Electronic device with reduced emitted radiation during loaded antenna operating conditions

摘要

An electronic device may have an antenna for providing coverage in wireless communications bands of interest. The wireless communications bands may include a communications band at a first frequency. The antenna may have a parasitic antenna resonating element that supports a low efficiency resonance. In response to operation of the electronic device in free space, the low efficiency resonance will be located at a second frequency that is greater than the first frequency. In response to operation of the electronic device in proximity to a user's body or other external object, the antenna will be loaded and the low efficiency resonance associated with the parasitic antenna resonating element will shift to the communications band at the first frequency. The antenna may include a resonating element formed on a flexible printed circuit or a dielectric carrier such as a plastic support structure.

主权项

1. An antenna operable in a communications band at a first frequency, comprising:
an antenna ground; antenna resonating element, wherein the antenna resonating element comprises an inverted-F antenna resonating element; a parasitic antenna resonating element, wherein the parasitic antenna resonating element exhibits a resonance at a second frequency greater than the first frequency when the antenna is operated in free space, the resonance shifts to overlap the communications band at the first frequency when the antenna is loaded due to proximity to an object, and the shifted resonance reduces antenna efficiency in the communications band at the first frequency when the antenna is loaded relative to when the antenna is operated in free space; and a flexible printed circuit having opposing first and second surfaces, wherein the antenna resonating element is formed on the first surface and wherein the parasitic antenna resonating element is formed on the second surface.