Closed-form asymptotic extraction method for coupled microstrip lines

The effective dielectric constants of a symmetric coupled microstrip line operating in the dominant mode are solved by using a closed-form formula of the asymptotic part of the impedance matrix elements. Using this asymptotic closed-form solution, the finite upper limit for numerical integration in the evaluation of the impedance matrix elements is significantly reduced. This results in improved computational efficiency for determining the /spl epsiv//sub reff/ of a coupled microstrip line while retaining a good accuracy compared to the conventional spectral domain approach (SDA).