Reduction of electromagnetic radiation from power and ground layers using capacitors

Reduction of electromagnetic radiation using capacitors has been studied for power and ground layers in multilayer printed circuit boards. Capacitors placed near the board edges decreased the electromagnetic radiation from the power and the ground layer when they were arranged with an appropriate spacing. However, they activated another radiation noise. It was found that capacitors near ICs were effective to reduce the other noise. By placing an appropriate capacitance for the edge capacitors and for the near-IC capacitors, the electromagnetic radiation from the power and the ground layer was reduced drastically without exciting the other noise.