A New Method for Identifying the Life Parameters via Radar
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Research Article A New Method for Identifying the Life Parameters via Radar Wang Jianqi,1, 2 Zheng Chongxun,1 Lu Guohua,2 and Jing Xijing2 1 The
Key Laboratory of Education, Ministry of China, Xi’an Jiaotong University, Xi’an 710049, China of Biomedical Engineering, The Fourth Military Medical University, Xi’an 710032, China
2 Department
Received 10 January 2006; Revised 22 September 2006; Accepted 6 October 2006 Recommended by Ulrich Heute 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. Copyright © 2007 Wang Jianqi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1.
INTRODUCTION
The life-detection system can be used to search living objects after the earthquake and building collapse, also to monitor patients in clinic without contacting the subjects. In addition, it can be used by law-enforcement services to search criminals hiding behind various covers. The life detection based on radar techniques has been attracting more attention these years. The continuous-wave (CW) radar is widely used to detect the life parameters because of its simple structure and high sensitivity [1–5]. The frequency-modulated continuous-wave (FM-CW) radar is also used [6]. They can detect the life parameters of human noncontact, even behind the barrier such as the brick walls, debris, and clothes. 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. For all the life-detection systems via radar, it is difficult to detect the weak life signals from the strong echo waves of background. There exist two problems ineffectively resolved in common: how to improve the SNR and how to restrain the strong randomness, time variability and sensitivity to the interferences produced by the moving objects further
aggravate the situation, especially
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