A waveguide to microstrip T-junction includes a microstrip transmission line structure having a ground plane separated from a strip conductor by a dielectric layer, the ground plane defining an aperture; a waveguide channel having a conductive periphery being electrically coupled to the ground plane...http://www.google.co.uk/patents/US20020097109?utm_source=gb-gplus-sharePatent US20020097109 - Waveguide to microstrip transition
