A Mode Perturbation Scheme for Suppressing Upper Sideband Oscillations of Sheet Beam Traveling Wave Tubes

The problem of sideband oscillation has been a persistent challenge in the development of power and bandwidth for traveling wave tubes, particularly for high-power sheet beam traveling wave tubes (SB-TWTs). In this paper, a method of mode perturbation is proposed to suppress oscillation by interfering with the interaction field. To address this issue, a modified structure is designed, which differs from the traditional double staggered vanes slow-wave structure (SDV-SWS). The modified structure enables the high-frequency cut-off mode to couple a stronger transverse electric field component, replacing the original longitudinal component, thus avoiding the problem of upper sideband oscillation and freeing up bandwidth.