PATENT DOCUMENT

Publication Number: US-10468756-B2
Application Number: US-201815940772-A
Country: US
Kind Code: B2

Title: Antennas having symmetrical switching architecture

Abstract:
An electronic device may include wireless circuitry with antennas. An antenna resonating element arm for an antenna may be formed from conductive housing structures running along the edges of the device. The antenna may have first and second antenna feeds and multiple adjustable components that bridge a slot between the antenna resonating element and an antenna ground. Control circuitry may control the adjustable components and selectively activate one of the first and second feeds at a given time to place the antenna in first, second, or third operating modes. The control circuitry may determine which operating mode to use based on information indicative of the operating environment of the device. By switching between the operating modes, the control circuitry may shift current hot spots across the length of the resonating element arm to ensure satisfactory performance of the antenna in a variety of operating conditions.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 peripheral conductive housing structures, wherein a segment of the peripheral conductive housing structures extends between first and second dielectric-filled gaps in the peripheral conductive housing structures; 
 an antenna that comprises the segment, an antenna ground separated from the segment by a slot, a switch coupled between a first point on the segment and the antenna ground, an adjustable component coupled between a second point on the segment and the antenna ground, a first antenna feed coupled between a third point on the segment and the antenna ground, and a second antenna feed coupled between a fourth point on the segment and the antenna ground; and 
 control circuitry coupled to the antenna and configured to place the antenna into a selected one of:
 a first state in which the first antenna feed is active, the second antenna feed is inactive, and the switch is closed, and 
 a second state in which the first antenna feed is inactive, the second antenna feed is active, the switch is open, and the adjustable component tunes a frequency response of the antenna. 
 
 
     
     
       2. The electronic device defined in  claim 1 , further comprising:
 an additional adjustable component coupled between a fifth point on the segment and the antenna ground. 
 
     
     
       3. The electronic device defined in  claim 2 , wherein the first point is interposed between the first dielectric-filled gap and the second point, the second point is interposed between the first and third points, the third point is interposed between the second and fourth points, the fourth point is interposed between the third point and the second dielectric-filled gap, and the fifth point is interposed between the third point and the second dielectric-filled gap. 
     
     
       4. The electronic device defined in  claim 1 , wherein the first point is interposed between the first dielectric-filled gap and the second point, the second point is interposed between the first and third points, the third point is interposed between the second and fourth points, and the fourth point is interposed between the third point and the second dielectric-filled gap. 
     
     
       5. The electronic device defined in  claim 4 , further comprising:
 sensor circuitry configured to gather sensor data, wherein the control circuitry is configured to place the antenna into the selected one of the first and second states based on the sensor data. 
 
     
     
       6. The electronic device defined in  claim 5 , wherein the sensor circuitry comprises a sensor selected from the group consisting of: an accelerometer, a compass, an impedance sensor, and a gyroscope. 
     
     
       7. The electronic device defined in  claim 4 , wherein the electronic device has a first edge and a second edge that is different from the first edge, the first gap is formed in the peripheral conductive structures along the first edge, and the second gap is formed in the peripheral conductive structures along the second edge. 
     
     
       8. The electronic device defined in  claim 4 , wherein the frequency response comprises a resonance at frequencies within a cellular telephone communications band. 
     
     
       9. The electronic device defined in  claim 8 , wherein the cellular telephone communications band comprises frequencies between 700 MHz and 960 MHz. 
     
     
       10. The electronic device defined in  claim 1 , further comprising:
 a display having a display cover layer mounted to the peripheral conductive housing structures; and 
 a rear housing wall, wherein the peripheral conductive housing structures surround a periphery of the electronic device and extend from the rear housing wall to the display cover layer. 
 
     
     
       11. The electronic device defined in  claim 1 , wherein the adjustable component comprises a switchable inductor. 
     
     
       12. An electronic device, comprising:
 peripheral conductive housing sidewalls; and 
 an antenna, wherein the antenna comprises:
 a segment of the peripheral conductive housing sidewalls having opposing ends defined by first and second gaps in the peripheral conductive housing sidewalls, 
 an antenna ground separated from the segment by a slot, 
 a switch coupled between a first point on the segment and the antenna ground across the slot, 
 a first antenna tuning component coupled between a second point on the segment and the antenna ground across the slot, 
 a first antenna feed coupled between a third point on the segment and the antenna ground across the slot, 
 a second antenna feed coupled between a fourth point on the segment and the antenna ground across the slot, and 
 a second antenna tuning component coupled between a fifth point on the segment and the antenna ground across the slot, wherein the first point is interposed between the first gap and the second point, the second point is interposed between the first and third points, the third point is interposed between the second and fourth points, and the fourth and fifth points are both interposed between the third point and the second gap. 
 
 
     
     
       13. The electronic device defined by  claim 12 , further comprising:
 control circuitry configured to adjust the first and second antenna tuning components to tune a frequency response of the antenna. 
 
     
     
       14. The electronic device defined in  claim 13 , further comprising:
 sensor circuitry configured to generate sensor data, wherein the control circuitry is configured to toggle the switch and to adjust the first and second antenna tuning components based on the sensor data. 
 
     
     
       15. The electronic device defined in  claim 14 , wherein the sensor circuitry comprises a sensor selected from the group consisting of:
 an accelerometer, a compass, and impedance sensor, and a gyroscope. 
 
     
     
       16. The electronic device defined in  claim 12 , further comprising:
 control circuitry, wherein the control circuitry is configured to place the antenna into a selected one of:
 a first operating mode in which the first antenna feed is enabled and the second antenna feed is disabled, and 
 a second operating mode in which the first antenna feed is disabled and the second antenna feed is enabled. 
 
 
     
     
       17. The electronic device defined in  claim 16 , wherein the switch is closed in the first mode of operation and open in the second mode of operation. 
     
     
       18. An antenna comprising:
 an antenna ground; 
 a conductive segment having a first end separated from the antenna ground by a first gap and an opposing second end separated from the antenna ground by a second gap, wherein a dielectric slot extends between the conductive segment and the antenna ground from the first gap to the second gap; 
 a switch coupled between a first point on the conductive segment and the antenna ground across the slot; 
 a first antenna feed coupled between a second point on the conductive segment and the antenna ground, the first point being interposed between the first gap and the second point; and 
 a second antenna feed coupled between a third point on the conductive segment and the antenna ground, wherein the second point is interposed between the first and third points, the third point is interposed between the second point and the second gap, and the antenna is operable in:
 a first mode in which the first antenna feed is active, the second antenna feed is inactive, and the switch forms a short circuit between the conductive segment and the antenna ground, and 
 a second mode in which the first antenna feed is inactive, the second antenna feed is active, and the switch forms an open circuit between the conductive segment and the antenna ground. 
 
 
     
     
       19. The antenna defined in  claim 18 , further comprising:
 a tunable component coupled between a fourth point on the conductive segment and the antenna ground, wherein the fourth point is interposed between the first and second points, and, when the antenna is in the second mode, the tunable component is configured to tune a frequency response of the antenna within a frequency band that comprises frequencies between 700 MHz and 960 MHz. 
 
     
     
       20. The antenna defined in  claim 19 , further comprising:
 an additional tunable component coupled between a fifth point on the conductive segment and the antenna ground, wherein the fifth point is interposed between the second point and the second gap.

Description:
This application is a continuation of patent application Ser. No. 15/429,597, filed Feb. 10, 2017, which claims the benefit of provisional patent application No. 62/398,375, filed Sep. 22, 2016, which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. 
     It can be challenging to form electronic device antenna structures with desired attributes. In some wireless devices, antennas are bulky. In other devices, antennas are compact, but are sensitive to the position of the antennas relative to external objects. If care is not taken, antennas may become detuned, may emit wireless signals with a power that is more or less than desired, or may otherwise not perform as expected. 
     It would therefore be desirable to be able to provide improved wireless circuitry for electronic devices. 
     SUMMARY 
     An electronic device may have wireless circuitry with antennas. An antenna may be formed from an antenna resonating element arm and an antenna ground. The antenna resonating element arm and antenna ground may be formed from metal housing structures or other conductive structures that are separated by a slot. The antenna resonating element arm may, for example, be formed from peripheral conductive structures running along the edges of the metal housing structures and an elongated opening in the metal housing structures may separate the antenna resonating element arm from a planar portion of the metal housing structures that serves as the antenna ground. 
     The antenna may have a first antenna feed having a positive feed terminal coupled to a first location on the resonating element arm and a second antenna feed having a positive feed terminal coupled to a second location on the resonating element arm. The resonating element arm may have opposing first and second ends. The antenna feeds and other components may be coupled between the resonating element arm and the antenna ground symmetrically around the longitudinal axis of the device. For example, the second location may be interposed between the first location and the second end of the resonating element arm. A first adjustable component may be coupled between a third location on the resonating element arm and the antenna ground. The third location may be interposed between the first location and the first end of the resonating element arm. A second adjustable component may be coupled between a fourth location on the resonating element arm and the antenna ground. The fourth location may be interposed between the second location and the second end of the resonating element arm. A third adjustable component may be coupled between a fifth location on the resonating element arm and the antenna ground. The fifth location may be interposed between the fourth location and the second end of the resonating element arm. 
     The first antenna feed terminal may be coupled to the first location on the resonating element arm by a fourth adjustable component. The fourth adjustable component may include a shunt switch coupled between the first antenna feed terminal and the antenna ground. During operation, loading of the antenna by an external object such as a user&#39;s hand can detune the antenna. The loading of the antenna may be dependent on how the user holds the device (e.g., whether the user holds the device with a left or right hand). 
     The electronic device may include control circuitry that controls the first, second, third, and fourth adjustable components and that selectively activates one of the first and second feeds at a given time to place the antenna in a first, second, or third operating mode (e.g., a free space mode, a left hand head mode, and a right hand head mode). As an example, the control circuitry may close the shunt switch to form a short circuit path between the resonating element arm and the antenna ground when the first antenna feed is inactive (disabled) and may open the shunt switch when the first antenna feed is active (enabled). The control circuitry may enable the first antenna feed and disable the second antenna feed in the free space and left hand head operating modes. The control circuitry may enable the second antenna feed and disable the first antenna feed in the right hand head operating mode. The control circuitry may determine which operating mode to use based on sensor data gathered by sensor circuitry and/or any other desired information about the operating environment of the device. By switching between the operating modes, the control circuitry may shift antenna current hot spots across the length of the resonating element arm to ensure satisfactory performance of the antenna in a variety of operating conditions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of illustrative circuitry in an electronic device in accordance with an embodiment. 
         FIG. 3  is a schematic diagram of illustrative wireless circuitry in accordance with an embodiment. 
         FIG. 4  is a schematic diagram of an illustrative inverted-F antenna in accordance with an embodiment. 
         FIG. 5  is a schematic diagram of an illustrative slot antenna in accordance with an embodiment. 
         FIG. 6  is a diagram of illustrative antenna structures having a symmetric switching architecture in accordance with an embodiment. 
         FIG. 7  is a graph in which antenna efficiency has been plotted as a function of operating frequency in accordance with an embodiment. 
         FIG. 8  is a flow chart of illustrative steps that may be involved in operating an electronic device having an antenna of the type shown in  FIG. 6  in accordance with an embodiment. 
         FIG. 9  is a diagram of an illustrative adjustable multi-element inductor that may be used in an antenna in accordance with an embodiment. 
         FIG. 10  is a diagram of an illustrative adjustable single-element inductor that may be used in an antenna in accordance with an embodiment. 
         FIG. 11  is a diagram of an illustrative shunt switch that may be used in an antenna in accordance with an embodiment. 
         FIG. 12  is a diagram of illustrative aperture tuning circuitry that may be used in an antenna in accordance with an embodiment. 
         FIG. 13  is a diagram of illustrative antenna feed switching circuitry that may be used to selectively enable one of multiple different antenna feeds in an antenna in accordance with an embodiment. 
         FIG. 14  is a state diagram showing illustrative antenna operating modes for an electronic device in accordance with an embodiment. 
         FIG. 15  is a flow chart of illustrative steps that may be involved in determining an operating mode to use for an antenna in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. 
     The wireless communications circuitry may include one more antennas. The antennas of the wireless communications circuitry can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, monopole antennas, dipole antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. 
     The conductive electronic device structures may include conductive housing structures. The housing structures may include peripheral structures such as peripheral conductive structures that run around the periphery of an electronic device. The peripheral conductive structure may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, may have portions that extend upwards from an integral planar rear housing (e.g., to form vertical planar sidewalls or curved sidewalls), and/or may form other housing structures. 
     Gaps may be formed in the peripheral conductive structures that divide the peripheral conductive structures into peripheral segments. One or more of the segments may be used in forming one or more antennas for electronic device  10 . Antennas may also be formed using an antenna ground plane formed from conductive housing structures such as metal housing midplate structures and other internal device structures. Rear housing wall structures may be used in forming antenna structures such as an antenna ground. 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Device  10  may also be a set-top box, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may be mounted on the front face of device  10 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or may be insensitive to touch. The rear face of housing  12  (i.e., the face of device  10  opposing the front face of device  10 ) may have a planar housing wall. The rear housing wall may be have slots that pass entirely through the rear housing wall and that therefore separate housing wall portions (and/or sidewall portions) of housing  12  from each other. Housing  12  (e.g., the rear housing wall, sidewalls, etc.) may also have shallow grooves that do not pass entirely through housing  12 . The slots and grooves may be filled with plastic or other dielectric. If desired, portions of housing  12  that have been separated from each other (e.g., by a through slot) may be joined by internal conductive structures (e.g., sheet metal or other metal members that bridge the slot). 
     Display  14  may include pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable pixel structures. A display cover layer such as a layer of clear glass or plastic may cover the surface of display  14  or the outermost layer of display  14  may be formed from a color filter layer, thin-film transistor layer, or other display layer. Buttons such as button  24  may pass through openings in the cover layer. The cover layer may also have other openings such as an opening for speaker port  26 . 
     Housing  12  may include peripheral housing structures such as structures  16 . Structures  16  may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape with four edges, structures  16  may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges (as an example). Peripheral structures  16  or part of peripheral structures  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or that helps hold display  14  to device  10 ). Peripheral structures  16  may also, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral housing structures  16  may be formed of a conductive material such as metal and may therefore sometimes be referred to as peripheral conductive housing structures, conductive housing structures, peripheral metal structures, or a peripheral conductive housing member (as examples). Peripheral housing structures  16  may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, or more than two separate structures may be used in forming peripheral housing structures  16 . 
     It is not necessary for peripheral housing structures  16  to have a uniform cross-section. For example, the top portion of peripheral housing structures  16  may, if desired, have an inwardly protruding lip that helps hold display  14  in place. The bottom portion of peripheral housing structures  16  may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). Peripheral housing structures  16  may have substantially straight vertical sidewalls, may have sidewalls that are curved, or may have other suitable shapes. In some configurations (e.g., when peripheral housing structures  16  serve as a bezel for display  14 ), peripheral housing structures  16  may run around the lip of housing  12  (i.e., peripheral housing structures  16  may cover only the edge of housing  12  that surrounds display  14  and not the rest of the sidewalls of housing  12 ). 
     If desired, housing  12  may have a conductive rear surface. For example, housing  12  may be formed from a metal such as stainless steel or aluminum. The rear surface of housing  12  may lie in a plane that is parallel to display  14 . In configurations for device  10  in which the rear surface of housing  12  is formed from metal, it may be desirable to form parts of peripheral conductive housing structures  16  as integral portions of the housing structures forming the rear surface of housing  12 . For example, a rear housing wall of device  10  may be formed from a planar metal structure and portions of peripheral housing structures  16  on the sides of housing  12  may be formed as flat or curved vertically extending integral metal portions of the planar metal structure. Housing structures such as these may, if desired, be machined from a block of metal and/or may include multiple metal pieces that are assembled together to form housing  12 . The planar rear wall of housing  12  may have one or more, two or more, or three or more portions. 
     Display  14  may have an array of pixels that form an active area AA that displays images for a user of device  10 . An inactive border region such as inactive area IA may run along one or more of the peripheral edges of active area AA. 
     Display  14  may include conductive structures such as an array of capacitive electrodes for a touch sensor, conductive lines for addressing pixels, driver circuits, etc. Housing  12  may include internal conductive structures such as metal frame members and a planar conductive housing member (sometimes referred to as a midplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more parts that is welded or otherwise connected between opposing sides of member  16 ). Device  10  may also include conductive structures such as printed circuit boards, components mounted on printed circuit boards, and other internal conductive structures. These conductive structures, which may be used in forming a ground plane in device  10 , may be located in the center of housing  12  and may extend under active area AA of display  14 . 
     In regions  22  and  20 , openings may be formed within the conductive structures of device  10  (e.g., between peripheral conductive housing structures  16  and opposing conductive ground structures such as conductive housing midplate or rear housing wall structures, a printed circuit board, and conductive electrical components in display  14  and device  10 ). These openings, which may sometimes be referred to as gaps, may be filled with air, plastic, and other dielectrics and may be used in forming slot antenna resonating elements for one or more antennas in device  10 . 
     Conductive housing structures and other conductive structures in device  10  such as a midplate, traces on a printed circuit board, display  14 , and conductive electronic components may serve as a ground plane for the antennas in device  10 . The openings in regions  20  and  22  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, may contribute to the performance of a parasitic antenna resonating element, or may otherwise serve as part of antenna structures formed in regions  20  and  22 . If desired, the ground plane that is under active area AA of display  14  and/or other metal structures in device  10  may have portions that extend into parts of the ends of device  10  (e.g., the ground may extend towards the dielectric-filled openings in regions  20  and  22 ), thereby narrowing the slots in regions  20  and  22 . In configurations for device  10  with narrow U-shaped openings or other openings that run along the edges of device  10 , the ground plane of device  10  can be enlarged to accommodate additional electrical components (integrated circuits, sensors, etc.). 
     In general, device  10  may include any suitable number of antennas (e.g., one or more, two or more, three or more, four or more, etc.). The antennas in device  10  may be located at opposing first and second ends of an elongated device housing (e.g., at ends  20  and  22  of device  10  of  FIG. 1 ), along one or more edges of a device housing, in the center of a device housing, in other suitable locations, or in one or more of these locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral housing structures  16  may be provided with peripheral gap structures. For example, peripheral conductive housing structures  16  may be provided with one or more gaps such as gaps  18 , as shown in  FIG. 1 . The gaps in peripheral housing structures  16  may be filled with dielectric such as polymer, ceramic, glass, air, other dielectric materials, or combinations of these materials. Gaps  18  may divide peripheral housing structures  16  into one or more peripheral conductive segments. There may be, for example, two peripheral conductive segments in peripheral housing structures  16  (e.g., in an arrangement with two of gaps  18 ), three peripheral conductive segments (e.g., in an arrangement with three of gaps  18 ), four peripheral conductive segments (e.g., in an arrangement with four gaps  18 , etc.). The segments of peripheral conductive housing structures  16  that are formed in this way may form parts of antennas in device  10 . 
     If desired, openings in housing  12  such as grooves that extend partway or completely through housing  12  may extend across the width of the rear wall of housing  12  and may penetrate through the rear wall of housing  12  to divide the rear wall into different portions. These grooves may also extend into peripheral housing structures  16  and may form antenna slots, gaps  18 , and other structures in device  10 . Polymer or other dielectric may fill these grooves and other housing openings. In some situations, housing openings that form antenna slots and other structure may be filled with a dielectric such as air. 
     In a typical scenario, device  10  may have upper and lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme, if desired. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, etc. 
     A schematic diagram showing illustrative components that may be used in device  10  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, application specific integrated circuits, etc. Storage and processing circuitry  28  may sometimes be referred to herein as control circuitry  28 . 
     Storage and processing circuitry  28  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, multiple-input and multiple-output (MIMO) protocols, antenna diversity protocols, etc. 
     Input-output circuitry  30  may include input-output devices  32 . Input-output devices  32  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  32  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  32  may include touch screens, displays without touch sensor capabilities, buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, position and orientation sensors (e.g., sensors such as accelerometers, gyroscopes, and compasses), capacitance sensors, proximity sensors (e.g., capacitive proximity sensors, light-based proximity sensors, etc.), fingerprint sensors (e.g., a fingerprint sensor integrated with a button such as button  24  of  FIG. 1  or a fingerprint sensor that takes the place of button  24 ), etc. 
     Input-output circuitry  30  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  34  may include radio-frequency transceiver circuitry  90  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  42 . Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a low-midband from 960 to 1710 MHz, a midband from 1710 to 2170 MHz, and a high band from 2300 to 2700 MHz or other communications bands between 700 MHz and 2700 MHz or other suitable frequencies (as examples). Circuitry  38  may handle voice data and non-voice data. Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include 60 GHz transceiver circuitry, circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. Wireless communications circuitry  34  may include global positioning system (GPS) receiver equipment such as GPS receiver circuitry  42  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, dipole antenna structures, monopole antenna structures, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. 
     As shown in  FIG. 3 , transceiver circuitry  90  in wireless circuitry  34  may be coupled to antenna structures  40  using paths such as path  92 . Wireless circuitry  34  may be coupled to control circuitry  28 . Control circuitry  28  may be coupled to input-output devices  32 . Input-output devices  32  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures such as antenna(s)  40  with the ability to cover communications frequencies of interest, antenna(s)  40  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). If desired, antenna(s)  40  may be provided with adjustable circuits such as tunable components  102  to tune antennas over communications bands of interest. Tunable components  102  may be part of a tunable filter or tunable impedance matching network, may be part of an antenna resonating element, may span a gap between an antenna resonating element and antenna ground, etc. Tunable components  102  may include tunable inductors, tunable capacitors, or other tunable components. Tunable components such as these may be based on switches and networks of fixed components, distributed metal structures that produce associated distributed capacitances and inductances, variable solid state devices for producing variable capacitance and inductance values, tunable filters, or other suitable tunable structures. During operation of device  10 , control circuitry  28  may issue control signals on one or more paths such as path  120  that adjust inductance values, capacitance values, or other parameters associated with tunable components  102 , thereby tuning antenna structures  40  to cover desired communications bands. 
     Path  92  may include one or more transmission lines. As an example, signal path  92  of  FIG. 3  may be a transmission line having a positive signal conductor such as line  94  and a ground signal conductor such as line  96 . Lines  94  and  96  may form parts of a coaxial cable or a microstrip transmission line (as examples). A matching network formed from components such as inductors, resistors, and capacitors may be used in matching the impedance of antenna(s)  40  to the impedance of transmission line  92 . Matching network components may be provided as discrete components (e.g., surface mount technology components) or may be formed from housing structures, printed circuit board structures, traces on plastic supports, etc. Components such as these may also be used in forming filter circuitry in antenna(s)  40  and may be tunable and/or fixed components. 
     Transmission line  92  may be coupled to antenna feed structures associated with antenna structures  40 . As an example, antenna structures  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed with a positive antenna feed terminal such as terminal  98  and a ground antenna feed terminal such as ground antenna feed terminal  100 . Positive transmission line conductor  94  may be coupled to positive antenna feed terminal  98  and ground transmission line conductor  96  may be coupled to ground antenna feed terminal  92 . Other types of antenna feed arrangements may be used if desired. For example, antenna structures  40  may be fed using multiple feeds. The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     Control circuitry  28  may use an impedance measurement circuit to gather antenna impedance information. Control circuitry  28  may use information from a proximity sensor (see, e.g., sensors  32  of  FIG. 2 ), received signal strength information, device orientation information from an orientation sensor, information from a connector sensor that senses the presence of a digital connector adjacent to antenna  40 , information identifying whether wired or wireless headphones are being used with device  10 , information identifying a type of headphones that are being used with device  10 , information from one or more antenna impedance sensors, information on the operating state or usage scenario of device  10 , or other information in determining when antenna  40  is being affected by the presence of nearby external objects or is otherwise in need of tuning. In response, control circuitry  28  may adjust an adjustable inductor, adjustable capacitor, switch, or other tunable components  102  to ensure that antenna  40  operates as desired. Adjustments to components  102  may also be made to extend the coverage of antenna  40  (e.g., to cover desired communications bands that extend over a range of frequencies larger than antenna  40  would cover without tuning). 
       FIG. 4  is a diagram of illustrative inverted-F antenna structures that may be used in implementing antenna  40  for device  10 . Inverted-F antenna  40  of  FIG. 4  has antenna resonating element  106  and antenna ground (ground plane)  104 . Antenna resonating element  106  may have a main resonating element arm such as arm  108 . The length of arm  108  and/or portions of arm  108  may be selected so that antenna  40  resonates at desired operating frequencies. For example, the length of arm  108  may be a quarter of a wavelength at a desired operating frequency for antenna  40 . Antenna  40  may also exhibit resonances at harmonic frequencies. 
     Main resonating element arm  108  may be coupled to ground  104  by return path  110 . An inductor or other component may be interposed in path  110  and/or tunable components  102  may be interposed in path  110  and/or coupled in parallel with path  110  between arm  108  and ground  104 . 
     Antenna  40  may be fed using one or more antenna feeds. For example, antenna  40  may be fed using antenna feed  112 . Antenna feed  112  may include positive antenna feed terminal  98  and ground antenna feed terminal  100  and may run in parallel to return path  110  between arm  108  and ground  104 . If desired, inverted-F antennas such as illustrative antenna  40  of  FIG. 4  may have more than one resonating arm branch (e.g., to create multiple frequency resonances to support operations in multiple communications bands) or may have other antenna structures (e.g., parasitic antenna resonating elements, tunable components to support antenna tuning, etc.). For example, arm  108  may have left and right branches that extend outwardly from feed  112  and return path  110 . Multiple feeds may be used to feed antennas such as antenna  40 . 
     Antenna  40  may be a hybrid antenna that includes one or more slot antenna resonating elements. As shown in  FIG. 5 , for example, antenna  40  may be based on a slot antenna configuration having an opening such as slot  114  that is formed within conductive structures such as antenna ground  104 . Slot  114  may be filled with air, plastic, and/or other dielectric. The shape of slot  114  may be straight or may have one or more bends (i.e., slot  114  may have an elongated shape following a meandering path). The antenna feed for antenna  40  may include positive antenna feed terminal  98  and ground antenna feed terminal  100 . Feed terminals  98  and  100  may, for example, be located on opposing sides of slot  114  (e.g., on opposing long sides). Slot-based antenna resonating elements such as slot antenna resonating element  114  of  FIG. 5  may give rise to an antenna resonance at frequencies in which the wavelength of the antenna signals is equal to the perimeter of the slot. In narrow slots, the resonant frequency of a slot antenna resonating element is associated with signal frequencies at which the slot length is equal to a half of a wavelength. Slot antenna frequency response can be tuned using one or more tunable components such as tunable inductors or tunable capacitors. These components may have terminals that are coupled to opposing sides of the slot (i.e., the tunable components may bridge the slot). If desired, tunable components may have terminals that are coupled to respective locations along the length of one of the sides of slot  114 . Combinations of these arrangements may also be used. 
     Antenna  40  may be a hybrid slot-inverted-F antenna that includes resonating elements of the type shown in both  FIG. 4  and  FIG. 5 . An illustrative configuration for an antenna with slot and inverted-F antenna structures is shown in  FIG. 6 . 
     The presence or absence of external objects such as a user&#39;s hand or other body part in the vicinity of antenna  40  may affect antenna loading and therefore antenna performance. Antenna loading may differ depending on the way in which device  10  is being held. For example, antenna loading and therefore antenna performance may be affected in one way when a user is holding device  10  in the user&#39;s right hand and may be affected in another way when a user is holding device  10  in the user&#39;s left hand. In addition, antenna loading and performance may be affected in one way when a user is holding device  10  to the user&#39;s head and in another way when the user is holding device  10  away from the user&#39;s head. To accommodate various loading scenarios, device  10  may use sensor data, antenna measurements, information about the usage scenario or operating state of device  10 , and/or other data from input-output circuitry  30  to monitor for the presence of antenna loading (e.g., the presence of a user&#39;s hand, the user&#39;s head, or another external object). Device  10  (e.g., control circuitry  28 ) may then adjust adjustable components  102  in antenna  40  to compensate for the loading. 
     In order to help compensate for antenna loading due to the presence of external objects such as the user&#39;s hand at different locations relative to device  10 , antenna  40  may include multiple antenna feeds (e.g., antenna feeds such as antenna feed  112  of  FIG. 4 ). Control circuitry  28  may selectively activate one of the multiple antenna feeds at a given time. For example, control circuitry  28  may selectively activate the antenna feed that is located farthest away from an external object that is loading the antenna to help minimize the impact of the presence of the external object on the performance of antenna  40 . 
     As shown in  FIG. 6 , antenna  40  (e.g., a hybrid slot-inverted-F antenna) may include a first antenna feed P 1  and a second antenna feed P 2  (sometimes referred to herein as first antenna port P 1  and second antenna port P 2 ). Antenna  40  of  FIG. 6  may be, for example, a lower antenna formed within region  20  of device  10  ( FIG. 1 ). Feeds P 1  and P 2  may be fed by transceiver circuitry that is coupled to feeds P 1  and P 2  over one or more corresponding transmission lines  92 . Antenna  40  may include a slot such as slot  114  that is formed from an elongated gap between peripheral conductive structures  16  and ground  104  (e.g., a slot formed in housing  12  using machining tools or other equipment). The slot may be filled with dielectrics such as air and/or plastic. For example, plastic may be inserted into portions of slot  114  and this plastic may be flush with the outside of housing  12 . If desired, a connector port such as connector port  164  may be formed in peripheral structures  16 . Connector port  164  may receive a mating digital connector or other connector structure. Connector port  164  may receive data signals and/or power from the connector structure and/or may provide data signals to the connector structure when inserted in port  164 . 
     Portions of slot  114  may contribute slot antenna resonances to antenna  40 . Peripheral conductive structures  16  may form an antenna resonating element arm such as arm  108  of  FIG. 4  that extends between gaps  18 - 1  and  18 - 2  (e.g., gaps  18  in peripheral conductive structures  16 ). For example, a first end of the segment of peripheral structures  16  that forms resonating element arm  108  may define an edge of gap  18 - 1  whereas an opposing second end of the segment of peripheral structures  16  defines an edge of gap  18 - 2 . First and second antenna feeds P 1  and P 2  may include respective positive antenna feed terminals  98  and ground antenna feed terminals  100  ( FIG. 3 ). For example, first antenna feed P 1  may include a positive antenna feed terminal  98 - 1  and a corresponding ground antenna feed terminal  100 - 1  that are coupled to opposing sides of slot  114 . Positive antenna feed terminal  98 - 1  may be coupled to peripheral conductive structures  16  via feed leg  170  whereas ground antenna feed terminal  100 - 1  is coupled to a first location along ground plane  104 . Second antenna feed P 2  may include a positive antenna feed terminal  98 - 2  and a corresponding ground antenna feed terminal  100 - 2 . Positive antenna feed terminal  98 - 2  may be coupled to peripheral conductive structures  16  via feed leg  168  whereas ground antenna feed terminal  100 - 2  is coupled to a second location along ground plane  104 . Feed legs  168  and  170  may sometimes be referred to herein as feed arms, feed paths, feed conductors, or feed elements. Feed legs  168  and  170  may include any desired conductive structures such as conductive wire, metal traces on a rigid or flexible printed circuit board, sheet metal, metal portions of electronic device components, conductive radio-frequency connectors, conductive spring structures, metal screws or other fasteners, weld structures, solder structures, conductive adhesive structures, combinations of these structures, etc. 
     Feed leg  170  may be coupled to peripheral conductive structures  16  at point  180  whereas feed leg  168  is coupled to peripheral conductive structures  16  at point  182 . Point  182  may, for example, be located at a given distance from gap  18 - 1  (e.g., along the width of device  10 ). If desired, point  180  may also be coupled to peripheral structures  16  at the same given distance from gap  18 - 2 . Similarly, ground feed terminal  100 - 2  may be coupled to ground plane  104  at the same distance with respect to gap  18 - 1  as ground terminal  100 - 1  is with respect to gap  18 - 2 . In other words, antenna feeds P 1  and P 2  may be symmetrically distributed across the width of device  10  (e.g., about the longitudinal axis  190  of device  10  running down the center and along the longest dimension of the device). This example is merely illustrative. In general, antenna feed P 2  may be coupled between ground  104  and peripheral structures  16  at any desired location that is interposed between antenna feed P 1  and gap  18 - 1 . Antenna feed P 1  may be coupled between ground  104  and peripheral structures  16  at any desired location that is interposed between antenna feed P 2  and gap  18 - 2 . Ground antenna feed terminals  100 - 2  and  100 - 1  may be coupled to antenna ground  104  at any desired locations (e.g., either symmetrically or asymmetrically distributed about longitudinal axis  190 ) and/or feed legs  168  and  170  may be coupled to conductive structures  16  at any desired locations (e.g., either symmetrically or asymmetrically distributed about the longitudinal axis  190 ). 
     Adjustable tuning components  102  of  FIG. 3  may include adjustable (tunable) components such as components  152 ,  154 ,  156 ,  158 , and  160  of  FIG. 6 . Adjustable component  156  may be interposed on feed leg  168  between positive feed terminal  98 - 2  and peripheral structures  16 . Adjustable component  158  may be interposed on feed leg  170  between positive feed terminal  98 - 1  and peripheral structures  16 . Control circuitry  28  may adjust components  156  and  158  to adjust the performance of antenna  40 . For example, control circuitry  28  may adjust components  156  and  158  to selectively activate one of antenna feeds P 1  and P 2  at a given time. 
     In one suitable arrangement, adjustable component  158  may include switching circuitry such as a shunt single-pole double-throw (SP2T) switch or any other desired switching circuitry. When antenna feed P 1  is to be activated (enabled), control circuitry  28  may adjust the switching circuitry in adjustable component  158  to route radio-frequency antenna signals between antenna feed terminal  98 - 1  and peripheral structures  16 . When antenna feed P 1  is to be deactivated (disabled), control circuitry  28  may adjust the switching circuitry in adjustable component  158  to short radio-frequency antenna signals conveyed over path  170  to ground. 
     If desired, adjustable component  156  may include switching circuitry such as a single-pole single-throw (SPST) switch or any other desired switching circuitry. The SPST switch may, for example, be coupled in series between feed terminal  98 - 2  and point  182  on peripheral structures  16 . When antenna feed P 2  is to be activated, control circuitry  28  may close the switch in adjustable component  156  to route signals between feed terminal  98 - 2  and peripheral structures  16 . When antenna feed P 2  is to be deactivated, control circuitry  28  may open the switch in adjustable component  156  to form an open circuit between antenna feed terminal  98 - 2  and peripheral structures  16  (e.g., so that signals are not conveyed between feed terminal  98 - 2  and peripheral structures  16 ). 
     Adjustable component  154  may be coupled between ground  104  and peripheral structures  16  (e.g., a first terminal  192  of adjustable component  154  may be coupled to ground  104  whereas a second terminal  194  of adjustable component  154  is coupled to peripheral structures  16 ). Terminal  194  of adjustable component  154  may be interposed between point  182  and gap  18 - 1 . Terminal  192  of adjustable component  154  may be interposed between ground antenna feed terminal  100 - 2  and gap  18 - 1 . Adjustable component  154  may include switchable inductors and resistors coupled in parallel between ground  104  and peripheral structures  16 , for example. Control circuitry  28  may adjust component  154  to tune the resonant frequency of antenna  40  and/or to adjust the antenna efficiency of antenna  40 . Component  154  may sometimes be referred to herein as aperture tuning circuitry  154  or aperture tuner  154  (e.g., because adjusting component  154  may effectively tune or adjust the aperture or perimeter of slot  114 ). 
     Adjustable component  152  may be coupled between ground  104  and peripheral structures  16  (e.g., a first terminal  196  of adjustable component  152  may be coupled to ground  104  whereas a second terminal  198  of adjustable component  152  is coupled to peripheral structures  16 ). Terminal  198  of adjustable component  152  may be interposed between terminal  194  of adjustable component  154  and gap  18 - 1 . Terminal  196  of adjustable component  152  may be interposed between terminal  192  of adjustable component  154  and gap  18 - 1 . Adjustable component  152  may include switching circuitry such as a single-pole double-throw (SP2T) switch or any other desired switching circuitry. Control circuitry  28  may adjust the switching circuitry in component  152  to tune the resonant frequency of antenna  40 , for example. 
     Adjustable component  160  may be coupled between ground  104  and peripheral structures  16  (e.g., a first terminal  200  of adjustable component  160  may be coupled to ground  104  whereas a second terminal  202  of adjustable component  160  is coupled to peripheral structures  16 ). Terminal  202  may be interposed between point  180  of feed leg  170  and gap  18 - 2 . Terminal  200  may be interposed between ground antenna feed terminal  100 - 1  and gap  18 - 2 . Adjustable component  160  may include switching circuitry such as a single-pole double-throw (SP2T) switch or any other desired switching circuitry. Control circuitry  28  may adjust the switching circuitry in component  160  to tune the resonant frequency of antenna  40 , for example. 
     In one suitable arrangement, adjustable component  152  may be identical to adjustable component  160 . Control circuitry  28  may control adjustable components  152  and  160  to both be in the same state at any given time, for example. Terminal  198  and  196  may, if desired, be located at the same distance with respect to gap  18 - 1  as terminals  200  and  202  are located with respect to gap  18 - 2  (e.g., components  152  and  160  may be symmetrically distributed about longitudinal axis  190 ). This example is merely illustrative. In general, adjustable component  152  may be coupled between ground  104  and peripheral structures  16  at any desired location between adjustable component  154  and gap  18 - 1  and adjustable component  160  may be coupled between ground  104  and peripheral structures  16  at any desired location between antenna feed P 1  and gap  18 - 2 . 
     During operation, components  152 ,  154 ,  158 , and  160  may form return paths for antenna  40  such as path  110  of  FIG. 4 . For example, return paths may be formed by components  152 ,  154 ,  158 , and/or  160  when switches in the adjustable components are closed to form a short circuit across slot  114 . Using switchable return paths and multiple selectively-activated antenna feeds may provide antenna  40  with flexibility to accommodate different loading conditions (e.g., different loading conditions that may arise due to the presence of a user&#39;s hand or other external object on various different portions of device  10  adjacent to various different corresponding portions of antenna  40 ). 
     Adjustable components such as components  152 ,  154 ,  156 ,  158 , and  160  (see, e.g., components  102  of  FIG. 3 ) may be used in adjusting the operation of antenna  40 . Components  152 ,  154 ,  156 ,  158 , and  160  may include switches such as adjustable return path switches, switches coupled to fixed components such as inductors and capacitors and other circuitry for providing adjustable amounts of capacitance, adjustable amounts of inductance, open and closed circuits, etc. Adjustable components in antenna  40  may be used to tune antenna coverage, may be used to restore antenna performance that has been degraded due to the presence of an external object such as a hand or other body part of a user, and/or may be used to adjust for other operating conditions and to ensure satisfactory operation at desired frequencies. 
     To enhance frequency coverage for antenna  40 , antenna  40  may be provided with a parasitic antenna resonating element such as parasitic antenna resonating element  162 . Element  162  may be formed from conductive structures such as conductive housing structures (e.g., an integral portion of housing such as a portion of housing  12  forming ground  104 ), from parts of conductive housing structures, from parts of electrical device components, from printed circuit board traces, from strips of conductor (e.g., strips of conductor or elongated portions of ground  104  that are embedded or molded into slot  114 ), or other conductive materials. In one suitable arrangement, parasitic antenna resonating element  162  is coupled to antenna resonating element  108  (e.g., peripheral structures  16 ) by near-field electromagnetic coupling and is used to modify the frequency response of antenna  40  so that antenna  40  operates at desired frequencies (e.g., parasitic element  162  may be indirectly fed via near-field coupling whereas peripheral structures  60  are directly fed using antenna feeds P 1  and P 2 ). As an example, parasitic antenna resonating element  162  may be based on a slot antenna resonating element structure (e.g., an open slot structure such as a slot with one open end and one closed end or a closed slot structure such as a slot that is completely surrounded by metal). If desired, slots for a slot-based parasitic antenna resonating element may be formed between opposing metal structures in peripheral structures  16  and/or antenna ground  104 . 
     Antenna  40  of  FIG. 6  may be used to cover radio-frequency communications in any desired communications bands.  FIG. 7  is a graph in which antenna efficiency has been plotted as a function of operating frequency f for an illustrative antenna such as antenna  40  of  FIG. 6  (e.g., including parasitic element  162 ). As shown in  FIG. 7 , antenna  40  may exhibit resonances in a low band LB, a midband MB, and a high band HB. 
     Low band LB may extend from 700 MHz to 960 MHz or may include any other suitable frequency range. Peripheral conductive structures  16  may serve as an inverted-F antenna resonating element arm such as arm  108  of  FIG. 4 . The resonance of antenna  40  at low band LB may be associated with the distance along peripheral conductive structures  16  between the active one of antenna feeds P 1  and P 2  and the farther of gaps  18 - 1  and  18 - 2  from the active antenna feed, for example. Aperture tuning circuitry  154  may be used to tune the response of antenna  40  in low band LB. As shown in  FIG. 7 , antenna  40  may have an antenna efficiency characterized by curve  220  in low band LB. The antenna efficiency of curve  220  may be achieved by adjusting aperture tuning circuitry  154  to place antenna  40  in one of three tuning states (e.g., a first state characterized by curve  222 , a second state characterized by curve  224 , and a third state characterized by curve  226 ). 
     High band HB may extend from 2300 MHz to 2700 MHz or within any other suitable frequency range. Antenna performance in high band HB may be supported by the resonance of parasitic antenna resonating element  162  (e.g., the length of element  162  may exhibit a quarter wavelength resonance at operating frequencies in band HB, etc.). 
     Midband MB may extend from 1710 MHz to 2170 MHz or within any other suitable frequency range. The resonance of antenna  40  at midband MB may be associated with the distance between the active one of antenna feeds P 1  and P 2  and a return path between peripheral structures  16  and ground  104  formed by one or more components  152 ,  154 ,  156 ,  158  and  160  of  FIG. 6 , for example. Control circuitry  28  may tune the resonance of antenna  40  within midband MB by adjusting components  152  and/or  160 , for example. 
     The presence or absence of external objects such as a user&#39;s hand or other body part in the vicinity of antenna  40  may affect antenna loading and therefore antenna performance. For example, in free space, the performance of antenna  40  in midband MB may be characterized by curve  228  of  FIG. 7 . In the presence of external loading, however, efficiency may be degraded (see, e.g., degraded efficiency curve  230 ). In the example of  FIG. 7 , efficiency in midband MB is degraded. However, in general, efficiency in any frequency bands covered by antenna  40  may be degraded due to the presence of external loading. 
     Antenna loading may differ depending on the way in which device  10  is being held and depending on which antenna feed is active. In the example of  FIG. 6 , antenna  40  is shown from the front of device  10  (e.g., through display  14 ). Edge  12 - 2  is associated with the right edge of housing  12  when device  10  is viewed from the front and edge  12 - 1  is associated with the left edge of housing  12  when device  10  is viewed from the front. In this example, when a user is holding device  10  in the user&#39;s right hand, the palm of the user&#39;s right hand will rest along edge  12 - 2  of housing  12  and the fingers of the user&#39;s right hand (which do not load antenna  40  as much as the user&#39;s palm) will rest along edge  12 - 1  of housing  12 . In this situation, if antenna feed P 1  is active, loading from the user&#39;s right hand may degrade the midband resonance of antenna  40  as shown by curve  230  of  FIG. 7 . Control circuitry  28  may detect the presence of the user&#39;s right hand in this scenario and, in response to such a detection, may deactivate antenna feed P 1  and activate antenna feed P 2 . Activating antenna feed P 2  may shift antenna current hotspots on peripheral structures  16  away from the right side (e.g., side  12 - 2 ) and towards the left side (e.g., side  12 - 1 ) of device  10 . This shift of current hotspots may reduce the loading and corresponding detuning of antenna  40  by the user&#39;s right hand. 
     When a user is holding device  10  in the user&#39;s left hand, the palm of the user&#39;s left hand will rest along the left edge of device  10  (e.g., housing edge  12 - 1  of  FIG. 6 ) and the fingers of the user&#39;s left hand will rest along edge  12 - 2  of device  10 . In this scenario, the palm of the user&#39;s hand may load the portion of antenna  40  near to edge  12 - 1 . If antenna feed P 2  is active, loading from the user&#39;s left hand may degrade the midband resonance of antenna  40  as shown by curve  230  of  FIG. 7 . Control circuitry  28  may detect the presence of the user&#39;s left hand in this scenario and, in response to such a detection, may deactivate antenna feed P 2  and activate antenna feed P 1 . Activating antenna feed P 1  may shift antenna current hotspots on peripheral structures  16  away from the left side  12 - 1  and towards right side  12 - 2  of device  10 . This shift of current hotspots may reduce the loading and corresponding detuning of antenna  40  by the user&#39;s left hand. 
     Control circuitry  28  may also adjust components  152 ,  154 ,  156 ,  158 , and  160  to ensure that antenna  40  remains properly tuned regardless of which antenna feed is active and regardless of which of the user&#39;s hand is being used to hold the device. For example, control circuitry  28  may place components  152 ,  154 ,  156 ,  158 , and  160  in a first tuning state (first tuning setting) when antenna  40  is being held by the user&#39;s right hand. Control circuitry  28  may place components  152 ,  154 ,  156 ,  158 , and  160  in a second tuning state (second tuning setting) when antenna  40  is being held by the user&#39;s left hand. Placing the adjustable components of antenna  40  in the first or second tuning states may undesirably detune the antenna in a free space scenario in which neither hand is loading the antenna. If desired, control circuitry  28  may place adjustable components  152 ,  154 ,  156 ,  158 , and  160  in a third tuning state (third tuning setting) when device  10  is operated in the free space scenario. Control circuitry  28  may activate antenna feed P 1  and deactivate antenna feed P 2  in the third tuning state, for example. 
     In one suitable arrangement, control circuitry  28  may place the adjustable components of antenna  40  in the first or second tuning states only when device  10  is being held adjacent to the head of the user (e.g., using the right or left hands respectively). The first tuning state may therefore sometimes be referred to herein as the right hand head mode of antenna  40  whereas the second tuning state is sometimes referred to herein as the left hand head mode of antenna  40 . Control circuitry  28  may place the adjustable components of antenna  40  in the third tuning state when device  10  is not being held adjacent to the head of a user or when neither of the user&#39;s hands is loading antenna  40 . The third tuning state may therefore sometimes be referred to herein as the free space mode of antenna  40 . By suitably controlling adjustable components  152 ,  154 ,  156 ,  158 , and  160  and selectively activating only one of antenna feeds P 1  and P 2  at a given time, control circuitry  28  may control antenna  40  to ensure that antenna  40  exhibits satisfactory midband antenna efficiency (e.g., as shown by curve  228  of  FIG. 7 ) regardless of whether device  10  is being held by the user&#39;s right or left hand or whether device  10  is operating in a free space environment. 
     The example of  FIGS. 6 and 7  is merely illustrative. If desired, the diagram of  FIG. 6  may illustrate device antenna  40  from the rear of device  10 . In this scenario, edge  12 - 2  is associated with the left edge of housing  12 , edge  12 - 1  is associated with the right edge of housing  12 , antenna feed P 1  may be activated when device  10  is held by the user&#39;s right hand, and antenna feed P 2  may be activated when device  10  is held by the user&#39;s left hand. Antenna ground plane  104  and slot  114  may have any desired shape. For example, ground plane  104  may have an extended portion that is closer to peripheral structures  16  than other portions of ground plane  104 . Slot  114  may, for example, have a U-shape or other meandering shape that runs around the extended portion of ground plane  104  between ground plane  104  and peripheral structures  16 . Antenna  40  may have any desired number of resonances in any desired frequency bands. In the example of  FIG. 6 , antenna  40  is formed as the lower antenna in region  20  of device  10  ( FIG. 1 ). If desired, the structures of  FIG. 6  may be used to form an upper antenna in region  22  for device  10  or an antenna at any other desired location within device  10 . 
     To ensure that antenna  40  operates satisfactorily when the user&#39;s right hand is being used to grip device  10  and when the user&#39;s left hand is being used to grip device  10  as well as during free space conditions, control circuitry  28  may determine which type of device operating environment is present and may adjust the adjustable circuitry of antenna  40  accordingly to compensate.  FIG. 8  is a flow chart of illustrative involved in operating device  10  to ensure satisfactory performance for antenna  40  in all desired frequency bands of interest. 
     At step  250  of  FIG. 8 , control circuitry  28  may monitor the operating environment of device  10 . Control circuitry  28  may, in general, use any suitable type of sensor measurements, wireless signal measurements, operation information, or antenna measurements to determine how device  10  is being used (e.g., to determine the operating environment of device  10 ). For example, control circuitry  28  may use sensors such as temperature sensors, capacitive proximity sensors, light-based proximity sensors, resistance sensors, force sensors, touch sensors, connector sensors that sense the presence of a connector in connector port  164  or that detect the presence or absence of data transmission through connector port  164 , sensors that detect whether wired or wireless headphones are being used with device  10 , sensors that identify a type of headphone or accessory device that is being used with device  10  (e.g., sensors that identify an accessory identifier identifying an accessory that is being used with device  10 ), or other sensors to determine how device  10  is being used. Control circuitry  28  may also use information from an orientation sensor such as an accelerometer in device  10  to help determine whether device  10  is being held in a position characteristic of right hand use or left hand use (or is being operated in free space). Control circuitry may also use information about a usage scenario of device  10  in determining how device  10  is being used (e.g., information identifying whether audio data is being transmitted through ear speaker  26  of  FIG. 1 , information identifying whether a telephone call is being conducted, information identifying whether a microphone on device  10  is receiving voice signals, etc.). If desired, an impedance sensor or other sensor may be used in monitoring the impedance of antenna  40  or part of antenna  40 . Different antenna loading scenarios may load antenna  40  differently, so impedance measurements may help determine whether device  10  is being gripped by a user&#39;s left or right hand or is being operated in free space. Another way in which control circuitry  28  may monitor antenna loading conditions involves making received signal strength measurements on radio-frequency signals being received with antenna  40 . In this example, the adjustable circuitry of antenna  40  can be toggled between different settings and an optimum setting for antenna  40  can be identified by choosing a setting that maximizes received signal strength. In general, any desired combinations of one or more of these measurements or other measurements may be processed by control circuitry  28  to identify how device  10  is being used (i.e., to identify the operating environment of device  10 ). 
     In a scenario where control circuitry  28  processes orientation information for determining the operating environment of device  10 , the orientation information may be gathered using an accelerometer from input-output devices  32  ( FIG. 2 ), for example. The accelerometer may measure a gravity vector having a direction that points towards the earth. Control circuitry  28  may identify the direction of the gravity vector to determine whether device  10  is being held by the user&#39;s left or right hand. For example, the gravity vector may have a first component that generally has a positive value when device  10  is being held by the user&#39;s left hand and a negative value when device  10  is being held by the user&#39;s right hand. Control circuitry  28  may identify the sign of this component of the gravity vector to determine whether device  10  is being held by the user&#39;s left or right hand. This is merely illustrative and, in general, any desired sensor data may be used. 
     At step  252 , control circuitry  28  may adjust the configuration of antenna  10  based on the current operating environment of device  10  (e.g., based on data or information gathered while processing step  250 ). For example, control circuitry  28  may process the data gathered while processing step  250  to determine whether device  10  is being held to the user&#39;s head by the user&#39;s right hand, whether device  10  is being held to the user&#39;s head by the user&#39;s left hand, or whether device  10  is in some other operating environment (e.g., a free space environment). If control circuitry  28  determines that device  10  is being held to the user&#39;s head by the user&#39;s right hand, control circuitry  28  may place antenna  40  in the right hand head mode (e.g., by placing tuning components  152 ,  154 ,  156 ,  158 , and  160  in the first tuning state, activating feed P 2 , and deactivating feed P 1 ). If control circuitry  28  determines that device  10  is being held to the user&#39;s head by the user&#39;s left hand, control circuitry  28  may place antenna  40  in the left hand head mode (e.g., by placing tuning components  152 ,  154 ,  156 ,  158 , and  160  in the second tuning state, activating feed P 1 , and deactivating feed P 2 ). If control circuitry  28  determines that device  10  is in any other operating environment, control circuitry  28  may place antenna  40  in the free space mode (e.g., by placing tuning components  152 ,  154 ,  156 ,  158 , and  160  in the tuning third state, activating feed P 1 , and deactivating feed P 2 ). By placing antenna  40  in one of these modes, control circuitry  28  may ensure that antenna  40  operates satisfactorily in all frequency bands of interest regardless of how the user is holding device  10 . 
     At step  254 , antenna  40  may be used to transmit and receive wireless data in using the currently activated antenna feed and setting for components  152 ,  154 ,  156 ,  158 , and  160 . This process may be performed continuously, as indicated by line  256 . 
       FIGS. 9-12  show illustrative examples of the electrical components that may be used in forming adjustable components  152 ,  154 ,  156 ,  158 , and  160  of  FIG. 6  and that may be adjusted to place antenna  40  into the right hand head mode, left hand head mode, or free space mode (e.g., while processing step  252  of  FIG. 8 ). 
       FIG. 9  is a circuit diagram showing circuit elements that may be used in forming adjustable components  152  and  160  of  FIG. 6 . As shown in  FIG. 9 , adjustable component  260  (e.g., an adjustable component such as component  152  or  156  of  FIG. 6 ) may include multiple inductors that are used in providing antenna  40  with an adjustable amount of inductance (e.g., component  260  may sometimes be referred to as an adjustable inductor or adjustable inductor circuitry). Control circuitry  28  may adjust adjustable inductor circuitry  260  of  FIG. 9  to produce different amounts of inductance between terminal  262  (e.g., terminal  196  when implementing adjustable component  152  of  FIG. 6  or terminal  200  when implementing adjustable component  160  of  FIG. 6 ) and terminal  264  (e.g., terminal  198  when implementing adjustable component  152  or terminal  202  when implementing adjustable component  160 ) by controlling the state of switching circuitry such as switch  266  using control signals on control input  268 . Switch  266  may be, for example, a single-pole double-throw (SP2T) switch. 
     Control signals on path  268  may be used to switch inductor L 1  into use between terminals  262  and  264  while switching inductor L 2  out of use, may be used to switch inductor L 2  into use between terminals  262  and  264  while switching inductor L 1  out of use, may be used to switch both inductors L 1  and L 2  into use in parallel between terminals  262  and  264 , or may be used to switch both inductors L 1  and L 2  out of use. The switching circuitry arrangement of adjustable inductor  260  of  FIG. 9  is therefore able to produce one or more different inductance values, two or more different inductance values, three or more different inductance values, or, if desired, four different inductance values (e.g., L 1 , L 2 , L 1  and L 2  in parallel, or infinite inductance when L 1  and L 2  are switched out of use simultaneously). When at least one of inductors L 1  and L 2  is switched into use, a return path is formed between antenna ground  104  and peripheral structures  16 . Control circuitry  28  may adjust the inductance provided by adjustable inductor circuitry  260  to tune the resonant frequency of antenna  40  within midband MB, for example. If desired, the same control signal may be provided to adjustable inductor circuitry  260  in both adjustable components  152  and  160  ( FIG. 6 ) so that both components exhibit the same inductance at a given time. This may allow tuning in midband MB regardless of which of antenna ports P 1  and P 2  is active. 
       FIG. 10  is a circuit diagram showing circuit elements that may be used in forming adjustable component  156  of  FIG. 6 . As shown in  FIG. 10 , adjustable component  156  may include inductor L 2  coupled in series with switch  270  between positive antenna feed terminal  98 - 2  of antenna feed P 2  and terminal  182  (e.g., adjustable component  156  may be interposed on antenna feed path  168 ). Switch  270  may be, for example, a single-pole single-throw (SPST) switch. Adjustable component  156  can be adjusted to produce different amounts of inductance between terminals  98 - 2  and  182 . Component  156  may therefore sometimes be referred to herein as adjustable inductor or switchable inductor circuitry  156 . Control circuitry  28  may control switch  270  using control signals on input  272 . When switch  270  is placed in a closed state, inductor L 3  is switched into use and adjustable inductor  156  exhibits an inductance L 3  between terminals  122  and  124 . Antenna signals may be conveyed over feed terminal  98 - 2  to peripheral structures  16  through closed switch  270  and inductor L 3 . When switch  270  is placed in an open state, inductor L 3  is switched out of use and adjustable inductor  156  exhibits an essentially infinite amount of inductance between terminals  98 - 2  and  182 . Antenna signals may not be conveyed over feed terminal  98 - 2  and peripheral structures  16  when switch  270  is opened. If desired, switch  270  may be opened when antenna feed P 2  is disabled. 
       FIG. 11  is a circuit diagram showing circuit elements that may be used in forming adjustable component  158  of  FIG. 6 . As shown in  FIG. 11 , adjustable component  158  may include an inductor L 4  coupled in series with first switch  282  between antenna feed path  170  and ground  104 . Component  158  may include a resistor  286  coupled in series with second switch  284  between signal antenna feed path  170  and ground  104 . Switches  282  and  284  may be, for example, single-pole single-throw (SPST) switches. Collectively, component  158  may be, for example, a shunt single-pole double-throw switch that selectively forms a shunt path from feed path  170  to ground  104 . 
     Resistor  286  in adjustable component  158  may, for example, have a resistance of 0 Ohms or any other desired resistance. Control circuitry  28  may provide control signals over control input  280  to selectively open and close switches  282  and  284 . Control circuitry  28  may close switch  284  and open switch  282  to short antenna signals on peripheral structures  16  to ground  104 . This may effectively form a return path such as return path  110  of  FIG. 4  from peripheral structures  16  to ground  104  at the location of terminal  180 . Control circuitry  28  may close switch  284  and open switch  282  when antenna feed P 1  is disabled, for example. When antenna feed P 1  is enabled, switch  284  may be in an open state so that antenna signals may flow between terminals  98 - 1  and  180  without being shunted to ground. Control circuitry  28  may open or close switch  282  to adjust the inductance of antenna  40  at the location of feed conductor  170  if desired. The example of  FIG. 11  in which component  158  is coupled between feed arm  170  and ground  104  is merely illustrative. If desired, component  158  may be coupled between any desired location on signal conductor  94  of transmission line  92  ( FIG. 3 ) and ground  104 . Inductor L 4  may, if desired, be omitted from adjustable component  158 . 
       FIG. 12  is a circuit diagram showing circuit elements that may be used in forming adjustable aperture tuning circuitry  154  of  FIG. 6 . As shown in  FIG. 12 , adjustable component  154  may include a resistor  300  coupled in series with switch  308 , a first inductor L 5  coupled in series with switch  302 , a second inductor L 6  coupled in series with switch  304 , and a third inductor L 7  coupled in series with switch  306  in parallel between terminal  192  and terminal  194 . Inductors L 5 -L 7  may be used in providing antenna  40  with an adjustable amount of inductance. Control circuitry  28  may adjust component  154  to produce different amounts of inductance between terminal  192  and terminal  194  by controlling the state of switching circuitry such as switches  302 - 308  using control signals on control input  310 . Switches  302 - 308  may each be, for example, single-pole single-throw (SPST) switches. Resistor  300  may have a resistance of 0 Ohms or any other desired resistance. 
     Control signals on path  310  may be used to switch any desired combination of one or more of inductors L 5 -L 7  and resistor  300  into use between terminals  192  and  194 . As an example, control circuitry  28  may close switch  308  while opening switches  302 - 306  to switch resistor  300  into use between terminals  192  and  194 . In this scenario, antenna signals on peripheral conductive structures  16  may be shorted to from terminal  194  to ground  104  at terminal  192  (e.g., circuitry  154  may form a return path such as return path  110  of  FIG. 4  for antenna  40 ). If desired, control circuitry  28  may open switch  308  while closing one or more of switches  302 - 306  to adjust the inductance provided by aperture tuning circuitry  154 . Switching different combinations of inductors L 5 -L 7  into use between terminals  192  and  194  may tune the resonance of antenna  40  within low band LB. For example, control circuitry  28  may close switch  302  and open switches  304 - 308  to tune the low band performance of antenna  40  as shown by curve  222  of  FIG. 7 , may close switch  304  and open switches  302 ,  306 , and  308  to tune the low band performance of antenna  40  as shown by curve  224 , and may close switch  306  and open switches  302 ,  304 , and  308  to tune the low band performance of antenna  40  as shown by curve  226 . The example of  FIG. 12  is merely illustrative. In general, there may be any desired number of inductors coupled in parallel between terminals  192  and  194 . The examples of  FIGS. 9-12  are merely illustrative. In general, adjustable components  152 ,  154 ,  156 ,  158 , and  160  may each include any desired number of inductive, capacitive, resistive, and switching elements arranged in any desired manner (e.g., in series, in parallel, in shunt configurations, etc.). 
     If desired, additional switching circuitry may be coupled between radio-frequency transceiver circuitry  90  and antenna feeds P 1  and P 2  for selectively activating one of antenna feeds P 1  and P 2  at a given time.  FIG. 13  is a schematic diagram showing how additional switching circuitry may be used to selectively activate antenna feeds for antenna  40 . As shown in  FIG. 13 , switching circuit  320  may be interposed on signal conductor  94  of transmission line  92 . Control circuitry  28  may provide control signals to switching circuit  320  over input  322 . Control circuitry  28  may control switch  320  to selectively route radio-frequency signals between transceiver circuitry  90  and antenna feed terminal  98 - 2  of antenna feed P 2  and between transceiver circuitry  90  and antenna feed terminal  98 - 1  of antenna feed P 1 . When antenna feed P 2  is active, control circuitry  28  may place switch  320  in a first state in which signals are routed between transceiver  90  and feed terminal  98 - 2 . When antenna feed P 1  is to be activated, control circuitry  28  may place switch  320  in a second state in which signals are routed between transceiver  90  and feed terminal  98 - 1 . This example is merely illustrative. In general, switching circuitry  320  may include any desired number of switches arranged in any desired configuration. Switching circuitry  320  may be omitted if desired (e.g., antenna feeds P 1  and P 2  may be selectively activated using only adjustable circuitry  156  and  158  of  FIG. 6 ). 
     Control circuitry  28  may adjust the switching circuitry of  FIGS. 9-13  when placing antenna  40  in the left hand head mode, right hand head mode, and free space mode (e.g., while processing step  252  of  FIG. 8  to ensure that the optimal antenna feed is activated and that the adjustable components of antenna  40  are placed in a suitable configuration to ensure optimal antenna efficiency in each frequency band of interest). Control circuitry  28  may adjust the switching circuitry of  FIGS. 9-13  based on the monitored operating environment of device  10 . 
     A state diagram showing illustrative operating modes for antenna  40  is shown in  FIG. 14 . As shown in  FIG. 14 , antenna  40  may be operable in a free space mode  360 , a left hand head mode  362 , and a right hand head mode  364 . Control circuitry  28  may identify which mode is to be used based on the monitored operating environment of device  10  (e.g., using the sensor data and other information gathered while processing step  250  of  FIG. 8 ) and may adjust tunable components  152 ,  154 ,  156 ,  158 , and  160  of  FIG. 6  to place antenna  40  in the corresponding operating mode. 
     When operating in free space mode  360 , control circuitry  28  may enable antenna feed P 1  and may disable antenna feed P 2 . For example, control circuitry  28  may control switch  320  of  FIG. 13  to route signals between transceiver  90  and antenna feed terminal  98 - 1  of antenna feed P 1 . If desired, control circuitry  28  may open switch  270  in adjustable component  156  ( FIG. 10 ) to decouple antenna feed terminal  98 - 2  from peripheral structures  16  instead of or in addition to adjusting switch  320 . Control circuitry  28  may open switches  284  and  286  in adjustable component  158  ( FIG. 11 ) so that radio-frequency signals are routed from antenna feed terminal  98 - 1  to point  180  on peripheral structures  16 . When it is desired to transmit and receive low band signals in band LB, control circuitry  28  may control the switches of aperture tuning circuit  154  to switch an appropriate one of inductors L 5 , L 6 , and L 7  into use, thereby tuning the low band response of antenna  40 . The low band response of antenna  40  may be supported by, for example, resonance of the portion of conductive structures  16  to the left of feed P 1  or any other desired portion of conductive structures  16  and antenna ground  104 . Control circuitry  28  may, if desired, control switching circuitry  260  of adjustable components  152  and/or  160  ( FIG. 9 ) to tune antenna  40  to a desired frequency within midband MB. The midband response of antenna  40  may be supported by, for example, resonance of the portion of conductive structures  16  to the right of feed P 1  or any other desired portion of conductive structures  16  and antenna ground  104 . Peripheral structures  16  may indirectly feed parasitic element  162  ( FIG. 6 ) via near field coupling to provide coverage in high band HB. In free space mode  360 , antenna  40  may cover frequencies in low band LB, midband MB, and high band HB ( FIG. 7 ) with satisfactory antenna efficiency. 
     In free space mode  360 , control circuitry  28  may collect and analyze sensor data such as proximity sensor data, orientation sensor data, connector sensor data, temperature sensor data, and other sensor data, may collect and analyze received signal strength data, call state data, data indicative of whether audio is being played through ear speaker  26  ( FIG. 1 ), data indicative of what type of headphones or other accessories are being used with device  10 , and information about other wireless settings, and may collect and analyze antenna performance information such as antenna impedance information and other antenna feedback information to determine whether device  10  is being used in an operating environment such as a left hand head environment or right hand head environment that loads antenna  40  in a way that can be compensated by adjusting the adjustable circuitry of antenna  40 . Control circuitry  28  may continue to operate antenna  40  in free space mode  360  while the gathered information indicates that device  10  has not entered the left or right hand head device operating environments. Control circuitry  28  may, for example, operate antenna  40  in free space mode  360  when the data gathered while processing step  250  of  FIG. 8  indicates that device  10  is not being used adjacent to the user&#39;s head and/or when the data indicates that device  10  is not being held by the user&#39;s left or right hand. 
     If it is determined that device  10  is being held in the left hand of a user and adjacent to the user&#39;s head (e.g., a non-free-space operating environment in which antenna  40  is being loaded along edge  12 - 1  and device  10  is adjacent to the user&#39;s head), control circuitry  28  may adjust the circuitry of antenna  40  to place antenna  40  in left hand head mode  362 . When operating in left hand head mode  362 , control circuitry  28  may enable antenna feed P 1  and may disable antenna feed P 2 . For example, control circuitry  28  may control switch  320  of  FIG. 13  to route signals between transceiver  90  and antenna feed terminal  98 - 1  of antenna feed P 1 . If desired, control circuitry  28  may open switch  270  in adjustable component  156  ( FIG. 10 ) to decouple antenna feed terminal  98 - 2  from peripheral structures  16  instead of or in addition to adjusting switch  320 . Control circuitry  28  may open switches  284  and  286  in adjustable component  158  ( FIG. 11 ) so that radio-frequency signals are routed from antenna feed terminal  98 - 1  to point  180  on peripheral structures  16 . 
     Control circuitry  28  may close switch  308  of aperture tuning circuitry  154  to short terminal  194  on conductive structures  16  to terminal  192  on ground  104  ( FIG. 12 ). This may short antenna currents on peripheral structures  16  to ground  104  at the location of aperture tuner  154  so that the state of adjustable circuit  152  has no effect on the resonant frequency of antenna  40  (e.g., antenna currents do not pass through component  152  because the currents are shorted to ground prior to reaching component  152 ). Control circuitry  28  may control switch  266  of adjustable component  160  to switch at least one of inductors L 1  and L 2  into use between terminals  202  and  200  ( FIG. 9 ) and to adjust the resonant frequency of antenna  40  within midband MB. In left hand head mode  362 , antenna  40  may cover frequencies in midband MB and high band HB (e.g., coverage in low band LB may not be supported by left hand head mode  362 ). The midband response of antenna  40  may be supported by, for example, resonance of the portion of conductive structures  16  to the right of aperture tuning circuitry  154  or any other desired portion of conductive structures  16  and antenna ground  104 . Peripheral structures  16  may indirectly feed parasitic element  162  ( FIG. 6 ) via near field coupling to provide coverage in high band HB. 
     By operating antenna  40  in this way during left hand head mode  362 , antenna current hotspots may be shifted away from left side  12 - 1  and towards right side  12 - 2  of device  10 . This may mitigate the loading of antenna  40  by the user&#39;s left hand and any corresponding detuning of antenna  40 . In left hand head mode  362 , control circuitry  28  may monitor for conditions indicating that device  10  is being operated in a free space environment (in which case device  10  can transition to mode  360 ) or is being held in the right hand and adjacent to the head of the user (in which case device  10  can transition to right hand head mode  364 ). Control circuitry  28  may continue to operate antenna  40  in left hand head mode  362  while the gathered information indicates that device  10  has not entered the right hand head operating environment or the free space operating environment. Control circuitry  28  may, for example, operate antenna  40  in left hand head mode  360  when the data gathered while processing step  250  of  FIG. 8  indicates that device  10  is being used adjacent to the user&#39;s head and that device  10  is being held by the user&#39;s left hand. 
     If it is determined that device  10  is being held in the right hand of a user and adjacent to the user&#39;s head (e.g., a non-free-space operating environment in which antenna  40  is being loaded along edge  12 - 2  and device  10  is adjacent to the user&#39;s head), control circuitry  28  may adjust the circuitry of antenna  40  to place antenna  40  in right hand head mode  364 . When operating in right hand head mode  364 , control circuitry  28  may enable antenna feed P 2  and may disable antenna feed P 1 . For example, control circuitry  28  may control switch  320  of  FIG. 13  to route signals between transceiver  90  and antenna feed terminal  98 - 2  of antenna feed P 2 . If desired, control circuitry  28  may close switch  270  in adjustable component  156  ( FIG. 10 ) to couple antenna feed terminal  98 - 2  to peripheral structures  16 . Control circuitry  28  may close switch  284  in adjustable component  158  ( FIG. 11 ) so that radio-frequency antenna signals on peripheral structures  16  are shorted to ground  104  through zero-ohm resistor  286  instead of passing to antenna feed terminal  98 - 1 . Because the antenna currents are shorted to ground  104  by adjustable component  158  in this mode, the state of adjustable circuit  160  has no effect on the resonant frequency of antenna  40  (e.g., antenna currents do not pass through component  160  because the currents are shorted to ground at element  158  prior to reaching component  160 ). 
     Control circuitry  28  may control switch  266  in adjustable component  152  to switch at least one of inductors L 1  and L 2  of adjustable component  152  into use between terminals  196  and  198 . This may adjust the resonant frequency of antenna  40  within midband MB. Control circuitry  28  may open switch  308  of aperture tuning circuitry  154  to decouple resistor  300  from ground ( FIG. 12 ). Control circuitry  28  may control switches  302 - 306  of  FIG. 12  to couple one or more of inductors L 5 -L 7  to ground. In this configuration (e.g., when feed P 2  is active and P 1  is inactive), aperture tuning circuitry  154  may form adjustable matching circuitry having an adjustable impedance that is controlled by opening and closing switches  302 - 306  to adjust the antenna efficiency of antenna  40 . 
     In right hand head mode  364 , antenna  40  may cover frequencies in midband MB and high band HB (e.g., coverage in low band LB may not be supported by right hand head mode  364 ). The midband response of antenna  40  may be supported by, for example, resonance of the portion of conductive structures  16  to the left of disabled antenna feed P 1  or any other desired portion of conductive structures  16  and antenna ground  104 . Peripheral structures  16  may indirectly feed parasitic element  162  ( FIG. 6 ) via near field coupling to provide coverage in high band HB. 
     By operating antenna  40  in this way during right hand head mode  364 , antenna current hotspots may be shifted away from right side  12 - 2  and towards left side  12 - 1  of device  10 . This may mitigate the loading of antenna  40  by the user&#39;s right hand and any corresponding detuning of antenna  40 . In right hand head mode  364 , control circuitry  28  may monitor for conditions indicating that device  10  is being operated in free space (in which case device  10  can transition to mode  360 ) or is being held in the left hand and adjacent to the head of the user (in which case device  10  can transition to left hand head mode  362 ). Control circuitry  28  may continue to operate antenna  40  in right hand head mode  364  while the gathered information indicates that device  10  has not entered the left hand head operating environment or free space operating environment. Control circuitry  28  may, for example, operate antenna  40  in right hand head mode  364  when the data gathered while processing step  250  of  FIG. 8  indicates that device  10  is being used adjacent to the user&#39;s head and that device  10  is being held by the user&#39;s right hand. 
       FIG. 15  is a flow chart of exemplary steps that may be performed by control circuitry  28  in switching between operating modes for antenna  40 . At step  400 , control circuitry  28  may begin to collect sensor data such as proximity sensor data, orientation sensor data, connector sensor data, temperature sensor data, information about the type of headphones or other accessories that are being used with device  10 , and other sensor data, may begin to collect received signal strength data, call state data, data indicative of whether audio is being played through ear speaker  26  ( FIG. 1 ), and other wireless settings, and/or may begin to collect antenna performance information such as antenna impedance information and other antenna feedback information. This data may be indicative of the operating environment of device  10 . Control circuitry  28  may continue to collect this data and information while processing the steps of  FIG. 15 . 
     At step  402 , control circuitry  28  may process the gathered data and information indicative of the operating environment of device  10  to determine whether device  10  is being held adjacent to the head of a user. If control circuitry  28  determines that device  10  is being held adjacent to the head of a user, processing may proceed to step  410  as shown by path  408 . If control circuitry  28  determines that device  10  is not being held adjacent to the head of a user, processing may proceed to step  406  as shown by path  404 . 
     As one example, control circuitry  28  may determine that device  10  is adjacent to the head of a user when it is determined that audio data is being played through ear speaker  26  ( FIG. 1 ) and may determine that device  10  is not adjacent to the head of a user when it is determined that no audio data is being played through ear speaker  26 . This example is merely illustrative. In general, any desired combination of data gathered at step  400  may be used to make the determination of step  402 . 
     At step  406 , control circuitry  28  may place antenna  40  in free space mode  360  (FIG.  14 ). In other words, control circuitry  28  may operate antenna  40  in free space mode  360  whenever device  10  is not being held adjacent to the head of a user. If desired, processing may loop back to step  402  as shown by path  420  to continually monitor whether device  10  has been moved adjacent to the head of a user. 
     At step  410 , control circuitry  28  may process the gathered data and information indicative of the operating environment of device  10  to determine whether device  10  is being held in the user&#39;s left hand or right hand. If control circuitry  28  determines that device  10  is being held in the user&#39;s left hand, processing may proceed to step  416  as shown by path  412 . If control circuitry  28  determines that device  10  is being held in the user&#39;s right hand, processing may proceed to step  418  as shown by path  414 . 
     At step  416 , control circuitry  28  may place antenna  40  in left hand head mode  362 . In other words, control circuitry  28  may operate antenna  40  in left hand head mode whenever device  10  is determined to be held in the user&#39;s left hand and adjacent to the user&#39;s head. If desired, processing may loop back to step  402  as shown by path  420  to continually monitor device  10  for changes in operating environment. For example, control circuitry  28  may update the operating mode of antenna  40  when it is determined that device  10  has moved away from the user&#39;s head and/or been moved to the user&#39;s right hand. 
     At step  418 , control circuitry  28  may place antenna  40  in right hand head mode  364 . In other words, control circuitry  28  may operate antenna  40  in right hand head mode whenever device  10  is determined to be held in the user&#39;s right hand and adjacent to the user&#39;s head. If desired, processing may loop back to step  402  as shown by path  420  to continually monitor device  10  for changes in operating environment. For example, control circuitry  28  may update the operating mode of antenna  40  when it is determined that device  10  has moved away from the user&#39;s head and/or been moved to the user&#39;s left hand. In some scenarios, the gathered data indicative of the operating environment of device  10  may indicate that neither hand is adjacent to antenna  40  (e.g., that the user is not holding device  10  even though control circuitry  28  determined that device  10  is adjacent to the user&#39;s head). In this scenario, processing may jump to step  406  to place antenna  40  in free space mode  360 . If desired, control circuitry may adjust the transmit power level of antenna  40  based on the gathered information and data indicative of the operating environment of device  10  (e.g., to minimize signal absorption by the user&#39;s body while also ensuring satisfactory communications link quality and conserving battery power). In this way, control circuitry  28  may continually monitor the operating environment of device  10  to ensure that antenna  40  has satisfactory antenna efficiency in each band of interest regardless of how device  10  is being held by a user. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20180329
Publication Date: 20191105
Grant Date: 20191105
Priority Date: 20160922
Inventors: HAN, XU
HAN, LIANG
MOW, MATTHEW A.
TSAI, MING-JU
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/401", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/50", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q23/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q19/021", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q19/021", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 61620627