Bandwidth Comparison of Topside Waveguide-to-Microstrip Transitions with Back-Short Waveguide and with Double-Layer Substrate in Millimeter-Wave Band

Topside waveguide-to-microstrip transitions whose waveguide sits on the top of the substrate were developed in the millimeter-wave band. A substrate is attached on a back-short waveguide and the WR-10 waveguide is set on them. The microstrip line is inserted into the WR-10 waveguide, while the microstrip line is inserted into the backshort waveguide of the ordinary transition. A topside waveguide-to-microstrip transition with double layer substrate has been also developed. A coupling patch is located on the top surface with spacing of the upper substrate thickness from the microstrip signal line patterned between the upper and the lower substrates. The performance of the topside transitions with a back-short waveguide is compared with the transition with double layer substrate and the ordinary transition in this paper.