Abstract: A removable case may receive an electronic device. A male connector in the case may mate with a female connector in the device. A battery in the case may supply power to the device through the male connector. The electronic device may have an antenna formed from peripheral conductive housing structures and an antenna ground. The antenna may include a slot antenna resonating element. The case may have supplemental antenna structures such as a metal patch that overlaps an end of the slot antenna resonating element to retune the slot antenna resonating element to a desired operating frequency after being detuned by dielectric loading from the case. The supplemental antenna structures may overlap antennas of other types and may include tunable circuitry that is adjusted based on information received from the electronic device.

Abstract: 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. Elongated conductive members may longitudinally divide openings between the peripheral conductive housing structures and the ground. The elongated conductive members may extend from an internal ground to outer ends of the elongated conductive members that are located adjacent to the gaps. Transmission lines may extend along the elongated conductive members to antenna feeds at the outer ends. The elongated conductive members may form open slots that serve as slot antenna resonating elements for the antenna.

Abstract: An electronic device may be provided with wireless circuitry. Control circuitry may be used to adjust the wireless circuitry. The wireless circuitry may include antennas that are tuned, adjustable impedance matching circuitry, antenna port selection circuitry, and adjustable transceiver circuitry. Wireless circuit adjustments may be made by ascertaining a current usage scenario for the electronic device based on sensor data, information from cellular base station equipment or other external equipment, signal-to-noise ratio information or other signal information, antenna impedance measurements, and other information about the operation of the electronic device.

Abstract: Electronic devices may be provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. The antenna structures may form a dual arm inverted-F antenna. The antenna may have a resonating element formed from portions of a peripheral conductive electronic device housing member and may have an antenna ground that is separated from the antenna resonating element by a gap. A short circuit path may bridge the gap. An antenna feed may be coupled across the gap in parallel with the short circuit path. Low band tuning may be provided using an adjustable inductor that bridges the gap. The antenna may have a slot-based parasitic antenna resonating element with a slot formed between portions of the peripheral conductive electronic device housing member and the antenna ground. An adjustable capacitor may bridge the slot to provide high band tuning.

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: Electronic devices may be provided that include radio-frequency transceiver circuitry and antennas. An antenna may be formed from an antenna resonating element and an antenna ground. The antenna resonating element may have a shorter portion that resonates at higher communications band frequencies and a longer portion that resonates at lower communications band frequencies. The resonating element may be formed from a peripheral conductive electronic device housing structure that is separated from the antenna ground by an opening. A parasitic monopole antenna resonating element or parasitic loop antenna resonating element may be located in the opening. Antenna tuning in the higher communications band may be implemented using an adjustable inductor in the parasitic element. Antenna tuning in the lower communications band may be implemented using an adjustable inductor that couples the antenna resonating element to the antenna ground.

Abstract: Electronic devices may be provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. The antenna structures may form a dual arm inverted-F antenna. The antenna may have a resonating element formed from portions of a peripheral conductive electronic device housing member and may have an antenna ground that is separated from the antenna resonating element by a gap. A short circuit path may bridge the gap. An antenna feed may be coupled across the gap in parallel with the short circuit path. Low band tuning may be provided using an adjustable inductor that bridges the gap. The antenna may have a slot-based parasitic antenna resonating element with a slot formed between portions of the peripheral conductive electronic device housing member and the antenna ground. An adjustable capacitor may bridge the slot to provide high band tuning.

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 balance-fed antenna structures that do not have direct paths to ground. The antenna structures may serve as a Global Positioning System (GPS) antenna and may have a dipole structure having a first and second antenna resonating element arms. The antenna structures may include a conductive path that conveys antenna signals between a first feed terminal on the first antenna resonating element arm and a transmission line. The conductive path may overlap with the second antenna resonating element arm such that current flow through the conductive path induces corresponding current flow in the second antenna resonating element arm. The antenna structures may include an impedance matching short-circuit stub path that couples the first antenna resonating element arm to the second antenna resonating element arm. Choke inductors may be used to help block indirect paths from the antenna structures to ground through adjacent circuitry.

Abstract: An electronic device may have wireless circuitry with antennas. An antenna may have an inverted-F antenna resonating element, an antenna ground, and other resonating element structures. A tip of the antenna resonating element and the antenna ground may be separated by a peripheral housing gap filled with plastic. The antenna may be sensitive to capacitance changes induced by the presence of a user's hand overlapping the gap or other portions of the antenna. A hand capacitance sensing electrode may be mounted in the plastic of the gap or elsewhere in the vicinity of the antenna. A transmission line may couple the hand capacitance sensing electrode to the antenna to retune the antenna in the event that the user's hand overlaps the antenna.

Abstract: A removable case may receive an electronic device. A male connector in the case may mate with a female connector in the device. A battery in the case may supply power to the device through the male connector. The electronic device may have an antenna formed from peripheral conductive housing structures and an antenna ground. The case may have a supplemental antenna that restores antenna performance when the device is received within the case. The supplemental antenna may be formed from a monopole antenna resonating element coupled to the antenna ground through the power pin. The monopole element may have a portion that runs parallel to the peripheral conductive housing structures. During operation of the antenna in the electronic device, the supplemental antenna in the case may be indirectly fed by near-field coupling between the supplemental antenna and the antenna of the electronic device.

Abstract: An electronic device may be provided with an antenna. The antenna may have an antenna resonating element and an antenna ground. The antenna resonating element may be formed from peripheral conductive housing structures. An audio jack or other connector may be mounted in an opening in the peripheral conductive housing structures. The audio jack may overlap the antenna ground. Contacts in the audio jack may be coupled to an interference mitigation circuit. The interference mitigation circuit may include capacitors coupled to the ground and inductors coupled between the contacts and the capacitors. Radio-frequency signal blocking inductors may be coupled between the interference mitigation circuit and respective ports in an audio circuit.

Abstract: An electronic device may be provided with an antenna. The antenna may have an antenna resonating element and an antenna ground. An adjustable inductor may be coupled between the antenna resonating element and the antenna ground. An antenna feed may have a positive feed terminal coupled to the antenna resonating element and a ground antenna feed coupled to the antenna ground. The adjustable inductor may have first and second inductors coupled to respective first and second ports of a switch. The switch may have a third port coupled to the antenna ground. A capacitor may have a first terminal coupled to ground and a second terminal coupled to the first inductor at the first port of the switch. An inductor may be coupled between the antenna resonating element and antenna ground at a location between the adjustable inductor and the antenna feed.

Abstract: Electronic devices may be provided that include radio-frequency transceiver circuitry and antennas. An antenna may be formed from an antenna resonating element and an antenna ground. The antenna resonating element may have a shorter portion that resonates at higher communications band frequencies and a longer portion that resonates at lower communications band frequencies. An extended portion of the antenna ground may form an inverted-F antenna resonating element portion of the antenna resonating element. The antenna resonating element may be formed from a peripheral conductive electronic device housing structure that is separated from the antenna ground by an opening. A first antenna feed may be coupled between the peripheral conductive electronic device housing structures and the antenna ground across the opening. A second antenna feed may be coupled to the inverted-F antenna resonating element portion of the antenna resonating element.

Abstract: An electronic device may have an antenna for providing coverage in wireless communications bands of interest. The wireless communications bands may include first, second, third, and fourth communications bands. The antenna may have an antenna resonating element with first, second, and third arms and may have an antenna ground. The antenna ground may be formed form metal housing structures and other conductive structures in the electronic device. The first arm may be configured to exhibit an antenna resonance in the first and third communications bands. The second arm may be configured to exhibit an antenna resonance in the second communications band. The third arm may be configured to exhibit an antenna resonance in the fourth communications band. The third arm may be located between the first arm and the ground. A diagonal crossover path may pass over a return path and may couple the second and third arms.

Abstract: An electronic device may be provided with a housing. The housing may have a periphery that is surrounded by peripheral conductive structures such as a segmented peripheral metal member. A segment of the peripheral metal member may be separated from a ground by a slot. An antenna feed may have a positive antenna terminal coupled to the peripheral metal member and a ground terminal coupled to the ground and may feed both an inverted-F antenna structure that is formed from the peripheral metal member and the ground and a slot antenna structure that is formed from the slot. Control circuitry may tune the antenna by controlling adjustable components that are coupled to the peripheral metal member. The adjustable components may include adjustable inductors and adjustable capacitors.

Abstract: An electronic device may be provided with wireless circuitry. Control circuitry may be used to adjust the wireless circuitry. The wireless circuitry may include antennas that are tuned, adjustable impedance matching circuitry, antenna port selection circuitry, and adjustable transceiver circuitry. Wireless circuit adjustments may be made by ascertaining a current usage scenario for the electronic device based on sensor data, information from cellular base station equipment or other external equipment, signal-to-noise ratio information or other signal information, antenna impedance measurements, and other information about the operation of the electronic device.

Abstract: An electronic device may be provided with wireless circuitry that includes a radio-frequency transceiver circuit and an antenna. The antenna may be a patch antenna formed from a patch antenna resonating element and an antenna ground. The patch antenna resonating element may be formed from a metal patch on a printed circuit board. The antenna ground may be formed from a metal housing having a planar rear wall that lies in a plane parallel to the metal patch. The radio-frequency transceiver circuit may be coupled to the metal patch through traces on the printed circuit and may be coupled to rear wall of the housing through a screw and a screw boss in the housing. Buttons and other electrical components may be mounted on the printed circuit board and may be coupled to control circuitry on the printed circuit board through the metal patch.

Abstract: An electronic device may be provided with wireless circuitry. Control circuitry may be used to adjust the wireless circuitry. The wireless circuitry may include an antenna that is tuned using tunable components. The control circuitry may gather information on the current operating mode of the. electronic device, sensor data from a proximity sensor, accelerometer, microphone, and other sensors, antenna impedance information for the antenna, and information on the use of connectors in the electronic device. Based on this gathered data, the control circuitry can adjust the tunable components to compensate for antenna detuning due to loading from nearby external objects, may adjust transmit power levels, and may make other wireless circuit adjustments.

Abstract: Electronic devices may be provided with antenna structures such as distributed loop antenna resonating element structures. A distributed loop antenna may be formed on an elongated dielectric carrier and may have a longitudinal axis. The distributed loop antenna may include a loop antenna resonating element formed from a sheet of conductive material that extends around the longitudinal axis. A gap may be formed in the sheet of conductive material. The gap may be located under an opaque masking layer on the underside of a display cover glass associated with a display. The loop antenna resonating element may have a main body portion that includes the gap and may have an extended tail portion that extends between the display and conductive housing structures. The main body portion and extended tail portion may be configured to ensure that undesired waveguide modes are cut off during operation of the loop antenna.