This article presents frequency-modulated-continuous-wave (FMCW) radars developed for the detection of vital signs and gestures using two generations of 145-GHz transceivers (TRXs) integrated in 28-nm bulk CMOS. The performance and limitations of high-frequency radars are quantified with a system-level study, and the design and performance of individual circuit blocks are presented in detail. A 145-GHz center frequency and radar operation over an RF bandwidth of 10 GHz yield a displacement responsivity of 2 \textbackslash{}pi rad/mm and a windowed range resolution of 30 mm, respectively. Radar operation over a 0.1-7 m range is enabled by an effective-isotropic radiated power of 11.5 dBm and a noise figure of 8 dB. The ICs feature frequency multiplication by 9 in the transmit and receive paths, sub-arrayed dipole antennas, and neutralization of TX-RX leakage via delay control. A single TRX dissipates 500 mW from a 0.9-/1.8-V drive. The use of fast chirps (5-30- s) mitigates the effect of 1/f -noise at the intermediate frequency (IF). Extensive characterization results showcase state-of-the-art performance of the TRXs, while the code-domain multiple-input and multiple-output (MIMO) radars ( 1 * 4 and 4 * 4) built with them demonstrate vital-sign and gesture detections.