On the design of waveguide-to-microstrip and waveguide-to-coplanar line transitions

New versions of the waveguide-to-microstrip and waveguide-to-coplanar line transitions are described and analyzed. The transitions differ from the standard ones by a probe in the shape of a rectangular patch. The structure is very simple, easily adjustable, it has a broad bandwidth, and there is no need to use an impedance transformer. These transitions have been analyzed by the method of minimal autonomous blocks and the integral equation method. The results obtained were compared with experimental data. An optimized structure has been designed by a simple optimization process using the integral equation method. Its transition band is flat with return losses better than -15dB nearly in the whole X-band.