Low cost AM/AM and AM/PM distortion measurement using distortion-to-amplitude transformations

Amplitude-to-amplitude (AM-AM) and amplitude-to-phase (AM-PM) distortion are two significant effects in power amplifiers at high output power levels. Traditional measurement of amplitude and phase distortion in RF power amplifiers requires the use of expensive vector network analyzers (VNAs). This paper proposes a low cost and accurate test methodology for AM-AM and AM-PM measurement using distortion-to-amplitude conversion using simple load board test circuitry along with the use of hardware and software based difference generation and peak detection mechanisms. It is seen that both distortion effects can be measured with high accuracy while allowing significant reduction in test cost.