Abstract:
An electronic device may be provided with shared antenna structures that can be used to form both a near-field-communications antenna such as a loop antenna and a non-near-field communications antenna such as an inverted-F antenna. The antenna structures may include conductive structures such as metal traces on printed circuits or other dielectric substrates, internal metal housing structures, or other conductive electronic device housing structures. A main resonating element arm may be separated from an antenna ground by an opening. A non-near-field communications antenna return path and antenna feed path may span the opening. A balun may have first and second electromagnetically coupled inductors. The second inductor may have terminals coupled across differential signal terminals in a near-field communications transceiver. The first inductor may form part of the near-field communications loop antenna.
Abstract:
An electronic device may include a housing and four antennas at respective corners of the housing. Cellular telephone transceiver circuitry may concurrently convey signals at one or more of the same frequencies over one or more of the four antennas using a multiple-input multiple-output (MIMO) scheme. In order to isolate adjacent antennas, dielectric-filled openings may be formed in conductive walls of the housing to divide the walls into segments that are used to form resonating element arms for the antennas. If desired, first and second antennas may include resonating element arms formed from a wall without any gaps. The first and second antennas may include adjacent return paths. A magnetic field associated with currents for the first antenna may cancel out with a magnetic field associated with currents for the second antenna at the adjacent return paths, thereby serving to electromagnetically isolate the first and second antennas.