Printed-Probe Hybrid Coupler for the 3-mm Band

A printed-circuit, 7-element, 3-dB hybrid coupler has been developed for application to low - cost systems operating in the 3-mm atmospheric window. Based on a computer-aided analysis, a prototype coupler has been constructed and tested. Across a 3.7-GHz band centered at 94 GHz, the measured isolation is 22 dB or better, and the coupling is 3.4±0.9 dB. Such a coupler can be integrated with other planar circuits to form a variety of components useful in advanced high-resolution systems.