STUDY OF THE DISPERSION CHARACTERISTICS OF PLANAR CHIRAL LINES

This paper analyzes the dispersion characteristics of the fundamental modes of some basic chiral planar transmission lines: microstrip, slot -line, coplanar waveguide (CPW), and a coupled microstrip line, includ ing the possible frequency dependence of the chiral parameters. The di spersion characteristics are computed after finding the zeros of the d eterminantal equation resulting from the application of the Galerkin m ethod in the spectral domain. Because of the biisotropic nature of the substrate, a 4 x 4 matrix differential equation has been solved to ob tain the spectral dyadic Green's function (SDGF). This function will b e explicitly obtained in terms of a closed-form 4 x 4 transition matri x that relates the transverse electromagnetic fields at the upper and lower interface of the chiral substrate. This fact is key to developin g fast computer codes since it avoids numerical matrix exponentiations . The numerical results have shown that the chiral nature of the subst rate basically adds an additional parameter to control the propagation characteristics of the analyzed lines and, in general, makes the line s more dispersive, showing even resonant-like behavior.