Three-dimensional noise current distribution on power and ground planes in printed circuit boards

Radiation noise currents on power and ground planes in multilayer printed circuit boards are shown three-dimensionally, combining the moment method simulation with far electric and near magnetic field measurements. The power and ground layers are modeled into four metal planes, considering the skin effect. The analysis shows that the main noise current flows only on the two facing planes (the inner planes) of the layers in the differential-mode. The current distributions on the inner planes are shown for various resonance modes. Methods of reducing the noise radiation are also discussed.