Simulation Design of G-Band FWG TWT Amplifier Enhanced by π-Mode Extended Interaction

This article studies and summarizes the operating characteristics of a ${G}$ -band folded waveguide traveling wave tube (TWT) amplifier enhanced by the $\pi $ -mode extended interaction cavities. Compared with conventional ${G}$ -band TWTs, the proposed amplifier can at once obtain a higher gain in a shorter interaction circuit length and ensure a proper operating bandwidth. The key of the design is introducing the $\pi $ -mode multigap resonant cavity with alternating wide and narrow slots, which will improve the working performance of the whole device by shortening the length of the interaction circuit, enhancing its interaction effect, and improving its gain of unit length. In this design, the operation bandwidth is expanded by stagger tuning technique. In addition, the influence of cavity loss is examined so that the optimal performance is achieved. The PIC simulation results show that when the operating voltage is 21 kV and the operating current 80 mA, the maximum average output power of the designed TWT amplifier is 65.78 W at 217.4 GHz, which is corresponding to the maximum gain and efficiency of 37.38 dB and 3.9%, respectively. The gain per unit length is 12.64 dB/cm and the 3-dB bandwidth is 3.5 GHz.