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Introduction to ray methods for modeling the fields of antennas for modern aerospace and wireless applications

Prof. Prabhakar H. Pathak
The Ohio State University ElectroScience Laboratory, Department of Electrical and Computer Engineering, Columbus, OH, USA

20 hours, 5 credits (final test)

October 1 - October 4, 2007
Dipartimento di Ingegneria dell'Informazione: Elettronica, Informatica, Telecomunicazioni, via G. Caruso, meeting room, ground floor

Contacts: Prof. Giuliano Manara

Aims

Modern applications of electromagnetic (EM) theory often require the prediction of EM wave radiation and propagation in large complex environments. Typical examples of interest may involve the performance prediction of antennas (or antenna phased arrays) placed conformally on modern aircraft, spacecraft and naval platforms, or the prediction of propagation of antenna fields from a base station to users in the presence of large buildings as in the case of urban wireless communications, or in the presence of large mountains in a rural environment, etc. Conventional numerical methods become intractable for solving such large problems. On the other hand, high frequency ray methods not only become efficient for treating these types of large problems accurately, but they also provide a simple physical picture for the radiation and diffraction mechanisms present in such problems in terms of various species of rays. The latter property of ray methods is very useful for engineering design purposes. Some basic background for developing EM ray solutions will be presented. Ray solutions based on the uniform geometrical theory of diffraction (UTD) will be introduced. The method of canonical UTD problems will be discussed. Several modern utilizations of the UTD will be demonstrated to deal with the above mentioned problems in aerospace and wireless applications.

Syllabus

• Introduction to UTD as the sum of geometrical optics (GO) and diffracted ray fields. Keller’s postulates. Ray shadow boundaries and caustics/foci. Principle of high frequency localization. Proof of localization using spatial domain EM wave front radiation integral formulation and the stationary phase concept for the development of a ray field. Relation to the spectral domain formulation. (5 hours)
• Stationary phase concept applied to describe EM scattering by a PEC strip in terms of edge diffracted rays. Spectral domain analysis to extract rays in the problem of diffraction by a PEC half plane. General discussion of the method of canonical problems to extract ray physics and to develop UTD canonical solutions. (5 hours)
• Brief summary of many useful and known UTD canonical solutions with simple illustrations. Generalization of canonical UTD solutions to treat arbitrary curved edges and arbitrary smooth convex curved surfaces. (5 hours)
• Illustrations of application of the UTD to predicting patterns of an antenna on an F-16 aircraft, a Boeing 737 and 747 aircraft, a space shuttle, private aircraft, a naval ship, etc. (2.5 hours)
• Illustrations of application of the UTD for predicting EM wave propagation in urban environments involving large buildings for wireless applications. In particular, software developed, by Prof. Paolo Nepa et. al., at the Univ. of Pisa will be demonstrated. (2.5 hours)
• A simple project on UTD simulations will be given to students. All UTD computer subroutines will be provided. Students will work in pre-assigned groups of two (or possibly three) individuals to each group. (5 hours)