A folded-slot quasi-optical planar balanced mixer

A folded-slot quasi-optical mixer is presented. The simple uniplanar mixer uses orthogonal modes in a folded-slot antenna to achieve intrinsic RF/LO isolation, eliminating the need for RF filtering or subharmonic pumping. A folded-slot mixer was fabricated on RT/Duriod, and a Friis transmission experiment was used to measure a minimum isotropic conversion loss of 1.2 dB at 11.6 GHz. An antenna directivity of approximately 7 dB was obtained by numerical integration of full two-dimensional antenna patterns, and this corresponds to a mixer conversion loss of 8.2 dB. The mixer also demonstrated -18 dB RF/IF isolation and -30 dB LO/IF isolation.