Modeling and linearization of a parametric power upconverting amplifier

Research toward high output power, high efficiency RF power amplifiers has been growing recently. Upconverting parametric power amplifiers (paramps) have been suggested as one possible solution to the problem of high linearity amplification of complex wideband multi-carrier modulation schemes. Investigation of distortion characteristics of paramps is crucial before its widespread adoption. This paper presents the results of modeling, characterization and feedback linearization of paramps. A single-carrier WCDMA signal was used to derive the instantaneous complex gain function, which was then used to fit a behavioral model. It was found that the distortion is dominated by AM/PM distortion, but that AM/AM (gain compression), and long-term memory effects are also present. The Ghorbani model was used to obtain the best fit memoryless model for the paramp. Excellent agreement was observed between the measured gain function and the Ghorbani model for three different pump power levels. Memoryless digital predistortion was used to linearize the paramp, and a modest ACLR reduction of 10dB was obtained.