Linearization of a Spatially-Combined X-Band 100-W GaAs FET Power Amplifier System with Predistortion Linearizer

This paper presents the design and performance of an X-band GaAs FET power amplifier (PA) system with 100-W of saturated output power. A simple and cost-effective predistortion linearizer is developed to increase the linear output power of the PA system. To spatially combine output powers of GaAs FETs and to launch output signals directly into the WR-112 waveguide, the PA uses a pair of microstrip-to-coaxial transition probes. Measurement shows that linearization significantly reduces the PA's nonlinear signal distortions, resulting in a 3 dB increase of operating linear output power.