Mode Conversion and Common-Mode Noise Reduction Using Periodic Structure Filter

In this article, a 90°-bent differential transmission line using the asymmetric periodic structure filter is proposed. The asymmetry of the periodic structure filter is used to reduce the differential-to-common mode conversion while the frequency response of the periodic structure filter is used to reflect the common-mode noise. As compared with the conventional 90°-bent differential transmission line, the differential-to-common mode conversion is greatly reduced from −3.04 to −20.42 dB while the time-domain differential-to-common mode transmission is greatly reduced from 0.094 to 0.006 V. Besides, the common-mode reflection coefficient is largely increased from −13.72 to −0.94 dB while the time-domain common-mode reflection is largely increased from 0.017 to 0.068 V. Furthermore, the performance of the eye diagram is upgraded, meaning that the signal integrity is improved.