Characteristics of Single and Coupled Microstrips on Anisotropic Substrates

In this paper, the effect of an anisotropic substrate on the characteristics of covered microstrip is presented for single and coupled lines. The Green´s function is obtained in integral and series form for an arbitrary anisotropic substrate. Computer programs based on the method of moments approach [1], [2] are employed and results are presented in graphical form for impedance Z, coupling constant K, and phase velocity v_p as functions of n_x / n_y (the ratio of the substrate indices of refraction). Z, K, and v_p are studied for various w/H, S/H, and B/H ratios where w is the line width (w₁ and w₂ for coupled lines), S is the separation between coupled lines, B is the separation between ground planes, and H is the substrate thickness.