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.