A 20 W GaN-on-Si Solid State Power Amplifier for Q-band Space Communication Systems

This contribution presents a Q-band Solid State Power Amplifier (SSPA) developed by Thales Alenia Space in Italy for next generation High Throughput Satellite (HTS). The Radio Frequency Tray (RFT) is composed by the cascade of a channel amplifier, a linearizer and a high power section. The first two sub-units are built with mainly Gallium Arsenide components, whereas the latter combines sixteen elementary MMICs Power Amplifiers (PAs), designed ad-hoc on a commercial 100 nm gate length Gallium Nitride on Silicon (GaN-Si) process, in WR-22 waveguide structure. Sizes and weight of a first prototype of the SSPA discussed in this paper are [45x22x7.2] (LxWxH) cm
³
and 5.5 Kg, respectively, including the WR-22 waveguide input and output isolators. A version with reduced mass (3.5 kg) and size [29.5x21.0x5.5] (LxWxH) cm
³
is under test at the time of writing and results will be presented at the conference. In the overall Q-band downlink range (i.e., from 37.5 to 42.5GHz) the SSPA delivers more than 20 W of output power with an associated Noise to Power Ratio and power added efficiency better than 18 dB and 15 %, respectively, whereas the gain can be varied from 60 dB to 100 dB through telecommand. To the best of the authors' knowledge, this is the first realization of a 20 W SSPA in Q-band for space applications, at least in Europe.