Common-mode noise reduction of bended differential lines using meander line structure

Time skew between inner line and outer line is main reason to induce differential to common-mode noise in differential bended lines. To compensate time skew arisen length difference of inner line and outer line, meander line structure was adopted. The increase of time delay for differential signal by mender line structure was verified by simulated results on balanced coupled transmission lines. The meander line structure, having four pair of section 1, and 2, or section 2, and 3 was adopted to inner line of right-angle bended line at both sides, and common-mode noises was reduced about 87 % of that induced by bended lines without meander line structure. From measured results, it was verified that Scd2i were below 20-dB within range of 4 GHz both simulation and measurement, which means the time skew was compensated well with low differential insertion loss within range of 4 GHz both simulation and measurement. The length and width of meander line structure were only 1.2 mm and 1.75 mm, respectively, therefore, it has advantage of size miniaturization.