Scattering analysis of planar electric and magnetic dipoles in multilayered chiral structures

Abstract

Abstract-This paper describes a model for the analysis of multilayered chiral structures containing planar electric and magnetic scattering elements of arbitrary shape, illuminated by an elliptically polarized plane wave. The particular case of a single chiral layer is analyzed and the scattering matrices for single and dual electric and/or magnetic dipole distributions are derived in an original way. As an application, the polarimetric response of a short electric or magnetic dipole is directly obtained from their scattering matrix.Index Terms-Chiral medium, electromagnetic scattering, Green's functions, layered media, radar remote sensing, spectral fields. The problem of electromagnetic scattering and propagation in structures composed of multiple layers of complex media appears often not only in microwave SAR remote sensing (e.g., stratified soil, crop and forest vegetation, snow and ice covers), but also in other diverse applications, such as: microstrip antennas, microwave monolithic integrated circuits (MMIC), printed circuit technology, mobile and wireless communications, medical imaging and diagnosing, geophysical mapping and planetary exploration. The efficient computational analysis of each of these cases requires accurate models that account for the geometric and electromagnetic characteristics of the particular structure under study, as well as for the specific electromagnetic excitation mechanism.For practical PolSAR remote sensing applications, such as image classification and sensor calibration, several models have been developed to properly characterize the electromagnetic scattering of diverse targets [7]. For example, forest canopy models based on the Radiative Transfer and smaller disks (for its leaves). On the other hand, taking into account the effect of multiple scattering from rough surfaces or volumetric interactions is not a simple task. Therefore, for an electrically dense medium, where scatterers are compactly distributed or the radiation frequency is such that the spacing between them is comparable to the wavelength, the fundamental RT assumption of independent scattering from the elements is no longer valid, thus requiring either complex model adjustments or a different model altogether [9].Another important consideration for the accuracy of a PolSAR remote sensing model is the dielectric properties of the media that constitute each layer. Specialized literature reveals a variety of such properties, for instance: natural media such as rocks, snow, and certain types of soil can not usually be considered homogeneous [10]. Also, scattering from natural terrain cover can be strongly Among the several different parameters used in the literature for polarimetric target characterization, the scattering matrix, which combines both polarimetric and electromagnetic properties of a given target, plays an important role. Once the scattering matrix for a given target is accurately determined, other polarimetric target descriptors (e.g., its polarimetric response, radar cross section, entropy, ani...