A mobile device includes a system ground plane and an antenna system. The antenna system includes a dielectric substrate, an antenna ground plane, a radiation element, and at least one feeding element. The antenna ground plane is coupled to the system ground plane. The feeding element is coupled to a signal source. The feeding element is positioned between the radiation element and the antenna ground plane. The feeding element and the radiation element are completely separate from each other. The radiation element is excited by the feeding element by coupling.