Millimetre wave wideband low-loss waveguide-to-substrate integrated waveguide transition

A wideband Ka-band waveguide-to-substrate integrated waveguide transition is presented based on a multi-section transformer approach. We designed our transition by successfully adapting multi-section inhomogeneous waveguide transformer theory to match a substrate integrated waveguide feedline to a standard waveguide flange, which offers more degrees of freedom than current design methods in the state of the art. We subjected our transition to a simulated tolerance analysis and have found the transition to be robust when fabrication errors are considered. We validated these simulations by measuring a back-to-back waveguide-to-substrate integrated waveguide transition, where there is very good agreement between measured and simulated results. Moreover, an insertion loss of −0.48 dB was measured at the center frequency of the required operating range.