Design and Fabrication of S-Band GaN SSPA for a Radar

In this paper, a design and fabrication of GaN power amplifier for the S-band frequency (400 MHz bandwidth) are presented. A combining path using /4 transmission line is implemented for GaN pallet amp. Both the combiner with suspended-type transmission structure for low-loss and the suspended stripline coupler with aperture coupling for auto gain control are realized for achieving high-power high-efficiency amplifier. Proposed power amplifier demonstrated a 5 kW peak output power, 27.8 % efficiency, 67 dB gain without ALC and a 4 kW peak output power, 25.5 % efficiency, 0.1 dB droop at 200 usec pulse width and 10 % duty with ALC.