A novel quasi-optical millimeter-wave (MMW) monolithic monopulse receiver and its performance when integrated with a quasi-optical diplexer and antenna are described. Integration of the antenna, diplexer, and receiver forms a complete MMW radar front end. The receiver, which was fabricated on 0.025-in.-thick GaAs substrates, included four monolithic chips. The entire receiver was packaged on the planar back surface of a 1.5-in.-diameter lens. This lens, hyperhemispherical in shape, provided a dual function as a focusing lens and carrier for the monolithic receiver. The measured noise figure and conversion gain of the receiver were 8.7 dB and 19.0 dB, respectively, at 35.0 GHz.<<ETX>>