Shielding Effects in Thin-Film Integrated Circuits

The shielding effect of a thin (or thick) film ground plane on two film conductors has been theoretically investigated by viewing the problem as that of determining the scattering matrix coefficients of a microstrip directional coupler in terms of various transmission-line parameters. The effect of resistive losses in the film conductors and ground plane are considered and methods of systematically determining all transmission parameters have been evolved. Recently published equations for the design of coupled microstrips are used to determine pertinent transmission-line parameters. These results can serve as a guide to designers of thin-film integrated circuits, wherein undesired coupling levels can be predicted and optimum circuit layouts can be determined.