Generalized microstrip on a dielectric sheet

A procedure is described for arriving at a close approximation to the capacitance between symmetrically placed conducting strips, possibly of different widths, on opposite sides of a dielectric sheet. The procedure is based on static methods, following K.G. Black and T.J. Higgins (1955) for total capacitance of the structure with vacuum dielectric everywhere, and using H.A. Wheeler's (1964) method for determining the series component of dielectric capacitance. Dielectric polarization is included while refraction at the vacuum/dielectric boundary is ignored in the method; its effect is subsequently shown to be small. The derived equations are valid for all finite impedance, all values of relative dielectric constant, and all conductor widths. The maximum absolute error is estimated to be O(0.001Z'), where Z' is the impedance of a generalized microstrip on a dielectric sheet.<
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