AbstractTwo novel quasioptical mixers using patch antennas and compact local oscillator (LO) ports are described: a fundamentally pumped mixer with a waveguide LO and a subharmonically pumped mixer with a planar LO. The angular dependence of the antenna patterns, the isotropic conversion loss, and the mixer noise figure are presented. A 7.5‐dB noise figure has been measured at 35 GHz for the subharmonically pumped design. The importance of the effective antenna temperature and its effect on the mixer noise figure are discusse