A new UTD formulation for multiple cylindrical diffraction
This paper describes a new formulation of the uniform theory of diffraction (UTD) with application to multiple cylindrical structures. The new formulas present some modified UTD diffraction coefficients in cooperation with a slope diffraction term for higher accuracy in the electromagnetic modeling. The above are then combined with a simple ray tracing algorithm that takes into account multipath propagation between cylindrical structures. Comparisons with existing analytical models that employ other electromagnetic theories have shown that the new UTD solution can give very accurate results while it seems to be superior in terms of computation time and complexity. The solution can be applicable to radiowave paths which are characterized by convex structures and multipath propagation such as mountainous areas or urban areas with special rounded objects
Cascaded cylinder model for predicting terrain diffraction loss at microwave frequencies
The problem of determining the diffraction loss between a transmitter and receiver in clear air conditions, when the intervening terrain is given, is treated for propagation at microwave frequencies. A model is developed which simulates the terrain by means of a cascaded arrangement of cylinders. This model, which remains valid at grazing angles, extends Vogler's result for cascaded half planes to treat cylinders. Experiments are conducted on two cylinders which share the same shadow boundary, for both vertical and horizontal polarisation. Measurements are performed on cylinders which present both zero and non zero surface impedance, and these are found to be in good agreement with predictions.
Spectral analysis of high‐frequency diffraction of an arbitrary incident field by a half plane—Comparison with four asymptotic techniques
The knowledge of high-frequency diffraction of an arbitrary wave incident on an edge is important in many applications, such as antennas mounted on aircraft and reflector antennas illuminated by complex feeds. In this paper the problem of a half plane illuminated by a nonplanar wave is investigated using the concept of the plane wave spectral representation. For large wave number k, a new higher-order asymptotic solution for the total field up to and including terms of order k−5/2 relative to the incident field is derived. The behavior of the solution for the observation points which coincide with shadow boundary directions of a multipole line source is discussed in detail. Furthermore, numerical solution of the field integral representation is constructed for the observation angles in the transition regions. The results are compared with those of the Geometrical Theory of Diffraction (GTD), the Uniform Asymptotic Theory (UAT), the Uniform Theory of Diffraction (UTD) and the Modified Slope Diffraction (MSD).