A Review on Recent Advances in Doppler Radar Sensors for Noncontact Healthcare Monitoring

Monitoring vital signs over multiplexed radio by near-field coherent sensing

“…The green markers were measured with a commercial blood pressure monitor (OMRON BP760N). Note that the breath and heartbeat information is independently derived from the quadrature demodulation, and no special filtering or pattern recognition as in the conventional microwave backscattering is required 27,28 . Because the internal vital signals are retrieved from NCS, the interferometer-like structure significantly increases the sensitivity to enable collection of the motion waveform, similar to a ballistocardiogram (BCG) 29 .…”

Ultra-Wide Patch Antenna Array Design at 60 GHz Band for Remote Vital Sign Monitoring with Doppler Radar Principle

“…In the recent couple of decades, a significant amount of research has been conducted to improve the accuracy of the RVSM by employing various techniques including distance and frequency optimization [13][14][15][16][17][18], robust signal processing methods [19][20][21], breath holding for HR detection and so on [22][23][24][25][26][27][28]. However, most of the reported practical work is based on Doppler radars working at lower microwave (MW) frequency bands around 2.4, 5.8 and 10 GHz where the wavelength resolution of the electromagnetic wave is low and therefore the accuracy of the vital signs detection, especially the HR, remained challenging [23].…”

“…The main motives of RVSM at MMW frequencies include (i) improvement in the detection accuracy by employing shorter wavelength of the signal, (ii) smaller form factor for the device compactness and (iii) possibility of more subject focused signal transmission and reception to avoid the interference from the unwanted side reflections [22,[33][34][35]. From MMW band, 60 GHz band (57-66 GHz) has drawn more attraction because this band is free of licence and is quite mature due to its extensive use for several other wireless services [27].…”

“…The antenna should be designed in such a way that it only focuses the radiation beam on the subject [22] and should have an adequate gain to maintain a required signal to noise ratio [31]. Microstrip patch antennas are thought to better option for compact MMW sensors due to their embedment with on-chip devices, low profile, low cost and ability to make array to attain high antenna gain [23,[30][31][32].…”

Comparison between different decorrelation techniques in vital sign detection

“…Leakage between the TX and RX channels, null point problem, stability of local oscillator and strong clutter coming from environment are among the problems to be faced [3].…”