Doppler rader sensing system of respiration and heart rate using circular polarization

Abstract

Wireless bio-signal detection is the recent tendencies in the medical industry, and research for sensing bio-signal continues to rise [1, 2]. The early stage of the system was heavy, bulky, and costly, but the lasts technology in wireless system accomplishes a small and cheap integrated module. The remote sensing of person using RF system is profitable in cost aspects compared with expensive medical instruments. Because the sensing system is easy to handle, even ordinary person who is not instructed about usage of the instruments can use it. The integrated hypersensitive Doppler radar systems are used on this study. The system is composed of antennas, transmitter, receiver, display and baseband part. The bistatic system, which has a Tx antenna and a Rx antenna, has better isolation characteristic compared with monostatic system, which uses one antenna. Through the idea of reverse sense of rotation when the reflecting surface is perfectly-conducting, it is shown that the detecting property of the system can be effectively improved. The link budget about detecting systems is analyzed. We can check the power level at each stage including transmitted and received power at the antenna varying with the distance between antenna and target, and the maximum detection range.