PATENT DOCUMENT

Publication Number: US-10381715-B2
Application Number: US-201715602972-A
Country: US
Kind Code: B2

Title: Electronic device antennas having multi-band tuning capabilities

Abstract:
An electronic device may include an antenna having a resonating element, an antenna ground, and a feed. First and second tunable components may be coupled to the resonating element. Adjustable matching circuitry may be coupled to the feed. Control circuitry may use the first tunable component to tune a midband antenna resonance when sensor circuitry identifies that the device is being held in a right hand and may use the second tunable component to tune the midband resonance when the sensor circuitry identifies that the device is being held in a left hand. For tuning a low band resonance, the control circuitry may place the antenna in different tuning states by sequentially adjusting a selected one of the matching circuitry and the tunable components, potentially reverting to a previous tuning state at each step in the sequence. This may ensure that antenna efficiency is satisfactory regardless of antenna loading conditions.

Claims:
What is claimed is: 
     
       1. An electronic device configured to be operated in a first orientation while held in a right hand of a user and in a second orientation while held in a left hand of the user, the electronic device comprising:
 orientation sensor circuitry configured to generate orientation data that identifies when the electronic device is in a given one of the first and second orientations; 
 an antenna having a resonating element arm, an antenna ground, an antenna feed having a first feed terminal coupled to the resonating element arm and a second feed terminal coupled to the antenna ground, and first and second tunable components coupled to the resonating element arm on opposing sides of the first feed terminal, wherein the antenna resonating element arm and the antenna ground are configured to exhibit a first resonance in a first communications band and a second resonance in a second communications band that is higher in frequency than the first communications band; and 
 control circuitry, wherein the control circuitry is configured to, based on the orientation data, place the antenna in a first non-free space mode of antenna operation in which the first tunable component tunes the second resonance and in a second non-free space mode of antenna operation in which the second tunable component tunes the second resonance, the antenna feed being configured to convey radio-frequency signals for the antenna in both the first and second non-free space modes of antenna operation. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the first tunable component comprises first and second switchable inductors coupled between the resonating element arm and the antenna ground. 
     
     
       3. The electronic device defined in  claim 2 , wherein the second tunable component comprises third and fourth switchable inductors coupled between the resonating element arm and the antenna ground. 
     
     
       4. The electronic device defined in  claim 3 , wherein the antenna further comprises a fourth tunable component coupled between the resonating element arm and the antenna ground, the fourth tunable component is coupled to the resonating element arm at a location between the first tunable component and the first feed terminal, and the control circuitry is configured to adjust the fourth tunable component to tune a selected one of the first resonance and the second resonance. 
     
     
       5. The electronic device defined in  claim 4 , wherein the fourth tunable component comprises:
 four additional switchable inductors coupled between the resonating element arm and the antenna ground. 
 
     
     
       6. The electronic device defined in  claim 3 , wherein the control circuitry is configured to place the antenna in the first non-free space mode of antenna operation in response to determining that the orientation sensor data identifies that the electronic device is in the first orientation and the control circuitry is configured to place the antenna in the second non-free space mode of antenna operation in response to determining that the orientation sensor data identifies that the electronic device is in the second orientation. 
     
     
       7. The electronic device defined in  claim 6 , wherein the control circuitry is configured to control the first tunable component to tune the second resonance in the first non-free space mode of antenna operation by selectively coupling a given one of the first and second switchable inductors between the resonating element arm and the antenna ground. 
     
     
       8. The electronic device defined in  claim 7 , wherein the control circuitry is configured to control the second tunable component to tune the second resonance in the second non-free space mode of antenna operation by selectively coupling a given one of the third and fourth switchable inductors between the resonating element arm and the antenna ground. 
     
     
       9. The electronic device defined in  claim 8 , further comprising:
 a metal electronic device housing, wherein the resonating element arm is separated from the antenna ground by a slot in the metal electronic device housing and the resonating element arm and the antenna ground are formed from portions of the metal electronic device housing. 
 
     
     
       10. The electronic device antenna defined in  claim 1  further comprising:
 radio-frequency transceiver circuitry; and 
 a coupler interposed between the radio-frequency transceiver circuitry and the antenna feed, wherein the control circuitry is configured to gather antenna impedance information associated with the antenna using signals received by the transceiver circuitry over the coupler, and wherein the control circuitry is configured to place the antenna in a selected one of the first and second non-free space modes of antenna operation based on the orientation data and the gathered antenna impedance information. 
 
     
     
       11. Apparatus, comprising:
 radio-frequency transceiver circuitry; 
 an antenna operable in a plurality of different tuning states and having an antenna resonating element, an antenna ground, an antenna feed, a tunable component coupled to the antenna resonating element, and an adjustable impedance matching circuit coupled between the antenna feed and the antenna resonating element; 
 control circuitry coupled to the antenna; and 
 sensor circuitry coupled to the control circuitry, wherein the control circuitry is configured to:
 place the antenna in a first tuning state of the plurality of tuning states by adjusting the adjustable impedance matching circuit; 
 adjust the antenna from the first tuning state to a second tuning state of the plurality of tuning states by adjusting the tunable component; and 
 gather sensor data using the sensor circuitry while the antenna is placed in each of the first and second tuning states. 
 
 
     
     
       12. The apparatus defined in  claim 11 , wherein the control circuitry is further configured to, based on the sensor data, adjust the antenna from the second tuning state back to the first tuning state by adjusting the tunable component prior to adjusting the antenna to any other tuning state of the plurality of tuning states. 
     
     
       13. The apparatus defined in  claim 11 , wherein the control circuitry is further configured to, based on the sensor data, adjust the antenna from the second tuning state to a third tuning state of the plurality of tuning states by adjusting the adjustable impedance matching circuit. 
     
     
       14. The apparatus defined in  claim 13 , wherein the tunable component comprises a plurality of inductors and switching circuitry and the control circuitry is configured to adjust the tunable component by controlling the switching circuitry to couple a selected one of the plurality of inductors between the antenna resonating element and the antenna ground. 
     
     
       15. The apparatus defined in  claim 14 , wherein the control circuitry is configured to adjust the adjustable impedance matching circuit by controlling the adjustable impedance matching circuit to exhibit a selected one of a first impedance and a second impedance that is different from the first impedance. 
     
     
       16. The apparatus defined in  claim 15 , wherein a first inductor of the plurality of inductors is coupled between the antenna resonating element and the antenna ground and the impedance matching circuit exhibits the first impedance when the antenna is placed in the first tuning state, a second inductor of the plurality of inductors is coupled between the antenna resonating element and the antenna ground and the impedance matching circuit exhibits the first impedance when the antenna is placed in the second antenna tuning state, and the second inductor is coupled between the antenna resonating element and the antenna ground and the impedance matching circuit exhibits the second impedance when the antenna is placed in the third antenna tuning state. 
     
     
       17. The apparatus defined in  claim 11 , wherein the sensor circuitry comprises an impedance sensor and the sensor data comprises S11 scattering parameter values gathered while the antenna is placed in the first and second tuning states. 
     
     
       18. An electronic device, comprising:
 radio-frequency transceiver circuitry; 
 an antenna operable in a set of different tuning states and having an antenna resonating element, an antenna ground, an antenna feed, a tunable component coupled to the antenna resonating element, and an adjustable impedance matching circuit coupled between the antenna feed and the antenna resonating element; 
 sensor circuitry configured to generate sensor data; and 
 control circuitry, wherein the control circuitry is configured place the antenna in each of the tuning states in the set of tuning states by:
 tuning the antenna from a first tuning state in the set of tuning states to a second tuning state in the set of tuning states by adjusting a selected one of the adjustable impedance matching circuit and the tunable component; and 
 based on the sensor data, adjusting the antenna to return to the first tuning state from the second tuning state prior to tuning the antenna to a third tuning state in the set of tuning states. 
 
 
     
     
       19. The electronic device defined in  claim 18 , wherein the sensor circuitry comprises an impedance sensor, the sensor data comprises S11 scattering parameter values, and the control circuitry is further configured to:
 gather a first S11 scattering parameter value using the impedance sensor while the antenna is tuned to the first tuning state and a second S11 scattering parameter value using the impedance sensor while the antenna is tuned to the second tuning state; 
 compare a magnitude of the first S11 scattering parameter value to a magnitude of the second S11 scattering parameter value; and 
 in response to determining that the magnitude of the second S11 scattering parameter value is greater than the magnitude of the first S11 scattering parameter value, adjust the antenna to return to the first tuning state from the second tuning state prior to tuning the antenna to the third tuning state. 
 
     
     
       20. The electronic device defined in  claim 19 , wherein the control circuitry is further configured to:
 gather a third S11 scattering parameter value using the impedance sensor while the antenna is tuned to the first tuning state after returning to the first tuning state from the second tuning state; 
 compare an offset between the third S11 scattering parameter value and the first S11 scattering parameter value to a threshold value; and 
 in response to determining that the offset exceeds the threshold value, reset the antenna to an initial tuning state in the set of tuning states.

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 have wireless circuitry with a radio-frequency transceiver and antennas. An antenna may include an antenna resonating element arm, an antenna ground, and an antenna feed. 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. First and second tunable components may be coupled between the antenna ground and the antenna resonating element arm across the slot and on opposing sides of the feed. An adjustable impedance matching circuit may be coupled between the radio-frequency transceiver and the antenna feed. The electronic device may include sensor circuitry such as an orientation sensor and an impedance sensor that generate sensor data. The antenna may exhibit resonances in a low band, midband, high band, ultra-high band, and/or other frequency bands. 
     The control circuitry may place the antenna in a first non-free space mode of antenna operation in which the first tunable component tunes the midband resonance and in a second non-free space mode of antenna operation in which the second tunable component tunes the midband resonance. The control circuitry may place the antenna in the first non-free space mode when the orientation sensor detects that the device is being held in a user&#39;s right hand and may place the antenna in the second non-free space mode when the orientation sensor detects that the device is being held in the user&#39;s left hand, for example. 
     When tuning the low band resonance of the antenna, the control circuitry may place the antenna in a selected tuning state of a set of different tuning states. For example, the control circuitry may place the antenna in a first tuning state by adjusting the adjustable impedance matching circuit, may adjust the antenna from the first tuning state to a second tuning state by adjusting the tunable components, and may gather sensor data using the sensor circuitry while the antenna is placed in each of the first and second tuning states. The control circuitry may adjust the antenna from the second tuning state back to the first tuning state by reverting the setting of the tunable components prior to adjusting the antenna to any other tuning state in the set of tuning states. Alternatively, the control circuitry may adjust the antenna from the second tuning state to a third tuning state by further adjusting the impedance matching circuit. The control circuitry may determine which adjustment to make based on the sensor data. This process may be repeated across each of the different tuning states by sequentially adjusting only one of the matching circuitry and the tunable components at a given time, potentially reverting to a previous tuning state at each step in the sequence, until an optimal setting is identified by the sensor data. This may ensure that antenna efficiency is satisfactory regardless of the frequency of operation and regardless of the environmental loading conditions of the antenna. 
    
    
     
       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 of the present invention. 
         FIG. 6  is diagram of illustrative antenna structures having grip-independent multi-band tuning capabilities 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 performing mid band and ultra-high band antenna tuning using an antenna of the type shown in  FIG. 6  in accordance with an embodiment. 
         FIG. 9  is a state diagram showing illustrative mid band and ultra-high band antenna operating modes for an electronic device in accordance with an embodiment. 
         FIG. 10  is a flow chart of illustrative steps of illustrative steps that may be involved in performing low band antenna tuning using an antenna of the type shown in  FIG. 6  in accordance with an embodiment. 
         FIG. 11  is a state diagram showing illustrative low band antenna operating modes for an electronic device in accordance with an embodiment. 
         FIG. 12  is a Smith chart showing illustrative impedances that may be used in performing offset comparison operations for low band antenna tuning 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 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 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. 
     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 or other communications bands between 700 MHz and 3700 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 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 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, 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 component  102  to ensure that antenna  40  operates as desired. Adjustments to component  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, if 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 . If desired, tuning components  102  may be adjusted to interpose a selected one of a number of different inductors in path  110 . Additional return paths  110  may be coupled between arm  108  and ground  104  if desired. 
     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 (e.g., tunable components  102  of  FIG. 3 ) 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 . As shown in  FIG. 6 , antenna  40  (e.g., a hybrid slot-inverted-F antenna) may be fed by transceiver circuitry  90  that is coupled to antenna feed  112  over radio-frequency transmission line  92 . One or more additional feeds may be coupled to antenna  40 , if desired. 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 . 
     Feed  112  may be coupled across slot  114 . For example, positive antenna feed terminal  98  may be coupled to peripheral conductive structures  16  whereas ground antenna feed terminal  100  is formed on ground plane  104 . Positive antenna feed terminal  98  may be coupled to transceiver  90  over signal conductor  94  of radio-frequency transmission line  92 . Ground antenna feed terminal  100  may be coupled to transceiver  90  over ground conductor  96  of radio-frequency transmission line  92 . 
     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  as shown in  FIG. 1 ). The length of antenna resonating element arm  108  (e.g., the portion of peripheral conductive housing structures  16  extending between gaps  18 - 1  and  18 - 2 ) 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  114  or an adjustable component such as adjustable components  120 ,  122 , and/or  124  (see, e.g., components  102  of  FIG. 3 ). Adjustable components  120 ,  122 , and  124  may sometimes be referred to herein as tuning components, tunable components, tuning circuits, tunable circuits, or adjustable tuning components. 
     Adjustable component  120  may bridge slot  114  at a first location along slot  114  (e.g., component  120  may be coupled between terminal  126  on ground plane  104  and terminal  128  on peripheral conductive structures  16 ). Adjustable component  122  may bridge slot  114  at a second location along slot  114  (e.g., component  122  may be coupled between terminal  130  on ground plane  104  and terminal  132  on peripheral conductive structures  16 ). Adjustable component  124  may bridge slot  114  at a third location along slot  114  (e.g., component  124  may be coupled between terminal  134  on ground plane  104  and a terminal  136  on peripheral conductive structures  16 ). Terminal  130  may be interposed between ground antenna feed terminal  100  and terminal  126  on ground plane  104 . Terminal  132  may be interposed between positive antenna feed terminal  98  and terminal  128  on peripheral conductive structures  16 . Ground antenna feed terminal  100  may be interposed between terminal  130  and terminal  134  on ground plane  104 . Positive antenna feed terminal  98  may be interposed between terminal  132  and terminal  136  on peripheral conductive structures  16 . 
     Antenna  40  may include an adjustable matching network such as adjustable matching circuitry  140  that is interposed in transmission line path  92 . Control circuitry  28  ( FIG. 2 ) may provide control signals to adjust matching circuitry  140  (e.g., to provide a selected matching impedance between transmission line  92  and antenna feed  112 ). 
     Coupler circuitry such as coupler  142  (e.g., a directional coupler or other radio-frequency coupler) may be used to tap antenna signals flowing to and from antenna  40 . Tapped antenna signals from coupler  142  may be conveyed to control circuitry  28  over coupler path  144  (e.g., via a feedback receiver in transceiver circuitry  90 ). Coupler path  144  may sometimes be referred to herein as feedback path  144 . 
     The tapped antenna signals may be processed by the feedback receiver and/or control circuitry  28 . For example, control circuitry  28  may gather impedance data such as phase and magnitude information from the tapped antenna signals on path  144  to determine the impedance of antenna  40  during operation of wireless circuitry  34 . Control circuitry  28  may convert the phase and magnitude values measured using signals over path  144  to complex impedance data points (values). The complex impedance data points may include, for example, scattering parameter values (e.g., values of so-called “S-parameters”) that are indicative of the complex impedance of antenna  40 . Measurements of the S-parameters may include measured reflection coefficient parameter values (S11 values) that are indicative of the amount of radio-frequency signals that is reflected back towards coupler  142  from antenna  40  during signal transmission, for example. Other impedance measurements may be gathered if desired. 
     Components  120 ,  122 , and  124  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 . This example is merely illustrative and, in general, components  120 ,  122 , and  124  may include other components such as adjustable return path switches, switches coupled to capacitors, or any other desired components. 
     As shown in  FIG. 6 , adjustable component  120  includes a radio-frequency switching circuit such as switch  150 , adjustable component  122  includes a radio-frequency switching circuit such as switch  152 , and adjustable component  124  includes a radio-frequency switching circuit such as switch  154 . Adjustable component  120  may include a first inductor L 1  and a second inductor L 2  coupled in parallel between switch  150  and terminal  128 . Adjustable component  122  may include a third inductor L 3 , a fourth inductor L 4 , a fifth inductor L 5 , and a sixth inductor L 6  coupled in parallel between switch  152  and terminal  132 . Adjustable component  124  may include a seventh inductor L 7  and an eighth inductor L 8  coupled in parallel between switch  154  and terminal  136 . Inductors L 1  through L 8  may sometimes be referred to herein as switchable inductors. This example is merely illustrative and, in general, components  120 ,  122 , and  124  may include any desired number of inductive, capacitive, resistive, and switching components coupled between ground plane  104  and peripheral conductive structures  16  in any desired manner. 
     Switches  150  and  154  may each include single-pole double-throw (SP2T) switches and switch  152  may include a single-pole four-throw (SP4T) switch, for example. In this example, switch  150  may have a first state in which inductor L 1  is coupled to terminal  126  and inductor L 2  is decoupled from terminal  126  and a second state in which inductor L 2  is coupled to terminal  126  and inductor L 1  is decoupled from terminal  126 . Switch  154  may have a first state in which inductor L 7  is coupled to terminal  134  and inductor L 8  is decoupled from terminal  134  and a second state in which inductor L 8  is coupled to terminal  134  and inductor L 7  is decoupled from terminal  134 . Switch  152  may have a first state at which inductor L 3  is coupled to terminal  130  and inductors L 4 , L 5 , and L 6  are decoupled from terminal  130 , a second state at which inductor L 4  is coupled to terminal  130  and inductors L 3 , L 5 , and L 6  are decoupled from terminal  130 , a third state at which inductor L 5  is coupled to terminal  130  and inductors L 3 , L 4 , and L 6  are decoupled from terminal  130 , and a fourth state at which inductor L 6  is coupled to terminal  130  and inductors L 3 , L 4 , and L 5  are decoupled from terminal  130 . 
     This example is merely illustrative. If desired, switch  150  may have a third state in which both inductors L 1  and L 2  are decoupled from terminal  126  (e.g., in which adjustable component  120  forms an open circuit between terminal  126  and terminal  128 ) and/or a fourth state at which both inductors L 1  and L 2  are coupled to terminal  126 . If desired, switch  154  may have a third state at which both inductors L 7  and L 8  are decoupled from terminal  134  (e.g., in which adjustable component  124  forms an open circuit between terminals  134  and  136 ) and/or a fourth state at which both inductors L 7  and L 8  are coupled to terminal  134 . If desired, switch  152  may have multiple additional states at which any desired combination of inductors L 3 , L 4 , L 5 , and L 6  are coupled to terminal  130  or at which an open circuit is formed between terminals  130  and  132 . If desired, switches  120 ,  122 , and/or  124  may have additional states at which short circuit paths (e.g., short circuit paths without inductors) are connected between ground  104  and peripheral conductive structures  16 . 
     Adjustable matching circuitry  140  may include switching circuitry and circuit components such as resistive, capacitive, and/or inductive components coupled in any desired manner between transmission line  92 , ground  104 , antenna feed  112 , and/or antenna resonating element arm  108 . The switching circuitry in adjustable matching circuitry  140  may be controlled to place circuitry  140  in one of any desired number of states. Matching circuitry  140  may exhibit different impedances in each of the states. For example, matching circuitry  140  may have a first state at which matching circuitry  140  exhibits a first impedance and a second state at which matching circuitry exhibits a second impedance. If desired, matching circuitry  140  may include an SP2T switch that switches matching network  140  between the first and second impedances. As one example, matching network  140  may include a first (shunt) inductor coupled in series with a first single-pole single-throw switch between positive signal path  94  and ground  104  and a second (shunt) inductor coupled in series with a second single-pole single-throw switch between positive signal path  94  and ground  104 . The first single-pole single-throw switch may be opened and the second single-pole single-throw switch may be closed in the first state whereas the first switch is closed and the second switch is opened in the second state, for example. This is merely illustrative and, in general, any desired components may be formed in matching network  140 . 
     Using multiple adjustable components at different locations along slot  114  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 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. Adjustable components  120 ,  122 , and  124 , and matching circuitry  140  may be controlled (i.e., placed in a desired state) using control signals received from control circuitry  28 . 
     Slot  114  may have an elongated shape (e.g., a slot shape) or other suitable elongated gap shape. In the example of  FIG. 6 , slot  114  has a U shape that runs along the periphery of device  10  between peripheral conductive structures  16  (e.g., housing sidewalls) and portions of the rear wall of device  10  (e.g., ground  104 ). The ends of slot  114 , which may sometimes be referred to as open ends, may be formed by gaps  18  (e.g., gaps  18 - 1  and  18 - 2  of  FIG. 6 ). The length of slot  114  may be about 4-20 cm, more than 2 cm, more than 4 cm, more than 8 cm, more than 12 cm, less than 25 cm, less than 15 cm, less than 10 cm, or other suitable length. Slot  114  may have a width of about 2 mm (e.g., less than 4 mm, less than 3 mm, less than 2 mm, more than 1 mm, more than 1.5 mm, 1-3 mm, etc.) or other suitable width. In the example of  FIG. 6 , slot  114  has a U shape. If desired, slot  114  may have other shapes such as the straight slot shape. 
       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 . As shown in  FIG. 7 , antenna  40  may exhibit resonances in a low band LB, midband MB, high band HB, and ultra-high band UHB. This example is merely illustrative and, if desired, antenna  40  may exhibit resonances in a subset of these bands and/or in additional bands (e.g., a low-middle band LMB extending from 1400 MHz to 1710 MHz or other suitable frequency ranges). 
     Low band LB may extend from 700 MHz to 960 MHz or other suitable frequency range. Peripheral conductive structures  16  may serve as an inverted-F 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 feed  112  of  FIG. 6  and gap  18 - 2 , for example. Gap  18 - 2  may be one of gaps  18  in peripheral conductive housing structures  16 .  FIG. 6  is a view from the front of device  10 , so gap  18 - 2  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 components  122 ,  120 ,  124 , and/or matching circuitry  140  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  170  in low band LB. The antenna efficiency of curve  170  may be achieved by tuning antenna  40  to place antenna  40  in one of two or more tuning states (e.g., a first state characterized by curve  172 , a second state characterized by curve  174 , etc.). 
     High band HB may extend from 2300 MHz to 2700 MHz or other suitable frequency range. Antenna performance in high band HB may be supported by a parasitic antenna resonating element associated with antenna  40 , for example. The parasitic antenna resonating element 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, the parasitic antenna resonating element may be coupled to antenna resonating element  108  (e.g., peripheral structures  16 ) by near-field electromagnetic coupling (e.g., the parasitic element may be indirectly fed via near-field coupling whereas peripheral structures  16  are directly fed using antenna feed  112 ). As an example, the parasitic antenna resonating element may be based on a slot antenna resonating element structure formed from a portion of slot  114  (e.g., a slot for a slot-based parasitic antenna resonating element may be formed between opposing metal structures in peripheral structures  16  and/or antenna ground  104 ). In another suitable arrangement, antenna performance in high band HB may be supported by a harmonic mode of a resonance supported by antenna arm  108 . 
     Midband MB may extend from 1710 MHz to 2170 MHz or other suitable frequency range. The resonance of antenna  40  at midband MB may be associated with the distance along peripheral conductive structures  16  between component  120  of  FIG. 6  and feed  112  and/or the distance along peripheral conductive structures  16  between feed  112  and gap  18 - 1 , for example. Antenna  40  may exhibit first and second resonances in midband MB (e.g., resonances at different frequencies within midband MB as shown by curves  176  and  178 ). Tunable components such as components  122 ,  120 ,  124 , and/or matching circuitry  140  may be used to tune the response of antenna  40  in midband MB. As shown in  FIG. 7 , antenna  40  may have an antenna efficiency characterized by curve  180  in midband MB. The antenna efficiency of curve  180  may be achieved by tuning antenna  40  to place antenna  40  in one of two or more tuning states (e.g., a first state characterized by curve  176 , a second state characterized by curve  178 , etc.). 
     Ultra-high band UHB may extend from 3400 MHz to 3800 MHz or other suitable frequency range. Antenna performance in ultra-high band UHB may be supported by a harmonic mode of one of the other resonances supported by antenna  40 , as an 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 midband performance of antenna  40  may be characterized by curve  176 , the low band performance of antenna  40  may be characterized by curve  170 , and the ultra-high band performance of antenna  40  may be characterized by curve  182  of  FIG. 7 . In the presence of external loading, however, efficiency may be degraded (see, e.g., degraded efficiency curves  184 ,  186 , and  188 ). 
     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. To accommodate various loading scenarios, device  10  may use sensor data, antenna measurements, 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 or other external object). Device  10  (e.g., control circuitry  28 ) may then adjust adjustable components  102  in antenna  40  to compensate for the loading. With compensation, the performance of an antenna that is being loaded may be restored from a degraded efficiency curve such as curves  184 ,  186 , and  188  of  FIG. 7  to unimpaired (free space) efficiency curves  170 ,  176 , and  182 . Similarly, the presence of antenna loading can detune the antenna in different bands. For example, if antenna  40  is intended to be tuned to a midband frequency associated with curve  178 , the antenna loading can detune the antenna to exhibit a detuned resonance as shown by curve  186  or can otherwise reduce the antenna efficiency in midband MB (e.g., as shown by curve  186 ). With compensation, the performance of the antenna that is being loaded may be restored to unimpaired curve  178 . Similarly, if antenna  40  is intended to be tuned to a low band frequency associated with curve  174 , the antenna loading can detune the antenna to exhibit a detuned resonance as shown by curve  172 , or can otherwise reduce the antenna efficiency in low band LB (e.g., as shown by curve  184 ). With compensation, the performance of the antenna that is being loaded may be restored to unimpaired curve  174 . 
     In compensating for antenna loading, control circuitry  28  may control adjustable component (circuit)  120  (e.g., using control signals supplied to component  120 ) to apply a desired inductance value (e.g., L 1  or L 2 ) or to create an open circuit between terminals  128  and  126 . Control circuitry  28  may control adjustable component  122  to apply a desired inductance value (e.g., L 3 , L 4 , L 5 , or L 6 ) or to create an open circuit between terminals  130  and  132 . Control circuitry  28  may control adjustable component  124  to apply a desired inductance value (e.g., L 7  or L 8 ) or to create an open circuit between terminals  134  and  136 . Control circuitry  28  may control matching circuitry  140  to exhibit a selected one of a number of possible impedances. 
     As shown in  FIG. 6 , housing edge  12 - 1  is associated with the right edge of housing  12  when device  10  is viewed from the front and edge  12 - 2  is associated with the left edge of housing  12  when device  10  is viewed from the front. 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 - 1  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 - 2  of housing  12 . Device  10  may typically be oriented in a first orientation (e.g., a first range of orientations) when being held to the user&#39;s head with the user&#39;s right hand. In this situation, loading from the user&#39;s hand may affect the midband resonance associated with the distance between feed  112  and gap  18 - 1 . In addition, the user&#39;s palm may form a short circuit across gap  18 - 1  or otherwise alter a capacitance between arm  108  and ground  104  associated with gap  18 - 1 . 
     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 - 2  of  FIG. 6 ) and the fingers of the user&#39;s left hand will rest along edge  12 - 1  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 - 2 . Device  10  may typically be oriented in a second orientation (e.g., a second range of orientations) when being held to the user&#39;s head in with the user&#39;s left hand. In addition, the user&#39;s palm may form a short circuit across gap  18 - 2  or otherwise alter a capacitance associated with gap  18 - 2 . 
     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 operating environment is present and may adjust the adjustable circuitry of antenna  40  accordingly to compensate. Control circuitry  28  may, in general, use any suitable type of sensor measurements, wireless signal measurements, or antenna measurements to determine how device  10  is being used. 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, or other sensors to detect the presence of user&#39;s hand or other object on the left or right side of device  10 . Control circuitry  28  may also use information from an orientation sensor 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). If desired, an impedance sensor such as coupler  142  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 . 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. 
     Adjustable components  120 ,  122 , and  124  may sometimes be collectively referred to herein as aperture tuning circuitry (e.g., because components  120 ,  122 , and  124  may tune the resonance of slot aperture  114  between ground plane  104  and conductive structures  16 ). Adjustable matching network  140  may sometimes be referred to herein as impedance tuning circuitry. The impedance tuning circuitry may include any other desired components coupled between different portions of peripheral structures  16  and/or ground  104  if desired. The aperture tuning circuitry may include other components coupled between different portions of resonating element arm  108  if desired. 
     In practice, the particular adjustments that are performed by tuning components  120 ,  122 ,  124 , and  140  to compensate for antenna loading variations depend on the frequency band of interest. For example, first adjustments may be required to ensure satisfactory antenna efficiency when operating in midband MB and ultra-high band UHB whereas second adjustments may be required to ensure satisfactory antenna efficiency when operating in low band LB.  FIG. 8  is a flow chart of illustrative steps involved in operating device  10  to ensure satisfactory performance for antenna  40  in midband MB and ultra-high band UHB. 
     At step  200  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, 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 , or other sensors to determine how device  10  is being used. 
     If desired, control circuitry  28  may use device orientation sensor circuitry such as an inertial measurement unit to identify the orientation of device  10 . Inertial measurement units may include, for example, accelerometers that measure the orientation of the Earth&#39;s gravitational field and that can therefore measure the orientation and motion of device  10 , may include gyroscopes (gyroscopic sensors) that measure motion device  10  (e.g., angular motion), and/or sensors such as compasses (e.g., magnetic sensors, sometimes referred to as magnetometers) that measure orientation and that can therefore measure device movement. Inertial measurement units (e.g., microelectromechanical systems sensors) that include 3-axis accelerometer sensors, 3-axis gyroscopes, and 3-axis compasses may be used, for example. Information from a device orientation sensor such as an accelerometer in device  10  may be processed by control circuitry  28  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). 
     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. 
     If desired, control circuitry  28  may 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, control circuitry  28  may use an impedance sensor such as coupler  142  in monitoring the impedance of antenna  40  or part of antenna  40 . For example, control circuitry  28  may gather complex impedance values such as S11 measurements using signals gathered by coupler  142  that are indicative of the loading 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. 
     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 ). 
     At step  202 , control circuitry  28  may adjust the configuration of the aperture tuning circuitry in antenna  40  (i.e., components  120 ,  122 , and  124 ) based on the current operating environment of device  10  (e.g., based on data or information gathered while processing step  200 ). Control circuitry  28  may adjust the configuration of the aperture tuning circuitry by controlling the aperture tuning circuitry using one of a number of different sets of aperture tuning settings. Control circuitry  28  may select the set of aperture tuning settings to use based on the current operating environment of device  10  (e.g., circuitry  28  may select the optimal set of aperture tuning settings under current antenna loading conditions). As examples, controlling the aperture tuning circuitry using a first set of aperture tuning settings may involve controlling component  120  to couple one of inductors L 1  and L 2  to terminal  126  (e.g., to perform midband tuning using component  120 ) and setting components  122  and  124  to form open circuits, whereas controlling the aperture tuning circuitry using a second set of aperture tuning settings may involve controlling component  124  to couple one of inductors L 7  and L 8  to terminal  134  (e.g., to perform midband tuning using component  124 ) and setting components  120  and  122  to form open circuits. This is merely illustrative and, in general, each set of aperture tuning settings may involve controlling components  120 ,  122 , and  124  using any desired settings. Each set of aperture tuning settings may include different aperture tuning settings for components  120 ,  122 , and  124  depending on whether antenna  40  is being operated in midband MB or ultra-high band UHB. Control circuitry  28  may select which of these first and second sets of aperture tuning settings to use (or additional sets of aperture tuning settings to use) based on the current operating environment of device  10 . 
     As an example, control circuitry  28  may select the set of aperture tuning settings to use based on whether the data gathered while processing step  200  indicates that 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 by the user&#39;s right hand, control circuitry  28  may place antenna  40  in a right hand mode (e.g., by controlling aperture tuning components  120 ,  122 , and  124  using a first set of aperture tuning settings). If control circuitry  28  determines that device  10  is being held by the user&#39;s left hand, control circuitry  28  may place antenna  40  in the left hand mode (e.g., by controlling aperture tuning components  120 ,  122 , and  124  using a second set of aperture tuning settings). If control circuitry  28  determines that device  10  is in any other operating environment, control circuitry  28  may place antenna  40  in a default or free space mode (e.g., by controlling aperture tuning components using a third set of aperture tuning settings). By placing antenna  40  in one of these modes (e.g., in an optimal one of these modes), control circuitry  28  may ensure that antenna  40  operates satisfactorily in midband MB and ultra-high band UHB regardless of how the user is holding device  10 . 
     One or more different measurements about the operating environment of device  10  (e.g., as gathered while processing step  200 ) may be used in selecting the set of aperture tuning settings to use. For example, control circuitry  28  may determine whether audio is being played through ear speaker  26 , may use an accelerometer to determine whether device  10  is in motion, and may gather proximity sensor information using a proximity sensor. Control circuitry  28  may turn on a device orientation sensor to determine whether device  10  is being held in a user&#39;s left or right hand in response to determining that audio is being played through ear speaker  26 , that device  10  is in motion, and that an external object is in proximity to device  10 . This may, for example, reduce overall power consumption in device  10  relative to scenarios in which control circuitry  28  continuously gathers orientation sensor data to determine whether device  10  is being held in a user&#39;s left or right hand, as such a determination is only performed after other device information indicates that there is a relatively high probability that the user&#39;s hand is loading antenna  40 . 
     At step  204 , antenna  40  may be used to transmit and receive wireless data using the current set of aperture tuning settings for components  120 ,  122 , and  124  (e.g., as set during step  202 ). This process may be performed continuously, as indicated by line  206 . The example of  FIG. 8  is merely illustrative. If desired, matching circuitry  140  may be adjusted while processing step  202 . While the operations of  FIG. 8  are described in connection with performing antenna adjustments while operating in midband MB and ultra-high band UHB, the antenna adjustments may be performed while operating in any desired communication bands. 
     A state diagram showing illustrative operating modes for device  10  in performing wireless communications in midband MB and ultra-high band UHB using antenna  40  is shown in  FIG. 9 . 
     If it is determined that device  10  is being held in the right hand of a user (i.e., a non-free-space mode in which antenna  40  is being loaded along edge  12 - 1 ), control circuitry  28  may adjust the circuitry of antenna  40  to place device  10  in right hand mode  212 . Control circuitry  28  may place device  10  in right hand mode  212  by controlling aperture tuning circuitry  120 ,  122 , and  124  using a first set of aperture tuning settings. The first set of aperture tuning settings may include any desired combination of settings for components  120 ,  122 , and  124 . As an example, when handling midband MB, control circuitry  28  may control switch  150  to couple a given one of inductors L 1  and L 2  to terminal  126  (e.g., dependent upon whether resonance  176  or resonance  178  within midband MB as shown in  FIG. 7  is to be covered). When controlled using the first set of aperture tuning settings, control circuitry  28  may toggle switch  150  to change the particular midband frequency that is used over time. In other words, when controlled using the first set of aperture tuning settings, control circuitry  28  may use component  120  to perform midband tuning for antenna  40 . Control circuitry  28  may control switch  152  to form an open circuit between terminals  130  and  132 . Control circuitry  28  may control switch  154  to form an open circuit between terminals  134  and  136 . If desired, control circuitry  28  may control switch  154  to any arbitrary state (e.g., with one, both, or none of inductors L 7  and L 8  coupled to terminal  134 ) because, in the right hand mode, the user&#39;s palm may short currents from arm  108  to ground  104  across gap  18 - 1 , thereby minimizing the effect of component  124  on the resonance of antenna  40 . 
     If desired, the first set of aperture tuning settings may include different settings for components  120 ,  122 , and  124  when antenna  40  is being used to handle signals in ultra-high band UHB. For example, when handling ultra-high band UHB using the first set of aperture tuning settings, control circuitry  28  may control switch  152  to couple one or more of inductors L 3 , L 4 , L 5 , and L 6  to terminal  130  in addition to controlling component  120  to couple a given one of inductors L 1  and L 2  to terminal  126  (e.g., both components  120  and  122  may contribute to ultra-high band tuning for antenna  40 ). This example is merely illustrative and, in general, components  120 ,  122 , and  124  may be placed in any desired configuration when operated using the first set of aperture tuning settings (e.g., while device is operated in right hand mode  212 ). 
     If it is determined that device  10  is being held in the left hand of a user (i.e., a non-free-space mode in which antenna  40  is being loaded along edge  12 - 2 ), control circuitry  28  may adjust the circuitry of antenna  40  to place device  10  in left hand mode  214 . Control circuitry  28  may place device  10  in left hand mode  214  by controlling aperture tuning circuitry  120 ,  122 , and  124  using a second set of aperture tuning settings. The second set of aperture tuning settings is different from the first set of aperture tuning settings associated with right hand mode  212 . The second set of aperture tuning settings may include any desired combination of settings for components  120 ,  122 , and  124  that is different from the combination of settings for components  120 ,  122 , and  124  associated with the first set of aperture tuning settings. 
     As an example, when handling midband MB, control circuitry  28  may control switch  154  to couple a given one of inductors L 7  and L 8  to terminal  134  (e.g., dependent upon whether resonance  176  or resonance  178  of  FIG. 7  is to be covered). When controlled using the second set of aperture tuning settings, control circuitry  28  may toggle switch  154  to change the particular midband frequency that is used over time. In other words, when controlled using the second set of aperture tuning settings, control circuitry  28  may use component  124  to perform midband tuning for antenna  40 . Control circuitry  28  may control switch  152  to form an open circuit between terminals  130  and  132 . Control circuitry  28  may control switch  150  to form an open circuit between terminals  134  and  136 . If desired, control circuitry  28  may control switch  150  to any arbitrary state (e.g., with one, both, or none of inductors L 1  and L 2  coupled to terminal  126 ) because, in the left hand mode, the user&#39;s palm may short currents from arm  108  to ground  104  across gap  18 - 2 , thereby minimizing the effect of component  120  on the resonance of antenna  40 . 
     If desired, the second set of aperture tuning settings may include different settings for components  120 ,  122 , and  124  when antenna  40  is being used to handle signals in ultra-high band UHB. For example, when handling ultra-high band UHB using the second set of aperture tuning settings, control circuitry  28  may control switch  152  to couple one or more of inductors L 3 , L 4 , L 5 , and L 6  to terminal  130  in addition to controlling component  124  to couple a given one of inductors L 7  and L 8  to terminal  134  (e.g., both components  124  and  122  may contribute to ultra-high band tuning for antenna  40 ). This example is merely illustrative and, in general, components  120 ,  122 , and  124  may be placed in any desired configuration when operated using the second set of aperture tuning settings (e.g., while device is operated in left hand mode  214 ). 
     If it is determined that device  10  is operating in a free space mode or that device  10  is operating in neither the left hand mode nor the right hand mode, control circuitry  28  may adjust the circuitry of antenna  40  to place device  10  in default (free space) mode  210 . Control circuitry  28  may place device  10  in default mode  210  by controlling aperture tuning circuitry  120 ,  122 , and  124  using a third set of aperture tuning settings. The third set of aperture tuning settings may be different from the first and second sets of aperture tuning settings associated with the right and left hand modes. In another suitable arrangement, the third set of aperture tuning settings may be identical to either the first set of aperture tuning settings associated with right hand mode  212  or the second set of aperture tuning settings associated with left hand mode  214 . 
     In each of modes  210 ,  212 , and  214 , control circuitry  28  may collect and analyze sensor data such as proximity sensor data, orientation sensor data, temperature sensor data, and other sensor data, may collect and analyze received signal strength data, call state data, and other wireless settings, and may collect and analyze antenna performance information such as antenna impedance information (e.g., S11 values) and other antenna feedback information (e.g., while performing step  200  of  FIG. 8 ) to determine whether device  10  is being used in one of the other modes that loads antenna  40  in a way that can be compensated by adjusting the adjustable circuitry of antenna  40 . When it is determined that the antenna loading has changed, control circuitry  28  may adjust the aperture tuning settings to adjust device  10  between modes  210 ,  212 , and  214  to compensate for the change in antenna loading (e.g., while processing step  202  of FIG.  8 ). 
     For example, if device  10  is being held in a user&#39;s left hand and device  10  is currently in right hand mode  212  (e.g., antenna  40  is currently tuned using the first set of aperture tuning settings), antenna loading from the user&#39;s left hand may cause antenna  40  to exhibit deteriorated antenna efficiency (e.g., as shown by curves  186  and  188  of  FIG. 7 ). By adjusting device  10  to left hand mode  214  (e.g., by controlling antenna  40  using the second set of aperture tuning settings), antenna  40  may exhibit satisfactory antenna efficiency (e.g., as shown by curves  176  and  182  of  FIG. 7 ). Similarly, if device  10  is being held in a user&#39;s right hand and device  10  is currently operated in left hand mode  214  (e.g., antenna  40  is currently tuned using the second set of aperture tuning settings), antenna loading from the user&#39;s right hand may cause antenna  40  to exhibit deteriorated antenna efficiency (e.g., as shown by curves  186  and  188 ). By placing device  10  in right hand mode  212  (e.g., by controlling antenna  40  using the first set of aperture tuning settings), antenna  40  may exhibit satisfactory antenna efficiency (e.g., as shown by curves  176  and  182 ). 
     If desired, control circuitry  28  may process impedance data (e.g., S11 measurements) to determine whether the user&#39;s hand is covering one, both, or neither of gaps  18 - 2  and  18 - 1 . Control circuitry  28  may use this information about whether the user&#39;s hand is covering one, both, or neither of gaps  18 - 1  and  18 - 2  in selecting the set of aperture tuning settings to use. For example, control circuitry  28  may compare the magnitude of gathered S11 values to a pre-calibrated range of S11 values that are known to be associated with the user&#39;s hand covering only a single one of gaps  18 - 1  and  18 - 2 . The range of S11 values may be defined between (e.g., defined by) a minimum S11 magnitude threshold value and a maximum S11 magnitude threshold value. If control circuitry  28  determines that gathered S11 values are within the predetermined range (e.g., greater than the minimum S11 magnitude threshold value and less than the maximum S11 magnitude threshold value), control circuitry  28  may determine that only one of gaps  18 - 1  and  18 - 2  are covered. If control circuitry  28  determines that the gathered S11 values are less than the minimum S11 magnitude threshold value, control circuitry  28  may determine that neither or both of gaps  18 - 1  and  18 - 2  are covered. If desired, control circuitry  28  may place antenna  40  in left hand mode  214  in response to determining that only one gap is covered and that device  10  is being held by the user&#39;s left hand (e.g., using orientation sensor data or any other desired data gathered while processing step  200 ). Control circuitry  28  may place antenna  40  in right hand mode  212  in response to determining that only one gap is covered and that device  10  is being held in the user&#39;s right hand. Control circuitry  28  may place antenna  40  in default mode  210  in response to determining that neither or both of gaps  18 - 1  and  18 - 2  are covered. 
     The example of  FIG. 9  is merely illustrative. If desired, device  10  may be operated in more than three midband and ultra-high band tuning states (e.g., antenna  40  may be controlled using four or more sets of aperture tuning settings). If desired, matching network  140  may be placed in different configurations in each state. While described above in connection with midband MB and ultra-high band UHB, each state may control antenna tuning in any desired frequency band. If desired, control circuitry  28  may perform different antenna adjustments to ensure satisfactory antenna efficiency for antenna  40  under different antenna loading conditions while operating in low band LB. 
       FIG. 10  is a flow chart of illustrative steps involved in operating device  10  to ensure satisfactory performance for antenna  40  in low band LB. The steps of  FIG. 10  may, for example, be performed by control circuitry  28 . 
     Control circuitry  28  may collectively place aperture tuning circuits  120 ,  122 , and  124  into a particular configuration or state (sometimes referred to herein as an aperture tuning state). Each aperture tuning state may include corresponding settings for adjustable components  120 ,  122 , and  124  (e.g., each aperture tuning state may correspond to a different combination of settings for components  120 ,  122 , and  124 ). For example, in a first aperture tuning state, switch  150  may couple inductor L 1  to terminal  126 , switch  152  couples inductor L 3  to terminal  130 , and switch  154  forms an open circuit, in a second aperture tuning state switch  150  couples inductor L 2  to terminal  126 , switch  152  couples inductor L 4  to terminal  130 , and switch  154  couples inductor L 8  to terminal  134 , in a third aperture tuning state switch  150  forms an open circuit, switch  152  couples inductor L 3  to terminal  130 , and switch  154  forms an open circuit, etc. Every possible combination of settings for components  120 ,  122 , and  124  may represent a corresponding aperture tuning state for antenna  40 . 
     Similarly, control circuitry  28  may place impedance tuning circuitry  140  into a particular configuration or state (sometimes referred to herein as an impedance tuning state). Each impedance tuning state may include corresponding settings for matching circuitry  140  (e.g., each impedance tuning state may correspond to a different impedance exhibited by circuitry  140 ). As an example, impedance matching circuitry  140  may have a first impedance tuning state at which circuitry  140  exhibits a first impedance and may have a second impedance tuning state at which circuitry  140  exhibits a second impedance that is different from the first impedance. In general, impedance matching circuitry  140  may have any desired number of impedance tuning states. 
     Control circuitry  28  may place antenna  40  into a particular configuration or state (sometimes referred to herein as a tuning state or antenna tuning state). Each tuning state may include a corresponding impedance tuning state for circuitry  140  and a corresponding aperture tuning state for the aperture tuning circuitry (e.g., each tuning state of antenna  40  may correspond to a different respective combination of impedance tuning state and aperture tuning state). Changing either the impedance tuning state or the aperture tuning state changes the tuning state of antenna  40 , for example. The number of tuning states of antenna  40  may be equal to the product of the number of impedance tuning states and the number of aperture tuning states. For example, when antenna  40  has two aperture tuning states and two impedance tuning states, antenna  40  may have a total of four tuning states, when antenna  40  has three aperture tuning states and three impedance tuning states, antenna  40  may have a total of nine tuning states, when antenna  40  has two aperture tuning states and three impedance tuning states, antenna  40  may have a total of six tuning states, etc. 
     At step  220  of  FIG. 10 , control circuitry  28  may place (set) antenna  40  in an initial tuning state. The initial tuning state may be selected from a predetermined set of N allowed tuning states. The N allowed tuning states may, for example, be determined based on calibration of device  10  (e.g., during device manufacture or calibration). The N allowed tuning states may be less than the total number of possible tuning states of antenna  40 . For example, in the arrangement of  FIG. 6 , there may be four tuning states of antenna  40  (e.g., corresponding to four different combinations of two aperture tuning states and two impedance tuning states) even though there are more than four total combinations of settings for components  120 ,  122 ,  124 , and  140 . The N allowed tuning states may be, for example, tuning states that have an effect on the tuning or efficiency of antenna  40  at the frequency band of interest (e.g., as determined during calibration of device  10 ). The initial tuning state may include an initial impedance tuning state for circuitry  140  and an initial aperture tuning state for circuits  120 ,  122 , and  124 . 
     Control circuitry  28  may gather impedance measurements (e.g., S11 values) using coupler  142  while antenna  40  is placed in the initial tuning state. Control circuitry  28  may store the measured S11 values on storage circuitry (e.g., memory) for subsequent processing. 
     In some scenarios, control circuitry  28  sweeps through each of the N allowed tuning states of antenna  40  before selecting the tuning state to use for communications. In this scenario, control circuitry  28  may gather S11 values at each of the N tuning states in the sweep and then after stepping through each tuning state, may process the S11 values to select the tuning state to use for subsequent communications (i.e., the tuning state for which antenna  40  has maximum efficiency given the current antenna loading conditions). However, sweeping through each of the N tuning states requires antenna  40  to spend a significant amount of time at tuning states that may be associated with relatively low antenna efficiency given the current antenna loading conditions. This may lead to a relatively high likelihood of the communications link between antenna  40  and external communications equipment (e.g., a telephone call handled by antenna  40 ) being dropped. 
     In order to mitigate these risks, control circuitry  28  may adjust the tuning state of antenna  40  by first adjusting the impedance tuning state of circuitry  140  (step  222 ). Control circuitry  28  may subsequently gather S11 values or other impedance data using coupler  142 . 
     At step  224 , control circuitry  28  may adjust the tuning state of antenna  40  by adjusting one of the impedance tuning state or the aperture tuning state. Control circuitry  28  may, if desired, adjust the tuning state back to the immediately previous tuning state (e.g., back to the initial tuning state during the first iteration of the steps of  FIG. 10  by reversing the impedance tuning state adjustment performed at step  222 ). Control circuitry  28  may select the tuning state to adjust to (of the N allowed tuning states) based on the S11 values gathered during the current (active) tuning state and the immediately previous tuning state (e.g., using S11 values gathered while processing step  222  and  220  in the first iteration of the steps of  FIG. 10 ). 
     For example, control circuitry  28  may select the tuning state to tune to based on a comparison of the S11 values during the current tuning state to the S11 values gathered during the immediately previous tuning state. The comparison may be performed between individual S11 values gathered in each tuning state or between a combination of S11 values gathered in each tuning state (e.g., an average or linear combination of multiple S11 values in each tuning state). In one suitable arrangement, control circuitry  28  may revert to the immediately previous tuning state in response to determining that the magnitude of S11 values gathered in the current tuning state is greater than the magnitude of S11 values gathered during the immediately previous tuning state. In this example, control circuitry  28  may adjust the tuning state by changing one (but not both) of the aperture tuning state and the impedance tuning state in response to determining that the magnitude of S11 values gathered in the current tuning state is less than or equal to the magnitude of S11 values gathered during the immediately previous tuning state. By adjusting only one of the aperture tuning state or the impedance tuning state at a time when adjusting the antenna tuning state (and potentially reverting to the previous tuning state), control circuitry  28  may reduce the risk of dropping the communications link with external equipment relative to scenarios where both the impedance tuning state and the aperture tuning state are adjusted at the same time. 
     At step  226 , once control circuitry  28  has adjusted the tuning state (e.g., by adjusting the aperture tuning state or the impedance tuning state, potentially reverting to the previous antenna tuning state), control circuitry may gather additional S11 values. Control circuitry  28  may determine whether the additional S11 values gathered at the current tuning state satisfy predetermined wireless performance criteria. 
     The predetermined wireless performance criteria may, for example, include a predetermined range of acceptable S11 values. The predetermined range of acceptable S11 values may be defined by a maximum S11 magnitude threshold value. In this example, control circuitry  28  may determine whether the additional S11 values satisfy the predetermined wireless performance criteria by determining whether the additional S11 measurements fall within the predetermined range of acceptable S11 values (e.g., by determining whether the magnitude of the additional S11 values is less than the maximum S11 magnitude threshold value). If the additional S11 values fall within the predetermined range (e.g., if the S11 values or an average or other combination of the S11 values has a magnitude that falls below the maximum S11 magnitude threshold value), control circuitry  28  may determine that the wireless performance criteria have been satisfied. Otherwise, control circuitry  28  may determine that the wireless performance criteria have not been satisfied. This example is merely illustrative and, in general, any desired wireless performance criteria may be used. 
     If control circuitry  28  determines that the wireless performance criteria have been satisfied, processing may proceed to step  230  as shown by path  228 . At step  230 , control circuitry  28  may control antenna  40  to remain at the current tuning state. Control circuitry  28  may continue to gather S11 information if desired. Antenna  40  may transmit and/or receive signals at the current tuning state until the magnitude of the measured S11 values fall below the maximum S11 magnitude threshold value (e.g., until the loading conditions of antenna  40  change). In another suitable arrangement, antenna  40  may remain at the current tuning state for a predetermined amount of time. In general, any antenna  40  may remain at the current tuning state until any other desired trigger condition occurs. Once the trigger condition occurs (e.g., once the loading conditions of antenna  40  have changed, a predetermined amount of time has passed, device  10  changes operating modes, etc.), the steps of  FIG. 10  may be re-initialized using the current tuning state, the first tuning state (e.g., the initial tuning state from the first iteration of the steps of  FIG. 10 ), or any other desired tuning state as the initial tuning state set at step  220 . 
     If control circuitry  28  determines that the wireless performance criteria have not been satisfied while processing step  226 , processing may proceed to step  234  as shown by path  232 . At step  234 , control circuitry  28  may determine whether the S11 values gathered at the current tuning state (i.e., the tuning state that was selected during the current iteration of step  224 ) are superior to the S11 values gathered at the other N−1 allowable tuning states. For example, circuitry  28  may compare the magnitude of the S11 values gathered at the current tuning state to the magnitude of S11 values gathered at the other N−1 allowable tuning states. If the magnitude of the S11 values at the current tuning state is less than the magnitude of the S11 values gathered at the other N−1 allowable tuning states, control circuitry  28  may determine that the S11 values gathered at the current tuning state are superior to the S11 values gathered at the other N−1 allowable tuning states. Otherwise, control circuitry  28  may determine that the S11 values gathered at the current tuning state are not superior to the S11 values gathered at the other N−1 allowable tuning states. 
     If control circuitry  28  determines that the S11 values gathered at the current tuning state are superior to the S11 values gathered at the other N−1 allowable tuning states, processing may proceed to step  230  as shown by path  238 . If control circuitry  28  determines that the S11 values gathered at the current tuning state are superior to the S11 values gathered at the other N−1 allowable tuning states, processing may loop back to path  224  as shown by path  236 . Control circuitry  28  may subsequently perform additional iterations of aperture tuning state or impedance tuning state adjustments (potentially reverting back to any immediately previous tuning state) until the wireless performance criteria is satisfied. Step  234  may be omitted in the first iteration of  FIG. 10  or may be omitted from every iteration of  FIG. 10  if desired (e.g., path  232  may loop back directly to step  224  over path  236  if desired). The 
     Control circuitry  28  may select whether the aperture tuning state or the impedance tuning state is adjusted in processing step  224  based on any desired criteria such as the S11 measurements gathered in one or more previous tuning states. If desired, control circuitry  28  may select whether to adjust the aperture tuning state or the impedance tuning state when switching to the next antenna tuning state based on whether the impedance tuning state or aperture tuning state was adjusted to reach the current antenna tuning state. For example, control circuitry  28  may adjust the impedance tuning state if the previous antenna tuning state adjustment was performed by adjusting the aperture tuning state (e.g., if the aperture tuning state was adjusted during the previous iteration of  FIG. 10 ). Control circuitry  28  may adjust the aperture tuning state if the previous antenna tuning state adjustment was performed by adjusting the impedance tuning state (e.g., if the impedance tuning state was adjusted during the previous iteration of  FIG. 10 ). This may apply only to scenarios where control circuitry  28  does not revert to the immediately previous tuning state while processing step  224 , for example. The example of  FIG. 10  in which S11 measurements are used to adjust the tuning state is merely illustrative. In general, any desired impedance measurements or other wireless performance metric data may be used. 
     By processing the S  11  data to determine whether to adjust the antenna tuning state, alternating between aperture tuning state adjustments and impedance tuning state adjustments, and potentially reverting back to an immediately previous tuning state at each iteration of step  226  of  FIG. 10 , control circuitry  28  may reduce the risk of dropping the wireless link (e.g., dropping a telephone call with external equipment) relative to scenarios in which control circuitry  28  blindly sweeps through each of the N tuning states before identifying a tuning state at which to remain. In practice, adjusting the impedance tuning state may involve less risk of dropping the communications link than adjusting the aperture tuning state. Performing the first antenna tuning state adjustment by adjusting the impedance tuning state (e.g., while processing step  222 ) may involve less overall risk of dropping the wireless link than if the aperture tuning state were adjusted first. Processing the steps of  FIG. 10  may allow control circuitry  28  to actively place antenna  40  in an optimal tuning state for communications in a selected frequency within low band LB given the current antenna loading conditions, even if the antenna loading conditions change over time. For example, even if a user&#39;s grip deteriorates the antenna efficiency of antenna  40  in low band LB (e.g., as shown by curve  184  of  FIG. 7 ), performing the steps of  FIG. 10  may allow antenna  40  to exhibit satisfactory antenna efficiency (e.g., as shown by curves  172 ,  172 , and  174  of  FIG. 7 ) regardless the user&#39;s grip on device  10 . 
     A state diagram showing illustrative operating modes for device  10  in performing wireless communications in low band LB using antenna  40  is shown in  FIG. 11 . In the example of  FIG. 11 , control circuitry  28  places antenna  40  in one of four different allowable tuning states (e.g., there may be N=4 allowable tuning states). This is merely illustrative and, in general, there may be any desired number of antenna tuning states. 
     In the example of  FIG. 11 , control circuitry  28  may adjust antenna  40  between a first tuning state  250 , a second tuning state  252 , a third tuning state  254 , and a fourth tuning state  256 . In first tuning state  250 , control circuitry  28  may place impedance circuitry  140  in a first impedance tuning state and may place the aperture tuning circuitry in a first aperture tuning state. In second tuning state  252 , control circuitry  28  may place impedance circuitry  140  in the first impedance tuning state and may place the aperture tuning circuitry in a second aperture tuning state. In third tuning state  254 , control circuitry  28  may place impedance circuitry  140  in a second impedance tuning state and may place the aperture tuning circuitry in the first aperture tuning state. In fourth tuning state  256 , control circuitry  28  may place impedance circuitry  28  in the second impedance tuning state and may place the aperture tuning circuitry in the second aperture tuning state. 
     In some scenarios, control circuitry  28  blindly sweeps through each of tuning states  250 ,  252 ,  254 , and  256  and then processes S11 values gathered at each tuning state before identifying a tuning state in which to remain. In order to mitigate the risks associated with blindly sweeping through each tuning state in this manner, the processing operations of  FIG. 10  may be performed to adjust antenna  40  between the tuning states. 
     For example, control circuitry  28  may place antenna  40  in an initial tuning state such as first tuning state  250  (e.g., while processing step  220  of  FIG. 10 ). Control circuitry  28  may gather S11 values while antenna  40  is tuned to first tuning state  250 . Control circuitry  28  may subsequently adjust the impedance tuning state to the second impedance tuning state, which places antenna  40  into third tuning state  254  as shown by arrow  260  (e.g., while processing a first iteration of step  224  of  FIG. 10 ). Control circuitry  28  may gather S11 values while antenna  40  is tuned to third tuning state  250 . Control circuitry  28  may determine whether the S11 values gathered at tuning state  250  satisfy predetermined wireless performance criteria (e.g., while processing step  226  of  FIG. 10 ). 
     In response to determining that the S11 values satisfy the predetermined wireless performance criteria, control circuitry  28  may control antenna  40  to remain at state  254  (e.g., while processing step  230  of  FIG. 10 ). In response to determining that the S11 values fail to satisfy the predetermined wireless performance criteria, control circuitry  28  may adjust either the aperture tuning state to advance to state  256  as shown by arrow  262  (e.g., in scenarios where the magnitude of the S11 values gathered at state  254  are less than the magnitude of the S11 values gathered at state  250 ), or may adjust the impedance tuning state to revert to the immediately previous state (i.e., first state  250 ) as shown by path  264  (e.g., in scenarios where the magnitude of the S11 values gathered at state  254  are greater than or equal to those initially measured at state  250 ). 
     In scenarios where control circuitry  28  adjusts antenna  40  from tuning state  254  to tuning state  256 , control circuitry  28  may gather additional S11 values while antenna  40  is at fourth tuning state  256  and may compare those S11 values to the S11 values gathered at tuning state  254  to determine whether to remain at state  256 , advance to second tuning state  252  as shown by path  266 , or to revert to third tuning state  254  as shown by path  268  (e.g., while processing a second iteration of steps  224  and  226  of  FIG. 10 ). In scenarios where control circuitry  28  adjusts antenna  40  from tuning state  254  back to tuning state  250 , control circuitry  28  may gather additional S11 values at tuning state  250  and may compare those S11 values to the S11 values gathered at tuning state  254  to determine whether to remain at state  256 , advance to second tuning state  252  as shown by path  270 , or revert to third tuning state  254  as shown by path  260  (e.g., while processing a second iteration of steps  224  and  226  of  FIG. 10 ). Similar operations may be performed to remain at second tuning state  252 , to advance from tuning state  252  to fourth tuning state  256  as shown by arrow  272 , or to advance from tuning state  252  to first tuning state  250  as shown by arrow  274 . In this way, control circuitry  28  may alternate between adjustments to the aperture tuning state and the impedance tuning state, potentially reverting to a previous tuning state, until satisfactory S11 measurements are obtained (e.g., until satisfactory antenna efficiency given the current low band frequency and antenna loading conditions is obtained). 
     If desired, the steps of  FIG. 10  may be restarted (reset) at any desired time (e.g., control circuitry  40  may revert antenna  40  back to an initial state such as first tuning  250  regardless of the current tuning state of antenna  40 ). In one suitable arrangement, control circuitry  28  may determine whether to reset the operations of  FIG. 10  by perform offset comparison operations. 
       FIG. 12  is a Smith chart showing how offset comparison operations may be performed to reset low band tuning operations. In the Smith chart of  FIG. 12 , antenna impedances for antenna  40  are measured as a function of different operating conditions. A fifty ohm antenna impedance is characterized by impedance point  290  in  FIG. 12 . 
     Under a given loading condition, antenna  40  may exhibit an impedance at point  292  while tuned to a given tuning state such as third tuning state  254  of  FIG. 11 . When antenna  40  is adjusted to a different tuning state such as fourth tuning state  256  (e.g., while processing step  224  of  FIG. 10 ), the impedance exhibited by antenna  40  may shift to point  294  as shown by arrow  296 . In this example, control circuitry  28  may control antenna  40  to revert to the immediately previous tuning state (i.e., third tuning state  254 ). Reverting back to third tuning state  254  may cause antenna  40  to exhibit an impedance at point  298  as shown by arrow  300 . If the antenna loading conditions have not changed between measuring impedance  292  and  298 , impedance  298  will overlap with or lie in close proximity to point  292 . However, if the antenna loading conditions have changed, impedance  298  will be located relatively far away from impedance  292  on the Smith chart of  FIG. 12 . 
     In the example of  FIG. 12 , the antenna loading conditions have changed and impedance  298  is offset with respect to impedance  292 . Control circuitry  298  may identify the magnitude of the offset between points  298  and  292  and may compare the magnitude of the offset to an offset threshold, such as threshold  302 . If control circuitry  28  determines that the offset between points  298  and  292  exceeds the threshold, control circuitry  28  may reset the tuning state of antenna  40  (e.g., may place antenna  40  in the initial tuning state) and may restart the operations of  FIG. 10 . In the example of  FIG. 12 , because point  298  lies farther than threshold  302  away from point  292 , control circuitry  28  may reset the tuning state of antenna  40  to the initial tuning state and may restart the operations of  FIG. 10 . Such offset comparison operations may be performed while processing step  224  whenever reverting back to an immediately previous tuning state, for example. In this way, control circuitry  28  may ensure that antenna  40  is retuned to account for any changes in the loading conditions of antenna  40  in real time, for example. While the examples of  FIGS. 10-12  are described in connection with communications in low band LB, the operations of  FIGS. 10-12  may be performed for communications in any desired frequency bands. 
     Control circuitry  28  may be configured to perform these operations (e.g., the operations of  FIGS. 8-12 ) using hardware (e.g., dedicated hardware or circuitry) and/or software (e.g., code that runs on the hardware of device  10 ). Software code for performing these operations is stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media). The software code may sometimes be referred to as software, data, program instructions, instructions, or code. The non-transitory computer readable storage media may include non-volatile memory such as non-volatile random-access memory (NVRAM), one or more hard drives (e.g., magnetic drives or solid state drives), one or more removable flash drives or other removable media, other computer readable media, or combinations of these computer readable media or other storage. Software stored on the non-transitory computer readable storage media may be executed on the processing circuitry of control circuitry  28 . The processing circuitry may include application-specific integrated circuits with processing circuitry, one or more microprocessors, or other processing circuitry. 
     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: 20170523
Publication Date: 20190813
Grant Date: 20190813
Priority Date: 20170523
Inventors: HAN, LIANG
BIEDKA, THOMAS E.
MOW, MATTHEW A.
RAMACHANDRAN, IYAPPAN
PASCOLINI, MATTIA
HAN, XU
XU, HAO
EDWARDS, JENNIFER M.
YARGA, SALIH
ZHOU, YIJUN
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/401", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/245", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/026", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/401", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W4/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/401", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/245", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 64401423