A Common-Mode Suppression Filter for Improving Differential Signal Integrity Based on Short Stubs and Defected Ground Plane

A compact filter design for common-mode (CM) noise suppression in high-speed differential signals is proposed and validated on a six-layer printed circuit board (PCB). The filter is implemented by striplines coupled with two meaned open stubs and ground plane patterned two T-shaped slots. As an example, a prototype is fabricated and the experiment result proves that it can achieve CM noise suppression over 10dB from 9.24 to 12.70 GHz with a fractional bandwidth of 37.4%. In addition, the structure can effectively improve the signal integrity of high-speed differential signals while realizing common mode noise suppression.