A 170-GHz fully integrated single-chip heterodyne frequency modulated continuous-wave (FMCW) imaging radar using a 130-nm SiGe BiCMOS technology (f_T/f_max = 220/280 GHz) is reported. This system demonstrates a wide bandwidth of 27.5 GHz (16.3%) at a center frequency of 168 GHz. A design methodology to maximize the tuning range of the voltage-controlled oscillator (VCO) is presented. A co-design of the VCO, coupler, and antenna is performed to minimize the chip area and the dc power consumption. The transmitter radiates a peak power of -1 dBm with a dc-to-RF efficiency of 1.42%. At the receiver side, a subharmonic mixer is used for signal downconversion. The system achieves a measured sensitivity of 87 fW with a total dc power consumption of 67 mW. The prototype is capable of forming 2-D and 3-D images with a range resolution of 7 mm. To the best of our knowledge, this fully integrated imaging radar demonstrates the highest sensitivity and radiation efficiency among all imaging systems around 200 GHz. Moreover, the system is capable of practical 2-D and 3-D imaging with significantly lower dc power consumption compared to the state-of-the-art FMCW radars.