Substrate Integrated Waveguide-to-Microstrip Transition in Multilayer Substrate

This paper presents a novel transition between a microstrip line and a substrate integrated waveguide (SIW) in a multilayer substrate design environment. In order to achieve a broadband response, a transition, consisting of a tapered ridged SIW and a tapered microstrip line, is modeled and designed by considering simultaneously both impedance matching and field matching. An effective bandwidth of 14.5% at 15 dB return loss is obtained. This transition provides a way to design substrate integrated circuits (SICs) with buried microstrip circuits in multilayer substrate, and any transform ratio can be anticipated in the design. A design guideline is also developed in this work.