Key result
A novel 2.4-GHz frequency-locked loop radar accurately measured respiration and heart rates during nonperiodic body movement, with standard deviations of 1.27 and 5.69 beats/min respectively while seated.
Why the study?
Most conventional vital-sign radars cannot easily detect human vital sign signals under nonperiodic body movement.
A novel 2.4-GHz FLL radar can accurately detect human respiration and heart rates even in the presence of nonperiodic body movements.
May enable motion-robust non-contact vital sign monitoring; leaves open clinical validation before practice adoption.
Most conventional vital-sign radars cannot easily detect human vital sign signals under nonperiodic body movement. This article presents a novel frequency-locked loop (FLL) radar that can track the phase changes that are caused by nonperiodic body movement. A gain/phase detector and a cross correlation function (CCF) in the FLL radar greatly reduce the second harmonic, the intermodulation terms between vital sign signals and nonperiodic body movement noise, enhancing both the signal-to-noise ratio and the accuracy of detection of the vital signs. Measurements indicated that the implemented 2.4-GHz FLL radar with a gain/phase detector and CCF can effectively detect the human respiration rate (RR) and heart rate (HR) under nonperiodic body movement. Using a chest belt as the measurement reference, the standard deviation (SD) of RR and HR measurements were 1.27 and 5.69 beats/min, respectively, when the seated subject under test (SUT) swung nonperiodically his upper body. When the SUT walked away from the radar naturally at 2.6 km/h, the implemented FLL radar measured RR and HR with SDs of 2.67 and 8.28 beats/min, respectively.
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Peng et al. (2021) studied this question. 2.4-GHz frequency-locked loop (FLL) radar vs. Chest belt was evaluated on Standard deviation (SD) of respiration rate (RR) and heart rate (HR) measurements. A novel 2.4-GHz frequency-locked loop radar accurately measured respiration and heart rates during nonperiodic body movement, with standard deviations of 1.27 and 5.69 beats/min respectively while seated.
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