An FMCW Radar for Localization and Vital Signs Measurement for Different Chest Orientations

Abstract

This work tests the ability of a frequency-modulated continuous wave (FMCW) radar to measure the respiratory rate and the heartbeat of a subject in challenging indoor scenarios. To simulate a realistic configuration for ambient assisted living (AAL) applications, in which the thorax orientation towards the antenna is typically unknown, four different scenarios were considered. Measurements were performed on five volunteers positioned with the chest, left, back, and right side facing the antenna, respectively. The 5.8 GHz radar and the antennas used for the measurements were suitably designed for the considered application. To obtain a low cost and compact system, series-fed arrays were preferred over other antenna topologies. The geometry of the patches was opportunely shaped to reduce the side lobe level (SLL) and increase the bandwidth, thus ensuring good system performances. In all scenarios, the vital signs extracted from the radar signal were compared with the ones collected by a photoplethysmograph and a respiratory belt, used as references. A statistical analysis of the measured data on the different subjects and orientations was performed, showing that the radar was able to measure with high accuracy both the respiratory rate and the heartbeat in all considered configurations.

Wearable Belt With Built-In Textile Electrodes for Cardio—Respiratory Monitoring

“…By using the electromagnetic radiation in the microwave region, it is possible to monitor cardio-respiratory activity without any contact with the subject under examination and, consequently, to carry out non-invasive monitoring. The systems proposed in the literature for the remote monitoring of breath activity are mainly based on Doppler [6,7], ultra wideband (UWB) [8,9] and FMCW radar techniques [10,11]. Their major advantage is that, without the need for any cable or electrode, it is possible to locate the patient inside the room, and then, to measure his/her respiratory rate and heartbeat.…”

An Inclusive Survey of Contactless Wireless Sensing: A Technology Used for Remotely Monitoring Vital Signs Has the Potential to Combating COVID-19

“…2) Power consumption: FMCW radar systems are able to provide fine range and Doppler information, nevertheless, the power consumption of these system is high [12]. 3) Orientation: Since the FMCW-based system sends a continues signal in a given direction, the orientation of the subject is a factor where for example if the chest is being observed for respiratory monitoring some critical signals may be missed if the patient's thorax is not facing the antenna because the signal is weak [34]. 4) Accuracy: Accuracy is one of the most important attribute for a vital signs monitoring system in an AAL environment for instance.…”

“…Third WiGait estimates the gait velocity and stride length using stable phase based on time series. FIGURE 32: WiGait sensor system [33] 10) Author in [34] utilized FMCW-based radar system to monitor the respiratory rate and the heartbeat of a patient in a challenging indoor environment in order to simulate ambient assisted living (AAL) conditions. The authors considered four different scenarios where the patient's chest, left, right, and back side were facing the antennas.…”

“…This study has also shown that contantless sensors have great potential to revolutionise human vital sign detection and monitoring. The study has demonstrated that contactless sensing technology can be used to limit contact between patients, [37] Surgery recovery (endometriosis) FMCW Not specified [38] Head position FMCW Not specified BodyCompass [41] Sleep position FMCW 5.4 GHz -7.2 GHz Emirald [39] Pacing FMCW Not specified [42] PD FMCW Not specified [40] Human Figure FMCW 5.46 -7.24 [34] Respiratory rate and heartbeat FMCW 5.8 [35] Respiration rate FMCW 5.8 [17] Human activity (sitting standing) CSI 2.4…”

Experimental Comparison of IR-UWB Radar and FMCW Radar for Vital Signs

“…FMCW radar overcomes the drawbacks of continuous-wave (CW) radar, with capabilities to measure range and velocity, which has also been studied in measuring noncontact vital signs [ 21 , 22 ] as well as counting people and recognizing hand gestures. Since it transmits linear FM signals, it can transmit relatively high power to achieve a high SNR.…”