A Novel Compact Dual-Functional Circuit With Differential-Mode Equalization and Broadband Common-Mode Suppression Using Patterned Ground Plane

A new passive differential-mode equalizer (DME) equipped with the function of common-mode (CM) suppression is proposed by using differential shunt stubs (DSSs) and patterned ground structure (PGS). The DSS is mainly responsible for generating the high-pass response in differential mode to achieve the equalization effect with a data rate of up to 10 Gbps, while the PGS is responsible for creating the wideband CM suppression from 2 GHz to more than 10 GHz. The equivalent circuit model is constructed and the frequency-domain analysis is applied to calculate the even-mode and odd-mode responses. The calculated responses are validated and then used to solve the approximated resonant frequencies and cut-off frequency of the CM response analytically. Additionally, time-domain eye simulation, full-wave simulation, and measurement are performed to verify the effectiveness of differential-mode equalization and wideband CM suppression. Most crucially, this proposed circuit not only provides better performance on signal integrity, but also features the most compact size in a 2-layer printed circuit board (PCB) and the lowest frequency 2.1 GHz of the CM stopband, in contrast to the previous works.