IP3 measurement Testbench
Fundamental Measurement
- Rigol DG1032 Function Generator
- 40 dB Pad Pin < -20 dBm
- No Pad Pin >= -56 dBm (2 dB offset from above)
- Combiner -3dB, 50Ω Load on unused port
- Amplifier with 4:1 Z ratio output transformer
- Step Attenuator
- 4 dB Pad
- VNWA Port 2, Calibrated with 4dB Pad and DG1032
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3rd Order Measurement
- Rigol DG1032 Function Generator
- Combiner -3dB
- Amplifier with 4:1 Z ratio output transformer
- Step Attenuator
- 4 dB Pad
- VNWA Port 2, Calibrated with 4dB Pad and DG1032
- Average 2f1-f2 and 2f2-f1 dBm measurements
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Fundamental and 3rd Order Plot
Example VNWA Window
Step Attenuator = 20 dB, Pout = -2.1 dBm
Single Point IP3 = -2.1 + ((64.92 - 22.1) / 2) = 19.3 dBm
Example VNWA Window
Step Attenuator = 10 dB, Pout = -3.15 dBm
Single Point IP3 = -3.15 + ((56.63 - 13.15) / 2) = 18.6 dBm
IP3 Versus Emitter Current
Pout ~= -2 dBm, Using IP3 = Pout + dBc/2
Amplifier without Output Transformer
- Using 50Ω Load, adjust signal generator for 20 mVrms using oscilloscope measure function.
- With signal generator connected to amplifier, adjust feed back resistor for 20 mVrms input.
Zin = 50Ω
- Observation, feedback R Zin ~= R / Vgain
700 / (222/20) ~= 63Ω
- Zin ~= 1 / (1/560 + 1/2.7k + 1/63 + 1/1k) ~= 53Ω
- Assuming 4:1 Z ratio output transformer, gain ~= 15 dB
- Bias selected for ~0.1W transistor power
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| Measurements
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| Input | = | 20mVrms
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| Output | = | 222mVrms
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| Vb | = | 2.025V
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| Ve | = | 1.389V
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| Feedback R | = | 700Ω
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