High-Efficiency Substrate-Less Transition Technology From Waveguide to Chip for mm-Wave Active Modules

Journal article, 2025

This article presents a substrate-less transition technique for direct integration of rectangular waveguides (RWs) with monolithic microwave integrated circuits (MMICs) in the W band. The proposed transition employs a ridge waveguide (RWG) structure to allow low-loss interconnection between RW and chip, facilitating single-process fabrication via computer numerical control (CNC) machining, thus minimizing the dielectric and assembly losses. A trapezoidal metal probe, acting as a TE-to-quasi-TEM mode converter, interfaces with the chip through the standard gold wire bonding. Two prototypes validate the design: Prototype-I, using a passive quartz substrate, achieves an insertion loss below 0.86 dB from 75 to 110 GHz; Prototype-II, integrating a commercial power amplifier (PA) MMIC, exhibits an output power deviation of only 0.5 dBm from datasheet specifications across 96–104 GHz, confirming the transition’s high efficiency. The results demonstrate a broadband, low-loss, and repeatable packaging solution for W-band front-end systems.