Method for Determining the Width of Injection Line for Line Injection Method of Cable Transfer Impedance

This paper presents a simple method for determining the width of the injection line when measuring the transfer impedance of coaxial cable by line injection method. In line injection test of coaxial cable, copper strip or copper foil with a certain width is commonly used as the injection line, and the reflection coefficient of the outer circuit is less than 0.1 by adjusting the width of the copper strip or copper foil. In this paper, the outer circuit model of the injection line-coaxial cable shielding layer is established, and the width of the injection line with the different thickness of the dielectric layer and the different relative dielectric constants is obtained by simulation software. Then, the function of the injection line width to the cable radius, the thickness of the dielectric layer and the relative dielectric constants is obtained by curve fitting based on the simulation data. Finally, it is verified that the reflection coefficient of the outer circuit with the injection line width determined by the given function meets the requirements of IEC 62153.4-6 through simulation.