Determing Amplifier Nonlinearities by using Real-World Signals European Microwave Week 2003

Transcription

1 Determing Amplifier Nonlinearities by using Real-World Signals European Microwave Week 2003 Martin Weiß, Applications 21MAA MAR Re MW /00 Nonlinear Table of Contents and Different Methods: - - Two-Tone - with a real signal - with a real signal Stimulus 1MAA MW 2 Nonlinear 1

2 and Problem Ref -12 dbm * Att 0 db RM * VIEW * RBW 10 khz * VBW 100 khz * SWT 10 s CH PWR ACP Low ACP Up dbm db db B SGL 2 RM VIEW * Ref -12 dbm * Att 0 db * RBW 10 khz * VBW 100 khz * SWT 10 s CH PWR ACP Low ACP Up dbm db * db B SGL Center 1 GHz 400 khz/ Span 4 MHz Center 1 GHz 400 khz/ Span 4 MHz 1MAA MW 3 Nonlinear and Goals Predistortion Method: Digital Predistortion Measure: AM/AM and AM/PM compression curve Model: Polynomial approximation Goal: Low ACP and EVM values 1MAA MW 4 Nonlinear

3 Results with a Network Analyzer P in - P out Increase power FAST Increase power SLOW Decrease power FAST Decrease power SLOW P in 1MAA MW 5 Nonlinear Two tone measurement Princip of with a two-tone signal Which modulation frequency f m must be selected? f 0 -f m f 0 f 0 + f m 1MAA MW 6 Nonlinear

4 Two tone measurement Typical Result with different Modulation Frequencies Colors: Different modulation frequencies Tones K3 K5 1MAA MW 7 Nonlinear The new R&S Vector Signal Generator SMU For more information, visit our stand 1MAA MW 8 Nonlinear 4

5 Results with different test signals CW Multi-Tone - Pulse 1MAA MW 9 Nonlinear Results with different test signals The crest factor of the stimulus signal has a significant influence on the measured AM/AM and AM/PM compression curve CONSEQUENCE: s need to be performed on a signal with the same bandwidth and crest factor as in real operation conditions 1MAA MW 10 Nonlinear

6 Test Setup Overview R&S Software AmpTune 1MAA MW 11 Nonlinear Steps Generate the test signal or load it via file Adjust the DUT input level for the desired RMS output level Downconvert the RF signal to IQ baseband and sample it Perform a synchronization Calculate the AM/AM and AM/PM model Predistore the test signal Verify the predistortion effect 1MAA MW 12 Nonlinear

7 Available Test Signals Bandlimited Noise (generated internally) (generated internally) Signals from WinIQSIM (import via file) Signals from many simulation tool (import via IQWizard) NPR (Noise Power Ratio) signals (import via IQWizard, generation via NPR tool) -> Application Notes 1MAA MW 13 Nonlinear Key Features Precise timing synchronisation and delay calculation Auto-leveling of the DUT output power of RF-to-RF devices (Amplifiers, ) of IQ-to-RF devices (direct-upconverter, ) Support of all R&S Signal Generators and IQ Sources (AMIQ, SMIQ-B60, SMIQ, SMU) Support of all R&S Signal and Spectrum Analyzers (FSIQ, FSP, FSU, FSQ) HTML Report including curve coefficients Free-of-charge software 1MAA MW 14 Nonlinear

8 Signal Processing 1MAA MW 15 Nonlinear AM/AM and AM/PM and Predistortion AM/AM curve AM/AM predistortion 1MAA MW 16 Nonlinear

9 Predistortion Results with 8 MHz signal, 10 db Crest Level [dbm] RF Amplifier CDMA signal, 8 MHz BW Predistored Original Without predistortion CH Power ACP Low ACP Up ALT1 Low ALT1 Up With predistortion CH Power dbm db db db db dbm -70 ACP Low ACP Up db db -80 ALT1 Low db -24,0-20,0-16,0-12,0-8,0-4,0 0,0 4,0 8,0 12,0 16,0 20,0 24,0 Frequency Offset [MHz] ALT1 Up db 1MAA MW 17 Nonlinear Free software AmpTune from Rohde & Schwarz 1MAA MW 18 Nonlinear

10 with Rohde & Schwarz FSQ & FSQ-K70 1MAA MW 19 Nonlinear Principals of Operation Vector Signal Analysis 1MAA MW 20 Nonlinear

11 with Rohde & Schwarz FSQ-K70 1MAA MW 21 Nonlinear Overview over the Presented Methods Suitable for Amplifier Test Stimulus Bandwidth Automatic Predistortion Single Carrier LOW PARTLY Two Tone HIGH AmpTune YES Any Signal HIGH YES FSQ-K70 YES Vector Mod. Signal HIGH Report YES Generator Analysator Network Analyzer ZVx SMU FSP/U/Q SMIQ / SMU FSP/U/Q SMIQ / SMU FSQ Software AmpTune --- 1MAA MW 22 Nonlinear

12 Thank you for your attention! For additional information, please visit our stand 1MAA MW 23 Nonlinear