A new technique for measuring the resonant behavior of power amplifier bias circuits

In this paper, a new and simple technique for measuring the magnitude and phase of low frequency components of bias circuits of power amplifiers is described. The Low-Frequency probe technique is implemented to determine modulation bandwidth and low frequency behaviors of power amplifiers and is also useful in determining the resonant frequencies of peripheral components causing potential instability and oscillations. The construction, set-up and calibration of the probe are discussed and supported by simulation and measurement results.