A Wideband Differential Microstrip-to-Waveguide Transition for Multilayer PCBs at 120 GHz

A robust and wideband differential microstrip line-to-WR6-waveguide transition for mixed multilayer PCBs at D-band is presented. The PCB stack is composed of three standard RF core materials with standard thicknesses. Compared to other inline transitions above 90 GHz, which are designed for single substrates, it can be applied to mixed multilayer circuits. The tapered transition is only 8.0-mm wide and 2.5-mm long, has an insertion loss between 1.2 and 1.8 dB, and a return loss higher than 10 dB for 30-GHz bandwidth around the center frequency of 120 GHz.