This paper presents a complete 2.5-V 77-GHz chipset for Doppler radar and imaging applications fabricated in SiGe HBT and SiGe BiCMOS technologies. The chipset includes a 123-mW single-chip receiver with 24-dB gain and an IP1dB of -21.7 dBm at 76-GHz local oscillator (LO) and 77-GHz RF, 4.8-dB double-sideband noise figure at 76-GHz LO and 1-GHz IF, and worst case -98.5 dBc/Hz phase noise at 1-MHz offset over the entire voltage-controlled oscillator tuning range at room temperature. Monolithic spiral inductors and transformers result in a receiver core area of 450 mum times 280 mum. For integration of an entire 77-GHz transceiver, a power amplifier with 19-dB gain, +14.5-dBm saturated output power, and 15.7% power-added efficiency is demonstrated. Frequency divider topologies for 2.5-V operation are investigated and measurement results show a 105-GHz static frequency divider consuming 75 mW, and a 107-GHz Miller divider consuming 33 mW. Measurements on all circuits confirm operation up to 100 deg C. Low-power low-noise design techniques for each circuit block are discussed.