Calculation of Common-Mode Radiation from Single-Channel Differential Signaling System Using Imbalance Difference Model

Tohlu MATSUSHIMA  Tetsushi WATANABE  Yoshitaka TOYOTA  Ryuji KOGA  Osami WADA  

IEICE TRANSACTIONS on Communications   Vol.E93-B   No.7   pp.1739-1745
Publication Date: 2010/07/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E93.B.1739
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Advanced Electromagnetic Compatibility Technology in Conjunction with Main Topics of EMC'09/Kyoto)
Category: PCB and Circuit Design for EMI Control
common-mode radiation,  differential transmission line,  imbalance difference model,  guard trace,  

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In a differential transmission line, a large common-mode radiation is excited due to its asymmetry. In this paper, the imbalance difference model, which was proposed by the authors for estimation of common-mode radiation, is extended to apply to the differential signaling systems. The authors focus on a differential transmission line with asymmetric property, which consists of an adjacent return plane and two signal lines which are placed close to an edge of the return plane. Three orthogonal transmission modes, a normal mode, a primary common mode and a secondary common mode, are defined. Among these transmission modes, the secondary common mode is dominant in radiation, and a mechanism of the secondary common-mode generation is explained. The radiated emission which was calculated using the imbalance difference model was in good agreement with that obtained by full wave calculation.