The HMC294 chip is a miniature passive GaAs MMIC double-balanced mixer which can be used as an upconverter or downconverter from 25 - 40 GHz in a small chip area of 1.70 mm2. Excellent isolations are provided by on-chip baluns, which require no external components and no DC bias. All data is measured with the chip in a 50 ohm test fixture connected via 0.076 mm (3 mil) gold ribbon of minimal length <0.31 mm (<12 mils).