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Practical Design Methodology of Mode-Conversion-Free Tightly Coupled Asymmetrically Tapered Bend for High-Density Differential Wiring
Chenyu WANG Kengo IOKIBE Yoshitaka TOYOTA
IEICE TRANSACTIONS on Communications
Publication Date: 2021/03/01
Online ISSN: 1745-1345
Type of Manuscript: PAPER
Category: Electromagnetic Compatibility(EMC)
differential transmission lines, mode-conversion, high-density wiring, asymmetric tapers, design methodology,
Full Text: FreePDF(1.3MB)
The plain bend in a pair of differential transmission lines causes a path difference, which leads to differential-to-common mode conversion due to the phase difference. This conversion can cause serious common-mode noise issues. We previously proposed a tightly coupled asymmetrically tapered bend to suppress forward differential-to-common mode conversion and derived the constraint conditions for high-density wiring. To provide sufficient suppression of mode conversion, however, the additional correction was required to make the effective path difference vanish. This paper proposes a practical and straightforward design methodology by using a very tightly coupled bend (decreasing the line width and the line separation of the tightly coupled bend). Full-wave simulations below 20GHz demonstrated that sufficient suppression of the forward differential-to-common mode conversion is successfully achieved as designed. Measurements showed that our design methodology is effective.