Investigation on a high-power V-band transit-time oscillator under a low guiding magnetic field with a focusing cathode

Abstract

Low guiding magnetic fields are favored for high-power microwave sources in practical applications for the sake of compactness and miniaturization, especially for permanent magnet packaging to replace the bulky and heavy solenoid system. A novel focusing cathode is proposed in a V-band transit-time oscillator to reduce the requirement for guiding magnetic fields. Particle-in-cell simulation results indicate that in the diode region, the radial electric field and electron beam current are reduced with the focusing cathode, further leading to improved transmission of the electron beam under a low guiding magnetic field. With an input of diode voltage of 393 kV, a beam current of 5.25 kA, and a low guiding magnetic field of 0.6 T, the transit-time oscillator outputs a microwave with an average power of 566 MW and a frequency of 58.6 GHz, resulting in a conversion efficiency of 27.3%. The proposed V-band transit-time oscillator with a focusing cathode can also stably work under a large range of input voltage and magnetic field, desired for further research with permanent magnet packaging.