Detection of Human Vital Signs and Estimation of Direction of Arrival Using Multiple Doppler Radars

Abstract

This paper presents a non-contact measurement method of vital signal by the use of multiple-input multiple-output (MIMO) bio-radar system, configured with two antennas that are separated by a certain distance. The direction of arrival (DOA) estimation algorithm for coherent sources was applied to detect vital signals coming from different spatial angles. The proposed MIMO bio-radar system was composed of two identical transceivers sharing single VCO with a PLL. In order to verify the performance of the system, the DOA estimation experiment was completed with respect to the human target at angles varying between -50° and 50° where the bio-radar system was placed at distances (corresponding to 50 cm and 95 cm) in front of a human target. The proposed MIMO bio-radar system can successfully find the direction of a human target. Ⅰ. IntroductionRecently, remote sensing techniques have been actively studied as a means of measuring vital signs. Among these techniques, the Doppler radar sensing of vital signs has received substantial attention due to its simple system architecture and non-contact detection capability [1,2]. Various Doppler radar architectures for sensing human vital signs have consequently been developed: a Doppler radar system based on board-level and chip-level design [3], a dual-antenna Doppler radar system compensated for background motion [4], a barrier penetration consisted of ultra-wide band (UWB), and a CW Doppler radar [5] are some examples. MIMO signal processing methods, such as blind source separation (BSS) and analytical constant modulus algorithm (ACMA), have attracted a great deal of interest for non-contact vital sign detection [6,7]. Until recently, however, the existing MIMO techniques for vital sign detection have been mainly investigated to separate vital signs from multiple sources.The use of MIMO radar technique for vital signal sensing has a number of potential advantages. For a given system design choice, some of these advantages are enhancement of the target detection performance, improvement of the angle estimation accuracy, and a decrease in the minimum detection velocity [8]. A MIMO bio-radar system can also be combined with well-known direction of arrival (DOA) estimation algorithms to provide solutions for direction finding of human subjects. In the present paper, a new approach is presented to find the direction of human vital signals with two identical transceiver architectures sharing a single VCO with a PLL. The MIMO Doppler radar system can be effectively applied to find a human target with respect to azimuth angle, making it a good candidate for applications in home health care systems, military surveillance, as well as security services. To the best of authors' knowledge, this is the first successfully implemented direction finding system for human targets based on a MIMO radar concept. Ⅱ. MIMO Bio-Radar System ConfigurationThe configuration of the proposed integrated MIMO bioradar system is shown in Fig. 1. This monostatic MIMO radar consists of two antennas...

Vital sign detection for handheld communication device using antenna mismatching effect

“…Vital sign detector can be used for healthcare system and arrhythmia patient is one of the possible usages. In most cases continuous wave Doppler radars are studied and this type of sensors are shown to be accurate and reliable [1][2][3]. They can detect vital signs from 1 to 2 m distance.…”

RSSI-Based Living-Body Radar Using Single RF Front-End and Tunable Parasitic Antennas

“…Combining the signals received at all antenna elements yields a high detection rate. The second group aims to find the direction or location of the living-bodies [5], [7]. For detecting the location of a living-body, a key advance was the MIMO radar technique [8].…”

Heart Rate Detection During Sleep Using a Flexible RF Resonator and Injection-Locked PLL Sensor

“…According to previous studies, continuous wave Doppler radar operating in far field at 2.4 GHz or 10 GHz can detect heart rates at a distance of around 100 cm away from the chest [6][7][8][9]. However, the output signal of this system is significantly affected by motion artifacts: the reflected heart beat signal can be masked by random body movements due to the nature of the Doppler radar.…”