Third harmonic frequency multiplication of a two-stage tapered gyro-TWT amplifier

The third harmonic frequency multiplication is experimentally verified using a two-stage tapered gyrotron traveling-wave tube amplifier in low-power operation. The third harmonic frequency multiplication is predicted and investigated using a self-consistent large-signal theory and a particle-in-cell code simulation. Both results show a good agreement in frequency multiplication and power amplification. The interaction between a 30 kV axis-encircling electron beam with a drive signal in the tapered waveguide of the input stage modulates the electron beam at the fundamental cyclotron harmonic, then the third harmonic component of the modulated beam current is chosen to be extracted in the tapered output stage. In the proof-of-principle experiment, X-band drive signals from 10.6 to 12 GHz are multiplied by three times to be Ka-band output frequencies from 31.8 to 36 GHz, showing consistent results with theoretical predictions when a 30 kV, 160 mA electron beam is used.