Investigations of the Recirculating Planar Crossed-Field Amplifier

Crossed-Field Amplifiers are widely used, broadband (>10% bandwidth) RF amplifiers that can achieve output powers of several megawatts. The Recirculating Planar Crossed-Field Amplifier (RPCFA) was initially designed by Exelby at the University of Michigan. 1 With a high-power (>150-kW) input signal operating at 3.05 GHz, the RPCFA had a measured gain of 8.7 dB and 10% bandwidth with up to 5-6 MW output power 1 . In recent experiments coupling the input to the output of the RPCFA directly with waveguide, a feedback loop was achieved, and oscillations were observed. The highest peak powers measured during the feedback-oscillation of the RPCFA were between 10-30 kW. These oscillations were observed late in the pulse. Oscillations were suppressed when attenuation was added into the feedback loop. 2 The delay-time between the measured microwave power peaks is being investigated when the feedback loop length is increased.