High frequency approximations to multiple scatter by rough surfaces that exhibit enhanced backscatter (original) (raw)
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Experimental study of enhanced backscattering from one- and two-dimensional random rough surfaces
Journal of the Optical Society of America A, 1990
An experimental study of backscatter enhancement from rough surfaces is presented. The Stokes parameters of the average scattered light from two-dimensional rough surfaces show the presence of an unpolarized component, which lends support to the multiply scattering ray model. Experimental data from one-dimensional rough surfaces are compared with numerical calculation.
Journal of the Optical Society of America A, 2001
Full-wave solutions are given for the single-and double-scatter radar cross sections for two-dimensional random rough surfaces. High-frequency approximations are used for the double-scatter cross sections in order to express them as numerically tractable four-dimensional integrals. The major contributions to the doublescatter cross sections are associated with the quasi-parallel and quasi-antiparallel double-scatter paths. They come from the neighborhoods of specular points. The enhancement of the backscatter cross sections, which is associated with the quasi-antiparallel double-scatter paths, is observed for both the like-and cross-polarized cross sections.
Radio Science, 1993
We present experimental results on the scattering of electromagnetic waves at millimeter-wave frequencies from one-dimensional very rough conducting surfaces with controlled surface roughness statistics. Very rough surfaces are defined as surfaces with rms height and correlation length of the order of a wavelength such that the rms slope is at least unity. It is expected that scattering experiments using these surfaces can provide useful insights since their statistics lie outside the range of validity of the present theories, namely, the Kirchhoff and perturbation theories. Strong backscattering enhancement at different incident angles, both in the transverse electric and transverse magnetic polarizations, are observed experimentally. Numerical calculations based on the exact integral equation method for cylindrical beam wave illumination compare favorably with the experimental results. The agreement between measurements and numerical calculations is good over a wide range of incident angles and for all scattering angles. The close agreement between the experimental results and numerical simulations indicates that this controlled experimental setup can be used to study scattering phenomena from one-dimensional very rough surfaces with different roughness statistics as well as from two-dimensional rough surfaces. INTRODUCTION Recently, there has been interest in the phenomenon of backscattering enhancement, also known as the opposition effect, in the scattering of electromagnetic waves from very rough surfaces. The existence of the enhancement has been verified numerically by several authors [Celli et el., 1985; McGurn and Maradudin, 1987; Soto-Crespo and Nieto-Vesperinas, 1989; Chen and lshimaru, 1990]. Analytical solutions based on the first-and second-order Kirchhoff approximations have been successful in predicting the existence of backscattering enhancement for very rough perfectly conducting, dielectric and metallic surfaces [C hen and lshimaru, 1990]. Experimental verifications of the backscattering enhancement of scattered light from metallic rough surfaces have also been reported independently by several authors [O'Donnell and Mendez, 1987; Haner and Menzies, 1989; Gu et ai., 1989; Kim et al., 1990]. Most of the recently reported experiments are for surfaces in which either the statistics of the surfaces are known ap
On backscatter from spatially varying surfaces
1972
This paper deals with the theory of radar backscatter from rough (spatially varying) surfaces. An integral equation developed by Kerr to describe the radar backscatter from a perfectly conducting surface is applied to non-smooth surfaces. The results are compared with those obtained by Beckmann as well as those obtained by Wright. Differences between the three solutions are discussed.
Exact multiple scattering of waves from random rough surfaces
Optics Communications, 1979
The exact multiple scattering theory of waves scattered from a random rough surface is presented. We give an iterative series for the mean scattered intensity (I(Q)) for all order in the statistics. We show that the coherent intens!ty for large correlation distances approaches the value obtained in the Kirchhoff approximation by Beckmann. Also we prove that a "white noise" surface reflects speeularly the whole incident intensity.
Models for Scattering from Rough Surfaces
Electromagnetic Waves, 2011
Electromagnetic Waves 204 modelling scattering of electromagnetic waves from random rough surfaces. We will also define the bistatic scattering coefficient due to the importance of this type of measurement in many remote sensing applications.
Numerical Backscattering Analysis for Rough Surfaces Including a Cloddy Structure
IEEE Transactions on Geoscience and Remote Sensing, 2000
In recent years, the presence of a new type of agricultural surface tillage, used for the sowing of wheat and corn, has been observed with increasing frequency. It illustrates less roughly ploughed soils, with a greater quantity of small clods distributed over the soil surface. In this paper, a new description of such rough agricultural surfaces is proposed. It is based on a composite model, including a classical surface, represented by an exponential correlation function, together with radom cloddy structure. This description enables volumetric structures to be introduced over the soil's surface. A numerical moment modelling method, based on integral equations, is used to evaluate the contribution of clods to the radar backscattering behaviour of agricultural surfaces. It is found that the presence of clods explains the very small correlation lengths which are often found in cloddy agricultural fields. The classical approach, in which the surface is described by a correlation function only, based on two statistical parameters, rms height and correlation _ length, overestimates the backscattering coefficients when compared to an approach that includes the clods. This over-estimation is often observed with real radar data for such fields. _ Our paper is organised as follows: in Section II, the generation of a surface with a cloddy structure is presented. Description of the proposed moment method, discussions and results are provided in Section III. Finally, our conclusions are presented in Section IV. II. Statistics of Soil Surfaces with Cloddy Structure A. Introduction As presented in the three illustrations of figure 1, corresponding to agricultural fields in Orgeval basin [25], we observe in the last years a generalisation of this new tillage of surfaces prepared to sowing. We note the presence of clods with different sizes superposed over soil surface, with different discontinuities in surface profile. As said in introduction, our objective is to propose a new modelling of this type of surface, considering these clods structures. [26] has presented a close approach for rock-strewn surfaces description, with identification of discrete objects for rocks.
Exact multiple scattering of waves from random rough surfaces*1
Optics Communications, 1979
The exact multiple scattering theory of waves scattered from a random rough surface is presented. We give an iterative series for the mean scattered intensity (I(Q)) for all order in the statistics. We show that the coherent intens!ty for large correlation distances approaches the value obtained in the Kirchhoff approximation by Beckmann. Also we prove that a "white noise" surface reflects speeularly the whole incident intensity.
Backscattering enhancement of an electromagnetic wave scattered by two-dimensional rough layers
Journal of the Optical Society of America, 2001
The problem of an electromagnetic wave scattering by a slab with two rough boundaries is solved by a small-perturbation method under the Rayleigh hypothesis. In order to obtain a perturbative development, we use a systematic procedure which involves integral equations called the reduced Rayleigh equations. Then we will show for a dielectric slab deposited on a silver film that the backscattering enhancement can be produced by guided waves which interact with the two rough surfaces.