Ku-band solid state power amplifier for Geosat follow-on

A compact 7 W (peak) Ku-band solid state power amplifier (SSPA) has been designed and developed for the Navy's Geosat follow-on (GFO) radar altimeter. This amplifier combines the output of two 5 W internally matched MESFETs with an integral waveguide combiner, and uses an external isofilter to protect the SSPA from load variations and to suppress 2nd and 3rd harmonics to -60 dBc. Drain voltage switching was implemented using a novel modulator design. An automatic levelling control (ALC) circuit maintains constant output power at end of life (EOL) over varying input and environmental conditions. AM/PM conversion was measured at 4.4 degrees peak/dB and the phase linearity was measured at 12.0 degrees p-p. A discussion is included on various growth options and new devices applicable for the future in remote sensing applications such as SeaWinds II, NPOESS, and GFO2.