Abstract: An electronic device may have peripheral conductive structures and a conductive layer that define edges of a slot element for a slot antenna. The slot element may be configured to cover wireless communications in a 1575 MHz satellite navigation band and 2.4 GHz and 5 GHz wireless local area network bands. A tuning circuit may be coupled across the slot approximately half way across the length of the slot. The antenna tuning circuit may include an inductor coupled in series with a notch filter (in scenarios where the slot is long enough to cover the 1575 MHz satellite navigation band in its fundamental mode) or may include a capacitor coupled in series with a notch or low pass filter. The fundamental mode and one or more harmonic modes of the slot element may cover the satellite navigation and wireless local area network bands.

Abstract: An electronic device housing may have a rear housing wall that forms a metal ground plane. A slot may be formed in the metal ground plane. The slot may have one or more open ends along an edge of the ground plane. A near-field communications loop antenna may overlap the slot. The near-field communications loop antenna may have one or more turns. A current path through the metal ground plane may form one of the turns in the near-field communications loop antenna. The slot may form portions of non-near-field-communications antennas in addition to the near-field communications loop antenna. The slot in the non-near-field-communications antennas may be fed using an indirect antenna feed structure. Components such as a capacitor and inductor may help allow non-near-field communications antenna and the near-field communications antenna to be formed from common portions of the metal ground plane.

Abstract: An electronic device may have hybrid antennas that include slot antenna resonating elements formed from slots in a ground plane and planar inverted-F antenna resonating elements. The planar inverted-F antenna resonating elements may each have a planar metal member that overlaps one of the slots. The slot of each slot antenna resonating element may divide the ground plane into first and second portions. A return path and feed may be coupled in parallel between the planar metal member and the first portion of the ground plane. Tunable components such as tunable inductors may be used to tune the hybrid antennas. A tunable inductor may bridge the slot in hybrid antenna, may be coupled between the planar metal member of the planar inverted-F antenna resonating element and the ground plane, or multiple tunable inductors may bridge the slot on opposing sides of the planar inverted-F antenna resonating element.

Abstract: An electronic device may be provided with a conductive wall. A gap in the wall may divide the wall into first and second segments. A ground may be separated from the wall by first, second, and third slots that form radiating elements for first, second, and third non-near-field communications antennas. First and second conductive structures may be coupled between the wall and the ground. A near-field communications antenna may include a first feed terminal coupled to the first segment and a second feed terminal coupled to the second segment. The antenna may convey signals over a conductive loop path that includes portions of the first and second segments, the antenna ground, and the first and second conductive structures. A differential or single-ended signal transmission line may be coupled to the terminals. Phase shifters may configure the signals to be out of phase at the feed terminals.

Abstract: An electronic device may have conductive housing structures and first, second, third, and fourth slot antennas having respective first, second, third, and fourth slot elements in the conductive housing structures. The third slot element may be interposed between the first and second slot elements and the second slot element may be interposed between the third and fourth slot elements. Switching circuitry may be coupled between a transceiver and the slot elements. Control circuitry may control the switching circuitry to activate a selected pair of the slot antennas based on an orientation of the device or other data. The active pair of antennas may convey radio-frequency signals at the same frequencies using a multiple-input and multiple-output (MIMO) communications scheme. In this way, the device may perform wireless communications at relatively high data throughputs regardless of how the device is being held by a user.

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 have a hybrid antenna that includes a slot resonating element formed from a slot in a ground plane and a planar resonating element formed over the slot. A parasitic element may be disposed over the planar element. A switch may couple the parasitic element to the ground. A tunable circuit may couple the planar element to the ground. The switch and tunable circuit may be placed in different tuning states. In a first state, the tunable circuit and switch form open circuits. In a second state, the tunable circuit may an open circuit and the switch is closed. In a third state, the tunable circuit forms a return path and the switch forms an open circuit. This may allow the antenna to operate with satisfactory efficiency in low, mid, and high bands despite volume constraints imposed on the antenna.

Abstract: An electronic device may have hybrid antennas that include slot antenna resonating elements formed from slots in a ground plane and planar inverted-F antenna resonating elements. The planar inverted-F antenna resonating elements may each have a planar metal member that overlaps one of the slots. A return path and feed may be coupled in parallel between the planar metal member and the ground plane. Adjustable circuits such as tunable inductors may be used to tune the hybrid antennas. Adjustable circuits may bridge the slots in hybrid antennas and may be included in return paths that are coupled between the planar metal members of the planar inverted-F antenna resonating elements and the ground plane. A slot may be selectively divided to from two slots using switching circuitry.

Abstract: An electronic device may be provided with wireless circuitry. The wireless circuitry may include cavity antennas. A cavity antenna may be formed from a metal antenna cavity and resonating element structures. The metal antenna cavity may be formed from metal traces on a dielectric carrier. The resonating element structures may include directly fed and indirectly fed slot antenna resonating elements and monopole antenna resonating elements. The metal antenna cavity may exhibit a resonance that is tuned using a transmission line tuning stub. Filters and duplexer circuits may be used in routing signals at different frequency bands among the antenna resonating elements.

Abstract: An electronic device may have hybrid antennas that include slot antenna resonating elements formed from slots in a ground plane and planar inverted-F antenna resonating elements. The planar inverted-F antenna resonating elements may each have a planar metal member that overlaps one of the slots. The slot of each slot antenna resonating element may divide the ground plane into first and second portions. A return path and feed may be coupled in parallel between the planar metal member and the first portion of the ground plane. Tunable components such as tunable inductors may be used to tune the hybrid antennas. A tunable inductor may bridge the slot in hybrid antenna, may be coupled between the planar metal member of the planar inverted-F antenna resonating element and the ground plane, or multiple tunable inductors may bridge the slot on opposing sides of the planar inverted-F antenna resonating element.

Abstract: An electronic device housing may have a rear housing wall that forms a metal ground plane. A slot may be formed in the metal ground plane. The slot may have one or more open ends along an edge of the ground plane. A near-field communications loop antenna may overlap the slot. The near-field communications loop antenna may have one or more turns. A current path through the metal ground plane may form one of the turns in the near-field communications loop antenna. The slot may form portions of non-near-field-communications antennas in addition to the near-field communications loop antenna. The slot in the non-near-field-communications antennas may be fed using an indirect antenna feed structure. Components such as a capacitor and inductor may help allow non-near-field communications antenna and the near-field communications antenna to be formed from common portions of the metal ground plane.

Abstract: An electronic device may be provided with wireless circuitry. The wireless circuitry may include cavity antennas. A cavity antenna may be formed from a metal antenna cavity and resonating element structures. The metal antenna cavity may be formed from metal traces on a dielectric carrier. The resonating element structures may include directly fed and indirectly fed slot antenna resonating elements and monopole antenna resonating elements. The metal antenna cavity may exhibit a resonance that is tuned using a transmission line tuning stub. Filters and duplexer circuits may be used in routing signals at different frequency bands among the antenna resonating elements.

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 he coupled to control circuitry on the printed circuit board through the metal patch.

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: A method for wireless power transmission includes establishing respective wireless communication link between a coordinating transmitter and each receiver. The method further includes measuring respective mutual impedance between a coordinating transmitter and each receiver by applying a voltage to the coordinating transmitter and configuring each receiver to measure an induced current in response to the applied voltage. The method calculates respective matching impedance for the coordinating transmitter and each receiver based on corresponding mutual impedance. The method transmits the respective matching impedance to each receiver to enable each receiver to adjust to have the respective matching impedance. The method adjusts the coordinating transmitter to have the respective matching impedance.