A Study on Imbalance Component and EM Radiation from Asymmetrical Differential-Paired Lines with U-Shape Bend Routing

摘要

Recently, differential-signaling techniques have been widely used in digital electronics devices in order to suppress electromagnetic interference (EMI). To provide the basic considerations and establish the method for predicting the imbalance components and EM radiation from practical differential-paired lines, this paper attempts to identify and quantify the imbalance components and EM radiation from asymmetrical differential-paired lines with U-shape bend equi-distance routing. Although the geometric length of each line is the same, the imbalance component and EM radiation increased and cannot be suppressed completely as the distance between bend routing regions ana length of U-shape bend region become wider. The dominant factor of generation of imbalance component of the model under study is difference of the far-end cross-talk due to the asymmetrical geometry. The physics based model is constructed with an equivalent circuit model to calculate current distribution, and radiation model based on Hertzian dipole antenna. The frequency response of EM radiation from an asymmetrical differential-paired lines can be identified using our proposed model. This study has successfully established a basic method to effectively predict EM radiation from practical differential-paired lines.