Simplified method for computing knife edge diffraction in the shadow region

A simplified method of computing knife edge diffraction in the shadow region is presented which is applicable to most obstacle gain paths, that is, paths with a dominant mountain obstacle. The method has been worked out for 1) the four-ray model-specular reflection on each side of the obstacle, 2) the two-ray model-reflection on one side only, and 3) the single-ray model-no reflection on either side. The obstacle can be at any location along the path. The accuracy is within 2 db for path geometries such that the usual diffraction parameter is greater than 1 and the two terminal heights are less than the obstacle height. Curves which further simplify the computation procedure are presented.