Complex Radar Cross Section Measurements of the Human Body for Breath-Activity Monitoring Applications

An experimental setup for complex mono-static radar cross section (RCS) measurements in the 1-10-GHz-frequency band, employing a suitably modified semianechoic chamber, is presented and characterized. The foreseen application is the measurement of the complex RCS of the human body during respiratory activity, to ease the design and optimization of ultrawideband (UWB) radar systems for breath-activity monitoring. The proposed RCS test range is calibrated by means of a readily available aluminum flat panel and its performance is tested against canonical targets, evaluating uncertainty in magnitude, and phase measurements. The setup is then employed to carry out investigations on the complex RCS of a volunteer, focusing on its changes resulting from breath activity. Applying the measured RCS patterns to a specifically developed model, the feasibility of the UWB radar approach for achieving a continuous contact-less monitoring of breath activity in a subject at rest is clearly demonstrated. Finally, experimental tests of the application of the proposed radar technique to real-world scenarios are shown, and the safety of RCS measurements and UWB radar monitoring, with reference to exposure of the monitored subject to the radiated electromagnetic fields, is evaluated.