On the calculation of the electrical properties of precision coaxial lines

Practical examples of air lines are slightly inhomogeneous. We give an approach for the calculation of such an air line being exclusively based on a) geometrical parameters and b) material parameters. We show that-within the limits of actual deviations of high-precision air lines-the impact of the diameter variation is by far stronger than an excentrically placed inner conductor or a deformed cross section. We find that, from a practical point of view, the conductivity of the air line conductors is the most sensitive parameter. The resulting electrical behavior of the real air line is slightly reflective, i.e., it may no longer be described by a scalar transmission factor. A simple formula for its equivalent electrical length and some test relations for the validity of this formula are given.