Abstract
This study proposes a mode-selective circuit to suppress the competing modes in a TE 01 gyrotron backward-wave oscillator (gyro-BWO). The circuit, also functioning as an interaction structure, comprises of several transverse slices. It eliminates the restrictions of the mode-competitions and allows a longer interaction structure to optimize interacting efficiency. Mode-selective effect will be analyzed. Experimental results indicate that the Ka-band TE 01 fundamental harmonic gyro-BWO is capable of continuous tuning from 31.4 GHz to 36.4 GHz with a peak efficiency of 23.7% corresponding to 100 kW at I b = 4.5 A and V b = 93.6 kV. © 2009 IEEE.