CHARACTERIZATION OF SINGLE AND COUPLED MICROSTRIP LINES COVERED WITH PROTECTIVE DIELECTRIC FILM

In this paper, we presented an analysis of single and coupled microstr ip lines covered with protective dielectric film which is usually used in the microwave integrated circuits. The method employed in the char acterization is called partial-boundary element method (B-BEM) The p-B EM provides an efficient means to the analysis of the structures with multilayered media or covered with protective dielectric film. The num erical results show that by changing the thickness of the protective d ielectric films such as SiO2, Si and Polyimide covered on these lines on a GaAs substrate, the coupled microstrip lines vary within 10% on t he characteristic impedance and within 25% on the effective dielectric constant for the odd mode of coupled microstrip line, respectively, i n comparison with the structures without the protective dielectric In contrast, the single microstrip lines vary within 4% on the characteri stic impedance and within 8% on the effective dielectric constant, res pectively. The protective dielectric film affects the odd mode of the coupled lines more strongly than the even mode and the characteristics of the single microstrip lines.