High-efficiency shared-current microwave power amplifier design

The objective of this dissertation is to develop a new microwave power amplifier design using Gallium Arsenide Field Effect Transistors (GaAsFETs) to achieve previously unattainable direct current (DC) to radio frequency (RF) conversion efficiency while overcoming GaAsFET bias limitations.; The power amplifier requires the majority of available power in any communications system. Improving the efficiency of the power amplifier results in many advantages, from reduced heat sink size to smaller, lighter batteries for airborne applications. Before designing the new high efficiency power amplifier, common amplifier terms and performance parameters are defined.; The most important step in designing a power amplifier is selecting the correct power transistor for the particular application. The most common modern devices and technologies are discussed, and a large signal model is simulated. When designing a microwave circuit, component nonlinearities must be taken into account for optimal performance. Detailed capacitor, inductor, and resistor models are presented and their circuits simulated. Microwave printed circuit board (PCB) effects and PCB parasitic capacitances and inductances are also discussed.; A complete high-efficiency shared-current microwave power amplifier design is developed for a military airborne application. The DC bias network, decoupling capacitor network, impedance matching networks, power splitter, power combiner, and mounting system are designed. The complete design is simulated, fabricated, and tested according to performance requirements, and a comparison between design parameters and experimental results is presented.