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Author: Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
This final report summarizes work done under Grant DAAHO4-94- g-0035. The objective of the investigation was to develop a more rigorous full wave approach to rough surface scattering than that used by Bahar in his full wave method Instead of relying on the use of telegraphists equations a local spectral expansion method was found that is applicable to general rough surface scattering, not just surfaces with roughness in one dimension only. The local spectral expansion method can be formulated so as to involve the tangential fields at the surface as the only unknowns. This is in contrast with Bahar's full wave method which involves coupling integrals between the modes used in expanding the field and is more difficult to use in an iterative procedure. The new method turns out, in the lowest approximation involving the Kirchhoff approximation for the surface tangential fields, to yield significantly more accurate results for most scattering angles. The new approach also covers a wider range of surface parameters that extend from the small perturbation regime to the standard Kirchhoff regime.
Author: Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
This final report summarizes work done under Grant DAAHO4-94- g-0035. The objective of the investigation was to develop a more rigorous full wave approach to rough surface scattering than that used by Bahar in his full wave method Instead of relying on the use of telegraphists equations a local spectral expansion method was found that is applicable to general rough surface scattering, not just surfaces with roughness in one dimension only. The local spectral expansion method can be formulated so as to involve the tangential fields at the surface as the only unknowns. This is in contrast with Bahar's full wave method which involves coupling integrals between the modes used in expanding the field and is more difficult to use in an iterative procedure. The new method turns out, in the lowest approximation involving the Kirchhoff approximation for the surface tangential fields, to yield significantly more accurate results for most scattering angles. The new approach also covers a wider range of surface parameters that extend from the small perturbation regime to the standard Kirchhoff regime.
Author: J. A. Ogilvy Publisher: CRC Press ISBN: Category : Art Languages : en Pages : 300
Book Description
A review of theories developed for the study of acoustic, elastic and electromagnetic wave scattering from randomly rough surfaces, and a comprehensive summary of the latest techniques. Different theories are illustrated by experimental data.With applications in radar, sonar, ultrasonics and optics this book will be invaluable to graduate students, researchers and engineers.
Author: Anthony A. Triolo Publisher: ISBN: Category : Scattering (Physics) Languages : en Pages : 222
Book Description
Rough surface scattering is a current topic of interest in many diverse fields. But, despite its importance, the two most widely used solution methods, the Kirchhoff and first order perturbation methods, are valid only for a restricted range of surface types. There is a large range of surface statistics for which neither of these theories is valid. There are purely numerical solutions to the problem, i.e., the integral equation technique and FDTD method, but these methods require a prohibitively large amount of computer time and storage space for use in practical applications. A full wave method has been introduced by E. Bahar which agrees with the Kirchhoff method in its range of validity, but does not bridge the gap between the later two standard theories and does not provide understanding of the physical processes involved in rough surface scattering. Consequently, it has been a center of controversy since modifications made to improve the method seem arbitrary and are without mathematical or physical justification. The method presented here is a new full wave method which uses equivalent currents to provide insight into the physical scattering processes. This full wave method analytically reduces to the two standard theories in their respective regions of validity and bridges the gap between the two, which was shown by comparison to the integral equation method. The results presented here are for statistically rough surfaces with Gaussian distributed heights and slopes. A Monte Carlo procedure is used to generate the radar cross section data for this new full wave method.
Author: Alexander G. Voronovich Publisher: Springer Science & Business Media ISBN: 3642599362 Category : Technology & Engineering Languages : en Pages : 239
Book Description
Since the fIrst edition of this book was published in the 1994, the theory of wave scattering from rough surfaces has continued to develop intensively. The community of researchers working in this area keeps growing, which provides justifIcation for issuing this second edition. In preparing the second edition, I was challenged by the problem of se lecting new material from the many important results obtained recently. Even tually, a new section was added to the central Chap. 6 of this book. This sec tion describes the operator expansion technique put forward by M. Milder, which conforms well with the general approach adopted in the book and which to my mind is one of the most promising. Remote sensing of the terrain and ocean surface represents one of the most important and interesting challenges to the theory of wave scattering from rough surfaces. Rapid progress in electronics results in sensors with new capabilities. New powerful computers and data communication systems allow more sophisticated data processing techniques. What information about soil or air-sea interaction processes can be obtained from gigaflops of data streaming from air-or space-borne radars? To use this information efficiently, one cannot rely entirely on heuristic approaches and needs adequate theory. I hope that this book will contribute to progress in this important area.
Author: Publisher: ISBN: Category : Languages : en Pages : 15
Book Description
This report summarizes the principal results in three areas of investigation. The first is a new full wave method that takes two dimensional surface roughness into account and does not use the telegraphist's equations. The second study concerns scattering from a rough surface when the incident field is a gaussian beam. The third is a summary of the difficulties inherent in Bahar's extended full wave theory on which the prediction of enhanced backscatter was based. It was found that enhanced backscatter occurred only because of the invalid assumption that the heights and slopes were uncorrelated.
Author: Publisher: ISBN: Category : Languages : en Pages : 35
Book Description
The goal of this project was to complete a study of Bahar's full-wave approach to rough surface scattering that was begun under ONR support. The two proposed items of technical work have been fully completed. In the ONR-supported work, a study was begun for a simplified scattering problem: Scattering from a one-dimensional (1-D) surface with the Dirichlet (zero field) boundary condition using a Gaussian roughness spectrum. The full-wave method was implemented numerically and used in Monte Carlo calculations of the scattering cross section. Comparisons were then made with exact integral equation results, and with the Kirchholl and perturbation approximations. It was found that the full- wave prediction did not reduce to the lowest order perturbation prediction when the perturbation result was known to be accurate, as shown by exact calculations. This is contrary to conclusions reached by Bahar and is an important finding, showing that the full-wave approach is not as general as previously thought. The full-wave prediction did reduce to the Kirchhoff prediction when the Kirchhoff approximation is known to be accurate, as shown by exact calculations. In fact, the full-wave result was found to agree closely with the Kirchhoff result for all cases studied, whether or not the Kirchhoff result was accurate. (rrh).
Author: Qi Wang Publisher: ISBN: Category : Languages : en Pages : 100
Book Description
A full-wave theory of plane wave scattering from rough surfaces called the Correction Current (CC) method was recently developed for the two-dimensional scatter problem that have a one-dimensional roughness profile. The method involves a primary field and radiation modes that are plane-wave-type fields that satisfy the boundary conditions at the rough surface. These fields do not satisfy Maxwell's source free equations, but they are forced to satisfy Maxwell's equations with distributed sources upon the introduction of fictitious volume currents distributions which correct for the field errors. Additionally, current sheet distributions are introduced which generate a radiation modal field that satisfies the boundary conditions, the radiation condition for plane waves, and Maxwell's equations with distributed sources. The scatter problem is solved by eliminating these volume and sheet current densities in an iterative procedure which produces a composite field that satisfies all requirements. Reciprocity is satisfied by using only the first-order field solution. The first-order solution of the CC method reduces to the small perturbation and the Kirchhoff methods in the regions of validity and is more accurate than these methods in regions where neither are considered valid. This paper extends the CC method to the more general and important case of beam wave scattering by a deterministic rough metal surface.
Author: Frank D. Carsey Publisher: American Geophysical Union ISBN: 087590033X Category : Science Languages : en Pages : 466
Book Description
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 68. Human activities in the polar regions have undergone incredible changes in this century. Among these changes is the revolution that satellites have brought about in obtaining information concerning polar geophysical processes. Satellites have flown for about three decades, and the polar regions have been the subject of their routine surveillance for more than half that time. Our observations of polar regions have evolved from happenstance ship sightings and isolated harbor icing records to routine global records obtained by those satellites. Thanks to such abundant data, we now know a great deal about the ice-covered seas, which constitute about 10% of the Earth's surface. This explosion of information about sea ice has fascinated scientists for some 20 years. We are now at a point of transition in sea ice studies; we are concerned less about ice itself and more about its role in the climate system. This change in emphasis has been the prime stimulus for this book.
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Author: J. A. Ogilvy
Author: Anthony A. Triolo
Author: Alexander G. Voronovich
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Author: Qi Wang
Author: Frank D. Carsey
Author: Frederick C. Jackson
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