Non-invasive detection of respiration and heart rate using high sensitivity radar

Abstract

The systematic monitoring of vital signs such as respiration and heart rate has a significant influence on many conditions in the medical field. During the past several decades, medical technology has improved remarkably, and bio-sensor systems have been used to detect the respiration and heart rate. Nowadays, respiration and heart rate monitoring with Doppler radar offers an attractive alternative to commonly pre-scribed chest strap monitors. By utilizing these techniques, non-contact detection can be used to monitor the vital signs of humans or animals from a significant distance away, without any sensor attached to the body. As microwaves have great penetration capability, Doppler radar can detect the heart and respiration rates through clothing, making it a non-invasive method. As interest in health increases, many research institutions have studied radar structures, demodulation techniques, and detection algorithms to achieve accurate performance. Various Doppler radar systems for detecting respiration and heart rate are proposed. First, Doppler ra-dar which has a direct-conversion and single channel receiver structure is presented in Chapter 3. It can be integrated with compact size because of its simplicity and increase the sensitivity using a circular polarization characteristic. The operating frequency of the system is in the X-band and the radar size is 95 x 50 x 13 mm3. Second, X-band radar system which has a heterodyne and a quadrature receiver with series-fed array antenna is proposed. An array antenna with high gain and elliptical polarization make the detection range up to 5 meters. Last, Doppler radar system with high sensitivity for long range detection at Ku-band in Chapter 4. Heterodyne structure, highly sensitive quadrature receiver, and leakage cancellation technique have been implemented in order to increase the detectable range of the radar system. Arctangent demodulation without additional dc offset compensation technique can be applie...