Abstract: A monolithic high frequency downconverter which utilizes a three-stage low-noise amplifier, a singly balanced mixer, and a two-stage intermediate frequency amplifier. The downconverter is suitable for applications in a range of systems utilizing EHF frequencies, such as satellites, or phased array antennas. Other applications include RF front end of smart weapons operating at frequencies ranging from 35 to 94 GHz, and avionic systems employing channelized receivers and EW (electronic warfare) systems. The three-stage low-noise amplifier employs four-gate finger HEMT devices for reduced gate resistance and source impedance matching. The singly balanced active HEMT mixer employs a compact 180.sub.-- rat-race hybrid ring which significantly reduces the chip size and provides low conversion loss, high LO to RF isolation, high output, IP.sub.3 and high-spur rejection as compared to single-ended mixer designs.