New formula for effective dielectric constant in multi-dielectric layer microstrip structure

A simple expression of effective dielectric constant for microstrip on a multi-layered substrate is derived with the quasi-TEM assumption and the superposition of partial capacitance. Our method for a single-layer substrate provides difference within 2.32 percent compared to full-wave simulation. For the double layer case, our results are less than 2.2% in difference with an enhanced spectral domain technique and 1.6% with a variation method.