A CURVILINEAR COORDINATE-BASED SPLIT-STEP PARABOLIC EQUATION METHOD FOR PROPAGATION PREDICTIONS OVER TERRAIN

Propagation of radiowaves over irregular terrain and in an inhomogeneo us atmosphere is solved by the parabolic equation method using the spl it-step Fourier algorithm on a terrain-conformal mesh. A piece,vise co ntinuous coordinate system is generated by the specification of: 1) th e terrain profile shape at discrete points and 2) an upper height. The resulting mesh is conformal to the terrain at the lower boundary a:nd gradually flattens off at the maximum height. In addition to preservi ng the number of points on any vertical line between the terrain and t he maximum height from one range step to another, the coordinate trans formation used in the paper produces a correction term in the refracti ve index whose gradient diminishes with height. As a result, the sampl ing requirements over steep terrain are relaxed when compared to the B eilis-Tappert transformation. Formulation and results are given both f or the horizontal and vertical polarizations.