The HMC331 is a passive miniature frequency doubler MMIC. Suppression of undesired fundamental and higher order harmonics is 50 dB typical with respect to input signal level. The doubler utilizes the same GaAs Schottky diode/balun technology found in Hittite MMIC mixers. It features small size, requires no DC bias, and adds no measurable additive phase noise onto the multiplied signal.