Review of Self-Injection-Locked Radar Systems for Noncontact Detection of Vital Signs

Wang, Fu-Kang; Wu, Chung-Tse Michael; Horng, Tzyy‐Sheng; Tseng, Chao‐Hsiung; Yu, Shiang-Hwua; Chang, Chia-Chan; Juan, Pin-Hsun; Yuan, Yifei

doi:10.1109/jerm.2020.2994821

Cited by 47 publications

(9 citation statements)

References 53 publications

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“…Traditional ways to monitor vital signs usually require hospitalization and involve body-attached instruments (e.g., PPG and ECG sensors), which are intrusive, costly, and require the cooperation of the person being monitored. To overcome these problems, research studies have been exploring contact-less vital sign monitoring via radio frequency (RF) signals [1]- [5]. Early studies used continuous-wave radar, or WiFi devices transmitting RF signals.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Monitoring of Multiple People’s Vital Sign Leveraging a Single Phased-MIMO Radar

Shi

Zhang

et al. 2022

IEEE J. Electromagn. RF Microw. Med. Biol.

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Vital sign monitoring plays a critical role in tracking the physiological state of people and enabling various healthrelated applications (e.g., recommending a change of lifestyle, examining the risk of diseases). Traditional approaches rely on hospitalization or body-attached instruments, which are costly and intrusive. However, in recent years there is an emergence of contactless vital sign monitoring techniques that rely on radio frequency signals. Early studies with continuous wave radars/WiFi devices have shown good success in detecting the vital signs of a single individual, while simultaneous monitoring of the vital signs of multiple, closely spaced subjects remains a challenge. In this paper, using an off-the-shelf Texas Instrument automotive FMCW radar, we design and implement a time-division multiplexing (TDM) phased-MIMO radar sensing system that allows high-precision vital sign monitoring of multiple subjects. The proposed sensing system can steer the beam towards the desired directions with a micro-second delay.The steerable beam enables capturing the vital signs of multiple individuals at the same radial distance to the radar. The proposed system enables the formation of a virtual array with aperture longer than that of the physical array. A Capon beamformer is used at the receiver side to combine the data collected from different transmit and receive antenna pairs corresponding to the virtual array. As all those pairs provide independent information about the targets, their combination significantly boosts the receiver signal-to-noise ratio. Based on the designed TDM phased-MIMO radar, we develop a system to automatically localize multiple human subjects and estimate their vital signs. Extensive evaluations show that under two-subject scenarios, our system can achieve more than 98.06% accuracy for breathing rate (BR) and more than 82.89% accuracy for heartbeat rate (HR) estimation, at a subject-to-radar distance of 1.6 m when the targets are facing the radar. The minimal subjectto-subject angle separation is 30 • at a subject-to-radar distance of 1.6 m, corresponding to a close distance of 0.3 m between two subjects, which outperforms the state-of-the-art.

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Section: Introductionmentioning

confidence: 99%

Simultaneous Monitoring of Multiple People’s Vital Sign Leveraging a Single Phased-MIMO Radar

Shi

Zhang

et al. 2022

IEEE J. Electromagn. RF Microw. Med. Biol.

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“…Infrared radiation energy is a kind of energy that can be obtained by a noncontact method, and it is closely related to the internal state of the measured object. As a result, infrared radiation analysis technology has been widely used in various fields requiring noncontact measurement, for example, vital signs monitoring, , power equipment damage monitoring, , celestial movement, medical diagnosis assistance, geological survey, etc. In the loading process of coal-rock, infrared radiation energy is a part of dissipated energy, and there is a certain coupling between them.…”

Section: Introductionmentioning

confidence: 99%

Coupling Mechanism of Dissipated Energy–Infrared Radiation Energy of the Deformation and Fracture of Composite Coal-Rock under Load

Yang

et al. 2022

ACS Omega

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The fracture of composite coal-rock under load is the process of energy conversion. As the dissipative energy composition, there is a correlation between the infrared radiation energy and the coal-rock states. Based on theories of theoretical mechanics, modern quantum mechanics, thermodynamics, and other disciplines, first, this paper explained the causes of infrared radiation energy in the process of coal-rock fracture by using the microanalysis method. After that, the mathematical model of dissipation energy−infrared radiation energy coupling was deduced and established, and the experimental analysis was carried out under different loading conditions. The analysis shows that the conversion of mechanical energy and internal energy in the process of loading caused constant collisions between molecules in coal-rock, which led to a temperature rise. After entering the excited state, molecules have to transition to a lower energy level, which generates infrared radiation. The experimental results show that there was a strong correlation between energy characteristic parameters, which is consistent with the established relationship. In addition, the energy conversion and dissipated energy changes in the loading process had stages. Before the elastic−plastic stage, the dissipated energy obtained by coal-rock energy conversion was less, but it increased rapidly in the later stage, which eventually led to the fracture of coal-rock. In the early elastic−plastic period, infrared radiation energy was the main component of the dissipated energy and its variation trend was consistent with the dissipated energy. After that, the infrared radiation energy remained stable, but the dissipation energy still increased. At this time, infrared radiant energy was no longer the main component of dissipated energy. And the infrared radiation energy dropped rapidly before coal-rock fracture, which had certain precursory characteristics. The coupling mechanism of dissipated energy−infrared radiation energy can be used to explain the failure reason of composite coal-rock under different loading conditions from the perspective of energy, which will provide a new idea for assisting the prediction of coal-rock dynamic disasters.

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“…This paper reviews some of the progresses made since 2013 with frequency-conversion based continuous-wave (CW) radar architectures. Due to page limit and research area of the authors, the paper does not cover impulse-radio ultrawideband (IR-UWB) [12] and injection-locked detection architectures [13], although they also have unique advantages for sensing of life activities. The rest of the paper will start from new front-end technologies.…”

Section: Introductionmentioning

confidence: 99%

Sensing of Life Activities at the Human-Microwave Frontier

Lubecke

Borić–Lubecke

et al. 2021

IEEE J. Microw.

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Review of Self-Injection-Locked Radar Systems for Noncontact Detection of Vital Signs

Cited by 47 publications

References 53 publications

Simultaneous Monitoring of Multiple People’s Vital Sign Leveraging a Single Phased-MIMO Radar

Simultaneous Monitoring of Multiple People’s Vital Sign Leveraging a Single Phased-MIMO Radar

Coupling Mechanism of Dissipated Energy–Infrared Radiation Energy of the Deformation and Fracture of Composite Coal-Rock under Load

Sensing of Life Activities at the Human-Microwave Frontier

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