A novel common-mode filter for multiple differential pairs with low crosstalk and low mode conversion level

In this paper, a two-pair common-mode filter is proposed to solve the crosstalk and mode conversion problem of conventional ones in multi-pair form, such as USB3.0 and PCIExpress II. Coupling of the two differential pairs is obviously reduced by a shielding ground plane between them. Moreover, mode conversion problem resulted from asymmetry is also solved. Some simulations have been done to prove the good signal integrity over gigahertz bands brought by the proposed structure, including low loss and distortion of differential mode, a deep transmission zero to suppress common-mode noise, and lower crosstalk and mode conversion level.