PATENT DOCUMENT

Publication Number: US-9179299-B2
Application Number: US-201514714991-A
Country: US
Kind Code: B2

Title: Adjustable wireless circuitry with antenna-based proximity detector

Abstract:
An electronic device such as a portable electronic device has wireless communications circuitry. Antennas in the electronic device may be used in transmitting radio-frequency antenna signals. A coupler and antenna signal phase and magnitude measurement circuitry may be used to determine when external objects are in the vicinity of the antenna by making antenna impedance measurements. In-band and out-of-band phase and magnitude signal measurements may be made in determining whether external objects are present. Additional sensors such as motion sensors, light and heat sensors, acoustic and electrical sensors may produce data that can be combined with the proximity data gathered using the antenna-based proximity sensor. In response to detecting that an external object such as a user&#39;s body is within a given distance of the antenna, the electronic device may reduce transmit powers, switch antennas, steer a phased antenna array, switch communications protocols, or take other actions.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 an antenna with which the electronic device transmits radio-frequency signals according to a wireless communications mode; 
 circuitry that is coupled to the antenna and that makes radio-frequency signal phase and magnitude measurements; and 
 storage and processing circuitry that determines whether an external object is adjacent to the antenna by processing the radio-frequency signal phase and magnitude measurements, wherein the storage and processing circuitry identifies what tasks are being performed by the electronic device and, in response to determining that the external object is adjacent to the antenna, adjusts the wireless communications mode based at least partly on the tasks that are being performed by the electronic device. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the circuitry comprises phase and magnitude detection circuitry. 
     
     
       3. The electronic device defined in  claim 1 , wherein the storage and processing circuitry is configured to identify tasks that are scheduled to be performed by the electronic device and, in response to determining that the external object is adjacent to the antenna, adjust the wireless communications mode based at least partly on the tasks that are scheduled to be performed by the electronic device. 
     
     
       4. The electronic device defined in  claim 3 , wherein the storage and processing circuitry is configured to, in response to determining that the external object is adjacent to the antenna, adjust the wireless communications mode based at least partly on whether a message is scheduled to be sent by the electronic device. 
     
     
       5. The electronic device defined in  claim 4 , wherein the message comprises an email message. 
     
     
       6. The electronic device defined in  claim 1 , wherein the storage and processing circuitry is configured to identify tasks that are likely to be performed by the electronic device and, in response to determining that the external object is adjacent to the antenna, adjust the wireless communications mode based at least partly on the tasks that are likely to be performed by the electronic device. 
     
     
       7. The electronic device defined in  claim 1 , wherein the storage and processing circuitry is configured to, in response to determining that the external object is adjacent to the antenna, adjust the wireless communications mode based at least partly on whether a telephone call is being performed by the electronic device. 
     
     
       8. The electronic device defined in  claim 1 , wherein the storage and processing circuitry is configured to, in response to determining that the external object is adjacent to the antenna, switch an additional antenna into use so that the additional antenna transmits the radio-frequency signals based at least partly on the tasks that are being performed by the electronic device. 
     
     
       9. The electronic device defined in  claim 1 , wherein the storage and processing circuitry is configured to, in response to determining that the external object is adjacent to the antenna, change a wireless communications protocol used by the electronic device to transmit the radio-frequency signals based at least partly on the tasks that are being performed by the electronic device. 
     
     
       10. The electronic device defined in  claim 1 , wherein the storage and processing circuitry is configured to, in response to determining that the external object is adjacent to the antenna, change a transmit power used by the electronic device to transmit the radio-frequency signals based at least partly on the tasks that are being performed by the electronic device. 
     
     
       11. The electronic device defined in  claim 1 , further comprising:
 a sensor configured to gather sensor data in response to the external object, wherein the storage and processing circuitry is configured adjust the communications mode based at least partly on the phase and magnitude measurements, the sensor data, and the tasks that are being performed by the electronic device. 
 
     
     
       12. A method of using an electronic device, the method comprising:
 transmitting radio-frequency antenna signals through an antenna; 
 with phase and magnitude detector circuitry that is coupled to the antenna in the electronic device, making radio-frequency antenna signal phase and magnitude measurements to produce proximity data; 
 with the control circuitry, identifying what task is being performed by the electronic device; and 
 with the control circuitry, adjusting a wireless communications mode of the electronic device based on the proximity data from the phase and magnitude detector circuitry and the identified task. 
 
     
     
       13. The method defined in  claim 12 , further comprising:
 with the control circuitry, determining whether an external object is adjacent to the antenna based on the proximity data from the phase and magnitude detector circuitry; and 
 with the control circuitry in response to determining that the external object is adjacent to the antenna, adjusting the wireless communications mode based on the identified task. 
 
     
     
       14. The method defined in  claim 12 , wherein identifying what task is being performed by the electronic device comprises:
 determining whether the electronic device is currently being used for a telephone call. 
 
     
     
       15. The method defined in  claim 13 , wherein adjusting the wireless communications mode comprises adjusting the wireless communications mode based on the proximity data and whether the electronic device is currently being used for the telephone call. 
     
     
       16. The method defined in  claim 12 , wherein identifying what task is being performed by the electronic device comprises:
 determining whether an email message has been queued for transmission over the antenna. 
 
     
     
       17. The method defined in  claim 12  wherein adjusting the wireless communications mode of the electronic device based on the proximity data and the identified task comprises:
 adjusting a selected one of antenna transmit power, wireless communications protocol, and a tunable circuit coupled to the antenna based on the proximity data and the identified task. 
 
     
     
       18. An electronic device, comprising:
 an antenna with which the electronic device transmits radio-frequency signals according to a wireless communications mode; 
 circuitry coupled to the antenna that gathers phase and magnitude data; and 
 storage and processing circuitry that is configured to identify what task is being performed by the electronic device and to adjust the wireless communications mode based at least partly on the phase and magnitude data and the task that is being performed by the electronic device. 
 
     
     
       19. The electronic device defined in  claim 18 , wherein the circuitry comprises phase and magnitude detection circuitry that makes phase and magnitude measurements to generate the phase and magnitude data. 
     
     
       20. The electronic device defined in  claim 18 , further comprising:
 an additional antenna, wherein the storage and processing circuitry is configured to adjust the wireless communications mode based at least partly on the task that is being performed by the electronic device by switching between a first communications mode in which the antenna and the additional antenna transmit the radio-frequency signals and a second communications mode in which only the antenna transmits the radio-frequency signals.

Description:
This application is a division of patent application Ser. No. 14/219,946, filed Mar. 19, 2014, which is a continuation of patent application Ser. No. 12/759,243, filed Apr. 13, 2010, each of which is hereby incorporated by reference herein in its entirety. This application claims the benefit of and claims priority to patent application Ser. No. 14/219,946, filed Mar. 19, 2014, which is a continuation of patent application Ser. No. 12/759,243, filed Apr. 13, 2010 
    
    
     BACKGROUND 
     This relates generally to wireless communications circuitry, and more particularly, to electronic devices that have wireless communications circuitry whose operation may be adjusted based on the proximity of the electronic devices to external objects. 
     Electronic devices such as computers and handheld electronic devices are becoming increasingly popular. Devices such as these are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry to communicate using cellular telephone bands. Electronic devices may use short-range wireless communications links to handle communications with nearby equipment. For example, electronic devices may communicate using the WiFi® (IEEE 802.11) bands at 2.4 GHz and 5 GHz and the Bluetooth® band at 2.4 GHz. 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components using compact structures. To satisfy regulatory guidelines for maximum emitted power, it may be desirable to limit the radio-frequency output of an electronic device. Care must be taken, however, to ensure that the proper wireless operation of the electronic device is not disrupted. If emitted wireless signal strengths are overly limited, a device may not function satisfactorily. 
     In view of these considerations, it would be desirable to provide improved wireless circuitry for electronic devices. 
     SUMMARY 
     Electronic devices such as portable electronic devices may be provided with one or more antennas. The antennas may operate in a common communications band (e.g., when implementing an antenna diversity arrangement) or may operate in separate communications bands. An array of antennas may be controlled using phase controllers to implement a phased antenna array capable of beam steering. Antennas may be provided with tunable matching networks, tunable feeds, tunable antenna resonating elements, and adjustable tuning circuits. 
     The electronic device may determine whether a user&#39;s body or other external object is within a given distance of an antenna by making antenna impedance measurements. The antenna impedance measurements may be made using signal phase and magnitude monitoring circuitry that is coupled to the antenna. 
     The electronic device may also include other sensors such as thermal sensors, infrared heat sensors, motion sensors, capacitance sensors, ambient light sensors, infrared light proximity sensors, acoustic sensors, cameras, electrical (resistance) sensors, etc. Data from each of these sensors may be used in addition to the antenna impedance measurement data to help accurately determine whether the external object is in the vicinity of the antenna. 
     Transceiver and power amplifier circuitry may be used in transmitting radio-frequency antenna signals through the antenna. A communications protocol, transmit data rate, and a given communications band may be used when transmitting signals. 
     Storage and processing circuitry may process information from an antenna-based proximity sensor and from other sensors and sources of data within the electronic device to determine when external objects are within a given distance of the antennas in the device are how to respond. Appropriate actions that may be taken when an external object is detected include adjustments to transmit power through the antenna, adjustments to the type of communications protocol that is being used, adjustments to the rate at which data is being wirelessly transmitted, and adjustments to the communications band that is being used for wireless transmissions. Antennas may be selectively disabled and may have their powers adjusted individually. In a phased antenna array, the direction in which the antenna array is operating may be adjusted. The antennas in the device may also be tuned in response to the detection of external objects by adjusting matching circuits, antenna feed locations, tuning circuits, and adjustable switches that control the size and shape of the active portions of antenna resonating elements within the antennas. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 3  is circuit diagram of illustrative wireless circuitry in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 4  is a circuit diagram showing illustrative circuitry that may be used to measure radio-frequency antenna signals in real time during operation of an electronic device in accordance with an embodiment of the present invention. 
         FIG. 5  is a Smith chart showing how antenna impedance may vary in response to the presence or absence of different types of external objects in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of an illustrative adjustable antenna matching circuit, an illustrative adjustable antenna feed, illustrative adjustable antenna tuning circuitry, and an adjustable antenna resonating element for an adjustable antenna in accordance with an embodiment of the present invention. 
         FIG. 7  is a schematic diagram of an illustrative electronic device with multiple antennas in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram of an illustrative phased antenna array that may be adjusted in real time using control circuitry in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 9  is a flow chart of illustrative steps involved in operating an electronic device with sensors and wireless circuitry in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications such as long-range wireless communications (e.g., communications in cellular telephone bands) and short-range communications (i.e., local area network links such as WiFi® links, Bluetooth® links, etc.). The wireless communications circuitry may include one or more antennas. 
     The electronic devices may include proximity sensors that are implemented using circuitry that monitors antenna signals. A proximity sensor of this type may, for example, discern whether a user&#39;s hand or other body part is in the vicinity of an antenna in an electronic device. Other sensor data may also be gathered by the device. 
     Processing circuitry may be used to process the antenna signal proximity sensor data and other data to determine when it is necessary to adjust the wireless circuitry. The processing circuitry may decide to adjust the wireless circuitry whenever appropriate criteria have been satisfied. Examples of criteria that might be used to determine when a wireless circuit adjustment is appropriate include criteria specifying how close a user&#39;s body may be located to a particular antenna as determined by a radio-frequency antenna signal proximity sensor, which antennas in an array are close to a user&#39;s body, how a device is being oriented, what type of applications are currently running on the device, whether the device is moving, whether an external object appears to be in the vicinity of the device as measured by a light sensor, heat sensor, infrared light or heat sensor, acoustic sensor, or capacitive sensor, etc. 
     After gathering proximity data and other suitable data using one or more of these sensors, the processing circuitry may take appropriate action. Examples of actions that may be taken include adjusting the amount of radio-frequency power that is transmitted through each antenna, switching to a desired antenna mode (e.g., switching between a mode in which multiple antennas are used to a mode in which a single antenna is used or vice versa), adjusting a phased antenna array (e.g., to steer an antenna away from the user&#39;s body), adjusting which communications bands are active, adjusting how fast data is transmitted, delaying data transmission for particular types of data, switching which communications protocol is being used, issuing an alert, prompting a user to take a particular action such as reorienting the device, etc. Proximity data may sometimes be a particularly reliable form of data to use in controlling radio-frequency emissions from wireless circuitry, but ancillary data such as data from other sensors and data on the current operation of a device may be used to increase the accuracy and appropriateness of any actions that are taken. Changes in output power and other adjustments that are being made in response to antenna-based proximity sensor data and other gathered data may be made in conjunction with changes in output power that are made in response to transmit power commands received from a cellular network. 
     Any suitable electronic devices may be provided with wireless circuitry that is controlled in this way. As an example, control techniques such as these may be used in electronic devices such as desktop computers, game consoles, routers, laptop computers, computers embedded in a computer monitor or television, computers that are part of set-top boxes or other consumer electronics equipment, relatively compact electronic devices such as portable electronic devices, etc. The use of portable electronic devices is sometimes described herein as an example. This is, however, merely illustrative. Wireless circuitry may be controlled based on proximity data and other information in any electronic device. 
     An illustrative portable electronic device in accordance with an embodiment of the present invention is shown in  FIG. 1 . Portable electronic devices such as illustrative portable electronic device  10  of  FIG. 1  may be laptop computers or small portable computers such as ultraportable computers, netbook computers, and tablet computers. Portable electronic devices may also be somewhat smaller devices. Examples of smaller portable electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, the portable electronic devices are handheld electronic devices such as cellular telephones. Other examples of handheld devices include media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, and handheld gaming devices. Handheld devices and other portable devices may, if desired, include the functionality of multiple conventional devices. Examples of multi-functional devices include cellular telephones that include media player functionality, gaming devices that include wireless communications capabilities, cellular telephones that include game and email functions, and handheld devices that receive email, support mobile telephone calls, and support web browsing. These are merely illustrative examples. Device  10  of  FIG. 1  may be any suitable portable or handheld electronic device. 
     Device  10  includes housing  12 . Housing  12 , which is sometimes referred to as a case, may be formed of any suitable materials including plastic, glass, ceramics, carbon-fiber composites and other composites, metal, other suitable materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed form light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electronic ink elements, liquid crystal display (LCD) components, or other suitable image pixel structures. A cover glass member may cover the surface of display  14 . Buttons such as button  16  may pass through openings in the cover glass. Openings may also be formed in the cover glass of display  14  to form a speaker port such as speaker port  18 . Openings in housing  12  may be used to form input-output ports, microphone ports, speaker ports, button openings, etc. 
     Wireless communications circuitry in device  10  may be used to form remote and local wireless links. One or more antennas may be used during wireless communications. Single-band and multiband antennas may be used. For example, a single-band antenna may be used to handle Bluetooth® communications at 2.4 GHz (as an example). As another example, a multiband antenna may be used to handle cellular telephone communications in multiple cellular telephone bands. Other types of communications links may also be supported using single-band and multiband antennas. 
     If desired, device  10  may use multiple antennas to support an antenna diversity scheme. With this type of arrangement, control circuitry in device  10  may monitor signal quality or sensor data to determine which antenna or antennas are performing best or are otherwise desirable to use (e.g., to satisfy regulatory limits). Based on these considerations, the control circuitry may then choose to use only a subset of the antennas or may otherwise adjust antenna use. If, for example, a sensor or a signal quality measurement determines that one of two antennas in an antenna diversity arrangement has become blocked by an external object such as part of a human body, the control circuitry may temporarily inactivate that antenna. 
     Device  10  may also use multiple antennas to implement a multiple-input-multiple-output (MIMO) communications protocol (e.g., to enhance data throughput). The control circuitry in device  10  may use proximity data or other data to control operation of the multiple antennas in the MIMO setup. For example, the control circuitry may temporarily switch from MIMO operation to a protocol that uses only a single antenna or may switch from a four-antenna MIMO scheme to a two-antenna MIMO scheme, etc. 
     Device  10  may include a phased antenna array. The array may include multiple antenna elements (i.e., multiple antennas). Control circuitry may be used to control the signals that are routed to and from the antenna elements (e.g., by controlling signal phases). The control circuitry can alter the direction in which the antenna operates. If, for example, it is desired to point the antenna in a first direction, the control circuitry can use a first group of antenna element phase settings. If it is desired to point the antenna in a second direction that is different than the first direction, the control circuitry can use a distinct second group of phase settings. Using this approach, the power of the radio-frequency signals that are emitted by the antenna array can be steered to avoid or minimize emissions into external objects (e.g., to comply with regulatory limits by avoiding radio-frequency emissions into human tissue). 
     Combinations of these approaches may also be used. For example, the control circuitry in device  10  may use proximity sensor information or other sensor data to determine the location of external objects relative to the device. The control circuitry can also ascertain what tasks are being performed by the device and what tasks are scheduled to be performed or are likely to be performed. As an example, the control circuitry can determine that a user is currently using device  10  for a telephone call or can determine that an email message has been queued up for transmission or is likely to be sent (e.g., because an email application is currently open). Using this collection of information, the control circuitry can balance the current and future needs of the user against the need to regulate emitted power. The control circuitry may take a combination of corresponding actions including switching antennas in an antenna diversity scheme, changing which wireless communications protocol (algorithm) is used, changing which wireless communications mode is used while complying with the same overall protocol, changing the settings in a beam forming phase antenna array so that emitted signals are directed towards a new location, etc. 
     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, Bluetooth® communications, etc. As an example, a lower antenna in region  20  of device  10  may be used in handling voice and data communications in one or more cellular telephone bands, whereas an upper antenna in region  22  of device  10  may provide coverage in a first band for handling Global Positioning System (GPS) signals at 1575 MHz and a second band for handling Bluetooth® and IEEE 802.11 (wireless local area network) signals at 2.4 GHz (as examples). Additional antennas may be provided to implement antenna diversity schemes, phased antenna arrays (e.g., at 60 GHz), additional bands, etc. 
     A schematic diagram of an illustrative electronic device is shown in  FIG. 2 . Device  10  of  FIG. 2  may be a portable computer such as a portable tablet computer, a mobile telephone, a mobile telephone with media player capabilities, a handheld computer, a remote control, a game player, a global positioning system (GPS) device, a combination of such devices, or any other suitable electronic device. 
     As shown in  FIG. 2 , device  10  may include storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, MIMO protocols, antenna diversity protocols, etc. 
     Input-output circuitry  30  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  such as touch screens and other user input interface are examples of input-output circuitry  32 . Input-output devices  32  may also include user input-output devices such as buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, etc. A user can control the operation of device  10  by supplying commands through such user input devices. Display and audio devices such as display  14  ( FIG. 1 ) and other components that present visual information and status data may be included in devices  32 . Display and audio components in input-output devices  32  may also include audio equipment such as speakers and other devices for creating sound. If desired, input-output devices  32  may contain audio-video interface equipment such as jacks and other connectors for external headphones and monitors. 
     Input-output devices  30  may include sensors. Data from sensors may be used to control the operation of device  10 . For example, data from sensors in device  10  may be used to control screen brightness, the orientation of information on screen  14 , the operation of wireless circuitry, etc. 
     The sensors in device  10  may include thermal sensors  41 . Thermal sensors  41  may be used to detect where and when a user is touching device  10 . For example, thermal sensors  41  may be used to monitor when a user is holding device  10  in the user&#39;s hand or may be used to monitor when device  10  is resting on the user&#39;s lap. Multiple thermal sensors  41  may be provided to determine where a user&#39;s body is contacting device  10 . There may be, for example, a thermal sensor associated with each of multiple antennas in device  10 . If a temperature rise is measured near one of the antennas, the power of that antenna may be reduced or other appropriate action may be taken. Sensors  41  may be implemented using thermocouples, bimetallic temperature sensors, solid state devices, or other suitable temperature sensors. 
     The sensors in device  10  may also include infrared heat sensors  42 . Heat sensors  42  may measure heat using thermal imaging techniques (i.e., by detecting the emitted infrared light from an object that is characteristic of the object&#39;s heat). If desired, Peltier effect coolers, heat sinks, or other devices may be used to cool infrared heat sensors  42  to reduce noise. As with thermal sensors  41 , infrared heat sensors  42  may be used to detect whether a user is touching device  10 . Infrared heat sensors  42  may, for example, be used to detect when a user is holding device  10  or is resting device  10  on the user&#39;s lap. More than one infrared heat sensor  42  may be provided. This allows device  10  to determine where an external object such as a part of a user&#39;s body is contacting device  10 . Each of the antennas in device  10  may be provided with a respective infrared heat sensor  42 . Appropriate action may be taken when heat is detected adjacent to a particular antenna. For example, the antenna may be temporarily inactivated. Infrared heat sensors  42  may be implemented using semiconductor devices or other suitable infrared heat sensor equipment. Heat sensors  42  may operate in the near-infrared band (i.e., 700 nm to 1400 nm), or may operate at longer wavelengths such as those in the short-wavelength, mid-wavelength, or long-wavelength infrared bands. 
     Motion sensors  43 , which may sometimes referred to as accelerometers, may be used to detect the earth&#39;s gravity and the relative motion of device  10 . Motion sensors  43  may therefore be used to determine how device  10  is oriented and whether device  10  is exhibiting movement characteristic of human use. For example, one or more motion sensors  43  may be used in determining whether display  14  lies in a plane parallel to the plane of the earth&#39;s surface (as when device  10  is resting flat on a table and is not adjacent to a user&#39;s body) or at a non-zero angle relative to the plane of the earth&#39;s surface. Sensors  43  can also determine whether device  10  is oriented in a landscape orientation or a portrait orientation. Movement such as periodic transitions between landscape and portrait mode or jiggling motions may be indicative of human use and can be detected using sensors  43 . 
     Capacitance sensors  44  may be integrated into a touch screen such as display  14  or may be provided as stand-alone devices. Capacitance sensors  44 , which may sometimes be referred to as touch sensors, may be used to determine when an external object such as a portion of a user&#39;s body has come into direct contact with device  10  or has come within a given threshold distance of device  10  (e.g., within 5 mm). Data gathered with capacitance sensors  44  may be used to generate proximity data (i.e., data on the proximity of external objects to device  10 ), so sensors  44  may sometimes be referred to as proximity sensors or capacitive proximity sensors. 
     Ambient light sensors  45  may be used to measure the amount of light that is illuminating device  10 . Ambient light sensors  45  may be sensitive in the visible spectrum and/or the infrared. Sensors  45  may be used to determine when a user&#39;s body is adjacent to particular portions of device  10 . For example, an ambient light sensor may be mounted on the front face of device  10  to detect when a user has placed device  10  in the vicinity of the user&#39;s head (and has thereby blocked light from reaching the ambient light sensor). Infrared light proximity sensor  46  may similarly use a light detector to determine whether an external object is in the vicinity of device  10 . Infrared light proximity sensor  46  may include an active emitter such as an infrared light emitting diode. The diode may be modulated to improve the signal-to-noise ratio of the sensor. When light from the diode is reflected back into an infrared light sensor in the infrared light proximity sensor  46 , the sensor can generate an output signal indicating that an object is in the vicinity of sensor  46 . 
     Acoustic sensors  47  may include microphones. The microphone may gather ambient noise readings that are indicative of whether device  10  is being used by a user. For example, a microphone in an acoustic sensor may be used to detect the amount of ambient noise that is present in the vicinity of device  10 . If ambient noise or certain types of ambient noise (e.g., voices) are present, device  10  can conclude that device  10  is being used by a user. Acoustic sensors  47  may also include acoustic emitters (e.g., ultrasonic transducers). This type of acoustic sensor may use echolocation techniques to measure the distance between device  10  and surrounding objects and may therefore serve as an acoustic proximity sensor. 
     Electrical sensors  48  may be used to make electrical measurements. Electrical sensors  48  may include, for example, current sensors, resistance sensors, voltage sensors, etc. Electrodes that are formed as part of electrical sensors  48  or that are electrically connected to sensors  48  may be used in making electrical measurements. As an example, a pair of electrical terminals may be located on portions of housing  12 . An electrical sensor may measure the resistance between the electrical terminals. When a user holds device  10  in the user&#39;s hand, the electrical sensor may detect a drop in resistance that is indicative of the presence of the user&#39;s hand. 
     If desired, input-output circuitry  30  may include cameras such as cameras  49 . Cameras  49  may have image sensor integrated circuits that include two-dimensional arrays of light-sensitive pixels. Image sensors in cameras  49  may have sufficient resolution for forming photographs or may have lower resolution (e.g., for gathering proximity data or other data on the environment of device  10 ). The image sensors in cameras  49  may be sensitive in the visible spectrum, in the infrared spectrum, etc. Image data that is acquired by cameras  49  may include still images and moving images (video clips). This information may be processed by a general purpose processor, a dedicated image processing circuit, or other circuitry in storage and processing circuitry  28 . 
     Cameras  49  may gather information that is used in determining whether or not a user&#39;s body or other external objects are in the vicinity of device  10 . Examples of acquired image data that may indicate that a user&#39;s body or other external object is in the vicinity of device  10  and antennas in device  10  include images containing a user&#39;s face or other identifiable body part, images containing motion, images containing flesh tones, hair, or other human attributes, image data such as video data indicating motion towards the antennas of device  10  or other portion of device  10 , dark (black) images and other images in which a camera sensor (i.e., a camera window and camera module lens) in device  10  has been obscured and therefore blocked by a human body part or other external object, etc. This information may be combined with other sensor data to enhance human body detection accuracy. 
     Sensors such as sensors  41 ,  42 ,  43 ,  44 ,  45 ,  46 ,  47 ,  48 , and  49  are merely illustrative. Other sensors may be used to gather data on the environment and operation of device  10  if desired. These sensors may serve as proximity sensors or may produce information that can be used in conjunction with proximity sensor data to enhance the accuracy of the proximity sensor data. The sensors can be provided as single stand-alone units, as groups of multiple stand-alone units, in combined structures in which the functionality of multiple sensors are combined into a single unit, etc. 
     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, 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 circuits for handling multiple radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36  and  38 . Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in cellular telephone bands such as the GSM bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz, and the 2100 MHz data band (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 global positioning system (GPS) receiver equipment such as GPS receiver circuitry  37  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data, wireless circuitry for receiving radio and television signals, paging circuits, etc. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structure, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical 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. 
     With one suitable arrangement, device  10  may have antennas in regions of device  10  such as upper region  22  and lower region  20 . One or more upper antennas for device  10  may be formed in region  22 . One or more lower antennas for device  10  may be formed in region  20 . In devices with other form factors such as laptop and tablet computers, wearable devices, computer monitors with integrated computers, etc., antennas may be located in other suitable regions (e.g., at the four corners of a rectangular device, on front and back surfaces, along edge regions of a device, in one or more arrays, etc. 
     Illustrative wireless communications circuitry that may be used in circuitry  34  of  FIG. 2  in device  10  is shown in  FIG. 3 . As shown in  FIG. 3 , wireless communications circuitry  50  may include one or more antennas such as antennas  40 . Baseband module  52  may be implemented using a single integrated circuit (e.g., a baseband processor integrated circuit) or using multiple circuits. Baseband processor  52  may receive signals to be transmitted over antennas  40  at input line  89  (e.g., from storage and processing circuitry  28 ). Baseband processor  52  may provide signals that are to be transmitted to transmitter circuitry within RF transceiver circuitry  54 . The transmitter circuitry may be coupled to power amplifier circuitry  56  via path  55 . Control signals from storage and processing circuitry  28  ( FIG. 1 ) may be used to control the power of the radio-frequency signals that the transmitter circuitry within transceiver circuitry  54  supplies to the input of power amplifier circuitry  56  via path  55 . 
     During data transmission, power amplifier circuitry  56  may boost the output power of transmitted signals to a sufficiently high level to ensure adequate signal transmission. Amplified signals may be supplied to circuitry  57  on output path  65 . Radio-frequency (RF) output stage circuitry  57  may contain radio-frequency switches and passive elements such as duplexers and diplexers. The switches in RF output stage circuitry  57  may, if desired, be used to switch circuitry  50  between a transmitting mode and a receiving mode. Duplexer and diplexer circuits and other passive components in RF output stage  57  may be used to route input and output signals based on their frequency. A connector in stage  57  may allow an external cable to be connected to device  10  for calibration. 
     Matching circuitry  60  may include a network of components such as resistors, inductors, and capacitors and ensures that antennas  40  are impedance matched to the rest of the circuitry  50 . Wireless signals that are received by antennas  40  may be passed to receiver circuitry in transceiver circuitry  54  over a path such as path  67 . A low noise amplifier in the receiver circuitry of transceiver circuits  54  may be used to amplify incoming wireless signals from path  67 . 
     Each power amplifier (e.g., each power amplifier in power amplifiers  56 ) may include one or more power amplifier stages. As an example, each power amplifier may be used to handle a separate communications band and each such power amplifier may have three series-connected power amplifier stages. Circuitry  56  and the amplifier stages in circuitry  56  may have inputs that receive control signals and power supply signals that may be adjusted to selectively turn on and off gain stages and that may be otherwise adjusted to control the output power of the radio-frequency antenna signals on path  65 . Output power can also be controlled by adjusting the power on path  55  (e.g., using transceiver circuitry  54 ). By adjusting wireless circuitry  50  in this way, the transmitted power of the radio-frequency antenna signals that pass through antennas  40  may be adjusted in real time. For example, transmitted antenna signal power may be adjusted in real time in response to the detection of the presence of a user&#39;s body or other external object in the presence of device  10  and antennas  40 . 
     Wireless circuitry  50  may include radio-frequency signal monitoring circuitry that may be used in implementing an antenna-based proximity sensor. The radio-frequency signal monitoring circuitry may measure the phase and magnitude of antenna signals associated with antennas  40 . Based on this radio-frequency signal information, storage and processing circuitry  28  ( FIG. 1 ) can determine whether the behavior of antennas  40  are being influenced by the presence of a user&#39;s body or other external object. When a user&#39;s body or other object is detected, the output power of the radio-frequency signals passing through antenna  40  can be lowered to ensure that regulatory limits are satisfied or other suitable actions may be taken. 
     Illustrative wireless circuitry  61  that may be used in implementing an antenna-based proximity sensor of this type is shown in  FIG. 4 . As shown in  FIG. 4 , wireless circuitry  61  may receive transmitted radio-frequency antenna signals on path  63  (e.g., from power amplifier circuitry  56 , output stage  57 , matching circuitry  60 , etc.). Coupler  62  may route the transmitted radio-frequency antenna signals to antenna  40 , so that these signals are transmitted over the air to a remote receiver. 
     Coupler  62  may also serve as a tap that routes a fraction of the transmitted signals from path  63  to phase and magnitude detector circuitry  64  over path  69 . Radio-frequency antenna signals that are received by coupler  62  from antenna  40  (e.g., transmitted signals that have reflected from antenna  40 ) may be routed to phase and magnitude detector circuitry  64 . Radio-frequency signal phase and magnitude detector circuitry  64  may monitor the values of the signals on paths  69  and  71  and may generate corresponding measured phase and magnitude information that is passed to signal processor  66  over path  73 . Circuitry such as circuitry  64  and  66  may be implemented using dedicated hardware, one or more general purpose processors, digital signal processing circuitry, or other suitable control circuitry (e.g., storage and processing circuitry  28  of  FIG. 1 ). 
     Antenna signal monitoring circuitry  61  may be used to monitor one, two, more than two, or all of the antennas  40  in device  10 . Using antenna signal monitoring circuitry such as circuitry  61  of  FIG. 4 , the behavior of each of antennas  40  and therefore information on the environment in which each of antennas  40  is operating may be measured in real time. This information may be used as antenna-based proximity sensor data (i.e., circuitry  61  may be used to serve as one or more proximity sensors that are sensitive to the presence of external objects in the vicinity of each of antennas  40 ). Whenever the measurements of circuitry  61  and the information of other sensors in device  10  indicate that a user&#39;s body or other external object is in the vicinity of device  10  or a particular antenna  40  in device  10  (i.e., closer than a threshold distance), device  10  may take appropriate actions. 
     Circuitry  61  may be used to make real-time antenna impedance measurements, as illustrated in connection with the Smith chart of  FIG. 5 . In the Smith chart of  FIG. 5 , antenna impedances for an illustrative one of antennas  40  are measured as a function of several different operating conditions. A fifty ohm antenna impedance is characterized by impedance point  80  in the chart of  FIG. 5 . An antenna with an impedance close to point  80  may be considered well matched to a fifty ohm transmission line in device  10 . 
     Data points for the curves of  FIG. 5  may be gathered in real time using circuitry  61 . Impedance data may be gathered while transceiver circuitry  54  is transmitting wireless data signals during normal operation (e.g., while transceiver circuitry  54  is transmitting data over a local or remote wireless communications link). In this type of arrangement, impedance measurements may be made using an in-band arrangement (e.g., measurements may be made in the communications band being used by device  10  to transmit wireless data). In addition, or as an alternative, a tunable radio-frequency source in transceiver circuits  54  may produce a probe frequency that is swept through frequencies of interest while circuitry  61  gathers phase and magnitude data that is converted to impedance data points. The probe frequency may be restricted to in-band frequencies (i.e., frequencies on segment  70 ) or may involve the use of out-of-band frequencies (i.e., frequencies elsewhere on curve  68 ). In-band and out-of-band antenna impedance measurements such as these may be made periodically, whenever normal transceiver circuitry in device  10  is quiescent, when other proximity sensors indicate that an external object might be present, when other criteria are satisfied, etc. 
     The example of  FIG. 5  illustrates how antenna impedance is influenced by the environment in which device  10  operates. In the absence of any external objects, an antenna in device  10  may, for example, be characterized by a curve such as curve  68 . Darkened line segment  70 , which extends between band edge point  72  and band edge point  74  may correspond to the antenna impedances associated with a communications band of interest. 
     If an external object such as a metal surface or a user&#39;s hand comes into contact with an antenna  40  (e.g., if device  10  is placed on a metal surface or if a user grips device  10  so that the user&#39;s hand or other body part is flush with an antenna feed portion of antenna  40 ), the impedance of antenna  40  may change. For example, the impedance of antenna  40  may be characterized by a curve such as curve  76 . Darkened line segment  78 , which extends between band edge point  77  and band edge point  79  may correspond to the antenna impedances associated with the communications band of interest under these new operating conditions. Circuitry  61  may detect the transformation of curve segment  70  into curve segment  78  on characteristic curve  76  and may therefore conclude that device  10  is in the vicinity of a metal surface or user&#39;s hand. 
     In the presence of portions of the human body or other external objects that exhibit significant losses, the impedance of the antenna may be characterized by a curve such as curve  82 . In this type of situation, curve segment  70  is transformed into a curve segment such as curve segment  85 , extending from point  86  to point  84  on curve  82 . Due to the losses produced by the external object, there may be a relatively modest number of signal reflections, resulting in a curve segment location that is relatively close to point  80 . 
     Actions that may be taken when close proximity of an external object to one or more antennas is detected may include tuning antennas in device  10 , tuning matching circuitry in device  10 , tuning antenna feeds in device  10 , etc. 
     Consider, as an example, the illustrative antenna of  FIG. 6 . Antenna  40  in the  FIG. 6  example has an inverted-F configuration. Main resonating element arm  114  is connected to ground  88  through a short circuit path such as path  132 , a feed path (see, e.g., terminals  110  and  108 ), and one or more optional paths such as the path formed by element  120  (e.g., a switch), the path formed by element  122 , and the path formed by elements  124  and  126 . Optional antenna resonating element branches such as branch  130  may be coupled to antenna  40  (e.g., by connecting branch  130  to main resonating element arm  114 ). 
     As shown in  FIG. 6 , antenna  40  may be feed from a source such as source  90  (i.e., transceiver circuitry such as transceiver circuitry  54  of  FIG. 3 ). A transmission line having paths such as positive antenna signal path  94  and ground antenna signal path  92  may be used to convey radio-frequency antenna signals from source  90  to antenna  40 . 
     Matching circuitry  60  may be interposed in the path between source  90  and antenna  40 . Matching circuitry  60  may include series-connected and shunt-connected tunable components such as tunable component  98 . Component  98  may be a tunable capacitor, a tunable inductor, a tunable resistor, a tunable component or network that includes multiple components of this type, a tunable network that includes a mixture of fixed and tunable components, etc. 
     If desired, controllable switches such as switch  100  may be used to selectively adjust circuitry  60 . Switches such as switch  100  may be radio-frequency switches that are implemented using microelectromechanical systems (MEMS) technology, using field-effect transistor devices, or other suitable switch arrangements. As illustrated in the example of  FIG. 6 , switches such as switch  100  may be used to selectively connect circuit elements such as circuit element  102  to paths  94  and  92  (i.e., in a series or shunt configuration or as part of a more complex network). Circuit element  102  may be a fixed or adjustable component such as a resistor, capacitor, inductor, etc. 
     Transmission line paths such as positive transmission line path  104  and ground transmission line path  106  may be used to interconnect matching circuitry  60  to the antenna feed of antenna  40 . The antenna feed may have a fixed or tunable configuration. In the example of  FIG. 6 , the antenna feed for antenna  40  is tunable between a first antenna feed configuration in which switch  118  has a first position and a second antenna feed configuration in which switch  118  has a second position. When switch  118  is in its first position, terminal  108  is connected to terminal  112 , so that terminal  112  serves as the positive antenna feed terminal for antenna  40 . When switch  118  is in its second position, terminal  108  is connected to terminal  116 , so that terminal  116  serves as the positive antenna feed terminal for antenna  40 . Feed terminals  112  and  116  are located at different positions along the length of main resonating element arm  114 , so the impedance and therefore the frequency response of antenna  40  can be adjusted by using switch  118  to control the feed location in antenna  40 . The arrangement of  FIG. 6  is merely illustrative. In general, antennas such as antenna  40  in device  10  may have tunable feeds formed from two or more feed points, tunable feeds that involve one, two, three, or more than three switches, non-tunable feeds, etc. 
     As shown in  FIG. 6 , antenna  40  may have a resonating element that is composed of tunable elements. This allows the size and shape of the resonating element in antenna  40  to be controlled by storage and processing circuitry  28 . In the  FIG. 6  arrangement, switch  128  may have two states (as an example). In its first state, switch  128  may be open. This electrically disconnects antenna resonating element portion  130  from antenna resonating element portion  114 . In its second state, switch  128  may be closed. When switch  128  is closed, resonating element arm portion  130  is electrically connected to arm  114 , thereby adjusting the size and shape of the antenna resonating element and adjusting the frequency response of the antenna. Additional resonating element structures may likewise be selectively connected and disconnected from the antenna resonating element in antenna  40  if desired. Circuit components (e.g., resistors, inductors, and capacitors) may be interconnected with switches such as switch  128  (e.g., for impedance matching). 
     Antenna  40  may also be adjusted by controlling components such as switch  120  and tunable component  122 . Switches such as switch  120  (e.g., a MEMs or transistor switch) may be opened and closed to tune antenna  40 . Tunable component  122  may be a tunable capacitor, tunable resistor, tunable inductor, or other suitable circuitry having a tunable impedance that can be adjusted to tune antenna  40 . In the  FIG. 6  example, tunable component  122  has been connected between antenna resonating element arm  114  and ground antenna element  88 , but this is merely illustrative. Tunable components such as component  122  may be connected in series with antenna resonating element branches such as branches  114  and  130 , may be connected in series with short circuit antenna branch  132 , may be connected in parallel with these antenna structures, or may otherwise be interconnected with the components of antenna  40 . 
     Tuning capabilities for antenna  40  may also be implemented using switches such as switch  120  and switch  124 . Switches  120  and  124  may, for example, be controlled by storage and processing circuitry  28 . When switch  124  is in its open position, component  126  may be disconnected from antenna  40 . When switch  124  is in its closed position, component  126  may be connected between resonating element arm  114  and ground  88 . Adjustable circuits such as these may be interconnected in series or parallel with any suitable antenna component (e.g., arm  130 , arm  132 , arm  114 , ground  88 , etc.). Fixed components such as capacitors, resistors, and inductors may also be included in the tuning circuitry of antenna  40 . 
     These antenna adjustment schemes may be used individually or together. For example, antenna  40  can be adjusted by adjusting a matching network that is coupled to the antenna&#39;s transmission line, by adjusting the position of the antenna feed (e.g., using switching circuitry), by adjusting antenna tuning (e.g., by using switches and/or tunable circuit components), and by adjusting the size and shape of the antenna itself (e.g., by using switches or other controllable circuit components to selectively change the size and shape of the antenna resonating element, the antenna ground, or parasitic antenna elements). If desired, only some or only one of these adjustment mechanisms may be included in antenna  40 . The arrangement of  FIG. 6  is an example. 
       FIG. 7  is a top view of an illustrative electronic device that has a rectangular outline. As shown in  FIG. 7 , antennas may be mounted in four corners of device  10 . For example, antenna  40 A may be mounted in an upper left corner, antenna  40 B may be mounted in an upper right corner, antenna  40 C may be located in a lower left corner, and antenna  40 D may be located in a lower right corner. If desired, additional antennas may be mounted in device  10  (e.g., at one or more midpoints along the edges of device  10 , at interior locations, on external antenna mounts, etc.). 
     Control circuitry  134  (e.g., storage and processing circuitry and wireless circuitry) may be used in gathering antenna signals from antennas  40 A,  40 B,  40 C, and  40 D (e.g., for implementing antenna-based proximity sensors) and may be used in controlling antennas  40 A,  40 B,  40 C, and  40 D. For example, antenna adjustments may be made to antennas  40 A,  40 B,  40 C, and  40 D using antenna control techniques of the type described in connection with  FIG. 6 . These antenna adjustments may be used to control the bandwidth of the antennas, the communications bands covered by the antennas, the impedance of the antennas, etc. Each antenna may have associated wireless circuits such as circuitry  50  of  FIG. 3 . This circuitry may be adjusted to control the output power of each antenna. For example, the power that is transmitted by antennas that are near to external objects can be reduced or these antennas can be temporarily deactivated. If, as an example, an external object is detected in the vicinity of antenna  40 B, antenna  40 B can be deactivated and one, two, or three of the remaining antennas  40 A,  40 C, and  40 D may be used. Adjustments may also be made to the type of communications scheme that is being used during data transmissions. For example, a MIMO scheme may be used that involves use of all four antennas ( 40 A,  40 B,  40 C, and  40 D) of  FIG. 7 . If an external object is detected in the vicinity of antennas  40 A,  40 B, and  40 C (as an example), use of the MIMO scheme can be halted and an alternate scheme may be used such as a multiple-input-single-output communications scheme that uses only a single antenna such as antenna  40 D to transmit signals. Combinations of these approaches may be used if desired. 
     Device  10  may include a phased antenna array such as the array shown in  FIG. 8 . As shown in  FIG. 8 , an array of antennas  40  may be coupled to a signal path such as path  140 . During signal transmission operations, path  140  may be used to supply radio-frequency antenna signals to the antenna array for transmission to external wireless equipment. During signal reception operations, path  140  may be used to route radio-frequency antenna signals that have been received by antennas  40  from external wireless equipment to receiver circuitry in device  10 . 
     The use of multiple antennas in array  40  allows beam steering arrangements to be implemented by controlling the relative phases of the signals for the antennas. In the example of  FIG. 8 , antennas  40  each have a corresponding radio-frequency phase controller  138 . There may be, for example, 3-30 (or 5-20) antennas  40  and 3-30 (or 5-20) corresponding phase control circuits  138 . 
     Control circuitry  136  may use phase controllers  138  or other suitable phase control circuitry to adjust the relative phases of the transmitted radio-frequency antenna signals that are provide to each of the antennas in the antenna array. If, for example, control circuitry  136  is adjusted to produce a first set of phases on the transmitted signals, transmitted signals  144  from antennas  40  will form a radio-frequency beam such as beam  144  that is oriented in the direction of point A. If, however, control circuitry  136  adjusts phase controllers  138  to produce a second set of phases with controllers  138 , transmitted signals  146  will form a radio-frequency beam such as beam  142  that is oriented in the direction of point B. Phase tuning can also be used steer the direction of the antenna array during signal reception operations. With one suitable arrangement, the array of antennas in  FIG. 8  may be used to handle a communications band such as a communications band at 60 GHz (as an example). Wireless communications in other frequency bands of interest may also be supported. 
     During normal operations, the settings of control circuitry  136  may be adjusted in real time to maximize signal strength (e.g., to maximize signal-to-noise ratio) or otherwise optimize performance. If, however, an external object such as a user&#39;s body is detected in the proximity of device  10 , control circuitry  136  may be used to steer the direction in which the antenna array operates so as to bypass the external object. As an example, if a proximity sensor or other sensor detects that an external object is located at point A, control circuitry  136  may be used to adjust the antenna array so that the antenna sends and receives signals along path  142  in the direction of point B. Antenna steering can be used in combination with other responses to detected objects (e.g., selective or collective transmit power reductions, communications mode adjustments, communications band adjustments, etc.). 
     Illustrative steps involved in using an electronic device in which actions may be taken in response to detected objects in the vicinity of the device and its antennas are shown in  FIG. 9 . 
     At step  148 , antenna signal monitoring circuitry such as circuitry  61  of  FIG. 4  may be used to make real time measurements of the impedance of antenna  40 . One or more of the antennas (i.e., all of the antennas) in device  10  may be monitored in this way. Phase and magnitude detector circuitry  64  can use information such as phase and magnitude information on tapped outgoing radio-frequency antenna signals and the tapped reflected radio-frequency antenna signals to determine the impedance of antenna  40 . As described in connection with the Smith chart of  FIG. 5 , the impedance of each antenna may be monitored at in-band frequencies or at out-of-band frequencies. An optional signal generator may be used to generate test signals or, if desired, signal measurements may be made using existing transmitted data signals. 
     At step  150 , storage and processing circuitry  28  ( FIG. 2 ) may be used to analyze the antenna impedance measurements from circuitry  61 . The results of this analysis may reveal, as an example, that a user&#39;s body or other external object is located in the vicinity of certain antennas in device  10 , as described in connection with  FIG. 5 . 
     At step  152 , storage and processing circuitry  28  may gather additional information on the state of device  10 . For example, storage and processing circuitry  28  may gather information on which communications bands are being used in wirelessly communicating with external equipment, may gather information on current transmit power settings, may gather sensor information from additional sensors (e.g., the sensors of  FIG. 2 ), etc. 
     At step  154 , storage and processing circuitry  28  may process the signals from the antenna-based proximity sensor (i.e., circuitry  61 ), the sensors of  FIG. 2 , and other circuitry in device  10  to determine whether antenna adjustments and other adjustments to the operation of the wireless circuitry of device  10  should be made. During the processing of step  154 , device  10  may, for example, determine, for each antenna  40 , whether an external object such as a user&#39;s body is in the vicinity of the antenna. A weighting scheme may be used to weight data from different sensors. 
     As an example, consider a device that contains three antennas and corresponding antenna-based sensors of the type shown in  FIG. 4 , light-based proximity sensor such as sensors  45 , and capacitance-based proximity sensors such as sensors  44  (as examples). The light-based and capacitance-based sensors may be located adjacent to respective antennas. Measurements from the antenna-based sensors may indicate that an external object is blocking the first antenna (i.e., these measurements may indicate that an external object is adjacent to the first antenna and is therefore within a given distance of the first antenna). The capacitance-based sensors may produce identical results, but the light-based sensor may indicate that both the first and second antennas are blocked. By analyzing data from all three sensors, device  10  can determine whether external objects are in the vicinity of each antenna and can determine a suitable course of action. 
     For example, device  10  can inhibit operation of the first and second antennas in favor of the third antenna, device  10  can turn off all three antennas, or device  10  can reduce power to the first and second antennas while continuing to operate all three antennas. Device  10  may also make adjustments to each antenna by controlling antenna matching circuitry, antenna feeds, antenna resonating elements, and antenna tuning circuits as described in connection with  FIG. 6 . In devices that contain a phased antenna array, the direction of the signal beam associated with the antenna may be steered in response to the proximity information. For example, if an external object is detected in one location, the array can be adjusted so that antenna signals are oriented in a different direction. 
     The actions that are taken at step  154  in response to processing the data that has been gathered may include adjustments to the communications band that is being used by the wireless circuitry (e.g., by shifting from a 5.0 GHz band to a 2.4 GHz band so that more appropriate antennas may be used). Device  10  may also decide to cease MIMO operation (e.g., so that a blocked antenna is not used for signal transmission or is not used for signal transmission or reception). If it is desired to reduce transmit powers, device  10  may also decide to reduce data rates to sustainable levels (i.e., levels that are appropriate to the amount of signal strength that is available). 
     If desired, the operations of steps  148 ,  150 ,  152 , and  154  may be implemented in a device without extensive redundant antenna resources. For example, a device may have only one cellular telephone antenna. Circuitry  61  of  FIG. 4  may be used to monitor the impedance of the antenna in real time. Device  10  may reduce the output power of the antenna when impedance measurements of the type described in connection with  FIG. 7  reveal that an external object is partly or completely blocking the antenna. 
     In general, any suitable information may be used in determining what actions are appropriate when adjusting the antennas. For example, information from the sensors of  FIG. 2 , from application software, from circuitry  61  of  FIG. 4 , and other information may be processed by device  10  to determine whether an external object is adjacent to the antenna (e.g., whether an external object is within the vicinity of the antenna by virtue of being within a given threshold distance of the antenna). In response, device  10  may reduce or otherwise adjust antenna powers and other antenna circuit attributes, may control communications modes, may control communications bands, antenna phases, etc. As indicated by line  156  in  FIG. 9 , these operations may be repeated (e.g., continuously) during operation of device  10 . 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20150518
Publication Date: 20151103
Grant Date: 20151103
Priority Date: 20100413
Inventors: SCHLUB ROBERT W.
CABALLERO RUBEN
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W4/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W8/22", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W8/22", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/401", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W8/22", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W4/12", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 44025294