Compact and Broadband Multi-aperture Coupler for Terahertz Sheet Beam Travelling Wave Tubes

In this paper, a compact and broadband directional multi-aperture waveguide coupler was initially designed for terahertz sheet beam travelling wave tubes. The proposed coupler is based on a series of identical apertures distributed between a pair of parallel rectangular waveguides. Simulation results predicted that the bandwidth for the coupling coefficient greater than −1 dB was 81.3 GHz (220.0-301.3 GHz), corresponding to a fractional bandwidth of 31.2%. Meanwhile, the reflection of all ports was lower than −15 dB, and the maximum isolation coefficient was below −15 dB.