Simulation and Experimental Investigation on W-Band Back-to-Back Longitudinal Serpentine Groove Slow Wave Structures

This is the authors' abstract. We don't add key points for this paper.

Based on the traditional serpentine groove waveguide (SGW) slow wave structure (SWS), a novel back-to-back SGW (BTBSGW) is proposed in this article. The BTBSGW maintains the operational mode characteristics of conventional SGW while implementing dual-symmetric SGW that shares a common sheet beam, achieving two key improvements: 1) expanding the beam configuration and 2) simplifying the gun design. Through comprehensive high-frequency analysis, the dispersion characteristics, electric field distribution, coupling impedance, and transmission characteristics of the BTBSGW were investigated. Particle-in-cell (PIC) simulations were further conducted to evaluate the stability, saturation power, gain characteristics, and electronic efficiency of the BTBSGW traveling wave tube (TWT). Specifically, the BTBSGW-TWT is expected to achieve a gain exceeding 20 dB across the 86.5–92-GHz frequency band under fixed electron beam conditions (18.8 kV, 0.27 A). Peak performance occurs at 90 GHz, achieving a conversion efficiency of 5.97% and an output power of 302.06 W. To validate the design, the BTBSGW was fabricated using nano-computer numerical control (CNC) processing technology and the cold-test experiment was carried out. The experimental transmission characteristics exhibited a high degree of agreement with the simulation results. Overall, the BTBSGW-TWT demonstrates promising potential for applications in high-speed communication systems.