A broadband waveguide to microstrip-line transition on multi-layered LCP substrate

In this paper, a broadband waveguide WR-15 to microstrip-line (MSL) transition is proposed. The transition is structured on a multi-layered liquid crystal polymer (LCP) substrate. The substrate has two LCP layers and a metal back-short block is mounted on the substrate and is connected to ground plane. The WR-15 waveguide is directly connected to the substrate and is coupled with the MSL via rectangular apertures formed in the substrate. Small patches are put inside the apertures for enhancing the suppression of reflection. As a result, better mode transition is obtained if compared with one without the patches. A bandwidth of 16% (55-65 GHz) in which |S
₁₁
|<; -10 dB is obtained in measurement.