Particle-In-Cell Simulations of a Ka-Band Coupled-Cavity Traveling-Wave Tube

The particle-in-cell simulations of a Ka-band coupled-cavity traveling-wave tube (CCTWT) were performed to investigate the nonlinear interaction of the tube. The interaction circuit employs the double staggered ladder line coupled-cavity slow-wave structure. Combined with the design of well-matched high frequency coupling system, a 3-D circuit model based on CPI's Ka-band CCTWT was constructed. The particle-in-cell simulation results show that the tube can produce saturated average output power over 550 watts with greater than 600 MHz instantaneous bandwidth ranging from 28.3 GHz to 30 GHz when we adopt the similar parameters as CPI's Ka-band CCTWT, such as beam voltage, beam current and the slow-wave structure dispersion characteristics. The corresponding saturated gain and beam efficiency can reach over 33 dB and 8.39%, respectively. These results are in good agreement with the experimentally measured ones of the CPI's Ka-band CCTWT, which suggest that our design scheme is feasible and the CST PIC solver can accurately predict the performance of the CCTWT.