Abstract. The method presented here uses two independent series expansions of the charge distributions over the strip conductor surfaces in terms of Chebychev's polynomials. The charge density behaviour near the strip edges is taken into account. The charge over the strip side walls is neglected. For the effective dielectric constant of a microstrip line covered with a dielectric plate, the computed correction arising from the finite strip conductor thickness and the air gap turns out to be significant in nondestructive permittivity measurement.

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