Dispersion characteristics of optically excited coplanar striplines: comprehensive full-wave analysis

A comprehensive full-wave formulation to evaluate the dispersion and losses for coplanar striplines on substrates of finite and infinite thicknesses is presented. The loss mechanisms incorporated in the analysis are substrate losses and dielectric material losses. The method of N.K. Das and D.M. Pozar (1987) is generalized to include a complex propagation vector and can be used over a wide frequency range. A large range of line dimensions can also be handled, limits being set by the accuracy of the moment method. Metal losses can also be incorporated into this analysis by applying the appropriate boundary conditions for lossy metal. Analytically, the excitation of substrate modes is shown to correspond to the occurrence of the poles of the Green´s function in the reaction integrals. Results of the full-wave analysis are in good agreement with those obtained by established theory