Effects of atmospheric refractivity and variability on passive radar performance prediction

This paper presents results from model-based work investigating the influence of atmospheric refractivity on the performance of UHF passive radars, using parabolic-equation (PE)-based propagation techniques. It is shown that, since PE-based models are monochromatic, modeling the illuminator bandwidth can smooth their usual multipath power variations; this smoothing can affect the maximum predicted range of the radar. Further, it is shown that changing atmospheric conditions (refractivities) can impart meaningful variations in illumination and path loss at a variety of ranges and altitudes, ultimately affecting the radar's coverage. Finally, it is shown that, although specific refractivities do affect the realized radar performance, they do not appear to strongly influence the selection of optimal illuminators in channel-constrained passive radars.