Patent ID: 8514147

Claim:
An antenna device comprising: (i) an electromagnetic bandgap structure comprising unit structures which are cyclically coupled to each other, the electromagnetic bandgap structure providing a high surface impedance in a specific frequency band when viewed in a direction perpendicular to a principal plane of the electromagnetic bandgap structure and blocking transmission of a signal of a noise in a predetermined frequency band when viewed in a direction parallel to the principal plane, wherein the electromagnetic bandgap structure includes a magnetic material portion at least in part, wherein each unit structure has at least one conductive layer, and the magnetic material portion is formed in contact with the conductive layer, wherein the magnetic material portion comprises a ferrite layer formed on an upper surface and/or a lower surface of the conductive layer wherein the ferrite layer comprises a ferrite plating film that has a structure in which crystal phases are arranged with respect to each other to reduce anisotropy dispersion on a basis of exchange coupling between the crystal phases, and wherein the electromagnetic bandgap structure is in a form of a sheet or a plate having a first principal plan which provides a high surface impedance and a second principal plane opposite to the first principal plane; and (ii) an antenna support layer of a dielectric formed on the first principal plane.