US Patent 7965521 Electromagnetic bandgap structure and printed circuit board

An electromagnetic bandgap structure and a printed circuit board that can solve a mixed signal problem between an analog circuit and a digital circuit are disclosed. In accordance with an embodiment of the present invention, the electromagnetic bandgap structure can include a first metal layer; a first dielectric layer, stacked in the first metal layer; a metal plate, stacked in the first dielectric layer; a via, connecting the first metal layer to the metal plate; a second dielectric layer, stacked in the metal plate and the first dielectric layer; and a second metal layer, stacked in the second dielectric layer. Here, a hole can be formed on the metal plate. With the present invention, the electromagnetic bandgap structure can lower a noise level more within the same frequency band as compared with other structures having the same size.