A Gaussian beam (GB) summation representation for rough surface scattering is introduced. In this scheme, the coherent and incoherent scattered fields are described by a phase-space summation of GBs that emanate from the rough surface at discrete set of points and directions. It thus involves stochastic GB2GB scattering matrices for the coherent and incoherent fields, and deterministic GB propagators. It benefits from the simplicity and accuracy of the latter, and can be used in applications involving propagation in complex scenarios comprising inhomogeneous media with rough surface boundaries. The GB2GB matrices are calculated from the statistical moments of the scattering amplitude, which are given either analytically or empirically. An analytical and numerical example for weakly rough surface is presented and discussed. Applications to the more complicated propagation scenario of doubly rough surface waveguide with multiple reflection phenomena will be presented in a follow-up publication.
An original approach to the description of classical wave localization in weakly scattering random media is developed. The approach accounts explicitly for the correlation properties of the disorder, and is based on the idea of spectral filtering. According to this idea, the Fourier space (power spectrum) of the scattering potential is divided into two different domains. The first one is related to the global (Bragg) resonances and consists of spectral components lying within a limiting sphere of the Ewald construction. These resonances, arising in the momentum space as a result of a self-averaging, determine the dynamic behavior of the wave in a typical realization. The second domain, consisting of the components lying outside the limiting sphere, is responsible for the effect of local (stochastic) resonances observed in the configuration space. Combining a perturbative path-integral technique with the idea of spectral filtering allows one to eliminate the contribution of local resonances, and to distinguish between possible stochastic and dynamical localization of waves in a given system with arbitrary correlated disorder. In the one-dimensional (1D) case, the result, obtained for the localization length by using such an indirect procedure, coincides exactly with that predicted by a rigorous theory. In higher dimensions, the results, being in agreement with general conclusions of the scaling theory of localization, add important details to the common picture. In particular, the effect of the high-frequency localization length saturation is predicted for 2D systems. Some possible links with the problem of wave transport in periodic or near-periodic systems (photonic crystals) are also discussed.
In this work, we perform an analysis of a channel for the UHF wave propagation in the city street. The street is modeled as a planar multislit waveguide with screens and slits distributed by a Poisson law. Statistical propagation characteristics in such a waveguide can be expressed in terms of multiple ray fields approaching the observer along a direct ray and the rays reflected by the waveguide walls. The corresponding average field and intensity distributions can be transformed into the sums of modelike solutions using the Poisson summation formula. Numerical examples are presented and compared with the experimental data.Index Terms-UHF radio propagation, urban areas.
We have solved the equation for the two-frequency fourth-order moment of two parallel monochromatic plane waves having different frequencies and propagating through a randomly inhomogeneous medium. The solution procedure uses a two-scale expansion based on the smallness of a new parameter whose magnitude does not depend on the scattering strength. The results are shown to be valid for all values of the scattering parameter. The multidimensional integral expression for the bichromatic correlation was evaluated for a two-dimensional random medium characterized by a Gaussian correlation function. Further simplification was carried out in the strongscattering regime, using asymptotic techniques. It is shown that the bichromatic correlation decreases with the wavelength separation. Its dependence on range is more complicated: Initially it increases with increasing range, only to level off to zero for large enough scattering strength, wavelength separation, and range.
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