Microstrip with dielectric overlay: variational analysis and validation

A variational technique for the analysis of microstrip with dielectric overlay/cover in the Fourier transform domain is investigated with special reference to the strip thickness dependence. The effective permittivity calculated for different overlay thicknesses and permittivities indicates a mode change from quasi-TEM to TEM as the effect of strip width disappears in agreement with full wave spectral domain analysis. Experimental data on multilayer microstrip effective permittivity and numerical results are found to agree for various microwave bulk materials. Based on this software, with the advantage of easier implementation and faster computation a method has been suggested to determine the microwave permittivity of the bulk and thick film materials with minimum fabrication complexity