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This article presents a 24-GHz highly integrated phased array radar transceiver with four transmitters (TXs) and four receivers (RXs). To realize a wide field of view (FoV) and more efficiently reject the clutters, an automatic beam steering mode is realized. A beam scanning generator (BSG) and a frequency sweep generator (FSG) are proposed to steer the beam for each frequency-modulated continuous wave (FMCW) waveform sequence. The shape of the FMCW waveform, the number of beams, and the steering angles of beams can be reconfigured by initially setting the FSG and BSG. The TXs achieve an output power of 10.6 dBm and beam steering covering angles up to ±50° through a three-stage power amplifier (PA), a 6-bit phase shifter, and a 4-bit attenuator. The RXs achieve a noise figure (NF) of 13.5 dB and an overall gain of 105 dB. In the RXs, a two-stage low-noise amplifier (LNA) employs a low- ${k}$ transformer for flat band gain. A range-compensation filter with a total 40-dB slope is realized using a trans-impedance amplifier (TIA) with DC offset cancellation (DCOC) and first-stage biquad bandpass filter (BPF). The proposed transceiver was fabricated using 65-nm CMOS with an area of $3\times2.8$ mm2.

The remote vital signal detection using the Doppler radar is proposed to reduce the measurement errors caused by environmental factors, including the subject’s body movements. The proposed method for remote detection is based on the radar with beam control, which allows for adjusting the antenna’s radiating direction through spatial synthesis of an antenna array. By altering the beam direction, the proposed radar distinguishes between vital signals (respiration and heartbeat) originating from the asymmetrical movements of the human lungs and heart and the noise signals introduced by environmental factors, such as stationary clutters and the subject’s body movements. The respiration and heartbeat are extracted from the raw radar data obtained from each direction with signal processing techniques, including dc offset removal and random movement cancellation, which are based on the relationship of Bessel functions. An additional algorithm for extracting the correlated data from the acquired vital signals and filtering sudden variations significantly enhances the detection accuracy in the proposed method. In a practical test scenario, the vital signs of a subject walking at 2 km/h on a treadmill were measured in the surroundings with stationary clutters using the proposed method with a beam-switching 5.8-GHz radar module at a distance of 1 m. The measurement results demonstrated error rates of less than 3 beats per minute (bpm) for respiration and 4.2 bpm for heartbeat, compared with reference values obtained from contact-type sensors.

A mutual compensation range detection method using a multimodulation radar is proposed to detect the absolute distance of a target with high accuracy while using a narrow bandwidth. The waveform of the multimodulation radar consists of a combination of both a chirp of the frequency-modulated continuous wave (FMCW) radar and two-tone signals of the frequency-shift keying (FSK) radar for the precise mixing of the measured distances. The proposed mutual compensation range detection method can simultaneously solve the uncertainty by the phase offset and unambiguous range of the FSK radar and the limitation of the range resolution of the FMCW radar. Using the proposed method, the 5.8-GHz multimodulation radar with a bandwidth of 150 MHz detected the absolute distance of the target in the range of 2.1–5.1 m with a distance error of 2.1%. The distances between two persons located at 5 and 20 m were detected individually and distinguished when they crossed each other. The experimental results show that the proposed method using the multimodulation radar can solve the problem of unknown initial position caused by clutters and multipath interference in the surroundings, and the limited range resolution by the frequency bandwidth of the chirp.