Reconfigured Grating Structure With Frequency-Selective Characteristics for Higher Order Mode Suppression

To suppress the higher order mode (HOM) within terahertz (THz) traveling wave tubes (TWTs), a novel layout of slow wave structure (SWS) named reconfigured grating (RG) has been proposed in this article. Based on the staggered double grating (SDG), the RG achieves simultaneous frequency-selective and wave-absorbing characteristics by integrating two high-pass filter (HPF) functional layers and two absorbing layers alongside it. As signals pass through the RG, the fundamental mode (FM) is confined in the interaction circuit region to continuous interaction with the electrons. The HOMs are effectively filtered and absorbed. Beam-wave interaction results predict the enhancements in saturated power, electron efficiency, and effective HOMs suppression in the RG-TWT. Meanwhile, the fabrication feasibility and transmission characteristics of RG-SWSs were confirmed using high-precision computer numerical control (CNC) milling technology.