Patent attributes
An electronic device may have wireless circuitry with antennas. An antenna resonating element arm for an antenna may be formed from peripheral conductive structures running along the edges of a device housing. The peripheral conductive structures may form housing sidewalls. A slot may be machined into a metal housing that separates the housing sidewalls from a planar rear housing portion that forms a ground for an antenna. The slot may be filled with plastic filler. A parasitic antenna resonating element arm that supports an antenna resonance at high band frequencies may be embedded within the plastic filler. The parasitic antenna resonating element may be formed from a portion of the planar rear housing portion.