A Miniature 200-GHz Subharmonic Mixer With a Folded 180 degrees Hybrid Using Equal-Length Edge- and Broadside-Coupled Lines

Abstract

A miniature 180 degrees hybrid is proposed to demonstrate a 200-GHz subharmonic mixer (SHM) using a 0.18-mu m SiGe BiCMOS process. The reduced-size 180 degrees hybrid is achieved by folding the shared coupled lines between the in-phase power divider and the out-of-phase Marchand balun. The shared coupled lines demand an equal length design for the coupled lines at both Delta and Sigma ports of an 180 degrees hybrid. For the SHM, edge coupling for the Sigma section and broad-side coupling for the Delta section are employed to compensate the different input frequencies at Delta and Sigma ports. The SHM achieves a conversion gain around -21 dB from 175 to 200 GHz with 0-dBm LO pumping power. The LO-to-RF isolation is better than 32 dB within the operating bandwidth.