Electromagnetic plane wave scattering from periodically loaded cylinders and doubly periodic slabs

Abstract

Periodic structures are of great importance in the design of antenna and radome systems, and also find many applications in the area of low observability. In this thesis, two important geometries are investigated, namely, structures which are periodic along one axis and finite along the other two axes, or periodically loaded cylinders, and structures which are periodic along two axes and finite along the third axis, or doubly periodic slabs.

The periodical cylindrical geometries, investigated in this thesis, consist of homogeneous dielectric cylinders, which are periodically loaded with perfectly conducting, narrow strips. These strips are oriented either parallel or perpendicularly with respect to the cylindrical axis. An algorithm is presented, which allows for the analysis of the oblique plane wave scattering from arbitrarily loaded cylinders. In addition, an algorithm is proposed for designing strip loadings, which reduce the cylinder Radar Cross Section (RCS). This algorithm is based on the combinatorial optimization method of simulated annealing. It is shown that, using this method, strip configurations can be designed which simultaneously reduce the RCS of the dielectric cylinder for several observation angles.

The doubly periodic structures, investigated in this thesis, are composed of arbitrarily interconnected surfaces and wires, which are either perfectly conducting or characterized by a resistive boundary condition. Integral equation formulations are proposed for analyzing the plane wave scattering from free standing periodic slabs, as well as slabs which are embedded in a stratified medium. Several techniques for evaluating the periodic Green's function are investigated and their numerical efficiencies compared. In addition, a method is presented for analyzing the scattering from periodic wire grids whose cell sizes are small compared to the wavelength. These techniques are applied to the analysis of a variety of structures, including plate and honeycomb geometries, wire meshes which contain helical elements, and combined plate-wire structures.