Uniform Theory Of Diffraction Coefficients Research Articles

Analysis of Heuristic Uniform Theory of Diffraction Coefficients for Electromagnetic Scattering Prediction

We discuss three sets of heuristic coefficients used in uniform theory of diffraction (UTD) to characterize the electromagnetic scattering in realistic urban scenarios and canonical examples of diffraction by lossy conducting wedges using the three sets of heuristic coefficients and the Malyuzhinets solution as reference model. We compare not only the results of the canonical models but also their implementation in real outdoor scenarios. To predict the coverage of mobile networks, we used propagation models for outdoor environments by using a 3D ray-tracing model based on a brute-force algorithm for ray launching and a propagation model based on image theory. To evaluate each set of coefficients, we analyzed the mean and standard deviation of the absolute error between estimates and measured data in Ottawa, Canada; Valencia, Spain; and Cali, Colombia. Finally, we discuss the path loss prediction for each set of heuristic UTD coefficients in outdoor environment, as well as the comparison with the canonical results.

Heuristic UTD coefficients for electromagnetic scattering by lossy conducting wedges

AbstractIn this study, heuristic uniform theory of diffraction coefficients are suited to account for scattering by lossy conducting wedges.The novel heuristic solution is determined from other previously developed heuristic coefficients, combining their characteristics to improve the estimation of radiowave propagation in urban scenarios. Slope diffraction is also considered to account for double‐diffracted fields in consecutive wedges. Maliuzhinets' coefficients provide base solutions to validate the novel formulation. The novel solution is then applied to the wave propagation in a typical urban scenario, and results are compared against measurements provided in the literature. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2657–2662, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25557

A new solution expressed in terms of UTD coefficients for the multiple diffraction of spherical waves by a series of buildings

A new formulation expressed in terms of Uniform Theory of Diffraction (UTD) coefficients for the prediction of the multiple diffraction caused by a series of buildings modeled as wedges, considering spherical‐wave incidence, is presented. The solution, which has a certain heuristic nature, is validated with numerical results from technical literature and the particular cases of diffraction by buildings modeled as absorbing knife edges, as well as the one in which the mentioned buildings are replaced by flat‐roofed parallel rows of blocks (building rows in cross sections considered to be rectangular in shape) are also analyzed. The computing time is reduced over existing formulations, especially when the number of buildings is large, and the results can be applied in the development of theoretical models, in order to predict a more realistic path loss in urban environments when multiple‐building diffraction has to be considered.

Novel Heuristic UTD Coefficients for the Characterization of Radio Channels

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents novel heuristic coefficients for the uniform theory of diffraction (UTD), suited to analyze the scattering by lossy conducting wedges in an efficient and reciprocal manner. For its reciprocal properties, the coefficients are appropriate to handle complex scenarios with arbitrary transmitter and receiver positions. The new coefficients take advantage of two previously proposed heuristic coefficients, combining both in a novel approach. The diffraction by arbitrary conducting wedges is investigated and results are compared with those given by accurate Maliuzhinets and method-of-moments analyses. The proposed technique is then applied to characterize the scattering through a typical urban scenario in order to demonstrate its applicability. </para>

Wiener-Hopf Solution for Impenetrable Wedges at Skew Incidence

A new Wiener-Hopf approach for the solution of impenetrable wedges at skew incidence is presented. Mathematical aspects are described in a unified and consistent theory for angular region problems. Solutions are obtained using analytical and numerical-analytical approaches. Several numerical tests from the scientific literature validate the new technique, and new solutions for anisotropic surface impedance wedges are solved at skew incidence. The solutions are presented considering the geometrical and uniform theory of diffraction coefficients, total fields, and possible surface wave contributions

A solution expressed in terms of UTD coefficients for the analysis of the multiple diffraction in urban areas with shadowing caused by terrain effects

AbstractA function expressed in terms of uniform theory of diffraction (UTD) coefficients for the analysis of multiple diffraction in urban areas where a bare wedge‐shaped hill causes shadowing of the transmitter from the receiver (a non‐line‐of‐sight situation) is presented. The solution, validated by numerical results from the technical literature, has a good computational efficiency and increases the versatility over existing formulation, thus allowing study of the abovementioned environment when a small number of buildings is considered as well as when a spherical‐wave incidence over these latter is assumed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 523–525, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21218

An improved solution expressed in terms of UTD coefficients for the multiple-building diffraction of plane waves

A new formulation expressed in terms of uniform theory of diffraction (UTD) coefficients for the prediction of the multiple diffraction produced by an array of finitely conducting buildings considering plane-wave incidence is presented. The solution considers the building cross sections to be rectangular as well as the source to be above or level with the building's height and, due to the fact that only single diffractions over finitely conducting wedges are involved in the calculations, an easier final formulation is achieved. Furthermore, the computing time is reduced over existing solutions especially when the number of buildings is large. The proposed formulation can find application in the development of theoretical models to predict more realistic path loss in urban environments when multiple-building diffraction has to be considered.

A multiple‐building diffraction attenuation function expressed in terms of UTD coefficients for microcellular communications

AbstractThis work presents an explicit formulation for multiple‐edge diffraction for mobile radiowave propagation in terms of uniform theory of diffraction (UTD) coefficients when a spherical incident wave is considered. This solution can be used in an UTD context and sharply reduces the computing time over existing formulation. Results can be applied in the planning of microcellular systems. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 298–300, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11359

Dihedral corner reflector backscatter using higher order reflections and diffractions

The uniform theory of diffraction (UTD) plus an imposed edge diffraction extension is used to predict the backscatter cross sections of dihedral corner reflectors which have right, obtuse, and acute included angles. UTD allows individual backscattering mechanisms of the dihedral corner reflectors to be identified and provides good agreement with experimental cross section measurements in the azimuthal plane. Multiply reflected and diffracted fields of up to third order are included in the analysis for both horizontal and vertical polarizations. The coefficients of the uniform theory of diffraction revert to Keller's original geometrical theory of diffraction (GTD) in cross section analyses, but finite cross sections can be obtained everywhere by considering mutual cancellation of diffractions from parallel edges. Analytic calculations are performed using UTD coefficients; hence accuracy required in angular measurements is more critical as the distance increases. In particular, the common far-field approximation that all rays to the observation point are parallel is too gross of an approximation for the angular parameters in the UTD coefficients in the far field.