A CAD MODEL FOR MICROSTRIPS ON R-CUT SAPPHIRE SUBSTRATES

Simple and correct formulas are derived for calculation of an effectiv e isotropic dielectric constant, which characterizes the wa,e propagat ion in microstrip lines on anisotropic substrates made of r-cut sapphi re crystals. The r-plane is extensively used for epitaxial growth of h igh-T-c superconductor YBa2Cu3O7 films as applied to microwave integra ted circuits. In contradistinction to previous models de,:eloped for z -cut sapphire, the nondiagonal dielectric permittivity tenser of r-cut sapphire is used. The effective dielectric constant of a microstrip l ine on r-cut sapphire substrate is found as a function of the strip-li ne geometry and the orientation of the crystallographic axes with resp ect to the symmetry plane of the microstrip line. (C) 1994 John Wiley & Sons, Inc