Coordinate Systems and Alignment Conventions in Bistatic Radar Polarimetry

Abstract

This talk held at the National Key Laboratory of Microwaves Imaging Technology, part of the Institute of Electronics and belonging to the Chinese Academy of Sciences is concerned with the proper formulation of the electromagnetic wave scattering problem from coherent point targets in the general bistatic case which depends on the introduction of the proper coordinate systems. Deficiencies of often used ‘Forward Scattering Alignment (FSA)’ and the ‘Back Scatter Alignment (BSA)’ conventions are pointed out and we attempt to modify these concepts by explicitly introducing the time reversal operation, as proposed by E. Lüneburg. Coordinate systems are used to realize and concretize operator-valued field relations formulated in abstract vector spaces in terms of vectors and matrices in finite-dimensional complex linear vector spaces. Great care must be exercised in choosing the correct coordinate systems and conventions in such a way that the formulations allow a direct application of well-established mathematical theorems to the physical world of the various scattering scenarios. This applies in particular to the formulation of scatter problems using the conventional FSA and the BSA conventions in general bi-static radar polarimetry. This suggestion is also connected with the attempt to recombine the traditional formulations via the radar equation and via the voltage equation, considered to be the two independent cornerstones of radar polarimetry, on an equally cohesive footing.