New Concepts in Intrusion Detection

Abstract

This is a continuation of work presented in [1]. It appears possible to measure the Doppler frequency shift caused by radar impinging on blood pumped by the heart to infer the presence of a human in situations where other sensors cannot. This work is applicable to perimeter defense. The relation between the Doppler frequency shift and the pumping action of the heart was modeled mathematically. There is increasing interest in sending electromagnetic signals into the human body, not only for physical security but also for medical reasons [2] To estimate the detection range, propagation of a radar signal through the body is modeled. Input signal is dissipated primarily by scattering at organ interfaces, and attenuation in each organ. Scattering is caused by differences in the index of refraction at each interface. Scattering starts at the air-skin interface. In principal, the approach is valid for many radar frequencies, but high frequencies (GHz) are preferred. However, at these frequencies, significant signal attenuation is expected. Compromise frequencies are therefore being examined. Several hundred MHz might be a good alternative. In addition to examining different frequencies, different signal paths are being examined. Since the radar scans, its signal will enter at different parts of the body and therefore follow different paths, each of which will have a different attenuation. Body parts with expected low and high attenuations have been identified.