CEM for Radar Cross Section Application

Abstract

Configurations of interest for RCS application are described and the relative merits of alternative approaches to compute these configurations are discussed. These considerations led to the choice of the hybrid finite element integral equation formulation which is the basis of the SWITCH code. The essential details of the derivation of SWITCH are presented along with numerical assumptions that are inherent in this approach and computational electromagnetics (CEM) in general. To alleviate the degree of uncertainty resulting from the above discussion, a number of comparisons of SWITCH computations with canonical solutions and measured benchmarks are presented. These comparisons include a sphere containing anisotropic material and the Electromagnetic Code Consortium VFY218 fighter benchmark.

In addition to the ability to accurately compute relevant configurations, there is the requirement that the computer memory and running time be acceptable. Efforts that are directed at running time and memory reduction for dense matrices are the AIM procedure, FMM, Elegant Mathematics’ LRA-CDENSE solver, and INTEL’S Turbo Solver. The role AIM and FMM have in our hybrid approach will be presented as will be results using LRA-CDENSE. The status of bringing sparse solver expertise into the SWITCH effort will also be discussed.

The previously described material is of an overview and review nature; however, background material in the derivation of SWITCH is presented in a manner that facilitates the introduction of new materials. A new approach which reduces storage requirements is presented for the decomposition of duct RCS computation into segments which can be computed with a finite element approach. This work is a natural extension of previous work by others that treats each segment using integral equations. Finally, a derivation for combining a first principle method such as SWITCH with XPATCH is given which uses some of the ideas previously discussed as well as new ones. This combination of a first principle method (not SWITCH) with XPATCH has already been incorporated in an existing code; however, the derivation presented here can enhance theoretical understanding.