Design of Ultra-Wideband Double-Ridge-Waveguide to Microstrip Transition Using E-plane Probe

This article proposes a design for microstrip transition to double-ridge waveguide (DRWG). To facilitate the transition of the electric field mode from DRWG to microstrip, an E-plane microstrip probe is utilized as a coupling component. Furthermore, stepped ridges are incorporated to widen the gap between the waveguide ridges, enabling the microstrip to be mounted on the vertical face of these ridges. Concurrently, the majority of the electric field propagating in the DRWG is truncated by the stepped ridges, while the electric field concentrated in the gap is coupled by the microstrip probe over an ultra-wideband range. high impedance and quarter-wave microstrip lines are employed to match the probe impedance to a 50O microstrip line. Through the implementation of this approach, a single transition is designed for WRD500 using full-wave 3-D electromagnetic field simulation and optimization. A back-to-back configuration of this transition is fabricated, with test results demonstrating an insertion loss below 0.8 dB and a return loss under 16.5 dB across a 113% relative bandwidth spanning from 5 to 18 GHz.