Vital Signal Detection Using Multi-Radar for Reductions in Body Movement Effects

Figures

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  Figure 1. Asymmetrical movements of human organs: (a) pumping and filling of blood in the heart; (b) expansion and contraction in the lungs [25,26].

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  Figure 2. Preceding experiment showing that the respiration and heartbeat signals obtained from the radar can be different depending on the direction of the line-of-sight to the subject.

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  Figure 3. Frequency spectrum of the vital signals simultaneously measured from the two radars placed in front of and behind the subject.

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  Figure 4. Proposed radar configuration using multiple radars based on the asymmetrical movement of human organs.

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  Figure 5. Digital signal processing using the proposed correlation technique for reducing the effect of human body movement.

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  Figure 6. Normalized spectrum of baseband signals in the simulation.

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  Figure 7. Simulated spectrum of the conventional and proposed signal processing methods.

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  Figure 8. Signal-to-noise ratios of the conventional and proposed signal processing methods depending on the difference in the operating frequency of the two radars: the signal is the magnitude of the vital signs and the noise is the magnitude of the signal caused by the human body movement: (a) for respiration; (b) for heartbeat.

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  Figure 9. Implemented single-channel radar module in the 5.8 GHz ISM band.

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  Figure 10. Experiment environment of the proposed radar configuration for vital signal detection for canceling the effect of body movement.

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  Figure 11. Frequency spectra of the vital signals measured by using the reference sensors (a respiration belt and an ECG sensor) and the proposed radar configuration at the LOS angle of 30°.

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  Figure 12. Measurement results using the proposed radar configuration in the experiment with a measurement angle of 30°: (a) normalized spectrum obtained in the motionless condition; (b) spectrum displayed with the absolute amplitudes of signals in the motionless condition; (c) normalized spectrum obtained in the presence of human body movement; and (d) spectrum displayed with the absolute amplitudes of the signals in the presence of human body movement.