Abstract
It has been proved that the vital signs can be detected via radar. To better identify the life parameters such as respiration and heartbeat, a novel method combined with several signal processing techniques is presented. Firstly, to improve the signal-to-noise ratio (SNR) of the life signals, the signal accumulation technique by FFT is used. Then, to restrain the interferences produced by moving objects, a dual filtering algorithm (DFA) which is able to remove the interferences by tracing the interfering spectral peaks is proposed. Finally, the wavelet transform is applied to separate the heartbeat from the respiration signal. The method cannot only help to automatically detect the existence of human beings effectively, but also identifying the parameters like respiration, heartbeat, and body-moving signals significantly. Experimental results demonstrated that the method is very promising in identifying the life parameters via radar.
Highlights
The life-detection system can be used to search living objects after the earthquake and building collapse, to monitor patients in clinic without contacting the subjects
If the spectral peaks of respiration signal and the interferences can be estimated by using the power-spectrum estimation (PSE) and coherence characteristics of the spectral peaks can be computed, the interference signals and the respiration signals will be identified after the first filtering
If the bandwidth of original signal detected by the system estimated by autoregression power-spectrum estimation (ARPSE) under the same condition as in Section 2.3 is [0, Ω], it can be divided into the lower halfband from 0 to Ω/2 and the higher half-band from Ω/2 to Ω for every wavelet decomposition scales
Summary
The life-detection system can be used to search living objects after the earthquake and building collapse, to monitor patients in clinic without contacting the subjects. The radar detector radiates electromagnetic waves to human subjects and receives echo waves modulated by the body surface jiggle caused by their physiological activities The life parameters such as respiration and heartbeat can be extracted according to the frequency or phased variations of the echo waves. Some methods for stationary signal processing, including FFT and high-order linear narrowband filtering [7] can improve the SNR They may be effective in good circumstances, but may not work in complex situations. To effectively resolve the problems described above, a new method was proposed, including improving the SNR of the life signals, restraining the interferences produced by moving objects, and separating the heartbeat from respiration signal. Experimental results demonstrated that the method integrating with the three signal processing techniques above is very promising in identifying the life parameters via radar
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