Three-Way Serpentine Slow Wave Structures With Stationary Inflection Point and Enhanced Interaction Impedance

We introduce two novel variants of the serpentine waveguide (SWG) slow wave structure (SWS), often utilized in millimeter-wave traveling-wave tubes (TWTs), with enhanced interaction impedance. Using dispersion engineering conjunction transfer matrix methods, we tune guided wavenumber relation to exhibit stationary inflection points (SIPs), and also nonstationary, or “tilted” (TIPs), within dominant TE10 mode a rectangular waveguide. The degeneracy is found below first upper band edge associated bandgap where neighboring spatial harmonics meet SWG which threaded by beam tunnel. geometries are optimized be able achieve an SIP allows for three-mode synchronism electron over specified interval desired Brillouin zone. Full-wave simulations used obtain verify existence three-way coupled fine-tune geometry such that would at near SIP. SWS exhibits moderately high Pierce impedance vicinity nearly TIP, making potentially useful improving power gain basic extraction efficiency TWTs. Additionally, introduced have directional coupler-like behavior, enables distributed frequencies frequency.