An efficient approach for reflectivity and coupling computation in an abruptly ended planar layered waveguide using modified formulation of CGF-RFFM

An efficient method for computation of surface wave (SW) reflectivity and coupling in an abruptly ended planar layered waveguide is presented. Using characteristic Green's function (CGF) technique, the original structure is approximated by a separable structure. Then by applying rational function fitting method (RFFM) a uniform and closed-form expression of spatial Green's function for separable structure is derived. Having a full wave solution of the original structure, an optimization problem is defined to find the reflection coefficients of SW modes. Unlike the previous presented CGF based method called CGF-complex images (CI), CGF-RFFM leads to easy incorporation of radiation modes effects in the optimization step and more accurate results consequently. The CGF-RFFM derivation is also modified to incorporate the coupling matrix of SWs to obtain the coupling coefficients. Simple implementation, high accuracy as well as generality of the method are the main advantages of the proposed method. Excellent agreements with rigorous methods are illustrated in several examples.