A Composite Staggered Double-Grating Structure for G-Band Dual-Beam TWT With High-Order Mode Operation

To suppress the fundamental mode competition and achieve stable high-order mode (HOM) amplification in staggered double-grating (SDG), a slow wave structure (SWS) named composite SDG (C-SDG) is proposed in this article. Based on the traditional SDG (T-SDG), C-SDG reconstructs the TE₁₀ mode electric field distribution by centering and longitudinally extending metal gratings along the broadside of the waveguide. Meanwhile, a hybrid-dispersion technique is employed to mitigate the energy accumulation of the TE₁₀ mode during beam–wave interaction, thereby enhancing device stability. The high-frequency characteristics and beam–wave interaction behavior are analyzed using CST Studio Suite. Particle-in-cell (PIC) results predict that the C-SDG traveling-wave tube (TWT) can achieve a maximum output power of 118 W and a gain of 20.7 dB at 220 GHz when driven by two sheet beams with an operating voltage of 21.4 kV, a beam current of 0.06-A per beam, and an input power of 1 W.