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Andrea Ferrero Dipartimento di Elettronica Politecnico di Torino, Italy

Overview of modern load-pull and other non-linear measurement systems ARFTG Nonlinear Measurements Workshop San Diego, November 2001. Andrea Ferrero Dipartimento di Elettronica Politecnico di Torino, Italy. Basics of load-pull. Definitions. Load-pull

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Andrea Ferrero Dipartimento di Elettronica Politecnico di Torino, Italy

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  1. Overview of modern load-pull and other non-linear measurement systemsARFTG Nonlinear Measurements WorkshopSan Diego, November 2001 Andrea FerreroDipartimento di ElettronicaPolitecnico di Torino, Italy

  2. Basics of load-pull Definitions • Load-pull • Controlling the loading condition at the output port • Source-pull • Controlling the loading condition at the input port • Fundamental load-pull • Controlling the loading/source condition at the fundamental frequency • Harmonic load-pull • Controlling the loading condition at one or more harmonic frequencies ARFTG –2001 – San Diego

  3. Basics of load-pull Example of load-pull data Output power [dBm] @ 1dB gain compression Power Added Efficiency (PAE) [%] @ 2dB gain compression ARFTG –2001 – San Diego

  4. Basics of load-pull Measurement systems • Power meter or scalar analyzer-based • only scalar information on DUT performances • economic • Vector receiver (ANA, 6-port) • vectorial and more complete informations on DUT performances • high accuracy, thanks to vector calibration • expensive • Time Domain Receiver (MTA-NVNA) • Waveform capabilities • Complexity, high cost ARFTG –2001 – San Diego

  5. and power sensors Passive tuners Power Meter Power Sensor G G Power Sensor S L Passive load-pull systems • Passive loads • Mechanical tuners • Electronic tuners (PIN diode-based) ARFTG –2001 – San Diego

  6. Passive load-pull • Features • Single or double slug tuners • High repeatability of tuner positions • Pre-characterization with a network analyzer • High power handling ARFTG –2001 – San Diego

  7. Passive Load Pull Motors Slab Line DUT TUNERS ARFTG –2001 – San Diego

  8. Passive Limits • Drawback • Load reflection coefficient limited in magnitude by tuner and test-set losses • This is true especially for harmonic tuning • higher frequency • optimum load on the edge of the Smith chart ARFTG –2001 – San Diego

  9. LOSS G LOSS G G L L L PreMatching • Pre-matching • To reach higher gamma while characterizing highly mismatched transistors • Pre-matching networks • Pre-matched tuners • Features • Highest gamma attainable • Difficult pre-calibration (5D space!!) • Harmonic Loading uncontrolled ARFTG –2001 – San Diego

  10. PreMatching ARFTG –2001 – San Diego

  11. VECTOR INFO ACTIVE LOADS NETWORK ANALYZER PORT 2 SWITCHING NETWORK NORMAL VNA CAL DUT Real Time load-pull Vector network analyzer-based system OutputLoad InputLoad ARFTG –2001 – San Diego

  12. Active load Active loop technique ARFTG –2001 – San Diego

  13. Harmonic Load Pull • Controlling the Load/Source condition at harmonic frequencies • Waveshaping techniques at microwave frequencies • Great complexity of the system but potential improvement of the performance ARFTG –2001 – San Diego

  14. G f0 G 2f0 Passive load-pull Passive Harmonic system • A Tuner for each harmonic • Complex • Easy to change frequency • More control of the harmonic load • Harmonic Resonators • Difficult to change frequency • Only Phase control of the load Fundamental Harmonic ARFTG –2001 – San Diego

  15. Harmonic active load-pull Extending the active loop technique Politecnico di Torino System ARFTG –2001 – San Diego

  16. Harmonic active load-pull Extending the active loop technique IRCOM Active Harmonic Load Pull ARFTG –2001 – San Diego

  17. 4 Loops Harmonic system VNA Amplifier Loop Unit Switching Unit Couplers DUT and Probe Maury/Paf Active Harmonic Load Pull ARFTG –2001 – San Diego

  18. VECTORAND TD INFO ACTIVE LOADS MTA TD WAVEFORMS Ref Signal Test Signal SWITCHING NETWORK TD CAL REQUIRED DUT Time domain load-pull Transition Analyzer based system OutputLoad InputLoad ARFTG –2001 – San Diego

  19. Calibration and Verfication • Passive System • Coaxial VNA Measurement of the Tuners for different positions (typically thousands) • De-embedding of external components (probe,cables ..) • Real Time Active System • Standard Measurements directly at the reference plane • Error Model as ordinary S-parameters ARFTG –2001 – San Diego

  20. DUT G G in L 1 2 PwrMeter Short NETWORK ANALYZER Short SWITCHING NETWORK Open Thru Load Line G G t 3 Probe Tip Load-pull Accuracy VNA-based system: calibration • Reference plane definitions ARFTG –2001 – San Diego

  21. Uncertainty Main Contributions to Power Waves Calibration Residual Uncertainty • NWA measurement repeatability (0.1 %) • Uncertainty on power calibration coefficient (input TWTA during calibration: 2%, no TWTA 0.5%) • On-wafer probe position repeatability (0.2%) ARFTG –2001 – San Diego

  22. Passive LP System Main Contributions to Uncertainty • tuner position repeatability • S-parameter measurement uncertainty: • residual NWA calibration uncertainty • NWA repeatability • measured power uncertainty (power meter dynamic range) ARFTG –2001 – San Diego

  23. passive LP: red line • active LP Comparison Passive vs. Active Output Power Standard Uncertainty dBm 0.5 0.4 0.34 0.25 0.17 0.086 ARFTG –2001 – San Diego

  24. Load Pull and PA Design • Classical PA design Information like: • Power Sweep • Optimum Loads • MAP based design • Additional info with Active Real Time System • GammaIn • AM/PM conversion • Harmonic Load condition • Time Domain Info ARFTG –2001 – San Diego

  25. DATA SET EXAMPLE Load Pull and PA Design ARFTG –2001 – San Diego

  26. Power Sweep and more 1dB compression Point Pout=26.29 dBmGain= 9.72dB IM3R= -18.34 dBc IM3L=-18.50dBcEff=48.07 % ARFTG –2001 – San Diego

  27. Load Pull and PA Design COMBINING LP MAP INFORMATION TO OPTIMIZE POWER PERFORMANCES 12dB OUTPUT POWER @ 1 dB GAIN COMPRESSION POWER GAIN@ 1 dB GAIN COMPRESSION 26dBm ARFTG –2001 – San Diego

  28. Load Pull and PA Design COMBINING LP MAP INFORMATION TO OPTIMIZE LINEARITY PERFORMANCES PAE @ 1 dB GAIN COMPRESSION 50% -28dBm C/I 3 LEFT @ POUT = 24 dBm ARFTG –2001 – San Diego

  29. Harmonic Information Harmonic Load Effect on Efficiency Power Added Efficiency (PAE) [%] @ 4 GHz, 2dB gain compression as a function of the second harmonic load value (8 GHz). ARFTG –2001 – San Diego

  30. Time Domain LP Istantaneous Working Point Waveform check ARFTG –2001 – San Diego

  31. Conclusions • Load-pull test set as important tools for: • Power amplifier design • Model Verification • Device optimization • Different possibility available according to • Testing needs • Application needs • Budget ARFTG –2001 – San Diego

  32. Many Thanks to • Dave Hartskeerl - Philips Research Laboratories • Surinder Bali – Maury Microwave ARFTG –2001 – San Diego

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