Wideband transition between rectangular waveguide and microstrip using asymmetric fin line probe

A novel wideband waveguide-to-microstrip transition realised by inserting asymmetric fin line probe into metallic rectangular waveguide is presented. One back-to-back transition covering the Ka band is designed, fabricated and tested to show the advantages of such asymmetric fin line-probe inspired transition structure, and measured results consist well with simulations. An insertion loss less than 0.8 dB and a return loss better than 15 dB over 24-40 GHz are obtained for the back-to-back structure. This broadband fin line-probe transition between rectangular waveguide and microstrip can be used widely in microwave and millimetre-wave circuit and system.