Electromagnetic Wave Theory. Proceedings of a Symposium Held at Delft, The Netherlands, September 1965 PDF
Preview Electromagnetic Wave Theory. Proceedings of a Symposium Held at Delft, The Netherlands, September 1965
OTHER TITLES IN THE SERIES ON ELECTROMAGNETIC WAVES Vol. 1 Diffraction by Convex Surface - FOCK Vol. 2 Ionospheric Sporadic E - SMITH AND MATSUSHITA (Editors) Vol. 3 Electromagnetic Waves in Stratified Media - WAIT Vol. 4 The Scattering of Electromagnetic Waves from Rough Surfaces BECKMANN AND SPIZZICHINO Vol. 5 Electromagnetic Scattering - KERKER Vol. 6 Electromagnetic Theory and Antennas - JORDAN Vol. 7 The Propagation of Electromagnetic Waves in Plasmas - GINZBURG Vol. 8 Tropospheric Radiowave Propagation beyond the Horizon - DU CASTEL Vol. 9 Dipole Radiation in the Presence of a Conducting Half-space - BANOS Vol. 10 Electrical Methods in Geophysical Prospecting - KELLER AND FRISCH KNECHT ELECTROMAGNETIC WAVE THEORY Parti Proceedings of a Symposium held at Delft, The Netherlands, September 1965 Edited by J. BROWN SYMPOSIUM PUBLICATIONS DIVISION PERGAMON PRESS OXFORD · LONDON · EDINBURGH · NEW YORK TORONTO · SYDNEY · PARIS · BRAUNSCHWEIG Pergamon Press Ltd., Headington Hill Hall, Oxford 4 & 5 Fitzroy Square, London W. 1 Pergamon Press (Scotland) Ltd., 2 & 3 Teviot Place, Edinburgh 1 Pergamon Press Inc., 44-01 21st Street, Long Island City, New York 11101 Pergamon of Canada, Ltd., 6 Adelaide Street East, Toronto, Ontario Pergamon Press (Aust.) Pty. Ltd., 20-22 Margaret Street, Sydney, New South Wales Pergamon Press S.A.R.L., 24 rue des Ecoles, Paris 5e Vieweg&Sohn GmbH, Burgplatz 1, Braunschweig Copyright © 1967 Pergamon Press Ltd. First edition 1967 Library of Congress Catalog Card No. 66-17928 (2890/67) SYMPOSIUM COMMITTEE (Organizing and Technical Committees) F.L.H.M.STUMPERS, the Netherlands, Chairman H.M.BARLOW, U.K. H.BREMMER, the Netherlands H.A.W.GOOSSENS, the Netherlands, Treasurer A.T. DE HOOP, the Netherlands O.E.H.RYDBECK, Sweden J. P. SCHOUTEN, the Netherlands K.M.SIEGEL, U.S.A. V.I.SIFOROV, U.S.S.R. B.D.H.TELLEGEN, the Netherlands R. TIMMAN, the Netherlands, Secretary G. TORALDO DI FRANCIA, Italy INTRODUCTION AN U.R.S.I. Symposium on Electromagnetic Wave Theory was held in Delft from September 6 to 11, 1966. It was sponsored by the International Scientific Radio Union (U.R.S.I.) and its Netherlands National Committee, by the Tech nological University of Delft, and by the Netherlands Electronic and Radio Society (N.E.R.G.). It was during a visit of Professor Timman to the University of Michigan, that Professor Siegel, president of the Symposium Committee of U.R.S.I. Commis sion VI, suggested that it would be in line with the great Dutch scientific tradition to organize this Symposium. Professor Timman got the approval of the Board of his University, the National Committee of U.R.S.I. also agreed to sponsor the invitation, and during the Plenary Assembly of U.R.S.I. in Tokyo 1963, the invitation was accepted. The pioneer of the Dutch tradition in this sector of physics certainly was Christiaan Huygens 1629-95. Three hundred years before the date of our Sym posium we find in his works references to the wave propagation of light. He discussed spheroidal waves in 1677, and his famous "Traite de la lumiere" was prepared in 1678. It was printed in 1690. Huygens' principle still finds fruitful application in modern calculations on electromagnetic wave theory. The full title of his treatise: "Traite de la lumiere ou sont expliquoes les causes de ce qui luy arrive dans le reflexion et dans le refraction et particulierement dans l'etrange refraction du cristal d'islande" is also remarkable because of its strong relation to the title of a thesis of about 200 years later: "On the theory of reflection and refraction of light", 1875. In this work (in Dutch) the then 22 year- old H. A.Lorentz gave the first sign of his great talents by calculations based on the electromagnetic theory of light, proposed by Clerk Maxwell in 1865. About 1880 he derived the Lorentz-Lorenz relation between the macroscopical optical properties of the medium and the properties of the scattering particles. The second Lorenz is the famous Danish physicist L.V. Lorenz, who found the relation independently at about the same time. In later years the coherence theory of light, lately so much in the forefront because of laser develoments, was developed by van Cittert (1934) and Zernike (1938) at the universities of Utrecht and Groningen in our country. Zernike's many ideas and developments in the application of the theory of light won him a Nobel prize. The study of electromagnetic wave propagation for radio purposes owes much to the great talents of another Dutch physicist, so well known in U.R.S.I., Professor Balth van der Pol. His paper "On the propagation of radiowaves over a finitely con ducting spherical earth" (with H.Bremmer) is a classic. His last paper (with xin XIV INTRODUCTION A.Levelt) published posthumously, was still devoted to this branch of science: 'On the propagation of a discontinuous electromagnetic wave" (1960). If there is a long and strong tradition in the Netherlands in the study of wave propagation there is also the tradition in U.R.S.L on which we could build forth. The U.R.S.L Symposia form a distinguished list: McGill University, Montreal 1953, Michigan University, Ann Arbor, 1955, University of Toronto, 1959, Technical University of Denmark, Copenhague 1962. To organize the next Symposium in this series was not only a question of effort but also of money. The Committee received substantial donations from the "International Scientific Radio Union", the Netherlands National Committee of U.R.S.L, the Philips Industries in the Netherlands, the Netherlands Radar Research Station. The following Netherlands companies, firms and foundations also con tributed by donations to the success of the Symposium: Van der Heem N.V., I.B.M. Nederland, P. J. Kipp and Sons, Netherlands Cable factories, Neth. Standard Electric Cy, N.V. Radium, the Dutch P.T.T., Dutch Mathematical Society. It is a great pleasure to thank the Minister of Education and the Boards of Curators of the Technological University, Delft, for their approval to hold the symposium in the Main Building of the Technological University. The Minister also gave a substantial financial guarantee for which we were very thankful, although it proved unnecessary to make use of it. The Technological University assisted the organizing committee in very many ways. The congress bureau of the city of the Hague, where most participants were lodged, also gave much assistance and support. An organizing and technical committee was formed, many members of which could only help us by correspondence. We wish to mention especially that Professor Barlow drafted the first programme, and that we had many useful additions and names through a U.S. Committee under Professor Siegel. Pro fessor Siforov helped in organizing the participation from U.S.S.R. scientists. For most of the practical organization problems Professor Timman, Mr. Goos- sens and the chairman formed a small executive committe. The opening ceremony of the Symposium on Monday, September 6, 1965, was attended by a representative of the Minister of Science and Education, the Mayor of Delft, the Secretary of the College of Curators of the University, the chairmen of the Delft Departments of Electrical Engineering and General Science and by many participants of the Symposium. After a word of welcome by the chairman, Professor Kuypers, acting rector, gave an address on the history of the University and its future. He then officially opened the Symposium. Pro fessor Manneback for U.R.S.L thanked the University for its cooperation and wished the Symposium every success. After a coffee break, Professor Barlow gave his as-usual clear lecture on "Millimetre Waves and Optical Waves for Long Distance Telecommunications", and Mr. Kampinsky spoke on: "Ex perimental Evaluation of the results of the passive Communication Satellite, Echo II." In the afternoon the symposium split into a section on Antenna Theory, chaired by Professor Knudsen and Professor Roubine and a section on Pro- INTRODUCTION XV pagation in Inhomogeneous Media chaired by Dr. Stumpers. Invited papers were given by Professor Felsen (on "Lateral waves"—even among the good invited papers an excellent one) and by Professor Karbowiak (on "Aspects of Propagation in Inhomogeneous Media"). In the evening the acting Rector gave a reception to the participants and their ladies. On Tuesday the section on antennas continued. In addition, we had a section on Propagation in Plasmas, chaired by Professor Cloutier, with an invited paper by Professor Rydbeck (some wave propagation phenomena in ionized media), and a section on Underground Waves and Space Waves, chaired by Professor de Hoop, with an invited paper Dr. J. Wait (Terrestrial Waveguides). Wednesday was devoted to a very interesting excursion to the Delta project. The plans of closing the sea arms were discussed, and some dykes and sluices were visited. The long boat trip from Hellevoetsluis to Rotterdam gave an opportunity to renew old friendships and to discuss mutual problems. On Thursday Professor Timman chaired a session on Boundary Value Prob lems (invited paper: Professor S.Karp). Professor Siforov chaired a session on Millimetre Waves and Optical Waves. (The invited paper was that given by Professor Barlow on Monday). D. Kay chaired the session on Coherence Prob lems and Modern Optics. In this session Professor Marechal gave an invited paper on Wavefront Optics, and Professor Picinbono one on Statistical Optics. Some of these sections continued on Friday. New sections then started on Surface Waves and Wave Beams, chairman Professor Barzilay, with invited papers by Professor Oliner (Guided complex waves on slow wave periodic structures) and Dr.Zucker (Aspects of the theory of surface waves). Another section was devoted to Propagation in Nonlinear Media, chairman Professor Siegel, and had quite a number of contributions from Russian scientists. Saturday was divided between Multiple Scattering and Scattering on Rough Boundaries, in one hall and Deterministic Scattering in the other hall of the University. The first session was chaired by Professor van de Hülst, and invited papers were given by Dr. Twersky (Multiple scattering of waves by N-bodies) and by Professor Saxon (Propagation in random and periodic lat tices). The second session was chaired by Professor Marcuvitz, and the invited paper was given by Dr. Weston (Recent highlights in Diffraction Theory). Shortly before 2 o'clock Dr. Stumpers thanked the chairmen, speakers and participants and closed the Symposium. On Friday night a banquet was organized in the Kurhaus Hotel, attended by many participants and their ladies. Professor Siegel presided and Professor Casimir gave the after-dinner speech; in a parable he slightly teased the theore ticians about their prolonged discussions on unit systems. Professor Silver addressed the participants on behalf of the Board of U.R.S.I. Professors Marechal, Knudsen and Siforov spoke on behalf of the foreign participants and Dr. Stumpers for the organizers. Apart from the invited lectures, 117 contributions were presented at the Sym- XVI INTRODUCTION posium. For this reason there were always two sessions simultaneously, but those who so desired could follow all the papers on any subject. The number of registered participants was 264; 64 from the United States, 46 from the Nether lands, 25 from France, 24 from the United Kingdom, 20 from Danmark, 18 from Italy, 14 from Sweden, and 14 from U.S.S.R.—Canada, Poland, Norway, Greece, D.D.R., Switzerland, Hungary, Yougo-Slavia, Australia and Finland were also represented. During the Symposium the main burden of organisatorial activities fell on Mr. Goossens (Rear-Admiral, retired). Mrs. Timman, chairman of the Ladies Committee, and Mrs. de Hoop organized daily trips to picturesque parts of the country for the ladies and children of the participants. From a scientific point of view the classical subjects; inhomogeneous media, antenna theory, boundary value problems and surface waves had most attention. We had hoped for more contributions on millimetre waves and optical waves, coherence problems, modern optics and scattering problems, but apparently the attention in universities and research institutes shifts only slowly. Many international contacts were renewed and new contacts laid. The state of the art and the still open problems in our domain were clearly exposed. In this way this Symposium fulfilled the main task given to the Symposia of the International Scientific Radio Union. I hope it was a worthy successor to Copenhague, etc. After the Symposium, Professor John Brown accepted an invitation to edit the Transactions. On behalf of all readers we thank him and Pergamon Press, the publishers, for their work. Dr. F. L. STUMPERS Chairman Commission VI International Scientific Radio Union SECTION A WAVE PROPAGATION WAVE PROPAGATION IN INHOMOGENEOUS MEDIA A.E.KARBOWIAK University of New South Wales, Kensington, N.S.W. 1. INTRODUCTION Wave propagation problems in inhomogeneous and anisotropic media are of very frequent occurrence; in fact it is the phenomenon of wave propagation in homogeneous and anisotropic structures that occurs rather infrequently in nature. We recognize at the outset that wave propagation problems under the most general, unrestricted inhomogeneous and anisotropic conditions neither have explicit (and useful analytical solutions) nor can such problems be within our conceptual control (and adequate grasp). It is because of the complexity of the real problem that we find it necessary to restrict the class of problems to which our solutions apply. In the course of trying to simplify the characterization of our physical processes we tend to isolate different classes of problems and to study certain limiting conditions of real physical situations. It is in this process of reasoning that various patterns begin to emerge. But it is precisely at this point that we should question our process of thinking and wonder whether the patterns thus revealed—by painstaking analysis—are really projections of the physically undergoing phenomena or perhaps they are simply reflections of the patterns of our way of thinking, with little relation to physics. Necessarily, we find ourselves simplifying our physical models to a manageable level, to permit the use of known mathematical methods. Yet many a simplifica tion hides a clue to the solution of the real physical problem, thus taking us no nearer our final goal. Moreover, what appears to be a useful model may take us on a long chase of what may be a fascinating, but irrelevant class of problems. What do we need to help us in the growing complexity of problems? Until recently it was the time-consuming numerical evaluation of many problems that was the main stumbling block; but now, equipped with powerful computers, this is no longer the case. We need new and more powerful analytical tools and alongside of this a wider and deeper conceptual grasp of physics. Let us now examine the nature and breadth of the problems and perhaps then we will be in a better position to assess our needs. EWTI 1 1 2 A.E.KARBOWIAK 2. PARTICULAR ANALYTICAL APPROACHES 2.1. "Exact Solutions" The most successful analytical solutions are invariably based on some "judicious approach" and this is particularly true of various synthesis problems, where we recognize that certain particular configurations lead to a clearly defined class of problems, which, subsequently, can be tackled by well estab lished mathematical methods. In such cases explicit closed form solutions can be obtained. Such cases are, however, rare. 2.2. Approximate Solutions All other analytical approaches are based on approximations. Their successes are therefore limited by the explicit, and sometimes even implicit, approxima tions. The more successful approximate methods include: (1) variational methods, (2) perturbation calculus, (3) asymptotic evaluations, (4) WKB method, (5) Rayleigh-Ritz method, (6) statistical approach. 2.3. New Concepts New concepts are sometimes of assistance in analysis, but more frequently they are a help in understanding the physical processes. Often, new concepts are born out of an attempt of trying to gain a better understanding of physics. In theory of wave propagation new concepts embrace waves such as, for example: (a) surface waves, (b) leaky waves, (c) quasi-modes, (d) backward waves, (e) longitudinal section waves, (f) equivalent circuits, (g) rays and geometrical optics, etc. 3. PARTICULAR "PHYSICAL" CONFIGURATIONS 3.1. Plane Waves along a Plane Interface Separating two Dissimilar Media The class of problems encountered in wave propagation in the presence of a plane interface is now well understood. Here plane waves of types (a), (b) and (c) are found depending on circumstances, but because planes of infinite extent
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