PATENT DOCUMENT

Publication Number: US-10305453-B2
Application Number: US-201715700580-A
Country: US
Kind Code: B2

Title: Electronic device antennas having multiple operating modes

Abstract:
An electronic device may be provided with wireless circuitry and control circuitry. The wireless circuitry may include an antenna with an inverted-F antenna resonating element formed from portions of a peripheral conductive electronic device housing structure and may have an antenna ground that is separated from the antenna resonating element by a gap. The antenna may include a first adjustable component coupled between the antenna resonating element arm and the antenna ground on a first side of the antenna feed and a second adjustable component coupled between the antenna resonating element arm and the antenna ground on a second side of the antenna feed. Control circuitry in the electronic device may adjust the first and second adjustable components between a first tuning mode, a second tuning mode, and a third tuning mode.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing having peripheral conductive housing structures; 
 an antenna resonating element arm formed from a segment of the peripheral conductive housing structures; 
 an antenna ground; 
 an antenna feed having a positive antenna feed terminal coupled to the antenna resonating element arm and a ground antenna feed terminal coupled to the antenna ground; 
 a first adjustable component coupled between the antenna resonating element arm and the antenna ground on a first side of the antenna feed; 
 a second adjustable component coupled between the antenna resonating element arm and the antenna ground on a second side of the antenna feed; and 
 control circuitry configured to adjust the first and second adjustable components between a first tuning mode in which the first adjustable component forms an open circuit between the antenna resonating element arm and the antenna ground and the second adjustable component electrically couples the antenna resonating element arm to the antenna ground, a second tuning mode in which the second adjustable component forms an open circuit between the antenna resonating element arm and the antenna ground and the first adjustable component electrically couples the antenna resonating element arm to the antenna ground, and a third tuning mode in which both the first and second adjustable components electrically couple the antenna resonating element arm to the antenna ground. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the antenna resonating element arm has opposing first and second ends and, while the first and second adjustable components are in the first tuning mode, a first portion of the antenna resonating element arm between the antenna feed and the first end is configured to convey radio-frequency signals in a first frequency band and a second portion of the antenna resonating element arm between the antenna feed and the second end is configured to convey radio-frequency signals in a second frequency band. 
     
     
       3. The electronic device defined in  claim 2  wherein, while the first and second adjustable components are in the second tuning mode, a third portion of the antenna resonating element arm between the first adjustable component and the second end of the antenna resonating element arm is configured to convey radio-frequency signals in the first frequency band and a fourth portion of the antenna resonating element arm between the first adjustable component and the first end of the antenna resonating element arm is configured to convey radio-frequency signals in the second frequency band. 
     
     
       4. The electronic device defined in  claim 3  wherein, while the first and second adjustable components are in the third tuning mode, a conductive loop path including the first adjustable component, a portion of the antenna ground, the second adjustable component, and a fifth portion of the antenna resonating element arm between the first and second adjustable components is configured to convey radio-frequency signals in the second frequency band and a third frequency band. 
     
     
       5. The electronic device defined in  claim 4 , further comprising:
 first and second dielectric-filled gaps that divide the peripheral conductive housing structures, wherein the first end of the antenna resonating element arm is defined by the first dielectric-filled gap and the second end of the antenna resonating element arm is defined by the second dielectric-filled gap. 
 
     
     
       6. The electronic device defined in  claim 5 , wherein the antenna ground includes a first vertical slot that extends beyond an edge of the first dielectric-filled gap, the first vertical slot has edges defined by the antenna ground and the peripheral conductive housing structures, the antenna ground includes a second vertical slot that extends beyond an edge of the second dielectric-filled gap, and the second vertical slot has edges defined by the antenna ground and the peripheral conductive housing structures. 
     
     
       7. The electronic device defined in  claim 6  wherein, while the first and second adjustable components are in the first tuning mode, the first vertical slot is configured to convey radio-frequency signals in the third frequency band. 
     
     
       8. The electronic device defined in  claim 7 , wherein the first frequency band comprises frequencies between 700 MHz and 960 MHz, the second frequency band comprises frequencies between 1710 MHz and 2170 MHz, and the third frequency band comprises frequencies between 2300 MHz and 2700 MHz. 
     
     
       9. The electronic device defined in  claim 1 , wherein the first adjustable component comprises at least one inductor and switching circuitry that selectively couples the at least one inductor between the antenna resonating element arm to the antenna ground. 
     
     
       10. The electronic device defined in  claim 9 , wherein the second adjustable component comprises at least one inductor and switching circuitry that selectively couples the at least one inductor between the antenna resonating element arm to the antenna ground. 
     
     
       11. The electronic device defined in  claim 1 , further comprising:
 a display, wherein the antenna ground comprises conductive portions of the display. 
 
     
     
       12. The electronic device defined in  claim 1 , further comprising:
 a transmission line coupled to the antenna feed, wherein a distributed capacitance is formed between the antenna ground and the antenna resonating element arm that impedance matches the antenna resonating element arm to the transmission line. 
 
     
     
       13. An electronic device, comprising:
 a housing having peripheral conductive structures; 
 an antenna resonating element arm formed from a segment of the peripheral conductive structures that extends between first and second dielectric-filled gaps in the peripheral conductive structures; 
 an antenna ground; 
 an antenna feed having a positive antenna feed terminal coupled to the antenna resonating element arm and a ground antenna feed terminal coupled to the antenna ground; 
 a first antenna tuning component coupled between a first location on the antenna resonating element arm and the antenna ground; and 
 a second antenna tuning component coupled between a second location on the antenna resonating element arm and the antenna ground, wherein the positive antenna feed terminal is interposed between the first and second locations, a first portion of the antenna resonating element arm extending between the first dielectric-filled gap and the positive antenna feed terminal is configured to convey radio-frequency signals in a given frequency band while the first and second antenna tuning components are placed in a first tuning mode, a second portion of the antenna resonating element arm extending between the second location and the second dielectric-filled gap is configured to convey radio-frequency signals in the given frequency band while the first and second antenna tuning components are placed in a second tuning mode, and a third portion of the antenna resonating element arm extending between the first and second locations is configured to convey radio-frequency signals in the given frequency band while the first and second antenna tuning components are placed in a third tuning mode. 
 
     
     
       14. The electronic device defined in  claim 13 , further comprising:
 control circuitry configured to place the first and second antenna tuning components in a selected one of the first tuning mode, the second tuning mode, and the third tuning mode. 
 
     
     
       15. The electronic device defined in  claim 14 , wherein the given frequency band is a first frequency band and a fourth portion of the antenna resonating element arm extending between the positive antenna feed terminal and the second dielectric-filled gap is configured to convey radio-frequency signals in a second frequency band that is lower than the first frequency band while the first and second antenna tuning components are placed in the first tuning mode. 
     
     
       16. The electronic device defined in  claim 15 , wherein a fifth portion of the antenna resonating element arm extending between the second location and the first dielectric-filled gap is configured to convey radio-frequency signals in the second frequency band while the first and second antenna tuning components are placed in the second tuning mode. 
     
     
       17. The electronic device defined in  claim 16 , wherein the electronic device does not transmit radio-frequency signals in the second frequency band using the antenna resonating element arm while the first and second antenna tuning components are placed in the third tuning mode. 
     
     
       18. An electronic device comprising:
 an antenna resonating element arm; 
 an antenna ground; 
 an antenna feed having a positive antenna feed terminal coupled to the antenna resonating element arm and a ground antenna feed terminal coupled to the antenna ground; 
 a first antenna tuning component coupled between a first location on the antenna resonating element arm and the antenna ground; 
 a second antenna tuning component coupled between a second location on the antenna resonating element arm and the antenna ground; and 
 control circuitry configured to adjust the first and second antenna tuning components between a first tuning mode in which the first antenna tuning component, a portion of the antenna ground, the second antenna tuning component, and a portion of the antenna resonating element arm are configured to resonate in a given frequency band and a second tuning mode in which the first antenna tuning component forms an open circuit between the antenna resonating element arm and the antenna ground. 
 
     
     
       19. The electronic device defined in  claim 18 , wherein the first and second antenna tuning components are both electrically connected between the antenna resonating element arm and the antenna ground in the first tuning mode. 
     
     
       20. The electronic device defined in  claim 18 , wherein the first antenna tuning component comprises first and second inductors coupled in parallel between the first location on the antenna resonating element arm and the antenna ground and switching circuitry configured to selectively couple the first and second inductors between the antenna resonating element arm and the antenna ground and the second antenna tuning component comprises third and fourth inductors coupled in parallel between the second location on the antenna resonating element arm and the antenna ground and switching circuitry configured to selectively couple the third and fourth inductors between the antenna resonating element arm and the antenna ground.

Description:
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 be provided with wireless circuitry and control circuitry. The wireless circuitry may include multiple antennas and transceiver circuitry. The antennas may include antenna structures at opposing first and second ends of the electronic device. The antenna structures at a given end of the device may include adjustable components that are adjusted by the control circuitry to place the antenna structures and the electronic device in one of a number of different operating modes or states. 
     The antenna may have an inverted-F antenna resonating element formed from portions of a peripheral conductive electronic device housing structure and may have an antenna ground that is separated from the antenna resonating element by a gap. A short circuit path may bridge the gap. An antenna feed may be coupled across the gap in parallel with the short circuit path. 
     The antenna may include a first adjustable component coupled between the antenna resonating element arm and the antenna ground on a first side of the antenna feed and a second adjustable component coupled between the antenna resonating element arm and the antenna ground on a second side of the antenna feed. Control circuitry in the electronic device may adjust the first and second adjustable components between a first tuning mode, a second tuning mode, and a third tuning mode. 
     In the first tuning mode, the first adjustable component may form an open circuit between the antenna resonating element arm and the antenna ground whereas the second adjustable component may electrically couple the antenna resonating element arm to the antenna ground. In the second tuning mode, the second adjustable component may form an open circuit between the antenna resonating element arm and the antenna ground whereas the first adjustable component may electrically couple the antenna resonating element arm to the antenna ground. In the third tuning mode, both the first and second adjustable components may electrically couple the antenna resonating element arm to the antenna ground. 
     In the first tuning mode, the antenna may be configured to operate with a relatively high antenna efficiency if the device is being held by a user&#39;s right hand, whereas in the second tuning mode the antenna may be configured to operate with a relatively high antenna efficiency if the device is being held by a user&#39;s left hand. In the third tuning mode, the antenna may be configured to operate with a relatively high efficiency regardless of which hand a user is using to hold the device. 
    
    
     
       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 communications 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 top view of illustrative antenna structures that are adjustable between multiple operating modes in an electronic device in accordance with an embodiment. 
         FIG. 6  is a top view of the illustrative antenna structures of  FIG. 5  while placed in a first operating mode in accordance with an embodiment. 
         FIG. 7  is a top view of the illustrative antenna structures of  FIG. 5  while placed in a second operating mode in accordance with an embodiment. 
         FIG. 8  is a top view of the illustrative antenna structures of  FIG. 5  while placed in a third operating mode in accordance with an embodiment. 
         FIG. 9  is a graph of antenna efficiency as a function of frequency for an illustrative antenna of the type shown in  FIGS. 5-8  in accordance with an embodiment. 
         FIG. 10  is a flow chart of illustrative steps that may be involved in operating an electronic device having an antenna of the type shown in  FIGS. 5-8  in accordance with an embodiment. 
         FIG. 11  is a state diagram showing illustrative antenna operating modes for an electronic device with an antenna of the type shown in  FIGS. 5-8  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, 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 structures 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 and/or an antenna resonating element formed from conductive housing structures (e.g., internal and/or external structures, support plate structures, etc.). 
     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 (e.g., glass, ceramic, plastic, sapphire, etc.). 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 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. The rear housing wall may include conductive portions and/or dielectric portions. If desired, the rear housing wall may include a planar metal layer covered by a thin layer or coating of dielectric such as glass, plastic, sapphire, or ceramic. 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 if desired. 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, 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 or wall. 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. Peripheral conductive housing structures  16  and/or the conductive rear wall of housing  12  may form one or more exterior surfaces of device  10  (e.g., surfaces that are visible to a user of device  10 ) and/or may be implemented using internal structures that do not form exterior surfaces of device  10  (e.g., conductive housing structures that are not visible to a user of device  10  such as conductive structures that are covered with layers such as thin cosmetic layers, protective coatings, and/or other coating layers that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide structures  16  from view of the user). 
     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 backplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more metal parts that is welded or otherwise connected between opposing sides of member  16 ). The backplate may form an exterior rear surface of device  10  or may be covered by layers such as thin cosmetic layers, protective coatings, and/or other coatings that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide the backplate from view of the user. 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 extend under active area AA of display  14 , for example. 
     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 portions of housing  12 , conductive traces on a printed circuit board, conductive electrical components in display  14 , etc.). These openings, which may sometimes be referred to as gaps, may be filled with air, plastic, and/or other dielectrics and may be used in forming slot antenna resonating elements for one or more antennas in device  10 , if desired. 
     Conductive housing structures and other conductive structures in device  10  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 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 peripheral 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 of 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 one or more upper antennas and one or more 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. 
     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 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, a high band from 2300 to 2700 MHz, an ultra-high band from 3400 to 3700 MHz or other communications bands between 600 MHz and 4000 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  103  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, a stripline transmission line, or a microstrip transmission line (as examples). A matching network (e.g., an adjustable matching network formed using tunable components  102 ) may include components such as inductors, resistors, and capacitors 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  112  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  100 . 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 information from a proximity sensor (see, e.g., sensors  32  of  FIG. 2 ), wireless performance metric data such as received signal strength information, device orientation information from an orientation sensor, device motion data from an accelerometer or other motion detecting sensor, information about a usage scenario of device  10 , information about whether audio is being played through speaker  26 , information from one or more antenna impedance sensors, and/or other information in determining when antenna(s)  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 component  102  to ensure that antenna structures  40  operate as desired. Adjustments to component  102  may also be made to extend the coverage of antenna structures  40  (e.g., to cover desired communications bands that extend over a range of frequencies larger than antenna structures  40  would cover without tuning). 
     The presence or absence of external objects such as a user&#39;s hand 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  32  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. 
     Antennas  40  may include slot antenna structures, inverted-F antenna structures (e.g., planar and non-planar inverted-F antenna structures), loop antenna structures, combinations of these, or other antenna structures. 
     An illustrative inverted-F antenna structure is shown in  FIG. 4 . As shown in  FIG. 4 , inverted-F antenna structure  40  (sometimes referred to herein as antenna  40  or inverted-F antenna  40 ) may include an inverted-F antenna resonating element such as antenna resonating element  106  and an antenna ground (ground plane) such as antenna ground  104 . Antenna resonating element  106  may have a main resonating element arm such as arm  108 . The length of arm  108  may be selected so that antenna structure  40  resonates at desired operating frequencies. For example, the length of arm  108  (or a branch of arm  108 ) may be a quarter of a wavelength at a desired operating frequency for antenna  40 . Antenna structure  40  may also exhibit resonances at harmonic frequencies. If desired, slot antenna structures or other antenna structures may be incorporated into an inverted-F antenna such as antenna  40  of  FIG. 4  (e.g., to enhance antenna response in one or more communications bands). As an example, a slot antenna structure may be formed between arm  108  or other portions of resonating element  106  and ground  104 . In these scenarios, antenna  40  may include both slot antenna and inverted-F antenna structures and may sometimes be referred to as a hybrid inverted-F and slot antenna. 
     Arm  108  may be separated from ground  104  by a dielectric-filled opening such as dielectric gap  101 . Antenna ground  104  may be formed from housing structures such as a conductive support plate, printed circuit traces, metal portions of electronic components, or other conductive ground structures. Gap  101  may be formed by air, plastic, and/or other dielectric materials. 
     Main resonating element arm  108  may be coupled to ground  104  by return path  110 . Antenna feed  112  may include positive antenna feed terminal  98  and ground antenna feed terminal  100  and may run parallel to return path  110  between arm  108  and ground  104 . If desired, inverted-F antenna structures such as illustrative antenna structure  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.). Arm  108  may have other shapes and may follow any desired path if desired (e.g., paths having curved and/or straight segments). 
     If desired, antenna  40  may include one or more adjustable circuits (e.g., tunable components  102  of  FIG. 3 ) that are coupled to antenna resonating element structures  106  such as arm  108 . As shown in  FIG. 4 , for example, tunable components  102  such as adjustable inductor  114  may be coupled between antenna resonating element arm structures in antenna  40  such as arm  108  and antenna ground  104  (i.e., adjustable inductor  114  may bridge gap  101 ). Adjustable inductor  114  may exhibit an inductance value that is adjusted in response to control signals  116  provided to adjustable inductor  114  from control circuitry  28 . 
     A top interior view of an illustrative portion of device  10  that contains antennas is shown in  FIG. 5 . As shown in  FIG. 5 , device  10  may have peripheral conductive housing structures such as peripheral conductive housing structures  16 . Peripheral conductive housing structures  16  may be divided by dielectric-filled peripheral gaps (e.g., plastic gaps)  18  such as a first gaps  18 - 1  and a second gap  18 - 2 . The resonating element for antenna  40  may include an inverted-F antenna resonating element arm such as arm  108  that is formed from a segment of peripheral conductive housing structures  16  extending between gaps  18 - 1  and  18 - 2 . Air and/or other dielectric may fill slot  101  between arm  108  and ground structures  104 . If desired, opening  101  may be configured to form a slot antenna resonating element structure that contributes to the overall performance of the antenna. Antenna ground  104  may be formed from conductive housing structures, from electrical device components in device  10 , from printed circuit board traces, from strips of conductor such as strips of wire and metal foil, or other conductive structures. In one suitable arrangement ground  104  is formed from conductive portions of housing  12  (e.g., portions of a rear wall of housing  12  and portions of peripheral conductive housing structures  16  that are separated from arm  108  by peripheral gaps  18 ) and conductive portions of display  14  (e.g., conductive portions of a display panel, a conductive plate for supporting the display panel, and/or a conductive frame for supporting the conductive plate and/or the display panel). 
     As shown in  FIG. 5 , ground  104  may have portions that are separated from the segment of peripheral conductive housing structures  16  between gaps  18 - 2  and  18 - 1  by a distance  140 . Slot  101  may have a width  140  in these regions. Other portions of ground plane  104  may be separated from peripheral conductive housing structures  16  by a shorter distance  142 . Slot  101  may have a width  142  in these regions. 
     Positive transmission line conductor  94  and ground transmission line conductor  96  of transmission line  92  may be coupled between transceiver circuitry  90  and antenna feed  112 . Positive antenna feed terminal  98  of feed  112  may be coupled to arm  108 . Ground antenna feed terminal  100  of feed  112  may be coupled to ground  104 . Antenna feed  112  may be coupled across slot  101  at a location along ground plane  104  that is separated from peripheral conductive structures  16  by distance  142 . Distance  142  may, for example, be selected so that a desired distributed capacitance is formed between ground  104  and peripheral conductive housing structures  16 . The distributed capacitance may be selected to ensure that antenna  40  is impedance matched to transmission line  92 , for example. The portion of ground plane  104  that is separated from peripheral conductive housing structures  16  by distance  142  may be interposed between two regions where ground plane  104  is separated from peripheral conductive housing structures  16  by distance  140 , if desired. Transceiver circuitry  90  (e.g., remote wireless transceiver circuitry  38 , local wireless transceiver circuitry  36 , and/or GPS receiver circuitry  42  in  FIG. 2 ) may convey radio-frequency signals 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, a high band from 2300 to 2700 MHz, an ultra-high band from 3400 to 3700 MHz, 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications, and/or a 1575 MHz GPS band using antenna  40  and feed  112 . 
     Ground plane  104  may have any desired shape within device  10 . For example, the lower edge of ground plane  104  may be aligned with gap  18 - 1  in peripheral conductive hosing structures  16  (e.g., the upper or lower edge of gap  18 - 1  may be aligned with the edge of ground plane  104  defining slot  101  adjacent to gap  18 - 1 ). This example is merely illustrative. If desired, as shown in  FIG. 5 , ground  104  may include a vertical slot such as slot  162  adjacent to gap  18 - 1  that extends above the edges of gap  18 - 1  (e.g., along the Y-axis of  FIG. 5 ). Similarly, the lower edge of ground plane  104  may be aligned with the gap  18 - 2  (e.g., the upper or lower edge of gap  18 - 2  may be aligned with the edge of ground plane  104  defining slot  101  adjacent to gap  18 - 2 ) or may extend above the edges of gap  18 - 2 . 
     As shown in  FIG. 5 , vertical slot  162  adjacent to gap  18 - 1  may extend beyond the upper edge (e.g., upper edge  174 ) of gap  18 - 1  (e.g., in the direction of the Y-axis of  FIG. 5 ). Slot  162  may, for example, have two edges that are defined by ground  104  and one edge that is defined by peripheral conductive structures  16 . Slot  162  may have an open end defined by an open end of slot  101  at gap  18 - 1 . Slot  162  may have a width  176  that separates ground  104  from the portion of peripheral conductive structures  16  above gap  18 - 1  (e.g., in the direction of the X-axis of  FIG. 5 ). Because the portion of peripheral conductive structures  16  above gap  18 - 1  is shorted to ground  104  (and thus forms part of the antenna ground for antenna structures  40 ), slot  162  may effectively form an open slot having three sides defined by the antenna ground for antenna structures  40 . Slot  162  may have any desired width (e.g., about 2 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, more than 0.5 mm, more than 1.5 mm, more than 2.5 mm, 1-3 mm, etc.). Slot  162  may have an elongated length  178  (e.g., perpendicular to width  176 ). Slot  162  may have any desired length (e.g., 10-15 mm, more than 5 mm, more than 10 mm, more than 15 mm, more than 30 mm, less than 30 mm, less than 20 mm, less than 15 mm, less than 10 mm, between 5 and 20 mm, etc.). 
     Electronic device  10  may be characterized by longitudinal axis  282 . Length  178  may extend parallel to longitudinal axis  282  (e.g., the Y-axis of  FIG. 5 ). Portions of slot  162  may contribute slot antenna resonances to antenna  40  in one or more frequency bands if desired. For example, the length and width of slot  162  (e.g., the perimeter of slot  162 ) may be selected so that antenna  40  resonates at desired operating frequencies. If desired, the overall length of slots  101  and  162  may be selected so that antenna  40  resonates at desired operating frequencies. 
     If desired, ground plane  104  may include an additional vertical slot  182  adjacent to gap  18 - 2  that extends beyond the upper edge (e.g., upper edge  184 ) of gap  18 - 2  (e.g., in the direction of the Y-axis of  FIG. 5 ). Slot  182  may, for example, have two edges that are defined by ground  104  and one edge that is defined by peripheral conductive structures  16 . Slot  182  may have an open end defined by an open end of slot  101  at gap  18 - 2 . Slot  182  may have a width  186  that separates ground  104  from the portion of peripheral conductive structures  16  above gap  18 - 1  (e.g., in the direction of the X-axis of  FIG. 5 ). Because the portion of peripheral conductive structures  16  above gap  18 - 2  is shorted to ground  104  (and thus forms part of the antenna ground for antenna structures  40 ), slot  182  may effectively form an open slot having three sides defined by the antenna ground for antenna structures  40 . Slot  182  may have any desired width (e.g., about 2 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, more than 0.5 mm, more than 1.5 mm, more than 2.5 mm, 1-3 mm, etc.). Slot  182  may have an elongated length  188  (e.g., perpendicular to width  186 ). Slot  182  may have any desired length (e.g., 10-15 mm, more than 5 mm, more than 10 mm, more than 15 mm, more than 30 mm, less than 30 mm, less than 20 mm, less than 15 mm, less than 10 mm, between 5 and 20 mm, etc.). 
     Length  188  may extend parallel to longitudinal axis  282  (e.g., the Y-axis of  FIG. 5 ). Portions of slot  182  may contribute slot antenna resonances to antenna  40  in one or more frequency bands if desired. For example, the length and width of slot  182  may be selected so that antenna  40  resonates at desired operating frequencies. If desired, the overall length of slots  101  and  182  may be selected so that antenna  40  resonates at desired operating frequencies. If desired, the overall length of slots  101 ,  162 , and  182  may be selected so that antenna  40  resonates at desired operating frequencies. 
     A return path such as path  110  of  FIG. 4  may be formed by a fixed conductive path bridging slot  101  and/or one or more adjustable components such as adjustable components  202  and/or  208  as shown in  FIG. 5  (e.g., adjustable components such as tuning components  102  of  FIG. 3 ). Adjustable components  202  and  208  may sometimes be referred to herein as tuning components, tunable components, tuning circuits, tunable circuits, adjustable components, or adjustable tuning components. 
     Adjustable component  202  may bridge slot  101  at a first location along slot  101  (e.g., component  202  may be coupled between terminal  206  on ground plane  104  and terminal  204  on peripheral conductive structures  16 ). Adjustable component  208  may bridge slot  101  at a second location along slot  101  (e.g., component  208  may be coupled between terminal  212  on ground plane  104  and terminal  210  on peripheral conductive structures  16 ). Ground antenna feed terminal  100  may be interposed between terminal  206  and terminal  212  on ground plane  104 . Positive antenna feed terminal  98  may be interposed between terminal  204  and terminal  210  on peripheral conductive structures  16 . Terminal  212  may be closer to ground antenna feed terminal  100  than terminal  206 . Terminal  210  may be closer to positive antenna feed terminal  98  than terminal  204 . Terminals  206  and  212  may be formed on portions of ground plane  104  that are separated from peripheral conductive housing structures  16  by distance  140 . 
     Components  202  and  208  may include switches coupled to fixed components such as inductors for providing adjustable amounts of inductance or an open circuit between ground  104  and peripheral conductive structures  16 . Components  202  and  208  may also include fixed components that are not coupled to switches or a combination of components that are coupled to switches and components that are not coupled to switches. These examples are merely illustrative and, in general, components  202  and  208  may include other components such as adjustable return path switches, switches coupled to capacitors, or any other desired components. 
     Components  202  and  208  may be adjusted based on the operating environment of the electronic device. For example, electronic device  10  may have at least three modes of operation that correspond to different tuning settings of components  202  and  208 . A desired mode of operation may be selected for use based on the presence or absence of external objects such as a user&#39;s hand or other body part in the vicinity of antenna  40  and/or based on the frequency bands to be used for communications. Components  202  and  208  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 ). 
     Components  202  and  208  may be formed between peripheral conductive housing structures  16  and ground plane  104  using any desired structures. For example, components  202  and  208  may be formed on a printed circuit such as a flexible printed circuit board that is coupled between peripheral conductive housing structures  16  and ground plane  104 . Antenna ground  104  may include a conductive layer of housing  12  (e.g., a conductive backplate for device  10 ). If desired, additional conductive layers may be used to form portions of antenna ground  104 . For example, ground plane  104  may include conductive portions of display  14  of  FIG. 1  (e.g., conductive portions of a display panel, a conductive plate for supporting the display panel, and/or a conductive frame for supporting the conductive plate and/or the display panel). Ground terminals  206 ,  100 , and  212  may be coupled to the conductive layer of housing  12 , the conductive portion of display  14 , or other conductive structures that form antenna ground  104 . If desired, conductive structures such as vertical conductive interconnect structures (e.g., a bracket, clip, spring, pin, screw, solder, weld, conductive adhesive, wire, metal strip, etc.) may be used to short the conductive layer of housing  12  to the conductive portion of display  14  that forms a part of antenna ground  104  (e.g., at locations  206 ,  100 , and/or  212 ). Electrically connecting different components of the device ground (e.g., ground  104  in  FIG. 5 ) with vertical conductive interconnect structures may ensure that the conductive structures that are located the closest to resonating element arm  108  are held at a ground potential and form a part of antenna ground  104 . This may serve to optimize the antenna efficiency of antenna  40 , for example. 
     Control circuitry such as storage and processing circuitry  28  of  FIG. 2  may control tuning components  202  and  208  and/or transceiver to place device  10  in one of at least first, second, and third modes of operation. In the first mode of operation, antenna  40  may be placed in a first tuning mode or state in which tuning components  202  and  208  are controlled using a first configuration or setting. In the second mode of operation, antenna  40  may be placed in a second tuning mode or state in which tuning components  202  and  208  are controlled using a second configuration or setting. In the third mode of operation, antenna  40  may be placed in a third tuning mode or state in which tuning components  202  and  208  are controlled using a third configuration or setting. 
     Antenna  40  may be configured to handle different frequency bands in each tuning mode. For example, in the first tuning mode, antenna  40  may be configured to perform communications in a low band, midband, and high band. In the second tuning mode of antenna  40  may also be configured to perform communications in the low band, midband, and high band. However, the first and second tuning modes may compensate for antenna loading by an external device such as a user&#39;s hand in different ways. For example, in the first tuning mode, antenna  40  may be configured to operate with a relatively high antenna efficiency if device  10  is being held by a user&#39;s right hand and a relatively low antenna efficiency if device  10  is being held by a user&#39;s left hand, whereas in the second tuning mode antenna  40  may be configured to operate with a relatively high antenna efficiency if device  10  is being held by a user&#39;s left hand and a relatively low antenna efficiency if device  10  is being held by a user&#39;s right hand. In other words, in the first and second tuning modes, antenna  40  may perform wireless communications in the low band, midband, and high band, but may be sensitive to certain operating conditions such as which hand a user is using to hold device  10 . 
     In general, antenna  40  may be more susceptible to changing loading conditions and detuning when operating in the low band than when operating in the midband or high band. In the third tuning mode, antenna  40  may be configured to operate with a relatively high efficiency regardless of which hand a user is using to hold device  10  (e.g., antenna  40  may be resilient or reversible to the handedness of the user). However, when placed in the third tuning mode, antenna  40  may only cover a subset of the frequency bands that antenna  40  is capable of covering in the first and second tuning modes. For example, in the third tuning mode antenna  40  may cover the midband and high band without covering the low band. 
       FIGS. 6-8  are top views of electronic device  10  showing how antenna  40  may be tuned in each of the first, second, and third operating modes. In particular,  FIG. 6  is a diagram showing how antenna  40  may be controlled when placed in the first tuning mode,  FIG. 7  is a diagram showing how antenna  40  may be controlled when placed in the second tuning mode, and  FIG. 8  is a diagram showing how antenna  40  may be controlled when placed in the third tuning mode. 
     As shown in  FIG. 6 , component  202  may include inductor circuitry such as a first inductor  214  coupled in parallel with a second inductor  218  between terminals  204  and  206 . Inductor  214  may be coupled in series with switch  216  between terminals  204  and  206 , whereas inductor  218  may be coupled in series with switch  220  between terminals  204  and  206 . Switches  216  and  220  may selectively connect or disconnect the respective inductor across slot  101 . For example, switch  216  may have a first state in which switch  216  is closed and inductor  214  is connected between terminal  204  and terminal  206 . Switch  216  may have a second state in which switch  216  is open and inductor  214  is not connected between terminal  204  and terminal  206 . Similarly, switch  220  may have a first state in which switch  220  is closed and inductor  218  is connected between terminal  204  and terminal  206 . Switch  220  may have a second state in which switch  220  is open and inductor  218  is not connected between terminal  204  and terminal  206 . Inductors  214  and  218  may each exhibit any desired inductance values (e.g., 1-4 nH, 1-10 nH, greater than 1 nH, greater than 2 nH, less than 10 nH, less than 6 nH, less than 4 nH, etc.). 
     Component  208  may include two inductors such as a first inductor  222  coupled in parallel with a second inductor  226  between terminals  210  and  212 . Inductor  222  may be coupled in series with switch  224  between terminals  210  and  212 , whereas inductor  226  may be coupled in series with switch  228  between terminals  210  and  212 . Switches  224  and  228  may selectively connect or disconnect the respective inductor across slot  101 . For example, switch  224  may have a first state in which switch  224  is closed and inductor  222  is connected between terminal  210  and terminal  212 . Switch  224  may have a second state in which switch  224  is open and inductor  222  is not connected between terminal  210  and terminal  212 . Similarly, switch  228  may have a first state in which switch  228  is closed and inductor  226  is connected between terminal  210  and terminal  212 . Switch  228  may have a second state in which switch  228  is open and inductor  226  is not connected between terminal  210  and terminal  212 . Inductors  222  and  226  may each exhibit any desired inductance values (e.g., 1-4 nH, 1-10 nH, greater than 1 nH, greater than 2 nH, less than 10 nH, less than 6 nH, less than 4 nH, etc.). 
     When antenna structures  40  are operated in the first tuning mode (as shown in  FIG. 6 ), component  202  may form an open circuit between terminal  204  on peripheral conductive housing structure  16  and terminal  206  on ground plane  104  (e.g., switches  216  and  220  may both be turned off or open). Switch  224  of component  208  may be closed to connect inductor  222  between terminals  210  and  212  whereas switch  228  is open (disconnecting inductor  226  between terminals  210  and  212 ). This example is merely illustrative and, if desired, switch  228  may be closed and switch  224  may be open or both switches  224  and  228  may be closed in the first tuning mode. If desired, switches  224  and/or  228  may be toggled to tune antenna  40  while antenna  40  is placed in the first tuning mode. In other words, in the first tuning mode, all of the adjustable inductors of component  202  may be disconnected across slot  101  while component  208  performs antenna tuning by coupling one or both of inductors  222  and  226  across slot  101 . 
     The example of  FIG. 6  in which two inductors are included in component  202  and component  208  is merely illustrative. If desired, components  202  and  208  may include one, two, three, four, or more than four inductors. Components  202  and  208  may have the same number of inductors or a different number of inductors. Components  202  and/or  208  may include capacitive components in addition to or instead of inductors if desired. The example of  FIG. 6  in which the switching circuitry in components  202  and  208  are single-pole single-throw (SPST) switches is merely illustrative. In general, components  202  and  208  may include any desired switching circuitry (e.g., single-pole double throw (SP2T) switches, etc.). 
     In the first tuning mode, the resonance of antenna  40  in low band LB (e.g., from 700 MHz to 960 MHz or another suitable frequency range) may be associated with the distance along peripheral conductive structures  16  between feed  112  and gap  18 - 1 , for example.  FIG. 6  is a view from the front of device  10 , so gap  18 - 1  of  FIG. 6  lies on the left edge of device  10  when device  10  is viewed from the front (e.g., the side of device  10  on which display  14  is formed) and lies on the right edge of device  10  when device  10  is viewed from behind. 
     Tunable components such as component  208  or other tunable components (not shown) may be used to tune the response of antenna  40  in low band LB in the first tuning mode, if desired. The resonance of antenna  40  in midband MB (e.g., from approximately 1710 MHz to 2170 MHz) may be associated with the distance along peripheral conductive structures  16  between feed  112  and gap  18 - 2 , for example. Antenna performance in midband MB may also be supported by slot  182  in ground plane  104 . Tunable components such as component  208  may be used to tune the response of antenna  40  in midband MB in the first tuning mode. Antenna performance in high band HB (e.g., 2300 MHz to 2700 MHz) may be supported by slot  162  in ground plane  104  and/or by a harmonic mode of a resonance supported by antenna resonating element arm  108 . Tunable components such as component  208  may be used to tune the response of antenna  40  in high band HB in the first tuning mode if desired. 
     When operated in the first tuning mode, antenna  40  may be particularly susceptible to loading and detuning in low band LB when device  10  is being held by a user&#39;s left hand (e.g., because the user&#39;s left palm, which typically loads antenna  40  more than the user&#39;s fingers, may be in close proximity with the low band portion of resonating element  108  adjacent to gap  18 - 1  when held in the user&#39;s left hand). However, antenna  40  may be relatively immune to loading and detuning in low band LB when device  10  is being held by a user&#39;s right hand in the first tuning mode (e.g., because the user&#39;s right palm is located adjacent to gap  18 - 2  and relatively far from the low band portion of resonating element  108 ). The first tuning mode may therefore sometimes be referred to herein as the right hand tuning mode of antenna  40  (e.g., device  10  may be placed in a so-called right hand operating mode or state when antenna  40  is placed in the right hand tuning mode). The loading of antenna  40  in low band LB by the user&#39;s left hand may therefore cause antenna  40  to exhibit deteriorated antenna efficiency in low band LB when antenna  40  is placed in the first tuning mode. In order to mitigate such antenna loading by the user&#39;s left hand, antenna  40  may be placed in the second or third tuning modes. 
     As shown in  FIG. 7 , when antenna structures  40  are operated in the second tuning mode, component  208  may form an open circuit between terminal  210  on peripheral conductive housing structure  16  and terminal  212  on ground  104  (e.g., switches  224  and  228  may both be open or turned off). Switch  220  of component  202  may be closed to connect inductor  218  between terminals  204  and  206  whereas switch  216  may be open (disconnecting inductor  214  between terminals  204  and  206 ). This example is merely illustrative, and, if desired, switch  216  may be closed and switch  220  may be open or both switches  216  and  220  may be closed in the second tuning mode. If desired, switches  216  and/or  220  may be toggled to tune antenna  40  while antenna  40  is placed within the second tuning mode. In other words, in the second tuning mode, all of the adjustable inductors of component  208  may be disconnected across slot  101  while component  202  performs antenna tuning by coupling one or both of inductors  214  and  218  across slot  101 . 
     In the second tuning mode, the resonance of antenna  40  in low band LB (e.g., from 700 MHz to 960 MHz or another suitable frequency range) may be associated with the distance along peripheral conductive structures  16  between the position of component  202  (i.e., terminal  204 ) of  FIG. 7  and gap  18 - 2 , for example.  FIG. 7  is a view from the front of device  10 , so gap  18 - 2  of  FIG. 7  lies on the right edge of device  10  when device  10  is viewed from the front (e.g., the side of device  10  on which display  14  is formed) and lies on the left edge of device  10  when device  10  is viewed from behind. 
     Tunable components such as component  202  or other tunable components (not shown) may be used to tune the response of antenna  40  in low band LB in the second tuning mode, if desired. The resonance of antenna  40  in midband MB (e.g., from approximately 1710 MHz to 2170 MHz) may be associated with the distance along peripheral conductive structures  16  between the position of component  202  (i.e., terminal  204 ) and gap  18 - 1 , for example. Antenna performance in midband MB may also be supported by slot  182  in ground plane  104 . Tunable components such as component  202  may be used to tune the response of antenna  40  in midband MB in the second tuning mode. The resonance of antenna  40  at high band HB (e.g., 2300 MHz to 2700 MHz) may be associated with the distance along peripheral conductive structures  16  between the position of component  202  (i.e., terminal  204 ) and gap  18 - 1 , for example. Antenna performance in high band HB may also be supported by slot  162  in ground plane  104  and/or by a harmonic mode of a resonance supported by antenna resonating element arm  108 . Tunable components such as component  202  may be used to tune the response of antenna  40  in high band HB in the second tuning mode if desired. 
     When operated in the second tuning mode, antenna  40  may be particularly susceptible to loading and detuning in low band LB when device  10  is being held by a user&#39;s right hand (e.g., because the user&#39;s right palm, which typically loads antenna  40  more than the user&#39;s fingers, may be in close proximity with the low band portion of resonating element  108  adjacent to gap  18 - 2  when held in the user&#39;s right hand). However, antenna  40  may be relatively immune to loading and detuning in low band LB when device  10  is being held by a user&#39;s left hand in the second tuning mode (e.g., because the user&#39;s left palm is located adjacent to gap  18 - 1  and relatively far from the low band portion of resonating element  108 ). The second tuning mode may therefore sometimes be referred to herein as the left hand tuning mode of antenna  40  (e.g., device  10  may be placed in a so-called left hand operating mode or state when antenna  40  is placed in the left hand tuning mode). The loading of antenna  40  in low band LB by the user&#39;s right hand may therefore cause antenna  40  to exhibit deteriorated antenna efficiency in low band LB when antenna  40  is placed in the second tuning mode. In order to mitigate such antenna loading by the user&#39;s right hand, antenna  40  may be placed in the first or third tuning modes. 
     As shown in  FIG. 8 , when antenna  40  is in the third tuning mode, at least one switch in both component  202  and component  208  is closed. For example, switch  224  may be closed to connect inductor  222  between terminals  210  and  212  and switch  228  may be open to disconnect inductor  226  between terminals  210  and  212 . In other suitable arrangements, however, switch  228  may be closed and switch  224  may be open or both switches  224  and  228  may be closed. Similarly, switch  220  may be open to disconnect inductor  218  between terminals  204  and  206  and switch  216  may be closed to connect inductor  214  between terminals  204  and  206 . In other suitable arrangements, however, switch  220  may be closed and switch  216  may be open or both switches  216  and  220  may be closed. If desired, switches  216 ,  220 ,  224  and  228  may be toggled to tune antenna  40  while antenna  40  is placed in the third tuning mode. In other words, in the third tuning mode, components  202  and  208  perform antenna tuning by coupling one or both of inductors  214  and  218  and one or both of inductors  222  and  226  across slot  101 . 
     In the third tuning mode, the resonance of antenna  40  in midband MB and high band HB may be associated with a conductive loop path that includes portions of peripheral conductive structures  16  (e.g., the portion of peripheral conductive structures  16  extending between terminal  204  of component  202  and terminal  210  of component  208 ), component  202 , ground plane  104 , and component  208 . 
     When operated in the third tuning mode, antenna  40  may be substantially immune to changes in loading dependent on how the user is holding device  10  (e.g., antenna  40  may exhibit satisfactory antenna efficiency regardless of whether the user is holding device  10  with their left or right hand). However, at the same time, antenna  40  may not be able to support a resonance at relatively low frequencies such as frequencies in low band LB when placed in the third tuning mode. In addition, antenna  40  may exhibit improved midband and/or high band efficiency relative to the first and second tuning modes. However, if it is desired to communicate in low band LB (e.g., based on an assignment to device  10  by external communications equipment such as a wireless base station or access point, based on a control algorithm performed by storage and processing circuitry  28 , etc.), antenna  40  may be placed in the first or second tuning modes. Storage and processing circuitry  28  may adjust antenna  40  between the first, second and third tuning modes to ensure satisfactory performance in any desired bands over time regardless of environmental conditions. 
       FIG. 9  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  FIGS. 5-8 . As shown in  FIG. 9 , antenna  40  may exhibit resonances in a midband MB and high band HB (coverage in low band LB is not shown for the sake of clarity). As shown in  FIG. 9 , antenna  40  may have an antenna efficiency characterized by curve  232  in scenarios where ground plane  104  is separated from peripheral conductive structures  16  by distance  140  across the length of slot  101 . Antenna  40  may have an antenna efficiency characterized by curve  234  in examples where ground plane  104  includes a distributed capacitance formed by the portion of ground plane  104  that is separated from peripheral conductive structures  16  by distance  142  (as shown in  FIGS. 5-8 ). As shown in  FIG. 9 , the distributed capacitance formed by the extended portion of the ground plane may improve impedance matching for antenna  40  and thus antenna efficiency relative to scenarios in which the distributed capacitance is absent (i.e., curve  234  is higher than curve  232 ). 
     Curve  234  may characterize the performance of antenna  40  when placed in the first and second tuning modes (as shown in  FIGS. 6 and 7 ). Curve  236  may characterize the performance of antenna  40  when placed in the third tuning mode (as shown in  FIG. 8 ). When placed in the third tuning mode, antenna  40  may exhibit improved efficiency in midband MB and high band HB relative to the first and second tuning modes (as shown by curve  234 ). This increase in antenna efficiency may, for example, be a result of the increase in operating volume available for covering the midband and/or high band in the third antenna tuning mode (e.g., across the conductive loop path shown in  FIG. 8 ) relative to the operating volume available for covering the midband and/or high band in the first and second antenna tuning modes. The frequency response of antenna  40  in the first, second, and third tuning modes may be further tweaked by adjusting components  202  and  208  (e.g., to change the inductance coupled between resonating element arm  108  and ground  104 ). However, when operated in the third tuning mode, antenna  40  may not exhibit satisfactory antenna efficiency in low band LB (e.g., antenna  40  may cover low band LB in the first and second tuning modes but not in the third tuning mode). 
     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. 10  is a flow chart of illustrative steps involved in operating device  10  to ensure satisfactory performance for antenna  40  in all desired frequency bands of interest. 
     At step  242  of  FIG. 10 , 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 a connector port or that detect the presence or absence of data transmission through a connector port, 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  28  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  244 , control circuitry  28  may adjust the configuration of antenna  40  based on the current operating environment of device  10  (e.g., based on data or information gathered while processing step  242 ). For example, control circuitry  28  may process the data gathered while processing step  242  to determine whether device  10  is being held by the user&#39;s right hand, whether device  10  is being held by the user&#39;s left hand, or whether device  10  is in some other operating environment (e.g., a free space environment). Control circuitry  28  may determine desired communication bands for antenna  40 . As previously discussed, antenna  40  may only be used for midband MB and high band HB communications when the antenna is in the third mode (as shown in  FIG. 8 ). Therefore, in situations where low band LB communication is required of antenna  40 , control circuitry  28  may place antenna  40  in the first or second tuning modes. However, if low band communication is not required, control circuitry  28  may place antenna  40  in the third tuning mode (e.g., to optimize antenna efficiency in midband MB and high band HB without susceptibility to the handedness of the user). 
     If control circuitry  28  determines that device  10  is being held by the user&#39;s right hand and low band communication is required, control circuitry  28  may place antenna  40  in the first tuning mode (sometimes referred to as the right hand mode). Control circuitry  28  may place antenna  40  in the first mode by placing tuning components  202  and  208  in a first mode tuning state where all inductors in component  202  are disconnected, as an example. If control circuitry  28  determines that device  10  is being held by the user&#39;s left hand and low band communication is required, control circuitry  28  may place antenna  40  in the second mode (sometimes referred to as the left hand mode). Control circuitry  28  may place antenna  40  in the second mode by placing tuning components  202  and  208  in a second tuning state where all inductors in component  208  are disconnected, as an example. If control circuitry  28  determines that low band communications are not required, control circuitry  28  may place antenna  40  in the third mode (sometimes referred to as the reversible mode). Control circuitry  28  may place antenna  40  in the third mode by placing tuning components  202  and  208  in a third tuning state where both components  202  and  208  are used, as an example. 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  246 , antenna  40  may be used to transmit and receive wireless data in using the currently activated antenna feed and setting for components  202  and  208 . This process may be performed continuously, as indicated by line  248 . 
     A state diagram showing illustrative operating modes for antenna  40  is shown in  FIG. 11 . As shown in  FIG. 11 , antenna  40  may be operable in a left hand mode  250  (e.g., the second mode depicted in  FIG. 7 ), a right hand mode  252  (e.g., the first mode depicted in  FIG. 6 ), and a reversible mode  254  (e.g., the third mode depicted in  FIG. 8 ). 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  242  of  FIG. 10 ) and may adjust tunable components  202  and  208  of  FIG. 5  to place antenna  40  in the corresponding operating mode. 
     If low band communications are not required, control circuitry  28  may place antenna in the reversible mode  254  (which is resilient to different loading conditions). If low band communications are required, control circuitry  28  may place antenna  40  in mode  250  or mode  252 . If it is determined that device  10  is being held in the left hand of a user and low band coverage is required, control circuitry  28  may adjust the circuitry of antenna  40  to place the antenna in left hand mode  250 . If it is determined that device  10  is being held in the right hand of a user and low band coverage is required, control circuitry  28  may adjust the circuitry of antenna  40  to place the antenna in right hand mode  252 . Control circuitry  28  may disconnect component  202  and use component  208  for tuning in left hand mode  250 , may disconnect component  208  and use component  202  for tuning in right hand mode  252 , and may use both components  202  and  208  for tuning in reversible mode  254 . 
     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: 20170911
Publication Date: 20190528
Grant Date: 20190528
Priority Date: 20170911
Inventors: EDWARDS, JENNIFER M.
ZHOU, YIJUN
WANG, Yiren
XU, HAO
TSAI, MING-JU
Lee, Victor C.
HAN, LIANG
MOW, MATTHEW A.
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H03J2200/01", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03J7/186", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03J2200/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03J1/0083", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03J5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03J1/0083", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03J7/186", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03J5/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03J2200/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03J2200/01", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03J2200/06", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 65632287