Time-domain envelope measurements and simulations of pulse-to-pulse stability in microwave power amplifiers

This paper presents a new measurement system based on heterodyne receiver to characterize the impact of irregular pulsed signals on the pulse-to-pulse (P2P) stability of microwave power amplifiers. The aim of this work is to provide a way of identifying the key design parameters and specifications of power amplifiers, such as thermal management, which have a critical impact on P2P stability. This paper is focused on the impact of thermal effects by applying a worst-case radar waveform that integrates a long silence (i.e. off-time) between each sequence of periodic bursts of pulses. Time-domain envelope measurements and simulations of P2P stability are compared for a 10W S-band GaN HEMT amplifier, with particular regard to thermal time constants of the nonlinear electro-thermal model.