X-band Power Synthesis Technology Research

With the dramatic advancements of military and commercial communication systems, there have been increasing demands for high power solid-state amplifiers with high efficiency, wide bandwidth and low profile. Because of limited output power from Microwave Monolithic Integrated Circuit (MMIC) solid-state device at microwave and millimeter wave frequencies, power combining techniques are commonly used to deliver larger output power levels. The primary objective of this research is to study high efficiency, wide bandwidth power combining/dividing networks with low insertion loss, design and implement a 100 W pulsed solid-state power amplifier (SSPA) at X band.Various power combining techniques have been reviewed and analyzed. Meanwhile, a variety of factors affected the power combining efficiency are discussed in the thesis. Two methods of power combining at X-band: modified microstrip planar power combining and spatial power combining using radial waveguide, are proposed and investigated in this thesis.A microstrip power divider at X-band is first presented. The 8-way microstrip power divider is implemented by corporating multiple modified Wilkinson power dividers which address coupling between output branches at X-band. Its operation can be modeled and simulated by Advanced Design System (ADS). Measurement results indicate insertion loss is less than 2.5 dB, input return loss better than 12 dB and isolation better than 13 dB over the 9.5 to 10.5 GHz band.A 5-way power divider based radial waveguide is further investigated. Power dividing/combining networks based on radial waveguide, circuit model and equivalent circuit are analyzed. A 5-way power divider based on radial waveguide has been designed and simulated with High Frequency Structure Simulator (HFSS). Measurement results indicate insertion loss is less than 0.67 dB, input return loss better than 10 dB and isolation better than 8.2 dB over the 9.5 to 10.5 GHz band.The power combining pulsed amplifier is designed and fabricated. The combining circuit produces up to 100 W peak output power with a gain variation of±1 dB within the band of interest(9.5～10.5 GHz). The combining efficiency is more than 85%. It provides an excellent heat-sinking capacity. The measurement results demonstrate the desired graceful degradation as multiple devices fail, which indicates a good tolerance to device failures.