High-efficiency X-band Power Amplifiers and Spatial Combiners with Impedance Tuners Using Mem Inductors and Variable Capacitors

This paper presents work towards heterogeneous integration of high-efficiency power amplifiers (PAs) with tuner and biasing circuits implemented with micro-electro-machined elements. The PAs operate in switched mode with over 70% efficiency at X-band. Many such switched-mode amplifiers are used as the active portion of spatial power combining antenna arrays, with 2.3kW ERP at 8.4GHz at 65% drain efficiency, and 10kW ERP at 10GHz with over 60% efficiency. The switched-mode PAs are sensitive to the load impedance and small device variations can degrade efficiency. An output tuner for post-production efficiency tuning is developed with varactor diodes as a demonstration. MEM tuners have advantages of linearity, low power consumption, and low loss. For MEM tuners, variable capacitors are developed with 3:1 tuning range and with Q factor above 200. Lumped element bias lines for these amplifier circuits have been developed with MEM inductors that are suspended in air and have very low parasitic capacitance, allowing for high resonant frequencies. The capacitors and inductors can be assembled on any substrate for true heterogeneous integration.