A Study of Estimating the Common-Mode Radiation from a Cable Attached to a Metallic Box by Using the Simple Dipole Antenna Model

• Main Authors: Yang, Ting-Sung, 楊廷崧
• Other Authors: Lin, Jiun-Hwa
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/c86778

碩士 === 國立臺灣海洋大學 === 電機工程學系 === 106 === This thesis proposes a method of predicting the far-field radiation from cables attached to a conducting enclosure at the early stage of the design and development phase without using an EMI chamber. The method combines an equivalent dipole model approximating with sinusoidal current distribution and Common-mode current measurement at some specified locations on the cable. First, we use CST Microwave Studio to simulate the whole setup mentioned above to obtain the far-field radiation as the measurement data and to extract the current distribution on the cable for further analysis. By using the image method, we approximate the conducting enclosure with a cable attached to by a dipole model, and introduce current images to take the ground into account. The proposed model is examined by comparing the field data by CST and that from the far-field integral with the current distribution by CST. At the same time, we also observe the change of CST electric field and far field formula by changing the observation height. In practice, the current distribution along the cable cannot be obtained everywhere, but CM current can be measured at a couple of points by the current probe, and the measured current acts as the amplitude of an assumed sinusoidal distribution. This approach results in simple analytical formulas to evaluate far field components, which greatly reduces time and cost by a semi-anechoic solver or by real measurement in the anechoic chamber. In the model of cable attached to a metallic box to the ground, the resonant-mode electric field value is very close to the CST electric field value. Even if the observation height is changed, the two are also very similar. Detailed formulas will be proposed in this paper.