Noncontact measurement of cardiopulmonary movements: A review of system architectures and the path to micro-radars

This paper reviews the technology development history of noncontact measurement of respiration and heartbeat using microwave techniques, and shows how the technology evolved into small micro-radars. Through understandings of its detection mechanism and advances in hardware and software, the once bulky bench-top systems can be miniaturized while achieving better performance. The evolution of system architectures, detection methods, and choice of frequencies are reviewed. Vital-sign micro-radar sensors implemented in complementary metal-oxide-semiconductor (CMOS) and system-in-package technologies at the 5.8-GHz and 60-GHz industrial, scientific, and medical (ISM) bands are presented. The noncontact vital sign micro-radars can be used for various potential applications including healthcare, veterinary medicine, and biological research.