PATENT DOCUMENT

Publication Number: US-8159399-B2
Application Number: US-13254908-A
Country: US
Kind Code: B2

Title: Antenna diversity systems for portable electronic devices

Abstract:
Antenna diversity systems are provided for portable electronic devices that have wireless communications circuitry and environment sensors. The wireless communications circuitry may include multiple redundant antennas that operate in one or more overlapping radio-frequency communications bands. The environment sensors and redundant antennas may be used in implementing an antenna diversity system. For example, an electronic device may use environment sensors to select an antenna for use in handling wireless communications. The electronic devices may monitor the wireless performance of an active antenna. When the wireless performance of the active antenna degrades, the electronic devices may select a new antenna for wireless communications using the antenna diversity system and environment sensors. Antenna selection may also be made based on which features are being used in the electronic device.

Claims:
1. A portable electronic device with wireless communications circuitry, comprising:
 an accelerometer that determines an orientation of the portable electronic device relative to the direction of gravity; 
 a plurality of antennas that each transmit and receive radio-frequency signals in at least a first radio-frequency band; 
 a radio-frequency transceiver; 
 switching circuitry that selectively couples one of the plurality of antennas to the radio-frequency transceiver, wherein the plurality of antennas comprises a first antenna and a second antenna; and 
 a proximity sensor that detects when an object comes within a given distance of the first antenna, wherein when the proximity sensor detects that an object has come within the given distance of the first antenna, the switching circuitry selectively couples the second antenna to the radio-frequency transceiver. 
 
     
     
       2. The portable electronic device defined in  claim 1  wherein the switching circuitry comprises circuitry that selectively couples a given antenna in the plurality of antennas to the radio-frequency transceiver based at least partly on the orientation of the portable electronic device relative to the direction of gravity. 
     
     
       3. The portable electronic device defined in  claim 1  further comprising:
 processing circuitry that selectively couples a given antenna in the plurality of antennas to the radio-frequency transceiver based at least partly on signals from the orientation sensor that indicate which antennas out of the plurality of antennas are facing away from the direction of gravity. 
 
     
     
       4. The portable electronic device defined in  claim 1  wherein the first antenna is located at one end of the portable electronic device and the second antenna is located at an opposite end of the portable electronic device. 
     
     
       5. The portable electronic device defined in  claim 1  wherein when the proximity sensor has not detected that an object has come within the given distance of the first antenna, the switching circuitry selectively couples the first antenna to the radio-frequency transceiver. 
     
     
       6. The portable electronic device defined in  claim 1  further comprising:
 processing circuitry that uses signals from the orientation sensor that indicate the orientation of the portable electronic device to determine that a given antenna out of the first and second antennas is facing away from the direction of gravity, wherein when the proximity sensor does not detect that an object has come within the given distance of the first antenna, the given antenna is selectively coupled by the switching circuitry to the radio-frequency transceiver. 
 
     
     
       7. A portable electronic device comprising:
 first and second antennas that each transmit and receive radio-frequency signals in at least a first radio-frequency band; 
 a first proximity sensor that is located adjacent to the first antenna and that detects objects relative to the first antenna; 
 a second proximity sensor that is located adjacent to the second antenna and that detects objects relative to the second antenna; 
 a radio-frequency transceiver; and 
 switching circuitry that selectively couples a selected one of the first and second antennas to the radio-frequency transceiver, wherein the switching circuitry selectively couples the first to the radio-frequency transceiver whenever a given communications protocol is being used by the radio-frequency transceiver and wherein the switching circuitry selectively couples a selected one of the first and second antennas to the radio-frequency transceiver based on signals from the first and second proximity sensors whenever the given communications protocol is not being used by the radio-frequency transceiver. 
 
     
     
       8. The portable electronic device defined in  claim 7  wherein each proximity sensor comprises a light emitting diode that emits light at an infrared frequency from the portable electronic device and a light detecting diode that detects light at the infrared frequency that has been reflected back to the portable electronic device. 
     
     
       9. The portable electronic device defined in  claim 7  wherein the given communications protocol comprises a Bluetooth® communications protocol. 
     
     
       10. The portable electronic device defined in  claim 7  wherein the first antenna is located at one end of the portable electronic device and the second antenna is located at an opposite end of the portable electronic device.

Description:
BACKGROUND 
     This invention relates generally to antenna diversity systems, and more particularly, to antenna diversity systems for portable electronic devices. 
     Portable electronic devices such as handheld 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, portable 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 and the unlicensed 60 GHz band (57-66 GHz). 
     A number of compromises are typically made when designing antennas for a portable electronic device. For example, antennas that protrude excessively from a device housing may be unsightly. Antennas that are located within a device housing may be more desirable from an esthetic point of view, but can be challenging to design. Internal antennas are sometimes subject to proximity effects that make antenna performance dependent on the position of objects (such as a user&#39;s body) relative to the antenna. 
     Electronic devices that have redundant antennas (e.g., two or more antennas that operate in similar radio-frequency bands) may use diversity schemes to improve the reliability and performance of wireless communications activities. Traditional diversity schemes involve monitoring the strength or quality of signals that are received from multiple antennas in real time. If an antenna&#39;s performance drops below a given threshold, another antenna may be used for wireless communications activities. Antenna diversity schemes of this type may offer superior performance to arrangements that rely solely on a single antenna. However, waiting for antenna performance to degrade before making antenna adjustments can lead to undesirable dropped signals. 
     It would therefore be desirable to be able to provide improved antenna diversity systems. 
     SUMMARY 
     Antenna diversity systems are provided for portable electronic devices. The antenna diversity systems may use proximity sensors or other environment sensors to improve the wireless communications performance of portable electronic devices that operate in rapidly changing environments. The portable electronic devices may have wireless communications circuitry that includes transceiver circuitry, two or more antennas that operate in identical or similar radio-frequency communications bands, and circuitry for coupling a desired one of the antennas to the transceiver circuitry. The environment sensors may include any suitable sensors such as proximity sensors, ambient light sensors, accelerometers or other orientation sensors, touch sensors, thermal sensors, combinations of such sensors, etc. 
     The antenna diversity systems may use information from environment sensors and information from application software to determine which of the antennas is most likely to have satisfactory performance for wireless communications activities. For example, in an electronic device with an orientation sensor, a diversity system may be able to determine whether the electronic device is upright or upside down and then select the antenna that is facing upwards. In another arrangement, in an electronic device with multiple redundant antennas each of which is co-located with a respective proximity sensor, a diversity system may use information from the proximity sensors to determine which antennas have external objects nearby that may obstruct wireless signals and may then select an antenna that does not have an external object nearby. With one suitable arrangement, in an electronic device configured to operate as a cellular telephone, a diversity system may use information from application software indicating that a telephone call is in progress to select the antenna that is most likely to be away from a user&#39;s head (e.g., an antenna located away from an ear speaker of the electronic device). 
     Antenna diversity systems in electronic devices with environment sensors may also monitor the performance of an active antenna and switch to another antenna when the active antenna&#39;s performance drops below a threshold. For example, after an antenna has been selected using information from environment sensors or application software, an antenna diversity system may monitor the signal strength of incoming wireless signals on the active antenna and may switch to another antenna if the signal strength drops to an unacceptable level. 
     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 that may be used to implement an antenna diversity system in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative portable electronic device that may be used to implement an antenna diversity system in accordance with an embodiment of the present invention. 
         FIG. 3  is a circuit diagram of an illustrative electronic device that has multiple antennas and antenna switching circuitry and that may be used to implement an antenna diversity system in accordance with an embodiment of the present invention. 
         FIG. 4  is a top view of an illustrative portable electronic device that has multiple antennas and environment sensors and that may be used to implement an antenna diversity system in accordance with an embodiment of the present invention. 
         FIG. 5  is a top view showing an illustrative portable electronic device with multiple antennas that may be used to implement an antenna diversity system and showing an object that may cover one of the device&#39;s antennas in accordance with an embodiment of the present invention. 
         FIG. 6  is a perspective view of an illustrative handheld portable electronic device that may be used to implement an antenna diversity system in accordance with an embodiment of the present invention. 
         FIG. 7  is a perspective view of the back side of the portable electronic device in  FIG. 6  in accordance with an embodiment of the present invention. 
         FIG. 8  is a flow chart of illustrative steps involved in using signals from environment sensors and radio-frequency signal conditions in an antenna diversity system in an electronic device to choose an antenna to perform wireless communications activities in accordance with an embodiment of the present invention. 
         FIG. 9  is a table that shows illustrative antenna selections that may be made in an antenna diversity system in an electronic device using information from non-radiofrequency-based sources in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to antenna diversity systems, and more particularly, to antenna diversity systems for electronic devices. The electronic devices may be portable electronic devices such as laptop computers, tablet computers (e.g., slate-shaped portable electronic devices), or small portable computers of the type that are sometimes referred to as ultraportables. Portable electronic devices may also be somewhat smaller devices. 
     The 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 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 electronic device such as a portable electronic device in accordance with an embodiment of the present invention is shown in  FIG. 1 . Device  10  may be any suitable electronic device. As an example, device  10  may be a laptop computer. 
     Device  10  may handle communications over one or more communications bands. Typical communications bands that may be handled by the wireless communications circuitry in device  10  include the 2.4 GHz band that is sometimes used for Wi-Fi® (IEEE 802.11) and Bluetooth® communications, the 5 GHz band that is sometimes used for Wi-Fi communications, the 1575 MHz Global Positioning System band, the 2G and 3G cellular telephone bands (e.g., 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz), the licensed WiMAX® bands (e.g., 2.3 GHz, 2.5 GHz, and 3.5 GHz), and the unlicensed 60 GHz band (e.g., the 57-64 GHz band in the United States and the 59-66 GHz band in Europe and Japan). These bands may be covered by using single and multiband antennas. For example, cellular telephone communications can be handled using multiband cellular telephone antennas and local data communications can be handled using multiband wireless local area network antennas. 
     Device  10  has housing  12 . Housing  12 , which is sometimes referred to as a case, may be formed of any suitable materials including plastic, glass, ceramics, metal, 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 as not to disturb the operation of conductive antenna elements that are located in proximity to housing  12 . 
     Housing  12  or portions of housing  12  may also be formed from conductive materials such as metal. An illustrative metal housing material that can be used is anodized aluminum. Aluminum is relatively light in weight and, when anodized, has an attractive insulating and scratch-resistant surface. If desired, other metals can be used for the housing of device  10 , such as stainless steel, magnesium, titanium, alloys of these metals and other metals, etc. In scenarios in which housing  12  is formed from metal elements, one or more of the metal elements can be used as part of the antennas in device  10 . For example, metal portions of housing  12  and metal components in housing  12  may be shorted together to form a ground plane in device  10  or to expand a ground plane structure that is formed from a planar circuit structure such as a printed circuit board structure (e.g., a printed circuit board structure used in forming antenna structures for device  10 ). 
     Device  10  may have one or more keys such as keys  114 . Keys  114  can be formed on any suitable surface of device  10 . In the example of  FIG. 1 , keys  114  have been formed on the top surface of device  10 . With one suitable arrangement, keys  114  form a keyboard on a laptop computer. Keys such as keys  114  may also be referred to as buttons. 
     If desired, device  10  may have a display such as display  16 . Display  16  may be a liquid crystal diode (LCD) display, an organic light emitting diode (OLED) display, a plasma 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 can be integrated into display  16  (e.g., using a capacitive touch sensor). Device  10  may also have a separate touch pad device such as touch pad  116 . 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. If desired, a touch screen integrated into display  16  to make display  16  touch sensitive may function as a proximity sensor in addition to functioning as a touch sensor (e.g., so that display  16  can detect objects that are in close proximity to display  16  but are not actually touching display  16 ). Keys  114  may, if desired, be arranged adjacent to display  16 . With this type of arrangement, the buttons may be aligned with on-screen options that are presented on display  16 . A user may press a desired button to select a corresponding one of the displayed options. 
     Device  10  includes circuitry  104 . Circuitry  104  may include storage, processing circuitry, antenna switching circuitry, and input-output components. Wireless transceiver circuitry in circuitry  104  may be used to transmit and receive radio-frequency (RF) signals. Transmission lines (e.g., communications paths) such as coaxial transmission lines and microstrip transmission lines are used to convey radio-frequency signals between transceiver circuitry and antenna structures in device  10 . As shown in  FIG. 1 , for example, transmission lines  118  and  120  are used to convey signals between circuitry  104  and antenna structures  106  and  108 , respectively. Communications paths  118  and  120  (i.e., transmission lines  118  and  120 ) can be, for example, coaxial cables that are connected between an RF transceiver (sometimes called a radio) and multiband antennas. 
     Antenna structures such as antenna structures  106  and  108  may be located in regions  180  and  210 , respectively, (e.g., at opposite ends of a top edge of an upper portion of housing  12 ) as shown in  FIG. 1  or in other suitable locations. For example, antenna structures such as antenna structures  106  and  108  can be located on another housing edge or on another surface of housing  12  (e.g., on the surface of keys  114 ). 
     Device  10  may have multiple antennas that are each used to cover the same communications band or bands. For example, two pentaband cellular telephone antennas may be provided at opposing ends of the top edge of device  10  (e.g., in regions  180  and  210 ) or two dual band (2.4 GHz/5 GHz) GPS/Bluetooth®/IEEE-802.11 antennas may be provided at opposing ends of the top edge of device  10  (e.g., in regions  180  and  210 ). Device  10  may also have one or more antennas that do not overlap in their coverage of communications bands (e.g., antennas that are not used in a diversity arrangement). For example, device  10  may have two similar dual band GPS/Bluetooth®/IEEE-802.11 antennas (e.g., one in region  180  and one in region  210 ) while only having one pentaband cellular telephone antenna in region  180  or in region  210 . These are merely illustrative arrangements. Any suitable antenna structures may be used in device  10  if desired. 
     Device  10  may have environment sensors such as orientation sensors (e.g., acceleration sensors), proximity sensors (e.g., sensors that emit infrared light and detect when this emitted light is reflected back to device  10 ), ambient light sensors, temperature sensors, etc. Acceleration sensors such as orientation sensors may be used to measure the orientation of device  10  relative to a horizontal plane (e.g., relative to the ground). The environment sensors may be located in any suitable portion of device  10  such as near the antennas of device  10 . User input devices such as touchpad  116 , keys  114 , and touch screen display  16  may, if desired, serve as environment sensors, because activity from these devices typically indicates the presence of an external object such as a user&#39;s finger. When device  10  has multiple antennas that overlap in their coverage of radio-frequency bands, environment sensors in device  10  may be used in determining which antenna is most likely to be suitably positioned for successful wireless communications. 
     As one example, device  10  may have sensors such as sensor  112  (located near antenna  108 ) and sensor  110  (located near antenna  106 ) that detect when objects are near antennas such as antennas  106  and  108  during operation of device  10 . Sensors  110  and  112  are shown as being located on a top edge of housing  12  in device  10  of  FIG. 1 . This is merely illustrative. Sensors such as sensors  110  and  112  may be placed at any suitable location in device  10 . For example, sensors such as sensors  110  and  112  may be located on an inside edge of device  10  near regions  180  and  210 , respectively. Sensors  110  and  112  may be based on any suitable type of sensor such as a proximity sensor, a thermal sensor, a light sensor, etc. Thermal sensors may include thermal sensors based on thermocouples, diodes, and any other suitable sensor technologies. With one suitable arrangement, sensors  110  and  112  may each be formed from a light source such as a light emitting diode that emits infrared light and a photodetector such as a photodiode that detects infrared light. In this type of arrangement, when an object comes into proximity with a proximity sensor such as sensor  110  or sensor  112 , the emitted infrared light may reflect off of the object and be detected by the light detecting diode. 
     With one arrangement, when device  10  has two similar antennas, one in region  180  and one in region  210 , device  10  may use sensors such as sensors  110  and  112  to determine which of the two antennas is more likely to be suitable for wireless communications activities. When device  10  determines that an object is near region  180 , device  10  may switch to using the antenna in region  210  for wireless communications, because the antenna in region  180  is likely to have reduced performance due to the proximity of the object and its potential to block radio-frequency signals. 
     A schematic diagram of an illustrative portable electronic device such as a handheld electronic device that may be used to implement an antenna diversity system is shown in  FIG. 2 . Portable device  10  may be a laptop computer, a table computer, mobile telephone, a mobile telephone with media player capabilities, a handheld computer, a remote control, a game player, a global positioning system (GPS) device, 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 antenna diversity applications, 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 3G communications services (e.g., using wide band code division multiple access techniques), 2G cellular telephone communications protocols, WiMAX® communications protocols, communications protocols for the unlicensed 60 GHz band, 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 , keys  114 , and touch pad  116  are examples of input-output devices  38 . 
     Input-output devices  38  can 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). 
     Environment sensors  41  can include sensors such as acceleration sensors (e.g., accelerometers and other orientation sensors), proximity sensors, thermal sensors, light sensors, etc. If desired, proximity sensors may be based on a light emitting diode and a corresponding light detecting diode that detects emitted light from the light emitting diode that is reflected back towards device  10  from nearby objects. User input devices  40  may also be used as environment sensors  41 . For example, buttons and touch-screen input devices may be used as proximity detectors for detecting the presence of an object. Environment sensors  41  (and processing circuitry  36 ) may be used in implementing an antenna diversity system in device  10 . For example, sensors  41  may be used to help determine which antenna in device  10  would be most likely to have satisfactory radio-frequency performance in a given situation. 
     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), 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 . 
     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, the licensed WiMAX® bands at 2.3 GHz, 2.5 GHz, and 3.5 GHz, and the unlicensed 60 GHz band (e.g., the 57-64 GHz band in the United States and the 59-66 GHz band in Europe and Japan), and the global positioning system (GPS) band at 1575 MHz. 
     As shown in  FIG. 3 , device  10  may implement an antenna diversity system in which the device switches between multiple antennas to optimize wireless communications performance. If desired, device  10  may have multiple antennas such as antennas  100 ,  101 , and  102  that cover similar radio-frequency bands, sensors such as sensors  200 ,  201 , and  202  (e.g., environment sensors  41 ), and processing circuitry  36  for use in selecting which antenna in device  10  would be most likely to have satisfactory radio-frequency performance (e.g., by monitoring the environment around device  10 ). Antenna switching circuitry  54  may be used to electrically couple the selected antenna (e.g., one of antennas  100 ,  101 , or  102 ) to transceiver circuitry  56 . With another suitable arrangement, transceiver circuitry  56  may be directly connected to multiple antennas and may itself perform switching operations (e.g., antenna switching circuitry  54  may be integrated into transceiver circuitry  56 ). If desired, device  10  may have multiple antenna switching circuits  54 , multiple transceivers  56 , and multiple sets of antennas (e.g., in embodiments in which device  10  has multiple antenna diversity systems). 
     Each antenna  100 ,  101 , and  102  may be implemented using a single antenna or an array of antennas. For example, one or more of antennas  100 ,  101 , and  102  may be formed from multiple antenna elements that make up an electronically steerable antenna array. If desired, one or more of antennas  100 ,  101 , and  102  may include an antenna array used in supporting IEEE 802.11n wireless communications (e.g., in supporting multiple-input multiple-output, or MIMO, schemes). In single antenna and antenna array arrangements multiple antenna structures may be combined to provide extended frequency coverage. For example, each of antennas  100 ,  101 , and  102  may be formed from two or more antenna structure that are used together to provide multi-band radio-frequency communications capabilities. 
     Sensors such as sensors  200 ,  201 , and  202  may be located at any suitable location in device  10 . With one suitable arrangement, sensors  200 ,  201 , and  202  are located near (e.g., within millimeters or centimeters) to antennas  100 ,  101 , and  102 , respectively. For example, each sensor  200 ,  201 , and  202  may be a proximity sensor such as a thermal sensor or a light sensor that is located adjacent to a particular antenna and that is used in detecting the presence of objects that could interfere with the operation of that particular antenna (e.g., one of antennas  100 ,  101 , or  102 ). Sensors  200 ,  201 , and  202  may also be formed from a portion or all of a touch screen input device such as touch screen display  16 . As an example, in the  FIG. 1  embodiment, touch screen display  16  may be used by device  10  to determine when an object (e.g., a user&#39;s hand) is in the vicinity of a particular antenna (e.g., an antenna in region  180  or region  210 ). 
     If desired, sensors such as sensors  200 ,  201 , and  202  may also include sensors that are not associated directly with a particular antenna but that are used to sense information about the general environment around device  10 . For example, one or more of sensors  200 ,  201 , and  202  (or another environment sensor  41 ) may be an orientation sensor that is used in determining whether device  10  is in a right side up or upside down position, whether device is lying on a table (e.g., relatively flat and immobile), whether device  10  is in a position that may indicate that the device is being used for a particular activity (e.g., such as when device  10  is a device sometimes referred to as a personal digital assistant and is being held in the hand of a user), etc. 
     Transceiver circuitry  56  may also be used in an antenna diversity system (e.g., to select one of antennas  100 ,  101 , or  102  for use in wireless communications). For example, transceiver circuitry  56  may analyze the radio-frequency signals that are received by device  10  to gather information on current radio-frequency communication conditions. Transceiver  56  may determine the strength of incoming radio-frequency signals and may determine error rates for incoming data for each antenna in device  10 . If desired, transceiver  56  may determine the strength of incoming and outgoing RF signals using any suitable method such as by using error-checking codes that are applied to incoming packet and frame payloads and by observing whether or not proper acknowledgment messages are received by transceiver  56  in response to packets transmitted by device  10 . Transceiver  56  may gather information on RF conditions by measuring reflections from the radio-frequency signals that transceiver  56  has generated (e.g., because an object near the active antenna has reflected transmitted signals back towards an active antenna such as one of antennas  100 ,  101 , or  102 ). Information from transceiver circuitry  56  on current radio-frequency communication conditions may be conveyed to processing circuitry  36  to use in antenna selection (e.g., in the device&#39;s antenna diversity system). 
     Processing circuitry  36  may use information from environment sensors such as sensors  200 ,  201 , and  202 , from user input devices  40 , from transceiver circuitry  56  (such as information on the current signal strength of incoming radio-frequency signals), from software running on device  10  (i.e., on processing circuitry  36 ), and information from other suitable sources to select which antenna (i.e., antenna  100 ,  101 , or  102 ) is to be used for radio-frequency communications activities. Processing circuitry  36  may generate and convey control signals to antenna switching circuitry  54  that direct the switching circuitry to couple the selected antenna to transceiver circuitry  56 . If desired, antenna switching circuitry  54  may be integrated with transceiver circuitry  56  into a single integrated circuit (e.g., a single chip). 
     As shown in  FIG. 4 , device  10  may be a compact electronic device such as a tablet computer (e.g., a slate-shaped portable electronic device). Device  10  of  FIG. 4  may implement an antenna diversity system with multiple antennas  52 , sensors  62  (e.g., proximity sensors), portions  64  of a touch screen display such as display  16  that are used to detect objects (such as a user&#39;s hand), and environment sensors such as sensor  41  (which are generally located within a device housing). In general, device  10  may have any suitable number of antennas  52 , sensors  62 , portions  64 , and sensors  41 . 
     In the  FIG. 4  embodiment, sensor  41  may be an orientation sensor that is used to determine the position of device  10 . For example, sensor  41  may be an accelerometer capable of determining the direction of gravity relative to device  10  (e.g., whether the device is being held upright, is lying flat on a table, or is in another orientation with respect to the ground). An orientation sensor such as sensor  41  may be used to determine which antenna  52  in device  10  is pointing upwards and may therefore exhibit improved radio-frequency performance relative to the performance of antennas pointing towards the ground. 
     Any suitable number of antennas  52 , sensors  62 , and portions  64  may be provided in device  10 . In general, a device that has a larger number of antennas is more likely to have at least one antenna with satisfactory radio-frequency communications performance. If desired, each antenna  52  can have an associated sensor  62  that detects the presence of an object in the vicinity of its associated antenna  52 . Portions  64  of touch screen display  16  may be used in place of sensors  62  or in addition to sensors  62  to determine when an object is in proximity to a particular antenna. 
       FIG. 5  shows how an electronic device such as device  10  that has two antennas such as antenna  52  and antenna  53  may use an antenna diversity system based on non-radio-frequency sensors such as proximity sensor  62  and proximity sensor  63 . 
     In the  FIG. 5  example, when one of the sensors (e.g., sensor  63  under object  66 ) or a portion of touch screen display  16  near antenna  53  detects the presence of an object that may interfere with radio-frequency communications such as object  66  (e.g., a user&#39;s hand), device  10  may switch to using a different antenna (e.g., antenna  52 ) for wireless communications. 
     By switching to an unobstructed antenna such as antenna  52  using information from sensors  62  and  63  rather than waiting for radio-frequency communications with antenna  53  to fail, the wireless communications performance of device  10  may be improved. In contrast, with traditional antenna diversity methods, an electronic device would not switch antennas until radio-frequency communications had already degraded, which could result in a disruption of wireless communications activities. 
     An illustrative handheld electronic device in accordance with an embodiment of the present invention is shown in  FIG. 6 . Device  10  of  FIG. 6  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. 
     Housing  12  may have a bezel  14  that surrounds the top of display  16 . Display screen  16  may be a touch screen with a capacitive touch sensor that accepts user touch and multi-touch commands. 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. 6 , 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. 
     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 use antenna structures formed from one or more single antennas (single-band or multiband), one or more antenna arrays (e.g., single-band or multi-band), beam-forming antenna arrays such as steerable beam-forming antenna arrays (sometimes referred to as beamsteering antennas or beamsteering arrays), other directional antennas, sectorized antennas, etc. Device  10  may have multiple antennas that are used to cover a single communications band or multiple antennas each of which may cover multiple communications bands. In one embodiment, two pentaband cellular telephone antennas may be provided at opposing ends of device  10  (e.g., in regions  18  and  21 ). Two dual band GPS/Bluetooth®/IEEE-802.11 antennas may be also be provided at opposing ends of device  10  (e.g., in regions  18  and  21 ). Device  10  may also have one or more antennas that do not overlap in their coverage of communications bands (e.g., antennas that are not used in a diversity system). For example, device  10  may have two short range 2.4 GHz antennas (e.g., one in region  18  and one in region  21 ) while only having one cellular telephone antenna in region  18  or in region  21 . These are merely illustrative arrangements. Any suitable antenna structures may be used in device  10 . 
     As one example, device  10  may have a sensor such as sensor  25  located near or within speaker port  23  that detects when an object such as a user&#39;s ear is close to port  23  during operation of device  10 . Sensor  25  may be based on any suitable sensor such as a proximity sensor, a thermal sensor, a light sensor, etc. Thermal sensors may be based on thermocouples, diodes, and any other suitable sensor technologies. With one suitable arrangement, sensor  25  may be a proximity sensor formed from a light emitting diode that emits infrared light and a light detecting diode that detects the infrared light. In this type of arrangement, when an object such as a user&#39;s ear comes into proximity with sensor  25 , the emitted infrared light may reflect off of the object and be detected by the light detecting diode. 
     If device  10  has two similar antennas, one in region  18  and one in region  21 , device  10  may use sensor  25  to determine which of the two antennas is more likely to be suitable for wireless communications activities. In this example, when device  10  determines that the user&#39;s ear is near port  23 , device  10  may switch to using the antenna in region  18  for wireless communications since the antenna in region  21  is likely to have reduced performance due to the proximity of the user&#39;s head. This type of arrangement may also reduce the amount of radio-frequency radiation that is produced by device  10  in close proximity to the user&#39;s head. 
     A view of the back side (rear) of the electronic device shown in  FIG. 6  is shown in  FIG. 7 . Device  10  may have antennas in region  18  and region  21 . The antennas in region  18  and region  21  may transmit and receive radio-frequency signals through dielectric portions (e.g., dielectric windows) in housing  12  such as dielectric window  58 . Dielectric window  58  may allow radio-frequency signals for the antenna in region  18  to pass through the backside of the electronic device. Dielectric window  58  may be formed from any suitable dielectric materials. Dielectric window  58  may also be formed from materials that are similar in appearance to surrounding portions of housing  12  such that dielectric window  58  blends in to the surrounding portions (and may therefore be less visible to a user). 
     Sensors such as sensors  60  and  61  may be located on the backside of device  10  in or near region  18  (e.g., near the antennas located in region  18 ). If desired, device  10  may be provided with either sensor  60  or sensor  61  or may have both sensors  60  and  61 . Sensors  60  and  61  may be proximity sensors used by device  10  to detect when an object is in the vicinity of region  18  and therefore likely to interfere with radio-frequency communications. For example, sensors  60  and  61  may detect when device  10  is resting right side up on a table or when device  10  is being held by a user with the user&#39;s hand covering antenna window  58 . A similar arrangement may be used for the antenna in region  21 . 
     When device  10  is resting right side up on a table, dielectric window  58  may be blocked by the table. A sensor such as sensor  60  or sensor  61  may detect this condition. In response, device  10  may switch antennas in region  21  into use for wireless communications (e.g., antennas in region  21  may be used to send and receive radio-frequency signals through the top or front side of device  10 ). 
       FIG. 8  is a flow chart of illustrative steps involved in using an antenna diversity system for an electronic device such as device  10  that has multiple antennas and environment sensors such as proximity sensors and orientation sensors. 
     At step  68 , a user of device  10  may reorient (i.e., reposition) device  10 , grasp device  10  in a different manner, or otherwise alter the physical environment around device  10 . Examples of reorienting device  10  include situations in which a user picks device  10  up from a table, a user raises device  10  to their ear, a user shifts device  10  between landscape and portrait orientations, a user places device  10  right side up or upside down onto a table, a user opens or closes device  10  (e.g., when device  10  is suitable device such as a laptop computer with pivoting housing portions), etc. 
     At step  70 , the change in the physical environment around device  10  that arose during step  68  may be detected by environment sensors such as sensors  41  which may include portions of touch screen display  16 . For example, a proximity sensor may detect that an object has come into or left the vicinity of the electronic devices (e.g., by detecting body heat, by detecting a change in ambient or reflected light, by detecting changing electrical properties in a proximity sensor induced by nearby objects such as capacitance changes, etc.). An orientation sensor may detect when device  10  has been reoriented. Data from multiple sensors may be used to detect more complex changes in the physical environment surrounding device  10 . For example, when thermal sensors detect an increase in ambient temperature, light sensors detect a drop in the intensity of ambient light, and proximity sensors detect nearby objects all at the same time, device  10  may be able to determine within a certain probability that the device has been placed into a user&#39;s pocket. 
     At step  72 , device  10  may switch a particular antenna (such as one of antennas  52 ) into use in handling wireless communications activities based on the inputs of environment sensors  41 . For example, device  10  may opt to use the antenna that is farthest from external objects (such as a user&#39;s hand) or an antenna that is facing upwards. Device  10  may select an antenna that maximizes the likelihood that wireless communications activities will be successful (i.e., that signals will be received with sufficient signal strength). 
     In general, device  10  may choose which antenna to use based on information from applications that are running on device  10 , from accessories  46 , from user input devices  40 , from environment sensors such as sensors  41 , etc. For example, in a device  10  that has cellular telephone functionality, device  10  may select an antenna based on whether or not the device is being used to make a cellular telephone call. Device  10  may also use information such as whether a speakerphone is being used or whether a Bluetooth® headset or wired headset is connected to the device and is being used (both of which may indicate that the device is not near a user&#39;s ear even if the device is being used to make a cellular telephone call). As an example when device  10  has cellular telephone functionality (e.g., in an arrangement of the type shown in  FIG. 6 ), device  10  may choose to use an antenna in region  18  whenever the device is being used to make a cellular telephone call, so that the user&#39;s head is less likely to interfere with the antenna in region  18  (e.g., when a cellular telephone application is active and when speakerphone and headset devices are not being used). When the speakerphone or headset is being used, device  10  may use an antenna that is pointing upwards (e.g., such as the “top” antenna in region  21 ). Device  10  may determine which antenna is pointing upwards using information from an orientation sensor (i.e., an accelerometer). 
     By selecting an antenna in step  72  using information obtained from non-radio-frequency based sources, device  10  may exhibit improved wireless communication performance, particularly when device  10  is a highly mobile electronic device such as a cellular telephone handset or a portable computer. Because the radio-frequency conditions around highly mobile electronic devices can change frequently, waiting for radio-frequency conditions to degrade (as occurs in steps  74 ,  76 , and  78 ) before switching antennas may be undesirable (e.g., because RF-based diversity systems typically take longer to respond to changing RF signal conditions). By proactively selecting antennas using non-RF based information (e.g., using information from environment sensors such as sensors  41  as in steps  70  and  72 ) before radio frequency conditions deteriorate, the overall wireless communications performance of device  10  may be improved. 
     Device  10  may perform steps  70  and  72  when initiating wireless communications activities. For example, when wireless communications are initiated, device  10  may use sensor data in selecting a particular antenna to use in a first attempt at connecting to a wireless network such as wireless network  51 . Device  10  may use information from environment sensors (e.g., non-radio-frequency sensors). If desired, steps  70  and  72  may be repeated continuously during device operation to ensure proper antenna selection. 
     Whenever device  10  is performing wireless communications functions, the electronic device may also monitor radio-frequency signal conditions in real time (step  74 ). Device  10  may monitor RF signal conditions using any suitable method such as by measuring the strength (i.e., signal-to-noise ratio) of incoming wireless signals, by listening for reflections from transmitted wireless signals, by measuring error rates in incoming data, by observing the presence or absence of acknowledgement receipts returning from other wireless devices, etc. 
     As illustrated by step  76 , device  10  may detect that radio-frequency signal conditions have degraded below a given threshold (such as when the signal-to-noise ratio of received signals drops to an unacceptable level). In response, the antenna diversity system implemented on device  10  may select another antenna (step  78 ). 
     During step  78 , device  10  may select an optimum antenna to use in wireless communications activities. Because (in this example) device  10  is selecting a new antenna following the degradation of radio-frequency signal conditions (in step  76 ), device  10  may select an antenna in a similar manner to that of step  72  but may exclude from the selection those antennas that have a recent history of poor radio-frequency performance (i.e., that have had poor signal conditions). For example, if a given antenna selected in step  72  has insufficient radio-frequency performance, device  10  may exclude that antenna during its process of selecting a new antenna in step  78 . When device  10  is attempting to connect to a new wireless network or reconnect to a wireless network, steps  74 ,  76 , and  78  may be iteratively repeated either until wireless communications are successful or wireless communications have been attempted using all of the device&#39;s antennas. Steps  70  and  72  may also periodically be repeated if desired. 
     As illustrated in the table of  FIG. 9 , device  10  may select an antenna to use based on information from sensors and non-sensor sources. For example, device  10  may select an antenna using information from environment sensors  41  and user input devices  40 , information from software running on device  10  (e.g., information on which applications or which portions of applications are active), information associated with the use of accessories  46  such as a Bluetooth® headset (e.g., whether there is an active wireless headset coupled to device  10 ), information from combinations of these and other sources, etc. 
     In the  FIG. 9  example, device  10  might be a handheld electronic device of the type shown in  FIGS. 6 and 7 . For example, device  10  might be a handheld electronic device with two cellular telephone antennas at opposing ends of device  10  (e.g., in regions  18  and  21 ). Two 2.4 GHz antennas may be also be provided at opposing ends of device  10  (e.g., in regions  18  and  21 ). These are merely illustrative arrangements. 
     One possible situation that device  10  may be able to identify is illustrated in the first row of the table of  FIG. 9 . In this situation, device  10  may be placed in a user&#39;s pocket. When device  10  placed in a user&#39;s pocket, an ambient light sensor may sense that the surrounding environment is dark and a proximity sensor such as sensor  25  may detect that an object is nearby. Device  10  may use an orientation sensor to identify the uppermost antenna (i.e., the antenna in region  21  if device  10  is vertically upright) in device  10 . This antenna may then be switched into use for wireless communications. If desired, when device  10  is a cellular telephone, device  10  may only opt to use an antenna in region  21  for wireless communications in situations in which a cellular telephone application is not presently running (e.g., in order to minimize the amount of radio-frequency radiation emitted in the vicinity of a user&#39;s head). 
     When device  10  is a cellular telephone device, device  10  may be held up against a user&#39;s ear and used during cellular telephone calls. As illustrated in the second row of the table of  FIG. 9 , device  10  may be able to recognize this situation using information from software and/or hardware that indicates that a cellular telephone call is being made. As an example, device  10  may use information from a headset proximity sensor (i.e., sensor  25 ) to determine when the device is being held against a user&#39;s ear during cellular telephone calls. In this situation, device  10  can use an antenna that is located away from the user&#39;s head such as an antenna in region  18 . 
     Another situation that device  10  may be able to identify occurs when device  10  is held in a user&#39;s hand and is being used for activities other than cellular telephone activities. For illustrative purposes, this situation is referred to herein as a personal digital assistant (PDA) mode and is illustrated in the third row of the table of  FIG. 9 . In PDA mode, device  10  may not be running a telephone application, an orientation sensor may be indicating that the device is upright with its display facing up (e.g., in approximately the position illustrated in  FIG. 6 ), and a headset proximity sensor such as sensor  25  may be indicating that no objects are close to the proximity sensor. When device  10  detects these conditions, device  10  may use its orientation sensor to identify the uppermost antenna (i.e., the antenna in region  21 ). The uppermost antenna may then be switched into use. 
     With one suitable arrangement, device  10  may be a handheld electronic device and may have two similar dual band GPS/IEEE-802.11 antennas (e.g., one in region  18  and one in region  21 ) while only having one dual band GPS/Bluetooth®/IEEE-802.11 antenna in region  18 . In this type of arrangement, when the dual band GPS/Bluetooth®/IEEE-802.11 antenna in region  18  is active, it may be preferable to use the dual band GPS/IEEE-802.11 antenna in region  21  (rather than the similar antenna in region  18 ). The conditions of this situation are illustrated in the fourth row of the table of  FIG. 9 . 
     With another suitable arrangement, device  10  may have multiple antennas with varying radiation patterns. For example, in the  FIG. 6  embodiment, device  10  may have antennas in regions  18  and  21  that transmit and receive wireless signals predominantly through the back and front faces of device  10 , respectively (e.g., through the front surface shown in  FIG. 6  and through the back surface shown in  FIG. 7 ). In this arrangement, when device  10  has an orientation sensor and is placed on a flat surface (i.e., a table), device  10  may select an antenna based on radiation patterns. For example, when device  10  is placed on a table with its front face up, device  10  may select an antenna that at least partially radiates through its front face (e.g., an antenna in region  21 ). The conditions of this situation are illustrated in the last row of  FIG. 9 . 
     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: 20080603
Publication Date: 20120417
Grant Date: 20120417
Priority Date: 20080603
Inventors: DORSEY JOHN G.
KOUGH DOUGLAS B.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/2266", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q3/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 41379128