New Time-Domain Voltage and Current Waveform Measurement Setup for Power Amplifier Characterization and Optimization

This paper reports a novel voltage and current waveform measurement system suitable for large-signal transistor and power amplifier characterization and optimization. This technique is original in its use of a double six-port (SP) reflectometer as a homodyne vector network analyzer, which is calibrated in magnitude and phase by means of a reference multiharmonic signal generator, to measure the waveforms at the output terminal of the device. An active branch load-pull setup is used to control the source impedance at the fundamental frequency, and the load impedance at the fundamental, second, and third harmonic frequencies. The capability of the proposed SP reflectometer-based configuration is demonstrated experimentally, by measuring the voltage and current waveforms of a GaAs metal-semiconductor field-effect transistor that is biased in class AB and tuned for maximum efficiency. To assess the level of accuracy of the proposed method, the same waveforms were also measured using a microwave-transition-analyzer-based system. A comparison of the results shows that the proposed SP reflectometer setup obtains results accurate enough for power amplifier characterization with lower equipment cost.