Millimeter-Wave Doppler Spectrum and Polarimetric Response of Walking Bodies

In this paper, the Doppler spectra of the radar backscatter response of human body and a quadruped are presented at W-band frequencies. This study is motivated by the desire to utilize millimeter-wave radars to detect pedestrians against other targets in the radar scene. The approach is based on dissecting the radar backscatter to isolate the radar returns from different body parts. The forward model is based on an iterative physical optics approach. The complex motion of different parts of walking bodies and their amplitude and range of motion is directly reflected in their radar cross section (RCS) and Doppler spectrum bandwidth. It is shown that the Doppler spectra and RCS differences are sufficient to distinguish a walking human from stationary and other moving objects. Radar polarimetry in conjunction with time-frequency analysis is examined as a method for detecting concealed carried objects. The overall backscatter is decomposed into components associated with the limbs and torso which are then utilized to enhance target detection.