Abstract: The present invention is a multi-frequency antenna device comprising a first electrode layer and a second electrode layer disposed on a first surface of an insulating substrate, wherein the second electrode layer is located outside periphery of the first electrode layer. A third electrode layer is disposed on a second surface of the insulating substrate, and the first surface and the second surface are separated by the insulating substrate. A conductive element penetrates the insulating substrate and is connected to the first electrode layer. A groove is disposed on a side surface and/or the second surface of the insulating substrate, and a projection of the groove on the first surface completely or partially overlaps the second electrode layer. An effective dielectric constant between the second electrode layer and the third electrode layer is changed through arrangement of the groove to adjust a resonance frequency generated by the second electrode layer.

Abstract: The present invention is a multi-frequency antenna device comprising a first electrode layer and a second electrode layer disposed on a first surface of an insulating substrate, wherein the second electrode layer is located outside periphery of the first electrode layer. A third electrode layer is disposed on a second surface of the insulating substrate, and the first surface and the second surface are separated by the insulating substrate. A conductive element penetrates the insulating substrate and is connected to the first electrode layer. A groove is disposed on a side surface and/or the second surface of the insulating substrate, and a projection of the groove on the first surface completely or partially overlaps the second electrode layer. An effective dielectric constant between the second electrode layer and the third electrode layer is changed through arrangement of the groove to adjust a resonance frequency generated by the second electrode layer.