GaN-FET Class-E Amplifier for 60-MHz Radar

A prototype power amplifier (PA) using GaN FETs is developed for space-based surface-penetrating radar at 60 MHz. LDMOS FETs would typically be used at this frequency, but the need for space-qualified components mandates the use of GaN. A push-pull class-E design delivers 80 W to a matched load with an overall efficiency of 83.3 percent. It delivers 43+ W with 78+ percent efficiency into loads with an SWR of 1.5, and 28+ W with 75+ percent efficiency into loads with an SWR of 1.9. The PA can be operated with either CW or pulsed (FM-CW) signals.