Considerations in measuring vital signs cross section with Doppler radar

This paper describes the different considerations and challenges in measuring human cardiopulmonary radar cross section (RCS). The effect of clutter on the received signal is explained as well as the importance of preserving baseband dc content for valid readings. The center estimation algorithm with dc-cancellation is presented as a solution to restore dc content in the baseband signals and to exclude clutter contribution. The far-field conditions for the target range are revisited. By modeling the human torso as a half-cylinder and assuming unity reflectivity, the ratio of the RCS of the back of the torso with respect to the front is a function of wavelength. At 2.4 GHz and for a chest breadth of 30 cm, the back is expected to have an RCS that is 10 times that of the front while the RCS of the side is expected to be 4 times smaller.