Design Realization and Tests of a Space-Borne GaN Solid State Power Amplifier for Second Generation Galileo Navigation System

This paper discusses the design, realization, and tests of an engineering qualified model solid state power amplifier (SSPA) based on Gallium Nitride (GaN) technology, suitable for the second generation Galileo (G2G) constellation. The developed SSPA includes a power supply unit (PSU) to interface the module with the satellite primary bus, and an electronic power conditioner unit (EPC) to actuate remote telecommand and telemetry services. The radio frequency unit (RFU), based on 0.5-mu m GaN technology, delivers a saturated output power of 300 W, with a minimum gain of 60 dB and 60% of efficiency in the whole E1-Band (i.e., 50 MHz centered at f(0)=1.575 GHz). The RFU, PSU, and EPC subsystems are housed in a single box with limited volume and mass, which has carefully been designed to account for both mechanical and thermal aspects. The realized SSPA has been subject to an extensive test campaign as foreseen by the European Cooperation for Space Standardization standards. It included environmental and mechanical tests, endurance and EMC tests leading to a technology readiness level equal to 6. In particular, under continuous-wave operations and temperatures ranging from -10 degrees C to 70 degrees C in a vacuum, the SSPA delivers, at the reference operating point (correspondingly to roughly 2 dB of compression), an output power in excess of 230 W with a gain higher than 60 dB and an overall efficiency, including the power consumption of the PSU and the EPC, higher than 44%. The SSPA was also tested with the modulated signal that will probably be adopted for the G2G constellation, having 4 dB of peak-to-average power ratio. Results have shown a spectral regrowth of just 25 dBc with 40% of efficiency at 180 W of average output power.