An improved formalism for FDTD analysis of thin-slot problems by conformal mapping technique

An improved expression of the thin-slot formalism has been proposed to alleviate the gridding of the finite-difference time-domain (FDTD) solution for electromagnetic problems involving narrow slots. By applying the conformal mapping technique, the varying field distribution near the slots is analytically derived and fully cast into a unit FDTD cell with effective permittivity and permeability. As a result, this formalism permits narrow slots to be modeled without reducing spatial grid size, even when the slot gap width is much smaller than a one space grid. The method has been applied to several transmission line problems and the results are compared with traditional FDTD and other thin-slot formalisms. It is verified that the proposed method is easy to implement, numerically efficient, and accurate.