Measurement technique for characterizing memory effects in RF power amplifiers

Memory effects are defined as changes in the amplitude and phase of distortion components, caused by changes in the modulation frequency. These are particularly important in cancelling linearizer systems, for example, when distortion is reduced by similar distortion in opposite phase. This paper describes electrical and electro-thermal causes for memory effects, including resonance type phase jumps caused by partially cancelling distortion mechanisms. To measure the phase of IM3 distortion products, a 3-tone test set-up was constructed, and the measured results are presented in this paper.