Theoretical Design of Wideband 3-dB RWG Coupler

This letter introduces a design of wideband 3-dB ridge waveguide (RGW) coupler, theoretically addressing the issue of different odd- and even-mode cut-off frequencies, not mentioned before in the designs of traditional waveguide (WG) couplers. Accordingly, the working mechanism of the proposed RWG coupler is illustrated in detail based on the parameters’ reversion. The bandwidth (BW) of the coupler can be expanded effectively by optimizing the transition between the RWG and input/output stripline. For verification, the RWG coupler centered at 2.35 GHz is fabricated and measured, and the simulated and measured results with good agreement show the fractional BW (FBW) is more than 50%.