Demonstration of a frequency-selective filter for restraining high frequency oscillation in Ka-band sheet beam TWTs

The problem of oscillation suppression is the key to ensuring the normal operation of the traveling wave tubes (TWTs). In this paper, design of a frequency-selective filter for restraining high frequency oscillation in Ka-band sheet beam traveling-wave tubes is presented. Two design methods are used to extract and radiate the microwave on oscillation frequency, while avoiding the influence on the operating frequency. One is combination of multi-section gradual matching and pyramidal horn antenna, and the other is combination of multi-section gradual matching and Ka standard matched load. The simulation results of both methods show return loss (S
11
) is more than 20 dB over 26 GHz -– 40 GHz, and insertion loss (S
21
) is less than 10 dB over 35 GHz -– 38 GHz.