Abstract
Respiration and heartbeat are basic indicators of the physiological state of human beings. Frequency-modulated continuous wave (FMCW) radar can sense micro-displacement in the human body surface without contact, and is used for vital-sign (respiration and heartbeat) monitoring. For the extraction of vital-sign, it is essential to select the target range containing vital-sign information. In this paper, we exploit the coherency of phase in different range-bins of FMCW radar to effectively select the range-bins that contain accurate signals for remote monitoring of human respiration and heartbeat. To quantify coherency, the spatial phase coherency (SPC) index is introduced. The experimental results show that the SPC can select a range-bin containing more accurate vital-sign signals than conventional methods. This result demonstrates that the proposed method is accurate for monitoring of vital signs by using FMCW radar.
Highlights
Spatial Phase Coherency of frequency-modulated continuous wave (FMCW)Respiration and heartbeat can provide the basic physiological state of human beings, and can be used as healthcare indicators or in clinical diagnosis [1,2,3,4,5,6]
Information pertaining to respiration and heartbeat exists in specific range-bins, such as range-bins near the abdomen or thorax for respiration [39,42], and range-bins near the neck for heartbeat [43], so the range-bin that includes the vital signs (VSs) must be selected precisely
Considering the FMCW radar is widely used for multi-target monitoring because of its ranging capability, the proposed spatial phase coherency (SPC) needs to be expanded to multi-target VS monitoring
Summary
Spatial Phase Coherency of FMCWRespiration and heartbeat can provide the basic physiological state of human beings, and can be used as healthcare indicators or in clinical diagnosis [1,2,3,4,5,6]. Traditional monitoring sensors that are attached to the body can cause discomfort and restrict behavior. Radar can detect micro-displacement in the human body surface without contact [13,14,15], and this ability has been exploited for contactless monitoring of vital signs (VSs). Radar can monitor VSs continuously, and without contact, so the monitoring system has been applied in various applications such as medical care surveillance for severe burns or infectious diseases [16,17], driver assistance [18,19], sleep monitoring for sudden infant death syndrome, apnea detection [20,21,22], and homecare for the elderly [23,24,25]. Frequency-modulated continuous wave (FMCW) radar, which has ranging capability, can spatially separate VSs from clutters [26,27]. FMCW radar uses a millimeterwave band, and has the advantages of small sizes and low power consumption
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