Modeling of human torso time-space characteristics for respiratory effective RCS measurements with Doppler radar

The wave returning from a human torso in radar measurements is affected by the characteristics of the abdomen with respect to the thorax. While the physical properties affect the magnitude of the reflected components from each part, the motion delay and level offset result in different phases. This paper demonstrates a theoretical model for the torso time-space characteristics by formulating the baseband signal of a CW Doppler radar system as a superposition of two components, one from the thorax and the other from the abdomen. Measurements of a female subject in a supine position are used for verification. By reproducing the measured baseband signal, the respiration parameters could be identified for the subject under test.