Computation of the RCS of a complex BOR using FEM with coupled azimuth potentials and PML

An efficient finite element method (FEM) to compute scattering from a complex body of revolution (BOR) is discussed. The BOR is composed of perfect conductor and impedance surfaces and arbitrary inhomogeneous materials. The FEM equations are developed using the coupled azimuth potential (CAP) formulation. The FEM mesh is truncated with a perfectly matched layer (PML) in cylindrical coordinates. The use of PML in cylindrical coordinates avoids the wasted computation which results from a spherical mesh boundary with an elongated scatterer. The FEM equations are solved by ordering the unknowns with a reverse Cuthill-McKee algorithm and applying a banded-matrix solution algorithm. Numerical results are presented and compared to exact results and measurements and to results from a previous FEM algorithm which uses edge-based vector basis functions to expand the transverse field components and node-based scalar basis functions to expand the angular component. Problems associated with the CAP formulation are discussed and demonstrated through numerical examples.