Broadband 55–95 GHz microstrip to waveguide transition based on a dielectric tip and a tapered double-ridged waveguide section

As applications in E-band (60–90 GHz) are gaining increasing commercial interest, a full-band, low-cost and high performance microstrip to rectangular waveguide standard (WR12) transition is desired. The presented design covers a bandwidth from 55 GHz to 95 GHz thanks to smooth impedance transitions. A dielectric tip is machined at the end of the microstrip line to couple with a double ridged waveguide section, which is then linearly tapered to a standard WR12 section. Measurements on back-to-back transitions confirm wideband operation beyond E-band with a 3.6 dB average insertion loss (1.8 dB per transition) and return loss lower than 10 dB in the 55 to 95 GHz frequency range. Additionally, group delay is measured showing broadband operation in line with the simulation.