Abstract: A display cover layer may be mounted in an electronic device housing using housing structures such as corner brackets. A slot antenna may be formed from a corner bracket opening, metal traces on a hollow plastic support structure, or other conductive structures. The slot antenna may have a main portion with opposing ends. An antenna feed may be located at one of the ends. The slot antenna may have a slot with one or more bends. The bends may provide the slot antenna with a C-shaped outline. A side branch slot may extend from the main portion of the slot at a location between the two bends. The presence of the side branch slot may enhance antenna bandwidth. A hollow enclosure may serve as an antenna support structure and as a speaker box enclosing a speaker driver. The antenna feed may be positioned so as to overlap the speaker driver.

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: A test system for testing a device under test (DUT) is provided. The test system may include a DUT receiving structure configured to receive the DUT during testing and a DUT retention structure that is configured to press the DUT against the DUT receiving structure so that DUT cannot inadvertently shift around during testing. The DUT retention structure may include a pressure sensor operable to detect an amount of pressure that is applied to the DUT. The DUT retention structure may be raised and lowered vertically using a manually-controlled or a computer-controlled positioner. The positioner may be adjusted using a coarse tuning knob and a fine tuning knob. The positioner may be calibrated such that the DUT retention structure applies a sufficient amount of pressure on the DUT during production testing.

Abstract: An electronic device may have control circuitry that uses a reflectometer to measure antenna impedance during operation. The reflectometer may have a directional coupler that is coupled between radio-frequency transceiver circuitry and an antenna. A calibration circuit may be coupled between the directional coupler and the antenna. The calibration circuit may have a first port coupled to the antenna, a second port coupled to the directional coupler, and a third port that is coupled to a calibration resistance. The reflectometer may have terminations of identical impedance that are coupled to ground. Switching circuitry in the reflectometer may be used to route signals from the directional coupler to a feedback receiver for measurement by the control circuitry or to ground through the terminations. Calibrated antenna reflection coefficient measurements may be used in dynamically adjusting the antenna.

Abstract: An electronic device may be provided with antenna structures. Proximity sensors and other sensors may be used in determining how the electronic device is being operated. Wireless circuitry such as a radio-frequency transmitter associated with a cellular telephone communications band, a wireless local area network band, or other communications band may be used in transmitting radio-frequency signals through the antenna structures at a transmit power. Control circuitry may adjust the wireless circuitry to ensure that the transmit power is capped at a maximum transmit power. The maximum transmit power may be adjusted dynamically by the control circuitry based on data from the proximity sensors, data from a magnetic sensor that detects whether a cover is present on the device, a connector sensor that detects whether the device is coupled to a dock or other accessory, and other sensors.

Abstract: An electronic device may be provided with antenna structures. The antenna structures may include a plate antenna. The electronic device may have a conductive housing such as a metal housing with an opening. A dielectric antenna window may be formed within the opening. A dielectric support structure such as a flexible printed circuit may overlap the opening. A conductive trace on the dielectric support structure may form an antenna resonating element plate for the plate antenna. The plate may have a periphery that is separated from adjacent portions of the metal housing by a gap. The antenna resonating element plate may have a rectangular shape with a bend that lies along an edge of the conductive housing. The dielectric antenna window may have a bend that also lies along the edge of the conductive housing.

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: 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: 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: Electronic devices are provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. A parallel-fed loop antenna may be formed from portions of a conductive bezel and a ground plane. The antenna may operate in multiple communications bands. The bezel may surround a peripheral portion of a display that is mounted to the front of an electronic device. The bezel may contain a gap. Antenna feed terminals for the antenna may be located on opposing sides of the gap. A variable capacitor may bridge the gap. An inductive element may bridge the gap and the antenna feed terminals. A switchable inductor may be coupled in parallel with the inductive element. Tunable matching circuitry may be coupled between one of the antenna feed terminals and a conductor in a coaxial cable connecting the transceiver circuitry to the antenna.

Abstract: Electronic devices may include radio-frequency transceiver circuitry and antenna structures. The antenna structures may include antenna resonating elements such as dual-band antenna resonating elements that resonate in first and second communications bands. The antenna structures may also contain parasitic antenna elements such as elements that are operative in only the first or second communications band and elements that are operative in both the first and second communications bands. The antenna resonating elements and parasitic elements may be mounted on a common dielectric carrier. The dielectric carrier may be mounted within a slot or other opening in a conductive element. The conductive element may be formed from conductive housing structures in an electronic device such as a portable computer. The portable computer may have a clutch barrel with a dielectric cover. The dielectric cover may overlap and cover the slot and the dielectric carrier.

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: A computer stylus may have an elongated body with a metal tube that serves as an antenna ground for an antenna. An antenna resonating element for the antenna may be formed from metal traces that wrap around a longitudinal axis for the elongated body. The antenna may be an inverted-F antenna. A ground antenna feed terminal for the inverted-F antenna may be coupled to the metal tube with a sheet metal member, conductive fabric, and solder. A clip may run along a side of the elongated body at a location that does not overlap the metal traces of the antenna resonating element. The antenna may be fed at a location on an opposing side of the elongated body from the clip. Antenna signals from the inverted-F antenna may be reflected towards the tip by metal structures at the end of the elongated body opposing the tip.

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 wireless electronic device may contain at least one antenna tuning element for use in tuning the operating frequency range of the device. The antenna tuning element may include radio-frequency switches, continuously/semi-continuously adjustable components such as tunable resistors, inductors, and capacitors, and other load circuits that provide desired impedance characteristics. A test station may be used to measure the radio-frequency characteristics associated with the tuning element. The test station may provide adjustable temperature, power, and impedance control to help emulate a true application environment for the tuning element without having to place the tuning element within an actual device during testing. The test system may include at least one signal generator and a tester for measuring harmonic distortion values and may include at least two signal generators and a tester for measuring intermodulation distortion values.

Abstract: Electronic devices are provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. An inverted-F antenna may have first and second short circuit legs and a feed leg. The first and second short circuit legs and the feed leg may be connected to a folded antenna resonating element arm. The antenna resonating element arm and the first short circuit leg may be formed from portions of a conductive electronic device bezel. The folded antenna resonating element arm may have a bend. The bezel may have a gap that is located at the bend. Part of the folded resonating element arm may be formed from a conductive trace on a dielectric member. A spring may be used in connecting the conductive trace to the electronic device bezel portion of the antenna resonating element arm.

Abstract: An electronic device may be provided with wireless circuitry. The wireless circuitry may include a pair of antennas. The antennas may be formed from inverted-F antenna resonating elements located along one of the peripheral edges of a device housing. The housing may be formed of metal and may serve as an antenna ground for the antennas. The antennas may be used to receive satellite navigation system signals that are processed by a satellite navigation system receiver. An orientation sensor may be used to gather information on the orientation of the electronic device relative to the Earth. Information on received signal strength may be obtained from the satellite navigation system receiver. Based on orientation information or received signal strength information or other information, switching circuitry may be adjusted to switch an optimum one of the antennas into use or phase shifter circuitry may be adjusted to optimize signal reception.

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: An electronic device antenna may be provided with an antenna ground. An antenna resonating element may have a first end that is coupled to the ground using an inductor and may have a second end that is coupled to a peripheral conductive housing member in an electronic device. The peripheral conductive housing member may have a portion that is connected to the ground and may have a portion that is separated from the ground by a gap. The gap may be bridged by an inductor that couples the second end of the antenna resonating element to the antenna ground. The inductor may be bridged by a switch. A tunable circuit such as a capacitor bridged by a switch may be interposed in the antenna resonating element. The switches that bridge the gap and the capacitor may be used in tuning the antenna.