PATENT DOCUMENT

Publication Number: US-8818450-B2
Application Number: US-201313777955-A
Country: US
Kind Code: B2

Title: Electronic device with proximity-based radio power control

Abstract:
An electronic device such as a portable electronic device may have an antenna and associated wireless communications circuitry. A sensor such as a proximity sensor may be used to detect when the electronic device is in close proximity to a user&#39;s head. Control circuitry within the electronic device may be used to adjust radio-frequency signal transmit power levels. When it is determined that the electronic device is within a given distance from the user&#39;s head, the radio-frequency signal transmit power level may be reduced. When it is determined that the electronic device is not within the given distance from the user&#39;s head, proximity-based limits on the radio-frequency signal transmit power level may be removed. Data may be gathered from a touch sensor, accelerometer, ambient light sensor and other sources for use in determining how to adjust the transmit power level.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a capacitive proximity sensor that detects when objects are present within a given distance of the electronic device; 
 a radio-frequency antenna with which radio-frequency signals are transmitted with a transmit power; and 
 circuitry that adjusts the transmit power based at least partly on data from the capacitive proximity sensor, wherein the circuitry comprise transmitter circuitry that handles radio-frequency wireless transmissions in at least a first wireless communications band and a second wireless communications band and wherein the circuitry is configured to make radio-frequency wireless transmit power adjustments in the first wireless communications band at least partly based on changes that occur in radio-frequency wireless transmit power levels in the second wireless communications band. 
 
     
     
       2. A handheld electronic device operated by a user, comprising:
 an antenna with which radio-frequency signals are transmitted at a given transmit power; 
 a first sensor that generates sensor data, wherein the first sensor comprises an accelerometer; 
 a second sensor, wherein the second sensor generates proximity data indicative of whether at least part of the user is present within a given distance from the handheld electronic device; and 
 control circuitry that controls the transmit power based at least partly on the sensor data and the proximity data, wherein the control circuitry establishes a transmit power ceiling for the radio-frequency signals based on the proximity data, wherein the control circuitry is configured to inhibit adjustments to the transmit power based on the sensor data in response to determining that the user is present within the given distance. 
 
     
     
       3. The handheld electronic device defined in  claim 2  further comprising:
 a proximity sensor having a light source and a photodetector, wherein the control circuitry controls the transmit power by processing the sensor data, the proximity data, and information from the proximity sensor in parallel. 
 
     
     
       4. A method of operating a handheld electronic device, the method comprising:
 with an antenna, transmitting radio-frequency signals at a transmit power; 
 with a capacitive proximity sensor, determining whether a user is within a given distance from the handheld electronic device; 
 with control circuitry, adjusting the transmit power in response to determining that the user is within the given distance from the handheld electronic device; 
 with the control circuitry, establishing a transmit power ceiling in response to determining that the user is within the given distance from the handheld electronic device; 
 with an additional sensor, producing sensor data; 
 with the control circuitry, adjusting the transmit power based on the sensor data from the additional sensor, wherein the adjustments to the transmit power based on the sensor data from the additional sensor includes adjustments requiring an increased transmit power that exceeds the transmit power ceiling; and 
 with the control circuitry, preventing the adjustments to the transmit power based on the sensor data from the additional sensor that require the increased transmit power that exceeds the transmit power ceiling. 
 
     
     
       5. The method defined in  claim 4  wherein the additional sensor comprises an accelerometer and wherein producing the sensor data comprises:
 with the accelerometer, producing accelerometer data. 
 
     
     
       6. The method defined in  claim 4  further comprising:
 with the control circuitry, determining whether the electronic device is operating in a first communications mode or a second communications mode; 
 with the control circuitry, allowing adjustments to the transmit power to exceed the transmit power ceiling in response to determining that the electronic device is operating in the first communications mode; and 
 with the control circuitry, ensuring that the transmit power is maintained below the transmit power ceiling in response to determining that the electronic device is operating in the second communications mode. 
 
     
     
       7. The method defined in  claim 6  wherein the first communications mode comprises a 2G cellular communications mode and wherein the second communications mode comprises a 3G cellular communications mode. 
     
     
       8. The method defined in  claim 6  further comprising:
 wherein the electronic device wirelessly communicates using time division multiplexing in the first communications mode and wherein the electronic device does not wirelessly communicate using time division multiplexing in the second communications mode.

Description:
This application claims the benefit of provisional patent application No. 61/059,247, filed Jun. 5, 2008, and U.S. patent application Ser. No. 12/207,326 filed Sep. 9, 2008, which are hereby incorporated by reference herein in their entirety. 
     BACKGROUND 
     This invention relates generally to electronic devices, and more particularly, to power control techniques for radio-frequency circuitry in electronic devices. 
     Electronic devices such as handheld electronic devices and other portable electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type. Popular portable electronic devices that are somewhat larger than traditional handheld electronic devices include laptop computers and tablet computers. 
     Due in part to their mobile nature, portable electronic devices are often provided with wireless communications capabilities. For example, handheld electronic devices may use long-range wireless communications to communicate with wireless base stations. Cellular telephones and other devices with cellular capabilities may communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz. Portable electronic devices may also use short-range wireless communications links. For example, portable electronic devices may communicate using the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz and the Bluetooth® band at 2.4 GHz. Data communications are also possible at 2100 MHz. 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to reduce the size of components that are used in these devices while providing enhanced functionality. It is generally impractical to completely shield a user of a compact handheld device from transmitted radio-frequency signals. For example, conventional cellular telephone handsets generally emit signals in the vicinity of a user&#39;s head during telephone calls. Government regulations limit radio-frequency signal powers. In particular, so-called specific absorption rate (SAR) standards are in place that impose maximum energy absorption limits on handset manufacturers. At the same time, wireless carriers require that the handsets that are used in their networks be capable of producing certain minimum radio-frequency powers so as to ensure satisfactory operation of the handsets. 
     The manufacturers of electronic devices such as wireless handheld devices therefore face challenges in producing devices with adequate radio-frequency signal strengths that are compliant with applicable government regulations. 
     It would therefore be desirable to be able to provide electronic devices with improved wireless capabilities. 
     SUMMARY 
     An electronic device such as a handheld electronic device or other portable electronic device may be provided that has wireless communications capabilities. An antenna may be used to transmit and receive radio-frequency signals. The signals may be associated with cellular telephone communications bands. 
     A proximity sensor may be provided in the device. The proximity sensor may include a light source such as a light-emitting diode and a photodetector. During operation of the device, the light source emits light. If an object such as the head of a user is within a given distance of the electronic device, the emitted light will be reflected back to the electronic device and will be detected by the photodetector. This allows the electronic device to determine whether the electronic device is in close proximity to the user&#39;s head. 
     Information on whether the electronic device is close to the user&#39;s head may also be gathered using data from other sources. For example, the electronic device may have a touch screen with a touch sensor or may have other touch sensitive components. Signals from these touch sensors may be used to help determine whether the electronic device is adjacent to the user&#39;s head. The electronic device may also have sensors such as an ambient light sensor and an accelerometer. The ambient light sensor may detect when a shadow passes over the front face of the device, which may be indicative of a close distance between the electronic device and an external object. The accelerometer may produce data that is indicative of the current orientation of the electronic device relative to the ground and data that is indicative of whether the device is in motion or at rest. In situations in which the device is being held in an orientation in which one of the edges of the device faces the ground and in which the device is in motion, the electronic device can conclude that the electronic device is in close proximity to the user&#39;s head. 
     The electronic device may have an adjustable radio-frequency power amplifier. The device may adjust the output power from the radio-frequency power amplifier to control the power level of transmitted cellular telephone signals. If it is determined that the electronic device is close to the user&#39;s head, the maximum allowable transmit power level may be limited. If it is determined that the electronic device is not in close proximity to the user&#39;s head, the radio-frequency transmit power of the device need not be limited. 
     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 portable electronic device in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative portable electronic device in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of an illustrative electronic device showing how sensors may be used to detect when the electronic device is in the vicinity of an object such as a human body part in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of illustrative circuitry that may be used in an electronic device such as a wireless portable electronic device with output power control capabilities in accordance with an embodiment of the present invention. 
         FIG. 5  is a flow chart of illustrative steps involved in controlling transmitted radio-frequency power in a wireless electronic device in accordance with an embodiment of the present invention. 
         FIG. 6  is a graph showing how transmitted radio-frequency signal power can be controlled as a function of time in response to network control commands and locally established power limits based on data such as proximity sensor data in accordance with an embodiment of the present invention. 
         FIG. 7  is a flow chart of illustrative steps involved in gathering and analyzing data in a wireless electronic device to determine appropriate radio-frequency signal power settings for transmitted signals in accordance with an embodiment of the present invention. 
         FIG. 8  is a flow chart of illustrative steps involved in gathering and analyzing data in a wireless electronic device to determine appropriate radio-frequency signal power settings for transmitted signals in scenarios in which one or more communications bands are being used in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to electronic devices, and more particularly, to managing transmitted radio-frequency power levels in portable electronic devices such as handheld electronic devices. 
     The electronic devices may be portable electronic devices such as laptop computers or small portable computers of the type that are sometimes referred to as ultraportables. 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 may be wireless electronic devices. 
     The wireless electronic devices may be, for example, handheld wireless devices such as cellular telephones, 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. The wireless electronic devices may also be hybrid devices that combine the functionality of multiple conventional devices. Examples of hybrid portable electronic devices include a cellular telephone that includes media player functionality, a gaming device that includes a wireless communications capability, a cellular telephone that includes game and email functions, and a portable device that receives email, supports mobile telephone calls, has music player functionality and supports web browsing. These are merely illustrative examples. 
     An illustrative portable electronic device in accordance with an embodiment of the present invention is shown in  FIG. 1 . Device  10  of  FIG. 1  may be, for example, a handheld electronic device that supports 2G and/or 3G cellular telephone and data functions, global positioning system capabilities, and local wireless communications capabilities (e.g., IEEE 802.11 and Bluetooth®) and that supports handheld computing device functions such as internet browsing, email and calendar functions, games, music player functionality, etc. 
     Device  10  may have housing  12 . Antennas for handling wireless communications may be housed within housing  12  (as an example). 
     Housing  12 , which is sometimes referred to as a case, may be formed of any suitable materials including, plastic, glass, ceramics, metal, or other suitable materials, or a combination of these materials. In some situations, housing  12  or portions of housing  12  may be formed from a dielectric or other low-conductivity material, so that the operation of conductive antenna elements that are located in proximity to housing  12  is not disrupted. Housing  12  or portions of housing  12  may also be formed from conductive materials such as metal. An advantage of forming housing  12  from a dielectric material such as plastic is that this may help to reduce the overall weight of device  10 . 
     In scenarios in which housing  12  is formed from metal elements, one or more of the metal elements may be used as part of the antennas in device  10 . For example, metal portions of housing  12  may be shorted to an internal ground plane in device  10  to create a larger ground plane element for that device  10 . Housing  12  may have a bezel such as bezel  14  that surrounds display  16 . Bezel  14  may be formed from a conductive material or other suitable material and may be used as part of the antennas in device  10 . For example, bezel  14  may be shorted to printed circuit board conductors or other internal ground plane structures in device  10  to form part of an antenna ground plane. 
     Display  16  may be a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, or any other suitable display. The outermost surface of display  16  may be formed from one or more plastic or glass layers. If desired, touch screen functionality may be integrated into display  16  or may be provided using a separate touch pad device. An advantage of integrating a touch screen into display  16  to make display  16  touch sensitive is that this type of arrangement can save space and reduce visual clutter. Touch screen displays such as display  16  may be formed from capacitive touch sensors or any other suitable touch sensors (e.g., resistive touch sensors, touch sensors based on light or sound waves, etc.). An advantage of capacitive touch sensors is that they may be used to sense the presence of an object even when the object is not in direct contact with display  16 . 
     Display screen  16  (e.g., a touch screen) is merely one example of an input-output device that may be used with electronic device  10 . If desired, electronic device  10  may have other input-output devices. For example, electronic device  10  may have user input control devices such as button  19 , and input-output components such as port  20  and one or more input-output jacks (e.g., for audio and/or video). Button  19  may be, for example, a menu button. Port  20  may contain a 30-pin data connector (as an example). Openings  22  and  24  may, if desired, form speaker and microphone ports. Speaker port  22  may be used when operating device  10  in speakerphone mode. Opening  23  may also form a speaker port. For example, speaker port  23  may serve as a telephone receiver that is placed adjacent to a user&#39;s ear during operation. In the example of  FIG. 1 , display screen  16  is shown as being mounted on the front face of handheld electronic device  10 , but display screen  16  may, if desired, be mounted on the rear face of handheld electronic device  10 , on a side of device  10 , on a flip-up portion of device  10  that is attached to a main body portion of device  10  by a hinge (for example), or using any other suitable mounting arrangement. 
     A user of electronic device  10  may supply input commands using user input interface devices such as button  19  and touch screen  16 . Suitable user input interface devices for electronic device  10  include buttons (e.g., alphanumeric keys, power on-off, power-on, power-off, and other specialized buttons, etc.), a touch pad, pointing stick, or other cursor control device, a microphone for supplying voice commands, or any other suitable interface for controlling device  10 . Although shown schematically as being formed on the top face of electronic device  10  in the example of  FIG. 1 , buttons such as button  19  and other user input interface devices may generally be formed on any suitable portion of electronic device  10 . For example, a button such as button  19  or other user interface control may be formed on the side of electronic device  10 . Buttons and other user interface controls can also be located on the top face, rear face, or other portion of device  10 . If desired, device  10  can be controlled remotely (e.g., using an infrared remote control, a radio-frequency remote control such as a Bluetooth® remote control, etc.). 
     Device  10  may contain sensors that provide information about the environment and condition of device  10 . For example, device  10  may contain a proximity sensor such as sensor  25  and an ambient light sensor such as ambient light sensor  27 . 
     Proximity sensor  25  may include, for example, a light-emitting diode (LED) and an associated photodetector such as a photodiode. The light-emitting diode may be an infrared light-emitting diode (as an example). Reflected light from nearby objects may be detected using the photodiode. When sufficient reflected light is detected, it can be concluded that a human body part (e.g., a head, finger, or hand) or other object is located close to sensor  25 . When insufficient reflected light is detected, it can be concluded that no objects are located near to sensor  25 . If desired, emitted light from sensor  25  may be concentrated at a particular distance from sensor  25  using a lens or other focusing structure. This may help to enhance the strength of reflected signals from objects located at this particular distance (e.g., objects located at 0.5 to 10 cm away from the planar front surface of display  16 ). 
     The light-emitting diode in the proximity sensor may be modulated at a particular frequency or may be modulated using any other suitable modulation pattern. The use of a modulation pattern to drive the light-emitting diode may help to discriminate reflected light-emitting diode signals from background illumination. This may increase the signal-to-noise ratio of the proximity sensor. If desired, proximity sensor  25  may be based on proximity detection arrangements other than light-emitting diode arrangements. For example, a proximity sensor for device  10  may be based on a capacitive sensor, a photodetector that works only with ambient light (and not emitted light from device  10 ), an acoustic proximity sensor (e.g., a sensor that uses ultrasonic sound waves to determine the presence or absence of a nearby object), a sensor that detects reflected electromagnetic radiation (e.g., radio-frequency radiation), or any other suitable sensor capable of detecting the presence of a nearby object. 
     Ambient light sensor  27  may be used to detect the level of ambient illumination around device  10 . Ambient light sensor  27  may be implemented using a photodiode that is sensitive to visible light. Separate photodiodes are typically used for proximity sensor  25  and ambient light sensor  27 , but the photodiode functionality of ambient light sensor  27  and the photodiode functionality of proximity sensor  25  (in a light-based proximity detector) may be implemented using a common photodiode if desired. Information on the amount of light that is gathered by ambient light sensor  27  may be used to adjust the screen brightness of display  16  (as an example). 
     If desired, proximity sensor functionality may be implemented in device  10  using a device that serves multiple functions. As an example, a capacitive touch sensor or other such touch sensor that is part of a touch display  16  may be used in detecting the presence of a nearby object. During normal operation, touch sensor output signals may be used to identify user input selections as a user presses a finger against various portions of screen  16 . When used as a proximity sensor, the output signals of the touch screen may be processed to determine whether or not an object is adjacent to device  10 . With this type of arrangement, the capacitive readings obtained from the touch sensor portion of display  16  may be processed, for example, to determine whether a user has placed device  10  next to the user&#39;s head. Because the presence of the user&#39;s head in the vicinity of screen  16  will change the capacitive reading (or other such touch sensor reading) from the display, the presence of the user&#39;s head can be detected without using a conventional proximity sensor. As another example, light readings from an ambient light sensor may be used as an indicator of the proximity of an object to device  10  (e.g., by detecting shadows that indicate the presence of an object). Touch pads without displays may also be used to produce proximity data. 
     To improve accuracy, signals from multiple proximity sensor devices (e.g., an LED-based proximity sensor, an ambient light sensor used to detect proximity, a capacitive touch screen, etc.) may be processed in parallel. With this type of arrangement, device  10  can more accurately determine whether or not device  10  has been placed in close proximity to an object. 
     The locations for proximity sensor  25  and ambient light sensor  27  of  FIG. 1  are merely illustrative. Sensors such as these may be placed at any suitable location on device  10 . When a location such as the location shown in  FIG. 1  is used, sensors  25  and  27  obtain information on whether the upper end of device  10  has been placed adjacent to a user&#39;s ear and head. This type of configuration arises when a user is using device  10  for a cellular telephone call. When using device  10  to make a telephone call, receiver  23  is placed immediately adjacent to the user&#39;s ear, whereas microphone port  24  is placed close to the user&#39;s mouth. If desired, sensors such as proximity sensor  25  and/or ambient light sensor  25  may be located at the lower (microphone) end of device  10 . For example, proximity sensor  25  may be placed adjacent to menu button  19  to help sense when microphone  24  is adjacent to the user&#39;s face. 
     Components such as display  16  and other user input interface devices may cover most of the available surface area on the front face of device  10  (as shown in the example of  FIG. 1 ) or may occupy only a small portion of the front face of device  10 . Because electronic components such as display  16  often contain large amounts of metal (e.g., as radio-frequency shielding), the location of these components relative to the antenna elements in device  10  should generally be taken into consideration. Suitably chosen locations for the antenna elements and electronic components of the device will allow the antennas of electronic device  10  to function properly without being disrupted by the electronic components. 
     Examples of locations in which antenna structures may be located in device  10  include region  18  and region  21 . These are merely illustrative examples. Any suitable portion of device  10  may be used to house antenna structures for device  10  if desired. 
     Any suitable antenna structures may be used in device  10 . For example, device  10  may have one antenna or may have multiple antennas. The antennas in device  10  may each be used to cover a single communications band or each antenna may cover multiple communications bands. If desired, one or more antennas may cover a single band while one or more additional antennas are each used to cover multiple bands. 
     In arrangements in which antennas are needed to support communications at more than one band, the antennas may have shapes that support multi-band operations. For example, an antenna may have a resonating element with arms of various different lengths and/or a ground plane with slots of various different sizes that resonate in desired radio-frequency bands. Inverted-F antenna elements, planar inverted-F antenna elements or other antenna structures may be used in the presence of an antenna slot to form a hybrid slot/non-slot antenna. 
     Antennas (e.g., hybrid slot/non-slot antennas or other suitable antennas) may be used at one end or both ends of device  10 . For example, one such antenna may be used as a dual band antenna (e.g., in region  21 ) and one such antenna may be used as a pentaband antenna (e.g., in region  18 ). 
     When an antenna in region  18  is used as a cellular telephone antenna (e.g., for 2G and/or 3G voice and data communications), the antenna will be located at the same end of device  10  as microphone port  24 . When device  10  is being held close to the user&#39;s head and microphone  24  is being used to conduct a telephone call, the antenna in region  18  will be near to the user&#39;s head and will therefore be likely to emit radio-frequency signals near the user&#39;s head. Proximity detector  25  and other sensors may be used in detecting the presence of the user&#39;s head or other nearby object. To ensure that regulatory limits on radio-frequency emissions in the vicinity of the user&#39;s head are satisfied, device  10  may reduce the maximum allowable transmitted radio-frequency signal power that is handled by the antenna in region  18  whenever it is determined that device  10  is in the vicinity of the user&#39;s head (i.e., whenever proximity detector  25  and/or other sensors determine that an object is within a few centimeters or other suitable distance from the front face of device  10 ). 
     A schematic diagram of an embodiment of an illustrative portable electronic device such as a handheld electronic device is shown in  FIG. 2 . Portable device  10  may be 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 laptop computer, a tablet computer, an ultraportable computer, a hybrid device that includes the functionality of some or all of these devices, or any other suitable portable electronic device. 
     As shown in  FIG. 2 , device  10  may include storage  34 . Storage  34  may include one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., battery-based static or dynamic random-access-memory), etc. 
     Processing circuitry  36  may be used to control the operation of device  10 . Processing circuitry  36  may be based on a processor such as a microprocessor and other suitable integrated circuits. With one suitable arrangement, processing circuitry  36  and storage  34  are 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. Processing circuitry  36  and storage  34  may be used in implementing suitable communications protocols. Communications protocols that may be implemented using processing circuitry  36  and storage  34  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, protocols for handling 3 G communications services (e.g., using wide band code division multiple access techniques), 2G cellular telephone communications protocols, etc. 
     Input-output devices  38  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. Display screen  16 , button  19 , microphone port  24 , speaker port  22 , and dock connector port  20  are examples of input-output devices  38 . 
     Input-output devices  38  may include sensors  41 . Sensors  41  may include proximity sensors such as proximity sensor  25  of  FIG. 1 , ambient light sensors such as ambient light sensor  27 , accelerometers (e.g., to determine the orientation of device  10  in real time), sensors formed by utilizing the capabilities of devices such as touch screen  16  or other multipurpose components in device  10 , acoustic sensors, electromagnetic sensors, or any other suitable sensors. 
     Input-output devices  38  can also include user input-output devices  40  such as buttons, touch screens, 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 user input devices  40 . Display and audio devices  42  may include liquid-crystal display (LCD) screens or other screens, light-emitting diodes (LEDs), and other components that present visual information and status data. Display and audio devices  42  may also include audio equipment such as speakers and other devices for creating sound. Display and audio devices  42  may contain audio-video interface equipment such as jacks and other connectors for external headphones and monitors. 
     Wireless communications devices  44  may include communications circuitry such as radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, passive RF components, antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Device  10  can communicate with external devices such as accessories  46 , computing equipment  48 , and wireless network  49  as shown by paths  50  and  51 . Paths  50  may include wired and wireless paths. Path  51  may be a wireless path. Accessories  46  may include headphones (e.g., a wireless cellular headset or audio headphones) and audio-video equipment (e.g., wireless speakers, a game controller, or other equipment that receives and plays audio and video content), a peripheral such as a wireless printer or camera, etc. 
     Computing equipment  48  may be any suitable computer. With one suitable arrangement, computing equipment  48  is a computer that has an associated wireless access point (router) or an internal or external wireless card that establishes a wireless connection with device  10 . The computer may be a server (e.g., an internet server), a local area network computer with or without internet access, a user&#39;s own personal computer, a peer device (e.g., another portable electronic device  10 ), or any other suitable computing equipment. 
     Wireless network  49  may include any suitable network equipment, such as cellular telephone base stations, cellular towers, wireless data networks, computers associated with wireless networks, etc. For example, wireless network  49  may include network management equipment that monitors the wireless signal strength of the wireless handsets (cellular telephones, handheld computing devices, etc.) that are in communication with network  49 . 
     To improve the overall performance of the network and to ensure that interference between handsets is minimized, the network management equipment may send power adjustment commands (sometimes referred to as transmit power control commands) to each handset. The transmit power control settings that are provided to the handsets direct handsets with weak signals to increase their transmit powers, so that their signals will be properly received by the network. At the same time, the transmit power control settings may instruct handsets whose signals are being received clearly at high power to reduce their transmit power control settings. This reduces interference between handsets and allows the network to maximize its use of available wireless bandwidth. 
     When devices such as device  10  receive transmit power control settings from the network, each device  10  may make suitable transmission power adjustments. For example, a device  10  may adjust the gain of the radio-frequency power amplifier circuitry that is used to amplify the radio-frequency signals that are being transmitted by device  10  to a higher level to increase the power of the transmitted radio-frequency signals or to a lower level to decrease the power of the transmitted radio-frequency signals. 
     The antenna structures and wireless communications devices of device  10  may support communications over any suitable wireless communications bands. For example, wireless communications devices  44  may be used to cover communications frequency bands such as cellular telephone voice and data bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz (as examples). Devices  44  may also be used to handle the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz (also sometimes referred to as wireless local area network or WLAN bands), the Bluetooth® band at 2.4 GHz, and the global positioning system (GPS) band at 1575 MHz. 
     Device  10  can cover these communications bands and/or other suitable communications bands using the antenna structures in wireless communications circuitry  44 . As an example, a pentaband cellular telephone antenna may be provided at one end of device  10  (e.g., in region  18 ) to handle 2G and 3G voice and data signals and a dual band antenna may be provided at another end of device  10  (e.g., in region  21 ) to handle GPS and 2.4 GHz signals. The pentaband antenna may be used to cover wireless bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz (as an example). The dual band antenna may be used to handle 1575 MHz signals for GPS operations and 2.4 GHz signals (for Bluetooth® and IEEE 802.11 operations). These are merely illustrative arrangements. Any suitable antenna structures may be used in device  10  if desired. 
     Regulatory compliance can be ensured by reducing the maximum allowable transmitted radio-frequency signal power from device  10  when device  10  is in the vicinity of a user&#39;s head or other body part. As shown in  FIG. 3 , a typical system environment such as environment  80  includes device  10  and an object such as object  60 . Object  60  may be an inanimate object or, more significantly, may be part of the user&#39;s body such as a user&#39;s head. The energy density associated with radio-frequency emissions from device  10  is generally negligible for IEEE 802.11 and Bluetooth® transmissions (e.g., transmissions that may be associated with antenna  62 ). The process of receiving and processing GPS signals also generally results in radio-frequency emissions of negligible energy densities. 
     In contrast, cellular telephone transmissions (e.g., transmissions that may be associated with antenna  64 ) may have nonnegligible energy densities. This is particularly true for 3G wireless transmissions, which use code-division multiple access (CDMA) coding schemes, rather than the time-division multiplexing (TDM) schemes associated with 2G GSM cellular telephone transmissions. Compliance with regulations that place upper limits on the amount of radio-frequency signal power that may be absorbed by a user&#39;s head can be ensured by reducing the power of the radio-frequency signal transmissions associated with antenna  64  (e.g., cellular telephone transmissions) whenever it is determined that device  10  is adjacent to the user&#39;s head. 
     As shown in  FIG. 3 , device  10  may have control circuitry  72  (e.g., processing circuitry  36 , storage  34 , and other circuitry from  FIG. 2 ). Control circuitry  72  may process sensor signals to detect object  60 . 
     Sensors that may be used to detect the presence of object  60  in the vicinity of device  10  may include proximity sensor  25 . Proximity sensor  25  may include a light-emitting element such as a laser or light-emitting diode. Proximity sensor  25  may also have a light-detecting element. In the example of  FIG. 3 , proximity sensor  25  has light-emitting diode  25 A and a light detecting element such as photodiode  25 B. Sensor  25  may use light in any suitable frequency range. For example, sensor  25  may use infrared light. Light  74  that is emitted by diode  25 A may be reflected from object  60 . Reflected light  76  may be detected by detector (sensor)  25 B. If desired, diode  25 A may be driven with a modulated signal so that light  74  is modulated. For example, light  74  may be modulated at a particular frequency. Using a bandpass filter centered at the modulation frequency or other suitable filtering arrangement, the signals from sensor  25 B may be filtered by control circuitry  72  to subtract background noise (as an example). Techniques such as these may be used to increase the signal-to-noise ratio of the measurement signals produced by proximity detector  25 . 
     Another sensor that may be used in device  10  when detecting the presence of object  60  is ambient light sensor  68 . Ambient light sensor  68  may be a photodiode or other light sensor that is capable of detecting incoming light  78 . Ambient light sensor  68  may, for example, operate in the visible spectrum and/or in the infrared spectrum. Because more light  78  will generally be received by sensor  68  when sensor  68  is not blocked by the presence of object  60  than when object  60  is present and is casting a shadow on sensor  68 , sensor  68  may be used to generate proximity data. This data may be used alone or in conjunction with proximity data from other sensors in assisting device  10  in determining whether or not object  60  is present. 
     Touch screen  16  may be located on the front face of device  10  (i.e., the side of device  10  that is shown as facing object  60  in the example of  FIG. 3 ). As shown in  FIG. 3 , Touch sensor  16 , may be a capacitive touch sensor having associated capacitances such as capacitance  66 . The magnitude of this capacitance (and inputs from the other sensors in  FIG. 3 ) may be monitored by control circuitry  72 . When object  60  is present in the vicinity of touch screen  16 , the magnitude of capacitance  66  will be affected, which allows control circuitry  72  and device  10  to conclude that object  60  is adjacent to device  10  as shown in  FIG. 3 . 
     The detection range of proximity detector  25  and the other sensors in device  10  is typically in the millimeter to centimeter range. Objects closer than the maximum detection distance will be sensed as being in the vicinity of device  10 . Objects outside of the detection range will not be considered to be in the vicinity of device  10 . If desired, other detection ranges may be used (e.g., detection ranges on the order of tens of centimeters). More typically, however, detection of the presence of object  60  only when object  60  is closer than several centimeters from device  10  is preferred, as this addresses the primary situation in which the energy density of radio-frequency emissions from antenna  64  is of concern. 
     If desired, sensors such as accelerometer  70  may be used in conjunction with other sensors to help determine when to adjust the power level associated with transmitted radio-frequency signals in device  10 . Accelerometer  70  may be used by control circuitry  72  to determine the orientation of device  10  relative to the ground. For example, accelerometer  70  may be used to determine whether device  10  is being held by a user so that one of its left or right edges is facing downwards (as when making a telephone call) or whether device  10  is resting horizontally on a table top. If it is determined that device  10  is horizontal and stationary, it may be concluded that it is impossible or at least unlikely that device  10  is being held in the vicinity of the user&#39;s head. This information may be used to help ascertain whether the readings obtained from the other sensors in device  10  are accurate. 
     During operation of device  10 , control circuitry  72  may be aware of the types of radio-frequency signals that are being transmitted. For example, control circuitry  72  might determine that low-power radio-frequency signals are being transmitted over antenna  62  and that antenna  64  is not being used. Control circuitry  72  might also determine when antenna  64  is being used for 2 G communications (and is therefore associated with relatively lower emission levels when averaged over time) and when antenna  64  is being used for 3 G communications (and is therefore associated with relatively larger time-averaged emissions because no time division multiplexing is being used). Control circuitry  72  can use operational information such as this in determining how to adjust the transmitted radio-frequency power from antenna  64 , while at the same time making power adjustment decisions based on the readings of one or more sensors (e.g., to determine whether object  60  is in close proximity to device  10 ). As an example, if it is determined that 2G signals are being transmitted, control circuitry  72  can decide to make no transmit power reductions regardless of the readings of proximity sensor  25 , whereas control circuitry  72  can make transmit power reductions when it is determined that 3G signals are being transmitted. 
     An illustrative control arrangement that may be used in controlling transmitted radio-frequency signal powers is shown in  FIG. 4 . As shown in  FIG. 4 , control circuitry  72  may include one or more integrated circuits such as a microprocessor (sometimes referred to as an application processor), a baseband module, power management chips, memory, codecs, etc. Transceiver circuitry  84  may be used in producing radio-frequency output signals based on data received from the application processor. Circuitry such as circuitry  84  may, if desired, be integrated into one or more of the integrated circuits in control circuitry  72 . 
     Radio-frequency signals that are to be transmitted by device  10  are generally amplified using radio-frequency amplifier circuitry. The radio-frequency amplifier circuitry may be implemented using one or more gain stages in one or more integrated circuits. In the example of  FIG. 4 , signals are shown as being amplified by radio-frequency power amplifier  86 . If desired, there may be multiple power amplifiers such as amplifier  86  each of which is associated with a different communications band or set of communications bands. A single power amplifier symbol is shown in the schematic diagram of  FIG. 4  to avoid over-complicating the drawing. 
     Power amplifier circuitry  86  may be used to amplify radio-frequency signals prior to transmission over antenna  64 . The gain of power amplifier circuitry  86  may be adjusted using a control path such as control path  90 . Control path  90  may be used to handle analog and/or digital control signals. The gain of power amplifier  86  may, for example, be controlled by adjusting the magnitude of an analog control voltage or analog power supply voltage. The gain of power amplifier  86  may also be adjusted by turning on and off certain gain stages in power amplifier  86 . If desired, digital control signals may be processed by power amplifier  86  and used in controlling the gain setting. Combinations of these approaches or other suitable power amplifier gain adjustments techniques may be used if desired. 
     The gain of power amplifier  86  may be adjusted to ensure that the strength of the radio-frequency signals that are being transmitted through antenna  64  is sufficient for satisfactory wireless communications, while not exceeding regulatory limits. Either an open loop or closed loop control scheme may be used when controlling the operation of power amplifier  86 . 
     In an open loop scheme, coupler  88  need not be used and the gain of power amplifier  86  may be adjusted by providing control signals to power amplifier  86  over control path  90  without feedback from the output path. 
     In a closed loop scheme of the type shown in  FIG. 4 , feedback is obtained from the output path. With one suitable arrangement, a radio-frequency coupler such as coupler  88  is interposed between the output of power amplifier  86  and antenna  64 . Coupler  88  may allow most of the power from amplifier  86  to pass to antenna  64 . A small fraction (typically less than a few percent) of the output power may be diverted by coupler  88  onto feedback path  92 . Radio-frequency detector  94  (e.g., a diode-based power sensor) may be used to sense the power of the diverted radio-frequency signal on path  92 . Measured output power data from detector  94  may be provided to control circuitry  72  over path  96 . Because the tap ratio of coupler  88  is known, control circuitry  72  can use the radio-frequency output signal power measurement data on path  96  to determine whether the desired output power level from power amplifier  86  is being properly maintained. If adjustments are needed, control circuitry  72  can generate corrective control signals on path  90  in real time. When power amplifier  86  receives these control signals, the gain of power amplifier  86  will be adjusted upwards or downwards as needed. 
     In configurations in which control circuitry  72  contains more than one processor, each processor may share control duties while controlling the power of transmitted radio-frequency signals. For example, control circuitry  72  may contain a main microprocessor for running an operating system and user applications. Control circuitry  72  may also include one or more smaller more dedicated processors such as a digital signal processor and microprocessor in a baseband module. In environments such as these, each processor may run its own control process. Communications between processors may be implemented using control lines, shared memory, or any other suitable technique. 
     Illustrative steps involved in controlling transmitted radio-frequency signal power levels in device  10  using sensor data and operational data of the type described in connection with  FIG. 3  and power control circuitry of the type described in connection with  FIG. 4  are shown in  FIG. 5 . As shown in  FIG. 5 , device  10  may transmit and receive wireless data during normal operation (step  98 ). Transmitted wireless data may include local area network data and Bluetooth® data being handled by antenna  62  in region  21  of device  10  and cellular telephone data being handled by antenna  64  in region  18 . During operation, control circuitry  72  ( FIGS. 3 and 4 ) may use information from proximity sensor  25  and other sensors in device  10  and may use information on which communications bands are being used and which communications protocols are being used for wireless communications (e.g., from the application processor and/or baseband module) to determine whether transmit power adjustments are warranted. Device  10  may receive transmit power adjustment commands from network  51  (e.g., a cellular base station) that inform device  10  that the transmit power should be adjusted up or down. Device  10  may also determine that real time power adjustments are desirable to compensate for changes in the operating environment for device  10  (e.g., temperature changes). Adjustments to the power of transmitted radio-frequency signals in device  10  in response to transmit power adjustment commands from a cellular base station or other conditions that are not based on the proximity of object  60  to device  10  may be performed during step  100 . 
     When control circuitry  72  determines that object (e.g., the user&#39;s head) is in the vicinity of device  10 , control circuitry  72  may reduce the maximum allowable transmit power (step  102 ). Whenever control circuitry  72  determines that object  60  (e.g., the user&#39;s head) is no longer in the vicinity of device  10 , control circuitry  72  may increase the level of the maximum allowable transmit power (step  104 ). The current value of the maximum allowable transmit power may represent a power ceiling beyond which the transmit power may not be raised, even if the adjustments of step  100  (e.g., response to a transmit power adjustment command from a cellular base station, response to a temperature-compensation command from an internal control process in device  10 , response to a user-selected power adjustment, response to non-proximity-sensor data such as data from an accelerometer, etc.) might otherwise require a larger power. 
     This is illustrated in the example of  FIG. 6 . In the graph of  FIG. 6 , transmitted radio-frequency power P from a given device  10  is plotted vertically and time is plotted horizontally. In the  FIG. 6  example, device  10  is initially transmitting radio-frequency signals at a power of P 4 . This power may satisfy regulatory limits on transmitted power provided that device  10  is not in the vicinity of the user&#39;s head. At time t 1 , the user of device  10  places device  10  in the vicinity of the user&#39;s head. The proximity between device  10  and the user&#39;s head may be detected using one or more sensors such as proximity sensor  25 . When the proximity of device  10  to the user&#39;s head is detected, the device  10  lowers the maximum permitted transmit power to P 3  (step  102  of  FIG. 5 ). Even though a higher transmit power might be desired between times t 1  and t 2  by the cellular network, the maximum allowable transmit power of P 3  is dictated by the close distance between device  10  and the user&#39;s head (e.g., a distance of less than a few centimeters). At time t 2 , device  10  is removed from the vicinity of the user&#39;s head. Sensors such as proximity sensor  25  detect this change in position, which allows the proximity-based maximum transmit power limitation to be removed (step  104  of  FIG. 5 ). Between times t 2  and t 3 , the transmitted power from device  10  is therefore maintained at power P 4 . At time t 3 , the device  10  is once more placed in proximity to the user&#39;s head, so the maximum allowable transmit power is reduced to P 3 . At time t 4 , device  10  reduces its output power to P 2  in response to an internally detected condition, in response to sensor data, or in response to a transmit power adjustment command from a cellular base station. Because power P 2  is lower than the maximum allowable power P 3 , device  10  can make this adjustment unhindered by the proximity limits imposed by the location of device  10 . 
     In making adjustments such as these, device  10  can process inputs from a variety of sensors and sources. This is illustrated in the diagram of  FIG. 7 . As shown in  FIG. 7 , device  10  may process data from multiple sources in real time to determine an appropriate transmit power level to use in transmitting radio-frequency signals (step  112 ). During step  112 , power output may be regulated using an arrangement of the type shown in  FIG. 4  (as an example). 
     Data that may be used in making power level determinations includes proximity sensor data. Proximity sensor data may be received by control circuitry  72  from proximity sensor  25 . As described in connection with touch screen capacitance  66  of  FIG. 3 , touch sensor data from a capacitive touch screen or other touch screen, from a touch pad, or from any other touch sensor may be processed by control circuitry  72  to help determine whether device  10  is in proximity to object  60  (step  114 ). Ambient light sensor data may also be used in determining whether device  10  is in proximity to object  60 . For example, if an ambient light sensor signal drops at the same time that the proximity sensor data indicates the presence of a nearby object, it may be concluded with greater certainty that device  10  is in proximity to object  60 . Ambient light sensor data may be received from a sensor such as sensor  27  ( FIG. 1 ) at step  116 . 
     Accelerometer data may be received by control circuitry  72  at step  118 . Data from an accelerometer may be used to determine whether or not device  10  is in motion (and therefore likely being held by a user) or is at rest (and therefore likely not being held by a user. Accelerometer data may also be used to determine when device  10  is being held on its side or is being maintained in a horizontal orientation. This data may be combined with data from a proximity sensor and other data to help determine whether or not to reduce transmit power levels. 
     Transmit power adjustment commands may be received from external equipment such as a cellular base station at step  108 . Internally generated information such as information on the current communications bands and protocols that are being used by device  10  may be gathered at step  110 . 
     During step  112 , control circuitry  72  may process data gathered during any suitable combination of steps  106 ,  108 ,  110 ,  114 ,  116 , and  118  to determine an appropriate transmit power level at which to transmit radio-frequency signals from device  10 . 
     It may be desirable to make transmit power adjustments in more than one band. For example, during the operations of steps  110  and  112  of  FIG. 7 , it may be desirable to maintain the total transmitted power below a particular level while transmission are being made in two or more different communications bands. In this type of situation, increases in transmit power in a first band may be offset by automatically reducing the transmit power in a second band. 
     Adjustments of this type may be made to maintain the total power level constant. For example, power reductions in one band may be made that exactly offset power increases that arise in another band. If desired, power adjustments may be made unequally, by imposing weighting factors on each of the bands. In this type of scenario, an increase in transmit power in one band may be adequately compensated by a lesser decrease in transmit power in another band when permitted by applicable regulations. Power adjustments may be made in any suitable number of bands (e.g., in one band, in two bands, in three bands, or in more than three bands). Moreover, transmit power levels in any suitable number of bands may be taken into consideration when computing desired transmit powers (e.g., one, two, three, more than three, etc.). 
       FIG. 8  shows illustrative steps that may be involved in operating a wireless electronic device to determine appropriate radio-frequency signal power settings for transmitted signals in situations in which one or more communications bands are being used. During step  98 , device  10  may be operated in a system. Due to automatic activity, response to external input, or response to a user command, the transmit power associated with one or more communications bands may change, as indicated by line  120 . As step  100 , device  10  can make suitable transmit power adjustments in one or more communications bands to accommodate the changes of line  120 . Device  10  may then return to normal operation at step  98 , as indicated by line  122 . 
     During step  100 , adjustments may be made based on transmit power changes made in one or more communications bands. For example, an scheduled operation in device  10  may require that a particular communications band be activated or that the transmit power associated with that band otherwise be increased (e.g., to accommodate a system power level adjustment request, etc.). A band may also be activated or deactivated or may be subject to other transmit power adjustments based on manual input. 
     As an example, a user may desire to use a local area network (IEEE 802.11) wireless communications band (e.g., at 2.4 GHz) to download a file from a local area network. At the same time, device  10  may be handling a voice call over a cellular telephone network in a GSM 2G or 3 G communications band (as an example). Because the wireless transmissions at 2.4 GHz that have been initiated by the user in this type of situation may contribute to the total amount of radio-frequency power emission from device  10 , it may be desirable to temporarily reduce the transmit power in the cellular telephone band to accommodate the user&#39;s use of the 2.4 GHz band. Once use of the 2.4 GHz band is complete (e.g., because the file download is complete or because the user has deactivated the 2.4 GHz band), the transmit power level in the cellular telephone band can be increased. 
     As another example, device  10  may automatically activate one or more GSM bands or other suitable long-range communications bands while another band or bands (e.g., telephone or local data) are already active. In this scenario, adjustments may be made to ensure that the total power in some or all communications bands remains below a desired level. If desired, weighting factors may be assigned to each band to reflect potentially different levels of importance when considering the transmit power in those bands. These weights may be assigned based on the amount by which each band&#39;s transmitted signals are believed to be absorbed by the user&#39;s body, based on the location of the antenna structures in device  10  that handle each band&#39;s signals (e.g., whether radiating towards the user&#39;s body or away from the user&#39;s body), based on regulatory limits for each band, based on other suitable factors, or based on combinations of these factors. 
     Moreover, other data may be taken into consideration when adjusting transmit powers. For example, device  10  may use global position system (GPS) data, user-supplied location data, or other suitable data to determine the current location of device  10 . The location of device  10  may then be used to determine which of multiple possible geographically-based regulatory regimes should be applied to the operation of device  10 . If, for example, it is determined that device  10  is present in a country in which the level of allowable transmit power is relatively large, device  10  may make adjustments during step  100  that allow for correspondingly larger amounts of transmitted radio-frequency power to be used by device  10 . Proximity-based transmit power adjustments and adjustments based on other factors may made in real time to accommodate these currently applicable geographic regulatory restrictions. 
     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.

Metadata:
Filing Date: 20130226
Publication Date: 20140826
Grant Date: 20140826
Priority Date: 20080605
Inventors: CABALLERO RUBEN
SCHLUB ROBERT W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W52/52", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/3838", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/283", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/246", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/283", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/52", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/52", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W88/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/3838", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 41037700