As the operating frequency of electronic circuits continues to increase, today’s package and printed circuit board designers face more radiation problem than ever before. The control of radiated emissions to make the package comply with radiation constraints is one of the most important aspects of the EMC study. Some "rules-of-thumb" are employed to help the designers to reduce the radiation problems. This
paper presents an investigation on the effects of the 20-H rule and the shielding vias on radiation from printed circuit boards.