High frequency approximations to multiple scatter by rough surfaces that exhibit enhanced backscatter (original) (raw)
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.
Journal of the Acoustical Society of America, 1989
Earlier results for coherent reflection and incoherent scattering by random distributions of relatively arbitrary bosses on rigid or free base planes [V. Twersky, J. Acoust. Soc. Am. 29, 209-225 (1957); 73, 85-94 (1983)] are applied to rigid and free ellipsoidal bosses with axes large compared to wavelength. The asymptotic procedures used originally for circular cylinders and spheres (1957) and subsequently for elliptic cylinders [J. E. Burke and V. Twersky, J. Acoust. Soc. Am. 40, 883-895 (1966) ] are generalized to triaxial ellipsoids, and results for the corresponding bosses are obtained by the original image method. Illustrative curves exhibit the effects of boss shape and orientation on the coherent reflection coefficients and incoherent differential scattering cross sections per unit area. To facilitate comparison with available low-frequency curves, the same isotropic and anisotropic surfaces were considered as before [R. J. Lucas and V. Twersky, J. Acoust. Soc. Am. 78, 1838-1850 (1985)] and emphasize anisotropic forward (specular) and backscattered effects for applications to sea-air, sea-bottom, and sea-ice pro
Open Journal of Acoustics, 2012
The first-order small slope approximation is applied to model the scattering strength from a rough surface in underwater acoustics to account for seafloor for high frequencies from 10 kHz to hundreds of kilohertz. Emphasis is placed on simulating the response from two-dimensional anisotropic rough surfaces. Several rough surfaces are described based on structure functions such as the particular sandy ripples shape. The scattering strength is predicted by the small slope approximation and is first compared to a well known bistatic method, interpolating the Kirchhoff approximation and the small perturbations model, assuming that the rough interface is isotropic. Results obtained from the two different models are similar and show a higher level in the specular direction than in the other directions. For an isotropic surface, changing the propagation plane gives similar results. Then, SSA, which lets us adapt the structure function of the roughness straight away, is tested trough several anisotropic surfaces. In a longitudinal direction of ripples, the scattering strength is mostly in the specular direction, whereas in the transversal direction of ripples, the scattering strength prediction shows high values for different angular directions. Thus the scattering strength is spread in a very different way strictly related to the particular features of the ripples. Combine our results, indicates the importance of taking into account the anisotropy of a surface in a scattering prediction process, taking into account the positions of the emitter and of the receiver which are naturally significant when predicting scattering strength.
Electromagnetic scattering from multi-scale rough surfaces
Waves in Random Media, 1997
It is shown that the wavelet correlation dimension is a very relevant quantity for the characterization of rough surfaces by remote sensing means. First, the concept of correlation length is generalized to surfaces with wide power spectrum. Second, it is demonstrated that, in the framework of the small-perturbation theory, the wavelet correlation dimension can be retrieved from a knowledge of the backscattered cross section for a discrete set of frequencies.
Backscattering enhancement from a dielectric surface
Journal of The Optical Society of America B-optical Physics, 1991
Using the unitary and reciprocal theory of Brown et al. [Surf. Sci. 136, 381 (1984)], we calculated numerically the differential reflection coefficient for the scattering of an electromagnetic wave from a weakly corrugated, randomly rough dielectric surface. For a one-dimensional surface we did not see enhanced backscattering except when the contribution from single scattering processes was subtracted. For a two-dimensional surface we clearly saw enhanced backscattering in the cross-polarized scattering.