Study of Dispersion Analysis for Various Microstrip Line Configurations Using Finite Difference Method

Abstract

In this paper, we studied about static analysis and losses of microwave isolated single stripline structure using conformal mapping method. Microstrip lines due to presence of two different dielectric boundaries does not support a pure TEM wave. It is assumed that only the fundamental mode will propagate, but the propagation constant, γ, is a non¬linear function of frequency. Due to the presence of two dif¬ferent dielectrics, the fringing fields experience an in-homogenous dielectric leading to a discontinuity on the field. A parameter called effective permittivity (ϵ_eff ) is introduced, which is always lesser than the permittivity of the substrate as the fields exists both in air and the substrate. Due to the non-TEM nature of the fields, the effective permittivity is dependent on the frequency. This is due to the fact that more field lines will penetrate the substrate with increasing frequency thus increasing the effective permittivity.