A Compact and Wideband MMIC-to-Ridge Gap Waveguide Contactless Transition for Phased Array Antenna Front Ends

A concept of a contactless in-line transition between a monolithic microwave integrated circuit (MMIC) and a ridge gap waveguide (RGW) is proposed and investigated at W-band. The transition employs an E-plane waveguide bifurcation obtained by mounting a GaAs MMIC on a supporting printed circuit board in the opening of an RGW top metal lid. Designed this way, multiple contactless transitions can be placed in a row with an electrically small spacing that makes the transition idea suitable for array antenna front ends. A transition equivalent circuit is constructed employing a single-mode transmission line model, which is verified through a full-wave simulation. An 85–105 GHz transition design is then developed and experimentally investigated in the back-to-back configuration indicating a 0.5–0.75 dB transition insertion loss. Finally, the performance of a 1-bit phase shifter MMIC, integrated into the RGW using two proposed transitions, is demonstrated.