Techniques for the Analysis and Elimination of Transient Oscillations in Wideband and Ultra-Wideband Pulsed Power Amplifiers

Abstract

Wideband pulsed power amplifiers (PAs) often exhibit undesirable transient oscillations at the trailing edges of the pulsed radiofrequency (RF) output. To combat this problem, this paper introduces an approach for predicting and eliminating such transient oscillations in pulsed PAs. Root causes for the transient oscillations are identified and contrasted with other time-domain pulse-distortion phenomena. Effective analytical techniques are presented for predicting transient instability during the PA design process. These techniques are demonstrated using a series of monolithic GaAs HBT Class-A and Class-C ultra-wideband (UWB) pulsed PA RF integrated circuits (RFICs). RFIC variants designed to exhibit no transient oscillations successfully show no such effects; RFIC variants designed without considering transient stability as a design tradeoff do indeed generate pulsed transients with measured oscillation frequencies and damping ratio parameters in less than 2% error with predictions. These results should greatly facilitate the design of pulsed transmitters for wideband/UWB communications and radar applications.