Physical modeling of EM propagation over nonhomgeneous terrain

To obtain experimental data for comparison with the theoretical results obtained from mathematical groundwave propagation models, it is often expedient to conduct experiments on laboratory models using microwaves. Besides the obvious convenience and reduced cost, practical difficulties encountered in full scale experiments are avoided (e.g., weather and other uncontrolled parameters such as path nonhomogeneities, earth curvature, buildings, right-of-ways, etc.). There is no need to use exact similitude scaling; the media and geometries are generally chosen to test the limits of the theory's validity. The design of several much models in the frequency range of 405 GHz is discussed, and the experimental results are compared with the corresponding theory. Specific examples are propagation over planar and curved surfaces (including stratified media, e.g., layered earth, sea ice, etc.), mixed paths (including media having abrupt discontinuities such as land-sea boundaries, gradual nonuniformities such as sloping beaches, off-path such as land-sea boundaries, gradual nonuniformities such as sloping beaches, off-path discontinuities such as islands, lakes and peninsulas), uniaxially anisotropic media, and media having an index of refraction near unity such as heavy vegetation.