An Ultra-Wideband Microstrip-to-WR15 Waveguide Transition for MMIC Applications

A Microstrip-to-WR15 Waveguide from 50GHz to 75 GHz is proposed. It is based on a metal enclosure and a double-layer PCB. The PCB contains a Klopfenstein-Taper as the first transition between the microstrip and a Substrate Integrated Wave (SIW) with optimized matching. A coupling aperture on the bottom side of the PCB acts as the second transition from the SIW to the waveguide. For matching the coupling aperture to the WR15 waveguide, a three-stepped-impedance converter is milled into the metal enclosure. The measured reflection coefficient is below −10 dB, and the measured transmission is better than −2.5 dB in the entire band. The advantages are easy manufacturing, tolerance insensitivity, and ultra-high bandwidth. Thus, it offers a wide range of applications for mm-Wave sensors.