Novel Integration Techniques for Gap Waveguides and MMICs Suitable for Multilayer Waveguide Applications

This article discusses three integration and packaging techniques for gap waveguides and monolithic microwave integrated circuits (MMICs) suitable for multilayer waveguide applications. Two vertical transitions between microstrips and ridge gap waveguides (RGWs) are presented. The first vertical transition connects RGW to a microstrip line from the top where a rectangular patch has been used. Measured results of the transition in a back-to-back structure show that the reflection coefficient is better than −10 dB from 75 to 83 GHz, and the insertion loss for a single transition over the frequency band is 0.65–0.85 dB. The second vertical transition connects RGW to a microstrip line from the back by a slot in the ground plane. Measured results of the transition in a back-to-back structure show that the reflection coefficient is better than −10 dB from 69 to 86 GHz, and the insertion loss for a single transition is 0.65–1 dB over the frequency band. Commercially available E-band MMIC amplifiers are integrated with RGWs using the two proposed transitions. Moreover, for the very first time, the integration of MMIC with inverted microstrip gap waveguide (IMGW) is realized by a compact packaging structure that utilizes bond wires and capacitive pads. All the three active integrations are consistent with the passive measurements in terms of operational bandwidth, losses, amplifier gain flatness, and unwanted resonance suppression.