PATENT DOCUMENT

Publication Number: US-10644758-B2
Application Number: US-201916265462-A
Country: US
Kind Code: B2

Title: Electronic device having multiple antennas with shared structures for near-field communications and non-near-field communications

Abstract:
An electronic device may include a peripheral conductive wall. A gap in the wall may divide the wall into first and second segments. The device may include a first antenna having a first resonating element arm formed from the first segment and a second antenna having a second resonating element arm formed from the second segment. A non-near-field communications transceiver may perform multiple-input and multiple-output (MIMO) operations using the first and second antennas. The gap may provide satisfactory isolation between the first and second antennas while the first and second antennas perform MIMO operations. Near-field communications circuitry may convey near-field communications signals over a conductive loop path that includes portions of the first and second segments and the antenna ground. The volume of the conductive loop path may extend across substantially all of a width of the electronic device.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a housing having peripheral conductive structures; 
 first, second, and third dielectric-filled gaps in the peripheral conductive structures, wherein a first segment of the peripheral conductive structures extends between the first and third dielectric-filled gaps and a second segment of the peripheral conductive structures extends between the third and second dielectric-filled gaps; 
 an antenna ground, wherein the first dielectric-filled gap separates the first segment from the antenna ground and the second dielectric-filled gap separates the second segment from the antenna ground; 
 an inductor coupled between the first and second segments across the third dielectric filled-gap; and 
 near-field communications transceiver circuitry configured to convey near-field communications signals over a conductive loop path that includes the first and second segments, the inductor, and a portion of the antenna ground. 
 
     
     
       2. The electronic device defined in  claim 1 , further comprising:
 a first antenna feed having a first feed terminal coupled to the first segment and a second feed terminal coupled to the antenna ground; 
 a second antenna feed having a third feed terminal coupled to the second segment and a fourth feed terminal coupled to the antenna ground; and 
 non-near-field communications circuitry coupled to the first and second antenna feeds and configured to concurrently convey non-near-field communications signals at a given frequency over both the first and second antenna feeds. 
 
     
     
       3. The electronic device defined in  claim 2 , wherein the given frequency is in a first non-near-field communications frequency band, an additional frequency is in a second non-near-field communications frequency band that is higher than the first non-near-field communications frequency band, and the non-near-field communications circuitry is configured to concurrently convey the non-near-field communications signals at both the given frequency and the additional frequency over the first and second antenna feeds. 
     
     
       4. The electronic device defined in  claim 1 , further comprising:
 a first additional inductor coupled between the first segment and the antenna ground; and 
 a second additional inductor coupled between the near-field communications transceiver circuitry and the second segment, wherein the conductive loop path includes the first and second additional inductors. 
 
     
     
       5. The electronic device defined in  claim 4 , wherein the first additional inductor is coupled to a first point on the first segment, the electronic device further comprising:
 a first antenna feed coupled to a second point on the first segment; 
 a first return path coupled between a third point on the first segment and the antenna ground; 
 a second return path coupled between a first point on the second segment and the antenna ground; and 
 a second antenna feed coupled to a second point on the second segment and the antenna ground, wherein the second point on the first segment is interposed between the first and third points on the first segment, the third point on the first segment is interposed between the second point on the first segment and the third dielectric-filled gap, and the first point on the second segment is interposed between the third dielectric-filled gap and the second point on the second segment. 
 
     
     
       6. The electronic device defined in  claim 5 , wherein the second additional inductor is coupled to the second point on the second segment, the electronic device further comprising:
 a first capacitor coupled between the first antenna feed and the second point on the first segment; 
 a second capacitor interposed on the first return path; 
 a third capacitor interposed on the second return path; and 
 a fourth capacitor coupled between the second antenna feed and the second point on the second segment, wherein the first, second, third, and fourth capacitors are configured to form short circuits at a non-near-field communications frequency and to form open circuits at a near-field communications frequency. 
 
     
     
       7. An electronic device comprising:
 a housing having first, second, and third conductive housing structures, wherein the second conductive housing structure is separated from the first conductive housing structure by a first dielectric-filled gap, the third conductive housing structure is separated from the first conductive structure by a second dielectric-filled gap, and the third conductive housing structure is separated from the second conductive housing structure by a third dielectric-filled gap; 
 an inductor coupled between the second and third conductive housing structures across the third dielectric-filled gap; and 
 near-field communications transceiver circuitry configured to convey near-field communications signals over a conductive loop path that includes the second and third conductive housing structures, the inductor, and a portion of the first conductive structure. 
 
     
     
       8. The electronic device defined in  claim 7 , further comprising:
 an additional inductor that couples the near-field communications transceiver circuitry to the third conductive housing structure, wherein the conductive loop path includes the additional inductor. 
 
     
     
       9. The electronic device defined in  claim 8 , further comprising:
 an adjustable inductor coupled between the first and second conductive housing structures across the first dielectric-filled gap, wherein the conductive loop path includes the adjustable inductor. 
 
     
     
       10. The electronic device defined in  claim 9 , further comprising:
 a capacitor coupled between the first and second conductive housing structures, wherein the capacitor is separate from the conductive loop path. 
 
     
     
       11. The electronic device defined in  claim 10 , further comprising:
 an additional capacitor coupled between the first and third conductive housing structures, wherein the additional capacitor is separate from the conductive loop path. 
 
     
     
       12. The electronic device defined in  claim 7 , wherein the first conductive housing structure is held at a ground potential. 
     
     
       13. The electronic device defined in  claim 7 , further comprising:
 an antenna feed coupled between the first and second conductive housing structures. 
 
     
     
       14. The electronic device defined in  claim 13 , further comprising:
 an additional antenna feed coupled between the first and third conductive housing structures. 
 
     
     
       15. The electronic device defined in  claim 14 , wherein the antenna feed comprises a first positive antenna feed terminal and the additional antenna feed comprises a second positive antenna feed terminal, the electronic device further comprising:
 a first capacitor coupled between the first positive antenna feed terminal and the second conductive housing structure; and 
 a second capacitor coupled between the second positive antenna feed terminal and the third conductive housing structure. 
 
     
     
       16. The electronic device defined in  claim 15 , further comprising:
 a third capacitor coupled between the first and third conductive housing structures; and 
 a fourth capacitor coupled between the second and third conductive housing structures. 
 
     
     
       17. The electronic device defined in  claim 16 , wherein the antenna feed and the additional antenna feed are configured to convey non-near-field communications signals at a frequency greater than 600 MHz. 
     
     
       18. The electronic device defined in  claim 7 , further comprising:
 a display having a display cover layer mounted to the first, second, and third conductive housing structures. 
 
     
     
       19. An electronic device comprising:
 a housing having peripheral conductive structures; 
 first, second, and third dielectric-filled gaps in the peripheral conductive structures, wherein a first segment of the peripheral conductive structures extends between the first and third dielectric-filled gaps and a second segment of the peripheral conductive structures extends between the third and second dielectric-filled gaps; 
 ground structures, wherein the first dielectric-filled gap separates the first segment from the ground structures and the second dielectric-filled gap separates the second segment from the ground structures; 
 an inductor coupled between the first and second segments across the third dielectric filled-gap; and 
 a near-field communications antenna that includes the first and second segments, the inductor, and a portion of the ground structures. 
 
     
     
       20. The electronic device defined in  claim 19 , wherein the electronic device has a first side, a second side that opposes the first side, a third side that extends between the first and second sides, and a fourth side that extends between the first and second sides and that opposes the third side, the first dielectric-filled gap being located along the first side, the second dielectric-filled gap being located along the second side, and the third dielectric-filled gap being located along the third side of the electronic device.

Description:
This application is a division of U.S. patent application Ser. No. 15/719,317, filed Sep. 28, 2017, which is hereby incorporated by reference herein in its entirety. This application claims the benefit of and claims priority to U.S. patent application Ser. No. 15/719,317, filed Sep. 28, 2017. 
    
    
     BACKGROUND 
     This relates to electronic devices, and more particularly, to antennas for electronic devices with wireless communications circuitry. 
     Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry to communicate using cellular telephone bands. Electronic devices may use short-range wireless communications circuitry such as wireless local area network communications circuitry to handle communications with nearby equipment. Electronic devices may also be provided with satellite navigation system receivers and other wireless circuitry such as near-field communications circuitry. Near-field communications schemes involve electromagnetically coupled communications over short distances, typically 20 cm or less. 
     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 a near-field communications band while simultaneously covering additional non-near-field (far-field) bands such cellular telephone bands, wireless local area network bands, and satellite navigation system bands. 
     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 a 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 wall. A dielectric-filled gap in the peripheral conductive wall may divide the peripheral conductive wall into first and second segments. The wireless circuitry may include antenna structures. For example, the wireless circuitry may include a first antenna having a first resonating element arm formed from the first segment and a first antenna feed coupled between the first segment and the antenna ground. The wireless circuitry may include a second antenna having a second resonating element arm formed from the second segment and a second antenna feed coupled between the second segment and the antenna ground. 
     The wireless circuitry may include non-near-field communications transceiver circuitry coupled to the first and second antenna feeds and configured to convey non-near-field communications signals using the first and second antennas. The non-near-field communications transceiver circuitry may concurrently convey the non-near-field communications signals over both the first and second antennas using the same non-near-field communications frequencies under a multiple-input and multiple-output (MIMO) scheme. The dielectric-filled opening in the peripheral conductive wall may ensure that the first and second antennas are electromagnetically isolated at these frequencies. 
     The wireless circuitry may include near-field communications transceiver circuitry coupled to the second segment over a first inductor and configured to convey near-field communications signals over a conductive loop path that forms a loop antenna resonating element for a near-field communications loop antenna. A second inductor may be coupled between the first and second segments across the dielectric-filled opening. An inductive return path may be coupled between the first segment and the antenna ground. Capacitor circuitry may be used to prevent non-near-field communications signals from interfering with the near-field communications transceiver circuitry. The first and second inductors may isolate the first and second antennas at non-near-field communications frequencies. The conductive loop path for the near-field communications loop antenna may include the first and second segments of the peripheral conductive housing wall, the first and second inductors, the inductive return path, and portions of the antenna ground. In this way, the same antenna structures may be used to perform both non-near-field communications under a MIMO scheme (e.g., with maximal data throughput) and near-field communications while maximizing the volume of the near-field communications loop path. 
    
    
     
       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 antenna structures in an electronic device that can be used to handle both non-near-field communications under a MIMO scheme and near-field communications in accordance with an embodiment. 
         FIG. 8  is a top view of illustrative antenna structures in an electronic device that can be used to handle both MIMO non-near-field communications and near-field communications across an entire width of the device in accordance with an embodiment. 
         FIG. 9  is a plot of antenna performance (antenna efficiency) in non-near-field communications bands for antenna structures of the type shown in  FIGS. 7 and 8  in accordance with an embodiment. 
         FIG. 10  is a circuit diagram of illustrative switchable inductor circuitry that may be used for tuning non-near-field communications in antenna structures of the type shown in  FIGS. 7 and 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 antenna structures. The antenna structures may include antennas for cellular telephone communications and/or other far-field (non-near-field) communications. Circuitry in the antenna structures may allow the antenna structures to form a near-field communications loop antenna to handle near-field communications. The antennas antenna structures may include loop antenna structures, inverted-F antenna structures, strip antenna structures, planar inverted-F antenna structures, slot antenna structures, hybrid antenna structures that include antenna structures of more than one type, or other suitable antenna structures. Conductive structures for the antenna structures 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. Buttons such as button  24  may pass through openings in the cover layer if desired. Button  24  may be omitted if desired. The cover layer may also have other openings such as an opening for speaker port  26 . 
     Housing  12  may include peripheral housing structures such as structures  16 . Structures  16  may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape with four edges, structures  16  may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges (as an example). Peripheral structures  16  or part of peripheral structures  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or that helps hold display  14  to device  10 ). Peripheral structures  16  may, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral housing structures  16  may be formed of a conductive material such as metal and may therefore sometimes be referred to as peripheral conductive housing structures, conductive housing structures, peripheral metal structures, 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, or more than two 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  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as 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 (e.g., a fingerprint sensor integrated with a button such as button  24  of  FIG. 1  or a fingerprint sensor that takes the place of button  24 ), etc. 
     Input-output circuitry  30  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  34  may include radio-frequency transceiver circuitry  90  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  42 . Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a low-midband from 960 to 1710 MHz, a midband from 1710 to 2170 MHz, a high band from 2300 to 2700 MHz, an ultra-high band from 3400 to 3700 MHz or other communications bands between 600 MHz and 4000 MHz or other suitable frequencies (as examples). 
     Circuitry  38  may handle voice data and non-voice data. Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include 60 GHz transceiver circuitry, circuitry for receiving television and radio signals, paging system transceivers, etc. Wireless communications circuitry  34  may include global positioning system (GPS) receiver equipment such as GPS receiver circuitry  42  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. In 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 circuitry  34  may include near-field communications circuitry  44  (sometimes referred to herein as near-field communications transceiver circuitry  44 , near-field communications transceiver circuits  44 , near-field communications transceiver  44 , near-field circuitry  44 , near-field transceiver circuitry  44 , or near-field transceiver  44 ). Near-field communications transceiver circuitry  44  may produce and receive near-field communications signals to support communications between device  10  and a near-field communications reader or other external near-field communications equipment. Near-field communications may be supported using loop antennas (e.g., to support inductive near-field communications in which a loop antenna in device  10  is electromagnetically near-field coupled to a corresponding loop antenna in a near-field communications reader). Near-field communications links typically are formed over distances of 20 cm or less (i.e., device  10  must be placed in the vicinity of the near-field communications reader for effective communications). 
     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. In addition to supporting cellular telephone communications, wireless local area network communications, and other far-field wireless communications, the structures of antennas  40  may be used in supporting near-field communications. The structures of antennas  40  may also be used in gathering proximity sensor signals (e.g., capacitive proximity sensor signals). 
     Radio-frequency transceiver circuitry  90  does not handle near-field communications signals and is therefore sometimes referred to as far-field communications circuitry, non-near-field communications circuitry, non-near-field circuitry, or non-near-field communications transceiver circuitry. Near-field communications transceiver circuitry  44  is used in handling near-field communications. With one suitable arrangement, near-field communications can be supported using signals at a frequency of 13.56 MHz or other frequencies below 600 MHz. Other near-field communications bands may be supported using the structures of antennas  40  if desired. Frequencies handled by near-field communications transceiver circuitry  44  in performing near-field communications using wireless near-field communications signals may sometimes be referred to herein as near-field communications frequencies. Transceiver circuitry  90  may handle non-near-field communications frequencies (e.g., frequencies above 600 MHz or other suitable frequencies). 
     The structures forming antennas  40  may sometimes be collectively referred to herein as antenna structures  40 . As shown in  FIG. 3 , antenna structures  40  may be coupled to near-field communications circuitry such as near-field communications transceiver circuitry  44  and non-near-field communications circuitry such as non-near-field communications transceiver circuitry  90 . 
     Non-near-field communications transceiver circuitry  90  in wireless circuitry  34  may be coupled to antenna structures  40  using paths such as path  92 . Near-field communications transceiver circuitry  44  may be coupled to antenna structures  40  using paths such as path  104 . Paths such as path  104  may be used to allow control circuitry  28  to transmit near-field communications data and to receive near-field communications data using a near-field communications antenna formed from structures  40 . 
     Control circuitry  28  may be coupled to input-output devices  32 . Input-output devices  32  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures such as antenna(s)  40  with the ability to cover communications frequencies of interest, antenna(s)  40  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). If desired, antenna(s)  40  may be provided with adjustable circuits such as tunable components  102  to tune antennas over communications bands of interest. Tunable components  102  may be part of a tunable filter or tunable impedance matching network, may be part of an antenna resonating element, may span a gap between an antenna resonating element and antenna ground, etc. 
     Tunable components  102  may include tunable inductors, tunable capacitors, or other tunable components. Tunable components such as these may be based on switches and networks of fixed components, distributed metal structures that produce associated distributed capacitances and inductances, variable solid state devices for producing variable capacitance and inductance values, tunable filters, or other suitable tunable structures. During operation of device  10 , control circuitry  28  may issue control signals on one or more paths such as path  108  that adjust inductance values, capacitance values, or other parameters associated with tunable components  102 , thereby tuning antenna structures  40  to cover desired communications bands. 
     During operation of device  10 , control circuitry  28  may issue control signals on one or more paths such as path  108  that adjust inductance values, capacitance values, or other parameters associated with tunable components  102 , thereby tuning antenna structures  40  to cover desired communications bands. Active and/or passive components may also be used to allow antenna structures  40  to be shared between non-near-field communications transceiver circuitry  90  and near-field communications transceiver circuitry  44 . Near-field communications and non-near-field communications may also be handled using two or more separate antennas, if desired. 
     Path  92  may include one or more transmission lines. As an example, signal path  92  of  FIG. 3  may be a radio-frequency transmission line having a positive signal conductor such as line  94  and a ground signal conductor such as line  96 . Transmission line structures used to form path  92  (sometimes referred to herein as transmission lines  92 ) may include parts of a coaxial cable, a stripline transmission line, microstrip transmission line, coaxial probes realized by metalized vias, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, waveguide structures, transmission lines formed from combinations of transmission lines of these types, etc. Transmission lines in device  10  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, transmission lines in device  10  may also include transmission line conductors (e.g., signal and ground conductors) 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) that may be folded or bent in multiple dimensions (e.g., two or three dimensions) and that 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  102 ) may include components such as inductors, resistors, and capacitors used in matching the impedance of antenna(s)  40  to the impedance of transmission line  92 . Matching network components may be provided as discrete components (e.g., surface mount technology components) or may be formed from housing structures, printed circuit board structures, traces on plastic supports, etc. Components such as these may also be used in forming filter circuitry in antenna(s)  40  and may be tunable and/or fixed components. 
     Transmission line  92  may be coupled to antenna feed structures associated with antenna structures  40 . As an example, antenna structures  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed  112  with a positive antenna feed terminal such as terminal  98  and a ground antenna feed terminal such as ground antenna feed terminal  100 . Positive transmission line conductor  94  may be coupled to positive antenna feed terminal  98  and ground transmission line conductor  96  may be coupled to ground antenna feed terminal  100 . Other types of antenna feed arrangements may be used if desired. For example, antenna structures  40  may be fed using multiple feeds. The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     If desired, control circuitry  28  may use an impedance measurement circuit to gather antenna impedance information. Control circuitry  28  may use information from a proximity sensor (see, e.g., sensors  32  of  FIG. 2 ), received signal strength information, device orientation information from an orientation sensor, information about a usage scenario of device  10 , information about whether audio is being played through speaker  26 , information from one or more antenna impedance sensors, or other information in determining when antenna  40  is being affected by the presence of nearby external objects or is otherwise in need of tuning. In response, control circuitry  28  may adjust an adjustable inductor, adjustable capacitor, switch, or other tunable component  102  to ensure that antenna  40  operates as desired. Adjustments to component  102  may also be made to extend the coverage of antenna  40  (e.g., to cover desired communications bands that extend over a range of frequencies larger than antenna  40  would cover without tuning). 
     Antenna structures  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  112 , and other components (e.g., tunable components  102 ). Antenna structures  40  may be configured to form any suitable types of antenna. With one suitable arrangement, which is sometimes described herein as an example, antenna structures  40  are 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 non-near-field communications transceiver circuitry  90  over respective transmission lines  92 . If desired, two or more antennas  40  may share the same transmission lines  92 .  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 location within housing  12 . 
     Wireless circuitry  34  may include input-output ports such as port  122  for interfacing with digital data circuits in storage and processing circuitry (e.g., storage and processing circuitry  28  of  FIG. 1 ). Wireless circuitry  34  may include baseband circuitry such as baseband (BB) processor  120  and radio-frequency transceiver circuitry such as non-near-field communications transceiver circuitry  90 . 
     Port  122  may receive digital data from storage and processing circuitry that is to be transmitted by non-near-field communications transceiver circuitry  90 . Incoming data that has been received by non-near-field communications transceiver circuitry  90  and baseband processor  120  may be supplied to storage and processing circuitry via port  122 . 
     Non-near-field communications transceiver circuitry  90  may include one or more transmitters and one or more receivers. For example, transceiver circuitry  90  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  92  (e.g., a first transmission line  92 - 1 , a second transmission line  92 - 2 , a third transmission line  92 - 3 , and a fourth transmission line  92 - 4 ). For example, first transceiver  38 - 1  may be coupled to antenna  40 - 1  over transmission line  92 - 1 , second transceiver  38 - 2  may be coupled to antenna  40 - 2  over transmission line  92 - 2 , third transceiver  38 - 3  may be coupled to antenna  40 - 3  over transmission line  92 - 3 , and fourth transceiver  38 - 4  may be coupled to antenna  40 - 4  over transmission line  92 - 4 . 
     Radio-frequency front end circuits  128  may be interposed on each transmission line  92  (e.g., a first front end circuit  128 - 1  may be interposed on line  92 - 1 , a second front end circuit  128 - 2  may be interposed on line  92 - 2 , a third front end circuit  128 - 3  may be interposed on line  92 - 3 , etc.). Front end circuits  128  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 line  92  to the corresponding antenna  40 , networks of active and/or passive components such as components  102  of  FIG. 3 , radio-frequency coupler circuitry for gathering antenna impedance measurements, or any other desired radio-frequency circuitry. If desired, front end circuits  128  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  128 ). 
     If desired, front end circuits  128  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  92  and/or formed within non-near-field communications transceiver circuitry  90  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  92  and/or formed within non-near-field communications transceiver circuitry  90  for amplifying radio-frequency signals received by antennas  40  prior to conveying the received signals to transceivers  38 . 
     In the example of  FIG. 3 , separate front end circuits  128  are formed on each transmission line  92 . This is merely illustrative. If desired, two or more transmission lines  92  may share the same front end circuits  128  (e.g., front end circuits  128  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  120  over path  124  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 paths  92  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  120  over paths  124 . 
     Each transceiver  38  may be formed on the same substrate, integrated circuit, or module (e.g., non-near-field communications transceiver circuitry  90  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 circuitry  120  and front end circuits  128  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, non-near-field communications transceiver circuitry  90  may include a single transceiver  38  having four ports, each of which is coupled to a respective transmission line  92 , 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 low band between 700 and 960 MHz, a second frequency band such as a midband between 1700 and 2200 MHz, and a third frequency band such as a high band between 2300 and 2700 MHz. Transceiver  38 - 2 , antenna  40 - 2 , transceiver  38 - 3 , and antenna  40 - 3  may handle radio-frequency signals in the second frequency band between 1700 and 2200 MHz and the third frequency band between 2300 and 2700 MHz (e.g., antennas  40 - 2  and  40 - 3  may not occupy sufficient volume to support signals within the low band). 
     The example of  FIG. 4  is merely illustrative. In general, antennas  40  may cover any desired frequency bands. Non-near-field communications transceiver circuitry  90  may include other transceiver circuits such as one or more circuits  36  or  42  of  FIG. 2  coupled to one or more antennas  40 . Housing  12  may have any desired shape. 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 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 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 circuitry  34 . 
     However, if care is not taken, radio-frequency signals conveyed in the same frequency band by multiple antennas  40  may interfere with each other, serving to deteriorate the overall wireless performance of circuitry  34 . Ensuring that antennas operating at the same frequency are electromagnetically isolated from each other can be particularly challenging for adjacent antennas  40  (e.g., antennas  40 - 1  and  40 - 2 , antennas  40 - 3  and  40 - 4 , etc.) and for antennas  40  that have common (shared) structures (e.g., that have resonating elements formed from adjacent or shared conductive portions of housing  12 ). 
     In order to perform wireless communications under a MIMO scheme, antennas  40  need to convey data at the same frequencies. If desired, wireless 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 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 low band (LB) 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 midband (MB) between 1700 and 2200 MHz and/or at the same frequency in a 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). 
     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  66  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  68  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 circuitry  34  may perform 2×MIMO operations using antennas  40 U and  40 L in one, two, or each of the low band, midband, and high band, for example. If desired, control circuitry  28  may toggle the switching circuitry over time to switch wireless circuitry  34  between a first mode in which antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  perform 2×MIMO operations in the low band and 4×MIMO operations in the midband and/or high band 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 the low band, midband, and/or high band. 
     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 (e.g., a frequency in low band LB), from a second wireless base station at a second frequency (e.g., a frequency in midband MB), and a from a third base station at a third frequency (e.g., a frequency in high band HB). 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 . If desired, antenna  40 - 1  may convey radio-frequency signals with more than three base stations (e.g., using more than one frequency in low band LB, midband MB, and/or high band HB). Similarly, antenna  40 - 4  may perform carrier aggregation at two, three, or more than three frequencies within bands LB, MB, and/or HB, and antennas  40 - 2  and  40 - 3  may perform carrier aggregation at two or more frequencies within bands MB and/or HB. This may serve to further increase the overall data throughput of wireless 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 (e.g., each carrier frequency within bands LB, MB, and HB) 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 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 circuitry  34 ). As one example, antennas  40 - 1  and  40 - 4  may perform carrier aggregation across three frequencies within each of bands LB, MB, and HB and antennas  40 - 3  and  40 - 4  may perform carrier aggregation across three frequencies within each of bands MB and HB. At the same time, antennas  40 - 1  and  40 - 4  may perform 2×MIMO operations in low band LB using and antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 4×MIMO operations in one of bands MB and HB. In this scenario, with an exemplary throughput of 40 Mb/s per carrier frequency, wireless circuitry  34  may exhibit a throughput of approximately 960 Mb/s. If 4× MIMO operations are performed in both bands MB and HB by antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 , circuitry  34  may exhibit an even greater throughput of approximately 1200 Mb/s. In other words, the data throughput of wireless 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 . Inverted-F antenna structure  40  of  FIG. 5  has antenna resonating element  130  (sometimes referred to herein as antenna radiating element  130 ) and antenna ground  136  (sometimes referred to herein as ground plane  136  or ground  136 ). Antenna resonating element  130  may have a main resonating element arm such as arm  132 . The length of arm  132  may be selected so that antenna structure  40  resonates at desired operating frequencies. For example, the length of arm  132  (or a branch of arm  132 ) may be a quarter of a wavelength at a desired operating frequency for antenna  40 . Antenna structure  40  may also exhibit resonances at harmonic frequencies. If desired, slot antenna structures or other antenna structures may be incorporated into an inverted-F antenna such as antenna  40  of  FIG. 5  (e.g., to enhance antenna response in one or more communications bands). 
     Main resonating element arm  132  may be coupled to ground  136  by return path  134 . Antenna feed  112  may include positive antenna feed terminal  98  and ground antenna feed terminal  100  and may run parallel to return path  134  between arm  132  and ground  136 . If desired, inverted-F antenna structures such as illustrative antenna structure  40  of  FIG. 5  may have more than one resonating arm branch (e.g., to create multiple frequency resonances to support operations in multiple communications bands) or may have other antenna structures (e.g., parasitic antenna resonating elements, tunable components to support antenna tuning, etc.). For example, arm  132  may have left and right branches that extend outwardly from feed  112  and return path  134 . Multiple feeds may be used to feed antennas such as antenna  40 . Arm  132  may follow any desired path having any desired shape (e.g., curved and/or straight paths, meandering paths, etc.). If desired, antennas such as inverted-F antenna  40  of  FIG. 5  may include tunable components such as components  102  of  FIG. 3  (e.g., coupled between different portions of arm  132 , between arm  132  and ground  136 , etc.). 
     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  140  that is formed within conductive structures such as antenna ground  136 . Slot  140  may be filled with air, plastic, and/or other dielectric. The shape of slot  140  may be straight or may have one or more bends (i.e., slot  140  may have an elongated shape following a meandering path). Feed terminals  98  and  100  may, for example, be located on opposing sides of slot  140  (e.g., on opposing long sides). Slot  140  may sometimes be referred to herein as slot element  140 , slot antenna resonating element  140 , slot antenna radiating element  140 , or slot  140 . Slot-based antenna resonating elements such as slot element  140  of  FIG. 7  may give rise to an antenna resonance at frequencies in which the wavelength of the antenna signals is equal to the perimeter of the slot. In narrow slots, the resonant frequency of a slot antenna resonating element is associated with signal frequencies at which the slot length is approximately equal to a half of a wavelength of operation. 
     Slot antenna frequency response can be tuned using one or more tuning components (e.g., components  102  of  FIG. 3 ). These components may have terminals that are coupled to opposing sides of the slot (i.e., the tunable components may bridge the slot). If desired, tunable components may have terminals that are coupled to respective locations along the length of one of the sides of slot  140 . 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 arm  132  of  FIG. 5  and a slot such as slot  140  of  FIG. 6 ). 
     The example of  FIG. 6  is merely illustrative. In general, slot  140  may have any desired shape (e.g., shapes with straight and/or curved edges), may follow a meandering path, etc. If desired, slot  140  may be an open slot having one or more ends that are free from conductive material (e.g., where slot  140  extends through one or more sides of ground  136 ). Slot  140  may, for example, have a length approximately equal to one-quarter of the wavelength of operation in these scenarios. 
     While the examples of  FIGS. 5 and 6  show only a single antenna  40 , multiple antennas  40  may be formed from these structures within device  10 . A top interior view of an illustrative portion of device  10  that contains antennas  40 - 1  and  40 - 2  is shown in  FIG. 7 . As shown in  FIG. 7 , device  10  may have peripheral conductive housing structures such as peripheral conductive housing structures  16 . Peripheral conductive housing structures  16  may be segmented by dielectric-filled gaps (e.g., plastic gaps)  18  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 . 
     As shown in  FIG. 7 , antennas  40 - 1  and  40 - 2  may include inverted-F antenna structures (e.g., inverted-F antenna structures as shown in  FIG. 5 ). Antenna  40 - 1  may include a resonating element arm  132 - 1  coupled to ground  136  by return path  134 - 1 . Antenna  40 - 1  may be fed using a first antenna feed  112 - 1 . Antenna feed  112 - 1  may have a positive antenna feed terminal  98 - 1  coupled to point  192  on resonating element arm  132 - 1  and a ground antenna feed terminal  100 - 1  coupled to ground  136 . Antenna  40 - 2  may include a resonating element arm  132 - 2  coupled to ground  136  by return path  134 - 2 . Antenna  40 - 2  may be fed using a second antenna feed  112 - 2  having a positive antenna feed terminal  98 - 2  coupled to resonating element arm  132 - 2  and a ground antenna feed terminal  100 - 2  coupled to ground  136 . 
     In the example of  FIG. 8 , return path  134 - 1  of antenna  40 - 1  may be coupled between point  190  on resonating element arm  132 - 1  and point  198  on ground  136 . Point  190  may be interposed between point  192  and gap  18 - 1 . Point  192  may be interposed between point  190  and gap  18 - 3 . Point  198  on ground  136  may be interposed between ground feed terminal  100 - 1  and gap  18 - 1 . Similarly, feed terminal  98 - 2  of antenna  40 - 2  may be coupled to resonating element arm  132 - 2  of antenna  40 - 2  at a location between gaps  18 - 3  and  18 - 2 . Return path  134 - 2  of antenna  40 - 2  may be formed at gap  18 - 3  or may be coupled to a location along arm  132 - 2  that is interposed between gap  18 - 3  and feed terminal  98 - 1 . Return path  134 - 2  may be coupled to point  196  on ground  136 . Ground feed terminal  100 - 2  may be interposed between point  196  on ground  136  and gap  18 - 2 . 
     Radio-frequency signals may be conveyed to and from antenna  40 - 1  over feed  112 - 1 . Feed  112 - 1  may be coupled to non-near-field communications transceiver (TX/RX) circuitry  90  over transmission line  92 - 1 . For example, positive conductor  94 - 1  of transmission line  92 - 1  may be coupled to feed terminal  98 - 1  whereas ground conductor  96 - 1  of transmission line  92 - 1  may be coupled to feed terminal  100 - 1 . If desired, matching circuitry (e.g., impedance matching circuitry in a front end circuit such as front end circuit  128 - 1  of  FIG. 4 ) may be interposed on transmission line  92 - 1 . 
     Radio-frequency signals may be conveyed to and from antenna  40 - 2  over feed  112 - 2 . Feed  112 - 2  may be coupled to non-near-field communications transceiver (TX/RX) circuitry  90  over transmission line  92 - 2  (e.g., transmission lines  92 - 1  and  92 - 2  may be coupled to respective ports on transceiver circuitry  90  or may be coupled to separate transceivers such as transceivers  38 - 1  and  38 - 2  as shown in  FIG. 4 ). For example, positive conductor  94 - 2  of transmission line  92 - 2  may be coupled to feed terminal  98 - 2  whereas ground conductor  96 - 2  of transmission line  92 - 2  may be coupled to feed terminal  100 - 2 . If desired, matching circuitry (e.g., impedance matching circuitry in a front end circuit such as front end circuit  128 - 2  of  FIG. 4 ) may be interposed on transmission line  92 - 2 . 
     An opening such as slot  140  may separate arms  132 - 1  and  132 - 2  from ground  136 . If desired, slot  140  may contribute slot antenna resonances to antennas  40 - 1  and/or  40 - 2  (e.g., antennas  40 - 1  and  40 - 2  may be hybrid slot-inverted-F antennas including resonating elements of the types shown in both  FIGS. 5 and 6 ). 
     Slot  140  may be formed from an elongated opening extending from gap  18 - 1  to gap  18 - 2  (e.g., the ends of slot  140 , which may sometimes be referred to as open ends, may be formed by gaps  18 - 1  and  18 - 2 ). Slot  140  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  140  along the longitudinal axis of slot  140 . Slot  140  may be filled with dielectric such as air, plastic, ceramic, or glass. For example, plastic may be inserted into portions of slot  140  and this plastic may be flush with the outside of housing  12 . Dielectric material in slot  140  may lie flush with dielectric material in gaps  18 - 1 ,  18 - 2 , and  18 - 3  at the outside of housing  12  if desired. The example of  FIG. 7  is merely illustrative. If desired, slot  140  may have any other desired shapes (e.g., a U-shape having segments extending along three sides of device  10  and surrounding an extended portion of ground  136 , shapes having curved and/or straight edges, etc.). 
     As shown in  FIG. 7 , resonating element arm  132 - 1  of antenna  40 - 1  and resonating element arm  132 - 2  of antenna  40 - 2  may be formed from respective segments of peripheral conductive housing structures  16 . The segment of peripheral conductive housing structures  16  forming resonating element arm  132 - 1  may extend between dielectric gap  18 - 1  at a first (left) side of device  10  and third dielectric gap  18 - 3  at a second (top) side of device  10 . The segment of peripheral conductive housing structures  16  forming resonating element arm  132 - 2  may extend between dielectric gap  18 - 3  and dielectric gap  18 - 2  at a third second (right) side of device  10 . 
     Antenna ground  136  may be formed from conductive housing structures, from electrical device components in device  10 , from printed circuit board traces, from strips of conductor such as strips of wire and metal foil, from conductive portions of display  14  (e.g., a conductive frame for display  14  or a conductive back panel for display  14 ), and/or other conductive structures. In one suitable arrangement, ground  136  is formed from conductive portions of housing  12  such as conductive housing layer  150  and the segments of peripheral conductive housing structures  16  that are separated from arm  132 - 1  by peripheral gap  18 - 1  and from arm  132 - 2  by peripheral gap  18 - 2 . Conductive housing layer  150  may form the conductive rear wall of device  10 , as an example. Conductive housing layer  150  may form an exterior surface of device  10  or may be covered with (e.g., formed over) a thin dielectric layer such as a glass, sapphire, plastic, or ceramic layer that covers conductive housing layer  150  and serves to hide layer  150  from view (e.g., where the dielectric layer forms the exterior surface of device  10 ). 
     Conductive housing layer  150  (sometimes referred to herein as ground layer  150  or conductive layer  150 ) may have any desired shape within device  10 . For example, ground layer  150  may align with gaps  18 - 1  and  18 - 2  in peripheral conductive hosing structures  16  (e.g., the lower edge of gap  18 - 1  may be aligned with the edge of ground layer  150  defining slot  140  adjacent to gap  18 - 1  such that the lower edge of gap  18 - 1  is approximately collinear with the edge of ground layer  150  at the interface between ground layer  150  and the portion of peripheral conductive structures  16  adjacent to gap  18 - 1 ). This example is merely illustrative and, in another suitable arrangement, ground layer  150  may have an additional vertical slot adjacent to gap  18 - 1  that extends below gap  18 - 1  (e.g., along the Y-axis of  FIG. 7 ). Similarly, if desired, ground layer  150  may include a vertical slot adjacent to gap  18 - 2  that extends beyond the lower edge of gap  18 - 2  (e.g., in the direction of the Y-axis of  FIG. 7 ). Such vertical slots may, for example, have two edges that are defined by ground layer  150  and one edge that is defined by peripheral conductive structures  16 . The vertical slots may have open ends defined by an open end of slot  140  at gaps  18 - 2  and  18 - 1 . The vertical slots may have any desired length extending beyond gaps  18 - 1  and  18 - 2  along the Y-axis of  FIG. 7  (e.g., 10-15 mm, more than 5 mm, more than 10 mm, more than 15 mm, more than 30 mm, less than 30 mm, less than 20 mm, less than 15 mm, less than 10 mm, between 5 and 20 mm, etc.) and may have any desired perpendicular width (e.g., about 2 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, more than 0.5 mm, more than 1.5 mm, more than 2.5 mm, 1-3 mm, etc.). 
     The length of antenna resonating element arms  132 - 1  and  132 - 2  may be selected so that antennas  40 - 1  and  40 - 2  resonate at desired frequencies such as frequencies in a low band LB (e.g., a frequency band between about 600 MHz and 960 MHz), in a midband MB (e.g., a frequency band between about 1700 MHz and 2200 MHz), and a high band HB (e.g., a frequency and between about 2300 MHz and 2700 MHz). 
     In one suitable arrangement, the frequency response of antenna  40 - 1  in midband MB may be associated with the distance along arm  132 - 1  between return path  134 - 1  and feed  112 - 1 . The frequency response of antenna  40 - 1  in low band LB may be associated with the distance along arm  132 - 1  between feed  112 - 1  and gap  18 - 3 , for example. The frequency response of antenna  40 - 2  in midband MB may be associated with the distance along arm  132 - 2  between return path  134 - 2  and gap  18 - 2 , for example. A portion of slot  140  between arm  132 - 1  and ground  136  and/or harmonics of arm  132 - 1  may contribute to the frequency response of antenna  40 - 1  in high band HB. A portion of slot  140  between arm  132 - 2  and ground  136  and/or harmonics of arm  132 - 2  may contribute to the frequency response of antenna  40 - 2  in high band HB. 
     Antenna tuning components (e.g., components  102  of  FIG. 3 ) may be coupled to antenna  40 - 1 . For example, an inductive component such as adjustable inductor  172  may be interposed in return path  134 - 1  between arm  132 - 1  and ground  136 . Adjustable inductor  172  may, for example, be controlled to adjust the frequency response of antenna  40 - 1  in midband MB and/or high band HB (e.g., using control signals provided by control circuitry  28  as shown in  FIG. 3 ). In this example, adjustable inductor  172  may include a set of fixed inductors coupled to ground  136  by switching circuitry. For example, adjustable inductor  172  may include a single fixed inductor coupled to ground  136  by a single-pole single-throw (SPST) switch or may include multiple fixed inductors coupled to ground  136  by a single-pole double-throw (SP2T) switch. This example is merely illustrative and, if desired, inductor  172  may be fixed. 
     Antenna  40 - 1  may have an additional return path  134 - 3  coupled between point  200  on arm  132 - 1  and point  202  on ground  136 . Point  200  may, for example, be interposed between point  192  and gap  18 - 3 . Point  202  may be interposed between ground terminal  100 - 1  and point  196 . A filter such as a frequency-dependent circuit based on capacitor  204  (e.g., a capacitor having a capacitance of about 20-30 pF) may be interposed on return path  134 - 3 . An inductive circuit such as adjustable inductor  206  may be interposed on return path  134 - 3  between capacitor  204  and ground  136 . Adjustable inductor  206  may, for example, include a set of fixed inductors coupled between capacitor  204  and point  202  by switching circuitry such as a single-pole four-throw (SP4T) switch. The switch may be adjusted to change the inductance coupled between points  200  and  202  to tune the frequency response of antenna  40 - 1  in low band LB. 
     If desired, antenna tuning components (e.g., components  102  of  FIG. 3 ) may be coupled between arm  132 - 2  and ground  136  for adjusting the frequency response of antenna  40 - 2  in midband MB and/or high band HB. For example, adjustable inductor circuitry or other circuitry may be interposed in return path  134 - 2 . The example of  FIG. 7  is merely illustrative. In general, any desired adjustable tuning components having any desired switching circuitry, resistive, capacitive, and/or inductive components may be included in antennas  40 - 1  and  40 - 2 . 
     When configured in this way, both antennas  40 - 1  and  40 - 2  may support communications in midband MB and high band HB whereas antenna  40 - 1  also supports communications in low band LB. Antennas  40 - 1  and  40 - 2  may therefore both perform communications using a MIMO scheme in midband MB and/or high band HB, if desired (e.g., a 2×MIMO scheme in midband MB and/or high band HB using only antennas  40 - 1  and  40 - 2  or a 4×MIMO scheme in midband MB and/or high band HB together with antennas  40 - 3  and  40 - 4  of  FIG. 3 ). When performing MIMO operations (e.g., 4×MIMO operations) within the same frequency band (e.g., within midband MB or high band HB), if care is not taken, antenna currents from antenna  40 - 1  can electromagnetically interact with antenna currents from antenna  40 - 2 , thereby deteriorating radio-frequency performance by both antennas. 
     However, as shown in  FIG. 7 , the mechanical separation between arms  132 - 1  and  132 - 2  provided by gap  18 - 3  may serve to electromagnetically isolate antenna  40 - 1  from antenna  40 - 2  when antennas  40  operate at the same frequency (e.g., while performing communications using a MIMO scheme). Forming return path  134 - 2  adjacent to gap  18 - 3  may serve to further isolate arms  132 - 1  and  132 - 2 . In this way, antenna  40 - 1  may be sufficiently isolated from antenna  40 - 2  despite both antennas operating at the same frequencies. At the same time, antenna  40 - 1  may, if desired, perform 2×MIMO operations in low band LB with other antennas in device  10  (e.g., with antenna  40 - 4  as shown in  FIG. 3 ). While the example of  FIG. 7  describes adjacent antennas  40 - 1  and  40 - 2 , similar antenna structures may be used in forming antennas  40 - 3  and  40 - 4  at the lower end of device  10  as shown in  FIG. 4  (e.g., where antenna  40 - 4  replaces antenna  40 - 1  and antenna  40 - 3  replaces antenna  40 - 2  in  FIG. 7 ). 
     To support near-field communications in device  10 , device  10  preferably includes a near-field communications antenna. Space can be conserved by using some or all of antennas  40 - 1  and/or  40 - 2  as both a cellular telephone antenna or other non-near-field communications antenna and as a near-field communications antenna. As an example, a near-field communications antenna for device  10  (e.g., an antenna that is used by near-field communications transceiver circuitry  44 ) may be formed using portions of antenna  40 - 1  of  FIG. 7  such as portions of resonating element arm  132 - 1 , return path  134 - 1 , and ground  136 . By sharing conductive antenna structures between both near-field and non-near-field antennas, duplicative conductive structures can be minimized and antenna volume can be conserved within device  10 . 
     As shown in  FIG. 7 , a near-field communications antenna for device  10  may be formed from antenna  40 - 1  such as portions of inverted-F antenna resonating element arm  132 - 1 , return path  134 - 1 , and ground  136 . The non-near-field communications antenna formed from antenna  40 - 1  may be fed using an antenna feed such as feed  112 - 1 . Non-near-field communications transceiver circuitry  90  may handle wireless communications using feed  112 - 1  in frequency bands such as low band LB, midband MB, high band HB, a low-midband from 960 to 1710 MHz, an ultra-high band from 3400 to 3700 MHz, 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications, a 1575 MHz band for GPS signals, and/or other non-near-field communications bands. 
     In order to support near-field communications using antenna  40 - 1 , near-field communications transceiver circuitry  44  (NFC TX/RX) may transmit and/or receive near-field communications signals (e.g., signals in a near-field communications band such as a 13.56 MHz near-field communications band). Near-field communications transceiver circuitry  44  may be coupled to antenna  40 - 1  using a conductive path such as path  154 . Path  154  may be coupled to point  194  on arm  132 - 1 . Point  194  may be interposed between point  192  and gap  18 - 3 . Path  154  may, for example, be a single-ended transmission line signal path for conveying single-ended near-field communications signals. In this scenario, near-field communications transceiver circuitry  44  may include balun circuitry or other circuitry for converting the single-ended signals into differential signals and for converting differential signals into the single-ended signals. 
     A filter such as a frequency-dependent circuit based on inductor  156  (e.g., an inductor having a value of 80 nH to 200 nH) or other suitable frequency-dependent circuit may couple arm  132 - 1  of antenna  40 - 1  to near-field communications transceiver circuitry  44 . If desired, impedance matching circuitry may be interposed between inductor  156  and the balun in circuitry  44  or the balun in circuitry  44  may be interposed between inductor  156  and impedance matching circuitry. 
     A filter such as a frequency-dependent circuit based on capacitor  152  (e.g., a capacitor having a capacitance of about 20-30 pF) may be coupled between feed terminal  98 - 1  and point  192  on arm  132 - 1 . The frequencies of the signals associated with non-near-field communications transceiver circuitry  90  are typically 600 MHz or greater. At these frequencies, inductor  156  forms an open circuit that electrically isolates arm  132 - 1  and antenna  40 - 1  from near-field communications transceiver circuitry  44 . Capacitor  152  may form a short circuit at these frequencies, so that feed terminal  98 - 1  is coupled to arm  132 - 1  and antenna  40 - 1  serves as an inverted-F antenna for non-near-field communications transceiver circuitry  90 . Capacitor  204  may also form a short circuit at these frequencies so that point  200  is coupled to point  202  and adjustable inductor  206  can perform frequency adjustments for antenna  40 - 1  in low band LB. 
     Near-field communications transceiver circuitry  44  may operate at lower frequencies (e.g., at 13.56 MHz). At near-field communications frequencies, capacitor  152  forms an open circuit, isolating the path containing capacitor  152  (i.e., feed terminal  98 - 1 ) from near-field communications signal currents. Similarly, capacitor  204  forms an open circuit at these frequencies, isolating point  202  from point  200 . Inductor  156  may form a short circuit at near-field communications frequencies, so near-field communications signal currents such as illustrative near-field communications current  170  can flow through a conductive path formed from portions of antenna  40 - 1  (e.g., a conductive loop path that forms a loop antenna resonating element of a near-field communications loop antenna). Current  170  may, for example, flow in a loop through path  154 , the portion of arm  132 - 1  between points  194  and  190 , return path  134 - 1 , and ground  136 . Current  170  may be isolated from arm  132 - 2  and return path  134 - 2  of antenna  40  by gap  18 - 3  in peripheral conductive structures  16 . Current  170  may produce corresponding wireless near-field communications signals that are transmitted by device  10  and/or may be produced in response to wireless near-field communications signals that are received by device  10 , for example. 
     As this example demonstrates, the antenna structures for antenna  40 - 1  of  FIG. 7  can serve both as non-near-field communications antenna structures (i.e., an inverted-F antenna) and as near-field communications antenna structures (i.e., a loop antenna formed from portions of antenna structures  40 - 1 ). The ability to share antenna structures between both near-field and non-near-field functions allows the size of the antennas in device  10  to be minimized and avoids duplication of antenna parts. 
     The example of  FIG. 7  is merely illustrative. If desired, near-field communications transceiver circuitry  44  may be coupled to antenna  40 - 2  and portions of antenna  40 - 2  may form a near-field communications loop antenna. However, in general, it may be desirable for the near-field communications loop antenna to occupy as much space as possible (e.g., as much of the width of device  10  along the X-axis of  FIG. 7  as possible). This may, for example, facilitate the use of device  10  for a user who is using device  10  to communicate with external near-field communications equipment such as an RFID reader (e.g., so that the user does not have to focus on precisely placing device  10  over the RFID reader so that the antenna volume is aligned with the RFID reader). Because antenna  40 - 2  occupies less volume than antenna  40 - 1  (e.g., because antenna  40 - 2  does not cover low band LB), forming a near-field communications loop from antenna  40 - 2  may undesirably increase the difficulty of operating device  10  for a user. If desired, even more of the width of device  10  may be utilized in forming the near-field communications loop antenna by forming the near-field communications loop antenna using portions of both antennas  40 - 1  and  40 - 2 . 
       FIG. 8  is a top-down diagram of device  10  having a near-field communications antenna formed from portions of both antennas  40 - 1  and  40 - 2 . As shown in  FIG. 8 , feed terminal  98 - 2  of feed  112 - 2  may be coupled to point  222  on arm  132 - 2 . Point  222  may be interposed between gaps  18 - 3  and  18 - 2 . A filter such as a frequency-dependent circuit based on capacitor  220  (e.g., a capacitor having a capacitance of about 20-30 pF) may be interposed between feed terminal  98 - 2  and point  222  on arm  132 - 2 . If desired, an impedance matching circuit such as matching (M) circuit  223  may be interposed between feed terminal  98 - 2  and capacitor  220 . Matching circuit  223  may serve to match the impedance of the transmission line for antenna  40 - 2  (e.g., transmission line  92 - 2  as shown in  FIGS. 4 and 7 ) to the impedance of antenna  40 - 2  at non-near-field communications frequencies. 
     A filter such as a frequency-dependent circuit based on capacitor  216  (e.g., a capacitor having a capacitance of about 20-30 pF) may be interposed on return path  134 - 2  of antenna  40 - 2 . Capacitor  216  may be coupled to point  210  on arm  132 - 2  through circuit node  221 . Point  210  may be located at the edge of gap  18 - 3 , may be adjacent to gap  18 - 3 , or may be at any other desired location between gap  18 - 3  and point  222 . 
     Near-field communications transceiver circuitry  44  may be coupled to peripheral conductive structures  16  using a conductive path such as path  226 . Path  226  may be coupled to point  222  on arm  132 - 1 . This is merely illustrative and, in other suitable arrangements, path  226  may be coupled to other desired locations on arm  132 - 2  (e.g., feed  112 - 1  and path  226  need not be coupled to the same point on arm  132 - 2 ). Path  226  may, for example, be a single-ended transmission line signal path for conveying single-ended near-field communications signals. In this scenario, near-field communications transceiver circuitry  44  may include balun circuitry or other circuitry for converting the single-ended signals into differential signals and for converting differential signals into the single-ended signals. 
     A filter such as a frequency-dependent circuit based on inductor  224  (e.g., an inductor having a value of 80 nH to 200 nH) or other suitable frequency-dependent circuit may couple arm  132 - 2  of antenna  40 - 2  to near-field communications transceiver circuitry  44 . If desired, impedance matching circuitry such as impedance matching circuitry  225  may be interposed between inductor  224  and the balun in circuitry  44 . In another suitable arrangement, the balun in circuitry  44  may be interposed between inductor  224  and impedance matching circuitry  225 . Impedance matching circuitry  225  may ensure that path  226  and circuitry  44  is impedance matched to antenna  40 - 2  at near-field communications frequencies. 
     If desired, an optional filter such as a frequency-dependent circuit based on capacitor  248  (e.g., a capacitor having a capacitance value of 20-30 pF) or other suitable frequency-dependent circuit may couple path  226  to point  246  on ground  136 . Capacitor  248  may, for example, be coupled to a point on path  226  that is interposed between inductor  224  and near-field communications transceiver circuitry  44  (e.g., capacitor  248  may be coupled to the side of inductor  224  coupled to near-field communications transceiver circuitry  44 ). 
     In order to maximize the volume of the near-field communications loop antenna for device  10 , arm  132 - 1  of antenna  40 - 1  may be coupled to arm  132 - 2  of antenna  40 - 2  by a conductive path bridging gap  18 - 3 . For example, a filter such as a frequency-dependent circuit based on inductor  212  (e.g., an inductor having a value of 80 nH to 200 nH) or other suitable frequency-dependent circuit may couple arm  132 - 1  of antenna  40 - 1  to arm  132 - 2  of antenna  40 - 2  (e.g., inductor  212  may bridge gap  18 - 3  and may couple the end of arm  132 - 1  adjacent to gap  18 - 3  to the end of arm  132 - 2  adjacent to gap  18 - 3 ). In one suitable arrangement, inductor  212  may be coupled between point  208  on arm  132 - 1  and circuit node  221 . Point  208  may be located at the edge of arm  132 - 1  defined by gap  18 - 3 , may be located adjacent to gap  18 - 3 , or may be located at any desired point between point  200  and gap  18 - 3 . Inductor  212  may be coupled directly to node  210  or to a point on arm  132 - 2  between point  210  and edge  18 - 3  in other suitable arrangements. If desired, an additional inductor may be interposed on return path  134 - 2  between point  210  and circuit node  221  (e.g., to ensure that antennas  40 - 1  and  40 - 2  are provided with desired impedance matching at near-field communications frequencies). 
     At the frequencies of the signals associated with antenna feeds  112 - 1  and  112 - 2  (e.g., non-near-field frequencies greater than 600 MHz associated with the non-near-field signals conveyed by non-near-field communications transceiver circuitry  90  of  FIG. 7 ), inductor  224  forms an open circuit that electrically isolates arm  132 - 2  and antenna  40 - 2  from near-field communications transceiver circuitry  44  and inductor  212  forms an open circuit that electrically isolates arm  132 - 2  of antenna  40 - 2  from arm  132 - 1  of antenna  401 . In this way, antennas  40 - 1  and  40 - 2  may be electromagnetically isolated by gap  18 - 3  at non-near-field communications frequencies. 
     Capacitors  152 ,  204 ,  216 , and  220  may form short circuits at these frequencies so that feed terminal  98 - 2  is coupled to arm  132 - 2  and antenna  40 - 2  serves as an inverted-F antenna for the non-near-field communications transceiver circuitry and so that feed terminal  98 - 1  is coupled to arm  132 - 1  and antenna  40 - 1  serves as an inverted-F antenna for the non-near-field communications transceiver circuitry. At these frequencies, capacitor  204  may electrically couple point  200  on arm  132 - 1  to point  202  on ground  136  (e.g., forming return path  134 - 3  and enabling inductor  206  to affect the non-near-field frequency response of antenna  40 - 1 ). Switching circuitry in adjustable inductor  206  may be adjusted to tune the frequency response of antenna  40 - 1  within low band LB. If desired, switching circuitry in adjustable inductor  172  may be adjusted to tune the frequency response of antenna  40 - 1  within midband MB and/or high band HB. At these non-near-field communications frequencies, capacitor  216  may short point  210  on arm  132 - 2  to point  196  on ground  136 , thereby shorting antenna currents at non-near-field communications frequencies to ground  136  over return path  134 - 2 . Switching circuitry in antenna  40 - 2  may be adjusted to tune the frequency response of antenna  40 - 2  within midband MB and/or high band HB if desired. 
     In scenarios where optional capacitor  248  is coupled between path  226  and ground  136 , inductor  224  may have a small enough inductance to pass non-near-field communications signals. Capacitor  248  may serve as a shunt capacitance that shorts non-near-field communications signals from point  222  to point  246  on ground  136 , thereby isolating near-field communications transceiver circuitry  44  from the non-near-field communications signals. In this scenario, antenna  40 - 2  may have an additional return path  134 - 4  formed by capacitor  248  and inductor  224  may perform impedance matching for antenna  40 - 2  at non-near-field communications frequencies. In another suitable arrangement, inductor  224  may include adjustable inductor circuitry that is adjusted to tune the frequency response of antenna  40 - 2  in midband MB and/or high band HB. 
     At near-field communications frequencies, capacitors  152 ,  204 ,  216 ,  220 , and  248  form open circuits. This may serve to isolate feed terminal  98 - 1 , low band tuning inductor  206 , and feed terminal  98 - 2  from near-field communications signal currents conveyed by near-field communications transceiver circuitry  44 . Similarly, signals at near-field communications frequencies may be prevented from shorting to ground point  202  over path  134 - 3 , from shorting to ground point  196  over return path  134 - 2 , and from shorting to ground point  246  over return path  134 - 4 . Inductors  172 ,  212 , and  224  may form short circuits at near-field communications frequencies. In this way, near-field communications signal currents such as illustrative near-field communications current  250  can flow through a conductive path formed from portions of both antennas  40 - 1  and  40 - 2  (e.g., a conductive loop path that forms a loop antenna resonating element of a near-field communications loop antenna for device  10 ). Current  250  may, for example, flow in a loop through conductive path  224 , the portion of arm  132 - 2  between points  222  and  210 , across gap  18 - 3  through inductor  212 , the portion of arm  132 - 1  between points  208  and  190 , through return path  134 - 1 , and through ground  136 . Current  250  may produce corresponding wireless near-field communications signals that are transmitted by device  10  and/or may be produced in response to wireless near-field communications signals that are received by device  10 , for example. 
     In this way, the near-field communications loop antenna formed by the conductive loop path of current  250  may extend across substantially all of the width of device  10  (e.g., across the lengths of both antennas  40 - 1  and  40 - 2 ). This may, for example, facilitate the use of device  10  for a user who is using device  10  to communicate with external near-field communications equipment such as an RFID reader (e.g., so that the user does not have to focus on precisely placing device  10  over the RFID reader so that the antenna volume is aligned with the RFID reader). At the same time, antennas  40 - 1  and  40 - 2  may handle radio-frequency communications at non-near-field communications frequencies in multiple bands (e.g., without the non-near-field communications signals interfering with near-field communications transceiver circuitry  44  or the near-field communications signals). Antennas  40 - 1  and  40 - 2  may, for example, perform MIMO communications at one or more of the same frequencies while maintaining satisfactory isolation between the antennas to maximize the data throughput of wireless communications circuitry  34 . 
     The example of  FIGS. 7 and 8  are merely illustrative. If desired, path  224  may be coupled to any desired location along arm  132 - 1  instead of a location along arm  132 - 2 . Arms  132 - 1  and  132 - 2  may have any desired shape (e.g., following straight and/or curved paths) and may have additional branches if desired. Slot  140  may have any other desired shapes (e.g., a U-shape having segments extending along three sides of device  10  and surrounding an extended portion of ground  136 , shapes having curved and/or straight edges, etc.). Point  190  may be interposed between points  192  and  200  or between points  200  and  208  if desired. Conductive path  226  may be coupled to arm  132 - 2  at a location between points  222  and  210  if desired. Point  222  may be interposed between gap  18 - 3  and point  210  if desired. While the example of  FIG. 8  describes antennas  40 - 1  and  40 - 2 , similar structures may be used to implement other antennas in device  10  if desired (e.g., antennas  40 - 3  and  40 - 4  of  FIG. 4 ). Antennas  40 - 1  and  40 - 2  may cover any desired frequency bands. In another suitable arrangement, the segment of peripheral housing structure  16  forming arm  132 - 1  may be continuous with the segment of peripheral housing structure  16  forming arm  132 - 2  (e.g., gap  18 - 3  may be omitted). In this scenario, an additional return path for antenna  40 - 1  may be coupled between point  208  and ground  136  to optimize isolation between antennas  40 - 1  and  40 - 2  if desired. 
       FIG. 9  is a graph in which non-near-field communications antenna performance (antenna efficiency) has been plotted as a function of operating frequency F for antennas  40 - 1  and  40 - 2  of  FIGS. 7 and 8 . As shown in  FIG. 9 , curve  267  plots the antenna efficiency of antenna  40 - 1  when operated at non-near-field communications frequencies. When operating at non-near-field communications frequencies, antenna  40 - 1  may exhibit peak efficiencies in low band LB, midband MB, and high band HB (e.g., peak efficiencies of approximately −3 dB). Curve  269  plots the antenna efficiency of antenna  40 - 2  when operating at non-near-field communications frequencies. When operating at non-near-field communications frequencies, antenna  40 - 2  may exhibit peak efficiencies in midband MB and high band HB. Antennas  40 - 1  and  40 - 2  may both exhibit satisfactory antenna efficiencies over the entirety of midband MB and high band HB even though antennas  40 - 1  and  40 - 2  both also form part of a near-field communications at near-field communications frequencies (e.g., due at least in part to the isolation provided by gap  18 - 3  of  FIG. 8 ). Antennas  40 - 1  and  40 - 2  may thereby perform MIMO operations at one or more frequencies in midband MB and/or high band HB in addition to performing near-field communications, if desired. 
       FIG. 10  is a circuit diagram of one possible adjustable circuit that may be used for tuning the non-near-field frequency response of antennas  40 - 1  and/or  40 - 2 . As shown in  FIG. 10 , wireless communications circuitry  34  may include an adjustable circuit  270  coupled between terminals  272  and  286 . Circuit node  276  may be coupled to terminal  272 . An inductor such as inductor  274  may be coupled between node  276  and terminal  286 . Fixed inductors such as inductors  280  and  282  may be coupled to terminal  286  via switching circuitry such as switch  284  (e.g., an SP2T switch or other desired switches). Capacitor  278  may be coupled to node  276 . Inductors  280  and  282  may be coupled in parallel between capacitor  278  and switch  284 . Switch  284  may be adjusted to selectively couple none, one, or both of inductors  280  and  282  between capacitor  278  and terminal  286 . 
     At near-field communications frequencies, capacitor  278  may form an open circuit. Inductor  274  may short terminal  272  to terminal  286  at near-field communications frequencies. If desired, inductor  274  may perform impedance matching for an antenna resonating element arm coupled to terminal  272  at non-near-field communications frequencies. 
     At non-near-field communications frequencies, capacitor  278  may form a short circuit between node  276  and inductors  280  and  282 . Inductor  274  may be configured to form an open circuit or a short circuit at non-near-field communications frequencies. Capacitor  278  may thereby serve to short non-near-field communications signals to terminal  286  over one or both of inductors  280  and  282  (e.g., depending on the state of switch  284 ). Switch  284  may be adjusted to change the inductance between terminals  272  and  286  and to thereby tune the frequency response of the antenna resonating element arm coupled to terminal  272  at non-near-field communications frequencies. In this way, an adjustable component such as component  270  may serve as both a short circuit path for near-field communication signals and as a tuning component for non-near-field communications antennas. 
     As examples, component  270  of  FIG. 10  may be used in place of adjustable inductor  172  of  FIGS. 7 and 8  (e.g., where terminal  272  of component  270  is coupled to point  190  on arm  132 - 1  and terminal  286  of component  270  is coupled to ground point  198  as shown in  FIG. 7 ), in place of return path  134 - 2  of  FIG. 7  (e.g., where terminal  272  is coupled to arm  132 - 2  of antenna  40 - 2  and terminal  286  is coupled to ground point  196  as shown in  FIG. 7 ), in place of return path  134 - 3  of  FIG. 8  (e.g., where terminal  272  is coupled to point  200  on arm  132 - 1  and terminal  286  is coupled to ground point  202  as shown in  FIG. 8 ), in place of inductor  224  of  FIG. 8  (e.g., where terminal  272  is coupled to point  222  on arm  132 - 2  and terminal  286  is coupled to ground  136 ), or at any other desired location in antennas  40 - 1  and/or  40 - 2 . The example of  FIG. 10  is merely illustrative. If desired, component  270  may include more than two inductors coupled to switch  284 . In general, component  270  may include any desired switches, inductors, and capacitors coupled in any desired manner between terminals  272  and  286 . 
     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: 20190201
Publication Date: 20200505
Grant Date: 20200505
Priority Date: 20170928
Inventors: IRCI, Erdinc
WANG, HAN
ATMATZAKIS, GEORGIOS
AYALA VAZQUEZ, ENRIQUE
TONG, ERICA J.
GAO, XU
HU, HONGFEI
JIN, NANBO
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q23/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/2258", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0413", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0413", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/242", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/521", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/50", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B5/0031", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0413", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/0056", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0249", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/48", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B5/48", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B5/77", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/72", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/77", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 65200291