Simplified and fast iterative physical optics algorithm for human body analysis at W-band

The millimeter-wave (MMW) region of electromagnetic spectrum presents a unique opportunity in detection of pedestrians in heavy clutter environment and hidden objects carried by individuals. In our previous studies [1], [2], we presented polarimetric radar Doppler signature of walking human and dog at 95 GHz. We utilized physical optics (PO) method to model the body with equivalent PO surface and geometrical optics (GO) method to determine the shadowed areas for a given orientation of human body with respect to the direction of the incident wave. The first order PO approach does not actually account for interactions between different body parts. As a result, an accurate cross-polarized response cannot be expected. To alleviate this problem, we employed Iterative PO model in which the interactions between body parts are fully accommodated. In this analysis, human body is descretized into a number of flat facets for each of which the induced currents resulted from other facetspsila scattered field is also taken into account. In this case, if the number of constituent facets is N, the operation of calculating all the interactions is on the order of N² since each facet has N operations (interactions). This is unlike the first order PO in which we had one operation for each facet and analysis was on the order of N. This massive number of operations for higher order PO brings up some difficulties regarding the exorbitant computation time needed for analysis of a walking individual. This challenge forced us to revise the scheme and take advantage of some features in human body to make the IPO analysis computationally tracktable.