Analysis of broadside‐coupled strip lines with anisotropic substrate

Two analytical approaches are presented for broadside‐coupled strip lines with anisotropic substrates. One is based on the quasi‐static approximation which uses the Fourier transformation and the Ritz procedure. the other is based on the rigorous hybrid‐mode formulation, and the frequency dependent solutions are obtained by using the network analytical methods of electromagnetic fields and Galerkin's procedure. Some numerical results are presented for sapphire and Epsilam‐10 substrates. the effect of the inclination of the optical axis is not so large, and the effect of the shift of central axes of strip lines S/W in the odd modes is larger than that in the even modes. the rigorous frequency dependent solutions converge to quasi‐static values at lower frequencies, and the dispersion of the even modes, which cannot be neglected at higher frequencies.