Analysis of the Influence of Insertion Loss on Phase Tuning to Improve Output Power

With the increase of frequency, the nonnegligible insertion loss becomes one of the important factors affecting the performance of the traveling wave tube (TWT). The phase tuning method has been proven to be a simple way to improve the output power. For 0.65 THz TWT, the improvement of output power by phase tuning with perfect electrical conductor (PEC) or lossy metal shells is studied. The influence of different phase tuning values at different positions on the output power can be quickly obtained by the program. When insertion loss is present, the tuning position range that can enhance the output power is narrower and situated closer to the output port. PIC simulations were performed to further analyze the impact of losses on phase tuning. Loss reduces the effect of phase tuning on increasing output power by affecting the bunching of the electron beam.