Characteristic impedance of dielectric-filled slotted coaxial transmission line

A solution is presented for the determination of the impedance of slotted dielectric-filled transmission lines of the type that could be formed from semi-rigid coaxial cable, and theoretical results are compared with measured values. The solution is a composite one: over the region of greatest impedance variation, a method involving the conformal transformation of the slotted line to microstrip geometry is used, and a matchedexponential function s used for the remaining part. The experimental method for finding the line impedance values, which is generally useful as it can be applied to any type of transmission line of unknown phase velocity, is also presented.