Broadside-Coupled and Broadside Edge-Coupled Stripline-Like Transmission Lines with Anisotropic Substrates

Abstract

An example of a broadside-coupled symmetric strip transmission line embedded in a homogeneous anisotropic dielectric, with principal axes (in the transverse plane) rotated with respect to the xy co-ordinate axes, is analysed using the spectral-domain technique under the quasi-static approximation. Comparison of the final capacitance formula with that of a corresponding isotropic structure derived using the two-wire transmission line analogy and identification of an admittance parameter leads to generalization of the capacitance expression for a class of symmetric broadside-coupled lines. Similar approach is used for evolving a general variational capacitance expression applicable to a class of broadside, edge-coupled lines. Numerical results are presented on the characteristic impedances and effective dielectric constants for some of the typical transmission structures with anisotropic substrates having principal axes in the transverse plane either aligned or rotated with respect to the xy coordinate axes.

Indexing terms:

• Coupled planar transmission lines
• anisotropy