Beam–Wave Resynchronization Method of the Nonperiodic Meander Line and Folded-Waveguide SWS for TWTs

A beam–wave resynchronization (BWRS) method is proposed by changing the structural parameters of the nonperiodic (NP) slow wave structure (SWS) to reduce the phase velocity of the wave for traveling-wave tubes (TWT) application. The mathematical model and analysis for the BWRS method are introduced to investigate what condition the NP meander line SWS (ML-SWS) and the NP folded-waveguide SWS (FW-SWS) should satisfy so that the corresponding TWT can have a good output performance. As the applications, the NP zigzag ML-SWS and the concentric arc FW-SWS are designed according to the method, which is also compared with that designed according to the phase velocity synchronization (PVS). The simulated results show that, by using the BWRS method, the max output power (efficiency) of the zigzag ML-SWS TWT can be improved from 56.7 (18.9%) to 76.26 W (25.4%), and the bandwidth can be expanded from 6 to 10 GHz in the Ka-band. Furthermore, the max output power (efficiency) of the concentric arc FW-SWS TWT can be improved from 199 (27.6%) to 237 W (32.9%), and the bandwidth can be expanded more than twice in the W-band as before. These results indicate that the BWRS method is beneficial for the improvement of the output power and electron efficiency and may be beneficial for wider bandwidth.