PATENT DOCUMENT

Publication Number: US-10693516-B2
Application Number: US-201816017847-A
Country: US
Kind Code: B2

Title: Electronic device having adjustable antenna settings

Abstract:
An electronic device may include control circuitry, sensors, and wireless circuitry having antennas. The sensors may generate sensor data that is used by the control circuitry to identify an operating environment for the device. The sensor data may include a grip map generated by a touch-sensitive display, infrared facial recognition image signals or other image signals, an angle of arrival of sound received by a set of microphones, impedance data from an impedance sensor, and any other desired sensor data. The control circuitry may use the sensor data, radio-frequency spatial ranging data, information about whether audio is being played over an ear speaker, and/or information about communications protocols in use to identify the operating environment. The control circuitry may adjust antenna settings for the wireless circuitry based on the identified operating environment to ensure that the antennas operate with satisfactory antenna efficiency regardless of operating conditions.

Claims:
What is claimed is: 
     
       1. An electronic device having opposing first and second faces, comprising:
 a housing; 
 a touch-sensitive display at the first face; 
 an image sensor at the first face; 
 a plurality of microphones in the housing that are configured to receive sound and to generate audio signals in response to the sound; 
 wireless communications circuitry configured to convey radio-frequency signals over a plurality of antennas using antenna settings; and 
 control circuitry configured to adjust the antenna settings based on sensor data, wherein the sensor data comprises data selected from the group consisting of:
 a grip map generated by the touch-sensitive display, and 
 an angle of arrival of the sound received by the plurality of microphones. 
 
 
     
     
       2. The electronic device defined in  claim 1 , further comprising:
 a light source at the first face and configured to emit infrared light, wherein the image sensor is configured to receive a reflected version of the infrared light emitted by the light source and the control circuitry is further configured to detect an object in image signals generated by the image sensor in response to the reflected version of the infrared light emitted by the light source and to adjust the antenna settings based on the detected object in the image signals. 
 
     
     
       3. The electronic device defined in  claim 1 , wherein the control circuitry is further configured to generate a depth map based on image signals generated by the image sensor and to adjust the antenna settings based on the depth map. 
     
     
       4. The electronic device defined in  claim 1 , further comprising:
 an orientation sensor configured to generate orientation sensor data, wherein the control circuitry is further configured to adjust the antenna settings based on the orientation sensor data. 
 
     
     
       5. The electronic device defined in  claim 1 , wherein the grip map comprises a set of locations on the touch-sensitive display that are in contact with an external object. 
     
     
       6. The electronic device defined in  claim 5 , wherein the touch-sensitive display is configured to gather force data indicative of a pressure applied to the touch-sensitive display and the grip map comprises force data associated with each of the locations in the set of locations. 
     
     
       7. The electronic device defined in  claim 1 , wherein the antenna settings comprise a selected pair of antennas in the plurality of antennas that are configured to concurrently transmit the radio-frequency signals at a given frequency under a multiple-input and multiple-output (MIMO) scheme. 
     
     
       8. The electronic device defined in  claim 1 , wherein the antenna settings comprise a setting selected from the group consisting of: a set of active antennas in the plurality of antennas, a set of active antenna feeds for the plurality of antennas, operating frequencies for the plurality of antennas, maximum transmit power levels for the plurality of antennas, and tuning settings for the plurality of antennas. 
     
     
       9. The electronic device defined in  claim 1 , wherein the housing comprises peripheral conductive housing structures that run along a periphery of the electronic device, the electronic device has a length, a width that is less than the length, and a height that is less than the width, the peripheral conductive housing structures comprise first and second sidewalls that run along the length and third and fourth sidewalls that run along the width, the plurality of antennas comprises first, second, third, and fourth antennas, the first antenna includes a first resonating element formed from the first and second sidewalls, the second antenna includes a second resonating element formed from the second and third sidewalls, the third antenna includes a third resonating element formed from the third and fourth sidewalls, the fourth antenna includes a fourth resonating element formed from the fourth and first sidewalls, the first resonating element is separated from the second resonating element by a first gap in the second sidewall, and the third resonating element is separated from the fourth resonating element by a second gap in the fourth sidewall. 
     
     
       10. The electronic device defined in  claim 1 , wherein the control circuitry is further configured to place an antenna in the plurality of antennas in:
 a free space operating mode in response to determining that the electronic device is being operated in the first environment, 
 a first non-free space operating mode in response to determining that the electronic device is being operated in the second environment, 
 a second non-free space operating mode in response to determining that the electronic device is being operated in the third environment, and 
 a third non-free space operating mode in response to determining that the electronic device is being operated in the fourth environment, wherein the antenna is configured to transmit the radio-frequency signals using a first maximum transmit power level in the free space operating mode and using respective second, third, and fourth maximum transmit power levels in the first, second, and third non-free space operating modes, the first maximum transmit power level being greater than each of the second, third, and fourth maximum transmit power levels. 
 
     
     
       11. The electronic device defined in  claim 1 , further comprising:
 an impedance sensor coupled to the plurality of antennas and configured to generate radio-frequency phase and magnitude information associated with the plurality of antennas, wherein the control circuitry is further configured to generate radio-frequency spatial ranging data indicative of a distance between the electronic device and an object external to the electronic device based on a radio-frequency signal transmitted by a given antenna in the plurality of antennas and a reflected version of the transmitted radio-frequency signal received using the given antenna, and the control circuitry is further configured to adjust the antenna settings based on the radio-frequency spatial ranging data and the radio-frequency phase and magnitude information. 
 
     
     
       12. An electronic device having opposing first and second faces, comprising:
 a housing, wherein the housing comprises peripheral conductive housing structures that run along a periphery of the electronic device, the electronic device has a length, a width that is less than the length, and a height that is less than the width, the peripheral conductive housing structures comprise first and second sidewalls that run along the length and third and fourth sidewalls that run along the width; 
 a touch-sensitive display at the first face; 
 a light source at the first face and configured to emit infrared light; 
 an image sensor at the first face and configured to receive a reflected version of the infrared light emitted by the light source; 
 a plurality of microphones in the housing that are configured to receive sound and to generate audio signals in response to the sound; 
 wireless communications circuitry configured to convey radio-frequency signals over a plurality of antennas using antenna settings, wherein the plurality of antennas comprises antennas formed from corresponding portions of the first, second, third, and fourth sidewalls; and 
 control circuitry configured to adjust the antenna settings based on sensor data, wherein the sensor data comprises data selected from the group consisting of:
 a grip map generated by the touch-sensitive display, 
 an angle of arrival of the sound received by the plurality of microphones, and 
 image signals generated by the image sensor in response to the reflected version of the infrared light emitted by the light source. 
 
 
     
     
       13. The electronic device defined in  claim 12 , wherein the antennas formed from the corresponding portions of the first, second, third, and fourth sidewalls comprise a first antenna formed from a first portion of the third sidewall, a second antenna formed from a second portion of the third sidewall. 
     
     
       14. The electronic device defined in  claim 13 , wherein the antennas formed from the corresponding portions of the first, second, third, and fourth sidewalls further comprise a third antenna formed from a first portion of the fourth sidewall, and a fourth antenna formed from a second portion of the fourth sidewall. 
     
     
       15. The electronic device defined in  claim 12 , wherein the control circuitry is further configured to place an antenna in the plurality of antennas in:
 a free space operating mode in response to determining that the electronic device is being operated in the first environment, 
 a first non-free space operating mode in response to determining that the electronic device is being operated in the second environment, 
 a second non-free space operating mode in response to determining that the electronic device is being operated in the third environment, and 
 a third non-free space operating mode in response to determining that the electronic device is being operated in the fourth environment, wherein the antenna is configured to transmit the radio-frequency signals using a first maximum transmit power level in the free space operating mode and using respective second, third, and fourth maximum transmit power levels in the first, second, and third non-free space operating modes, the first maximum transmit power level being greater than each of the second, third, and fourth maximum transmit power levels. 
 
     
     
       16. The electronic device defined in  claim 15 , wherein the first environment comprises a free space environment, the second environment comprises an environment in which the electronic device is placed on a surface in a vehicle, the third environment comprises an environment in which the electronic device is being held by a user, and the fourth environment comprises an environment in which the electronic device is being held against a head of the user. 
     
     
       17. The electronic device defined in  claim 15 , wherein the antenna comprises a tunable component and the control circuitry is configured to place the antenna in a selected one of a plurality of sub-modes of operation by adjusting the tunable component after the antenna has been placed in the third non-free space operating mode. 
     
     
       18. The electronic device defined in  claim 12 , further comprising:
 an impedance sensor coupled to the plurality of antennas and configured to generate radio-frequency phase and magnitude information associated with the plurality of antennas, wherein the control circuitry is further configured to generate radio-frequency spatial ranging data indicative of a distance between the electronic device and an object external to the electronic device based on a radio-frequency signal transmitted by a given antenna in the plurality of antennas and a reflected version of the transmitted radio-frequency signal received using the given antenna, and the control circuitry is further configured to adjust the antenna settings based on the radio-frequency spatial ranging data and the radio-frequency phase and magnitude information. 
 
     
     
       19. An electronic device having opposing first and second faces, comprising:
 a housing; 
 a touch-sensitive display at the first face; 
 an image sensor at the first face; 
 a microphone in the housing; 
 wireless communications circuitry configured to convey radio-frequency signals over a plurality of antennas using antenna settings; and 
 control circuitry configured to adjust the antenna settings based on a grip map generated by the touch-sensitive display, wherein the grip map comprises a set of locations on the touch-sensitive display that are in contact with an external object. 
 
     
     
       20. The electronic device defined in  claim 19 , wherein the touch-sensitive display is configured to gather force data indicative of a pressure applied to the touch-sensitive display and the grip map comprises force data associated with each of the locations in the set of locations.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. 
     It can be challenging to form electronic device antenna structures with desired attributes. In some electronic devices, antennas are bulky. In other devices, antennas are compact, but are sensitive to the position of the antennas relative to external objects. If care is not taken, antennas may become detuned, may emit wireless signals with a power that is more or less than desired, or may otherwise not perform as expected. In addition, it is often difficult to perform wireless communications with a satisfactory data rate (data throughput), especially as software applications performed by electronic devices become increasingly data hungry. 
     It would therefore be desirable to be able to provide improved wireless communications circuitry for electronic devices. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry and a housing having peripheral conductive housing structures. The peripheral conductive housing structures may be used to form resonating elements for a set of antennas. If desired, the antennas may concurrently operate at one or more of the same frequencies under a multiple-input and multiple-output (MIMO) protocol. 
     The electronic device may monitor its operating environment using one or more sensors. For example, the electronic device may include a touch-sensitive display. The touch-sensitive display may generate a grip map that identifies locations on the touch-sensitive display that are in contact with an external object such as the hand of a user. The touch-sensitive display may also be force-sensitive. The grip map may include force data for each of the identified locations in contact with the external object. 
     The electronic device may also include an image sensor and a light source. The light source may emit infrared light. The image sensor may generate image data in response to a reflected version of the infrared light emitted by the light source. Control circuitry in the electronic device may perform user authentication operations using the image data, may generate a depth map using the image data, and/or may perform object detection operations based on the image data. 
     The electronic device may also include multiple microphones distributed across the device. The microphones may gather audio signals in response to a sound received by the microphones. The control circuitry may process the audio signals to determine an angle of arrival of the sound. The electronic device may include other sensors such as an impedance sensor that generates impedance data, a proximity sensor that generates proximity data, an ambient light sensor that generates ambient light data, an orientation and motion sensor that generates orientation and motion data, and other sensors. 
     If desired, the control circuitry may gather spatial ranging data indicative of a distance between the device and an external object using transmitted and reflected radio-frequency signals. The control circuitry may use combinations of one or more of these types of data, information about whether audio is being played through an ear speaker on the device, and/or information about wireless communications protocols that are being used by device  10  to identify an operating environment for the electronic device. 
     The control circuitry may adjust antenna settings for the wireless communications circuitry to place the circuitry into one of a number of different operating modes based on the identified operating environment. The operating modes may include a head mode for scenarios where the device is being held to the user&#39;s head, a hand mode for scenarios where the device is being held by the user away from their head, a free space mode, and a vehicle mode for scenarios where the device is resting on a surface inside a vehicle. 
     The antenna settings may include a set of active antennas to use for performing MIMO operations, a set of active antenna feeds to use for conveying radio-frequency signals, maximum transmit power levels, operating frequencies, and/or antenna tuning settings, as examples. In this way, the control circuitry may control the wireless communications circuitry to ensure that satisfactory antenna efficiency is achieved regardless of operating environment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of illustrative circuitry in an electronic device in accordance with an embodiment. 
         FIG. 3  is a schematic diagram of illustrative wireless communications circuitry in accordance with an embodiment. 
         FIG. 4  is a diagram of illustrative wireless circuitry including multiple antennas for performing multiple-input and multiple-output (MIMO) communications in accordance with an embodiment. 
         FIG. 5  is a schematic diagram of an illustrative inverted-F antenna in accordance with an embodiment. 
         FIG. 6  is a schematic diagram of an illustrative slot antenna in accordance with an embodiment. 
         FIG. 7  is a top view of illustrative antennas formed from housing structures in an electronic device in accordance with an embodiment. 
         FIG. 8  is a flow chart of illustrative steps that may be involved in adjusting wireless communications circuitry based on sensor data and other data in accordance with an embodiment. 
         FIG. 9  is a state diagram showing illustrative operating modes for wireless communications circuitry in accordance with an embodiment. 
         FIG. 10  is a flow chart of illustrative steps that may be involved in adjusting wireless communications circuitry based on identified operating modes of the wireless communications circuitry in accordance with an embodiment. 
         FIG. 11  is a perspective view of an illustrative electronic device having sensors for gathering sensor data that is used to adjust wireless communications circuitry in accordance with an embodiment. 
         FIG. 12  is a side view of an illustrative electronic device having multiple microphones for gathering microphone data that is used to adjust wireless communications circuitry in accordance with an embodiment. 
         FIG. 13  is a plot of antenna performance (antenna efficiency) of an illustrative antenna when operated using different antenna settings in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. 
     The wireless communications circuitry may include one or more antennas. The antennas of the wireless communications circuitry can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. 
     The conductive electronic device structures may include conductive housing structures. The housing structures may include peripheral structures such as peripheral conductive structures that run around the periphery of the electronic device. The peripheral conductive structures may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, may have portions that extend upwards from an integral planar rear housing (e.g., to form vertical planar sidewalls or curved sidewalls), and/or may form other housing structures. 
     Gaps may be formed in the peripheral conductive structures that divide the peripheral conductive structures into peripheral segments. One or more of the segments may be used in forming one or more antennas for electronic device  10 . Antennas may also be formed using an antenna ground plane and/or an antenna resonating element formed from conductive housing structures (e.g., internal and/or external structures, support plate structures, etc.). 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Device  10  may also be a set-top box, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, a wireless access point, wireless base station, an electronic device incorporated into a kiosk, building, or vehicle, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may be mounted on the front face of device  10 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or may be insensitive to touch. The rear face of housing  12  (i.e., the face of device  10  opposing the front face of device  10 ) may have a rear housing wall (e.g., a planar housing wall). The rear housing wall may have slots that pass entirely through the rear housing wall and that therefore separate housing wall portions (rear housing wall portions and/or sidewall portions) of housing  12  from each other. The rear housing wall may include conductive portions and/or dielectric portions. If desired, the rear housing wall may include a planar metal layer covered by a thin layer or coating of dielectric such as glass, plastic, sapphire, or ceramic. Housing  12  (e.g., the rear housing wall, sidewalls, etc.) may also have shallow grooves that do not pass entirely through housing  12 . The slots and grooves may be filled with plastic or other dielectric. If desired, portions of housing  12  that have been separated from each other (e.g., by a through slot) may be joined by internal conductive structures (e.g., sheet metal or other metal members that bridge the slot). 
     Display  14  may include pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable pixel structures. A display cover layer such as a layer of clear glass or plastic may cover the surface of display  14  or the outermost layer of display  14  may be formed from a color filter layer, thin-film transistor layer, or other display layer. If desired, buttons may pass through openings in the cover layer. The cover layer may also have other openings such as an opening for speaker port  8 . 
     Housing  12  may include peripheral housing structures such as structures  16 . Structures  16  may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape with four edges, structures  16  may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges (as an example). Peripheral structures  16  or part of peripheral structures  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or that helps hold display  14  to device  10 ). Peripheral structures  16  may, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral housing structures  16  may be formed of a conductive material such as metal and may therefore sometimes be referred to as peripheral conductive housing structures, conductive housing structures, peripheral metal structures, peripheral conductive housing sidewall structures, peripheral conductive housing sidewalls, peripheral conductive sidewalls, or a peripheral conductive housing member (as examples). Peripheral conductive housing structures  16  may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, three, four, five, six, or more than six separate structures may be used in forming peripheral conductive housing structures  16 . 
     It is not necessary for peripheral conductive housing structures  16  to have a uniform cross-section. For example, the top portion of peripheral conductive housing structures  16  may, if desired, have an inwardly protruding lip that helps hold display  14  in place. The bottom portion of peripheral conductive housing structures  16  may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). Peripheral conductive housing structures  16  may have substantially straight vertical sidewalls, may have sidewalls that are curved, or may have other suitable shapes. In some configurations (e.g., when peripheral conductive housing structures  16  serve as a bezel for display  14 ), peripheral conductive housing structures  16  may run around the lip of housing  12  (i.e., peripheral conductive housing structures  16  may cover only the edge of housing  12  that surrounds display  14  and not the rest of the sidewalls of housing  12 ). 
     If desired, housing  12  may have a conductive rear surface or wall. For example, housing  12  may be formed from a metal such as stainless steel or aluminum. The rear surface of housing  12  may lie in a plane that is parallel to display  14 . In configurations for device  10  in which the rear surface of housing  12  is formed from metal, it may be desirable to form parts of peripheral conductive housing structures  16  as integral portions of the housing structures forming the rear surface of housing  12 . For example, a conductive rear housing wall of device  10  may be formed from a planar metal structure and portions of peripheral conductive housing structures  16  on the sides of housing  12  may be formed as flat or curved vertically extending integral metal portions of the planar metal structure. Housing structures such as these may, if desired, be machined from a block of metal and/or may include multiple metal pieces that are assembled together to form housing  12 . The conductive rear wall of housing  12  may have one or more, two or more, or three or more portions. Peripheral conductive housing structures  16  and/or the conductive rear wall of housing  12  may form one or more exterior surfaces of device  10  (e.g., surfaces that are visible to a user of device  10 ) and/or may be implemented using internal structures that do not form exterior surfaces of device  10  (e.g., conductive housing structures that are not visible to a user of device  10  such as conductive structures that are covered with layers such as thin cosmetic layers, protective coatings, and/or other coating layers that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide structures  16  and/or the conductive rear wall of housing  12  from view of the user). 
     Display  14  may have an array of pixels that form an active area AA that displays images for a user of device  10 . An inactive border region such as inactive area IA may run along one or more of the peripheral edges of active area AA. 
     Display  14  may include conductive structures such as an array of capacitive electrodes for a touch sensor, conductive lines for addressing pixels, driver circuits, etc. Housing  12  may include internal conductive structures such as metal frame members and a planar conductive housing member (sometimes referred to as a backplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more metal parts that is welded or otherwise connected between opposing sides of peripheral conductive housing structures  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 regions  20  and  22  of device  10  of  FIG. 1 ), along one or more edges of a device housing, in the center of a device housing, in other suitable locations, or in one or more of these locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral conductive housing structures  16  may be provided with peripheral gap structures. For example, peripheral conductive housing structures  16  may be provided with one or more gaps such as gaps  18 , as shown in  FIG. 1 . The gaps in peripheral conductive housing structures  16  may be filled with dielectric such as polymer, ceramic, glass, air, other dielectric materials, or combinations of these materials. Gaps  18  may divide peripheral conductive housing structures  16  into one or more peripheral conductive segments. There may be, for example, two peripheral conductive segments in peripheral conductive housing structures  16  (e.g., in an arrangement with two of gaps  18 ), three peripheral conductive segments (e.g., in an arrangement with three of gaps  18 ), four peripheral conductive segments (e.g., in an arrangement with four of gaps  18 ), six peripheral conductive segments (e.g., in an arrangement with six gaps  18 ), etc. The segments of peripheral conductive housing structures  16  that are formed in this way may form parts of antennas in device  10 . 
     If desired, openings in housing  12  such as grooves that extend partway or completely through housing  12  may extend across the width of the rear wall of housing  12  and may penetrate through the rear wall of housing  12  to divide the rear wall into different portions. These grooves may also extend into peripheral conductive housing structures  16  and may form antenna slots, gaps  18 , and other structures in device  10 . Polymer or other dielectric may fill these grooves and other housing openings. In some situations, housing openings that form antenna slots and other structure may be filled with a dielectric such as air. 
     In a typical scenario, device  10  may have one or more upper antennas and one or more lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, near-field communications, etc. 
     A schematic diagram showing illustrative components that may be used in device  10  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  (sometimes referred to herein as control circuitry  28 ) may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, control circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, multiple-input and multiple-output (MIMO) protocols, antenna diversity protocols, near-field communications (NFC) protocols, etc. 
     Input-output circuitry  30  may include input-output devices  32 . Input-output devices  32  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  32  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  32  may include touch screens, displays without touch sensor capabilities, buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, position and orientation sensors (e.g., sensors such as accelerometers, gyroscopes, and compasses), capacitance sensors, proximity sensors (e.g., capacitive proximity sensors, light-based proximity sensors, etc.), fingerprint sensors, etc. 
     Input-output circuitry  30  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  34  may include radio-frequency transceiver circuitry  26  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  24 . Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications or communications in other wireless local area network (WLAN) bands and may handle the 2.4 GHz Bluetooth® communications band or other wireless personal area network (WPAN) bands. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in frequency ranges such as a cellular low band (LB) from 600 to 960 MHz, a cellular low-midband (LMB) from 1410 to 1510 MHz, a cellular midband (MB) from 1710 to 2170 MHz, a cellular high band (FIB) from 2300 to 2700 MHz, a cellular ultra-high band (UHB) from 3400 to 3600 MHz, or other communications bands between 600 MHz and 4000 MHz or other suitable frequencies (as examples). 
     Circuitry  38  may handle voice data and non-voice data. Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include 60 GHz transceiver circuitry (e.g., millimeter wave transceiver circuitry), circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. Wireless communications circuitry  34  may include global positioning system (GPS) receiver equipment such as GPS receiver circuitry  24  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. In Wi-Fi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, dipole antenna structures, monopole antenna structures, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. 
     As shown in  FIG. 3 , transceiver circuitry  26  in wireless communications circuitry  34  may be coupled to antenna structures such as a given antenna  40  using paths such as path  50 . Wireless communications circuitry  34  may be coupled to control circuitry  28 . Control circuitry  28  may be coupled to input-output devices  32 . Input-output devices  32  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures such as antenna  40  with the ability to cover communications frequencies of interest, antenna  40  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). If desired, antenna  40  may be provided with adjustable circuits such as tunable components  42  to tune the antenna over communications bands of interest. Tunable components  42  may be part of a tunable filter or tunable impedance matching network, may be part of an antenna resonating element, may span a gap between an antenna resonating element and antenna ground, etc. 
     Tunable components  42  may include tunable inductors, tunable capacitors, or other tunable components. Tunable components such as these may be based on switches and networks of fixed components, distributed metal structures that produce associated distributed capacitances and inductances, variable solid state devices for producing variable capacitance and inductance values, tunable filters, or other suitable tunable structures. During operation of device  10 , control circuitry  28  may issue control signals on one or more paths such as path  56  that adjust inductance values, capacitance values, or other parameters associated with tunable components  42 , thereby tuning antenna  40  to cover desired communications bands. Antenna tuning components that are used to adjust the frequency response of antenna  40  such as tunable components  42  may sometimes be referred to herein as antenna tuning components, tuning components, antenna tuning elements, tuning elements, adjustable tuning components, adjustable tuning elements, or adjustable components. 
     Path  50  may include one or more transmission lines. As an example, path  50  of  FIG. 3  may be a transmission line having a positive signal conductor such as line  52  and a ground signal conductor such as line  54 . Path  50  may sometimes be referred to herein as transmission line  50  or radio-frequency transmission line  50 . Line  52  may sometimes be referred to herein as positive signal conductor  52 , signal conductor  52 , signal line conductor  52 , signal line  52 , positive signal line  52 , signal path  52 , or positive signal path  52  of transmission line  50 . Line  54  may sometimes be referred to herein as ground signal conductor  54 , ground conductor  54 , ground line conductor  54 , ground line  54 , ground signal line  54 , ground path  54 , or ground signal path  54  of transmission line  50 . 
     Transmission line  50  may, for example, include a coaxial cable transmission line (e.g., ground conductor  54  may be implemented as a grounded conductive braid surrounding signal conductor  52  along its length), a stripline transmission line, a microstrip transmission line, coaxial probes realized by a metalized via, an edge-coupled microstrip transmission line, an edge-coupled stripline transmission line, a waveguide structure (e.g., a coplanar waveguide or grounded coplanar waveguide), combinations of these types of transmission lines and/or other transmission line structures, etc. 
     Transmission lines in device  10  such as transmission line  50  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, transmission lines such as transmission line  50  may also include transmission line conductors (e.g., signal conductors  52  and ground conductors  54 ) integrated within multilayer laminated structures (e.g., layers of a conductive material such as copper and a dielectric material such as a resin that are laminated together without intervening adhesive). The multilayer laminated structures may, if desired, be folded or bent in multiple dimensions (e.g., two or three dimensions) and may maintain a bent or folded shape after bending (e.g., the multilayer laminated structures may be folded into a particular three-dimensional shape to route around other device components and may be rigid enough to hold its shape after folding without being held in place by stiffeners or other structures). All of the multiple layers of the laminated structures may be batch laminated together (e.g., in a single pressing process) without adhesive (e.g., as opposed to performing multiple pressing processes to laminate multiple layers together with adhesive). 
     A matching network (e.g., an adjustable matching network formed using tunable components  42 ) may include components such as inductors, resistors, and capacitors used in matching the impedance of antenna  40  to the impedance of transmission line  50 . Matching network components may be provided as discrete components (e.g., surface mount technology components) or may be formed from housing structures, printed circuit board structures, traces on plastic supports, etc. Components such as these may also be used in forming filter circuitry in antenna(s)  40  and may be tunable and/or fixed components. 
     Transmission line  50  may be coupled to antenna feed structures associated with antenna  40 . As an example, antenna  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed  44  with a positive antenna feed terminal such as terminal  46  and a ground antenna feed terminal such as ground antenna feed terminal  48 . Signal conductor  52  may be coupled to positive antenna feed terminal  46  and ground conductor  54  may be coupled to ground antenna feed terminal  48 . Other types of antenna feed arrangements may be used if desired. For example, antenna  40  may be fed using multiple feeds each coupled to a respective port of transceiver circuitry  26  over a corresponding transmission line. If desired, signal conductor  52  may be coupled to multiple locations on antenna  40  (e.g., antenna  40  may include multiple positive antenna feed terminals coupled to signal conductor  52  of the same transmission line  50 ). Switches may be interposed on the signal conductor between transceiver circuitry  26  and the positive antenna feed terminals if desired (e.g., to selectively activate one or more positive antenna feed terminals at any given time). The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     Control circuitry  28  may use information from a proximity sensor, wireless performance metric data such as received signal strength information, device orientation information from an orientation sensor, device motion data from an accelerometer or other motion detecting sensor, information about a usage scenario of device  10 , information about whether audio is being played through speaker port  8  ( FIG. 1 ), information about whether device  10  is being used to wirelessly communicate using a particular protocol such as a Bluetooth or WLAN protocol, touch and/or force sensor data from a display such as display  14 , image data from an image sensor, infrared image data from an infrared image sensor, ambient light sensor data from an ambient light sensor, radio-frequency range and angle of arrival data, microphone data from one or more microphones or other audio sensors, information on desired frequency bands to use for communications, information from one or more antenna impedance sensors such as impedance sensor  55 , and/or other information in determining when antenna  40  is being affected by the presence of nearby external objects or is otherwise in need of tuning. In response, control circuitry  28  may adjust an adjustable inductor, adjustable capacitor, switch, or other tunable components such as tunable components  42  to ensure that antenna  40  operates as desired. Adjustments to tunable components  42  may also be made to extend the frequency coverage of antenna  40  (e.g., to cover desired communications bands that extend over a range of frequencies larger than antenna  40  would cover without tuning). 
     Impedance sensor  55  may be coupled to control circuitry  28  over path  57 . Impedance sensor  55  may include radio-frequency coupler circuitry (e.g., one or more radio-frequency couplers) coupled to transmission line  50  and/or portions of antenna  40 . Impedance sensor  55  may gather radio-frequency signals (e.g., transmitted and reflected radio-frequency signals or other signals) and may generate corresponding impedance data (e.g., radio-frequency phase and magnitude data) indicative of the impedance of antenna  40 . Control circuitry  28  may gather impedance data about the impedance of antenna  40  using impedance sensor  55  over path  57 . The impedance data may be used in adjusting wireless communications circuitry  34  if desired. 
     Antenna  40  may include resonating element structures (sometimes referred to herein as radiating element structures), antenna ground plane structures (sometimes referred to herein as ground plane structures, ground structures, or antenna ground structures), an antenna feed such as feed  44 , and other components (e.g., tunable components  42 ). Antenna  40  may be configured to form any suitable types of antenna. With one suitable arrangement, which is sometimes described herein as an example, antenna  40  is used to implement a hybrid inverted-F-slot antenna that includes both inverted-F and slot antenna resonating elements. 
     If desired, multiple antennas  40  may be formed in device  10 . Each antenna  40  may be coupled to transceiver circuitry such as transceiver circuitry  26  over respective transmission lines such as transmission line  50 . If desired, two or more antennas  40  may share the same transmission line  50 .  FIG. 4  is a diagram showing how device  10  may include multiple antennas  40  for performing wireless communications. 
     As shown in  FIG. 4 , device  10  may include two or more antennas  40  such as a first antenna  40 - 1 , a second antenna  40 - 2 , a third antenna  40 - 3 , and a fourth antenna  40 - 4 . Antennas  40  may be provided at different locations within housing  12  of device  10 . For example, antennas  40 - 1  and  40 - 2  may be formed within region  22  at a first (upper) end of housing  12  whereas antennas  40 - 3  and  40 - 4  are formed within region  20  at an opposing second (lower) end of housing  12 . In the example of  FIG. 3 , housing  12  has a rectangular periphery (e.g., a periphery having four corners) and each antenna  40  is formed at a respective corner of housing  12 . This example is merely illustrative and, in general, antennas  40  may be formed at any desired locations within housing  12 . 
     Wireless communications circuitry  34  may include input-output ports such as port  60  for interfacing with digital data circuits in control circuitry (e.g., storage and processing circuitry  28  of  FIG. 2 ). Wireless communications circuitry  34  may include baseband circuitry such as baseband (BB) processor  62  and radio-frequency transceiver circuitry such as transceiver circuitry  26 . 
     Port  60  may receive digital data from control circuitry that is to be transmitted by transceiver circuitry  26 . Incoming data that has been received by transceiver circuitry  26  and baseband processor  62  may be supplied to control circuitry via port  60 . 
     Transceiver circuitry  26  may include one or more transmitters and one or more receivers. For example, transceiver circuitry  26  may include multiple remote wireless transceivers  38  such as a first transceiver  38 - 1 , a second transceiver  38 - 2 , a third transceiver  38 - 3 , and a fourth transceiver  38 - 4  (e.g., transceiver circuits for handling voice and non-voice cellular telephone communications in cellular telephone communications bands). Each transceiver  38  may be coupled to a respective antenna  40  over a corresponding transmission line  50  (e.g., a first transmission line  50 - 1 , a second transmission line  50 - 2 , a third transmission line  50 - 3 , and a fourth transmission line  50 - 4 ). For example, first transceiver  38 - 1  may be coupled to antenna  40 - 1  over transmission line  50 - 1 , second transceiver  38 - 2  may be coupled to antenna  40 - 2  over transmission line  50 - 2 , third transceiver  38 - 3  may be coupled to antenna  40 - 3  over transmission line  50 - 3 , and fourth transceiver  38 - 4  may be coupled to antenna  40 - 4  over transmission line  50 - 4 . 
     Radio-frequency front end circuits  58  may be interposed on each transmission line  50  (e.g., a first front end circuit  58 - 1  may be interposed on transmission line  50 - 1 , a second front end circuit  58 - 2  may be interposed on transmission line  50 - 2 , a third front end circuit  58 - 3  may be interposed on transmission line  50 - 3 , etc.). Front end circuits  58  may each include switching circuitry, filter circuitry (e.g., duplexer and/or diplexer circuitry, notch filter circuitry, low pass filter circuitry, high pass filter circuitry, bandpass filter circuitry, etc.), impedance matching circuitry for matching the impedance of transmission lines  50  to the corresponding antenna  40 , networks of active and/or passive components such as tunable components  42  of  FIG. 3 , radio-frequency coupler circuitry for gathering antenna impedance measurements, amplifier circuitry (e.g., low noise amplifiers and/or power amplifiers) or any other desired radio-frequency circuitry. If desired, front end circuits  58  may include switching circuitry that is configured to selectively couple antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  to different respective transceivers  38 - 1 ,  38 - 2 ,  38 - 3 , and  38 - 4  (e.g., so that each antenna can handle communications for different transceivers  38  over time based on the state of the switching circuits in front end circuits  58 ). 
     If desired, front end circuits  58  may include filtering circuitry (e.g., duplexers and/or diplexers) that allow the corresponding antenna  40  to transmit and receive radio-frequency signals at the same time (e.g., using a frequency domain duplexing (FDD) scheme). Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may transmit and/or receive radio-frequency signals in respective time slots or two or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may transmit and/or receive radio-frequency signals concurrently. In general, any desired combination of transceivers  38 - 1 ,  38 - 2 ,  38 - 3 , and  38 - 4  may transmit and/or receive radio-frequency signals using the corresponding antenna  40  at a given time. In one suitable arrangement, each of transceivers  38 - 1 ,  38 - 2 ,  38 - 3 , and  38 - 4  may receive radio-frequency signals while a given one of transceivers  38 - 1 ,  38 - 2 ,  38 - 3 , and  38 - 4  transmits radio-frequency signals at a given time. 
     Amplifier circuitry such as one or more power amplifiers may be interposed on transmission lines  50  and/or formed within transceiver circuitry  26  for amplifying radio-frequency signals output by transceivers  38  prior to transmission over antennas  40 . Amplifier circuitry such as one or more low noise amplifiers may be interposed on transmission lines  50  and/or formed within transceiver circuitry  26  for amplifying radio-frequency signals received by antennas  40  prior to conveying the received signals to transceivers  38 . 
     In the example of  FIG. 4 , separate front end circuits  58  are formed on each transmission line  50 . This is merely illustrative. If desired, two or more transmission lines  50  may share the same front end circuits  58  (e.g., front end circuits  58  may be formed on the same substrate, module, or integrated circuit). 
     Each of transceivers  38  may, for example, include circuitry for converting baseband signals received from baseband processor  62  over paths  63  into corresponding radio-frequency signals. For example, transceivers  38  may each include mixer circuitry for up-converting the baseband signals to radio-frequencies prior to transmission over antennas  40 . Transceivers  38  may include digital to analog converter (DAC) and/or analog to digital converter (ADC) circuitry for converting signals between digital and analog domains. Each of transceivers  38  may include circuitry for converting radio-frequency signals received from antennas  40  over transmission lines  50  into corresponding baseband signals. For example, transceivers  38  may each include mixer circuitry for down-converting the radio-frequency signals to baseband frequencies prior to conveying the baseband signals to baseband processor  62  over paths  63 . 
     Each transceiver  38  may be formed on the same substrate, integrated circuit, or module (e.g., transceiver circuitry  26  may be a transceiver module having a substrate or integrated circuit on which each of transceivers  38  are formed) or two or more transceivers  38  may be formed on separate substrates, integrated circuits, or modules. Baseband processor  62  and front end circuits  58  may be formed on the same substrate, integrated circuit, or module as transceivers  38  or may be formed on separate substrates, integrated circuits, or modules from transceivers  38 . In another suitable arrangement, transceiver circuitry  26  may include a single transceiver  38  having four ports, each of which is coupled to a respective transmission line  50 , if desired. Each transceiver  38  may include transmitter and receiver circuitry for both transmitting and receiving radio-frequency signals. In another suitable arrangement, one or more transceivers  38  may perform only signal transmission or signal reception (e.g., one or more of circuits  38  may be a dedicated transmitter or dedicated receiver). 
     In the example of  FIG. 4 , antennas  40 - 1  and  40 - 4  may occupy a larger space (e.g., a larger area or volume within device  10 ) than antennas  40 - 2  and  40 - 3 . This may allow antennas  40 - 1  and  40 - 4  to support communications at longer wavelengths (i.e., lower frequencies) than antennas  40 - 2  and  40 - 3 . This is merely illustrative and, if desired, each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may occupy the same volume or may occupy different volumes. Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may be configured to convey radio-frequency signals in at least one common frequency band. If desired, one or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may handle radio-frequency signals in at least one frequency band that is not covered by one or more of the other antennas in device  10 . 
     If desired, each antenna  40  and each transceiver  38  may handle radio-frequency communications in multiple frequency bands (e.g., multiple cellular telephone communications bands). For example, transceiver  38 - 1 , antenna  40 - 1 , transceiver  38 - 4 , and antenna  40 - 4 , may handle radio-frequency signals in a first frequency band such as a cellular low band between 600 and 960 MHz, a second frequency band such as a cellular low-midband between 1410 and 1510 MHz, a third frequency band such as a cellular midband between 1700 and 2200 MHz, a fourth frequency band such as a cellular high band between 2300 and 2700 MHz, and/or a fifth frequency band such as a cellular ultra-high band between 3400 and 3600 MHz. Transceiver  38 - 2 , antenna  40 - 2 , transceiver  38 - 3 , and antenna  40 - 3  may handle radio-frequency signals in some or all of these bands (e.g., in scenarios where the volume of antennas  40 - 3  and  40 - 2  is large enough to support frequencies in the low band). 
     The example of  FIG. 4  is merely illustrative. In general, antennas  40  may cover any desired frequency bands. Transceiver circuitry  26  may include other transceiver circuits such as one or more circuits  36  or  24  of  FIG. 2  coupled to one or more antennas  40 . Housing  12  may have any desired shape. Antennas  40  may be formed at any desired locations within housing  12 . Forming each of antennas  40 - 1  through  40 - 4  at different corners of housing  12  may, for example, maximize the multi-path propagation of wireless data conveyed by antennas  40  to optimize overall data throughput for wireless communications circuitry  34 . 
     When operating using a single antenna  40 , a single stream of wireless data may be conveyed between device  10  and external communications equipment (e.g., one or more other wireless devices such as wireless base stations, access points, cellular telephones, computers, etc.). This may impose an upper limit on the data rate (data throughput) obtainable by wireless communications circuitry  34  in communicating with the external communications equipment. As software applications and other device operations increase in complexity over time, the amount of data that needs to be conveyed between device  10  and the external communications equipment typically increases, such that a single antenna  40  may not be capable of providing sufficient data throughput for handling the desired device operations. 
     In order to increase the overall data throughput of wireless communications circuitry  34 , multiple antennas  40  may be operated using a multiple-input and multiple-output (MIMO) scheme. When operating using a MIMO scheme, two or more antennas  40  on device  10  may be used to convey multiple independent streams of wireless data at the same frequency. This may significantly increase the overall data throughput between device  10  and the external communications equipment relative to scenarios where only a single antenna  40  is used. In general, the greater the number of antennas  40  that are used for conveying wireless data under the MIMO scheme, the greater the overall throughput of wireless communications circuitry  34 . 
     In order to perform wireless communications under a MIMO scheme, antennas  40  need to convey data at the same frequencies. If desired, wireless communications circuitry  34  may perform so-called two-stream (2×) MIMO operations (sometimes referred to herein as 2× MIMO communications or communications using a 2× MIMO scheme) in which two antennas  40  are used to convey two independent streams of radio-frequency signals at the same frequency. Wireless communications circuitry  34  may perform so-called four-stream (4×) MIMO operations (sometimes referred to herein as 4× MIMO communications or communications using a 4× MIMO scheme) in which four antennas  40  are used to convey four independent streams of radio-frequency signals at the same frequency. Performing 4× MIMO operations may support higher overall data throughput than 2× MIMO operations because 4× MIMO operations involve four independent wireless data streams whereas 2× MIMO operations involve only two independent wireless data streams. If desired, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 2× MIMO operations in some frequency bands and may perform 4× MIMO operations in other frequency bands (e.g., depending on which bands are handled by which antennas). Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 2× MIMO operations in some bands concurrently with performing 4× MIMO operations in other bands, for example. 
     As one example, antennas  40 - 1  and  40 - 4  (and the corresponding transceivers  38 - 1  and  38 - 4 ) may perform 2× MIMO operations by conveying radio-frequency signals at the same frequency in a cellular low band between 600 MHz and 960 MHz. At the same time, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may collectively perform 4× MIMO operations by conveying radio-frequency signals at the same frequency in a cellular midband between 1700 and 2200 MHz and/or at the same frequency in a cellular high band (HB) between 2300 and 2700 MHz (e.g., antennas  40 - 1  and  40 - 4  may perform 2× MIMO operations in the low band concurrently with performing 4× MIMO operations in the midband and/or high band). This example is merely illustrative and, in general, any desired number of antennas may be used to perform any desired MIMO operations in any desired frequency bands. 
     If desired, antennas  40 - 1  and  40 - 2  may include switching circuitry that is adjusted by control circuitry (e.g., control circuitry  28  of  FIG. 3 ). Control circuitry  28  may control the switching circuitry in antennas  40 - 1  and  40 - 2  to configure antenna structures in antennas  40 - 1  and  40 - 2  to form a single antenna  40 U in region  22  of device  10 . Similarly, antennas  40 - 3  and  40 - 4  may include switching circuitry that is adjusted by control circuitry  28 . Control circuitry  28  may control the switching circuitry in antennas  40 - 3  and  40 - 4  to form a single antenna  40 L (e.g., an antenna  40 L that includes antenna structures from antennas  40 - 3  and  40 - 4 ) in region  20  of device  10 . Antenna  40 U may, for example, be formed at an upper end of housing  12  and may therefore sometimes be referred to herein as upper antenna  40 U. Antenna  40 L may be formed at an opposing lower end of housing  12  and may therefore sometimes be referred to herein as lower antenna  40 L. When antennas  40 - 1  and  40 - 2  are configured to form upper antenna  40 U and antennas  40 - 3  and  40 - 4  are configured to form lower antenna  40 L, wireless communications circuitry  34  may perform 2× MIMO operations using antennas  40 U and  40 L in any desired frequency bands. If desired, control circuitry  28  may toggle the switching circuitry over time to switch wireless communications circuitry  34  between a first mode in which antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  perform 2× MIMO operations in any desired frequency bands and 4× MIMO operations in any desired frequency bands and a second mode in which antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  are configured to form antennas  40 U and  40 L that perform 2× MIMO operations in any desired frequency bands. 
     If desired, wireless communications circuitry  34  may convey wireless data with multiple antennas on one or more external devices (e.g., multiple wireless base stations) in a scheme sometimes referred to as carrier aggregation. When operating using a carrier aggregation scheme, the same antenna  40  may convey radio-frequency signals with multiple antennas (e.g., antennas on different wireless base stations) at different respective frequencies (sometimes referred to herein as carrier frequencies, channels, carrier channels, or carriers). For example, antenna  40 - 1  may receive radio-frequency signals from a first wireless base station at a first frequency, from a second wireless base station at a second frequency, and a from a third base station at a third frequency. The received signals at different frequencies may be simultaneously processed (e.g., by transceiver  38 - 1 ) to increase the communications bandwidth of transceiver  38 - 1 , thereby increasing the data rate of transceiver  38 - 1 . Similarly, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform carrier aggregation at two, three, or more than three frequencies within any desired frequency bands. This may serve to further increase the overall data throughput of wireless communications circuitry  34  relative to scenarios where no carrier aggregation is performed. For example, the data throughput of circuitry  34  may increase for each carrier frequency that is used (e.g., for each wireless base station that communicates with each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 ). 
     By performing communications using both a MIMO scheme and a carrier aggregation scheme, the data throughput of wireless communications circuitry  34  may be even greater than in scenarios where either a MIMO scheme or a carrier aggregation scheme is used. The data throughput of circuitry  34  may, for example, increase for each carrier frequency that is used by antennas  40  (e.g., each carrier frequency may contribute 40 megabits per second (Mb/s) or some other throughput to the total throughput of wireless communications circuitry  34 ). As one example, antennas  40 - 1  and  40 - 4  may perform carrier aggregation across three frequencies within each of the cellular low band, midband, and high band and antennas  40 - 3  and  40 - 4  may perform carrier aggregation across three frequencies within each of the cellular midband and high band. At the same time, antennas  40 - 1  and  40 - 4  may perform 2× MIMO operations in the cellular low band and antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may perform 4× MIMO operations in one of cellular midband and the cellular high band. In this scenario, with an exemplary throughput of 40 Mb/s per carrier frequency, wireless communications circuitry  34  may exhibit a throughput of approximately 960 Mb/s. If 4× MIMO operations are performed in both the cellular midband and the cellular high band by antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 , wireless communications circuitry  34  may exhibit an even greater throughput of approximately 1200 Mb/s. In other words, the data throughput of wireless communications circuitry  34  may be increased from the 40 Mb/s associated with conveying signals at a single frequency with a single antenna to approximately 1 gigabits per second (Gb/s) by performing communications using MIMO and carrier aggregation schemes using four antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 . 
     These examples are merely illustrative and, if desired, carrier aggregation may be performed in fewer than three carriers per band, may be performed across different bands, or may be omitted for one or more of antennas  40 - 1  through  40 - 4 . The example of  FIG. 4  is merely illustrative. If desired, antennas  40  may cover any desired number of frequency bands at any desired frequencies. More than four antennas  40  or fewer than four antennas  40  may perform MIMO and/or carrier aggregation operations at non-near-field communications frequencies if desired. 
     Antennas  40  may include slot antenna structures, inverted-F antenna structures (e.g., planar and non-planar inverted-F antenna structures), loop antenna structures, combinations of these, or other antenna structures. An illustrative inverted-F antenna structure is shown in  FIG. 5 . 
     When using an inverted-F antenna structure as shown in  FIG. 5 , antenna  40  may include an antenna resonating element  64  (sometimes referred to herein as antenna radiating element  64 ) and antenna ground  74  (sometimes referred to herein as ground plane  74  or ground  74 ). Antenna resonating element  64  may have a main resonating element arm such as resonating element arm  66 . The length of resonating element arm  66  may be selected so that antenna  40  resonates at desired operating frequencies. For example, the length of resonating element arm  66  (or a branch of resonating element arm  66 ) may be approximately one-quarter of the wavelength corresponding to a desired operating frequency for antenna  40 . Antenna  40  may also exhibit resonances at harmonic frequencies. If desired, slot antenna structures or other antenna structures may be incorporated into an inverted-F antenna such as antenna  40  of  FIG. 5  (e.g., to enhance antenna response in one or more communications bands). 
     Resonating element arm  66  may be coupled to antenna ground  74  by return path  68 . Antenna feed  44  may include positive antenna feed terminal  46  and ground antenna feed terminal  48  and may run parallel to return path  68  between resonating element arm  66  and antenna ground  74 . If desired, antenna  40  may have more than one resonating element arm branch (e.g., to create multiple frequency resonances to support operations in multiple communications bands) or may have other antenna structures (e.g., parasitic antenna resonating elements, tunable components to support antenna tuning, etc.). For example, resonating element arm  66  may have left and right branches that extend outwardly from antenna feed  44  and return path  68 . If desired, multiple feeds may be used to feed antennas such as antenna  40 . Resonating element arm  66  may follow any desired path having any desired shape (e.g., curved and/or straight paths, meandering paths, etc.). 
     If desired, antenna  40  may include one or more adjustable circuits (e.g., tunable components  42  of  FIG. 3 ) that are coupled to resonating element arm  66 . As shown in  FIG. 5 , for example, tunable components such as adjustable inductor  70  may be coupled between antenna resonating element structures in antenna  40  such as resonating element arm  66  and antenna ground  74  (i.e., adjustable inductor  70  may bridge the gap between resonating element arm  66  and antenna ground  74 ). Adjustable inductor  70  may exhibit an inductance value that is adjusted in response to control signals  72  provided to adjustable inductor  70  from control circuitry  28  ( FIG. 3 ). 
     Antenna  40  may be a hybrid antenna that includes one or more slot elements. As shown in  FIG. 6 , for example, antenna  40  may be based on a slot antenna configuration having an opening such as slot  76  that is formed within conductive structures such as antenna ground  74 . Slot  76  may be filled with air, plastic, and/or other dielectric. The shape of slot  76  may be straight or may have one or more bends (i.e., slot  76  may have an elongated shape following a meandering path). Feed terminals  48  and  46  may, for example, be located on opposing sides of slot  76  (e.g., on opposing long sides). Slot  76  may sometimes be referred to herein as slot element  76 , slot antenna resonating element  76 , slot antenna radiating element  76 , or slot radiating element  76 . Slot-based radiating elements such as slot  76  of  FIG. 6  may give rise to an antenna resonance at frequencies in which the wavelength of the antenna signals is approximately equal to the perimeter of the slot. In narrow slots, the resonant frequency of slot  76  is associated with signal frequencies at which the slot length is approximately equal to a half of a wavelength of operation. 
     The frequency response of antenna  40  can be tuned using one or more tuning components (e.g., tunable components  42  of  FIG. 3 ). These components may have terminals that are coupled to opposing sides of slot  76  (i.e., the tunable components may bridge slot  76 ). If desired, tunable components may have terminals that are coupled to respective locations along the length of one of the sides of slot  76 . Combinations of these arrangements may also be used. If desired, antenna  40  may be a hybrid slot-inverted-F antenna that includes resonating elements of the type shown in both  FIG. 5  and  FIG. 6  (e.g., having resonances given by both a resonating element arm such as resonating element arm  66  of  FIG. 5  and a slot such as slot  76  of  FIG. 6 ). 
     The example of  FIG. 6  is merely illustrative. In general, slot  76  may have any desired shape (e.g., shapes with straight and/or curved edges), may follow a meandering path, etc. If desired, slot  76  may be an open slot having one or more ends that are free from conductive material (e.g., where slot  76  extends through one or more sides of antenna ground  74 ). Slot  76  may, for example, have a length approximately equal to one-quarter of the wavelength of operation in these scenarios. 
     If desired, each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  ( FIG. 4 ) may be formed using hybrid slot-inverted-F antenna structures that includes resonating elements of the types shown in  FIGS. 5 and 6 . Each of these antennas may be formed using a portion of the housing for electronic device  10 . A top interior view of device  10  showing how antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may be integrated within the housing for electronic device  10  is shown in  FIG. 7 . 
     As shown in  FIG. 7 , peripheral conductive housing structures  16  may be segmented (divided) by dielectric-filled gaps  18  (e.g., plastic gaps) that divide peripheral conductive housing structures  16  into segments. Gaps  18  may include a first gap  18 - 1 , a second gap  18 - 2 , a third gap  18 - 3 , a fourth gap  18 - 4 , a fifth gap  18 - 5 , and a sixth gap  18 - 6 . Gaps  18 - 6  and  18 - 1  may be formed on the left side of device  10 , gaps  18 - 4  and  18 - 2  may be formed on the right side of device  10 , gap  18 - 3  may be formed on the bottom side of device  10 , and gap  18 - 5  may be formed on the top side of device  10 . Gap  18 - 6  may separate a first segment  16 - 1  of peripheral conductive housing structures  16  from a sixth segment  16 - 6  of peripheral conductive housing structures. Gap  18 - 5  may separate sixth segment  16 - 6  from a fifth segment  16 - 5  of peripheral conductive housing structures  16 . Gap  18 - 4  may separate fifth segment  16 - 5  from a fourth segment  16 - 4  of peripheral conductive housing structures  16 . Gap  18 - 2  may separate fourth segment  16 - 4  of peripheral conductive housing structures  16  from a third segment  16 - 3  of peripheral conductive housing structures  16 . Gap  18 - 3  may separate third segment  16 - 3  from second segment  16 - 2  of peripheral conductive housing structures  16 . Gap  18 - 1  may separate second segment  16 - 2  from first segment  16 - 1  of peripheral conductive housing structures  16 . 
     The resonating element for antenna  40 - 4  may include an inverted-F antenna resonating element arm (e.g., resonating element arm  66  of  FIG. 5 ) that is formed from segment  16 - 3 . The resonating element for antenna  40 - 3  may include an inverted-F antenna resonating element arm that is formed from segment  16 - 2 . Similarly, the resonating element for antenna  40 - 2  may include an inverted-F antenna resonating element arm that is formed from segment  16 - 5  and the resonating element for antenna  40 - 1  may include an inverted-F antenna resonating element arm that is formed from segment  16 - 6 . Segments  16 - 6  and  16 - 5  may be separated from ground structures  78  by slot  76 U (e.g., a radiating slot  76  as shown in  FIG. 6 ). Segments  16 - 2  and  16 - 3  may be separated from ground structures  78  by slot  76 L (e.g., a radiating slot  76  as shown in  FIG. 6 ). Air and/or other dielectric may fill slots  76 U and  76 L. 
     Each antenna may include one or more antenna feeds (e.g., antenna feed  44  of  FIGS. 3, 5, and 6 ) coupled across the corresponding slot. In the example of  FIG. 7 , lower antenna  40 - 4  includes two antenna feeds coupled across slot  76 L (e.g., a first antenna feed having a positive antenna feed terminal  46 A coupled to segment  16 - 3  and a ground antenna feed terminal  48 A coupled to ground structures  78 , as well as a second antenna feed having a positive antenna feed terminal  46 B coupled to segment  16 - 3  and a ground antenna feed terminal  48 B coupled to ground structures  78 ). This example is merely illustrative. Antenna  40 - 4  may have only one antenna feed or more than three antenna feeds if desired. While antennas  40 - 1 ,  40 - 2 , and  40 - 3  are shown in the example of  FIG. 7  without antenna feeds for the sake of clarity, antennas  40 - 1 ,  40 - 2 , and  40 - 3  may each have any desired number of antenna feeds (e.g., one antenna feed, two antenna feeds, or more than two antenna feeds). Each antenna feed may be selectively activated at a given time (e.g., using switching circuitry and/or by selectively activating different ports of transceiver circuitry  26  of  FIG. 3 ). 
     Ground structures  78  may include one or more planar metal layers such as a metal layer used to form a rear housing wall for device  10 , a metal layer that forms an internal support structure for device  10 , conductive traces on a printed circuit board, and/or any other desired conductive layers in device  10 . Ground structures  78  may extend from segment  16 - 1  to segment  16 - 4  of peripheral conductive housing structures  16 . Ground structures  78  may be coupled to segments  16 - 1  and  16 - 4  using conductive adhesive, solder, welds, conductive screws, conductive pins, and/or any other desired conductive interconnect structures. If desired, ground structures  78  and segments  16 - 1  and  16 - 4  may be formed from different portions of a single integral conductive structure (e.g., a conductive housing for device  10 ). 
     Ground structures  78  need not be confined to a single plane and may, if desired, include multiple layers located in different planes or non-planar structures. Ground structures  78  may include conductive (e.g., grounded) portions of other electrical components within device  10 . For example, ground structures  78  may include conductive portions of display  14  ( FIG. 1 ). Conductive portions of display  14  may include a metal frame for display  14 , a metal backplate for display  14 , shielding layers or shielding cans for display  14 , pixel circuitry in display  14 , touch sensor circuitry (e.g., touch sensor electrodes) for display  14 , and/or any other desired conductive structures in display  14  or used for mounting display  14  to the housing for device  10 . 
     Ground structures  78  and segments  16 - 1  and  16 - 4  may form portions of antenna ground  74  ( FIGS. 5 and 6 ) for antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 . If desired, slot  76 L may be configured to form slot antenna resonating element structures that contribute to the overall performance of antennas  40 - 3  and/or  40 - 4 . Slot  76 L may extend from gap  18 - 1  to gap  18 - 2  (e.g., the ends of slot  76 L which may sometimes be referred to as open ends, may be formed by gaps  18 - 1  and  18 - 2 ). Slot  76 L 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 the longitudinal axis of the longest a portion of slot  76 L (e.g., the portion of slot  76  extending from the left to the right of  FIG. 7 ). If desired, slot  76 L may include vertical portions that extend parallel to longitudinal axis  80  of device  10  and beyond gaps  18 - 1  and  18 - 2 . 
     Similarly, slot  76 U may be configured to form slot antenna resonating element structures that contribute to the overall performance of antennas  40 - 1  and/or  40 - 2 . Slot  76 U may extend from gap  18 - 6  to gap  18 - 4  (e.g., the ends of slot  76 U may be formed by gaps  18 - 6  and  18 - 4 ). Slot  76 U 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 - 5  may be continuous with and extend perpendicular to the longitudinal axis of the longest a portion of slot  76 U. If desired, slot  76 U may include vertical portions that extend parallel to longitudinal axis  80  of device  10  and beyond gaps  18 - 6  and  18 - 4  (e.g., towards slot  76 L). 
     Slots  76 U and  76 L may be filled with dielectric such as air, plastic, ceramic, or glass. For example, plastic may be inserted into portions of slots  76 U and  76 L and this plastic may be flush with the exterior of the housing for device  10 . Dielectric material in slot  76 U may lie flush with dielectric material in gaps  18 - 6 ,  18 - 5 , and  18 - 4  at the exterior of the housing  12  if desired. Dielectric material in slot  76 L may lie flush with dielectric material in gaps  18 - 1 ,  18 - 3 , and  18 - 2  at the exterior of the housing  12 . The example of  FIG. 7  in which slots  76 L and  76 U each have a U-shape is merely illustrative. If desired, slots  76 U and  76 L may have any other desired shapes (e.g., rectangular shapes, meandering shapes having curved and/or straight edges, etc.). 
     The presence or absence of external objects such as a user&#39;s hand or other body part in the vicinity of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may affect antenna loading and therefore antenna performance. For example, in free space (e.g., the absence of external loading from external objects), each antenna may operate with satisfactory antenna efficiency. However, if care is not taken in the presence of external loading, one or more antennas may become detuned by the external loading, thereby leading to a degradation in antenna efficiency in one or more frequency bands for those antennas. 
     Antenna loading may differ depending on the way in which device  10  is being held. For example, antenna loading and therefore antenna performance may be affected in one way when a user is holding device  10  in the user&#39;s right hand, may be affected in another way when a user is holding device  10  in the user&#39;s left hand, and may be affected in another way when a user is holding device  10  with both hands. Because device  10  includes antennas at both lower region  20  and upper region  22  that may operate at the same frequencies under a MIMO scheme, antenna loading and therefore antenna performance may also be affected in one way when a user is holding device  10  in a portrait orientation (e.g., with region  22  pointed upwards, skywards, or away from the user&#39;s body) and may be affected in another way when a user is holding device  10  a landscape orientation (e.g., with segment  16 - 1  or  16 - 4  pointed upwards, skywards, or away from the user&#39;s body). 
     Other factors and combinations of these factors may also affect antenna loading and performance. In general, factors such as the hand (or hands) that a user uses to hold device  10 , the orientation of device  10 , how far away the user holds device  10  from their body, where the user holds device  10  during use, the type of material located adjacent to device  10 , and/or other factors may affect antenna loading and therefore antenna performance for one or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 . In addition, regulatory and/or industry standards may impose limits on the amount of radio-frequency energy that can be transmitted by antennas in the vicinity of different parts of the user&#39;s body (e.g., limits on the amount of radio-frequency energy absorbed by the user&#39;s body). 
     To accommodate various loading scenarios and such limits on absorbed radio-frequency energy, device  10  may use sensor data and other information about how device  10  is being used to detect and/or predict the presence of antenna loading adjacent to one or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 . Device  10  (e.g., control circuitry  28  of  FIG. 3 ) may then adjust antenna settings for wireless communications circuitry  34  to ensure that satisfactory antenna performance is achieved by wireless communications circuitry  34  while also satisfying any regulatory or industry-imposed limits on radio-frequency absorption. Control circuitry  28  may adjust the antenna settings by, for example, selectively activating one or more antennas  40 , selectively activating one or more antenna feeds (e.g., positive antenna feed terminals such as positive antenna feed terminals  46 A and  46 B of  FIG. 7 ), limiting the maximum transmit power level of the antennas, selecting desired operating frequencies, and/or adjusting tunable components of in the antennas (e.g., tunable components  42  of  FIG. 3 ). 
     As shown in  FIG. 7 , segment  16 - 4  is associated with the right edge of housing  12  when device  10  is viewed from the front and segment  16 - 1  is associated with the left edge of housing  12  when device  10  is viewed from the front. When a user is holding device  10  in the user&#39;s right hand, the palm of the user&#39;s right hand may rest along the bottom-right edge of housing  12  such as within region  84  and the fingers of the user&#39;s right hand (which do not load the antennas as much as the user&#39;s palm) will rest along segment  16 - 1  of housing  12 . In this situation, loading from the user&#39;s palm may deteriorate the antenna efficiency of antenna  40 - 4  in one or more frequency bands and/or may undesirably affect the performance of the other antennas in device  10 . Similarly, when a user is holding device  10  in the user&#39;s left hand, the palm of the user&#39;s left hand may rest along the bottom-left edge of device  10  such as within region  82  and the fingers of the user&#39;s left hand will rest along segment  16 - 4  of device  10 . In this scenario, the palm of the user&#39;s hand may load and deteriorate the antenna efficiency of antenna  40 - 3  in one or more frequency bands and/or may undesirably affect the performance of the other antennas in device  10 . 
     These examples are merely illustrative of some of the possible usage scenarios for device  10 . In other usage scenarios, the user may hold device  10  with both hands in a portrait orientation (e.g., where the user&#39;s palms are located in regions  82  and  84 ), with both hands in a landscape orientation (e.g., where the user&#39;s palms are located in regions  86  and  84  or in regions  88  and  82 ), with one hand in a landscape orientation, or in other manners. When a user holds device  10  to their ear, the user&#39;s ear, head, or other parts of the user&#39;s body may load one or more antennas in device  10  (e.g., from region  88  and/or region  86 ). These environmental factors affecting the loading of antennas  40  in device  10  (e.g., from external objects at or adjacent to the exterior of device  10 ) may sometimes be referred to herein as the operating environment for device  10 . 
     Control circuitry  28  ( FIG. 3 ) may monitor the operating environment for device  10  during use. Control circuitry  28  may control the antenna settings for wireless communications circuitry  34  based on the monitored operating environment to ensure that one or more antennas (e.g., at least two antennas for performing MIMO operations) operate with satisfactory antenna efficiency in one or more frequency bands of interest. At the same time, control circuitry  28  may also adjust the antenna settings for wireless communications circuitry  34  to ensure that device  10  satisfies any applicable limits on absorbed radio-frequency energy regardless of operating environment. 
       FIG. 8  is a flow chart of illustrative steps involved in operating wireless communications circuitry  34  to ensure that antennas  40  exhibit satisfactory performance (e.g., antenna efficiency) while also meeting limits on absorbed radio-frequency energy regardless of operating environment. 
     At step  90 , control circuitry  28  may monitor the operating environment of device  10 . Control circuitry  28  may monitor the operating environment by gathering sensor data using sensors on device  10  (e.g., sensors from input-output devices  32  of  FIG. 2 ). For example, at step  92 , control circuitry  28  may gather antenna impedance measurements for antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and/or  40 - 4  using impedance sensors such as impedance sensor  55  of  FIG. 3 . The impedance measurements may include radio-frequency phase and magnitude data (e.g., radio-frequency phase and magnitude data associated with transmitted, received, and/or reflected radio-frequency signals) and may sometimes referred to herein as impedance data, impedance values, or impedance information. 
     The impedance measurements may, for example, be indicative of external objects located in the vicinity of antenna  40 - 1 ,  40 - 2 ,  40 - 3 , and/or  40 - 4 . Control circuitry  28  may process the impedance measurements to identify how device  10  is being used or held by a user (e.g., to help identify the operating environment for device  10 ). For example, if control circuitry  28  detects that only antennas  40 - 4  and  40 - 2  ( FIG. 7 ) are being heavily loaded based on the impedance measurements, control circuitry  28  may determine that device  10  is being held in a landscape orientation with both of the user&#39;s hands (e.g., hands within regions  84  and  86  of  FIG. 7 ). As another example, if control circuitry  28  detects that only antenna  40 - 3  is being heavily loaded using the impedance measurements, control circuitry  28  may determine that device  10  is being held in a portrait orientation with the user&#39;s left hand. These examples are merely illustrative and, in general, the impedance measurement is indicative of any loading of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 . 
     Control circuitry  28  may gather image data (e.g., one or more images that includes an array of pixel values or other image signals) using one or more image sensors on device  10  (step  100 ). The image sensors may include visible light image sensors that capture visible light image data using visible light-sensitive image sensor pixels, infrared light image sensors that capture infrared image data using infrared light-sensitive image sensor pixels, image sensors that capture image data in response to both visible and infrared light, or other suitable image sensors. The image sensors may be integrated into one or more camera modules (e.g., cameras) mounted within housing  12 . The image sensors may include first and second image sensors (so-called front-facing image sensors or front-facing cameras) mounted at the front face of device  10  (e.g., within inactive region IA of display  14  of  FIG. 1 ) and third and fourth image sensors mounted at the rear face of device  10  (a so-called rear-facing image sensors or rear-facing cameras). This example is merely illustrative and device  10  may, in general, include any desired number of image sensors. 
     In one suitable arrangement, input-output devices  32  ( FIG. 2 ) may include light sources mounted to the front face of device  10  (e.g., within inactive region IA of display  14  of  FIG. 1 ). The light sources may emit light at infrared wavelengths or other wavelengths that is reflected off of objects (e.g., the face of a user) and back towards device  10 . The light sources may, for example, include a flood illuminator and a dot projector. The dot projector may, for example, emit a grid, array, matrix, or other pattern of light dots (e.g., dots of light at infrared wavelengths) that are reflected off of objects facing display  14 . One or more of the front-facing image sensors may generate image data in response to this reflected light. Control circuitry  28  may process this image data (sometimes referred to herein as face image data, front-facing image data, or facial recognition image data) to identify facial features of the user (or other persons or objects that reflected the emitted light towards device  10 ). The facial recognition image data may include a depth map that maps three-dimensional depth of the scene in front of display  14  (e.g., that maps a distance between objects in the scene in front of display  14  and display  14 ). Control circuitry  28  may use the identified facial features to authenticate the identity of the user of device  10 . For example, if the identified facial features match those of an authorized user stored on control circuitry  28 , control circuitry  28  may unlock device  10  or may otherwise authorize or unlock software and/or hardware features on device that are only available to authorized users. Control circuitry  28  may perform image processing operations such as object detection and recognition operations on visible and/or infrared image data captured using the image sensors in device  10 . 
     The image data may, for example, be indicative of how device  10  is being used or held by a user. Control circuitry  28  may process the image data to help identify how device  10  is being used or held by a user (e.g., to help identify the operating environment for device  10 ). For example, if control circuitry  28  determines that a user&#39;s face is currently facing display  14  using the facial recognition image data (or using image data captured using a visible light front-facing image sensor), control circuitry  28  may determine that device  10  is not being held against the user&#39;s ear. Similarly, if control circuitry  28  determines that the user&#39;s left ear is facing display  14  using the facial recognition image data or other image data captured using the front facing image sensors, control circuitry  28  may determine that device  10  is being held against the user&#39;s left ear (e.g., with the user&#39;s left hand). If control circuitry  28  determines that the user&#39;s right ear is facing display  14  using the facial recognition image data or other image data captured using the front facing image sensors, control circuitry  28  may determine that device  10  is being held against the user&#39;s right ear (e.g., with the user&#39;s right hand). These examples are merely illustrative and, in general, control circuitry  28  may process the image data in any desired manner. 
     If desired, control circuitry  28  may gather audio data (e.g., microphone data) using audio sensors such as one or more microphones in device  10  (step  102 ). The microphone data may include voice data generated by the voice of the user. If desired, device  10  may include multiple microphones that each generate microphone data. Control circuitry  28  may process the relative magnitude (volume) of voice data in the microphone data gathered by each microphone and/or time delays in the voice data between each of the microphones to help identify a relative angle between the user&#39;s mouth and device  10  (e.g., an angle of arrival of the voice in the microphone data). Control circuitry  28  may use this angle of arrival to help determine the operating environment for device  10 . For example, control circuitry  28  may use this angle of arrival to determine whether the user is holding device  10  against the side of their head or if the user is holding device  10  away from their head. 
     If desired, control circuitry  28  may gather position and orientation sensor data using position and orientation sensors (e.g., sensors such as accelerometers, gyroscopes, and compasses) (step  104 ). The position and orientation sensor data may, if desired, include motion sensor data associated with how device  10  is moving over time. Control circuitry  28  may process the position and orientation sensor data to help identify the operating environment for device  10 . For example, if control circuitry  28  determines from the position and orientation sensor data that display  14  is facing upwards, control circuitry  28  may determine that device  10  is not being held against a user&#39;s head. 
     If desired, control circuitry  28  may gather display sensor data using sensor circuitry in display  14  (step  106 ). The display sensor data may include touch sensor data and/or force sensor data. The display may include touch sensor circuitry for generating the touch sensor data and, if desired, may include force sensor circuitry for generating the force sensor data. The touch sensor circuitry may include, for example, capacitive and/or resistive touch sensor electrodes integrated within display  14  ( FIG. 1 ). The force sensor circuitry may include any desired force or pressure sensor circuitry for detecting how hard a user is pressing down onto display  14  (e.g., at one or more locations across the face of display  14 ). 
     In one suitable arrangement, the display sensor data may include a grip map that maps each of the locations across the face of display  14  that are being contacted by the user&#39;s hand at any given time. The grip map may include, for example, multiple points in scenarios where the user&#39;s hand contacts display  14  at multiple points at once. If desired, the grip map may also include force sensor data indicative of how hard the user is pressing down at each of these locations. The grip map may, for example, be an array that includes entries (e.g., rows) for each contact location across the lateral face of display  14  at a given time. Each entry may include the X and Y locations across the lateral face of display  14  that are being contacted as well as a force sensor data value indicative of the amount of pressure with which that contact is being applied to display  14 , for example. 
     Control circuitry  28  may process the grip sensor data to help identify the operating environment for device  10 . For example, control circuitry  28  may determine which hand is being used to hold device  10  and/or the location of that hand on housing  12  based on the locations and/or force with which the user&#39;s hand is contacting the surface of display  14 . If desired, control circuitry  28  may store predetermined (calibrated) grip maps that are associated with different known ways of holding device  10 . Control circuitry  28  may identify predetermined grip maps that the match gathered grip maps to identify how the user is holding device  10 . 
     If desired, control circuitry  28  may gather proximity sensor data using a proximity sensor such as a capacitive proximity sensor (step  108 ). The proximity sensor data may be indicative of how close an external object is located to the proximity sensor and thus to device  10 . In one suitable arrangement, the proximity sensor may be located at the front face of device  10  (e.g., within inactive area IA of display  14  of  FIG. 1 ). Control circuitry  28  may process the proximity sensor data to help identify the operating environment for device  10 . For example, if control circuitry  28  determines from the proximity sensor data that an external object is in very close proximity (e.g., within a predetermined distance) of the proximity sensor, control circuitry  28  may determine that a user is holding device  10  to their ear. 
     If desired, control circuitry  28  may gather light sensor data using light sensors such as one or more ambient light sensors (step  112 ). The light sensor data may be indicative of the brightness or darkness of the immediate surroundings of device  10 . Device  10  may include a light sensor at the front face of device  10  and/or a light sensor at the rear face of device  10 . Control circuitry  28  may process the light sensor data to help identify the operating environment for device  10 . For example, if control circuitry  28  determines from the light sensor data that the surroundings of device  10  are bright, control circuitry  28  may determine that device  10  is not located within the user&#39;s pocket and/or that device  10  is not being held against the user&#39;s ear. 
     If desired, control circuitry  28  may perform spatial ranging operations to monitor the operating environment of device  10  (step  110 ). Control circuitry  28  may control transceiver circuitry in device  10  to perform spatial ranging operations using one or more desired antennas  40  (e.g., antennas  40 - 1 ,  40 - 2 ,  40 - 3 , or  40 - 4  of  FIG. 4  or other antennas in device  10 ). Spatial ranging operations may involve one-way communications that do not require external communications equipment. The spatial ranging operations may include range detection operations, external object detection operations, and/or external object tracking operations, for example. 
     In performing spatial ranging operations, the transceiver circuitry may transmit a signal such as a sequence (e.g., series) of pulses or other predetermined signals at radio frequencies using a corresponding antenna  40  (e.g., based on a RADAR protocol or other range or object detection protocol). The transceiver circuitry may then wait for receipt of a reflected version of the transmitted signal that has been reflected off of an external object in the vicinity of device  10  (e.g., within a line-of-sight of device  10 ). Upon receiving the reflected version of the transmitted signal, the transceiver circuitry or control circuitry  28  may compare the transmitted signal (e.g., the sequence of pulses in the transmitted signal) to the received reflected version of the transmitted signal (e.g., the sequence of pulses in the received signal). Control circuitry  28  may use this comparison to identify a distance between device  10  and the external object (e.g., based on a time delay between the transmitted signal and the received signal and the known propagation speed of the signals over the air and using the range or object detection protocol). If desired, control circuitry  28  may also use transmitted and the received reflected radio-frequency signals to identify an angle of arrival of the reflected signals to help track external objects near to device  10 . These distances and angles may sometimes be referred to herein as radio-frequency spatial ranging data. The sequence of pulses may, for example, allow the transceiver circuitry to identify that any given received signal is a reflected version of the transmitted signal instead of some other signal received at device  10  (e.g., because the sequence of pulses will be the same for the reflected version of the transmitted signal as the known sequence of pulses in the transmitted signal). Control circuitry  28  may gather radio-frequency spatial ranging data using one or more antennas  40  and may use the radio-frequency spatial ranging data to help identify the operating environment for device  10 . The radio-frequency spatial ranging data may be gathered using signals at any desired frequencies such as ultra-wideband frequencies between about 5 GHz and 8.3 GHz. 
     If desired, control circuitry  28  may identify a usage scenario for device  10  (e.g., operations that are being performed by device  10 ) to help determine the operating environment for device  10 . For example, control circuitry  28  may identify software or processing tasks that are being performed by device  10 , may determine whether device  10  is currently being used to make a telephone call, whether device  10  is sending or receiving a text message or email, being used to browse the internet, etc. 
     In one suitable arrangement, device  10  may identify the audio state of device  10  (step  94 ). The audio state may include information indicative of how device  10  is being used to play audio over one or more speakers such as ear speaker  8  of  FIG. 1 . The audio state may also include information indicative of whether device  10  is being operated in a speaker phone mode. Control circuitry  28  may process the identified audio state to help identify the operating environment of device  10 . For example, if control circuitry  28  determines that ear speaker  8  is being used to play audio, control circuitry  28  may determine that device  10  is likely being held to a user&#39;s ear. If control circuitry  28  determines that ear speaker  8  is not being used to play audio, control circuitry  28  may determine that device  10  is likely not being held to the user&#39;s ear. 
     As another example, device  10  may identify the wireless communications state of device  10  (step  96 ). The wireless communications state may include information indicative of the wireless protocols that are currently being used to perform wireless communications and/or information indicative of the type of external equipment being used to wirelessly communicate with device  10 . Control circuitry  28  may process the identified wireless communications state to help identify the operating environment of device  10 . 
     For example, if control circuitry  28  determines that device  10  is wirelessly communicating with wireless headphones using a Bluetooth link, control circuitry  28  may determine that device  10  is not being held against the user&#39;s ear. As another example, if control circuitry  28  determines that device  10  is not being used to wirelessly convey signals using a cellular telephone protocol, device  10  may determine that device  10  is not being held against the user&#39;s ear. As yet another example, if control circuitry  28  determines that device  10  is communicating with a vehicular audio system (e.g., an audio system in a car or other automobile) using a WLAN or Bluetooth link, control circuitry  28  may determine that device  10  is placed on a surface in a vehicle (e.g., a vehicle dashboard). 
     These examples are merely illustrative. Control circuitry  28  may perform, none, one, more than one, or all of steps  92 - 112 , and/or any other desired operations in monitoring the operating environment of device  10 . Steps  92 - 112  may be performed in any desired order and/or concurrently. Control circuitry  28  may use any desired combination of the information gathered (identified) at steps  92 - 112  in identifying the operating environment of device  10 . Using combinations of sensor data and other information as gathered while processing steps  92 - 112  may allow control circuitry  28  to more reliably or accurately determine the operating environment for device  10  than in scenarios where only one type of sensor data is used, for example. Control circuitry  28  may use some types of sensor data for monitoring the operating environment at some times and may use other types of sensor data for monitoring the operating environment at other times. This may, for example, allow control circuitry  28  to monitor the operating environment using the least resource-intensive sensors at any given time and/or to divert resources that would be used for some sensors to other device operations, as examples. 
     At step  114 , control circuitry  28  may select antenna settings for wireless communications circuitry  34  based on the monitored operating environment for device  10  (e.g., as identified while processing step  90 ). For example, control circuitry  28  may select one or more active antennas  40  to use for performing radio-frequency communications (step  116 ). In scenarios where wireless communications circuitry  34  operates using a MIMO scheme, control circuitry  28  may select a pair of active antennas or more than two active antennas. As one example, control circuitry  28  may disable antennas that are undesirably loaded and detuned by the presence of external objects and may activate antennas that are not excessively loaded by external objects. Control circuitry  28  may activate antennas by switching the antennas into use and/or by activating (enabling) corresponding ports on transceiver circuitry  26  ( FIG. 2 ). 
     If desired, control circuitry  28  may select active antenna feeds based on the operating environment of device  10  (step  118 ). For example, control circuitry  28  may selectively activate one of positive antenna feed terminals  46 A or  46 B of  FIG. 7  based on the operating environment. Adjusting the feed location for the antennas in this way may adjust the electric field distribution for the antennas to help to mitigate antenna loading by external objects. 
     If desired, control circuitry  28  may select desired operating frequencies based on the operating environment of device  10  (step  120 ). For example, if the antennas are undesirably loaded within a particular frequency band, control circuitry  28  may change the operating frequency of the antennas to frequencies outside of that frequency band to mitigate degradation in antenna efficiency. 
     If desired, control circuitry  28  may select maximum transmit power levels for antennas  40  based on the operating environment of device  10  (step  122 ). For example, if control circuitry  28  determines that a particular antenna is being loaded by the user&#39;s body or is otherwise in close proximity to the user&#39;s body, control circuitry  28  may limit the maximum transmit power level for that antenna to ensure that standards on absorbed radio-frequency energy are met. As another example, if control circuitry  28  determines that no antennas are in proximity to the user&#39;s body, control circuitry  28  may operate the antennas with a higher maximum transmit power level than when the user&#39;s body is in close proximity to device  10 . 
     If desired, control circuitry  28  may select antenna tuning settings for the antennas based on the operating environment of device  10  (step  124 ). For example, if control circuitry  28  determines that a particular antenna is being loaded by an external object, control circuitry  28  may adjust antenna tuning circuitry such as tunable components  42  of  FIG. 3  (e.g., aperture tuning circuitry and/or matching circuitry) to mitigate any degradation in antenna efficiency on caused by the loading. 
     These examples are merely illustrative. Control circuitry  28  may perform, none, one, more than one, all of steps  116 - 124 , or other antenna adjustments in selecting the antenna settings for wireless communications circuitry  34 . Using different combinations of the operations of steps  116 - 124  may allow wireless communications circuitry  34  to achieve satisfactory antenna efficiency in desired frequency bands of interest using two or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  (e.g., for performing communications using a MIMO scheme), while also satisfying limits on radio-frequency absorption, regardless of the operating environment for device  10 . 
     At step  126 , wireless communications circuitry  34  may be used to transmit and receive radio-frequency signals (e.g., wireless data) using the selected antenna settings (e.g., as selected during step  114 ). This process may be performed continuously, as indicated by line  128 . 
     Control circuitry  28  may place wireless communications circuitry  34  into a desired operating mode based on the monitored operating environment of device  10 . Each operating mode may correspond to a particular monitored (detected) operating environment. Each operating mode may include a corresponding set of antenna settings that are used to control wireless communications circuitry  34  (e.g., control circuitry  28  may place wireless communications circuitry  34  into a particular operating mode while processing step  114  of  FIG. 8 ). 
     A state diagram  130  of illustrative operating modes (states) for wireless communications circuitry  34  is shown in  FIG. 9 . As shown in  FIG. 9 , control circuitry  28  may place wireless communications circuitry  34  into one of four different operating modes such as a first operating mode  132 , a second operating mode  136 , a third operating mode  140 , and a fourth operating mode  144 . Control circuitry  28  may determine the operating mode to use based on the information identified while processing step  90  of  FIG. 8 . 
     For example, when control circuitry  28  determines that device  10  is being held to the head or ear of a user (e.g., while processing step  90  of  FIG. 8 ), control circuitry  28  may place wireless communications circuitry  34  in first operating mode  132  (sometimes referred to as head mode  132 ). Head mode  132  may include a first set of antenna settings. Control circuitry  28  may place wireless communications circuitry  34  into head mode  132  by controlling (configuring) wireless communications circuitry  34  using the first set of antenna settings. 
     The first set of antenna settings may, for example, include a maximum transmit power level P 4  that is imposed on antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  ( FIG. 7 ). Maximum transmit power level P 4  may be lower than the maximum transmit power level used for the other operating modes. This may help to ensure that device  10  satisfies limits on absorbed radio-frequency energy while device  10  is in very close proximity to the head of a user. The first set of antenna settings may include any other desired antenna settings such as active antenna feed settings, operating frequencies, antenna tuning settings, and active antenna settings if desired. 
     When control circuitry  28  determines that device  10  is being held in the hand (but not against the head or ear) of a user (e.g., while processing step  90  of  FIG. 8 ), control circuitry  28  may place wireless communications circuitry  34  in second operating mode  136  (sometimes referred to as hand mode  136 ). Hand mode  136  may include a second set of antenna settings. Control circuitry  28  may place wireless communications circuitry  34  into hand mode  136  by controlling (configuring) wireless communications circuitry  34  using the second set of antenna settings. 
     The second set of antenna settings may, for example, include a maximum transmit power level P 3  that is imposed on antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  ( FIG. 7 ). Maximum transmit power level P 3  may be greater than maximum transmit power level P 4  (e.g., because there may be less radio-frequency absorption by the user when the user holds device  10  in their hand and away from their head than when the user holds device  10  to their head). Maximum transmit power level P 3  may be less than maximum transmit power level P 1  associated with a free space operating environment (e.g., to help ensure that device  10  satisfies limits on absorbed radio-frequency energy while device  10  is being held by the user). The second set of antenna settings may include any other desired antenna settings such as active antenna feed settings, operating frequencies, antenna tuning settings, and active antenna settings if desired. 
     When control circuitry  28  determines that device  10  is not being held by a user and that device  10  is not being operated on a vehicle surface (e.g., while processing step  90  of  FIG. 8 ), control circuitry  28  may place wireless communications circuitry  34  in third operating mode  140  (sometimes referred to as free space mode  140 ). Free space mode  140  may include a third set of antenna settings. Control circuitry  28  may place wireless communications circuitry  34  into free space mode  140  by controlling (configuring) wireless communications circuitry  34  using the third set of antenna settings. 
     The third set of antenna settings may, for example, include a maximum transmit power level P 1  that is imposed on antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  ( FIG. 7 ). Maximum transmit power level P 1  may be greater than maximum transmit power levels for the other operating modes of wireless communications circuitry  34  (e.g., because the radio-frequency signals will not be substantially absorbed by a user in a free space environment). The third set of antenna settings may include any other desired antenna settings such as active antenna feed settings, operating frequencies, antenna tuning settings, and active antenna settings if desired. 
     When control circuitry  28  determines that device  10  is placed on a vehicle surface (e.g., while processing step  90  of  FIG. 8 ), control circuitry  28  may place wireless communications circuitry  34  in fourth operating mode  144  (sometimes referred to as vehicle mode  144 ). The vehicle surface may include a dashboard of a vehicle such as a car or other automobile, an electronic device mount affixed to the dashboard, a cup-holder, a wireless-charging surface (pad) within the vehicle, or other surfaces within the vehicle. 
     Vehicle mode  144  may include a fourth set of antenna settings. Control circuitry  28  may place wireless communications circuitry  34  into vehicle mode  144  by controlling (configuring) wireless communications circuitry  34  using the fourth set of antenna settings. The fourth set of antenna settings may, for example, include a maximum transmit power level P 2  that is imposed on antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  ( FIG. 7 ). Maximum transmit power level P 2  may be less than maximum transmit power level P 1  of free space mode  140  (e.g., due to the likely presence of people within the vehicle and/or electronic equipment in the vehicle that may be sensitive to radio-frequency signals transmitted by device  10 ). Maximum transmit power level P 2  may be equal to, less than, or greater than maximum transmit power level P 3  of hand mode  136 . The fourth set of antenna settings may include any other desired antenna settings such as active antenna feed settings, operating frequencies, antenna tuning settings, and active antenna settings if desired. 
     Each operating mode may include corresponding operating sub-modes. Once control circuitry  28  places wireless communications circuitry  34  into one of operating modes  132 ,  136 ,  140 , or  144 , control circuitry  28  may further adjust the antenna settings based on the monitored operating environment by placing wireless communications circuitry  34  into a selected operating sub-mode corresponding to the selected operating mode. Each operating sub-mode may correspond to a particular monitored (detected) operating environment. Each operating sub-mode may include a corresponding set of antenna settings that are used to control wireless communications circuitry  34  (e.g., control circuitry  28  may place wireless communications circuitry  34  into a particular operating sub-mode while processing step  114  of  FIG. 8 ). 
     As shown in  FIG. 9 , control circuitry  28  may place device  10  into a selected operating sub-mode  134  (e.g., a first sub-mode MA 1 , a second sub-mode MA 2 , etc.) while wireless communications circuitry  34  is in head mode  132 . As an example, control circuitry  28  may place wireless communications circuitry  34  into operating sub-mode MA 1  when device  10  is being held to the left ear of a user and may place wireless communications circuitry  34  into operating sub-mode MA 2  when device  10  is being held to the right ear of a user. 
     Control circuitry  28  may place device  10  into a selected operating sub-mode  138  (e.g., a first sub-mode MB 1 , a second sub-mode MB 2 , etc.) while wireless communications circuitry  34  is in hand mode  136 . As an example, control circuitry  28  may place wireless communications circuitry  34  into operating sub-mode MB 1  when device  10  is being held in a portrait orientation with the user&#39;s left hand and may place wireless communications circuitry  34  into operating sub-mode MB 2  when device  10  is being held in a landscape orientation with both of the user&#39;s hands. 
     Control circuitry  28  may place device  10  into a selected operating sub-mode  142  (e.g., a first sub-mode MC 1 , a second sub-mode MC 2 , etc.) while wireless communications circuitry  34  is in free space mode  140 . As an example, control circuitry  28  may place wireless communications circuitry  34  into operating sub-mode MC 1  when device  10  is resting face up on a non-vehicle surface and may place wireless communications circuitry  34  into operating sub-mode MC 2  when device  10  is resting face down on a non-vehicle surface. 
     Control circuitry  28  may place device  10  into a selected operating sub-mode  146  (e.g., a first sub-mode MD 1 , a second sub-mode MD 2 , etc.) while wireless communications circuitry  34  is in vehicle mode  144 . As an example, control circuitry  28  may place wireless communications circuitry  34  into operating sub-mode MD 1  when device  10  is resting on a wireless charging pad in a vehicle and may place wireless communications circuitry  34  into operating sub-mode MD 2  when device  10  is affixed to a vehicle dashboard using an electronic device mount. 
     The example of  FIG. 9  is merely illustrative. In general, wireless communications circuitry  34  may have any desired number of operating modes corresponding to any desired operating environment and each operating mode may include zero, one, two, more than two, or any desired number of operating sub-modes. Control circuitry  28  may dynamically adjust the antenna settings for wireless communications circuitry  34  (e.g., control circuitry  28  may dynamically adjust the operating modes and operating sub-modes for wireless communications circuitry  34 ) as the operating environment for device  10  changes over time. 
       FIG. 10  is a flow chart of illustrative steps involved in operating control circuitry  28  to adjust wireless communications circuitry  34  between different operating modes and operating sub-modes. At step  148 , control circuitry  28  may identify an operating mode to use for wireless communications circuitry  34  (e.g., while processing step  114  of  FIG. 8 ) based on the monitored operating environment for device  10  (e.g., as monitored while processing step  90  of  FIG. 8 ). 
     As an example, control circuitry  28  may identify that head mode  132  is to be used when control circuitry  28  determines that audio data is being played through ear speaker  8  ( FIG. 1 ), when position and orientation sensor data indicates that device  10  is being held in an upright position, when position and orientation sensor data indicates that device  10  exhibits periodic motion patterns associated with being held by a user, when proximity sensor data indicates that an external object is in close proximity to device  10 , when impedance sensor data indicates that antenna  40 - 1  and/or  40 - 2  are being loaded by an external object, when a grip map for display  14  indicates that a user is holding device  10  with a single hand in a portrait orientation, when image data gathered by a front-facing image sensor on device  10  indicates that a user&#39;s face or ear is facing display  14 , when ambient light sensor data indicates relatively dark ambient conditions at the front face of device  10  and relatively bright ambient conditions at the rear face of device  10 , when radio-frequency spatial ranging operations indicate that an external object is in relatively close proximity to device  10 , when microphone data indicates that the user&#39;s mouth is located at an angle with respect to device  10  that is associated with the user holding device  10  to their head, when control circuitry  28  determines that device  10  is being used to place a cellular telephone call, and/or any desired combination of these factors and/or other factors. 
     Control circuitry  28  may identify that hand mode  136  of  FIG. 9  is to be used when, for example, control circuitry  28  determines that audio data is not being played through ear speaker  8  ( FIG. 1 ), when position and orientation sensor data indicates that device  10  is being held in a position consistent with handheld use away from the user&#39;s head, when position and orientation sensor data indicates that device  10  exhibits periodic motion patterns associated with being held by a user, when proximity sensor data indicates that an external object is in close proximity to device  10 , when impedance sensor data indicates that one or more antennas  40  are being loaded by an external object, when a grip map for display  14  indicates that a user is holding device  10  with a single hand or both hands in a portrait or landscape orientation, when image data gathered by a front-facing image sensor on device  10  indicates that a user&#39;s face or ear is not near to or facing display  14 , when radio-frequency spatial ranging operations indicate that an external object is in relatively close proximity to device  10 , when microphone data indicates that the user&#39;s mouth is located at an angle with respect to device  10  that is associated with the user holding device  10  away from their head, when control circuitry  28  determines that device  10  is being not being used to place a cellular telephone call, and/or any desired combination of these factors and/or other factors. 
     Control circuitry  28  may identify that free space mode  140  of  FIG. 9  is to be used when control circuitry  28  determines that audio data is not being played through ear speaker  8  ( FIG. 1 ), when position and orientation sensor data indicates that device  10  is in a stationary position (e.g., a stationary face-up or face-down position), when impedance sensor data indicates that antennas  40  are not being significantly loaded by an external object, when a grip map for display  14  indicates that a user is not holding device  10 , when image data gathered image sensors on device  10  indicate that a user&#39;s body is not near to device  10 , when ambient light sensor data indicates relatively dark ambient conditions at one side of device  10  and relatively bright ambient conditions at another side of device  10 , when microphone data indicates that the user&#39;s mouth is located relatively far away from device  10 , and/or any desired combination of these factors and/or other factors. 
     Control circuitry  28  may identify that vehicle mode  144  of  FIG. 9  should be used when control circuitry  28  determines that audio data is not being played through ear speaker  8  ( FIG. 1 ), when control circuitry  28  determines that device  10  is operating in a speaker phone mode, when position and orientation sensor data indicates that device  10  is undergoing periodic or predetermined motion (vibration) patterns associated with travel in a vehicle, when impedance sensor data indicates that antennas  40  are not being significantly loaded by an external object, when microphone data indicates that the user&#39;s mouth is located relatively far away from device  10 , when control circuitry  28  determines that wireless communications circuitry  34  is wirelessly communicating with a vehicular audio system using a Bluetooth or WLAN link, and/or any desired combination of these factors and/or other factors. 
     At step  150 , control circuitry  28  may place wireless communications circuitry  34  into the identified operating mode by configuring wireless communications circuitry  34  with the antenna settings associated with the identified operating mode. For example, control circuitry  28  may place wireless communications circuitry  34  in head mode  132  by imposing maximum transmit power level P 4  on antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and/or  40 - 4 , may place wireless communications circuitry  34  in hand mode  136  using maximum transmit power level P 3 , may place wireless communications circuitry  34  in free space mode  140  using maximum transmit power level P 1 , and may place wireless communications circuitry  34  in vehicle mode  144  using maximum transmit power level P 2  ( FIG. 9 ). 
     At step  152 , control circuitry  28  may identify an operating sub-mode to use for wireless communications circuitry  34  (e.g., while processing step  114  of  FIG. 8 ) based on the monitored operating environment for device  10  (e.g., as monitored while processing step  90  of  FIG. 8 ). 
     For example, when wireless communications circuitry  34  is in head mode  132 , control circuitry  28  may identify that a first operating sub-mode should be used (e.g., one of operating sub-modes  134  of  FIG. 9 ) when device  10  is being held to the user&#39;s left ear, may identify that a second operating sub-mode should be used when device  10  is being held to the user&#39;s right ear, may identify that a third operating sub-mode should be used when device  10  is separated from the user&#39;s left ear by a predetermined distance, may identify that a fourth operating sub-mode should be used when device  10  is separated from the user&#39;s right ear by a predetermined distance, may identify that a fifth operating sub-mode should be used when a user is holding device  10  to their chin, etc. 
     Control circuitry  28  may identify the sub-mode of head mode  132  to use based on any desired combination of the information gathered while processing step  90  of  FIG. 8 . In one suitable arrangement, control circuitry  28  may identify the operating sub-mode to use based on image data, proximity sensor data, spatial ranging data, grip map data, and/or impedance data. For example, control circuitry  28  may identify that the first operating sub-mode should be used when image data captured by a front-facing image sensor includes an image of the user&#39;s left ear, when the proximity sensor data indicates that an external object is in close proximity to device  10 , and/or when the impedance data and/or grip map data indicates that the user is holding device  10 . As another example, control circuitry  28  may identify that the third operating sub-mode should be used when the proximity sensor data and/or the image data indicates that the user&#39;s left ear is located relatively far from device  10 . These examples are merely illustrative and any desired sensor data may be used in any desired manner. 
     When wireless communications circuitry  34  is in hand mode  136 , control circuitry  28  may, for example, identify that a first operating sub-mode (e.g., one of operating sub-modes  138  of  FIG. 9 ) should be used when device  10  is being held in a portrait orientation by the user&#39;s left hand, that a second operating sub-mode should be used when device  10  is being held in a portrait orientation by the user&#39;s right hand, that a third operating sub-mode should be used when device  10  is being held in a landscape orientation by the user&#39;s left hand, that a fourth operating sub-mode should be used when device  10  is being held in a landscape orientation by both of the user&#39;s hands, etc. Control circuitry  28  may identify the sub-modes of hand mode  136  to sue based on any desired combination of the information gathered while processing step  90  of  FIG. 8 . For example, control circuitry  28  may identify the operating sub-mode to use based on grip map data, position and orientation sensor data, and/or impedance data. 
     When wireless communications circuitry  34  is in free space mode  140 , control circuitry  28  may, for example, identify that a first operating sub-mode (e.g., one of operating sub-modes  142  of  FIG. 9 ) should be used when device  10  is placed in a face-up orientation, that a second operating sub-mode should be used when device  10  is placed in a face-down orientation, etc. Control circuitry  28  may identify the sub-modes of hand mode  136  to use based on any desired combination of the information gathered while processing step  90  of  FIG. 8  (e.g., orientation sensor data, ambient light sensor data, impedance sensor data, etc.). 
     When wireless communications circuitry  34  is in vehicle mode  144 , control circuitry  28  may, for example, identify that a first operating sub-mode (e.g., one of operating sub-modes  146  of  FIG. 9 ) should be used when device  10  is placed in a face-up orientation on a vehicle surface, that a second operating sub-mode should be used when device  10  is affixed to a vehicle dashboard using an electronic device mount, etc. Control circuitry  28  may identify the sub-modes of hand mode  136  to use based on any desired combination of the information gathered while processing step  90  of  FIG. 8  (e.g., orientation sensor data, ambient light sensor data, etc.). 
     At step  154 , control circuitry  28  may place wireless communications circuitry  34  into the identified operating sub-mode by configuring wireless communications circuitry  34  with the antenna settings associated with the identified operating sub-mode. For example, control circuitry  28  may place wireless communications circuitry  34  into the identified operating sub-mode by activating selected antenna feeds, activating selected antennas, selecting desired frequencies, and/or by selecting tuning settings for the antennas. If desired, control circuitry  28  may further adjust the transmit power level and/or maximum transmit power level when placing wireless communications circuitry  34  in the identified operating sub-mode. 
     At step  156 , wireless communications circuitry  34  may be used to transmit and receive radio-frequency signals (e.g., wireless data) using the identified operating mode and operating sub-mode. This process may be performed continuously, as indicated by line  158 . By placing wireless communications circuitry  34  into a desired operating mode before further placing the circuitry into a desired operating sub-mode, wireless communications circuitry  34  may ensure that a desired maximum transmit power level is established before further antenna refinements are performed (e.g., to ensure that device  10  satisfies limits on radio-frequency absorption even while steps  152 - 154  are performed). 
     If desired, control circuitry  28  may verify the radio-frequency performance of wireless communications circuitry  34  after each antenna setting adjustment. For example, control circuitry  28  may gather impedance data or other data indicative of antenna performance after performing step  150  and, if the wireless communications circuitry exhibits insufficient performance, may select a different operating mode to use and/or may sweep through antenna settings until a satisfactory antenna setting is found. Similarly, control circuitry  28  may gather impedance data or other data indicative of antenna performance after performing step  154  and, if the wireless communications circuitry exhibits insufficient performance, may select a different operating sub-mode to use and/or may sweep through antenna settings until a satisfactory antenna setting is found. 
     In one suitable arrangement, control circuitry  28  may identify the operating mode and operating sub-mode based on predetermined (e.g., stored) antenna settings that are known to be associated with the corresponding operating environment. In another suitable arrangement, control circuitry  28  may sweep through different operating modes and operating sub-modes (e.g., while processing steps  148  and  154 ), may gather radio-frequency performance metric data at each step in the sweep, and may process the gathered radio-frequency performance metric data until an optimal operating mode or operating sub-mode is found (e.g., antenna settings that maximize antenna efficiency while satisfying limits on absorbed radio-frequency energy). 
       FIG. 11  is a perspective view of device  10  showing how different sensors may be used for gathering sensor data that is used to identify the operating environment of device  10  (e.g., while processing step  90  of  FIG. 8 ). 
     As shown in  FIG. 11 , display  14  may be located at front face  160  of device  10 . One or more rear-facing image sensors  164  may be located at the opposing rear face  162  of device  10 . Rear-facing image sensors  164  may generate image data in response to visible and/or infrared light. Sensors and other components such as ear speaker  8  may be located at front face  160  within upper region  22  of device  10 . 
     In the example of  FIG. 11 , a first front-facing image sensor  166 , a second front-facing image sensor  172 , and ambient light sensor  168  are located at front face  160 . A capacitive proximity sensor may also be located at front face  160  within upper region  22  if desired. Image sensor  166  may generate image data in response to visible light. If desired, image sensor  166  may also capture light at some infrared wavelengths. Image sensor  172  may generate image data in response to infrared light. If desired, image sensor  172  may also capture light at some visible wavelengths. Light emitting components such as light sources  170  and  165  may be located at front face  160 . Light sources  170  and/or  165  may emit infrared light  174 . Infrared light  174  may be reflected off of objects in front of display  14  such as the user&#39;s face or ears. This reflected infrared light  174 ′ may be captured by image sensor  172  as facial recognition image sensor data, if desired. Light source  174  may be a dot projector and light source  170  may be a flood illuminator, as examples. This example is merely illustrative and, in general, any desired light sources and/or sensors may be formed at front face  160  of device  10 . 
     As shown in  FIG. 11 , display  14  may gather touch and/or force sensor data indicative of how a user is gripping device  10 . This data may include a grip map that maps the locations and/or force of contact between the user&#39;s hand and display  14 . The grip map may identify regions (locations)  176  such as regions  176 A,  176 B,  176 C,  176 D,  176 E,  176 F, and/or other locations across display  14  that are being touched by the user&#39;s hand. This data may be used to determine the operating mode and/or operating sub-mode for wireless communications circuitry  34 . 
     As an example, when a user is holding device  10  in a landscape orientation with both hands, the grip map may include data for locations  176 C and  176 A indicative of the user&#39;s hand contacting display  14  at locations  176 C and  176 A. As another example, when a user is holding device  10  in a portrait orientation with their left hand, the grip map may include data for location  176 D associated with the user&#39;s thumb or palm contacting display  14  and/or data for location  176 B associated with the user&#39;s fingertips contacting display  14 . These examples are merely illustrative and, in general, the grip map may be used to characterize any manner with which the user holds device  10 . This display sensor data as well as sensor data gathered by sensors  172 ,  166 ,  168 ,  164 , and/or other sensors may be used to identify the operating environment of device  10  and thus the operating mode and/or operating sub-mode for wireless communications circuitry  34 . 
       FIG. 12  is a side-view showing how control circuitry  28  may use multiple microphones for identifying the orientation of device  10  relative to the user (e.g., while processing step  102  of  FIG. 8 ). As shown in  FIG. 12 , device  10  may include multiple microphones  178  at different locations across the device. Each microphone may gather audio data from the user&#39;s voice. Control circuitry  28  may process the audio data from each microphone to determine relative volumes (magnitudes) of the user&#39;s voice from each microphone and/or time delays between the microphones. Control circuitry  28  may use this data (and known distances between each of the microphones) to determine the angle of arrival  184  of the user&#39;s voice. When control circuitry  28  determines that angle of arrival  184  is approximately zero (e.g., normal to a face of device  10 ), control circuitry  28  may determine that the user&#39;s voice is located at location  180 . When control circuitry  28  determines that angle of arrival  184  is larger, control circuitry  28  may determine that the user&#39;s voice is located at another location such as location  182 . In this way, microphones  178  may help to track the location of the user&#39;s voice (and thus the location of the user&#39;s mouth and head) relative to device  10 . This process may be used to determine angle of arrival of the audio captured by microphones  178  and may sometimes be referred to herein as microphone beam forming. 
     Control circuitry  28  may use this information to help determine the operating environment and thus the operating mode and sub-mode to use for wireless communications circuitry  34 . For example, when the microphone data indicates that the user&#39;s mouth is located at location  182 , control circuitry  28  may determine that device  10  is not being held against the user&#39;s head. Control circuitry  28  may determine that device  10  is being held against the user&#39;s head when the microphone data indicates that the user&#39;s head is located at location  180 , for example. 
       FIG. 13  is a graph in which antenna performance (antenna efficiency) has been plotted as a function of operating frequency for antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and/or  40 - 4 . As shown in  FIG. 13 , curve  184  plots an exemplary antenna efficiency of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and/or  40 - 4  while wireless communications circuitry  34  is operating in an unsuitable operating mode or operating sub-mode for the given operating environment. For example, curve  184  may be associated with operation of wireless communications circuitry  34  in free space mode  140  ( FIG. 9 ) while device  10  is being held by a user, operation in hand mode  136  while device  10  is being held to a user&#39;s head, etc. 
     The antenna efficiency associated with curve  184  may be unsatisfactory (e.g., below a threshold efficiency) across a frequency band of interest (e.g., between frequencies F 1  and F 2 ). By placing wireless communications circuitry  34  in the operating mode and operating sub-mode corresponding to the current operating environment (e.g., while processing the steps of  FIGS. 8 and 10 ), antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and/or  40 - 4  may exhibit satisfactory antenna efficiency across the frequency band of interest, as shown by curve  186 . 
     The example of  FIG. 13  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  184  and  188  may have other shapes if desired. 
     In this way, control circuitry  28  may ensure that each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  have been adjusted to mitigate loading by different external objects at different locations with respect to device  10 . This may allow the antennas to operate with satisfactory antenna efficiency regardless of the operating environment of the device even if the operating environment changes over time. At the same time, wireless communications circuitry  34  may comply with regulatory or industry limits on absorbed radio-frequency energy and may communicate with a satisfactory data rate (e.g., using a MIMO scheme and two or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  at a given time). 
     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: 20180625
Publication Date: 20200623
Grant Date: 20200623
Priority Date: 20180625
Inventors: HAN, LIANG
MOW, MATTHEW A.
PASCOLINI, MATTIA
CABALLERO, RUBEN
BIEDKA, THOMAS E.
XU, YUANCHENG
RAMACHANDRAN, IYAPPAN
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/40", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/3838", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06V40/161", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F18/251", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06V10/143", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06V40/161", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06V10/143", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/40", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/72454", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/72454", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/3838", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/283", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06T7/521", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0264", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/03", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06T7/55", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/6008", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M2250/52", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/03", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0264", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06T7/521", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06K9/2018", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/72569", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06K9/6289", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/3838", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06T7/55", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/283", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 68982341