ABSTRACT: When the transistor is in deep compression and its output is composed of multiple harmonics, the device behavior cannot be described correctly by S-parameters, which are frequency domain quantities. It is much more natural to analyze the behavior of the device under test (DUT) in terms of time domain RF voltage and current waveforms. Clear evidence of this is provided by the theoretical description of the different modes of operation of power amplifiers, which is completely done in time domain. In this case, a nonlinear vector network analyzer (NVNA) can be used to measure the incident and reflected a- and b-waves at the transistor input and output, in both amplitude and phase. The data can then reconstruct the time domain RF voltage and current waveforms and RF load lines as well as all the conventional performance parameters of the device, such as input and output power, gain and efficiency.2 Several commercial solutions exist to measure nonlinear transistor performance.
This article will compare Maury Microwave’s MT4463 large signal network analyzer (LSNA) and the MT2000 mixed-signal active loadpull system (MSALP). The MT4463 LSNA was offered in conjunction with Agilent’s Network Measurement and Description Group between 2003 and 2008. The MT2000 is currently offered as an integrated non-50 Ω measurement system, in conjunction with Anteverta-mw.