Analysis and Simulation of a Gigawatt-ClassKa-Band Radial Transit Time Oscillator

Abstract

Obtaining high power millimeter-wave output is a research hotspot of high power microwave (HPM) technology. Considering limited power capacity and mode competition in axial millimeter wave generators, the radial device is introduced to output high power millimeter waves. A gigawatt-class ${Ka}$ -band radial transit time oscillator (RTTO) is proposed in this paper. In guiding the magnetic field of 0.8 T, the radial TM01 mode is applied as the operation mode. Particle-in-cell (PIC) simulation demonstrates that when the diode voltage is 400 kV and the beam current is 7.5 kA, the HPMs at 31.2 GHz with an output power of 1.1 GW and a conversion efficiency of about 37% are generated. The maximum radial electric field is 1.2 MV/cm, proving that the radial structure is an effective way to enhance power capacity. 3-D PIC simulation proves there is no angular nonasymmetric mode intersection. Analysis of parameter sensitivity shows that, within a certain range, the thickness and axial position offset of the electron beam will not influence the performance of the RTTO. In addition, the oscillator can operate steadily as the radial guiding magnetic field changes from 0.6 to 6.0 T. With these characteristics, the RTTO is potential to output ${Ka}$ -band HPMs.