Microstrip-to-waveguide transition using waveguide with large broad-wall in millimeter-wave band

Broad-wall connected microstrip-to-waveguide transition using a waveguide with large broad-walls is proposed. Maximum width of the waveguide where higher order mode dose not propagate is used. The dimension of the rectangular patch element is examined to have optimum width for wideband. Moreover, the distance from the edge of the broad-wall of the waveguide to via holes is also examined to have optimum length for wideband. A numerical investigation of a transition shows appropriate parameters. Proposed transition has insertion loss less than 0.28 dB from 77 GHz to 81 GHz, and a bandwidth of 18.2 % (14.4GHz) for reflection coefficient below −15 dB.