A broadband transition between substrate integrated waveguide (SIW) and rectangular waveguide (RWG) is proposed. Five ridged steps in the RWG and a multi-section SIW are designed to expand the bandwidth. The measured results agree well with the simulations, a return loss better than 15 dB and an insertion loss less than 2.45 dB are obtained at the wide band from 23.83 GHz to 40 GHz for a back-to-back structure.
