Remote sensing of vital sign of human body with radio frequency

Abstract

Medical technology has improved remarkably in the field of health monitoring over the past few decades, becoming more sophisticated and less invasive as the years progress. Now, non-contact measurement of respiration and heartbeat with microwave Doppler radar phase modulation, offers an attractive alternative to commonly prescribed chest strap monitors. To monitor the vital signs an unmodulated radio frequency signal is transmitted toward the human body, where it is phase-modulated by the periodic physiological movement and reflected back to the receiver. The radar receiver captures the reflected signal and demodulates it to extract the vital sign signal components. The reflected signal from the body depends on the radar cross section (RCS) of body. In this paper the RCS of human body is measured in the X-band (8–12 GHz). There are several advantages to a noncontact measurement method: physically, it neither confines nor inhibits the subject and does not cause discomfort or skin irritation as electrodes and straps do. By measuring heartbeats, this technology can also be used to detect a person’s presence, search-and-rescue for earthquake or fire victims and border patrol. It has also attracted the interest of organizations requiring high security, such as see-through- wall radar and airport security monitoring.