Propagation over finite width knife-edge at arbitrary angle to direction of propagation

The calculation of field strength over propagation paths has been approximated by inserting a knife-edge at the highest point of the path, and applying Fresnel diffraction theory at that edge. Until comparatively recently such knife-edge solutions were two-dimensional, that is to say the knife-edges were of infinite extent in the direction transverse to that of the propagation. In 1989 a solution was obtained for a perfectly conducting knife-edge of both finite-height and finite-width. Thus the case of diffraction both over the top and round the sides of this knife-edge became available, although the direction of propagation remained normal to its plane. Because the complexity of the solution is reduced significantly when both these antennas are at ground level, the authors restrict their consideration to such ground based antennas for all the cases they consider. These cases include situations in which the plane of the knife-edge is at an arbitrary angle to the direction of propagation. The case of normal incidence is considered, both from the viewpoint of the compensation theorem and also from a ray theory point of view