An empirical formula for the frequency-dependent effective permittivity of a shielded microstrip line

With he concept of a virtual substrate, a closed-form dispersion model, epsilon(eff) (f), for a shielded microstrip line is presented with a maximum error of 3.63% and an average error within 2% for 0.6 less than or equal to W/h(1) less than or equal to 10, 1 less than or equal to epsilon(r1) less than or equal to 20, 0 less than or equal to f less than or equal to 100 GHz, h(2)/h(1) greater than or equal to 2. The model is suitable for the CAD of shielded microstrip structures. (C) 1996 John Wiley & Sons, Inc.