A Novel Dual-Sheet-Beam Backward Wave Oscillator Based on Sub-Terahertz Band V-Shaped Orthogonal Grating Waveguide

A sub-terahertz band dual-sheet-beam backward wave oscillator (BWO) highlighted with wide tunable bandwidth and enhanced radiation power is presented in this letter. This design includes two key innovations: 1) a novel V-shaped orthogonal grating waveguide (VOGW) operating in TM
$_{{21}}^{\text {++}}$
high-order mode (++ represents the electric field vectors within two beam tunnel regions are in-phase) is proposed, which exhibits higher coupling impedance compared with the traditional OGW; 2) a novel E-plane L-bend overmoded coupler with a tapered transition is designed for efficient power extraction of the TM
$_{{21}}^{\text {++}}$
mode. For verification, an interaction circuit made of 40-period VOGW and two identical couplers was fabricated, and the measured results agreed well with simulation predictions having considered conduct loss and assembly errors. PIC simulation for this innovative BWO predicts a stable radiation power of 182.4-317.5 W across 246.8-265.6 GHz, demonstrating a power increment of up to 43 W (~15%) in comparison to the OGW based BWO.