High-Order Mode Suppression in Traveling Wave Tube Based on Conformally Loaded Metasurface Filter

In order to address the high-order mode (HOM) oscillation that may affect the stability of traveling wave tubes (TWTs), a new strategy called conformally loaded metasurface filter (MF) has been proposed. By loading MF into the waveguide type slow wave structure (SWS), the frequency-selective transmission properties of MF can confine the operating mode in the SWS, while the nonoperating modes are transmitted out. Therefore, the amplitude of HOMs is limited, even if synchronization conditions are met, thereby, the risk of HOM oscillation is reduced. Taking the staggered double grating slow wave structure (SDG-SWS) as an example, the effectiveness of the strategy was verified. In addition, MF is easy to manufacture, which makes it have promising applications in high-power and high-frequency THz amplifiers.