A 240-GHz 4-transmitter (TX) 4-receiver (RX) 2-D multiple-input–multiple-output (MIMO) frequency-modulated continuous-wave (FMCW) radar transceiver was designed in a 130-nm SiGe bipolar CMOS (BiCMOS) technology with fT/fmax of 250/370 GHz using patch antennas on a single 4.032×4.032 mm2 chip. The differential RF inputs, located at the emitters of the direct conversion mixer quad transistors of each RX channel are dc-coupled and current-matched to the differential on-chip patch antenna. At 240 GHz, measurements reveal an RX conversion gain of 24.8 dB, a single-sideband noise figure of 14.9 dB, and an output power of −2 dBm.