Novel decoupling circuit enabling notable electromagnetic noise suppression and high-density packaging in a digital printed circuit board

This paper describes a novel decoupling circuit comprising magnetic materials and built-in choking coils which makes it possible to significantly suppress noise in a digital printed circuit board (PCB). It is well known that the common-mode current existing in the cables and chassis of digital equipment causes major radio frequency radiation from equipment. We found that the common-mode current in the digital PCB could be substantially reduced by enhancing the decoupling circuit of the DC supply line near the LSIs in the PCB. Experiments confirmed that use of the enhanced circuit greatly reduces the amount of radio frequency radiation emitted from digital equipment under normal circumstances.