Man-made Scatterers Research Articles

On the use of virtual ground scatterers to localize double and triple bounce scattering mechanisms for bistatic SAR

In Radar remote sensing, the electromagnetic (em) modeling of scattering contributions from natural or man-made scatterers has often to deal with coupling scattering mechanisms due to the underlying reflecting surface (ground or water). For the monostatic configuration, this contribution is commonly associated with the so-called double bounce scattering mechanism, which is also known to be located in synthetic aperture radar (SAR) images at the vertical projection of the scatterer onto the ground. To explore this phenomenon in the more general case of bistatic SAR but also for triple bounce scattering, a new formalism using virtual scatterers is introduced in this paper. Based upon image theory and on far-field assumption, these virtual points are defined by simple interaction scatterers located on the reflecting surface, and involving the same traveling wave path than the considered scattering mechanism. Depending only on the incidence and scattering angles, elegant formulae in their simplicity are highlighted to construct these fictitious scatterers. The resulting reduction of multiple to simple interaction scattering mechanisms simplifies the finding of their location within bistatic SAR images, generalizing thereby migration effects associated to coupling mechanisms in the bistatic configuration.

Capability Assessment of Fully Polarimetric ALOS–PALSAR Data for Discriminating Wet Snow From Other Scattering Types in Mountainous Regions

This paper examines the capability assessment of fully polarimetric L-band data for the snow and nonsnow-area classifications. The data sets used are the fully polarimetric Advanced Land Observation Satellite-Phased Array-Type L-Band Synthetic Aperture Radar data, optical Advanced Land Observing Satellite (ALOS)-advanced visible and near-infrared radiometer-2 data close to the radar acquisition, and environmental satellite-advanced synthetic aperture radar data. Several parameters are used to discriminate the snow-covered areas from nonsnow-covered areas in the Indian Himalayan region, including backscattering coefficients, the ratio of cross/copolarized backscattering power and polarization fraction (PF) value. Supervised classification schemes are employed using polarimetric decomposition methods based on the complex Wishart classifier. The accuracy of the classification was found to be 97.95% for the Wishart-supervised classification. Among various parameters and methods, it was found that the alternative newly proposed PF scheme, based on the implementation of fully polarimetric synthetic aperture radar data, yielded the best classification result in the absence of the training samples. The PF value has been effective for discrimination of the snow-covered areas from nonsnow-covered areas, debris-covered glacier, and vegetation. The results of this investigation show that L-band fully polarimetric SAR data provide considerable improvement but may not possess the optimal capability to discriminate snow from other inherent natural and man-made scatterers in heavy snow-laden mountainous scenarios, which may require fully polarimetric S-band or C-band PolSAR measurements.

Monte Carlo simulation of the coherent backscattering of electrons in a ballistic system

We study weak localization effects in the ballistic regime as induced by man-made scatterers. Specular reflection of the electrons off these scatterers causes backscattered trajectories to occur, which interfere with their time-reversed path resulting in weak localization corrections to the resistance. Using a semi-classical theory, we calculate the change in resistance due to these backscattered trajectories. We found that the inclusion of the exact shape of the scatterers is very important in order to explain the experimental results of Katine et al.[Superlattices and Microstructures 20 , 337 (1996)].

Optimal Polarization in Bistatic Scattering

The theory of optimal polarization in backscatter by Kennaugh and Graves is extended to the bistatic case to establish that there exist, in general, a set of polarizations characteristic of the features of the scatterer in each scattering geometry, namely optimal polarizations, that could be used as in backscatter to enhance radar detection of man-made scatterers. It will be shown that the optimal polarizations of each antenna used for transmitting in the bistatic scattering geometry and for receiving in the reciprocal scattering geometry are the same, so that both antennas must be tuned to the optimal polarizations for the scatterer. These optimal polarizations can be found by two alternative methods in a two-dimensional complex vector space: (a) as the eigenvectors of a certain pair of positive-definite power scattering matrix and reciprocal power scattering matrix; or (b) as the solutions of a pair of nonlinear equations relating the two sets of eigensolutions in (a). It will also be shown that both methods can be formally cast in a certain four-dimensional complex vector space in the forms that resemble the equations of Graves and Kennaugh in backscatter in a two-dimensional complex vector space.