Characteristic impedance of elliptic cylindrical strip and microstriplines filled with layered substrate

A method of analysis of elliptic cylindrical strip and microstriplines based on a TEM-wave approximation is presented. Green´s function is used to formulate the problem, which is to obtain a variational expression for the capacitance of the general case of an elliptic stripline with multilayered dielectric boundaries. Expressions for characteristic impedance and effective dielectric constant are derived for a very thin strip, which is the simplest case in planar analysis. Numerical results for characteristic impedance and effective dielectric constant are presented for such striplines with different dielectric media on the two sides of the strip, and also for microstriplines of similar cross-section. A discussion on the effect of the warpage is also presented.