Example embodiments relate to substrate integrated waveguide (SIW) transitions. An example SIW may include a dielectric substrate having a top surface and a bottom surface and a first metallic layer portion coupled to the top surface of the dielectric substrate that includes a single-ended termination, an impedance transformer, and a metallic rectangular patch located within an open portion in the first metallic layer portion such that the open portion forms a non-conductive loop around the metallic rectangular patch. The SIW also includes a second metallic layer portion coupled to the bottom surface of the dielectric substrate and metallic via-holes electrically coupling the first metallic layer to the second metallic layer. The SIW may be implemented in a radar unit to couple antennas to a printed circuit board (PCB). In some examples, the SIW may be implemented with only a non-conductive opening that lacks the metallic rectangular patch.