Eigenvalue solutions of the propagation constants of periodically loaded waveguides

In this paper, a new method of finding the propagation constants of one-dimensional periodic structures are presented. This technique places perfect electric conductors (PEC) on the two boundaries of one period of the structure. By formulating the one-period structure in MoM, a generalized eigenvalue problem is derived. The dimension of the matrix is the number of the basis functions on one boundary only and is much smaller then in FEM. This reduces the cost of solving the generalized eigenvalue problem significantly. The Green´s functions of the one-period structure needed in the MoM formulation are generated by FEM. Therefore, the geometry and the material inside the structure can be arbitrary