US Patent 7943864 Printed circuit board having electromagnetic bandgap structure

In accordance with an embodiment, the printed circuit board, having an analog circuit and a digital circuit includes: a first metal layer and a second metal layer, one of the first metal layer and the second metal layer being a power layer and the other being a ground layer; a third metal layer, layer-built between the first metal layer and the second metal layer; and a mushroom type structure including a via connected to a metal plate, the metal plate being arranged in a space between circuit patterns of the third metal layer.