Characteristic current decomposition for RCS analysis

Summary form only given. We study the scattering of electromagnetic waves from a bounded perfectly electrically conducting (PEC) obstacle. Given an incident electromagnetic field, the determination and computation of the induced electric currents, defined on the surface of the object, is now a rather common task. Once these are known, the scattered electromagnetic fields can be simply derived, and then their behavior far from the object which leads to its radar cross section (RCS). In order to control or to optimize the RCS, it is crucial to determine which part of the induced current is mainly responsible for the radiation at infinity. We try to address this issue by focusing on the scattering operator S. In the PEC case, where there is no damping, this operator is known to be unitary. In an appropriate framework, this operator can be explicitely diagonalized, using a Cayley transform, leading to an orthogonal set of far fields. The idea is then to project the scattered fields on this "eigenfield basis". Moreover, the related currents are also studied. We recover this way the characteristic currents of the obstacle. We illustrate numerically this characteristic current decomposition in the case of a general 3D object, and apply it to its RCS analysis. This way, the part of the induced current mainly responsible for the radiation in a given direction can be identified.