A multifrequency interferometric CW radar for vital signs detection

The use of radar techniques to detect minute body movements which are associated with respiration and cardiac activity (vital signs) is known at least since 1975 when J.C. Linn and J. Salinger proposed a non-contact microwave respiration monitor [1]. In 1979 Lipkin et al proposed CW respiration detector designed for surveillance purposes at Carnahan Conference on Crime and Countermeasures [2]. The first generation of commercially available CW radar purposely designed for detecting the presence of persons in visually obstructed areas was released in 1991 [3], the second generation followed in 1998 [4], it also had been the first radar which use led to documented rescue of two persons out of the debris on an earthquake area Niigata in Japan [5].