PATENT DOCUMENT

Publication Number: US-10833410-B2
Application Number: US-201815902907-A
Country: US
Kind Code: B2

Title: Electronic device antennas having multiple signal feed terminals

Abstract:
An electronic device may include a conductive housing and an antenna. The antenna may include an arm formed from a first segment of the housing. A gap may separate the first segment from a second segment. Respective first and second slots may separate an antenna ground from the first and second segments. The antenna may have a first positive antenna feed terminal on the first segment and a second positive antenna feed terminal on the second segment. A transmission line may include a signal conductor having a first branch coupled to the first positive antenna feed terminal and a second branch coupled to the second positive antenna feed terminal. A switch may be interposed on the second branch for switching the antenna between a first mode in which the second slot is directly fed and a second mode in which the second segment is indirectly fed by the first segment.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a housing having peripheral conductive housing structures; 
 an antenna ground; 
 an antenna having an antenna resonating element arm formed from a segment of the peripheral conductive housing structures that is separated from the antenna ground by a dielectric-filled opening; 
 radio-frequency transceiver circuitry in the housing; and 
 a radio-frequency transmission line comprising a ground conductor and a signal conductor coupled to the radio-frequency transceiver circuitry, wherein the ground conductor is coupled to a first terminal on the antenna ground and the signal conductor is coupled to second and third terminals on the peripheral conductive housing structures. 
 
     
     
       2. The electronic device defined in  claim 1 , further comprising:
 a dielectric-filled gap in the peripheral conductive housing structures that separates the antenna resonating element arm from an additional segment of the peripheral conductive housing structures, wherein the second terminal is coupled to the antenna resonating element arm and the third terminal is coupled to the additional segment of the peripheral conductive housing structures. 
 
     
     
       3. The electronic device defined in  claim 2 , wherein a portion of the dielectric-filled opening extends between the additional segment of the peripheral conductive housing structures and the antenna ground. 
     
     
       4. The electronic device defined in  claim 3 , wherein antenna resonating element arm is configured to convey radio-frequency signals in a first frequency band and the portion of the dielectric-filled opening is configured to convey radio-frequency signals in a second frequency band that is higher than the first frequency band. 
     
     
       5. The electronic device defined in  claim 4 , wherein the signal conductor comprises a first branch coupled to the second terminal and a second branch coupled to the third terminal, the electronic device further comprising:
 a switch interposed on the second branch of the signal conductor. 
 
     
     
       6. The electronic device defined in  claim 5 , wherein the switch has a first state at which an open circuit is formed between the first branch and the third terminal and a second state at which a short circuit path is formed between the first branch and the third terminal, the portion of the dielectric-filled opening being configured to convey the radio-frequency signals in the second frequency band when the switch is in the second state. 
     
     
       7. The electronic device defined in  claim 6 , wherein the additional segment is configured to convey the radio-frequency signals in the second frequency band when the switch is in the first state, the antenna resonating element arm being configured to indirectly feed the additional segment of the peripheral conductive housing structures via near-field electromagnetic coupling when the switch is in the first state. 
     
     
       8. The electronic device defined in  claim 7 , further comprising:
 an adjustable component coupled between the antenna resonating element arm and the antenna ground, wherein the adjustable component is configured to tune a frequency response of the antenna in the first frequency band. 
 
     
     
       9. The electronic device defined in  claim 8 , further comprising:
 an additional dielectric-filled gap in the peripheral conductive housing structures; and 
 an additional radio-frequency transmission line coupled to a fourth terminal on the antenna ground and a fifth terminal on the antenna resonating element arm, wherein the fifth terminal is interposed between the additional-dielectric filled gap in the peripheral conductive housing structures and the second terminal. 
 
     
     
       10. The electronic device defined in  claim 9 , wherein the additional radio-frequency transmission line is configured to convey radio-frequency signals in a third frequency band that is lower than the first and second frequency bands, the antenna resonating element arm is configured to convey the radio-frequency signals in the third frequency band, and the electronic device further comprises:
 control circuitry configured to selectively activate a given one of the radio-frequency transmission line and the additional radio-frequency transmission line. 
 
     
     
       11. The electronic device defined in  claim 10 , wherein the first frequency band comprises a first cellular telephone communications band between 1710 MHz and 2170 MHz, the second frequency band comprises a second cellular telephone communications band between 2300 MHz and 2700 MHz, and the third frequency band comprises a third cellular telephone communications band between 600 MHz and 960 MHz. 
     
     
       12. The electronic device defined in  claim 10 , further comprising an additional antenna having an additional antenna resonating element arm that is separated from the segment of the peripheral conductive housing structures by the additional dielectric-filled gap, wherein the control circuitry is configured to control the antenna and the additional antenna to perform radio-frequency communications at the same frequency using a multiple-input and multiple-output (MIMO) scheme. 
     
     
       13. The electronic device defined in  claim 4 , further comprising:
 an adjustable component coupled between the antenna resonating element arm and the antenna ground, wherein the adjustable component is configured to tune a frequency response of the antenna in the first frequency band. 
 
     
     
       14. An electronic device comprising:
 a housing having peripheral conductive structures; 
 a dielectric-filled gap in the peripheral conductive structures that divides the peripheral conductive structures into first and second segments; 
 an antenna ground; 
 a first slot that separates the antenna ground from the first segment; 
 a second slot that extends from an end of the first slot beyond an edge of the dielectric-filled gap in the peripheral conductive structures, wherein the second slot has edges defined by the antenna ground and the second segment of the peripheral conductive structures; and 
 an antenna formed from the antenna ground, the first slot, the second slot, the first segment, and the second segment, wherein the antenna comprises an antenna feed having a ground antenna feed terminal coupled to the antenna ground, a first positive antenna feed terminal coupled to the first segment, and a second positive antenna feed terminal coupled to the second segment. 
 
     
     
       15. The electronic device defined in  claim 14 , further comprising:
 radio-frequency transceiver circuitry; and 
 a radio-frequency transmission line that has a signal conductor coupled between the antenna feed and the radio-frequency transceiver circuitry, wherein the signal conductor is coupled to the first positive antenna feed terminal over a first signal conductor branch and the signal conductor is coupled to the second positive antenna feed terminal over a second signal conductor branch. 
 
     
     
       16. The electronic device defined in  claim 15 , wherein the second signal conductor branch and the second positive antenna feed terminal are configured to directly feed the second slot and the second slot is configured to radiate radio-frequency signals in a first frequency band. 
     
     
       17. The electronic device defined in  claim 16 , further comprising:
 an additional dielectric-filled gap in the peripheral conductive structures that separates the first segment from a third segment of the peripheral conductive structures, wherein the first segment comprises a first portion extending between the first positive antenna feed terminal and the dielectric-filled gap and a second portion extending between the first positive antenna feed terminal and the additional dielectric filled gap, the first portion of the first segment being configured to radiate radio-frequency signals in a second frequency band that is lower than the first frequency band, and the second portion of the first segment being configured to radiate radio-frequency signals in a third frequency band that is lower than the second frequency band. 
 
     
     
       18. The electronic device defined in  claim 17 , further comprising:
 switching circuitry interposed on the second signal conductor branch, wherein the switching circuitry has a first state at which an open circuit is formed between the first signal conductor branch and the second positive antenna feed terminal and a second state at which a short circuit is formed between the first signal conductor branch and the second positive antenna feed terminal, the first portion of the first segment is configured to indirectly feed the second segment and the second segment is configured to radiate the radio-frequency signals in the first frequency band when the switching circuitry is in the first state, and the second slot is configured to radiate the radio-frequency signals in the first frequency band when the switching circuitry is in the second state. 
 
     
     
       19. An electronic device comprising:
 a housing having peripheral conductive housing structures; 
 a dielectric-filled gap in the peripheral conductive housing structures that divides the peripheral conductive housing structures into first and second segments; 
 a radio-frequency transmission line having a signal conductor and a ground conductor; and 
 an antenna, wherein the antenna comprises:
 an antenna resonating element arm formed from the first segment; 
 an antenna ground separated from the first and second segments by a dielectric-filled opening; and 
 an antenna feed having a ground antenna feed terminal on the ground conductor, a first positive antenna feed terminal on the first segment that is coupled to the signal conductor, and a second positive antenna feed terminal on the second segment that is coupled to the signal conductor. 
 
 
     
     
       20. The electronic device defined in  claim 19 , further comprising:
 an additional radio-frequency transmission line coupled to an additional antenna feed having a third positive antenna feed terminal on the first segment and an additional ground antenna feed terminal on the antenna ground; and 
 control circuitry configured to selectively activate a given one of the antenna feed and the additional antenna feed at a given time.

Description:
BACKGROUND 
     This relates to electronic devices, and more particularly, to antennas for electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components using compact structures. At the same time, there is a desire for wireless devices to cover a growing number of communications bands. For example, it may be desirable for a wireless device to cover many different cellular telephone communications bands at different frequencies. 
     Because antennas have the potential to interfere with each other and with components in a wireless device, care must be taken when incorporating antennas into an electronic device. Moreover, care must be taken to ensure that the antennas and wireless circuitry in a device are able to exhibit satisfactory performance over the desired range of operating frequencies. In addition, it is often difficult to perform wireless communications with a satisfactory data rate (data throughput), especially as software applications performed by wireless devices become increasingly data hungry. 
     It would therefore be desirable to be able to provide improved wireless communications circuitry for wireless electronic devices. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry and a housing having a peripheral conductive housing structures. The wireless circuitry may include an antenna, radio-frequency transceiver circuitry, and one or more radio-frequency transmission lines. The antenna may include an antenna resonating element arm formed from a first segment of the peripheral conductive housing structures that is separated from an antenna ground by a dielectric-filled opening. A dielectric-filled gap in the peripheral conductive housing structures may separate the first segment from a second segment of the peripheral conductive housing structures. 
     A first slot may separate the antenna ground from the first segment. A second slot may separate the antenna ground from the second segment. The first and second slots may, for example, be formed from continuous portions of the dielectric filled opening (e.g., where the second slot extends from an end of the first slot and beyond an edge of the dielectric-filled gap in the peripheral conductive housing structures). The second slot may have edges defined by the antenna ground and the second segment of the peripheral conductive structures. 
     The antenna may be fed using an antenna feed having a ground antenna feed terminal and first and second positive antenna feed terminals. The first positive antenna feed terminal may be located on the first segment whereas the second positive antenna feed terminal is located on the second segment. A radio-frequency transmission line may include a ground conductor coupled to the ground antenna feed terminal and a signal conductor having first and second signal conductor branches. The first signal conductor branch may be coupled to the first positive antenna feed terminal. The second signal conductor branch may be coupled to the second positive antenna feed terminal. The second slot may be directly fed using the radio-frequency transmission line over the second signal conductor branch and the second positive antenna feed terminal. 
     If desired, a switch may be interposed on the second signal conductor branch. When the switch is open, the second segment may be indirectly fed by an end of the first segment and may radiate (e.g., may convey radio-frequency signals) in a first frequency band such as a cellular high band between 2300 MHz and 2700 MHz. When the switch is closed, the second slot may be directly fed and may radiate in the first frequency band (e.g., with greater efficiency towards the upper end of the cellular high band relative to when the switch is open). The first segment may radiate in a second frequency band such as a cellular midband and/or a cellular low-midband regardless of the state of the switch. If desired, an adjustable component may be coupled between the first segment and the antenna ground for adjusting the response of the antenna in the second frequency band. 
     In one suitable arrangement, the antenna may include an additional antenna feed coupled to an additional radio-frequency transmission line. Control circuitry in the electronic device may selectively activate one of the antenna feeds at a given time. When the additional antenna feed is active, the antenna may operate with optimized antenna efficiency in a third frequency band such as a cellular low band from 600 MHz to 960 MHz, for example. Multiple antennas in the device may be implemented using these structures and may concurrently convey radio-frequency signals at one or more of the same frequencies using a multiple-input and multiple-output (MIMO) scheme if desired. 
    
    
     
       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 in an electronic device having multiple signal feed terminals for optimizing radio-frequency performance across multiple different communications bands in accordance with an embodiment. 
         FIG. 8  is a flow chart of illustrative steps that may be involved in adjusting an antenna of the type shown in  FIG. 7  in accordance with an embodiment. 
         FIG. 9  is a plot of antenna performance (antenna efficiency) of an illustrative antenna of the type shown in  FIG. 7  in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. 
     The wireless communications circuitry may include one more antennas. The antennas of the wireless communications circuitry can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. 
     The conductive electronic device structures may include conductive housing structures. The housing structures may include peripheral structures such as peripheral conductive structures that run around the periphery of the electronic device. The peripheral conductive structures may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, may have portions that extend upwards from an integral planar rear housing (e.g., to form vertical planar sidewalls or curved sidewalls), and/or may form other housing structures. 
     Gaps may be formed in the peripheral conductive structures that divide the peripheral conductive structures into peripheral segments. One or more of the segments may be used in forming one or more antennas for electronic device  10 . Antennas may also be formed using an antenna ground plane and/or an antenna resonating element formed from conductive housing structures (e.g., internal and/or external structures, support plate structures, etc.). 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Device  10  may also be a set-top box, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, a wireless access point, wireless base station, an electronic device incorporated into a kiosk, building, or vehicle, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may be mounted on the front face of device  10 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or may be insensitive to touch. The rear face of housing  12  (i.e., the face of device  10  opposing the front face of device  10 ) may have a rear housing wall (e.g., a planar housing wall). The rear housing wall may have slots that pass entirely through the rear housing wall and that therefore separate housing wall portions (rear housing wall portions and/or sidewall portions) of housing  12  from each other. The rear housing wall may include conductive portions and/or dielectric portions. If desired, the rear housing wall may include a planar metal layer covered by a thin layer or coating of dielectric such as glass, plastic, sapphire, or ceramic. Housing  12  (e.g., the rear housing wall, sidewalls, etc.) may also have shallow grooves that do not pass entirely through housing  12 . The slots and grooves may be filled with plastic or other dielectric. If desired, portions of housing  12  that have been separated from each other (e.g., by a through slot) may be joined by internal conductive structures (e.g., sheet metal or other metal members that bridge the slot). 
     Display  14  may include pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable pixel structures. A display cover layer such as a layer of clear glass or plastic may cover the surface of display  14  or the outermost layer of display  14  may be formed from a color filter layer, thin-film transistor layer, or other display layer. If desired, buttons may pass through openings in the cover layer. The cover layer may also have other openings such as an opening for speaker port  8 . 
     Housing  12  may include peripheral housing structures such as structures  16 . Structures  16  may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape with four edges, structures  16  may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges (as an example). Peripheral structures  16  or part of peripheral structures  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or that helps hold display  14  to device  10 ). Peripheral structures  16  may, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral housing structures  16  may be formed of a conductive material such as metal and may therefore sometimes be referred to as peripheral conductive housing structures, conductive housing structures, peripheral metal structures, peripheral conductive housing sidewall structures, peripheral conductive housing sidewalls, peripheral conductive sidewalls, or a peripheral conductive housing member (as examples). Peripheral conductive housing structures  16  may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, three, four, five, six, or more than six separate structures may be used in forming peripheral conductive housing structures  16 . 
     It is not necessary for peripheral conductive housing structures  16  to have a uniform cross-section. For example, the top portion of peripheral conductive housing structures  16  may, if desired, have an inwardly protruding lip that helps hold display  14  in place. The bottom portion of peripheral conductive housing structures  16  may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). Peripheral conductive housing structures  16  may have substantially straight vertical sidewalls, may have sidewalls that are curved, or may have other suitable shapes. In some configurations (e.g., when peripheral conductive housing structures  16  serve as a bezel for display  14 ), peripheral conductive housing structures  16  may run around the lip of housing  12  (i.e., peripheral conductive housing structures  16  may cover only the edge of housing  12  that surrounds display  14  and not the rest of the sidewalls of housing  12 ). 
     If desired, housing  12  may have a conductive rear surface or wall. For example, housing  12  may be formed from a metal such as stainless steel or aluminum. The rear surface of housing  12  may lie in a plane that is parallel to display  14 . In configurations for device  10  in which the rear surface of housing  12  is formed from metal, it may be desirable to form parts of peripheral conductive housing structures  16  as integral portions of the housing structures forming the rear surface of housing  12 . For example, a conductive rear housing wall of device  10  may be formed from a planar metal structure and portions of peripheral conductive housing structures  16  on the sides of housing  12  may be formed as flat or curved vertically extending integral metal portions of the planar metal structure. Housing structures such as these may, if desired, be machined from a block of metal and/or may include multiple metal pieces that are assembled together to form housing  12 . The conductive rear wall of housing  12  may have one or more, two or more, or three or more portions. Peripheral conductive housing structures  16  and/or the conductive rear wall of housing  12  may form one or more exterior surfaces of device  10  (e.g., surfaces that are visible to a user of device  10 ) and/or may be implemented using internal structures that do not form exterior surfaces of device  10  (e.g., conductive housing structures that are not visible to a user of device  10  such as conductive structures that are covered with layers such as thin cosmetic layers, protective coatings, and/or other coating layers that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide structures  16  and/or the conductive rear wall of housing  12  from view of the user). 
     Display  14  may have an array of pixels that form an active area AA that displays images for a user of device  10 . An inactive border region such as inactive area IA may run along one or more of the peripheral edges of active area AA. 
     Display  14  may include conductive structures such as an array of capacitive electrodes for a touch sensor, conductive lines for addressing pixels, driver circuits, etc. Housing  12  may include internal conductive structures such as metal frame members and a planar conductive housing member (sometimes referred to as a backplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more metal parts that is welded or otherwise connected between opposing sides of member  16 ). The backplate may form an exterior rear surface of device  10  or may be covered by layers such as thin cosmetic layers, protective coatings, and/or other coatings that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide the backplate from view of the user. Device  10  may also include conductive structures such as printed circuit boards, components mounted on printed circuit boards, and other internal conductive structures. These conductive structures, which may be used in forming a ground plane in device  10 , may extend under active area AA of display  14 , for example. 
     In regions  22  and  20 , openings may be formed within the conductive structures of device  10  (e.g., between peripheral conductive housing structures  16  and opposing conductive ground structures such as conductive portions of the rear wall of housing  12 , conductive traces on a printed circuit board, conductive electrical components in display  14 , etc.). These openings, which may sometimes be referred to as gaps, may be filled with air, plastic, and/or other dielectrics and may be used in forming slot antenna resonating elements for one or more antennas in device  10 , if desired. 
     Conductive housing structures and other conductive structures in device  10  may serve as a ground plane for the antennas in device  10 . The openings in regions  20  and  22  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, may contribute to the performance of a parasitic antenna resonating element, or may otherwise serve as part of antenna structures formed in regions  20  and  22 . If desired, the ground plane that is under active area AA of display  14  and/or other metal structures in device  10  may have portions that extend into parts of the ends of device  10  (e.g., the ground may extend towards the dielectric-filled openings in regions  20  and  22 ), thereby narrowing the slots in regions  20  and  22 . 
     In general, device  10  may include any suitable number of antennas (e.g., one or more, two or more, three or more, four or more, etc.). The antennas in device  10  may be located at opposing first and second ends of an elongated device housing (e.g., at ends  20  and  22  of device  10  of  FIG. 1 ), along one or more edges of a device housing, in the center of a device housing, in other suitable locations, or in one or more of these locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral conductive housing structures  16  may be provided with peripheral gap structures. For example, peripheral conductive housing structures  16  may be provided with one or more gaps such as gaps  18 , as shown in  FIG. 1 . The gaps in peripheral conductive housing structures  16  may be filled with dielectric such as polymer, ceramic, glass, air, other dielectric materials, or combinations of these materials. Gaps  18  may divide peripheral conductive housing structures  16  into one or more peripheral conductive segments. There may be, for example, two peripheral conductive segments in peripheral conductive housing structures  16  (e.g., in an arrangement with two of gaps  18 ), three peripheral conductive segments (e.g., in an arrangement with three of gaps  18 ), four peripheral conductive segments (e.g., in an arrangement with four of gaps  18 ), six peripheral conductive segments (e.g., in an arrangement with six gaps  18 ), etc. The segments of peripheral conductive housing structures  16  that are formed in this way may form parts of antennas in device  10 . 
     If desired, openings in housing  12  such as grooves that extend partway or completely through housing  12  may extend across the width of the rear wall of housing  12  and may penetrate through the rear wall of housing  12  to divide the rear wall into different portions. These grooves may also extend into peripheral conductive housing structures  16  and may form antenna slots, gaps  18 , and other structures in device  10 . Polymer or other dielectric may fill these grooves and other housing openings. In some situations, housing openings that form antenna slots and other structure may be filled with a dielectric such as air. 
     In a typical scenario, device  10  may have one or more upper antennas and one or more lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, near-field communications, etc. 
     A schematic diagram showing illustrative components that may be used in device  10  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  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, etc. 
     Input-output circuitry  30  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  34  may include radio-frequency transceiver circuitry  26  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  42 . Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications or communications in other wireless local area network (WLAN) bands and may handle the 2.4 GHz Bluetooth® communications band or other wireless personal area network (WPAN) bands. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in frequency ranges such as a cellular communications low band from 600 to 960 MHz, a cellular communications low-midband from 1410 to 1510 MHz, a cellular communications midband from 1710 to 2170 MHz, a cellular communications high band from 2300 to 2700 MHz, a cellular communications ultra-high band from 3400 to 3600 MHz, or other communications bands between 600 MHz and 4000 MHz or other suitable frequencies (as examples). 
     Circuitry  38  may handle voice data and non-voice data. Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include 60 GHz transceiver circuitry, circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. Wireless communications circuitry  34  may include global positioning system (GPS) receiver equipment such as GPS receiver circuitry  42  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. In Wi-Fi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, dipole antenna structures, monopole antenna structures, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. 
     As shown in  FIG. 3 , transceiver circuitry  26  in wireless communications circuitry  34  may be coupled to antenna structures such as a given antenna  40  using paths such as path  92 . Wireless communications circuitry  34  may be coupled to control circuitry  28 . Control circuitry  28  may be coupled to input-output devices  32 . Input-output devices  32  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures such as antenna  40  with the ability to cover communications frequencies of interest, antenna  40  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). If desired, antenna  40  may be provided with adjustable circuits such as tunable components  102  to tune the antenna 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  90  that adjust inductance values, capacitance values, or other parameters associated with tunable components  102 , thereby tuning antenna  40  to cover desired communications bands. 
     Path  92  may include one or more transmission lines. As an example, path  92  of  FIG. 3  may be a transmission line having a positive signal conductor such as line  94  and a ground signal conductor such as line  96 . Path  92  may sometimes be referred to herein as transmission line  92  or radio-frequency transmission line  92 . Line  94  may sometimes be referred to herein as positive signal conductor  94 , signal conductor  94 , signal line conductor  94 , signal line  94 , positive signal line  94 , signal path  94 , or positive signal path  94  of transmission line  92 . Line  96  may sometimes be referred to herein as ground signal conductor  96 , ground conductor  96 , ground line conductor  96 , ground line  96 , ground signal line  96 , ground path  96 , or ground signal path  94  of transmission line  92 . 
     Transmission line  92  may, for example, include a coaxial cable transmission line (e.g., ground conductor  96  may be implemented as a grounded conductive braid surrounding signal conductor  94  along its length), a stripline transmission line, a microstrip transmission line, coaxial probes realized by a metalized via, an edge-coupled microstrip transmission line, an edge-coupled stripline transmission line, a waveguide structure, combinations of these types of transmission lines and/or other transmission line structures, etc. 
     Transmission lines in device  10  such as transmission line  92  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, transmission lines such as transmission line  92  may also include transmission line conductors (e.g., signal conductors  94  and ground conductors  96 ) integrated within multilayer laminated structures (e.g., layers of a conductive material such as copper and a dielectric material such as a resin that are laminated together without intervening adhesive). The multilayer laminated structures may, if desired, be folded or bent in multiple dimensions (e.g., two or three dimensions) and may maintain a bent or folded shape after bending (e.g., the multilayer laminated structures may be folded into a particular three-dimensional shape to route around other device components and may be rigid enough to hold its shape after folding without being held in place by stiffeners or other structures). All of the multiple layers of the laminated structures may be batch laminated together (e.g., in a single pressing process) without adhesive (e.g., as opposed to performing multiple pressing processes to laminate multiple layers together with adhesive). 
     A matching network (e.g., an adjustable matching network formed using tunable components  102 ) may include components such as inductors, resistors, and capacitors used in matching the impedance of antenna  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  40 . As an example, antenna  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed  112  with a positive antenna feed terminal such as terminal  98  and a ground antenna feed terminal such as ground antenna feed terminal  100 . Signal conductor  94  may be coupled to positive antenna feed terminal  98  and ground 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  40  may be fed using multiple feeds each coupled to a respective port of transceiver circuitry  26  over a corresponding transmission line. If desired, signal conductor  94  may be coupled to multiple locations on antenna  40  (e.g., antenna  40  may include multiple positive antenna feed terminals coupled to signal conductor  94  of the same transmission line  92 ). The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     Control circuitry  28  may use information from a proximity sensor, wireless performance metric data such as received signal strength information, device orientation information from an orientation sensor, device motion data from an accelerometer or other motion detecting sensor, information about a usage scenario of device  10 , information about whether audio is being played through speaker  26 , information from one or more antenna impedance sensors, information on desired frequency bands to use for communications, and/or other information in determining when antenna  40  is being affected by the presence of nearby external objects or is otherwise in need of tuning. In response, control circuitry  28  may adjust an adjustable inductor, adjustable capacitor, switch, or other tunable components  102  to ensure that antenna  40  operates as desired. Adjustments to tunable components  102  may also be made to extend the frequency coverage of antenna  40  (e.g., to cover desired communications bands that extend over a range of frequencies larger than antenna  40  would cover without tuning). 
     Antenna  40  may include resonating element structures (sometimes referred to herein as radiating element structures), antenna ground plane structures (sometimes referred to herein as ground plane structures, ground structures, or antenna ground structures), an antenna feed such as feed  112 , and other components (e.g., tunable components  102 ). Antenna  40  may be configured to form any suitable types of antenna. With one suitable arrangement, which is sometimes described herein as an example, antenna  40  is used to implement a hybrid inverted-F-slot antenna that includes both inverted-F and slot antenna resonating elements. 
     If desired, multiple antennas  40  may be formed in device  10 . Each antenna  40  may be coupled to transceiver circuitry such as transceiver circuitry  26  over respective transmission lines such as transmission line  92 . If desired, two or more antennas  40  may share the same transmission line  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 transceiver circuitry  26 . 
     Port  122  may receive digital data from storage and processing circuitry that is to be transmitted by transceiver circuitry  26 . Incoming data that has been received by transceiver circuitry  26  and baseband processor  120  may be supplied to storage and processing circuitry via port  122 . 
     Transceiver circuitry  26  may include one or more transmitters and one or more receivers. For example, transceiver circuitry  26  may include multiple remote wireless transceivers  38  such as a first transceiver  38 - 1 , a second transceiver  38 - 2 , a third transceiver  38 - 3 , and a fourth transceiver  38 - 4  (e.g., transceiver circuits for handling voice and non-voice cellular telephone communications in cellular telephone communications bands). Each transceiver  38  may be coupled to a respective antenna  40  over a corresponding transmission line  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 transmission line  92 - 1 , a second front end circuit  128 - 2  may be interposed on transmission line  92 - 2 , a third front end circuit  128 - 3  may be interposed on transmission 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 lines  92  to the corresponding antenna  40 , networks of active and/or passive components such as tunable 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 transceiver circuitry  26  for amplifying radio-frequency signals output by transceivers  38  prior to transmission over antennas  40 . Amplifier circuitry such as one or more low noise amplifiers may be interposed on transmission lines  92  and/or formed within transceiver circuitry  26  for amplifying radio-frequency signals received by antennas  40  prior to conveying the received signals to transceivers  38 . 
     In the example of  FIG. 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 transmission lines  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., transceiver circuitry  26  may be a transceiver module having a substrate or integrated circuit on which each of transceivers  38  are formed) or two or more transceivers  38  may be formed on separate substrates, integrated circuits, or modules. Baseband 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, transceiver circuitry  26  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 600 and 960 MHz, a second frequency band such as a low-midband between 1410 and 1510 MHz, a third frequency band such as a midband between 1700 and 2200 MHz, a fourth frequency band such as a high band between 2300 and 2700 MHz, and/or a fifth frequency band such as an ultra-high band between 3400 and 3600 MHz. Transceiver  38 - 2 , antenna  40 - 2 , transceiver  38 - 3 , and antenna  40 - 3  may handle radio-frequency signals in some or all of these bands (e.g., in scenarios where the volume of antennas  40 - 1  and  40 - 2  is large enough to support frequencies in the low band). 
     The example of  FIG. 4  is merely illustrative. In general, antennas  40  may cover any desired frequency bands. Transceiver circuitry  26  may include other transceiver circuits such as one or more circuits  36  or  42  of  FIG. 2  coupled to one or more antennas  40 . Housing  12  may have any desired shape. Antennas  40  may be formed at any desired locations within housing  12 . Forming each of antennas  40 - 1  through  40 - 4  at different corners of housing  12  may, for example, maximize the multi-path propagation of wireless data conveyed by antennas  40  to optimize overall data throughput for wireless 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 wireless communications 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 communications circuitry  34  may perform so-called two-stream (2×) MIMO operations (sometimes referred to herein as 2× MIMO communications or communications using a 2× MIMO scheme) in which two antennas  40  are used to convey two independent streams of radio-frequency signals at the same frequency. Wireless communications circuitry  34  may perform so-called four-stream (4×) MIMO operations (sometimes referred to herein as 4× MIMO communications or communications using a 4× MIMO scheme) in which four antennas  40  are used to convey four independent streams of radio-frequency signals at the same frequency. Performing 4× MIMO operations may support higher overall data throughput than 2× MIMO operations because 4× MIMO operations involve four independent wireless data streams whereas 2× MIMO operations involve only two independent wireless data streams. If desired, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 2× MIMO operations in some frequency bands and may perform 4× MIMO operations in other frequency bands (e.g., depending on which bands are handled by which antennas). Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 2× MIMO operations in some bands concurrently with performing 4× MIMO operations in other bands, for example. 
     As one example, antennas  40 - 1  and  40 - 4  (and the corresponding transceivers  38 - 1  and  38 - 4 ) may perform 2× MIMO operations by conveying radio-frequency signals at the same frequency in a 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). This example is merely illustrative and, in general, any desired number of antennas may be used to perform any desired MIMO operations in any desired frequency bands. 
     If desired, antennas  40 - 1  and  40 - 2  may include switching circuitry that is adjusted by control circuitry (e.g., control circuitry  28  of  FIG. 3 ). Control circuitry  28  may control the switching circuitry in antennas  40 - 1  and  40 - 2  to configure antenna structures in antennas  40 - 1  and  40 - 2  to form a single antenna  40 U in region  22  of device  10 . Similarly, antennas  40 - 3  and  40 - 4  may include switching circuitry that is adjusted by control circuitry  28 . Control circuitry  28  may control the switching circuitry in antennas  40 - 3  and  40 - 4  to form a single antenna  40 L (e.g., an antenna  40 L that includes antenna structures from antennas  40 - 3  and  40 - 4 ) in region  20  of device  10 . Antenna  40 U may, for example, be formed at an upper end of housing  12  and may therefore sometimes be referred to herein as upper antenna  40 U. Antenna  40 L may be formed at an opposing lower end of housing  12  and may therefore sometimes be referred to herein as lower antenna  40 L. When antennas  40 - 1  and  40 - 2  are configured to form upper antenna  40 U and antennas  40 - 3  and  40 - 4  are configured to form lower antenna  40 L, wireless circuitry  34  may perform 2× MIMO operations using antennas  40 U and  40 L in any desired frequency bands. If desired, control circuitry  28  may toggle the switching circuitry over time to switch wireless circuitry  34  between a first mode in which antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  perform 2× MIMO operations in any desired frequency bands and 4× MIMO operations in any desired frequency bands and a second mode in which antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  are configured to form antennas  40 U and  40 L that perform 2× MIMO operations in any desired frequency bands. 
     If desired, wireless communications circuitry  34  may convey wireless data with multiple antennas on one or more external devices (e.g., multiple wireless base stations) in a scheme sometimes referred to as carrier aggregation. When operating using a carrier aggregation scheme, the same antenna  40  may convey radio-frequency signals with multiple antennas (e.g., antennas on different wireless base stations) at different respective frequencies (sometimes referred to herein as carrier frequencies, channels, carrier channels, or carriers). For example, antenna  40 - 1  may receive radio-frequency signals from a first wireless base station at a first frequency, from a second wireless base station at a second frequency, and a from a third base station at a third frequency. The received signals at different frequencies may be simultaneously processed (e.g., by transceiver  38 - 1 ) to increase the communications bandwidth of transceiver  38 - 1 , thereby increasing the data rate of transceiver  38 - 1 . Similarly, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform carrier aggregation at two, three, or more than three frequencies within any desired frequency bands. This may serve to further increase the overall data throughput of wireless communications circuitry  34  relative to scenarios where no carrier aggregation is performed. For example, the data throughput of circuitry  34  may increase for each carrier frequency that is used (e.g., for each wireless base station that communicates with each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 ). 
     By performing communications using both a MIMO scheme and a carrier aggregation scheme, the data throughput of wireless communications circuitry  34  may be even greater than in scenarios where either a MIMO scheme or a carrier aggregation scheme is used. The data throughput of circuitry  34  may, for example, increase for each carrier frequency that is used by antennas  40  (e.g., each carrier frequency may contribute 40 megabits per second (Mb/s) or some other throughput to the total throughput of wireless communications circuitry  34 ). As one example, antennas  40 - 1  and  40 - 4  may perform carrier aggregation across three frequencies within each of the cellular low band, midband, and high band and antennas  40 - 3  and  40 - 4  may perform carrier aggregation across three frequencies within each of the cellular midband and high band. At the same time, antennas  40 - 1  and  40 - 4  may perform 2× MIMO operations in the cellular low band and antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 4× MIMO operations in one of cellular midband and the cellular high band. In this scenario, with an exemplary throughput of 40 Mb/s per carrier frequency, wireless circuitry  34  may exhibit a throughput of approximately 960 Mb/s. If 4× MIMO operations are performed in both the cellular midband and the cellular high band by antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 , wireless communications circuitry  34  may exhibit an even greater throughput of approximately 1200 Mb/s. In other words, the data throughput of wireless communications circuitry  34  may be increased from the 40 Mb/s associated with conveying signals at a single frequency with a single antenna to approximately 1 gigabits per second (Gb/s) by performing communications using MIMO and carrier aggregation schemes using four antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 . 
     These examples are merely illustrative and, if desired, carrier aggregation may be performed in fewer than three carriers per band, may be performed across different bands, or may be omitted for one or more of antennas  40 - 1  through  40 - 4 . The example of  FIG. 4  is merely illustrative. If desired, antennas  40  may cover any desired number of frequency bands at any desired frequencies. More than four antennas  40  or fewer than four antennas  40  may perform MIMO and/or carrier aggregation operations at non-near-field communications frequencies if desired. 
     Antennas  40  may include slot antenna structures, inverted-F antenna structures (e.g., planar and non-planar inverted-F antenna structures), loop antenna structures, combinations of these, or other antenna structures. 
     An illustrative inverted-F antenna structure is shown in  FIG. 5 . When using an inverted-F antenna structure as shown in  FIG. 5 , antenna  40  may include an antenna resonating element  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  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  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 antenna 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 antenna ground  136 . If desired, antenna  40  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 . If desired, 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, antenna  40  may include one or more adjustable circuits (e.g., tunable components  102  of  FIG. 3 ) that are coupled to arm  132 . As shown in  FIG. 5 , for example, tunable components  102  such as adjustable inductor  140  may be coupled between antenna resonating element structures in antenna  40  such as arm  132  and antenna ground  136  (i.e., adjustable inductor  140  may bridge the gap between arm  132  and antenna ground  136 ). Adjustable inductor  140  may exhibit an inductance value that is adjusted in response to control signals  138  provided to adjustable inductor  140  from control circuitry  28  ( FIGS. 2 and 3 ). 
     Antenna  40  may be a hybrid antenna that includes one or more slot elements. As shown in  FIG. 6 , for example, antenna  40  may be based on a slot antenna configuration having an opening such as slot  142  that is formed within conductive structures such as antenna ground  136 . Slot  142  may be filled with air, plastic, and/or other dielectric. The shape of slot  142  may be straight or may have one or more bends (i.e., slot  142  may have an elongated shape following a meandering path). Feed terminals  98  and  100  may, for example, be located on opposing sides of slot  142  (e.g., on opposing long sides). Slot  142  may sometimes be referred to herein as slot element  142 , slot antenna resonating element  142 , slot antenna radiating element  142 , or slot radiating element  142 . Slot-based radiating elements such as slot  142  of  FIG. 6  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 slot  142  is associated with signal frequencies at which the slot length is approximately equal to a half of a wavelength of operation. 
     The frequency response of antenna  40  can be tuned using one or more tuning components (e.g., components  102  of  FIG. 3 ). These components may have terminals that are coupled to opposing sides of slot  142  (i.e., the tunable components may bridge slot  142 ). If desired, tunable components may have terminals that are coupled to respective locations along the length of one of the sides of slot  142 . 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  142  of  FIG. 6 ). 
     The example of  FIG. 6  is merely illustrative. In general, slot  142  may have any desired shape (e.g., shapes with straight and/or curved edges), may follow a meandering path, etc. If desired, slot  142  may be an open slot having one or more ends that are free from conductive material (e.g., where slot  142  extends through one or more sides of antenna ground  136 ). Slot  142  may, for example, have a length approximately equal to one-quarter of the wavelength of operation in these scenarios. 
     A top interior view of an illustrative portion of device  10  that contains antenna  40 - 4  of  FIG. 4  is shown in  FIG. 7 . In the example of  FIG. 7 , antenna  40 - 4  is formed using hybrid slot-inverted-F antenna structures that includes resonating elements of the types shown in  FIGS. 5 and 6 . 
     As shown in  FIG. 7 , 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 . 
     The resonating element for antenna  40 - 4  may include an inverted-F antenna resonating element arm such as arm  132  that is formed from a segment of peripheral conductive housing structures  16  extending between gaps  18 - 3  and  18 - 2 . Air and/or other dielectric may fill slot  142  between arm  132  and antenna ground  136 . If desired, opening  142  may be configured to form a slot antenna resonating element structure that contributes to the overall performance of the antenna. 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, or other conductive structures. In one suitable arrangement antenna ground  136  is formed from conductive portions of housing  12  (e.g., portions of a rear wall of housing  12  and portions of peripheral conductive housing structures  16  that are separated from arm  132  by peripheral gaps  18 - 1  and  18 - 2 ) and conductive portions of display  14  (e.g., conductive portions of a display panel, a conductive plate for supporting the display panel, and/or a conductive frame for supporting the conductive plate and/or the display panel). 
     Antenna  40 - 4  may be fed using transmission line  92 - 4 . Transmission line  92 - 4  may include ground conductor  96  and signal conductor  94 . In one suitable example, transmission line  92 - 4  is a coaxial cable having a conductive outer braid that forms ground conductor  96  and having a signal conductor  94  that is surrounded by the conductive outer braid. This is merely illustrative and, in general, any desired transmission line structures having signal conductor  94  and ground conductor  96  may be used. 
     Transmission line  92 - 4  may be coupled to antenna feed  112  for antenna  40 - 4 . Positive antenna feed terminal  98  of antenna feed  112  may be coupled to arm  132 . Ground antenna feed terminal  100  of antenna feed  112  may be coupled to antenna ground  136  (e.g., antenna feed terminals  100  and  98  may be coupled to opposing sides of slot  142 ). Signal conductor  94  of transmission line  92 - 4  may be coupled to positive antenna feed terminal  98  across slot  142 . Ground conductor  96  of transmission line  92 - 4  may be coupled to antenna ground  136 . The opposing end of transmission line  92 - 4  may be coupled to transceiver circuitry  26  ( FIG. 4 ). In one suitable arrangement, transmission line  92 - 4  may convey cellular telephone signals for transceiver circuitry  26  in one or more of a low band from 600 to 960 MHz, a low-midband from 1410 to 1510 MHz, a midband from 1710 to 2170 MHz, a high band from 2300 to 2700 MHz, and an ultra-high band from 3400 to 3600 MHz. 
     Antenna ground  136  may have any desired shape within device  10 . For example, the lower edge of antenna ground  136  (e.g., the edge coupled of antenna ground  136  coupled to ground antenna feed terminal  100 ) may be aligned with gaps  18 - 1  and/or  18 - 2  in peripheral conductive hosing structures  16  (e.g., the upper or lower edge of gaps  18 - 1  and/or  18 - 2  may be aligned with the edge of antenna ground  136  defining slot  142  adjacent to gaps  18 - 1  and/or  18 - 2 ). For example, slot  142  may extend from gap  18 - 1  to gap  18 - 2  (e.g., the ends of slot  142  which may sometimes be referred to as open ends, may be formed by gaps  18 - 1  and  18 - 2 ). Slot  142  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  142  along the longitudinal axis of the longest portion of slot  142  (e.g., parallel to the X-axis of  FIG. 5 ). Slot  142  may be filled with dielectric such as air, plastic, ceramic, or glass. For example, plastic may be inserted into portions of slot  142  and this plastic may be flush with the outside of housing  12 . Dielectric material in slot  142  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  in which slot  142  has a U-shape is merely illustrative. If desired, slot  142  may have any other desired shapes (e.g., a rectangular shape, shapes having curved and/or straight edges, etc.). 
     If desired, as shown in  FIG. 7 , antenna ground  136  may include a slot such as vertical slot  190  adjacent to gap  18 - 2  that extends above the edges of gap  18 - 2  (e.g., along the Y-axis of  FIG. 7 ). A similar vertical slot may be formed adjacent to gap  18 - 1  if desired. 
     As shown in  FIG. 7 , vertical slot  190  adjacent to gap  18 - 2  may extend beyond the upper edge (e.g., upper edge  170 ) of gap  18 - 2  (e.g., in the direction of the Y-axis of  FIG. 5 ). Vertical slot  190  may, for example, have two or more edges that are defined by antenna ground  136  and one edge that is defined by peripheral conductive structures  16  (e.g., the segment of peripheral conductive structures  16  above gap  18 - 2 ). Vertical slot  190  may have an open end defined by an open end of slot  142  at gap  18 - 2 . Vertical slot  190  may therefore sometimes be referred to herein as a continuous portion of slot  142 , a vertical portion of slot  142 , or a vertical extension of slot  142 . 
     Vertical slot  190  may have a width  166  that separates antenna ground  136  from the portion of peripheral conductive structures  16  above gap  18 - 2  (e.g., in the direction of the X-axis of  FIG. 7 ). Because the portion of peripheral conductive structures  16  above gap  18 - 2  is shorted to antenna ground  136  (and thus forms part of the antenna ground for antenna  40 - 4 ), vertical slot  190  may effectively form an open slot having three sides defined by the antenna ground for antenna  40 - 4 . Vertical slot  190  may have any desired width (e.g., about 2 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, more than 0.5 mm, more than 1.5 mm, more than 2.5 mm, 1-3 mm, etc.). Vertical slot  190  may have an elongated length  162  (e.g., perpendicular to width  166 ). Vertical slot  190  may have any desired length  162  (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.). The segment of peripheral conductive housing structures  16  above gap  18 - 2  that defines an edge of vertical slot  190  may sometimes be referred to herein as segment, portion, or end  160  of peripheral conductive housing structures  16 . Segment  160  of peripheral conductive housing structures  16  may have the same length  162  as vertical slot  190 , for example. 
     Electronic device  10  may be characterized by longitudinal axis  150 . Length  162  may extend parallel to longitudinal axis  150  (e.g., the Y-axis of  FIG. 5 ). Portions of vertical slot  190  may contribute slot antenna resonances to antenna  40 - 4  in one or more frequency bands if desired. For example, the length and width of vertical slot  190  (e.g., the perimeter of vertical slot  190 ) may be selected so that antenna  40 - 4  resonates at desired operating frequencies. If desired, the overall length of slots  142  and  190  may be selected so that antenna  40  resonates at desired operating frequencies. 
     A return path for antenna  40 - 4  such as return path  134  of  FIG. 5  may be formed by one or more fixed conductive paths bridging slot  142  and/or one or more adjustable components such as adjustable components  176  and/or  180  as shown in  FIG. 7  (e.g., adjustable components such as tunable components  102  of  FIG. 3 ). Adjustable components  176  and  180  may sometimes be referred to herein as tuning components, tunable components, tuning circuits, tunable circuits, adjustable components, or adjustable tuning components. 
     Adjustable component  176  may bridge slot  142  at a first location along slot  142  (e.g., component  176  may be coupled between terminal  182  on antenna ground  136  and terminal  184  on peripheral conductive structures  16 ). Adjustable component  180  may bridge slot  142  at a second location along slot  142  (e.g., component  180  may be coupled between terminal  186  on antenna ground  136  and terminal  188  on peripheral conductive structures  16 ). Ground antenna feed terminal  100  may be interposed between terminal  182  and terminal  186  on antenna ground  136 . Positive antenna feed terminal  98  may be interposed between terminal  184  and terminal  188  on peripheral conductive housing structures  16 . Terminal  184  may be interposed between gap  18 - 3  and positive antenna feed terminal  98  on peripheral conductive housing structures  16 . Terminal  188  may be interposed between positive antenna feed terminal  98  and gap  18 - 2  on peripheral conductive housing structures  16 . 
     Components  176  and  180  may include switches coupled to fixed components such as inductors for providing adjustable amounts of inductance, a short circuit, and/or an open circuit between antenna ground  136  and peripheral conductive structures  16 . Components  176  and  180  may also include fixed components that are not coupled to switches or a combination of components that are coupled to switches and components that are not coupled to switches. These examples are merely illustrative and, in general, components  176  and  180  may include other components such as adjustable return path switches, switches coupled to capacitors, or any other desired components. 
     The length of arm  132  of antenna  40 - 4  may be selected so that antenna  40 - 4  radiates at desired frequencies such as frequencies in a cellular low band (e.g., a frequency band between about 600 MHz and 960 MHz), a cellular low-midband (e.g., a frequency band between about 1410 MHz and 1510 MHz), a cellular midband (e.g., a frequency band between about 1710 MHz and 2170 MHz), and a cellular ultra-high band (e.g., a frequency band between about 3400 MHz and 3600 MHz). 
     As an example, the frequency response of antenna  40 - 4  in the cellular low-midband, the cellular midband, and the cellular ultra-high band may be associated with the distance along arm  132  between return path positive antenna feed terminal  98  and gap  18 - 2  (as shown by dashed line  174 ). For example, the response of antenna  40 - 4  in the cellular low-midband and the cellular midband may be supported by a fundamental mode of arm  132  between positive antenna feed terminal  98  and gap  18 - 2 . The response of antenna  40 - 4  in the cellular ultra-high band may be supported by a harmonic mode of arm  132  between positive antenna feed terminal  98  and gap  18 - 2 . The frequency response of antenna  40 - 4  in the cellular low band may be associated with the distance along arm  132  between positive antenna feed terminal  98  and gap  18 - 3  (as shown by dashed line  172 ). 
     Adjustable component  180  may be adjusted to tune the frequency response of antenna  40 - 4  within the cellular low-midband and/or the cellular midband. As one example, adjustable component  180  may have a first state at which antenna  40 - 4  only covers the cellular midband and a second state at which antenna  40 - 4  also covers the cellular low-midband. Adjustable component  180  may form a first impedance (e.g., a short circuit) between terminal  186  and terminal  188  in the first state and second impedance (e.g., an open circuit) between terminals  186  and  188  in the second state, for example. Forming an open circuit with adjustable component  180  may, for example, extend the effective length of the portion of arm  132  thereby extending the response of antenna  40 - 4  to lower frequencies such as into the cellular low-midband. This example is merely illustrative and, in general, adjustable component  180  may perform any desired frequency adjustments for antenna  40 . Adjustable component  176  may be adjusted to tune the frequency response of antenna  40 - 4  within the cellular low band. 
     In the example of  FIG. 7 , the distance between positive antenna feed terminal  98  and gap  18 - 2  is depicted as being longer than the distance between positive antenna feed terminal  98  and gap  18 - 3  to more clearly show the components of antenna  40 - 4 . However, in practice, the distance between positive antenna feed terminal  98  and gap  18 - 3  is longer than the distance between positive antenna feed terminal  98  and gap  18 - 2  (e.g., because lower frequencies and thus longer wavelengths are supported by the length of arm  132  between positive antenna feed terminal  98  and gap  18 - 3  than the length of arm  132  between positive antenna feed terminal  98  and gap  18 - 2 ). 
     Segment  160  of peripheral conductive housing structures  16  may contribute to the frequency response of antenna  40 - 4  in the cellular high band. For example, end  192  of arm  132  at gap  18 - 2  may indirectly feed segment  160  via near-field electromagnetic coupling (e.g., across gap  18 - 2 ). Antenna currents on arm  132  may induce corresponding antenna currents on segment  160  via the near-field electromagnetic coupling. Length  162  may be selected to support a frequency response for antenna  40 - 4  in the cellular high band (e.g., length  162  may be about one-quarter of a wavelength of operation within the cellular high band). When segment  160  is indirectly fed antenna signals in this way, segment  160  may form a parasitic antenna resonating element for antenna  40 - 4  (e.g., a radiating element that is not directly fed using antenna feed  112 ). 
     In practice, indirectly feeding segment  160  may allow antenna  40 - 4  to cover some but not all of the cellular high band with satisfactory antenna efficiency. If desired, the frequency response of antenna  40 - 4  in the cellular high band may be optimized by directly feeding vertical slot  190 . 
     In order to directly feed vertical slot  190 , the signal conductor for transmission line  92 - 4  may have a branched structure that allows the signal conductor to be directly connected to both arm  132  and segment  160 . As shown in  FIG. 7 , signal conductor  94  of transmission line  92 - 4  may include a first signal conductor branch  155  coupled to positive antenna feed terminal  98  and a second signal conductor branch  154  coupled to (e.g., directly connected to) positive antenna feed terminal  158  on segment  160  of peripheral conductive housing structures  16 . Second signal conductor branch  154  and first signal conductor branch  155  of signal conductor  92  may meet at node  152  on signal conductor  92  (e.g., signal conductor branch  154  may be coupled to signal conductor branch  155  at node  152 ). 
     Antenna currents may be conveyed over both signal conductor branch  155  to arm  132  and signal conductor branch  154  to segment  160  of peripheral conductive housing structures  16 . In this way, antenna feed  112  and thus antenna  40 - 4  may have two positive antenna feed terminals (i.e., positive antenna feed terminals  98  and  158 ) that are coupled to peripheral conductive housing structures  16  on opposing sides of gap  18 - 2 . 
     Antenna currents conveyed over signal conductor branch  154  may be directly fed to vertical slot  190  (e.g., over positive antenna feed terminal  158 ) and may flow around the perimeter of vertical slot  190  (as shown by dashed path  168 ). Antenna currents flowing along path  168  may contribute a slot antenna resonance for antenna  40 - 4  within the cellular high band. The perimeter of vertical slot  190  (i.e., length  162 , width  166 , and thus the length of path  168 ) may be selected so that vertical slot  190  contributes a frequency response for antenna  40 - 4  at desired frequencies within the cellular high band. For example, the perimeter of vertical slot  190  (e.g., the length of path  168 ) may be about one-half of the wavelength of operation within the cellular high band. 
     Directly feeding vertical slot  190  in this way may optimize the frequency response of antenna  40 - 4  in the cellular high band relative to scenarios where segment  160  is only indirectly fed by end  192  of arm  132  (e.g., because vertical slot  190  offers a greater antenna area/aperture for covering the cellular high band than segment  160 ). For example, directly feeding vertical slot  190  may pull the overall frequency response of antenna  40 - 4  to higher frequencies within the cellular high band and may increase the overall antenna efficiency of antenna  40 - 4  within the cellular high band than when segment  160  is only indirectly fed. However, pulling the frequency response to higher frequencies by directly feeding vertical slot  190  in this way may deteriorate the frequency response of antenna  40 - 4  at other frequencies such as in the cellular low-midband. 
     If desired, storage and processing circuitry  28  ( FIG. 3 ) may control antenna  40 - 4  to between a first mode at which segment  160  is indirectly fed and a second mode at which vertical slot  190  is directly fed for covering the cellular high band. For example, switching circuitry such as switch  156  may be interposed on signal conductor branch  156 . Switch  156  may, for example, be a single-pole single-throw (SPST) switch. Switch  156  may be turned on (closed) or turned off (opened) based on control signals received from storage and processing circuitry  28  ( FIG. 3 ). 
     When switch  156  is turned off, an open circuit is formed between node  152  (signal conductor branch  155 ) and positive antenna feed terminal  158 . Antenna  40 - 4  is directly fed at a single point on arm  132  (e.g., positive antenna feed terminal  98 ). Segment  160  of peripheral conductive housing structures  16  is indirectly fed by end  192  of arm  132  via near-field electromagnetic coupling. Antenna  40 - 4  may exhibit a satisfactory antenna efficiency (e.g., an antenna efficiency greater than a predetermined threshold) for only some of the frequency in the cellular high band but may also exhibit satisfactory antenna efficiency at relatively low frequencies such as frequencies in the low-midband. 
     When switch  156  is turned on, node  152  is shorted to positive antenna feed terminal  158  (e.g., a short circuit path is formed between signal conductor branch  155  and positive antenna feed terminal  158 ). Antenna  40 - 4  is directly fed by transmission line  94  at two locations (e.g., positive antenna feed terminal  98  on arm  132  and positive antenna feed terminal  158  on segment  160  of peripheral conductive housing structures  16 ). Vertical slot  190  is thereby directly fed over signal conductor branch  154  and positive antenna feed terminal  158 . Antenna  40 - 4  may exhibit a satisfactory antenna efficiency for the entirety of the cellular high band (e.g., at higher frequencies than when switch  156  is turned off) but may also exhibit unsatisfactory antenna efficiency (e.g., an antenna efficiency less than a predetermined threshold) at relatively low frequencies such as frequencies in the low-midband. 
     If desired, control circuitry  20  ( FIG. 3 ) may adjust switch  156  in real time to tune the frequency response of antenna  40 - 4  based on the needs and/or operating environment of device  10 . For example, control circuitry  20  may turn switch  156  off when antenna  40 - 4  is assigned a frequency in the cellular low-midband or when communications in the cellular low-midband is otherwise prioritized over communications in the cellular high band (e.g., by software running on device  10  or by external equipment such as a cellular base station). Control circuitry  20  may turn switch  156  on when antenna  40 - 4  is assigned a frequency in the cellular high band (e.g., at relatively high frequencies in the cellular high band) or when communications in the cellular high band is otherwise prioritized over communications in the cellular low-midband. In this way, control circuitry  20  may dynamically adjust the number of positive antenna feed terminals that are used to feed antenna  40 - 4  using a single transmission line  92 - 4  in real time (e.g., to optimize wireless performance of antenna  40 - 4  in desired frequency bands). 
     In another suitable arrangement, control circuitry  20  may adjust component  180  to extend the frequency response of antenna  40 - 4  to frequencies in the cellular low-midband when antenna  40 - 4  is fed using both positive antenna feed terminals  98  and  158  (e.g., when switch  156  is turned on). As an example, adjustable component  180  may be controlled to form an open circuit (infinite impedance) between terminals  186  and  188  to pull the frequency response of antenna  40 - 4  to frequencies in the cellular low-midband. Adjustable component  180  may, for example, pull the response of antenna  40 - 4  to frequencies in the cellular low-midband without substantially affecting the response of antenna  40 - 4  in the cellular high band (e.g., because adjustable component  180  bridges slot  142  and does not overlap vertical slot  190 ). In this scenario, switch  156  may be omitted if desired. 
     Feeding antenna  40 - 4  using antenna feed  112  may limit the length of arm  132  that is used to cover the cellular low band. This may limit the overall antenna efficiency of antenna  40 - 4  in the cellular low band. If desired, antenna  40 - 4  may include an additional antenna feed  112 ′ coupled to an additional transmission line  92 - 4 ′. 
     Additional antenna feed  112 ′ may include a positive antenna feed terminal  98 ′ coupled to arm  132  and a ground antenna feed terminal  100 ′ coupled to antenna ground  136 . Terminal  182  of adjustable component  176  may, for example, be interposed between ground antenna feed terminal  100 ′ and ground antenna feed terminal  100  on antenna ground  136 . Positive antenna feed terminal  98 ′ may be interposed between terminal  184  and gap  18 - 3  on peripheral conductive housing structures  16 . Transmission line  92 - 4 ′ may include a signal conductor  94 ′ coupled to positive antenna feed terminal  98 ′ across slot  142  and a ground conductor  96 ′ coupled to ground antenna feed terminal  100 ′. 
     Control circuitry may control wireless communications circuitry  34  to perform wireless communications over antenna  40 - 4  using a selected one of transmission lines  92 - 4 ′ and  92 - 4  at a given time (e.g., using a selected one of antenna feeds  112 ′ and  112 ). For example, switching circuitry may couple transmission lines  92 - 4 ′ and  92 - 4  to transceiver circuitry  26  ( FIG. 2 ). The switching circuitry may have a first state at which transmission line  92 - 4 ′ and antenna feed  112 ′ are active (e.g., coupled to transceiver circuitry  26 ) and at which transmission line  92 - 4  and antenna feed  112  are inactive (e.g., decoupled from transceiver circuitry  26 ). The switching circuitry may have a second state at which transmission line  92 - 4 ′ and antenna feed  112 ′ are inactive and at which transmission line  92 - 4  and antenna feed  112  are active. 
     When antenna feed  112 ′ is active, the length of arm  132  between positive antenna feed terminal  98 ′ and gap  18 - 2  may support a frequency response of antenna  40 - 4  within the cellular low band. This length is greater than the length of arm  132  that supports frequencies in the cellular low band when antenna feed  112  is active (e.g., the length of arm  132  between positive antenna feed terminal  98  and gap  18 - 3 ). Providing a greater length of arm  132  for covering the cellular low band (e.g., when feed  112 ′ is active) may increase the overall antenna efficiency and bandwidth of antenna  40 - 4  within the cellular low band relative to scenarios where feed  112  is active. Adjustable component  176  may be used to adjust the frequency response of antenna  40 - 4  within the cellular low band regardless of which feed is active if desired. 
     Control circuitry  20  ( FIG. 3 ) may select a given one of antenna feeds  112  and  112 ′ to use in real time to tune the frequency response of antenna  40 - 4  based on the needs and/or operating environment of device  10 . For example, control circuitry  20  activate feed  112 ′ and deactivate feed  112  when antenna  40 - 4  is assigned a frequency in the cellular low band or when communications in the cellular low band is otherwise prioritized over communications in other bands (e.g., by software running on device  10  or by external equipment such as a cellular base station). Control circuitry  20  may activate feed  112  and deactivate feed  112 ′ when antenna  40 - 4  is assigned a frequency higher than the cellular low band or when communications in frequencies higher than the cellular low band are otherwise prioritized. 
     In this way, control circuitry  20  may dynamically adjust both the number of positive antenna feed terminals that are used to feed antenna  40 - 4  using a single transmission line  92 - 4  and the antenna feed (transmission line) that is used to feed antenna  40 - 4  in real time (e.g., to optimize wireless performance of antenna  40 - 4  in desired frequency bands). In scenarios where switch  156  and antenna feed  112 ′ are formed in antenna  40 - 4 , control circuitry  20  may adjust antenna  40 - 4  so that one or two of three possible positive antenna feed terminals are used to feed antenna  40 - 4  at any given time. For example, control circuitry  20  may configure antenna  40 - 4  to be fed using a single positive antenna feed terminal by either activating antenna feed  112 ′ (while antenna feed  112  is deactivated) or by activating antenna feed  112  while antenna feed  112  is deactivated and while switch  156  is turned off. Control circuitry  20  may configure antenna  40 - 4  to be fed using two antenna feed terminals by activating antenna feed  112  while antenna feed  112 ′ is deactivated and while switch  156  is turned on. 
     Switch  156 , signal conductor branch  154 , signal conductor branch  155 , adjustable component  176 , and/or adjustable component  180  may overlap slot  142  if desired. Switch  156 , signal conductor branch  154 , signal conductor branchy  155 , adjustable component  176 , and/or adjustable component  180  may be formed between peripheral conductive housing structures  16  and antenna ground  136  using any desired structures. For example, adjustable component  176 , adjustable component  180 , switch  156 , signal conductor branch  155 , and/or signal conductor branch  154  may be formed on a printed circuit such as a flexible printed circuit board that is coupled between peripheral conductive housing structures  16  and antenna ground  136 . 
     Antenna ground  136  may include a conductive layer of housing  12  (e.g., a conductive backplate for device  10 ). If desired, additional conductive layers may be used to form portions of antenna ground  136 . For example, antenna ground  136  may include conductive portions of display  14  of  FIG. 1  (e.g., conductive portions of a display panel, a conductive plate for supporting the display panel, and/or a conductive frame for supporting the conductive plate and/or the display panel). Grounded terminals  100 ′,  182 ,  100 , and/or  186  may be coupled to the conductive layer of housing  12 , the conductive portion of display  14 , or other conductive structures that form antenna ground  136 . If desired, conductive structures such as vertical conductive interconnect structures (e.g., a bracket, clip, spring, pin, screw, solder, weld, conductive adhesive, wire, metal strip, etc.) may be used to short the conductive layer of housing  12  to the conductive portion of display  14  that forms a part of antenna ground  136  (e.g., at the locations of terminals  100 ′,  182 ,  100 , and/or  186 ). Electrically connecting different components of the device ground (e.g., antenna ground  136  in  FIG. 7 ) with vertical conductive interconnect structures may ensure that the conductive structures that are located the closest to resonating element arm  132  are held at a ground potential and form a part of antenna ground  136 . This may serve to optimize the antenna efficiency of antenna  40 , for example. Conductive interconnect structures such as brackets, clips, springs, pins, screws, solders, welds, conductive adhesive, etc. may be used to couple terminals  98 ′,  184 ,  98 ,  188 , and/or  158  to peripheral conductive housing structures  16 . 
     The example of  FIG. 7  is merely illustrative. In one suitable arrangement, antenna feed  112 ′, transmission line  92 - 4 ′, and switch  156  may be omitted. In another suitable arrangement, antenna feed  112 ′ may be omitted. In yet another suitable arrangement, adjustable component  180  may be omitted. In still another suitable arrangement, adjustable component  180  and switch  156  may be omitted. In general, any desired combination of antenna feed  112 ′ (and thus transmission line  92 - 4 ′), adjustable component  176 , adjustable component  180 , and switch  156  may be omitted. Additional adjustable components may be coupled between arm  132  and antenna ground  136 , between different portions of antenna ground  136 , between antenna ground  136  and  136  and segment  160 , across gap  18 - 3 , across gap  18 - 2 , and/or between different portions of arm  132  if desired. 
     While the example of  FIG. 7  shows antenna structures for implementing antenna  40 - 4  in device  10 , these structures may be used to implement any one of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , or  40 - 4  of device  10  ( FIG. 4 ) and/or may be used to implement any desired antennas  40  in device  10 . If desired, the structures used to implement antenna  40 - 4  of  FIG. 7  may be used to implement more than one of antennas  40 - 2 ,  40 - 3 , and  40 - 1  of device  10  ( FIG. 4 ). In this way, any frequency adjustments performed to antenna  40 - 4  may also be performed (e.g., simultaneously or concurrently) on the other antennas  40  in device  10  for covering the same frequency bands under a MIMO scheme. In one suitable arrangement, antennas  40 - 1  and  40 - 4  may both be implemented using the antenna structures of antenna  40 - 4  of  FIG. 7  (e.g., for performing at least 2× MIMO communications in some bands and optionally 4× MIMO communications with antennas  40 - 2  and  40 - 3  in other bands). In another suitable arrangement, each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may be implemented using the antenna structures of antenna  40 - 4  (e.g., for performing 4× MIMO communications in each frequency band). 
     Antenna  40 - 3  of  FIG. 4  may, if desired, include an antenna resonating element formed from the segment of peripheral conductive housing structures  16  extending between gaps  18 - 1  and  18 - 3  of  FIG. 7  (e.g., using the same antenna structures as antenna  40 - 4  of  FIG. 7  or using other antenna structures). In these scenarios, gap  18 - 3  may provide mechanical separation between arms  132  of antenna  40 - 4  and the antenna resonating element of antenna  40 - 3 . This mechanical separation may serve to electromagnetically isolate antenna  40 - 3  from antenna  40 - 4  when antennas  40 - 3  and  40 - 4  operate at the same frequency (e.g., for performing communications using a MIMO scheme). 
       FIG. 8  is a flow chart of illustrative steps involved in operating device  10  to ensure satisfactory performance for antenna  40 - 4  of  FIG. 7  in all desired frequency bands of interest. 
     At step  200  of  FIG. 8 , storage and processing circuitry  28  may monitor the operating environment of device  10  and/or frequencies to use for performing wireless communications. The frequencies to use may be determined based on software running on storage processing circuitry  28  (e.g., software controlling wireless communications for device  10 ) and/or based on an assignment received from external equipment like a wireless base station. 
     Storage and processing circuitry  28  may, in general, use any suitable type of sensor measurements, wireless signal measurements, operation information, or antenna measurements to determine how device  10  is being used (e.g., to determine the operating environment of device  10 ). For example, control circuitry  28  may use sensors such as temperature sensors, capacitive proximity sensors, light-based proximity sensors, resistance sensors, force sensors, touch sensors, connector sensors that sense the presence of a connector in a connector port or that detect the presence or absence of data transmission through a connector port, sensors that detect whether wired or wireless headphones are being used with device  10 , sensors that identify a type of headphone or accessory device that is being used with device  10  (e.g., sensors that identify an accessory identifier identifying an accessory that is being used with device  10 ), or other sensors to determine how device  10  is being used. Control circuitry  28  may also use information from an orientation sensor such as an accelerometer in device  10  to help determine whether device  10  is being held in a position characteristic of right hand use or left hand use (or is being operated in free space). Control circuitry  28  may also use information about a usage scenario of device  10  in determining how device  10  is being used (e.g., information identifying whether audio data is being transmitted through ear speaker  26  of  FIG. 1 , information identifying whether a telephone call is being conducted, information identifying whether a microphone on device  10  is receiving voice signals, etc.). 
     If desired, an impedance sensor or other sensor may be used in monitoring the impedance of antenna  40 - 4  or part of antenna  40 - 4 . Different antenna loading scenarios may load antenna  40 - 4  differently, so impedance measurements may help determine whether device  10  is being gripped by a user&#39;s left or right hand or is being operated in free space. Another way in which storage and processing circuitry  28  may monitor antenna loading conditions involves making received signal strength measurements on radio-frequency signals being received with antenna  40 - 4 . In this example, the adjustable circuitry of antenna  40 - 4  can be toggled between different settings and an optimum setting for antenna  40 - 4  can be identified by choosing a setting that maximizes received signal strength. In general, any desired combinations of one or more of these measurements or other measurements may be processed by storage and processing circuitry  28  to identify how device  10  is being used (i.e., to identify the operating environment of device  10 ). 
     At step  202 , storage and processing circuitry  28  may adjust the configuration of antenna  40 - 4  (e.g., antenna settings for antenna  40 - 4 ) based on the current operating environment of device  10  and/or the frequencies to use for communications (e.g., based on data or information gathered while processing step  242 ). Storage and processing circuitry  28  may select a given one of feeds  112  and  112 ′ to activate, may adjust the state of switch  156 , may adjust component  176 , and/or may adjust component  180  of  FIG. 7  based on the information gathered while processing step  200  of  FIG. 8 . 
     At step  204 , antenna  40 - 4  may be used to transmit and receive wireless data using the antenna settings selected at step  202 . This process may be performed continuously, as indicated by path  206 . In this way, antenna  40 - 4  may be dynamically adjusted in real time based on the operating environment and needs of device  10 . Similar steps may be used to adjust antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and/or other antennas  40  in device  10  if desired. 
       FIG. 9  is a graph in which antenna performance (antenna efficiency) has been plotted as a function of operating frequency for antenna  40 - 4  of  FIG. 7 . As shown in  FIG. 9 , curve  210  plots an exemplary antenna efficiency of antenna  40 - 4  while antenna feed  112  is active, antenna feed  112 ′ is inactive, and switch  156  is turned off. 
     When placed in this configuration, the length of arm  132  between positive antenna feed terminal  98  and gap  18 - 3  may support a response peak in a first frequency band such as cellular low band LB (e.g., a frequency band between about 600 MHz and 960 MHz). The length of arm  132  between positive antenna feed terminal  98  and gap  18 - 2  may support a response peak that extends across a second frequency band such as cellular low-midband LMB (e.g., a frequency band between about 1410 MHz and 1510 MHz) and a third frequency band such as cellular midband MB (e.g., a frequency band between about 1710 MHz and 2170 MHz). End  192  of arm  132  may indirectly feed segment  160  of peripheral conductive housing structures  16  to support a response peak in a fourth frequency band such as cellular high band HB (e.g., a frequency band between about 2300 MHz and 2700 MHz). A harmonic mode of the portion of arm  132  between positive antenna feed terminal  98  and gap  18 - 2  may support a response peak in a fifth frequency band such as cellular ultra-high band UHB (e.g., a frequency band between about 3400 MHz and 3600 MHz). 
     As shown by curve  210 , the response peak in cellular high band HB may only cover relatively low frequencies in cellular high band HB without providing satisfactory efficiency at higher frequencies in cellular high band HB. In order to cover the entirety of cellular high band HB with satisfactory efficiency, storage and processing circuitry  28  may turn on switch  156 . 
     Curve  212  of  FIG. 9  plots an exemplary antenna efficiency of antenna  40 - 4  while antenna feed  112  is active, antenna feed  112 ′ is inactive, and switch  156  is turned on. Curve  212  also illustrates the efficiency of antenna  40 - 4  in scenarios where switch  156  is omitted and antenna feed  112  is active (while antenna feed  112 ′ is inactive). 
     When placed in this configuration, vertical slot  190  is directly fed over positive antenna feed terminal  158  and signal conductor branch  154 . This may serve to pull the coverage of antenna  40 - 4  in cellular high band HB to higher frequencies as well as to increase the overall efficiency of antenna  40 - 4  within cellular high band HB. Antenna  40 - 4  may thereby convey radio-frequency signals at higher frequencies within cellular high band HB with satisfactory antenna efficiency than in scenarios where transmission line  92 - 4  is only coupled to antenna  40 - 4  over a single positive antenna feed terminal  98  (as shown by curve  210  of  FIG. 9 ). 
     Directly feeding vertical slot  190  as shown by curve  212  may also reduce antenna efficiency within the second frequency band (e.g., within cellular low-midband LMB). If desired, storage and processing circuitry  28  may adjust component  180  of  FIG. 7  to pull the frequency response of antenna  40 - 4  downwards to also cover cellular low-midband LMB without substantially affecting coverage in cellular high band HB (as shown by arrow  216  of  FIG. 9 ). 
     In order to further optimize antenna efficiency across low band LB, storage and processing circuitry  28  may activate antenna feed  112 ′ and deactivate antenna feed  112  of  FIG. 7 . Curve  214  of  FIG. 9  plots an exemplary antenna efficiency of antenna  40 - 4  while antenna feed  112 ′ is active and antenna feed  112  is inactive. When placed in this configuration, a greater length of arm  132  is available for covering cellular low band LB than in scenarios where antenna feed  112  is used, thereby increasing the overall antenna efficiency and/or bandwidth for antenna  40 - 4  within cellular low band LB relative to the configurations associated with curves  210  and  212 . 
     The example of  FIG. 9  is merely illustrative. In general, antenna  40 - 4  may cover any desired bands at any desired frequencies (e.g., antenna  40 - 4  may exhibit any desired number of efficiency peaks extending over any desired frequency bands). Curves  210 ,  212 , and  214  may have other shapes if desired. 
     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: 20180222
Publication Date: 20201110
Grant Date: 20201110
Priority Date: 20180222
Inventors: AYALA VAZQUEZ, ENRIQUE
HU, HONGFEI
JIN, NANBO
GAO, XU
TONG, ERICA J.
IRCI, Erdinc
WANG, HAN
PASCOLINI, MATTIA
FROESE, KEVIN M.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/285", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0485", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0485", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/285", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 67618118