Basic of Load Pull Measurements Active and Passive load pull & Harmonic load pull testbench

Transcription

1 Basic of Load Pull Measurements Active and Passive load pull & Harmonic load pull testbench credits to Prof. Andrea Ferrero, Politecnico di Torino

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 Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 2

3 Basics of load-pull Example of load-pull data Output power 1dB gain compression Power Added Efficiency (PAE) 2dB gain compression Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 3

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) Waveform capabilities Complexity, high cost Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 4

5 Passive load-pull systems Passive loads Mechanical tuners Electronic tuners (PIN diode-based) Passive tuners and power sensors Power Meter Power Sensor Γ S Γ L Power Sensor Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 5

6 Passive load-pull Features Single or double slug tuners High repeatability of tuner positions Pre-characterization with a network analyzer High power handling 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 Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 6

7 Passive load-pull Pre-matching To reach higher gamma while characterizing highly mismatched transistors Pre-matching networks Pre-matched tuners LOSS Γ L Γ L LOSS Γ L Features Highest gamma attainable Difficult pre-calibration (5D space!!) Harmonic Loading uncontrolled Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 7

8 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 Γ f0 Γ 2f0 Harmonic Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 8

9 Real Time load-pull Vector network analyzer-based system VECTOR INFO Input Load NETWORK ANALYZER SWITCHING 4CHANNEL RECEIVER NETWORK PORT IF BUS2 ACTIVE LOADS Output Load NORMAL VNA CAL DUT Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 9

10 Time domain load-pull Transition Analyzer based system VECTOR AND TD INFO Input Load Ref Signal MTA TD WAVEFORMS SWITCHING NETWORK Test Signal ACTIVE LOADS Output Load TD CAL REQUIRED DUT Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 10

11 Active Load Two signal paths technique Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 11

12 Active load Active loop technique Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 12

13 Active load-pull Comparison of the two techniques Two signal path No risk of oscillations Difficulty to keep constant the load while sweeping the input power the DUT heats up Active loop High load stability, once the loop oscillation problem is solved Simple and safe operation Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 13

14 Harmonic active load-pull Extending the two-signal path technique Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 14

15 Harmonic active load-pull Extending the active loop technique Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 15

16 Load-pull Accuracy VNA-based system: calibration Reference plane definitions HP8510C NETWORK ANALYZER SWITCHING NETWORK 1 Short DUT Thru Γ in Γ Line L 2 Probe Tip 3 Γ t Γ PwrMeter Open Load Short Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 16

17 Uncertainty Evaluation Main Contributions to Power Wave Calibration Residual Uncertainty NVA 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%) Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 17

18 ()(%) up crout u c r ( ) ( ) L Pout = 2 ur pw 2 Example P out uncertainty vs. Γ L 1+ Γ 1 Γ L 4 dbm TWTA : ~2 % 0.79 no TWTA: ~0.55 % 0.41 Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 18

19 Passive LP System Main Contributions to Uncertainty tuner position repeatability S-parameter measurement uncertainty: residual NVA calibration uncertainty NVA repeatability measured power uncertainty (PWM) Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 19

20 Tuner Repeatability Absolute standard uncertainty (tuner repeatability) on S 11, S 21 for each tuner position from 0 to 100 Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 20

21 Uncertainties combinations P in_pwm POWER METER P out_pwm P in_ av S = 1 S POWER SENSOR POWER P in_ PWM P in_av P 1 P out DUT input power, output power and gain: 2 11 out = P 2 out _ PWM S21 S ij : tuner S-parameters (pre-characterization) S SENSOR G T = P P out in_ av Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 21

22 Comparison Passive vs. Active Output Power Standard Uncertainty passive LP: red line active LP dbm Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 22

23 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 Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 23

24 Load Pull and PA Design Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 24

25 Power Sweep and more Power Best Load for Pout GammaL= 0.41, 167 Frequency= 18 GHz db / dbm 1dB compression Point Pout=26.29dBm Gain= 9.72dB IM3R= dbc IM3L=-18.50dBc Eff=48.07 % Pout Gain IM3L IM3R AM/PM Eff Pav (dbm) 1dB Compression Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 25

26 Load Pull and PA Design COMBINING LP MAP INFORMATION TO OPTIMIZE POWER PERFORMANCES 12dB OUTPUT 1 db GAIN COMPRESSION 26dBm POWER 1 db GAIN COMPRESSION Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 26

27 Load Pull and PA Design COMBINING LP MAP INFORMATION TO OPTIMIZE LINEARITY PERFORMANCES 1 db GAIN COMPRESSION 50% -28dBm C/I 3 POUT = 24 dbm Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 27

28 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). Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 28

29 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 Master in Sistemi e Tecnologie a Microonde per le Telecomunicazioni 29