For wideband components two-tone measurement results vary depending on tone spacing Simulate real-world operating conditions Stress device with higher peak-to-average ratio Test with multiple phase sets

11. Effect of phase relationships…on peak-to-average ratio PSG CCDF Plots Equal phase set peak-to-average 17.88 dB Random phase set peak-to-average 6.70 dB 63-tone signal

12. Effect of phase relationships…on IMD performance Random phase set #1 3 rd order IMD -60.22 dB Random phase set #2 3 rd order IMD -48.65 dB Equal phase set 3 rd order IMD -52.89 dB

13. Conventional analog test stimulus DUT LPF Combiner + + + IsolatorAMP PSG CW signal generators PSA performance spectrum analyzer

14. Advantages of analog test approach Well established test procedure Common test equipment Disadvantages of analog test approach Complicated test setup Signal parameters are not easily modified Manual tuning Difficult to generate random phase sets Equipment and capital intensive Conventional analog test stimulus

15. Vector test stimulus IQ Internal Baseband Generator E8267C PSG Vector Signal Generator DUT Isolator

16. Multitone Number of tones: 2 to 64 Vary tone spacing: 100 Hz to 80 MHz (2-tone) Tone power: 0 to –40 dB Initial phase: fixed or random E8267C PSG vector signal generator personalities Two-tone Vary tone spacing: 100 Hz to 80 MHz

17. Up to 64 tones Vary tone power Change phase settings 80 MHz correction BW CCDF plot COM-based API LAN/GPI B PSGPSA E8267C PSG vector signal generator personalities … and After Improved IMD suppression Correct with additional devices in the loop Before… Signal Studio for Enhanced Multitone (opt. 408)

18. IMD products from DUT Low IMD reduces test uncertainty Tone correction Minimize test stimulus IMD … even at the output of an external power amplifier! Non-linear distortion measurement E8267C PSG E4440A PSA Enhanced Multitone Measurements DUT

19. Vector test stimulus Advantages of vector test approach Simple test setup and procedure Easily modify signal parameters Apply pre-distortion to improve signal quality Repeatable and accurate test results Save time and capital equipment cost Disadvantages of vector test approach Available output power Carrier feed through Images Relative tone spacing

20. Traditional NPR test methods LO RF IF Up converter Noise Source Band Stop Filter Noise generated By DUT NPR Noise Stimulus Measurement Bandwidth DUT PSA performance spectrum analyzer PSG CW signal generators

21. NPR challenges and alternatives CHALLENGES: Need signal generator + AWGN source + band stop filter TIME & COST AWGN is constant only if measured in a long period REPEATABILITY ALTERNATIVE: Use multiple tones with a large tone density to simulate noise signal

22. Features Vary tone spacing and notch depth Distortion correction Value Simplified test setup Repeatable test results NPR wideband component and satellite test Coming Soon Signal Studio for NPR E8267C PSG Vector Signal Generator personalities LAN/GPI B PSGPSA

23. Summary Nonlinear behavior must be characterized and addressed to minimize in-band and out-of-band interference Distortion Measurements are typically performed using CW signals Common test signals include two-tone, multitone, and NPR signals Digital multi-tone generation approach provides repeatability and cost advantages over analog generation approaches Digital generation approach uses pre-distortion to improve dynamic range, which can minimize cost and setup time

24. Where to find additional information… [1] Kent K. Johnson, Agilent Technologies, Predicting BER II –Measurements for Lowering Radio Cost, http://www.agilent.com/find/BroadbandSymp/ [2] Characterizing Digitally Modulated Signals with CCDF curves, Agilent Technologies Application Note, literature number 5968-6875E [3] Spectrum Analysis Basics, Agilent Technologies Application Note 150, literature number 5952-0292 [4] Optimizing Dynamic Range for Distortion Measurements, Agilent PSA series Product Note, literature number 5980-3079EN [5] www.agilent.com/find/psg [6] www.agilent.com/find/signalstudio [7] www.agilent.com/find/psa