A GaN-Based Solid State Power Amplifier for Satellite Communications

This paper deals with the design and experimental results of the Engineering Model of a Solid State Power Amplifier (SSPA) based on 100 nm gate length Gallium Nitride on Silicon technology and spatial power combining techniques, targeting Ka-band downlink SatCom applications. The SSPA is divided in two main units: the Radio Frequency Tray (RFT) to amplify the useful signal, and the Electronic Power Conditioner to interface the module with the satellite primary bus, to actuate remote telecommand/telemetry services and to set different operating modes. In the overall bandwidth (17.3-20.2 GHz), the SSPA delivers up to 125 W of output power with a minimum efficiency and gain of 24% and 70 dB, respectively. Such remarkable output power level has been achieved combining 16 Monolithic Microwave Integrated Circuits Power Amplifiers designed ad-hoc, with a low-loss Radial splitter/combiner structure developed in waveguide. The RFT of the SSPA also includes a gain control unit, an analogue linearizer and a driver together with a waveguide coupler and an isolator at the output.