Noncontact Accurate Measurement of Cardiopulmonary Activity Using a Compact Quadrature Doppler Radar Sensor

Abstract

The designed sensor enables accurate reconstruction of chest-wall movement caused by cardiopulmonary activities, and the algorithm enables estimation of respiration, heartbeat rate, and some indicators of heart rate variability (HRV). In particular, quadrature receiver and arctangent demodulation with calibration are introduced for high linearity representation of chest displacement; 24-bit ADCs with oversampling are adopted for radar baseband acquisition to achieve a high signal resolution; continuous-wavelet filter and ensemble empirical mode decomposition (EEMD) based algorithm are applied for cardio/pulmonary signal recovery and separation so that accurate beat-to-beat interval can be acquired in time domain for HRV analysis. In addition, the wireless sensor is realized and integrated on a printed circuit board compactly. The developed sensor system is successfully tested on both simulated target and human subjects. In simulated target experiments, the baseband signal-to-noise ratio (SNR) is 73.27 dB, high enough for heartbeat detection. The demodulated signal has 0.35% mean squared error, indicating high demodulation linearity. In human subject experiments, the relative error of extracted beat-to-beat intervals ranges from 2.53% to 4.83% compared with electrocardiography (ECG) R-R peak intervals. The sensor provides an accurate analysis for heart rate with the accuracy of 100% for p = 2% and higher than 97% for p = 1%.

Accurate heartbeat monitoring using ultra-wideband radar

“…[12,13,14], and 94.0 GHz [15,16,17,18]. Among these studies, only a few [1,2,8] successfully measured the instantaneous heart rate, which would allow the assessment of heart-rate variability. A received CW signal contains not only the echo from the subject but also echoes from other objects called clutters and crosstalk between antennas.…”

“…A received CW signal contains not only the echo from the subject but also echoes from other objects called clutters and crosstalk between antennas. These undesirable components must be removed using DC suppression techniques [1,8] and the center estimation method [10,19]. Such techniques, however, work only when the clutter is stationary; if there is more than one person or other moving objects in the scene, their motion cannot be distinguished from that of the target.…”

Detection of Breathing Rates in Through-wall UWB Radar Utilizing JTFA

“…Among many existing non-contact detection systems, the electromagnetic detection method is the most concerned technique for life sign detection due to the radar pulses are modulated by life activities such as human respiratory and heartbeat. Impulse ultra-wideband (UWB) radar has been widely applied to track moving targets, through-wall imaging and son on due to its excellent time resolution and strong permeability [6][7][8][9][10][11][12][13]. However, extensive researches on life sign detection need to be made based on UWB radar [14][15][16][17][18][19][20][21][22].…”

Remote heartbeat monitoring from human soles using 60-GHz ultra-wideband radar

“…Recently, much attention has been paid to the remote monitoring of heartbeats using radar systems [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23] that measure the slight displacement of a patient's skin surface due to heartbeats. However, patients in an MR scanner are surrounded by the interior wall of the scanner, with only the top of their head and soles seen from the outside.…”

“…In this study, we demonstrate the possibility of the remote measurement of heartbeats from soles using an ultra-wideband radar system. Most existing studies of the remote monitoring of heartbeats use echoes from the torso [5,6,7,8,9,10,11,12,13,14,15,16,17,18], whereas there have been no reports on remote monitoring of heartbeats from the soles.…”