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Network Analyzers From Small Signal To Large Signal Measurements Doug Rytting Slide 1 Agenda Small Signal Measurements & Error Correction Compression and AM to PM Hot S22 Measurements Load Pull Measurements Pulse Measurements Large Signal Network Analyzer Measurements Slide 2 Network Analyzer Block Diagram RF Source a0 IF IF a3 LO Source IF IF b0 b3 Port - 1 Cable a1 b2 DUT b1 Port - 2 Cable a2 Slide 3 Improvements with Correction ERRORS REMOVED ERRORS REMAINING Port Match Noise and Residuals Directivity Receiver Linearity Tracking Drift after Error-Correction Main Leakage Paths Stability after Error-Correction Repeatability of Connectors, etc Lower Lever Leakage Paths Errors of Calibration Standards Slide 4 Improvements with Correction Slide 5 Calibration Examples – 8 Term Model Seven or more independent known conditions must be measured A known impedance (Z 0) and a port-1 to port-2 connection are required TRL & LRL Thru (T) or Line (L) with known S-parameters [4 conditions] Unknown equal Reflect (R) on port-1 and port-2 [1 condition] Line (L) with known S11 and S 22 [2 conditions] TRM & LRM Thru (T) or Line (L) with known S-parameters [4 conditions] Unknown equal Reflect (R) on port-1 and port-2 [1 condition] Known Match (M) on port-1 and port-2 [2 conditions] TXYZ & LXYZ Thru (T) or Line (L) with known S-parameters [4 conditions] 3 known Reflects (XYZ) on port-1 or port-2 [3 conditions] Traditional TOSL (Overdetermined) Thru (T) with known S-parameters [4 conditions] 3 known Reflects (OSL) on port-1 [3 conditions] LRRM Line (L) with known S-parameters [4 conditions] 2 unknown equal Reflects (RR) on port-1 and port-2 [2 conditions] 3 known Reflect (OSL) on port-2 [3 condition] Known match (M) on port-1 [1 condition] UXYZ Unknown Thru Unknown Line (U) with S12 = S 21 [1 condition] 3 known Reflects (XYZ) on port-1 [3 conditions] 3 known Reflects (XYZ) on port-2 [3 conditions] Slide 6 Agenda Small Signal Measurements & Error Correction Compression and AM to PM Hot S22 Measurements Load Pull Measurements Pulse Measurements Large Signal Network Analyzer Measurements Slide 7 Output Power (dBm) Power Sweep - Compression Saturated output power Compression region Linear region (slope = small-signal gain) Input Power (dBm) Slide 8 Power Sweep -Gain Compression CH1 S21 1og MAG 1 dB/ REF 32 dB 30.991 dB 12.3 dBm C2 0 0 IF BW 3 kHz START -10 dBm CW 902.7 MHz 1 dB compression: input power resulting in 1 dB drop in gain Ratioed measurement Output power available (nonratioed measurement) SWP 420 msec STOP 15 dBm Slide 9 Power Sweep - AM to PM Conversion 1:Transmission 2:Transmission /M Log Mag Phase 1.0 dB/ 5.0 deg/ Ref 21.50 dB Ref -115.7 deg Ch1:Mkr1 -4.50 dBm 20.48 dB Ch2:Mkr2 1.00 dB 0.86 deg 2 1 Use transmission setup with a power sweep Display phase of S21 AM - PM = 0.86 deg/dB 2 1 1 Start -10.00 dBm Start -10.00 dBm CW 900.000 MHz CW 900.000 MHz Stop 0.00 dBm Stop 0.00 dBm Slide 10 Agenda Small Signal Measurements & Error Correction Compression and AM to PM Hot S22 Measurements Load Pull Measurements Pulse Measurements Large Signal Network Analyzer Measurements Slide 11 Hot S22 Measurement System Small signal S-parameters of a nonlinear device in the presence of a high power drive signal Df away from test frequency. Osc a High Power Combine 0 b b 0 a 1 b 1 DUT [A] b 2 a 2 3 a 3 High Power Load High Power Osc Slide 12 Hot S22 Measurement System S-parameters of a nonlinear device at a defined input or output power. a 0 b b 0 a 1 OSC b 1 DUT [A] b 3 a 3 GA 2 a 2 GB Slide 13 Agenda Small Signal Measurements & Error Correction Compression and AM to PM Hot S22 Measurements Load Pull Measurements Pulse Measurements Large Signal Network Analyzer Measurements Slide 14 Load Pull Measurement Need to measure nonlinear device behavior under actual operating conditions Pmax -1 dB -2 dB S22 -3 dB Low power High power Parameter changes vesus output power level Constant output power contours versus output load impedance Slide 15 Load Pull System INPUT IMPEDANCE AND POWER MEASUREMENT SYSTEM X INPUT TUNER X OUTPUT IMPEDANCE AND POWER MEASUREMENT SYSTEM DUT X X OUTPUT TUNER Slide 16 Types of Output Tuners Passive load-pull Active load-pull Harmonic load-pull Simultaneous Drive OSC DUT Slide 17 Harmonic Load Pull System LO Synthesizer HP 8360 1 - 50 GHz Four Channel Frequency Converter HP 8510C/85110A b2 a2 a1 b1 LO Synthesizer Can be Tuned to Harmonics T T fo Source Synthesizer HP 8360 1 - 50 GHz DUT Input Amplifier 1 - 50 GHz TWA Port Drive PIN Switch Port 1 Input Probe Port 2 Output Probe Reflectometer Mounted on Prober 2fo 3fo T Port 3 Coaxial and power cals. T Slide 18 Agenda Small Signal Measurements & Error Correction Compression and AM to PM Hot S22 Measurements Load Pull Measurements Pulse Measurements Large Signal Network Analyzer Measurements Slide 19 High Power Device Pulse Measurements Control DUT Temperature Eliminate temperature as a variable Test high power devices on-wafer at full power Measure devices in "unsafe" DC operating area Test "pulsed" devices in a pulsed environment Test environment = final application (GSM) Pulsed radars/phased array antennas/high power MMIC's Improve device characterization data Model power FET's at full power level Measure IV curves without temperature effects Investigate trapping effects in GaAs Slide 20 Pulse System Capabilities Gate/Bas e T 1 Synchronization of pulses Drain/Collecto r T 2 RF RF PW DC Safe Operating Limit IV plane characterization ID Q2 Q1 Point in pulse vs Frequency or Pulse profile vs Time VD Slide 21 Pulsed Bias/RF Meas System T RF Synthesizer Pulsed-RF Test Set LO Synthesizer T T Network Analyzer Bias Network Gate / Base Bias Pulser Measurement Controller T Drain / Collector Bias Pulser T DC Power Supply Digital Multimeter T Trigger Pulse Generator Slide 22 Agenda Small Signal Measurements & Error Correction Compression and AM to PM Hot S22 Measurements Load Pull Measurements Pulse Measurements Large Signal Network Analyzer Measurements Slide 23 Large Signal Network Analyzer Response Acquisition (LSNA) Stimulus 50 Ohm or Tuner ESG Complete Spectrum Waveforms Harmonics and Modulation Slide 24 Large Signal Network Analyzer Measures magnitude and phase of incident and reflected waves at fundamental, harmonic, and modulation frequencies. Calibrated for relative and absolute measurements for both linear and nonlinear components at the device under test. Calculate calibrated voltage and current in both the time and frequency domains. Combination of a vector network analyzer, sampling scope, spectrum analyzer and power meter. Slide 25 LSNA System Block Diagram Sampler Front End Requires high BW IF Requires Harmonic LO Slide 26 Sampling Converter Fundamentals LP fLO=19.98 MHz = (1GHz-1MHz)/50 RF 50 fLO 100 fLO 1 150 fLO 2 3 IF Freq. (GHz) IF Bandwidth: 4 MHz 1 2 3 Freq. (MHz) Slide 27 LSNA System Block Diagram Mixer Front End Requires harmonic sync Can use high BW IF for modulation Or low BW IF if no modulation Slide 28 Nonlinear Calibration - Model Response a 0 b0 a3 b3 Acquisition Stimulus Modulation Source Actual waves at DUT a1 a2 b1 b2 b2 a2 b1 K a1 Absolute magnitude and phase error term 0 0 2 0 0 2 1 1 0 1 1 0 2 2 0 0 b3 a3 b0 a0 50 Ohm or Tuner Measured waves 7 relative error terms same as a VNA Slide 29 Nonlinear Calibration Relative calibration at the fundamental and harmonic frequencies determines the 7 normal error terms. Power calibration at the fundamental and harmonic frequencies determines the magnitude of K. Phase reference generator calibration determines the phase of K relative to the fundamental frequency. Reference generator is an impulse that must be accurately modeled or measured. Slide 30 Example # 1 Complete device measurement capability using a Large Signal Network Analyzer (LSNA). Slide 31 Device Measurement a1 (t ) a2 (t ) v1 (t ) b1 (t ) b2 (t ) f 0 900MHz ids -0.2 V vg v2 (t ) -1.2 V i1 (t ) i2 (t ) vds Open port 50 Ohm load Slide 32 Example # 2 Device measurement verification and measurement-based model improvement. Slide 33 Model Verification & Improvement Parameter Boundaries GaAs pseudomorphic HEMT gate l=0.2 um w=100 um MODEL TO BE OPTIMIZED “Chalmers Model” generators apply LSNA measured waveforms “Power swept measurements under mismatched conditions” Slide 34 Model Verification & Improvement During OPTIMIZATION Voltage - Current State Space voltage current gate drain Time domain waveforms gate drain Frequency domain Slide 35 Model Verification & Improvement After OPTIMIZATION Voltage - Current State Space voltage current gate drain Time domain waveforms gate drain Frequency domain Slide 36 Vector Network Analyzer References Slide 37 Large Signal Network Analyzer References Slide 38