A Development of a Common-Mode FilterUsing an EBG Structure in High Speed SerialLinks

Abstract: As signal speed increases and electronic products become progressively smaller,the risks of electromagnetic radiation and interference are also heightened.Ericsson's SCXB, an Ethernet switch card, experiences exactly this problem,with excessive emission levels probably caused by common-mode noise.In this project, a common-mode lter using the electromagnetic bandgap(EBG) structure has been designed and implemented in the SCXB. Unlikeconventional common-mode lters, the common-mode lter is embedded inthe printed circuit board (PCB) beneath the dierential lines. The eect ofthe common-mode lter is assessed by measuring the insertion loss and thepower radiation of a shielded cable connected to the common-mode lter.A compact common-mode lter using an EBG structure has been proposedin this project and this works eectively at 937.5 MHz. One of the resultsfrom the parametric analysis shows that the common-mode lter is suitableto work in a high frequency range due to the smaller structure and the widerbandwidth range. The common-mode lter is constructed with the PCBfabrication process. No additional components are necessary, although morelayers of the PCB's stack up are required in which to embed the common-mode lter.