A New Directional Coupler to Measure the Performances of Noncontact Devices Used for the Reduction of the Shielding Current on Cables

The importance of the sheath current wave such as Sommerfeld's single-wire wave (SSWW) increases in electromagnetic compatibility. In order to measure the reflection coefficient of SSWW equipment under test (EUT) (for example an absorbing clamp), we can use the slotted line method. But this method takes much time and more efforts, because the voltage or current distribution must be measured along the line at a lot of different positions. However, in order to produce a more rapid determination of the reflection coefficient of an SSWW EUT, we have designed an SSWW directional coupler to measure it. In this paper, an improved technique for measuring the -parameters of an SSWW backward coupler is investigated. We present the equivalent circuit model of this coupler and discuss results. The measured -parameters will be used to determine the reflection coefficient of an SSWW EUT. As an application of this technique, a pyramidal foam absorber and an absorbing clamp are used as EUT. The reflection coefficient of the latter is measured twice: first using the slotted line and then with the coupler. A comparison between both results is presented.