PATENT DOCUMENT

Publication Number: US-11205834-B2
Application Number: US-201816019322-A
Country: US
Kind Code: B2

Title: Electronic device antennas having switchable feed terminals

Abstract:
An electronic device may include a conductive housing and an antenna. The antenna may include an arm formed from a first segment of the housing. A gap may separate the first segment from a second segment. The antenna may include a feed coupled to a transmission line having a signal conductor. The feed may include first and second positive terminals on the first segment and a third positive terminal on the second segment. An adjustable component may be coupled between the first and third terminals. The signal conductor may be coupled to the first terminal. A wide conductive trace may be coupled between the signal conductor and the second terminal. A switch may be interposed on the signal conductor. The second terminal may cover a cellular low band when the switch is open. The first terminal may cover the cellular low band and higher bands when the switch is closed.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a housing having peripheral conductive housing structures; 
 ground structures; 
 an antenna having a resonating element arm formed from a segment of the peripheral conductive housing structures that is separated from the ground structures by a slot; 
 a radio-frequency transmission line having a ground conductor coupled to the ground structures and having a signal conductor coupled to the segment; and 
 an adjustable component that is configured to tune a frequency response of the antenna and that has a first terminal coupled to the signal conductor, a second terminal coupled to the segment, and a third terminal coupled to the ground structures, wherein the adjustable component is configurable to decouple the first terminal from the second terminal and to form a return path between the second terminal and the third terminal. 
 
     
     
       2. The electronic device defined in  claim 1 , further comprising:
 a dielectric-filled gap in the peripheral conductive housing structures that separates the resonating element arm from an additional segment of the peripheral conductive housing structures. 
 
     
     
       3. The electronic device defined in  claim 2 , wherein the ground conductor is coupled to the ground structures at a ground antenna feed terminal, the signal conductor is coupled to a first positive antenna feed terminal on the segment, and the electronic device further comprises:
 a conductive path coupled between the first positive antenna feed terminal and a second positive antenna feed terminal on the additional segment. 
 
     
     
       4. The electronic device defined in  claim 3 , further comprising:
 an additional adjustable component interposed on the conductive path, wherein the additional adjustable component has a first state in which the resonating element arm is configured to indirectly feed radio-frequency signals to the additional segment via near field electromagnetic coupling, and the additional adjustable component has a second state in which the second positive antenna feed terminal conveys antenna currents from the signal conductor to the additional segment. 
 
     
     
       5. The electronic device defined in  claim 4 , wherein the additional adjustable component is configured to tune the frequency response of the antenna by coupling a selected inductance between the signal conductor and the second positive antenna feed terminal. 
     
     
       6. The electronic device defined in  claim 3 , further comprising:
 radio-frequency transceiver circuitry coupled to the radio-frequency transmission line; and 
 a switch interposed on the signal conductor, wherein the switch is coupled between the radio-frequency transceiver circuitry and the first terminal of the adjustable component. 
 
     
     
       7. The electronic device defined in  claim 6 , further comprising:
 a third positive antenna feed terminal on the segment; and 
 a conductive trace over the slot and coupled between a node on the signal conductor and the third positive antenna feed terminal, wherein the node is interposed between the radio-frequency transceiver circuitry and the switch. 
 
     
     
       8. The electronic device defined in  claim 7 , wherein the switch has a first state in which the third positive antenna feed terminal is active and the first and second positive antenna feed terminals are inactive and has a second state in which the first positive antenna feed terminal is active and the third positive antenna feed terminal is inactive. 
     
     
       9. An electronic device comprising:
 a housing having peripheral conductive housing structures; 
 ground structures, wherein a segment of the peripheral conductive housing structures is separated from the ground structures by a slot; 
 an antenna that comprises the ground structures, a resonating element arm formed from the segment, a ground antenna feed terminal coupled to the ground structures, and first and second positive antenna feed terminal coupled to the segment; 
 radio-frequency transceiver circuitry in the housing; 
 a radio-frequency transmission line coupled to the radio-frequency transceiver circuitry, wherein the radio-frequency transmission line comprises a ground conductor coupled to the ground antenna feed terminal and a signal conductor coupled to the first positive antenna feed terminal; 
 a switch interposed on the signal conductor; and 
 a conductive trace over the slot and coupled between a node on the signal conductor and the second positive antenna feed terminal, the node being interposed on the signal conductor between the switch and the radio-frequency transceiver circuitry. 
 
     
     
       10. The electronic device defined in  claim 9 , wherein the conductive trace is separated from the ground structures by a first distance and is separated from the segment by a second distance that is less than the first distance. 
     
     
       11. The electronic device defined in  claim 9 , wherein the conductive trace has a first end coupled to the node, an opposing second end coupled to the second positive antenna feed terminal, a length extending from the first end to the second end, and a width, the length being between two and ten times the width. 
     
     
       12. The electronic device defined in  claim 11 , further comprising:
 an adjustable inductor coupled between the second end of the conductive trace and the ground structures. 
 
     
     
       13. The electronic device defined in  claim 9 , further comprising:
 a dielectric-filled gap in the peripheral conductive housing structures that separates the resonating element arm from an additional segment of the peripheral conductive housing structures, wherein the antenna further comprises a third positive antenna feed terminal coupled to the additional segment and a conductive path coupled between the first positive antenna feed terminal and the third positive antenna feed terminal. 
 
     
     
       14. The electronic device defined in  claim 13 , further comprising:
 an adjustable component interposed on the conductive path, wherein a portion of the slot extends between the additional segment and the ground structures, the adjustable component having a first state in which the resonating element arm is configured to indirectly feed radio-frequency signals to the additional segment via near field electromagnetic coupling and a second state in which the third positive antenna feed terminal conveys antenna currents from the signal conductor to the additional segment. 
 
     
     
       15. The electronic device defined in  claim 13 , wherein the switch has an open state and a closed state, the segment and the second positive antenna feed terminal are configured to convey radio-frequency signals in a first frequency band while the switch is in the open state, the segment and the first positive antenna feed terminal are configured to convey radio-frequency signals in the first frequency band and a second frequency band that is higher than the first frequency band while the switch is in the closed state, and the additional segment and the third positive antenna feed terminal are configured to convey radio-frequency signals in a third frequency band that is higher than the second frequency band while the switch is in the closed state. 
     
     
       16. An antenna configured to receive radio-frequency signals from a radio-frequency transmission line having a signal conductor, the antenna comprising:
 ground structures; 
 a resonating element arm separated from the ground structures by a slot, wherein the slot comprises a portion extending between the ground structures and a conductive structure, the conductive structure being separated from the resonating element arm by a dielectric-filled gap; and 
 an antenna feed configured to convey the radio-frequency signals received from the radio-frequency transmission line, wherein the antenna feed has a ground antenna feed terminal coupled to the ground structures, first and second positive antenna feed terminals coupled the antenna resonating element arm, and a third positive antenna feed terminal coupled to the conductive structure. 
 
     
     
       17. The antenna defined in  claim 16 , further comprising:
 a conductive trace over the slot and coupled between a node on the signal conductor and the second positive antenna feed terminal; and 
 a switch coupled between the node and the first positive antenna feed terminal. 
 
     
     
       18. The antenna defined in  claim 17 , further comprising:
 a conductive path coupled between the first positive antenna feed terminal and the third positive antenna feed terminal; and 
 an adjustable component interposed on the conductive path, wherein the switch has open and closed states and the adjustable component has first and second states, the resonating element arm is configured to radiate in a first frequency band while the switch is in the open state, the resonating element arm is configured to radiate in the first frequency band and a second frequency band that is higher than the first frequency band while the switch is in the closed state, the conductive structure is configured to radiate in a third frequency band that is higher than the second frequency band while the switch is in the closed state and the adjustable component is in the first state, and the portion of the slot is configured to radiate in the third frequency band while the switch is in the closed state and the adjustable component is in the second state. 
 
     
     
       19. The electronic device defined in  claim 1 , wherein the adjustable component is configured, in a state, to form an open circuit between the first terminal and the second terminal by decoupling the first terminal from the second terminal and to form the return path between the second terminal and the third terminal. 
     
     
       20. The electronic device defined in  claim 19 , wherein the adjustable component is configured, in an additional state, to couple an impedance element between the first terminal and the third terminal and to form an open circuit between the second terminal and the third terminal.

Description:
BACKGROUND 
     This relates to electronic devices, and more particularly, to antennas for 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. 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components using compact structures. At the same time, there is a desire for wireless devices to cover a growing number of communications bands. For example, it may be desirable for a wireless device to cover many different cellular telephone communications bands at different frequencies. 
     Because antennas have the potential to interfere with each other and with components in a wireless device, care must be taken when incorporating antennas into an electronic device. Moreover, care must be taken to ensure that the antennas and wireless circuitry in a device are able to exhibit satisfactory performance over the desired range of operating frequencies. In addition, it is often difficult to perform wireless communications with a satisfactory data rate (data throughput), especially as software applications performed by wireless devices become increasingly data hungry. 
     It would therefore be desirable to be able to provide improved wireless communications circuitry for wireless electronic devices. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry and a housing having a peripheral conductive housing structures. The wireless circuitry may include an antenna, radio-frequency transceiver circuitry, and a radio-frequency transmission line. The transmission line may include a ground conductor and a signal conductor. The antenna may include a resonating element arm formed from a first segment of the peripheral conductive housing structures that is separated from ground structures by a slot. A dielectric-filled gap in the peripheral conductive housing structures may separate the first segment from a second segment of the peripheral conductive housing structures. A vertical portion of the slot may extend between the ground structures and the second segment. 
     The antenna may be fed using an antenna feed that conveys radio-frequency signals for the radio-frequency transmission line. The antenna feed may include a ground antenna feed terminal coupled to the ground structures, first and second positive antenna feed terminals coupled to the first segment, and a third positive antenna feed terminal coupled to the third segment. A conductive path may be coupled between the first and third positive antenna feed terminals. A first adjustable component may be interposed on the conductive path. The first adjustable component may have a first state in which the first segment indirectly feeds radio-frequency signals to the second segment in a cellular high band. The adjustable component may have a second state in which antenna currents are directly fed to the second segment through the third positive antenna feed terminal and in which the vertical portion of the slot radiates in the cellular high band. A second adjustable component may tune a frequency response of the antenna and may have a first terminal coupled to the signal conductor, a second terminal coupled to the first segment, and a third terminal coupled to the ground structures. 
     A conductive trace may be coupled between a node on the signal terminal and the second positive antenna feed terminal. The conductive trace may serve as a low-inductance feed combiner for the antenna. The conductive trace may have a width and a length that is between two and ten times the width to optimize the inductance between the signal conductor and the second positive antenna feed terminal. A switch may be interposed on the signal conductor between the node and the first positive antenna feed terminal. The first terminal of the second adjustable component may be interposed on the signal conductor between the switch and the first positive antenna feed terminal. 
     When the switch is in an open state, the second positive antenna feed terminal and the first segment may convey radio-frequency signals in a cellular low band. When the switch is in a closed state, the first positive antenna feed terminal and the first segment may convey radio-frequency signals in the cellular low band, a cellular low-midband, a cellular midband, and/or a cellular ultra-high band. The third antenna feed terminal and the vertical portion of the slot or the second segment may convey radio-frequency signals in the cellular high band while the switch is in the closed state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of illustrative circuitry in an electronic device in accordance with an embodiment. 
         FIG. 3  is a schematic diagram of illustrative wireless communications circuitry in accordance with an embodiment. 
         FIG. 4  is a diagram of illustrative wireless circuitry including multiple antennas for performing multiple-input and multiple-output (MIMO) communications in accordance with an embodiment. 
         FIG. 5  is a schematic diagram of an illustrative inverted-F antenna in accordance with an embodiment. 
         FIG. 6  is a schematic diagram of an illustrative slot antenna in accordance with an embodiment. 
         FIG. 7  is a top view of illustrative antennas formed from housing structures in an electronic device in accordance with an embodiment. 
         FIG. 8  is a top view of an illustrative antenna having multiple switchable signal feed terminals for optimizing radio-frequency performance across multiple different communications bands in accordance with an embodiment. 
         FIGS. 9A-9D  are circuit diagrams of illustrative adjustable components that may be formed in an antenna of the type shown in  FIG. 8  in accordance with an embodiment. 
         FIG. 10  is a flow chart of illustrative steps that may be involved in adjusting an antenna of the type shown in  FIG. 8  in accordance with an embodiment. 
         FIG. 11  is a plot of antenna performance (antenna efficiency) of an illustrative antenna of the type shown in  FIG. 8  in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. 
     The wireless communications circuitry may include one or 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 the electronic device. The peripheral conductive structures may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, may have portions that extend upwards from an integral planar rear housing (e.g., to form vertical planar sidewalls or curved sidewalls), and/or may form other housing structures. 
     Gaps may be formed in the peripheral conductive structures that divide the peripheral conductive structures into peripheral segments. One or more of the segments may be used in forming one or more antennas for electronic device  10 . Antennas may also be formed using an antenna ground plane and/or an antenna resonating element formed from conductive housing structures (e.g., internal and/or external structures, support plate structures, etc.). 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Device  10  may also be a set-top box, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, a wireless access point, wireless base station, an electronic device incorporated into a kiosk, building, or vehicle, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may be mounted on the front face of device  10 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or may be insensitive to touch. The rear face of housing  12  (i.e., the face of device  10  opposing the front face of device  10 ) may have a rear housing wall (e.g., 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 (rear housing wall portions and/or sidewall portions) of housing  12  from each other. The rear housing wall may include conductive portions and/or dielectric portions. If desired, the rear housing wall may include a planar metal layer covered by a thin layer or coating of dielectric such as glass, plastic, sapphire, or ceramic. Housing  12  (e.g., the rear housing wall, sidewalls, etc.) may also have shallow grooves that do not pass entirely through housing  12 . The slots and grooves may be filled with plastic or other dielectric. If desired, portions of housing  12  that have been separated from each other (e.g., by a through slot) may be joined by internal conductive structures (e.g., sheet metal or other metal members that bridge the slot). 
     Display  14  may include pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable pixel structures. A display cover layer such as a layer of clear glass or plastic may cover the surface of display  14  or the outermost layer of display  14  may be formed from a color filter layer, thin-film transistor layer, or other display layer. If desired, buttons may pass through openings in the cover layer. The cover layer may also have other openings such as an opening for speaker port  8 . 
     Housing  12  may include peripheral housing structures such as structures  16 . Structures  16  may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape with four edges, structures  16  may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges (as an example). Peripheral structures  16  or part of peripheral structures  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or that helps hold display  14  to device  10 ). Peripheral structures  16  may, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral housing structures  16  may be formed of a conductive material such as metal and may therefore sometimes be referred to as peripheral conductive housing structures, conductive housing structures, peripheral metal structures, peripheral conductive housing sidewall structures, peripheral conductive housing sidewalls, peripheral conductive sidewalls, or a peripheral conductive housing member (as examples). Peripheral conductive housing structures  16  may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, three, four, five, six, or more than six separate structures may be used in forming peripheral conductive housing structures  16 . 
     It is not necessary for peripheral conductive housing structures  16  to have a uniform cross-section. For example, the top portion of peripheral conductive housing structures  16  may, if desired, have an inwardly protruding lip that helps hold display  14  in place. The bottom portion of peripheral conductive housing structures  16  may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). Peripheral conductive 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 conductive housing structures  16  serve as a bezel for display  14 ), peripheral conductive housing structures  16  may run around the lip of housing  12  (i.e., peripheral conductive housing structures  16  may cover only the edge of housing  12  that surrounds display  14  and not the rest of the sidewalls of housing  12 ). 
     If desired, housing  12  may have a conductive rear surface or wall. For example, housing  12  may be formed from a metal such as stainless steel or aluminum. The rear surface of housing  12  may lie in a plane that is parallel to display  14 . In configurations for device  10  in which the rear surface of housing  12  is formed from metal, it may be desirable to form parts of peripheral conductive housing structures  16  as integral portions of the housing structures forming the rear surface of housing  12 . For example, a conductive rear housing wall of device  10  may be formed from a planar metal structure and portions of peripheral conductive 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 conductive rear wall of housing  12  may have one or more, two or more, or three or more portions. Peripheral conductive housing structures  16  and/or the conductive rear wall of housing  12  may form one or more exterior surfaces of device  10  (e.g., surfaces that are visible to a user of device  10 ) and/or may be implemented using internal structures that do not form exterior surfaces of device  10  (e.g., conductive housing structures that are not visible to a user of device  10  such as conductive structures that are covered with layers such as thin cosmetic layers, protective coatings, and/or other coating layers that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide structures  16  and/or the conductive rear wall of housing  12  from view of the user). 
     Display  14  may have an array of pixels that form an active area AA that displays images for a user of device  10 . An inactive border region such as inactive area IA may run along one or more of the peripheral edges of active area AA. 
     Display  14  may include conductive structures such as an array of capacitive electrodes for a touch sensor, conductive lines for addressing pixels, driver circuits, etc. Housing  12  may include internal conductive structures such as metal frame members and a planar conductive housing member (sometimes referred to as a backplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more metal parts that is welded or otherwise connected between opposing sides of member  16 ). The backplate may form an exterior rear surface of device  10  or may be covered by layers such as thin cosmetic layers, protective coatings, and/or other coatings that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide the backplate from view of the user. Device  10  may also include conductive structures such as printed circuit boards, components mounted on printed circuit boards, and other internal conductive structures. These conductive structures, which may be used in forming a ground plane in device  10 , may extend under active area AA of display  14 , for example. 
     In regions  22  and  20 , openings may be formed within the conductive structures of device  10  (e.g., between peripheral conductive housing structures  16  and opposing conductive ground structures such as conductive portions of the rear wall of housing  12 , conductive traces on a printed circuit board, conductive electrical components in display  14 , etc.). These openings, which may sometimes be referred to as gaps, may be filled with air, plastic, and/or other dielectrics and may be used in forming slot antenna resonating elements for one or more antennas in device  10 , if desired. 
     Conductive housing structures and other conductive structures in device  10  may serve as a ground plane for the antennas in device  10 . The openings in regions  20  and  22  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, may contribute to the performance of a parasitic antenna resonating element, or may otherwise serve as part of antenna structures formed in regions  20  and  22 . If desired, the ground plane that is under active area AA of display  14  and/or other metal structures in device  10  may have portions that extend into parts of the ends of device  10  (e.g., the ground may extend towards the dielectric-filled openings in regions  20  and  22 ), thereby narrowing the slots in regions  20  and  22 . 
     In general, device  10  may include any suitable number of antennas (e.g., one or more, two or more, three or more, four or more, etc.). The antennas in device  10  may be located at opposing first and second ends of an elongated device housing (e.g., at ends  20  and  22  of device  10  of  FIG. 1 ), along one or more edges of a device housing, in the center of a device housing, in other suitable locations, or in one or more of these locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral conductive 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 conductive 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 conductive housing structures  16  into one or more peripheral conductive segments. There may be, for example, two peripheral conductive segments in peripheral conductive housing structures  16  (e.g., in an arrangement with two of gaps  18 ), three peripheral conductive segments (e.g., in an arrangement with three of gaps  18 ), four peripheral conductive segments (e.g., in an arrangement with four of gaps  18 ), six peripheral conductive segments (e.g., in an arrangement with six 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 conductive housing structures  16  and may form antenna slots, gaps  18 , and other structures in device  10 . Polymer or other dielectric may fill these grooves and other housing openings. In some situations, housing openings that form antenna slots and other structure may be filled with a dielectric such as air. 
     In a typical scenario, device  10  may have one or more upper antennas and one or more lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, near-field 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  (sometimes referred to herein as control 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, control circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), 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, near-field communications (NFC) 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, 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  26  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  24 . Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications or communications in other wireless local area network (WLAN) bands and may handle the 2.4 GHz Bluetooth® communications band or other wireless personal area network (WPAN) bands. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in frequency ranges such as a cellular low band (LB) from 600 to 960 MHz, a cellular low-midband (LMB) from 1410 to 1510 MHz, a cellular midband (MB) from 1710 to 2170 MHz, a cellular high band (HB) from 2300 to 2700 MHz, a cellular ultra-high band (UHB) from 3400 to 3600 MHz, or other communications bands between 600 MHz and 4000 MHz or other suitable frequencies (as examples). 
     Circuitry  38  may handle voice data and non-voice data. Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include 60 GHz transceiver circuitry (e.g., millimeter wave 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  24  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. In Wi-Fi® 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  26  in wireless communications circuitry  34  may be coupled to antenna structures such as a given antenna  40  using paths such as path  50 . Wireless communications 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  40  with the ability to cover communications frequencies of interest, antenna  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  40  may be provided with adjustable circuits such as tunable components  42  to tune the antenna over communications bands of interest. Tunable components  42  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  42  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  56  that adjust inductance values, capacitance values, or other parameters associated with tunable components  42 , thereby tuning antenna  40  to cover desired communications bands. Antenna tuning components that are used to adjust the frequency response of antenna  40  such as tunable components  42  may sometimes be referred to herein as antenna tuning components, tuning components, antenna tuning elements, tuning elements, adjustable tuning components, adjustable tuning elements, or adjustable components. 
     Path  50  may include one or more transmission lines. As an example, path  50  of  FIG. 3  may be a transmission line having a positive signal conductor such as line  52  and a ground signal conductor such as line  54 . Path  50  may sometimes be referred to herein as transmission line  50  or radio-frequency transmission line  50 . Line  52  may sometimes be referred to herein as positive signal conductor  52 , signal conductor  52 , signal line conductor  52 , signal line  52 , positive signal line  52 , signal path  52 , or positive signal path  52  of transmission line  50 . Line  54  may sometimes be referred to herein as ground signal conductor  54 , ground conductor  54 , ground line conductor  54 , ground line  54 , ground signal line  54 , ground path  54 , or ground signal path  54  of transmission line  50 . 
     Transmission line  50  may, for example, include a coaxial cable transmission line (e.g., ground conductor  54  may be implemented as a grounded conductive braid surrounding signal conductor  52  along its length), a stripline transmission line, a microstrip transmission line, coaxial probes realized by a metalized via, an edge-coupled microstrip transmission line, an edge-coupled stripline transmission line, a waveguide structure (e.g., a coplanar waveguide or grounded coplanar waveguide), combinations of these types of transmission lines and/or other transmission line structures, etc. 
     Transmission lines in device  10  such as transmission line  50  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, transmission lines such as transmission line  50  may also include transmission line conductors (e.g., signal conductors  52  and ground conductors  54 ) integrated within multilayer laminated structures (e.g., layers of a conductive material such as copper and a dielectric material such as a resin that are laminated together without intervening adhesive). The multilayer laminated structures may, if desired, be folded or bent in multiple dimensions (e.g., two or three dimensions) and may maintain a bent or folded shape after bending (e.g., the multilayer laminated structures may be folded into a particular three-dimensional shape to route around other device components and may be rigid enough to hold its shape after folding without being held in place by stiffeners or other structures). All of the multiple layers of the laminated structures may be batch laminated together (e.g., in a single pressing process) without adhesive (e.g., as opposed to performing multiple pressing processes to laminate multiple layers together with adhesive). 
     A matching network (e.g., an adjustable matching network formed using tunable components  42 ) may include components such as inductors, resistors, and capacitors used in matching the impedance of antenna  40  to the impedance of transmission line  50 . 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  50  may be coupled to antenna feed structures associated with antenna  40 . As an example, antenna  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed  44  with a positive antenna feed terminal such as terminal  46  and a ground antenna feed terminal such as ground antenna feed terminal  48 . Signal conductor  52  may be coupled to positive antenna feed terminal  46  and ground conductor  54  may be coupled to ground antenna feed terminal  48 . Other types of antenna feed arrangements may be used if desired. For example, antenna  40  may be fed using multiple feeds each coupled to a respective port of transceiver circuitry  26  over a corresponding transmission line. If desired, signal conductor  52  may be coupled to multiple locations on antenna  40  (e.g., antenna  40  may include multiple positive antenna feed terminals coupled to signal conductor  52  of the same transmission line  50 ). Switches may be interposed on the signal conductor between transceiver circuitry  26  and the positive antenna feed terminals if desired (e.g., to selectively activate one or more positive antenna feed terminals at any given time). The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     Control circuitry  28  may use information from a proximity sensor, wireless performance metric data such as received signal strength information, device orientation information from an orientation sensor, device motion data from an accelerometer or other motion detecting sensor, information about a usage scenario of device  10 , information about whether audio is being played through speaker port  8  ( FIG. 1 ), information from one or more antenna impedance sensors, information on desired frequency bands to use for communications, and/or other information in determining when antenna  40  is being affected by the presence of nearby external objects or is otherwise in need of tuning. In response, control circuitry  28  may adjust an adjustable inductor, adjustable capacitor, switch, or other tunable components such as tunable components  42  to ensure that antenna  40  operates as desired. Adjustments to tunable components  42  may also be made to extend the frequency 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). 
     Antenna  40  may include resonating element structures (sometimes referred to herein as radiating element structures), antenna ground plane structures (sometimes referred to herein as ground plane structures, ground structures, or antenna ground structures), an antenna feed such as feed  44 , and other components (e.g., tunable components  42 ). Antenna  40  may be configured to form any suitable types of antenna. With one suitable arrangement, which is sometimes described herein as an example, antenna  40  is used to implement a hybrid inverted-F-slot antenna that includes both inverted-F and slot antenna resonating elements. 
     If desired, multiple antennas  40  may be formed in device  10 . Each antenna  40  may be coupled to transceiver circuitry such as transceiver circuitry  26  over respective transmission lines such as transmission line  50 . If desired, two or more antennas  40  may share the same transmission line  50 .  FIG. 4  is a diagram showing how device  10  may include multiple antennas  40  for performing wireless communications. 
     As shown in  FIG. 4 , device  10  may include two or more antennas  40  such as a first antenna  40 - 1 , a second antenna  40 - 2 , a third antenna  40 - 3 , and a fourth antenna  40 - 4 . Antennas  40  may be provided at different locations within housing  12  of device  10 . For example, antennas  40 - 1  and  40 - 2  may be formed within region  22  at a first (upper) end of housing  12  whereas antennas  40 - 3  and  40 - 4  are formed within region  20  at an opposing second (lower) end of housing  12 . In the example of  FIG. 3 , housing  12  has a rectangular periphery (e.g., a periphery having four corners) and each antenna  40  is formed at a respective corner of housing  12 . This example is merely illustrative and, in general, antennas  40  may be formed at any desired locations within housing  12 . 
     Wireless communications circuitry  34  may include input-output ports such as port  60  for interfacing with digital data circuits in control circuitry (e.g., storage and processing circuitry  28  of  FIG. 2 ). Wireless communications circuitry  34  may include baseband circuitry such as baseband (BB) processor  62  and radio-frequency transceiver circuitry such as transceiver circuitry  26 . 
     Port  60  may receive digital data from control circuitry that is to be transmitted by transceiver circuitry  26 . Incoming data that has been received by transceiver circuitry  26  and baseband processor  62  may be supplied to control circuitry via port  60 . 
     Transceiver circuitry  26  may include one or more transmitters and one or more receivers. For example, transceiver circuitry  26  may include multiple remote wireless transceivers  38  such as a first transceiver  38 - 1 , a second transceiver  38 - 2 , a third transceiver  38 - 3 , and a fourth transceiver  38 - 4  (e.g., transceiver circuits for handling voice and non-voice cellular telephone communications in cellular telephone communications bands). Each transceiver  38  may be coupled to a respective antenna  40  over a corresponding transmission line  50  (e.g., a first transmission line  50 - 1 , a second transmission line  50 - 2 , a third transmission line  50 - 3 , and a fourth transmission line  50 - 4 ). For example, first transceiver  38 - 1  may be coupled to antenna  40 - 1  over transmission line  50 - 1 , second transceiver  38 - 2  may be coupled to antenna  40 - 2  over transmission line  50 - 2 , third transceiver  38 - 3  may be coupled to antenna  40 - 3  over transmission line  50 - 3 , and fourth transceiver  38 - 4  may be coupled to antenna  40 - 4  over transmission line  50 - 4 . 
     Radio-frequency front end circuits  58  may be interposed on each transmission line  50  (e.g., a first front end circuit  58 - 1  may be interposed on transmission line  50 - 1 , a second front end circuit  58 - 2  may be interposed on transmission line  50 - 2 , a third front end circuit  58 - 3  may be interposed on transmission line  50 - 3 , etc.). Front end circuits  58  may each include switching circuitry, filter circuitry (e.g., duplexer and/or diplexer circuitry, notch filter circuitry, low pass filter circuitry, high pass filter circuitry, bandpass filter circuitry, etc.), impedance matching circuitry for matching the impedance of transmission lines  50  to the corresponding antenna  40 , networks of active and/or passive components such as tunable components  42  of  FIG. 3 , radio-frequency coupler circuitry for gathering antenna impedance measurements, amplifier circuitry (e.g., low noise amplifiers and/or power amplifiers) or any other desired radio-frequency circuitry. If desired, front end circuits  58  may include switching circuitry that is configured to selectively couple antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  to different respective transceivers  38 - 1 ,  38 - 2 ,  38 - 3 , and  38 - 4  (e.g., so that each antenna can handle communications for different transceivers  38  over time based on the state of the switching circuits in front end circuits  58 ). 
     If desired, front end circuits  58  may include filtering circuitry (e.g., duplexers and/or diplexers) that allow the corresponding antenna  40  to transmit and receive radio-frequency signals at the same time (e.g., using a frequency domain duplexing (FDD) scheme). Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may transmit and/or receive radio-frequency signals in respective time slots or two or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may transmit and/or receive radio-frequency signals concurrently. In general, any desired combination of transceivers  38 - 1 ,  38 - 2 ,  38 - 3 , and  38 - 4  may transmit and/or receive radio-frequency signals using the corresponding antenna  40  at a given time. In one suitable arrangement, each of transceivers  38 - 1 ,  38 - 2 ,  38 - 3 , and  38 - 4  may receive radio-frequency signals while a given one of transceivers  38 - 1 ,  38 - 2 ,  38 - 3 , and  38 - 4  transmits radio-frequency signals at a given time. 
     Amplifier circuitry such as one or more power amplifiers may be interposed on transmission lines  50  and/or formed within transceiver circuitry  26  for amplifying radio-frequency signals output by transceivers  38  prior to transmission over antennas  40 . Amplifier circuitry such as one or more low noise amplifiers may be interposed on transmission lines  50  and/or formed within transceiver circuitry  26  for amplifying radio-frequency signals received by antennas  40  prior to conveying the received signals to transceivers  38 . 
     In the example of  FIG. 4 , separate front end circuits  58  are formed on each transmission line  50 . This is merely illustrative. If desired, two or more transmission lines  50  may share the same front end circuits  58  (e.g., front end circuits  58  may be formed on the same substrate, module, or integrated circuit). 
     Each of transceivers  38  may, for example, include circuitry for converting baseband signals received from baseband processor  62  over paths  63  into corresponding radio-frequency signals. For example, transceivers  38  may each include mixer circuitry for up-converting the baseband signals to radio-frequencies prior to transmission over antennas  40 . Transceivers  38  may include digital to analog converter (DAC) and/or analog to digital converter (ADC) circuitry for converting signals between digital and analog domains. Each of transceivers  38  may include circuitry for converting radio-frequency signals received from antennas  40  over transmission lines  50  into corresponding baseband signals. For example, transceivers  38  may each include mixer circuitry for down-converting the radio-frequency signals to baseband frequencies prior to conveying the baseband signals to baseband processor  62  over paths  63 . 
     Each transceiver  38  may be formed on the same substrate, integrated circuit, or module (e.g., transceiver circuitry  26  may be a transceiver module having a substrate or integrated circuit on which each of transceivers  38  are formed) or two or more transceivers  38  may be formed on separate substrates, integrated circuits, or modules. Baseband processor  62  and front end circuits  58  may be formed on the same substrate, integrated circuit, or module as transceivers  38  or may be formed on separate substrates, integrated circuits, or modules from transceivers  38 . In another suitable arrangement, transceiver circuitry  26  may include a single transceiver  38  having four ports, each of which is coupled to a respective transmission line  50 , if desired. Each transceiver  38  may include transmitter and receiver circuitry for both transmitting and receiving radio-frequency signals. In another suitable arrangement, one or more transceivers  38  may perform only signal transmission or signal reception (e.g., one or more of circuits  38  may be a dedicated transmitter or dedicated receiver). 
     In the example of  FIG. 4 , antennas  40 - 1  and  40 - 4  may occupy a larger space (e.g., a larger area or volume within device  10 ) than antennas  40 - 2  and  40 - 3 . This may allow antennas  40 - 1  and  40 - 4  to support communications at longer wavelengths (i.e., lower frequencies) than antennas  40 - 2  and  40 - 3 . This is merely illustrative and, if desired, each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may occupy the same volume or may occupy different volumes. Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may be configured to convey radio-frequency signals in at least one common frequency band. If desired, one or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may handle radio-frequency signals in at least one frequency band that is not covered by one or more of the other antennas in device  10 . 
     If desired, each antenna  40  and each transceiver  38  may handle radio-frequency communications in multiple frequency bands (e.g., multiple cellular telephone communications bands). For example, transceiver  38 - 1 , antenna  40 - 1 , transceiver  38 - 4 , and antenna  40 - 4 , may handle radio-frequency signals in a first frequency band such as a cellular low band between 600 and 960 MHz, a second frequency band such as a cellular low-midband between 1410 and 1510 MHz, a third frequency band such as a cellular midband between 1700 and 2200 MHz, a fourth frequency band such as a cellular high band between 2300 and 2700 MHz, and/or a fifth frequency band such as a cellular ultra-high band between 3400 and 3600 MHz. Transceiver  38 - 2 , antenna  40 - 2 , transceiver  38 - 3 , and antenna  40 - 3  may handle radio-frequency signals in some or all of these bands (e.g., in scenarios where the volume of antennas  40 - 3  and  40 - 2  is large enough to support frequencies in the low band). 
     The example of  FIG. 4  is merely illustrative. In general, antennas  40  may cover any desired frequency bands. Transceiver circuitry  26  may include other transceiver circuits such as one or more circuits  36  or  24  of  FIG. 2  coupled to one or more antennas  40 . Housing  12  may have any desired shape. Antennas  40  may be formed at any desired locations within housing  12 . Forming each of antennas  40 - 1  through  40 - 4  at different corners of housing  12  may, for example, maximize the multi-path propagation of wireless data conveyed by antennas  40  to optimize overall data throughput for wireless communications circuitry  34 . 
     When operating using a single antenna  40 , a single stream of wireless data may be conveyed between device  10  and external communications equipment (e.g., one or more other wireless devices such as wireless base stations, access points, cellular telephones, computers, etc.). This may impose an upper limit on the data rate (data throughput) obtainable by wireless communications circuitry  34  in communicating with the external communications equipment. As software applications and other device operations increase in complexity over time, the amount of data that needs to be conveyed between device  10  and the external communications equipment typically increases, such that a single antenna  40  may not be capable of providing sufficient data throughput for handling the desired device operations. 
     In order to increase the overall data throughput of wireless communications circuitry  34 , multiple antennas  40  may be operated using a multiple-input and multiple-output (MIMO) scheme. When operating using a MIMO scheme, two or more antennas  40  on device  10  may be used to convey multiple independent streams of wireless data at the same frequency. This may significantly increase the overall data throughput between device  10  and the external communications equipment relative to scenarios where only a single antenna  40  is used. In general, the greater the number of antennas  40  that are used for conveying wireless data under the MIMO scheme, the greater the overall throughput of wireless communications circuitry  34 . 
     In order to perform wireless communications under a MIMO scheme, antennas  40  need to convey data at the same frequencies. If desired, wireless communications circuitry  34  may perform so-called two-stream (2×) MIMO operations (sometimes referred to herein as 2× MIMO communications or communications using a 2× MIMO scheme) in which two antennas  40  are used to convey two independent streams of radio-frequency signals at the same frequency. Wireless communications circuitry  34  may perform so-called four-stream (4×) MIMO operations (sometimes referred to herein as 4× MIMO communications or communications using a 4× MIMO scheme) in which four antennas  40  are used to convey four independent streams of radio-frequency signals at the same frequency. Performing 4× MIMO operations may support higher overall data throughput than 2× MIMO operations because 4× MIMO operations involve four independent wireless data streams whereas 2× MIMO operations involve only two independent wireless data streams. If desired, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 2× MIMO operations in some frequency bands and may perform 4× MIMO operations in other frequency bands (e.g., depending on which bands are handled by which antennas). Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 2× MIMO operations in some bands concurrently with performing 4× MIMO operations in other bands, for example. 
     As one example, antennas  40 - 1  and  40 - 4  (and the corresponding transceivers  38 - 1  and  38 - 4 ) may perform 2× MIMO operations by conveying radio-frequency signals at the same frequency in a cellular low band between 600 MHz and 960 MHz. At the same time, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may collectively perform 4× MIMO operations by conveying radio-frequency signals at the same frequency in a cellular midband between 1700 and 2200 MHz and/or at the same frequency in a cellular high band (HB) between 2300 and 2700 MHz (e.g., antennas  40 - 1  and  40 - 4  may perform 2× MIMO operations in the low band concurrently with performing 4× MIMO operations in the midband and/or high band). This example is merely illustrative and, in general, any desired number of antennas may be used to perform any desired MIMO operations in any desired frequency bands. 
     If desired, antennas  40 - 1  and  40 - 2  may include switching circuitry that is adjusted by control circuitry (e.g., control circuitry  28  of  FIG. 3 ). Control circuitry  28  may control the switching circuitry in antennas  40 - 1  and  40 - 2  to configure antenna structures in antennas  40 - 1  and  40 - 2  to form a single antenna  40 U in region  22  of device  10 . Similarly, antennas  40 - 3  and  40 - 4  may include switching circuitry that is adjusted by control circuitry  28 . Control circuitry  28  may control the switching circuitry in antennas  40 - 3  and  40 - 4  to form a single antenna  40 L (e.g., an antenna  40 L that includes antenna structures from antennas  40 - 3  and  40 - 4 ) in region  20  of device  10 . Antenna  40 U may, for example, be formed at an upper end of housing  12  and may therefore sometimes be referred to herein as upper antenna  40 U. Antenna  40 L may be formed at an opposing lower end of housing  12  and may therefore sometimes be referred to herein as lower antenna  40 L. When antennas  40 - 1  and  40 - 2  are configured to form upper antenna  40 U and antennas  40 - 3  and  40 - 4  are configured to form lower antenna  40 L, wireless communications circuitry  34  may perform 2× MIMO operations using antennas  40 U and  40 L in any desired frequency bands. If desired, control circuitry  28  may toggle the switching circuitry over time to switch wireless communications circuitry  34  between a first mode in which antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  perform 2× MIMO operations in any desired frequency bands and 4× MIMO operations in any desired frequency bands and a second mode in which antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  are configured to form antennas  40 U and  40 L that perform 2× MIMO operations in any desired frequency bands. 
     If desired, wireless communications circuitry  34  may convey wireless data with multiple antennas on one or more external devices (e.g., multiple wireless base stations) in a scheme sometimes referred to as carrier aggregation. When operating using a carrier aggregation scheme, the same antenna  40  may convey radio-frequency signals with multiple antennas (e.g., antennas on different wireless base stations) at different respective frequencies (sometimes referred to herein as carrier frequencies, channels, carrier channels, or carriers). For example, antenna  40 - 1  may receive radio-frequency signals from a first wireless base station at a first frequency, from a second wireless base station at a second frequency, and a from a third base station at a third frequency. The received signals at different frequencies may be simultaneously processed (e.g., by transceiver  38 - 1 ) to increase the communications bandwidth of transceiver  38 - 1 , thereby increasing the data rate of transceiver  38 - 1 . Similarly, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform carrier aggregation at two, three, or more than three frequencies within any desired frequency bands. This may serve to further increase the overall data throughput of wireless communications circuitry  34  relative to scenarios where no carrier aggregation is performed. For example, the data throughput of circuitry  34  may increase for each carrier frequency that is used (e.g., for each wireless base station that communicates with each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 ). 
     By performing communications using both a MIMO scheme and a carrier aggregation scheme, the data throughput of wireless communications circuitry  34  may be even greater than in scenarios where either a MIMO scheme or a carrier aggregation scheme is used. The data throughput of circuitry  34  may, for example, increase for each carrier frequency that is used by antennas  40  (e.g., each carrier frequency may contribute 40 megabits per second (Mb/s) or some other throughput to the total throughput of wireless communications circuitry  34 ). As one example, antennas  40 - 1  and  40 - 4  may perform carrier aggregation across three frequencies within each of the cellular low band, midband, and high band and antennas  40 - 3  and  40 - 4  may perform carrier aggregation across three frequencies within each of the cellular midband and high band. At the same time, antennas  40 - 1  and  40 - 4  may perform 2× MIMO operations in the cellular low band and antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 4× MIMO operations in one of cellular midband and the cellular high band. In this scenario, with an exemplary throughput of 40 Mb/s per carrier frequency, wireless communications circuitry  34  may exhibit a throughput of approximately 960 Mb/s. If 4× MIMO operations are performed in both the cellular midband and the cellular high band by antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 , wireless communications circuitry  34  may exhibit an even greater throughput of approximately 1200 Mb/s. In other words, the data throughput of wireless communications circuitry  34  may be increased from the 40 Mb/s associated with conveying signals at a single frequency with a single antenna to approximately 1 gigabits per second (Gb/s) by performing communications using MIMO and carrier aggregation schemes using four antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 . 
     These examples are merely illustrative and, if desired, carrier aggregation may be performed in fewer than three carriers per band, may be performed across different bands, or may be omitted for one or more of antennas  40 - 1  through  40 - 4 . The example of  FIG. 4  is merely illustrative. If desired, antennas  40  may cover any desired number of frequency bands at any desired frequencies. More than four antennas  40  or fewer than four antennas  40  may perform MIMO and/or carrier aggregation operations at non-near-field communications frequencies if desired. 
     Antennas  40  may include slot antenna structures, inverted-F antenna structures (e.g., planar and non-planar inverted-F antenna structures), loop antenna structures, combinations of these, or other antenna structures. An illustrative inverted-F antenna structure is shown in  FIG. 5 . 
     When using an inverted-F antenna structure as shown in  FIG. 5 , antenna  40  may include an antenna resonating element  64  (sometimes referred to herein as antenna radiating element  64 ) and antenna ground  74  (sometimes referred to herein as ground plane  74  or ground  74 ). Antenna resonating element  64  may have a main resonating element arm such as resonating element arm  66 . The length of resonating element arm  66  may be selected so that antenna  40  resonates at desired operating frequencies. For example, the length of resonating element arm  66  (or a branch of resonating element arm  66 ) may be approximately one-quarter of the wavelength corresponding to a desired operating frequency for antenna  40 . Antenna  40  may also exhibit resonances at harmonic frequencies. If desired, slot antenna structures or other antenna structures may be incorporated into an inverted-F antenna such as antenna  40  of  FIG. 5  (e.g., to enhance antenna response in one or more communications bands). 
     Resonating element arm  66  may be coupled to antenna ground  74  by return path  68 . Antenna feed  44  may include positive antenna feed terminal  46  and ground antenna feed terminal  48  and may run parallel to return path  68  between resonating element arm  66  and antenna ground  74 . If desired, antenna  40  may have more than one resonating element 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, resonating element arm  66  may have left and right branches that extend outwardly from antenna feed  44  and return path  68 . If desired, multiple feeds may be used to feed antennas such as antenna  40 . Resonating element arm  66  may follow any desired path having any desired shape (e.g., curved and/or straight paths, meandering paths, etc.). 
     If desired, antenna  40  may include one or more adjustable circuits (e.g., tunable components  42  of  FIG. 3 ) that are coupled to resonating element arm  66 . As shown in  FIG. 5 , for example, tunable components such as adjustable inductor  70  may be coupled between antenna resonating element structures in antenna  40  such as resonating element arm  66  and antenna ground  74  (i.e., adjustable inductor  70  may bridge the gap between resonating element arm  66  and antenna ground  74 ). Adjustable inductor  70  may exhibit an inductance value that is adjusted in response to control signals  72  provided to adjustable inductor  70  from control circuitry  28  ( FIG. 3 ). 
     Antenna  40  may be a hybrid antenna that includes one or more slot elements. As shown in  FIG. 6 , for example, antenna  40  may be based on a slot antenna configuration having an opening such as slot  76  that is formed within conductive structures such as antenna ground  74 . Slot  76  may be filled with air, plastic, and/or other dielectric. The shape of slot  76  may be straight or may have one or more bends (i.e., slot  76  may have an elongated shape following a meandering path). Feed terminals  48  and  46  may, for example, be located on opposing sides of slot  76  (e.g., on opposing long sides). Slot  76  may sometimes be referred to herein as slot element  76 , slot antenna resonating element  76 , slot antenna radiating element  76 , or slot radiating element  76 . Slot-based radiating elements such as slot  76  of  FIG. 6  may give rise to an antenna resonance at frequencies in which the wavelength of the antenna signals is approximately equal to the perimeter of the slot. In narrow slots, the resonant frequency of slot  76  is associated with signal frequencies at which the slot length is approximately equal to a half of a wavelength of operation. 
     The frequency response of antenna  40  can be tuned using one or more tuning components (e.g., tunable components  42  of  FIG. 3 ). These components may have terminals that are coupled to opposing sides of slot  76  (i.e., the tunable components may bridge slot  76 ). If desired, tunable components may have terminals that are coupled to respective locations along the length of one of the sides of slot  76 . Combinations of these arrangements may also be used. If desired, antenna  40  may be a hybrid slot-inverted-F antenna that includes resonating elements of the type shown in both  FIG. 5  and  FIG. 6  (e.g., having resonances given by both a resonating element arm such as resonating element arm  66  of  FIG. 5  and a slot such as slot  76  of  FIG. 6 ). 
     The example of  FIG. 6  is merely illustrative. In general, slot  76  may have any desired shape (e.g., shapes with straight and/or curved edges), may follow a meandering path, etc. If desired, slot  76  may be an open slot having one or more ends that are free from conductive material (e.g., where slot  76  extends through one or more sides of antenna ground  74 ). Slot  76  may, for example, have a length approximately equal to one-quarter of the wavelength of operation in these scenarios. 
     A top interior view of an illustrative portion of device  10  that contains antennas  40 - 4  and  40 - 3  of  FIG. 4  is shown in  FIG. 7 . In the example of  FIG. 7 , antennas  40 - 3  and  40 - 4  are each formed using hybrid slot-inverted-F antenna structures that includes resonating elements of the types shown in  FIGS. 5 and 6 . 
     As shown in  FIG. 7 , peripheral conductive housing structures  16  may be segmented (divided) by dielectric-filled gaps  18  (e.g., plastic gaps) such as a first gap  18 - 1 , a second gap  18 - 2 , and a third gap  18 - 3 . Each of gaps  18 - 1 ,  18 - 2 , and  18 - 3  may be formed within peripheral structures  16  along respective sides of device  10 . For example, gap  18 - 1  may be formed at a first side of device  10  and may separate a first segment  16 - 1  of peripheral conductive housing structures  16  from a second segment  16 - 2  of peripheral conductive housing structures  16 . Gap  18 - 3  may be formed at a second side of device  10  and may separate second segment  16 - 2  from a third segment  16 - 3  of peripheral conductive housing structures  16 . Gap  18 - 2  may be formed at a third side of device  10  and may separate third segment  16 - 3  from a fourth segment of peripheral conductive housing structures  16 . 
     The resonating element for antenna  40 - 4  may include an inverted-F antenna resonating element arm (e.g., resonating element arm  66  of  FIG. 5 ) that is formed from segment  16 - 3 . The resonating element for antenna  40 - 3  may include an inverted-F antenna resonating element arm that is formed from segment  16 - 2 . Air and/or other dielectric may fill slot  76  between arm segments  16 - 2  and  16 - 3  and ground structures  78 . 
     Ground structures  78  may include one or more planar metal layers such as a metal layer used to form a rear housing wall for device  10 , a metal layer that forms an internal support structure for device  10 , conductive traces on a printed circuit board, and/or any other desired conductive layers in device  10 . Ground structures  78  may extend from segment  16 - 1  to segment  16 - 4  of peripheral conductive housing structures  16 . Ground structures  78  may be coupled to segments  16 - 1  and  16 - 4  using conductive adhesive, solder, welds, conductive screws, conductive pins, and/or any other desired conductive interconnect structures. If desired, ground structures  78  and segments  16 - 1  and  16 - 4  may be formed from different portions of a single integral conductive structure (e.g., a conductive housing for device  10 ). 
     Ground structures  78  need not be confined to a single plane and may, if desired, include multiple layers located in different planes or non-planar structures. Ground structures  78  may include conductive (e.g., grounded) portions of other electrical components within device  10 . For example, ground structures  78  may include conductive portions of display  14  ( FIG. 1 ). Conductive portions of display  14  may include a metal frame for display  14 , a metal backplate for display  14 , shielding layers or shielding cans for display  14 , pixel circuitry in display  14 , touch sensor circuitry (e.g., touch sensor electrodes) for display  14 , and/or any other desired conductive structures in display  14  or used for mounting display  14  to the housing for device  10 . 
     Ground structures  78  and segments  16 - 1  and  16 - 4  may form portions of antenna ground  74  ( FIGS. 5 and 6 ) for antennas  40 - 3  and  40 - 40 . If desired, slot  76  may be configured to form slot antenna resonating element structures that contribute to the overall performance of antennas  40 - 3  and/or  40 - 4 . Slot  76  may extend from gap  18 - 1  to gap  18 - 2  (e.g., the ends of slot  76  which may sometimes be referred to as open ends, may be formed by gaps  18 - 1  and  18 - 2 ). Slot  76  may have an elongated shape having any suitable length (e.g., 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 10 cm, etc.) and any suitable width (e.g., approximately 2 mm, less than 2 mm, less than 3 mm, less than 4 mm, 1-3 mm, etc.). Gap  18 - 3  may be continuous with and extend perpendicular to a portion of slot  76  along the longitudinal axis of the longest portion of slot  76  (e.g., the portion of slot  76  extending parallel to the X-axis of  FIG. 7 ). If desired, slot  76  may include vertical portions that extend parallel to longitudinal axis  82  (e.g., the Y-axis of  FIG. 7 ) and beyond gaps  18 - 1  and  18 - 2 . 
     As shown in  FIG. 7 , a portion  80  of ground structures  78  may protrude into slot  76  towards segment  16 - 3 . Portion  80  of ground structures  78  (sometimes referred to herein as protrusion  80 , ground protrusion  80 , extension  80 , or ground extension  80 ) may be located closer to segment  16 - 3  than other portions of ground structures  78  (e.g., ground extension  80  may extend parallel to longitudinal axis  82  towards segment  16 - 3 ). Ground extension  80  may, for example, support components for display  14  of  FIG. 1  (e.g., components that allow active area AA of display  14  to extend across substantially all of the front face of device  10 ). If desired, ground extension  80  may form a distributed capacitance with segment  16 - 3  that tunes the frequency response of antenna  40 - 4 . 
     Slot  76  may be filled with dielectric such as air, plastic, ceramic, or glass. For example, plastic may be inserted into portions of slot  76  and this plastic may be flush with the exterior of the housing for device  10 . Dielectric material in slot  76  may lie flush with dielectric material in gaps  18 - 1 ,  18 - 2 , and  18 - 3  at the exterior of the housing  12  if desired. The example of  FIG. 7  in which slot  76  has a U-shape is merely illustrative. If desired, slot  76  may have any other desired shapes (e.g., a rectangular shape, meandering shapes having curved and/or straight edges, etc.). 
     In general, it may be desirable to support multiple frequency bands using antenna  40 - 4  (e.g., using a MIMO scheme with the other antennas in device  10  to maximize the data rate for wireless communications circuitry  34  of  FIG. 2 ). For example, antenna  40 - 4  may support communications in a cellular low band, a cellular low-midband, a cellular high band, and/or a cellular ultra-high band. In order to support operations at multiple frequency bands with satisfactory antenna efficiency, antenna  40 - 4  may be provided with multiple positive antenna feed terminals such as positive antenna feed terminal  46  of  FIGS. 3, 5, and 6 . The positive antenna feed terminals may be located at different points along segment  16 - 3 , for example. 
     In some scenarios, each positive antenna feed terminal is coupled to a different respective radio-frequency transmission line (e.g., multiple radio-frequency transmission lines such as transmission line  50  of  FIG. 3  may be used to feed antenna  40 - 4 ). In these scenarios, switching circuitry is used to selectively couple the transmission lines to transceiver circuitry  26  ( FIG. 4 ) as needed. However, in practice, feeding antenna  40 - 4  using different transmission lines for each positive antenna feed terminal and the corresponding switching circuitry can introduce undesirable losses and attenuation to the radio-frequency signals. These losses can limit the antenna efficiency for antenna  40 - 4  across one or more frequency bands of interest. In addition, if care is not taken, the presence of ground extension  80  or other conductive display structures (e.g., conductive structures that maximize active area AA for display  14  of  FIG. 1 ) can limit the antenna efficiency for antenna  40 - 4  at relatively low frequencies such as frequencies in a cellular low band. It would therefore be desirable to be able to provide antenna  40 - 4  with satisfactory antenna efficiency across each frequency band of interest. 
       FIG. 8  is a top interior view of an illustrative portion of device  10  that contains antenna  40 - 4 . Antenna  40 - 4  of  FIG. 8  may, for example, support wireless communications with satisfactory antenna efficiency across multiple frequency bands of interest. 
     As shown in  FIG. 8 , antenna  40 - 4  may be formed at a corner of device  10  and may include an antenna resonating element arm  66  formed from segment  16 - 3  of peripheral conductive structures  16 . Antenna  40 - 4  may be fed using transmission line  50 - 4 . Transmission line  50 - 4  may include ground conductor  54  and signal conductor  52 . In one suitable example, transmission line  50 - 4  is a coaxial cable having a conductive outer braid that forms ground conductor  54  and having a signal conductor  52  that is surrounded by the conductive outer braid. This is merely illustrative and, in general, any desired transmission line structures having signal conductor  52  and ground conductor  54  may be used. 
     Transmission line  50 - 4  may be coupled to an antenna feed for antenna  40 - 4  (e.g., antenna feed  44  of  FIGS. 3, 5, and 6 ). The antenna feed may include ground antenna feed terminal  48  coupled to ground structures  78  at the edge of slot  76 . Ground antenna feed terminal  48  may be coupled to ground conductor  54  of transmission line  50 - 4 . The antenna feed may include multiple positive antenna feed terminals  46  coupled to peripheral conductive housing structures  16  that help to support communications across multiple frequency bands. 
     In the example of  FIG. 8 , antenna  40 - 4  includes a first positive antenna feed terminal  46 A, a second positive antenna feed terminal  46 B, and a third positive antenna feed terminal  46 C. Positive antenna feed terminals  46 A and  46 B may be coupled to segment  16 - 3  of peripheral conductive housing structures  16  (e.g., antenna resonating element arm  66 ). Positive antenna feed terminal  46 C may be coupled to segment  16 - 4  of peripheral conductive housing structures  16 . 
     Ground structures  78  may have any desired shape within device  10 . For example, the lower edge of ground structures  78  (e.g., the edge of ground structures  78  defining the upper edge of slot  76 ) may be aligned with gap  18 - 2  in peripheral conductive housing structures  16  (e.g., upper edge  112  or lower edge  110  of gap  18 - 2  may be aligned with the edge of ground structures  78  defining the portion of slot  76  adjacent to gap  18 - 2 ). If desired, as shown in the example of  FIG. 8 , ground structures  78  may include a slot such as vertical slot  120  adjacent to gap  18 - 2  that extends above upper edge  112  of gap  18 - 2  (e.g., in the direction of the Y-axis of  FIG. 7 ). Vertical slot  120  may, for example, have two or more edges that are defined by ground structures  78  and one edge that is defined by segment  16 - 4  of peripheral conductive housing structures  16 . Vertical slot  120  may have an open end defined by an open end of slot  76  at gap  18 - 2  and an opposing closed end  118  defined by ground structures  78 . Vertical slot  120  may therefore sometimes be referred to herein as a continuous portion of slot  76 , a vertical portion of slot  76 , or a vertical extension of slot  76 . 
     Vertical slot  120  may have a width  116  that separates ground structures  78  from segment  16 - 4  of peripheral conductive structures  16  (e.g., in the direction of the X-axis of  FIG. 8 ). Because segment  16 - 4  is shorted to ground structures  78  (and thus forms part of the antenna ground for antenna  40 - 4 ), vertical slot  120  may effectively form an open slot having three sides defined by the antenna ground for antenna  40 - 4 . 
     Vertical slot  120  may have any desired width  116  (e.g., about 2 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, more than 0.5 mm, more than 1.5 mm, more than 2.5 mm, 1-3 mm, etc.). Vertical slot  120  may have an elongated length  114  (e.g., perpendicular to width  116 ). Length  114  may be, for example, 10-15 mm, more than 5 mm, more than 10 mm, more than 15 mm, more than 30 mm, less than 30 mm, less than 20 mm, less than 15 mm, less than 10 mm, between 5 and 20 mm, etc. 
     Portions of vertical slot  120  may contribute slot antenna resonances to antenna  40 - 4  in one or more frequency bands if desired. For example, length  114  and width  116  of vertical slot  120  (e.g., the perimeter of vertical slot  120  shown by dashed path  122 ) may be selected so that antenna  40 - 4  resonates at desired operating frequencies. If desired, the overall length of slots  76  and  120  may be selected so that antenna  40 - 4  resonates at desired operating frequencies. 
     Antenna  40 - 4  may include adjustable components  102  (e.g., tunable components  42  of  FIG. 3 ) such as a first adjustable component  102 A, a second adjustable component  102 B, a third adjustable component  102 C, a fourth adjustable component  102 D, and a fifth adjustable component  102 E coupled across slot  76 . Return paths for antenna  40 - 4  such as return path  68  of  FIG. 5  may be formed by adjustable components  102 A,  102 B, and/or  102 D. 
     Adjustable components  102  may include switches coupled to fixed components such as inductors for providing adjustable amounts of inductance, a short circuit path, and/or an open circuit between peripheral conductive housing structures  16  and ground structures  78 . If desired, adjustable components  102  may also or alternatively include fixed components that are not coupled to switches or a combination of components that are coupled to switches and components that are not coupled to switches. These examples are merely illustrative and, in general, components  102  may include other components such as adjustable return path switches, switches coupled to capacitors, or any other desired components. 
     In the example of  FIG. 8 , adjustable component  102 A may bridge slot  76  at a first location along slot  76  (e.g., component  102 A may be coupled between terminal  132  on ground structures  78  and terminal  134  on segment  16 - 3 ). Adjustable component  102 C may be interposed on signal conductor  52 . 
     Adjustable component  102 D may bridge slot  76  and may be a three terminal component having a first terminal  104 , a second terminal  108 , and a third terminal  124 . First terminal  104  of adjustable component  102 D may be interposed on signal conductor  52  between adjustable component  102 C and positive antenna feed terminal  46 B. Second terminal  108  may be coupled to segment  16 - 3  at a location that is interposed between positive antenna feed terminal  46 B and gap  18 - 2 . Third terminal  124  may be coupled to ground structures  78 . Third terminal  124  may be interposed between ground antenna feed terminal  48  and gap  18 - 2  on ground structures  78 . If desired, third terminal  124  may be located along an edge of vertical slot  120 . 
     Signal conductor  52  may be coupled to positive antenna feed terminal  46 C over path  106 . Path  106  may be coupled to positive antenna feed terminal  46 B or at any other desired location between terminal  104  of adjustable component  102 D and positive antenna feed terminal  46 B. Adjustable component  102 E may be interposed on path  106  between positive antenna feed terminal  46 B and positive antenna feed terminal  46 C. 
     Adjustable component  102 B may bridge slot  76  between terminal  126  on ground structures  78  and positive antenna feed terminal  46 A. Positive antenna feed terminal  46 A may be interposed on segment  16 - 3  between terminal  134  and positive antenna feed terminal  46 B. Terminal  134  may be interposed on segment  16 - 3  between gap  18 - 3  and positive antenna feed terminal  46 A. Terminal  126  may be interposed on ground structures  78  between terminal  132  and ground antenna feed terminal  48 . Path  128  may couple adjustable component  102 B to positive antenna feed terminal  46 A. A node on path  128  such as node  130  may be coupled to node  100  on signal conductor  52  through a conductive structure such as conductive trace  90 . Node  100  may be interposed on signal conductor  52  between adjustable component  102 C and transceiver circuitry  26  ( FIG. 4 ). 
     The length of resonating element arm  66  (and the perimeter of vertical slot  120 ) may be selected so that antenna  40 - 4  radiates at desired operating frequencies such as frequencies in a cellular low band (e.g., a frequency band between about 600 MHz and 960 MHz), a cellular low-midband (e.g., a frequency band between about 1410 MHz and 1510 MHz), a cellular midband (e.g., a frequency band between about 1710 MHz and 2170 MHz), and/or a cellular ultra-high band (e.g., a frequency band between about 3400 MHz and 3600 MHz). 
     Positive antenna feed terminals  46 A and/or  46 B may be used to convey radio-frequency signals in the cellular low band as well as signals at frequencies higher than the cellular low band. For example, the length of resonating element arm  66  extending from positive antenna feed terminal  46 B to gap  18 - 2  may be selected to cover frequencies in the cellular low-midband and/or the cellular midband. This length may be approximately equal to one-quarter of the wavelength corresponding to a frequency in the cellular midband (e.g., where the wavelength is an effective wavelength that accounts for dielectric loading by the dielectric materials in slot  76 ). The response of antenna  40 - 4  in the cellular low-midband and the cellular midband may be supported by a fundamental mode of this length. The response of antenna  40 - 4  in the cellular ultra-high band may be supported by a harmonic mode of this length. 
     Segment  16 - 4  of peripheral conductive housing structures  16  may contribute to the frequency response of antenna  40 - 4  in the cellular high band. For example, lower edge  110  of gap  18 - 2  (e.g., the end of resonating element arm  66  at gap  18 - 2 ) may indirectly feed segment  16 - 4  via near-field electromagnetic coupling (e.g., across gap  18 - 2 ). Antenna currents on resonating element arm  16 - 3  may induce corresponding antenna currents on segment  16 - 4  via the near-field electromagnetic coupling. 
     Length  114  may be selected to support a frequency response for antenna  40 - 4  in the cellular high band (e.g., length  114  may be approximately one-quarter of the effective wavelength corresponding to a frequency within the cellular high band). When segment  16 - 4  is indirectly fed in this way, segment  16 - 4  may form a parasitic antenna resonating element for antenna  40 - 4  (e.g., a radiating element that is not directly fed using signal conductor  52 ). Adjustable component  102 E may be configured to form an open circuit between signal conductor  52  (positive antenna feed terminal  46 B) and positive antenna feed terminal  46 C when segment  16 - 4  is indirectly fed via near-field electromagnetic coupling. 
     In practice, indirectly feeding segment  16 - 4  may allow antenna  40 - 4  to cover some but not all of the cellular high band with satisfactory antenna efficiency. If desired, the frequency response of antenna  40 - 4  in the cellular high band may be optimized by directly feeding vertical slot  120 . In order to directly feed vertical slot  120 , antenna currents conveyed over signal conductor  52  may be directly fed to vertical slot  120  (e.g., over positive antenna feed terminal  46 C and path  106 ) and may flow around the perimeter of vertical slot  120  (as shown by dashed path  122 ). Adjustable component  102 E may be configured to form a short circuit path or another non-open-circuit impedance between signal conductor  52  (positive antenna feed terminal  46 B) and positive antenna feed terminal  46 C when vertical slot  120  is directly fed. In this way, path  106  may form a branch of signal conductor  52  and antenna  40 - 4  may be concurrently fed using both positive antenna feed terminals  46 B and  46 C (e.g., on opposing sides of gap  18 - 2 ). 
     Antenna currents flowing along path  122  may contribute a slot antenna resonance for antenna  40 - 4  within the cellular high band. The perimeter of vertical slot  120  (i.e., length  114 , width  116 , and thus the length of path  122 ) may be selected so that vertical slot  120  contributes a frequency response for antenna  40 - 4  at desired frequencies within the cellular high band. For example, the perimeter of vertical slot  120  (e.g., the length of path  122 ) may be approximately one-half of the effective wavelength corresponding to a frequency within the cellular high band. 
     Directly feeding vertical slot  120  in this way may optimize the frequency response of antenna  40 - 4  in the cellular high band relative to scenarios where segment  16 - 4  is only indirectly fed by the end of resonating element arm  66  (e.g., because vertical slot  120  offers a greater antenna area/aperture for covering the cellular high band than segment  16 - 4 ). For example, directly feeding vertical slot  120  may pull the overall frequency response of antenna  40 - 4  to higher frequencies within the cellular high band and may increase the overall antenna efficiency of antenna  40 - 4  within the cellular high band than when segment  16 - 4  is only indirectly fed. 
     The state of tuning component  102 E may be toggled to adjust the frequency response of antenna  40 - 4  within the cellular high band (e.g., by toggling antenna  40 - 4  between directly feeding vertical slot  120  and indirectly feeding segment  16 - 4 ). However, if care is not taken, directly feeding vertical slot  120  in this way may deteriorate the frequency response of antenna  40 - 4  at other frequencies such as in the cellular low-midband. 
     Adjustable component  102 D may be adjusted to tune the frequency response of antenna  40 - 4  within the cellular low-midband and/or the cellular midband (e.g., when positive antenna feed terminals  46 B and  46 C are active). As one example, adjustable component  102 D may have first, second, and third tuning states. In the first tuning state, adjustable component  102 D may form a return path (e.g., return path  68  of  FIG. 5 ) between terminal  108  on segment  16 - 3  and terminal  124  on ground structures  78 . In the first tuning state, an open circuit may be formed between terminal  104  and terminal  124  as well as between terminal  104  and terminal  108 . In the second tuning state, a capacitance may be interposed between terminal  104  and terminal  124 . In the third tuning state, an inductance may be interposed between terminal  104  and terminal  124 . In the second and third tuning states, an open circuit may be formed between terminal  108  and terminal  104  as well as between terminal  108  and terminal  124 . Adjustable component  102 D may be placed in a selected one of the first, second, and third tuning states to tune the frequency response of antenna  40 - 4  within the cellular low-midband and/or the cellular midband (e.g., to compensate for potential deterioration in antenna efficiency at these frequencies when vertical slot  120  is directly fed). 
     When positive antenna feed terminal  46 A and/or  46 B is active, the length of resonating element arm  66  between positive antenna feed terminal  46 A and gap  18 - 2 , and/or between positive antenna feed terminal  46 B and gap  18 - 3  may handle relatively low frequencies such as frequencies in the cellular low band. For example, this length may be selected to be approximately equal to one-quarter of the effective wavelength corresponding to a frequency in the cellular low band. Adjustable components  102 A and/or  102 B may be adjusted to tune the frequency response of antenna  40 - 4  in the cellular low band. For example, adjustable components  102 A and  102 B may include one or more inductors, capacitors, and/or resistors that are selectively switched into or out of use to tune the frequency response of antenna  40 - 4  in the cellular low band. 
     Feeding antenna  40 - 4  using positive antenna feed terminal  46 B may limit the length of resonating element arm  66  that is available to cover the cellular low band. In addition, operations at relatively low frequencies such as frequencies in the cellular low band may be particularly susceptible to loading by ground structures  78  and external objects such as a user&#39;s hand or body. In scenarios where the length of resonating element arm  66  extending from positive antenna feed terminal  46 B to gap  18 - 3  is used to support communications in the cellular low band, ground extension  80  and other structures associated with display  14  ( FIG. 1 ) may undesirably load resonating element arm  66  in the cellular low band. This may limit antenna efficiency at frequencies in the cellular low band. Such undesirable loading may be mitigated by using portions of resonating element arm  66  that are located farther from ground extension  80  and gap  18 - 3  to cover the cellular low band. 
     In order to optimize performance within the cellular low band, positive antenna feed terminal  46 A may be used while positive antenna feed terminals  46 B and  46 C are inactive (disabled). Adjustable component  102 C may have a first state at which an open circuit is formed between node  100  and terminal  104  of adjustable component  102 D and may have a second state at which node  100  is shorted to terminal  104 . Adjustable component  102 C may be placed in the first state to activate (enable) positive antenna feed terminal  46 A while deactivating (disabling) positive antenna feed terminals  46 B and  46 C. 
     The length of resonating element arm  66  extending from terminal  134  to gap  18 - 2  may be selected to cover frequencies in the cellular low band. For example, this length may be selected to be approximately equal to one-quarter of the effective wavelength corresponding to a frequency in the cellular low band. Activating positive antenna feed terminal  46 A while deactivating positive antenna feed terminals  46 B and  46 C may serve to shift electromagnetic hotspots in the cellular low band away from gap  18 - 3  and ground extension  80  and towards gap  18 - 2 . This may serve to minimize loading in the cellular low-band by ground extension  80  and other conductive portions of display  14  of  FIG. 1 , as well as by external objects such as the user&#39;s body, thereby maximizing antenna efficiency in the cellular low band. When positive antenna feed terminal  46 A is active and positive antenna feed terminals  46 B and  46 C are inactive, adjustable components  102 A and/or  102 B may be adjusted to tune the frequency response of antenna  40 - 4  in the cellular low band. 
     In some scenarios, positive antenna feed terminal  46 A is fed using a dedicated transmission line other than transmission line  50 - 4 . Switching circuitry is used to selectively couple each transmission line to transceiver circuitry  26  ( FIG. 4 ). However, use of a separate transmission line and the corresponding switching circuitry can undesirably attenuate the radio-frequency signals conveyed by positive antenna feed terminal  46 A. This attenuation may be eliminated by using the same radio-frequency transmission line  50 - 4  to convey signals to each of positive antenna feed terminals  46 A,  46 B, and  46 C. At the same time, positive antenna feed terminal  46 A is located relatively far from transmission line  50 - 4 . If care is not taken, the relatively long conductive path length from signal conductor  52  to positive antenna feed terminal  46 A may introduce excessive inductance between signal conductor  52  and positive antenna feed terminal  46 A. This inductance may undesirably limit the antenna efficiency for antenna  40 - 4  in the cellular low band when positive antenna feed terminal  46 A is active. 
     Conductive trace  90  may be configured to minimize the inductance associated with the relatively long conductive path length between signal conductor  52  and positive antenna feed terminal  46 A. Conductive trace  90  may have a first end  98  coupled to node  100  on signal conductor  52  and an opposing second end  96  coupled to node  130  on path  128 . Node  130  may be interposed on path  128  between adjustable component  102 B and positive antenna feed terminal  46 A. Conductive trace  90  may have a length (e.g., a longest rectangular dimension or longitudinal axis) that extends from end  96  to end  98 . Conductive trace  90  may have a width  94  (e.g., a shortest rectangular dimension or dimension perpendicular to the longitudinal axis). 
     In order minimize the inductance between positive antenna feed terminal  46 A and signal conductor  52 , conductive trace  90  may have a relatively large width  94 . In general, larger (wider) widths  94  may reduce the inductance between signal conductor  52  and positive antenna feed terminal  46 A more than shorter (narrower) widths  94 . At the same time, width  94  may be limited by the amount of space available between ground structures  78  and segment  16 - 3  (e.g., the width of slot  76 ). As examples, width  94  may be between 2.0 mm and 2.3 mm, between 2.5 mm and 2.9 mm, approximately 2.7 mm, between 1 mm and 4 mm, or any other desired width that balances a reduction in inductance with the amount of available space within slot  76 . The length of conductive trace  90  (e.g., as measured perpendicular to width  94  or from end  96  to end  98 ) may be approximately 20 mm, between 15 mm and 25 mm, between 10 mm and 20 mm, or any other desired length. The ratio of the length of conductive trace  90  to width  94  may be between 3 and 10, between 2 and 10, between 5 and 15, between 6 and 10, between 5 and 9, or any other desired ratio, as examples. 
     Conductive trace  90  may be located at a distance  88  from segment  16 - 3  and at a distance  92  from ground structures  78  (e.g., conductive trace  90  may be separated from ground structures  78  by portion  84  of slot  76  and may be separated from segment  16 - 3  by portion  86  of slot  76 ). Distance  88  (e.g., the width of portion  86  of slot  76 ) may be shorter than distance  92  (e.g., the width of portion  84  of slot  76 ). Distance  88  may be selected to allow conductive trace  90  to form a distributed capacitance with segment  16 - 3  such that when positive antenna feed terminal  46 B is active (e.g., when node  100  is shorted to terminal  104  of adjustable component  102 D), conductive trace  90  electrically forms a single integral conductor with segment  16 - 3 . When positive antenna feed terminal  46 B is inactive (e.g., when adjustable component  102 C forms an open circuit between node  100  and terminal  104  of adjustable component  102 D), conductive trace  90  electrically forms an inductor that is coupled in series between node  100  and node  130  and that has an inductance that is lower than in scenarios where a conductive line or wire is used to connect node  100  to node  130 . As examples, distance  92  may be approximately 1.0 mm, between 0.8 mm and 1.2 mm, between 0.6 and 1.4 mm, or any other desired distance. Distance  88  may be approximately 0.5 mm, between 0.3 mm and 0.7 mm, between 0.2 mm and 0.8 mm, between 0.6 mm and 0.1 mm, or any other desired distance that is less than distance  92 . 
     Conductive trace  90  may be formed on the dielectric material that is used to fill slot  76  (e.g., dielectric material that forms part of the exterior of device  10 ) or may be formed on a dielectric substrate mounted within slot  76  (e.g., a plastic block, flexible printed circuit, rigid printed circuit board, dielectric portions of other device components, etc.). Conductive trace  90  may be formed using other conductive structures such as stamped sheet metal, metal foil, integral portions of the housing for device  10 , and/or any other desired conductive structures. The example of  FIG. 8  is merely illustrative. If desired, conductive trace  90  may have other shapes (e.g., shapes following straight or meandering paths and having curved and/or straight edges). Fewer or additional adjustable components  102  may be coupled between any desired locations on antenna  40 - 4 . 
     When configured in this way, conductive trace  90  may form a relatively low-inductance feed line combiner that allows positive antenna feed terminals  46 A and  46 B to share the same signal conductor  52  without sacrificing antenna efficiency even though the terminals are located relatively far apart. Conductive trace  90  may sometimes be referred to herein as feed combiner trace  90 , low inductance trace  90 , low inductance feed combiner trace  90 , low inductance feed line combiner trace  90 , fat trace  90 , thick trace  90 , wide trace  90 , low inductance path  90 , low inductance feed combiner structure  90 , or feed line inductance limiting structure  90 . 
     Adjustable components  102 A- 102 E may overlap slot  76 . If desired, adjustable components  102 A- 102 E may be formed on one or more printed circuits such as a flexible printed circuit board that is coupled between peripheral conductive housing structures  16  and ground structures  78 . Ground structures  78  may include conductive portions of display  14  ( FIG. 1 ), a conductive housing layer for device  10 , and/or other conductive layers. If desired, conductive structures such as vertical conductive interconnect structures (e.g., brackets, clips, springs, pins, screws, solder, welds, conductive adhesive, wires, metal strips, etc.) may be used to short conductive portions of display  14  ( FIG. 1 ) to the conductive housing layer and/or other portions of ground structures  78  (e.g., at the locations of terminals  132 ,  126 ,  48 , and/or  124 ). Electrically connecting different components in ground structures  78  using vertical conductive interconnect structures may ensure that the conductive structures that are located the closest to resonating element arm  66  are held at a ground potential and form a part of the antenna ground for antenna  40 - 4 . This may serve to optimize the antenna efficiency of antenna  40 - 4 , for example. Conductive interconnect structures such as brackets, clips, springs, pins, screws, solders, welds, conductive adhesive, etc. may be used to couple terminals  134 ,  46 A,  46 B,  108 , and/or  46 C to peripheral conductive housing structures  16 . While the example of  FIG. 8  shows antenna structures for implementing antenna  40 - 4  in device  10 , these structures may be used to implement any one of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , or  40 - 4  of device  10  ( FIG. 4 ) and/or may be used to implement any desired antennas  40  in device  10 . 
     If desired, control circuitry  28  ( FIG. 3 ) may control adjustable components  102  to place antenna  40 - 4  in one of first or second operating modes (states). In the first operating mode, control circuitry  28  controls adjustable component  102 C to couple node  100  to terminal  104  of adjustable component  102 D so that positive antenna feed terminal  46 B is active. Conductive trace  90  and segment  16 - 3  may electrically form a single integral conductor. This may effectively render positive antenna feed terminal  46 A inactive (e.g., antenna current will not flow into segment  16 - 3  from positive antenna feed terminal  46 A). 
     In the first operating mode, the length of resonating element arm  66  between positive antenna feed terminal  46 B and gap  18 - 2  may exhibit a fundamental mode that supports communications in the cellular midband and the cellular low-midband. This length may exhibit harmonic modes that support communications in the cellular ultra-high band. The length of resonating element arm  66  between positive antenna feed terminal  46 B and gap  18 - 3  may support communications in the cellular low band. 
     In the first operating mode, control circuitry  28  may control adjustable component  102 E to form an open circuit so that resonating element arm  66  indirectly feeds segment  16 - 4  to cover the cellular high band. This may effectively deactivate positive antenna feed terminal  46 C. If desired, control circuitry  28  may control adjustable component  102 E to couple signal conductor  52  to positive antenna feed terminal  46 C. This may effectively activate positive antenna feed terminal  46 C so that vertical slot  120  is directly fed for covering the cellular high band (e.g., at higher frequencies than when adjustable component  102 E forms an open circuit). Control circuitry  28  may control adjustable component  102 E to adjust the inductance between signal conductor  52  and positive antenna feed terminal  46 C to further tweak the frequency response of antenna  40 - 4  if desired. 
     In the second operating mode, control circuitry  28  controls adjustable component  102 C to form an open circuit between node  100  and terminal  104  of adjustable component  102 D. This effectively activates positive antenna feed terminal  46 A (e.g., antenna current flows into segment  16 - 3  through conductive trace  90  and positive antenna feed terminal  46 A) and deactivates positive antenna feed terminals  46 B and  46 C (e.g., antenna current does not flow into segment  16 - 3  through positive antenna feed terminal  46 B or into segment  16 - 4  through positive antenna feed terminal  46 C). 
     Control circuitry  28  ( FIG. 3 ) may place antenna  40 - 4  into the first or second operating modes based on the needs and/or operating environment of device  10 . For example, control circuitry  28  may place antenna  40 - 4  in the second operating mode (sometimes referred to herein as a low band operating mode) when antenna  40 - 4  is assigned a frequency in the cellular low band or when communications in the cellular low band is otherwise prioritized over communications in other bands (e.g., by software running on device  10  or by external equipment such as a cellular base station). Similarly, control circuitry  28  may place antenna  40 - 4  in the first operating mode (sometimes referred to herein as a multi-band operating mode or a high band operating mode) when antenna  40 - 4  is assigned a frequency outside of the cellular low band. Control circuitry  28  may adjust the state of adjustable components  102 A and/or  102 B to tune the frequency response in the cellular low band in either of the first or second operating modes. Control circuitry  28  may adjust the state of adjustable components  102 D and/or  102 E to tune the frequency response in the cellular low-midband, the cellular midband, the cellular high band, and/or the cellular ultra-high band in the first operating mode. 
       FIGS. 9A-9D  are circuit diagrams of illustrative circuits that may be used to form any of the adjustable components  102  of  FIG. 8 . 
     As shown in  FIG. 9A , adjustable component  136  may include a switch SW 1  coupled in series between terminals  138  and  140 . Switch SW 1  may be, for example, a single-pole single-throw (SPST) switch. When switch SW 1  is placed in an open (off) state, an open circuit is formed between terminals  138  and  140 . When switch SW 1  is placed in a closed (on) state, a short circuit path is formed between terminals  138  and  140 . If desired, one or more resistors, capacitors, and/or inductors may be coupled in series between terminals  138  and  140 . 
     In one suitable arrangement, adjustable component  136  may be used to form adjustable component  102 C of  FIG. 8  (e.g., terminal  138  may be coupled to node  100  of  FIG. 8  whereas terminal  140  is coupled to terminal  104  of  FIG. 8 ). If desired, adjustable component  136  may also be used to form adjustable component  102 E of  FIG. 8  (e.g., terminal  140  may be coupled to positive antenna feed terminal  46 B of  FIG. 8  whereas terminal  138  is coupled to positive antenna feed terminal  46 C of  FIG. 8 ). 
     As shown in  FIG. 9B , adjustable component  142  includes multiple inductors that are used in providing antenna  40 - 4  with an adjustable amount of inductance (e.g., component  142  may sometimes be referred to as an adjustable inductor or adjustable inductor circuitry). Control circuitry  28  ( FIG. 3 ) may adjust circuitry  142  of  FIG. 9B  to produce different amounts of inductance between terminal  144  and terminal  146  by controlling the state of switching circuitry such as switches SW 2  and SW 3 . Switches SW 2  and SW 3  may be implemented as two SPST switches, as one single-pole double-throw (SP2T) switch, or using any other desired circuitry. 
     For example, control signals may be used to switch inductor L 1  into use between terminals  144  and  146  while switching inductor L 2  out of use, may be used to switch inductor L 2  into use between terminals  144  and  146  while switching inductor L 1  out of use, may be used to switch both inductors L 1  and L 2  into use in parallel between terminals  144  and  146 , or may be used to switch both inductors L 1  and L 2  out of use. The switching circuitry arrangement of  FIG. 9B  is therefore able to produce one or more different inductance values, two or more different inductance values, three or more different inductance values, or, if desired, four different inductance values (e.g., L 1 , L 2 , L 1  and L 2  in parallel, or infinite inductance when L 1  and L 2  are switched out of use simultaneously). 
     In one suitable arrangement, adjustable component  142  may be used to form adjustable component  102 B of  FIG. 8  (e.g., terminal  146  may be coupled to node  130  of  FIG. 8  whereas terminal  144  is coupled to terminal  126  of  FIG. 8 ). In this scenario, the inductance of adjustable component  142  can be toggled to tune the cellular low band response of antenna  40 - 4 . If desired, adjustable component  142  may be used to form adjustable component  102 E of  FIG. 8  (e.g., terminal  144  may be coupled to positive antenna feed terminal  46 B of  FIG. 8  whereas terminal  146  is coupled to positive antenna feed terminal  46 C of  FIG. 8 ). In this scenario, the inductance of adjustable component  142  can be toggled to tune the cellular high band response of antenna  40 - 4 . 
     As shown in  FIG. 9C , adjustable component  148  may include an inductor L 3  coupled in series with switch SW 4 , an inductor L 4  coupled in series with switch SW 5 , an inductor L 5  coupled in series with switch SW 6 , an inductor L 6  coupled in series with switch SW 7 , and an inductor L 7  coupled in parallel between terminal  150  and terminal  152 . Inductors L 3 -L 7  may be used in providing antenna  40 - 4  with an adjustable amount of inductance. Control circuitry  28  may adjust component  148  to produce different amounts of inductance between terminal  150  and terminal  152  by controlling the state of the switches in component  148 . Each of the switches may be, for example, a single-pole single-throw (SPST) switch, the switches may be implemented using a single-pole four-throw (SP4T) switch, or any other desired switching circuitry may be used. 
     In one suitable arrangement, adjustable component  148  may be used to form adjustable component  102 A of  FIG. 8  (e.g., terminal  150  may be coupled to terminal  132  of  FIG. 8  whereas terminal  152  is coupled to terminal  134  of  FIG. 8 ). In this scenario, the inductance of adjustable component  148  can be toggled to tune the cellular low band response of antenna  40 - 4 . 
     As shown in  FIG. 9D , adjustable component  154  may be a three-terminal component having terminals  158 ,  156 , and  160 . Adjustable component  154  may include an inductor L 8  coupled in series with switch SW 9  and a capacitor C coupled in series with switch SW 8  in parallel between terminals  158  and  156 . Adjustable component  154  may include an inductor L 9  coupled in series between terminals  160  and  156 . Control circuitry  28  may adjust component  154  to close zero, one, or more than one of switches SW 8 , SW 9 , and SW 10  at any given time to adjust the impedance between terminals  158 ,  156 , and  160 . 
     In one suitable arrangement, adjustable component  154  may be used to form adjustable component  102 D of  FIG. 8  (e.g., terminal  158  may be coupled to terminal  104  of  FIG. 8 , terminal  160  may be coupled to terminal  108  of  FIG. 8 , and terminal  156  may be coupled to terminal  124  of  FIG. 8 ). In this scenario, control circuitry  28  may adjust component  154  to tune the frequency response of antenna  40 - 4  in the cellular low-midband, the cellular midband, the cellular high band, and/or the cellular ultra-high band (e.g., while antenna  40 - 4  is in the first mode of operation in which positive antenna feed terminal  46 B is active). 
     The examples of  FIGS. 9A-9D  are merely illustrative. In general, adjustable components  136 ,  142 ,  148 , and  154  may each include any desired number of inductive, capacitive, resistive, and switching elements arranged in any desired manner (e.g., in series, in parallel, in shunt configurations, etc.). These components may be used to form any of adjustable components  102 A,  102 B,  102 C,  102 D, or  102 E of  FIG. 8 . 
       FIG. 10  is a flow chart of illustrative steps involved in operating device  10  to ensure satisfactory performance for antenna  40 - 4  of  FIG. 8  in all desired frequency bands of interest. 
     At step  162  of  FIG. 10 , control circuitry  28  may monitor the operating environment of device  10  and/or frequencies to use for performing wireless communications. The frequencies to use may be determined based on software running on control circuitry  28  (e.g., software controlling wireless communications for device  10 ) and/or based on an assignment received from external equipment like a wireless base station. 
     Control circuitry  28  may, in general, use any suitable type of sensor measurements, wireless signal measurements, operation information, or antenna measurements to determine how device  10  is being used (e.g., to determine the operating environment of device  10 ). For example, control circuitry  28  may use sensors such as temperature sensors, capacitive proximity sensors, light-based proximity sensors, resistance sensors, force sensors, touch sensors, connector sensors that sense the presence of a connector in a connector port or that detect the presence or absence of data transmission through a connector port, sensors that detect whether wired or wireless headphones are being used with device  10 , sensors that identify a type of headphone or accessory device that is being used with device  10  (e.g., sensors that identify an accessory identifier identifying an accessory that is being used with device  10 ), or other sensors to determine how device  10  is being used. Control circuitry  28  may also use information from an orientation sensor such as an accelerometer in device  10  to help determine whether device  10  is being held in a position characteristic of right hand use or left hand use (or is being operated in free space). Control circuitry  28  may also use information about a usage scenario of device  10  in determining how device  10  is being used (e.g., information identifying whether audio data is being transmitted through ear speaker  8  of  FIG. 1 , information identifying whether a telephone call is being conducted, information identifying whether a microphone on device  10  is receiving voice signals, etc.). 
     If desired, an impedance sensor or other sensor may be used in monitoring the impedance of antenna  40 - 4  or part of antenna  40 - 4 . Different antenna loading scenarios may load antenna  40 - 4  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 - 4 . In this example, the adjustable circuitry of antenna  40 - 4  can be toggled between different settings and an optimum setting for antenna  40 - 4  can be identified by choosing a setting that maximizes received signal strength. In general, any desired combinations of one or more of these measurements or other measurements may be processed by control circuitry  28  to identify how device  10  is being used (i.e., to identify the operating environment of device  10 ). 
     At step  164 , control circuitry  28  may adjust the configuration of antenna  40 - 4  (e.g., antenna settings for antenna  40 - 4 ) based on the current operating environment of device  10  and/or the frequencies to use for communications (e.g., based on data or information gathered while processing step  162 ). Control circuitry  28  may place antenna  40 - 4  into one of the first and second operating modes using adjustable component  102 C of  FIG. 8  and may adjust components  102 A,  102 B,  102 D, and/or  102 E to further adjust the frequency response of antenna  40 - 4  based on the information gathered while processing step  162  of  FIG. 10 . 
     At step  166 , antenna  40 - 4  may be used to transmit and receive wireless data using the antenna settings selected at step  164 . This process may be performed continuously, as indicated by path  168 . In this way, antenna  40 - 4  may be dynamically adjusted in real time based on the operating environment and needs of device  10 . Similar steps may be used to adjust antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and/or other antennas  40  in device  10  if desired. 
       FIG. 11  is a graph in which antenna performance (antenna efficiency) has been plotted as a function of operating frequency for antenna  40 - 4  of  FIG. 8 . As shown in  FIG. 11 , curve  170  plots an exemplary antenna efficiency of antenna  40 - 4  while antenna  40 - 4  is in the first operating mode and while adjustable component  102 E forms an open circuit (e.g., while positive antenna feed terminal  46 B is active and positive antenna feed terminals  46 A and  46 C are inactive). 
     When placed in this configuration, the length of resonating element arm  66  between positive antenna feed terminal  46 A and gap  18 - 2  ( FIG. 8 ) may support a response peak in a first frequency band such as cellular low band LB (e.g., a frequency band between about 600 MHz and 960 MHz). The length of resonating element arm  66  between positive antenna feed terminal  46 B and gap  18 - 2  may support a response peak that extends across a second frequency band such as cellular low-midband LMB (e.g., a frequency band between about 1410 MHz and 1510 MHz) and a third frequency band such as cellular midband MB (e.g., a frequency band between about 1710 MHz and 2170 MHz). The end (tip) of resonating element arm  66  may indirectly feed segment  16 - 4  of peripheral conductive housing structures  16  to support a response peak in a fourth frequency band such as cellular high band HB (e.g., a frequency band between about 2300 MHz and 2700 MHz). A harmonic mode of the portion of resonating element arm  66  between positive antenna feed terminal  46 B and gap  18 - 2  may support a response peak in a fifth frequency band such as cellular ultra-high band UHB (e.g., a frequency band between about 3400 MHz and 3600 MHz). Control circuitry  28  may adjust components  102 A and/or  102 B to adjust the frequency response in cellular low band LB and may adjust component  102 D to adjust the frequency response in cellular midband MB, cellular high band HB, and/or cellular ultra-high band UHB. 
     As shown by curve  170  of  FIG. 11 , the response peak in cellular high band HB may only cover relatively low frequencies in cellular high band HB without providing satisfactory efficiency at higher frequencies in cellular high band HB. In order to cover the entirety of cellular high band HB with satisfactory efficiency, control circuitry  28  may control adjustable component  102 E to activate positive antenna feed terminal  46 C (e.g., to directly feed vertical slot  120 ). 
     Curve  172  plots an exemplary antenna efficiency of antenna  40 - 4  while antenna  40 - 4  is in the first operating mode and while positive antenna feed terminal  46 C is active. When placed in this configuration, vertical slot  120  is directly fed over positive antenna feed terminal  46 C and path  106  of  FIG. 8 . This may serve to pull the coverage of antenna  40 - 4  in cellular high band HB to higher frequencies as well as to increase the overall efficiency of antenna  40 - 4  within cellular high band HB. 
     Directly feeding vertical slot  120  as shown by curve  172  of  FIG. 11  may also reduce antenna efficiency within the second frequency band (e.g., within cellular low-midband LMB). If desired, control circuitry  28  may adjust component  102 D of  FIG. 8  to pull the frequency response of antenna  40 - 4  downwards to also cover cellular low-midband LMB without substantially affecting coverage in cellular high band HB. Control circuitry  28  may adjust components  102 A and/or  102 B to adjust the frequency response in cellular low band LB and may adjust component  102 D to adjust the frequency response in cellular low-midband LMB, cellular midband MB, cellular high band HB, and/or cellular ultra-high band UHB. 
     Curve  174  of  FIG. 11  plots the antenna efficiency of antenna  40 - 4  in scenarios where positive antenna feed terminal  46 A is fed using a dedicated transmission line or in scenarios where node  100  is coupled to node  130  ( FIG. 8 ) by a wire or other thin conductive line having insufficient width. In scenarios where positive antenna feed terminal  46 A is fed using a dedicated transmission line, attenuation from the dedicated transmission line and the associated additional switching circuitry limits the peak antenna efficiency in cellular low band LB. In scenarios where node  100  is coupled to node  130  by a wire or other thin conductive line having insufficient width, the inductance associated with the relatively long electrical path length from signal conductor  52  to positive antenna feed terminal  46 A limits the peak antenna efficiency in cellular low band LB. 
     Curve  176  of  FIG. 11  plots an exemplary antenna efficiency of antenna  40 - 4  while antenna  40 - 4  is placed in the second operating mode (e.g., when positive antenna feed terminal  46 A is active and positive antenna feed terminals  46 B and  46 C are inactive). When placed in this configuration, electromagnetic hot spots in cellular low band LB are moved away from ground extension  80  ( FIG. 8 ) without introducing attenuation associated with a dedicated transmission line and its switching circuitry and without introducing excessive inductance between signal conductor  52  and positive antenna feed terminal  46 A. This may serve to increase the peak antenna efficiency and/or bandwidth of antenna  40 - 4  within cellular low band LB, as shown by arrow  178 . 
     The example of  FIG. 11  is merely illustrative. In general, antenna  40 - 4  may cover any desired bands at any desired frequencies (e.g., antenna  40 - 4  may exhibit any desired number of efficiency peaks extending over any desired frequency bands). Curves  170 ,  172 ,  174 , and  176  may have other shapes if desired. 
     In this way, device  10  may be provided with a display  14  ( FIG. 1 ) having an active area AA that extends across substantially all of the front face of device  10 . Antenna  40 - 4  may be provided with satisfactory antenna efficiency across multiple frequency bands of interest despite the presence of the conductive display structures used to support such a large active area AA for display  14 . Antenna  40 - 4  may operate using a carrier aggregation scheme across one or more of these frequency bands and using a MIMO scheme with the other antennas in device  10  to maximize wireless data throughput for device  10 . 
     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: 20180626
Publication Date: 20211221
Grant Date: 20211221
Priority Date: 20180626
Inventors: AYALA VAZQUEZ, ENRIQUE
HU, HONGFEI
PASCOLINI, MATTIA
JIN, NANBO
FROESE, KEVIN M.
TONG, ERICA J.
HAN, XU
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/242", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/46", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2258", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/314", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/0249", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/50", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/22", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/50", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q13/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/242", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0277", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/242", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 67385420