Remote Vital Sign Monitoring With IMU-Assisted Handheld IR-UWB Radar Sensor

Abstract

Radar-based remote vital sign sensing and measurement has recently gained substantial attention due to its noncontact and noninvasive nature. Currently, a considerable amount of research is being carried out to measure human vital signs under the influence of random body movements. However, previous studies consider radar sensors to be fixed and stationary. Handheld radar-based vital sign measurement can significantly expand the practical usefulness of radar in healthcare, and search and rescue applications. This article presents a novel handheld vital sign measurement system using impulse-radio ultrawideband (IR-UWB) radar equipped with inertial measurement unit (IMU) sensor. The movements caused by holding the radar while performing measurements are recorded using an IMU sensor, and their effects on the radar range point are evaluated to perform range calibration. A controlled preliminary experiment was conducted using a static wall target, demonstrating that IMU-based calibration significantly reduces spectral noise induced by handheld vibrations. The iterative method continuously observes two consecutive radar frames to track the hand movement and the movement higher than the radar range resolution is compensated accordingly. The results suggest that by applying range calibration using an IMU sensor, the handheld radar can effectively measure human vital signs with a mean absolute error (MAE) of 2.01 breaths per minute (BrPM) for the breathing rate (BR) and 2.72 beats per minute (BPM) for heart rate (HR). Contrary to that, without range calibration, handheld radars are unable to extract vital signs. Correlation analysis between radar and reference sensor was also performed before and after calibration, which further confirmed the effectiveness of the proposed calibration framework. Furthermore, vital sign measurements before and after exercise are also measured, which validates the robustness of the proposed algorithm under extreme physiological conditions.