An instruments-built Doppler radar for sensing vital signs

In this paper, we presented a fast solution to construct a Doppler radar system used for detecting vital signs by non-contact means. The radar system is constructed by instruments which are widely used and equipped in radio frequency and communication laboratories. Therefore, this work demonstrates the feasibility to conduct research on vital sign detection in ordinary radio frequency laboratories, while the existing vital sign detection systems must cost much effort to build. Digital IF technique is applied to help mitigate quadrature channel imbalance occurring in the quadrature radio architecture, and eliminate the complicated DC offset calibration required for arctangent demodulation. A 2.4GHz microchip patch antenna array was designed and used to carry out extensive experiments. When the transmit power is 0dBm, the detection range extends to 2.5m, with an accuracy of higher than 80%.