Abstract-In this paper, we present numerical simulations and indoor bistatic scattering measurements on scaled targets. The targets are vertical and/or tilted dielectric parallelepipeds representing the main forest elements (tree-trunks and primary branches) at VHF and low-UHF frequencies. They are placed above an aluminum circular plate to simulate a flat ground. The measurements have been conducted in the anechoic chamber of the "Centre Commun de Ressources Microondes" (CCRM) in Marseille, France. A 3D forest scattering model using a Method of Moments (MoM) is deployed to simulate the electric fields scattered by these targets. Two radar geometric, azimuthal and zenithal, bistatic configurations with special attention to the specular direction have been considered. Simulation results and experimental data are confronted for both V V -and HH-polarizations in order to evaluate the accuracy of our model. We have obtained a very good agreement between theoretical and experimental scattered fields for both the magnitude and phase.
This paper focuses on the two domain decomposition methods, the subdomain decomposition iterative method (SDIM) and the characteristics basis function method (CBFM), combined with adaptive cross approximation (ACA) to compute the normalized radar cross section (NRCS) from a perfectly conducting two-dimensional (2D) randomly rough surface. The 3D electromagnetic problem is solved from the electric field integral equation discretized by the Galerkin method of moments with the Rao–Wilton–Glisson basis functions. In addition, a parametric study versus the number of blocks, the number of overlapping edges, the thresholds of recompressed ACA (RACA; ACA combined with two QR decompositions and truncated by a SVD procedure, also named ACA-SVD or ACA-TSVD), and the parameters inherent to the CBFM is investigated. The complexity of the two methods is also addressed.
The Sub-domain Decomposition Iterative Method (SDIM) is presented to solve efficiently a large linear system obtained by sampling the boundary integral equations from the Method of Moments. Then, this new technique is tested on the electromagnetic scattering problem from a large highlyconducting one-dimensional rough sea surface. The diagonal blocks are the local impedance matrices corresponding to the geometry sub-domains while the off-diagonal blocks are the coupling matrices describing the interaction between two different sub-domains. The principle of SDIM is to invert the impedance matrix by blocks reducing significantly the complexity in comparison to a direct LU inversion of the whole impedance matrix. In addition, to accelerate the matrix-vector products and to reduce the memory requirement, the Adaptive Cross Approximation (ACA) is applied to compress the sub-domain coupling matrices. For microwave frequencies, the results show that SDIM converges rapidly and faster for the TM polarization. Moreover, the mean compression ratio of ACA is of the order of 98%, which makes this method very efficient.Index Terms-Electromagnetic scattering by rough surfaces, Method of Moments, Adaptive Cross Approximation, Iterative methods.
0018-926X (c)
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