PATENT DOCUMENT

Publication Number: US-8874041-B2
Application Number: US-201113252045-A
Country: US
Kind Code: B2

Title: Electronic device with service acquisition antenna switching

Abstract:
An electronic device may contain wireless communication circuitry. The wireless communication circuitry may include radio-frequency transceiver circuitry coupled to multiple antennas. The electronic device may use the multiple antennas to make received signal power measurements. The signal power measurements may be made for each frequency in a list of frequencies used most recently by the electronic device in conveying data traffic between the electronic device and a wireless network. Based on received signal power measurements, the electronic device may select which frequency to use in performing system acquisition operations to attempt to establish a wireless communications link between the electronic device and the wireless network. The device may make signal power measurements for each antenna in the device to determine which antenna should be used in performing the system acquisition operations or may rotate through antennas in sequence to identify an antenna that can successfully perform system acquisition operations.

Claims:
What is claimed is: 
     
       1. A method for using an electronic device that has a plurality of antennas to perform system acquisition operations to establish a wireless communications link with a wireless network, comprising:
 using only a selected one of the antennas to measure received power at each of a plurality of frequencies; 
 identifying which of the frequencies is associated with a largest of the measured received powers; 
 using the identified frequency and the selected antenna to perform system acquisition operations to attempt to establish the wireless communications link with the wireless network; 
 determining whether the system acquisition operations with the selected antenna were successful at establishing the wireless communications link; 
 in response to determining that the system acquisition operations with the selected antenna were unsuccessful at establishing the wireless communications link, switching an additional one of the antennas into use to measure received power in each of the plurality of frequencies; and 
 in response to determining that the system acquisition operations with the selected antenna were successful at establishing the wireless communications link, performing wireless communications over the wireless communications link. 
 
     
     
       2. The method defined in  claim 1  further comprising:
 after switching the additional one of the antennas into use, measuring received signal power in each of the plurality of frequencies using the additional one of the antennas. 
 
     
     
       3. The method defined in  claim 2  further comprising:
 identifying which of the frequencies is associated with a largest of the measured received powers measured using the additional one of the antennas; and 
 at the identified frequency associated with the largest of the measured received powers measured using the additional one of the antennas, using the additional one of the antennas to perform system acquisition operations to attempt to establish the wireless communications link with the wireless network. 
 
     
     
       4. The method defined in  claim 3  further comprising:
 maintaining a list of the plurality of frequencies in the electronic device. 
 
     
     
       5. The method defined in  claim 4  wherein the list of the plurality of frequencies comprises a list of frequencies most recently used to convey wireless traffic for the electronic device. 
     
     
       6. The method defined in  claim 1  wherein the electronic device comprises a portable electronic device having a rectangular housing with upper and lower ends, wherein an upper antenna is located in the upper end and a lower antenna is located in the lower end, and wherein switching the additional one of the antennas into use comprises switching the upper antenna into use in place of the lower antenna. 
     
     
       7. The method defined in  claim 1  further comprising:
 maintaining a list of the plurality of frequencies in the electronic device. 
 
     
     
       8. The method defined in  claim 7  wherein the list of the plurality of frequencies comprises a list of frequencies most recently used to convey wireless traffic for the electronic device. 
     
     
       9. A method for using an electronic device that has a plurality of antennas to perform system acquisition operations to establish a wireless communications link with a wireless network, wherein each antenna of the plurality of antennas is coupled to a different respective transceiver, the method comprising:
 using each of the plurality of antennas to measure received power in each of a plurality of frequencies by selectively activating the different respective transceivers coupled to each antenna of the plurality of antennas; 
 identifying which of the plurality of antennas and which of the frequencies is associated with a largest of the measured received powers; and 
 using the identified frequency and the identified antenna to perform system acquisition operations to attempt to establish the wireless communications link with the wireless network. 
 
     
     
       10. The method defined in  claim 9  further comprising:
 maintaining a list of the plurality of frequencies in the electronic device. 
 
     
     
       11. The method defined in  claim 10  wherein the list of the plurality of frequencies comprises a list of frequencies most recently used to convey wireless traffic for the electronic device. 
     
     
       12. The method defined in  claim 9  wherein the electronic device comprises a portable electronic device having a rectangular housing with upper and lower ends, wherein an upper antenna is located in the upper end and a lower antenna is located in the lower end, and wherein the identified antenna comprises the upper antenna. 
     
     
       13. The method defined in  claim 12  further comprising:
 maintaining a list of the plurality of frequencies in the electronic device. 
 
     
     
       14. The method defined in  claim 13  wherein the list of the plurality of frequencies comprises a list of frequencies most recently used to convey wireless traffic for the electronic device. 
     
     
       15. A method of performing system acquisition operations with a wireless electronic device to attempt to establish a wireless communications link with a wireless network, comprising:
 using at least one of a plurality of antennas in the wireless electronic device to make wireless signal power measurements; and 
 based on the wireless signal power measurements, selecting a given one of the plurality of antennas to use in performing the system acquisition operations, wherein the wireless electronic device comprises a portable electronic device having a rectangular housing with upper and lower ends, wherein an upper antenna is located in the upper end and a lower antenna is located in the lower end, and the selected antenna comprises the lower antenna. 
 
     
     
       16. The method defined in  claim 15  further comprising:
 with control circuitry in the wireless electronic device, maintaining a list of frequencies that have recently been used by the wireless electronic device in communicating with the wireless network. 
 
     
     
       17. The method defined in  claim 16  wherein using the at least one of the plurality of antennas comprises using at least a first of the antennas to measure received signal power for each of the frequencies in the list of frequencies. 
     
     
       18. The method defined in  claim 17  wherein using the at least one of the plurality of antennas comprises using at least a second of the antennas to measure received signal power for each of the frequencies in the list of frequencies. 
     
     
       19. The method defined in  claim 18  wherein selecting the given one of the plurality of antennas comprises selecting a given one of the first and second antennas. 
     
     
       20. The method defined in  claim 19  wherein selecting the given one of the first and second antennas comprises identifying which of the first and second antennas is associated with a largest of the measured received signal powers.

Description:
This relates generally to wireless communications circuitry, and more particularly, to electronic devices that have wireless communication circuitry with multiple antennas. 
     Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communication circuitry such as cellular telephone circuitry and WiMax (IEEE 802.16) circuitry. Electronic devices may also use short-range wireless communications circuitry such as WiFi® (IEEE 802.11) circuitry and Bluetooth® circuitry. 
     When powered up or following an out-of-service condition, an electronic device such as a cellular telephone performs service acquisition procedures. Using these procedures, the electronic device may establish a communications link with a wireless base station. Once the link has been established, the electronic device may wirelessly transmit and receive data traffic. 
     During operation of an electronic device such as a cellular telephone, it may sometimes be necessary to operate the device in less than optimal conditions. For example, a user may sometimes operate an electronic device near the edge of a cell or in other locations in which signal strength is poor. In some operation environments, an external object such as part of a user&#39;s body may be located in the vicinity of a device antenna and can affect wireless performance. In operating environments such as these, it may sometimes be difficult for a device to successfully complete service acquisition procedures. 
     It would therefore be desirable to be able to provide improved ways for electronic devices to perform service acquisition procedures. 
     SUMMARY 
     An electronic device may be provided that contains wireless communication circuitry. The wireless communication circuitry may include radio-frequency transceiver circuitry coupled to multiple antennas. The electronic device may be a device that contains a first antenna located in an upper portion of the device and a second antenna located in a lower portion of the device or may be a device that contains three or more antennas. 
     During operation, the electronic device may maintain a list of frequencies used most recently by the electronic device in conveying data traffic between the electronic device and a wireless network. 
     The electronic device may make received signal power measurements. The received signal power measurements may be made for each frequency in the list of recently used frequencies. Based on the received signal power measurements or other signal measurements, the electronic device may select which frequency to use in performing system acquisition operations to attempt to establish a wireless communications link between the electronic device and the wireless network. 
     The device may make signal power measurements for each antenna in the device to determine which antenna should be used in performing the system acquisition operations or the device may cycle through each of the antennas in sequence to determine whether any of the antennas can successfully perform system acquisition operations. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with wireless communication circuitry having multiple antennas in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of a wireless network including a base station and an illustrative electronic device with wireless communication circuitry having multiple antennas in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of illustrative wireless circuitry including multiple antennas and circuitry for controlling use of the antennas in accordance with an embodiment of the present invention. 
         FIGS. 4 and 5  are flow charts of illustrative operations involved in using an electronic device with multiple antennas to perform system acquisition operations in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with wireless communication circuitry. The wireless communications circuitry in a device may be used to support wireless communications in multiple wireless communication bands. The wireless communication circuitry may include multiple antennas. The antennas may be used in a single antenna mode or in a multiple antenna mode (e.g., a dual antenna mode). Control circuitry within a device may select which antenna (or antennas) to use based on signal strength measurements and other criteria. 
     The antennas can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may be formed from conductive electronic device structures such as conductive housing structures (e.g., a ground plane and part of a peripheral conductive housing member or other housing structures), traces on substrates such as traces on plastic, glass, or ceramic substrates, traces on flexible printed circuit boards (“flex circuits”), traces on rigid printed circuit boards (e.g., fiberglass-filled epoxy boards), sections of patterned metal foil, wires, strips of conductor, other conductive structures, or conductive structures that are formed from a combination of these structures. 
     An illustrative electronic device of the type that may be provided with one or more antennas (e.g., two antennas, three antennas, four antennas, five or more antennas, etc.) is shown in  FIG. 1 . Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a cellular telephone, a media player, a gaming device, etc. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electronic ink elements, liquid crystal display (LCD) components, or other suitable image pixel structures. A cover glass layer may cover the surface of display  14 . Portions of display  14  such as peripheral regions  201  may be inactive and may be devoid of image pixel structures. Portions of display  14  such as rectangular central portion  20 A (bounded by dashed line  20 ) may correspond to the active part of display  14 . In active display region  20 A, an array of image pixels may be used to display images for a user. 
     The cover glass layer that covers display  14  may have openings such as a circular opening for button  16  and a speaker port opening such as speaker port opening  18  (e.g., for an ear speaker for a user). Device  10  may also have other openings (e.g., openings in display  14  and/or housing  12  for accommodating volume buttons, ringer buttons, sleep buttons, and other buttons, openings for an audio jack, data port connectors, removable media slots, etc.). 
     Housing  12  may include a peripheral conductive member such as a bezel or band of metal that runs around the rectangular outline of display  14  and device  10  (as an example). The peripheral conductive member may be used in forming the antennas of device  10 , if desired. 
     Antennas may be located along the edges of device  10 , on the rear or front of device  10 , as extending elements or attachable structures, or elsewhere in device  10 . With one suitable arrangement, which is sometimes described herein as an example, device  10  may be provided with one or more antennas at lower end  24  of housing  12  and one or more antennas at upper end  22  of housing  12 . Locating antennas at opposing ends of device  10  (i.e., at the narrower end regions of display  14  and device  10  when device  10  has an elongated rectangular shape of the type shown in  FIG. 1 ) may allow these antennas to be formed at an appropriate distance from ground structures that are associated with the conductive portions of display  14  (e.g., the pixel array and driver circuits in active region  20 A of display  14 ). 
     If desired, a first cellular telephone antenna may be located in region  24  and a second cellular telephone antenna may be located in region  22 . Antenna structures for handling satellite navigation signals such as Global Positioning System signals or wireless local area network signals such as IEEE 802.11 (WiFi®) signals or Bluetooth® signals may also be provided in regions  22  and/or  24  (either as separate additional antennas or as parts of the first and second cellular telephone antennas). Antenna structures may also be provided in regions  22  and/or  24  to handle WiMax (IEEE 802.16) signals. 
     In regions  22  and  24 , openings may be formed between conductive housing structures and printed circuit boards and other conductive electrical components that make up device  10 . These openings may be filled with air, plastic, or other dielectrics. Conductive housing structures and other conductive structures may serve as a ground plane for the antennas in device  10 . The openings in regions  22  and  24  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element such as an inverted-F antenna resonating element formed from part of a conductive peripheral housing structure in device  10  from the ground plane, or may otherwise serve as part of antenna structures formed in regions  22  and  24 . 
     Antennas may be formed in regions  22  and  24  that are identical (i.e., antennas may be formed in regions  22  and  24  that each cover the same set of cellular telephone bands or other communications bands of interest). Due to layout constraints or other design constraints, it may not be desirable to use identical antennas. Rather, it may be desirable to implement the antennas in regions  22  and  24  using different designs. For example, the first antenna in region  24  may cover all cellular telephone bands of interest (e.g., four or five bands) and the second antenna in region  22  may cover a subset of the four or five bands handled by the first antenna. Arrangements in which the antenna in region  24  handles a subset of the bands handled by the antenna in region  22  (or vice versa) may also be used. Tuning circuitry may be used to tune this type of antenna in real time to cover a either a first subset of bands or a second subset of bands and thereby cover all bands of interest. 
     The use of device housing structures and antenna layouts of the type shown in  FIG. 1  is merely illustrative. Electronic device  10  may have the shape of a tablet computer, may be implemented using device housings with other portable shapes, or may be implemented as part of other suitable electronic equipment. Two or more antennas, three or more antennas, four or more antennas, or other suitable number of antennas may be used in device  10 . 
     In response to a power-up event or following an out-of-service condition, device  10  may perform service acquisition operations to establish a wireless communications link between device  10  and a cellular base station. Antenna operation can be disrupted when an antenna in device  10  is blocked by an external object such as a user&#39;s hand, when device  10  is placed near other external objects that interfere with proper antenna operation, or due to other factors (e.g., device orientation relative to its surroundings, etc.). Wireless communications can also be affected by the distance between device  10  and the base station, radio-frequency interference, and other environmental effects. When antenna operation is disrupted, there is a risk that service acquisition operations will be adversely affected. 
     To ensure that service acquisition operations are completed successfully, even in adverse operating environments such as when one of the antennas in device  10  is blocked, device  10  can use multiple antennas in performing service acquisition operations. For example, if one antenna is performing poorly (e.g., when signal strength is low), device  10  can switch to an alternate antenna to perform service acquisition operations. If desired, device  10  can evaluate signal strengths using both antennas and can, based on these measurements, perform system acquisition operations using whichever antenna (and frequency) is associated with the largest signal strength. Using schemes such as these or other suitable control schemes, device  10  can use multiple antennas to ensure that system acquisition operations are performed satisfactorily. 
     Device  10  may use an antenna selection algorithm to select an antenna for use during system acquisition operations. The antenna selection algorithm may run on the circuitry of device  10  and can be used to automatically select an appropriate antenna to use in real time. The antenna selection (switching) algorithm may select an appropriate antenna to use by evaluating signal strengths associated with various frequencies (channels) and, if desired, by evaluating signal strengths associated with each antenna. 
     Arrangements in which device  10  has a primary antenna and a secondary antenna are sometimes described herein as an example. This is, however, merely illustrative. Device  10  may use three or more antennas if desired. Device  10  may use antennas that are substantially identical (e.g., in band coverage, in efficiency, etc.), or may use other types of antenna configurations. 
     A schematic diagram of a system in which electronic device  10  may operate is shown in  FIG. 2 . As shown in  FIG. 2 , system  11  may include wireless network equipment such as base station  21 . Base stations such as base station  21  may be associated with a cellular telephone network or other wireless networking equipment. Device  10  may communicate with base station  21  over wireless link  23  (e.g., a cellular telephone link or other wireless communications link). 
     Device  10  may include control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  and other control circuits such as control circuits in wireless communications circuitry  34  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment such as base station  21 , storage and processing circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, IEEE802.16 (WiMax) protocols, cellular telephone protocols such as the Long Term Evolution (LTE) protocol, Global System for Mobile Communications (GSM) protocol, Code Division Multiple Access (CDMA) protocol, and Universal Mobile Telecommunications System (UMTS) protocol, etc. 
     Circuitry  28  may be configured to implement control algorithms that control the use of antennas in device  10 . For example, circuitry  28  may configure wireless circuitry  34  to switch a particular antenna into use for transmitting and/or receiving signals. Circuitry  28  may, as an example, configure wireless circuitry  34  to select an optimum antenna to use in performing system acquisition operations. Circuitry  28  may also be used in selecting an optimum antenna to use during normal operation, following system acquisition operations. 
     In some scenarios, circuitry  28  may be used in gathering sensor signals and signals that reflect the quality of received signals (e.g., received paging signals, received voice call traffic, received control channel signals, received data traffic, etc.). Examples of signal quality measurements that may be made in device  10  include bit error rate measurements, signal-to-noise ratio measurements, measurements on the amount of power associated with incoming wireless signals, channel quality measurements based on received signal strength indicator (RSSI) information (RSSI measurements), channel quality measurements based on received signal code power (RSCP) information (RSCP measurements), channel quality measurements based on signal-to-interference ratio (SINR) and signal-to-noise ratio (SNR) information (SINR and SNR measurements), channel quality measurements based on signal quality data such as Ec/lo or Ec/No data (Ec/lo and Ec/No measurements), etc. This information may be used in controlling which antenna is used. Antenna selections can also be made based on other criteria. 
     Input-output circuitry  30  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output circuitry  30  may include input-output devices  32 . Input-output devices  32  may include touch screens, buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  32  and may receive status information and other output from device  10  using the output resources of input-output devices  32 . 
     Wireless communication circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, and other circuitry for handling RF wireless signals. 
     Wireless communication circuitry  34  may include satellite navigation system receiver circuitry such as Global Positioning System (GPS) receiver circuitry  35  (e.g., for receiving satellite positioning signals at 1575 MHz). Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in cellular telephone bands such as bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz or other cellular telephone bands of interest. Wireless communication circuitry  34  can include circuitry for other short-range and long-range wireless links if desired (e.g., WiMax circuitry, etc.). Wireless communications circuitry  34  may, for example, include, wireless circuitry for receiving radio and television signals, paging circuits, etc. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communication circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable types of antenna. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, closed and open slot antenna structures, planar inverted-F antenna structures, helical antenna structures, strip antennas, monopoles, dipoles, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. As described in connection with  FIG. 1 , there may be multiple cellular telephone antennas in device  10 . For example, there may be one cellular telephone antenna in region  24  of device  10  and another cellular telephone antenna in region  22  of device  10 . In a tablet computer or other types of electronic device, different antennas may be located along one of the edges of the device, different antennas may be located at various device corners, different antennas may be located on opposing device edges, etc. The antennas in device  10  may be fixed or may be tunable. 
     Device  10  can be controlled by control circuitry that is configured to store and execute control code for implementing control algorithms (e.g., antenna selection algorithms and other wireless control algorithms). As shown in  FIG. 3 , control circuitry  42  may include storage and processing circuitry  28  (e.g., a microprocessor, memory circuits, etc.) and may include baseband processor  58 . Baseband processor  58  may form part of wireless circuitry  34  and may include memory and processing circuits (i.e., baseband processor  58  may be considered to form part of the storage and processing circuitry of device  10 ). 
     Baseband processor  58  may provide data to storage and processing circuitry  28  via path  48 . The data on path  48  may include raw and processed data associated with wireless (antenna) performance metrics for received signals such as received power (sometimes referred to as signal strength), transmitted power, frame error rate, bit error rate, channel quality measurements based on received signal strength indicator (RSSI) information, channel quality measurements based on received signal code power (RSCP) information, channel quality measurements based on signal-to-interference ratio (SINR) and signal-to-noise ratio (SNR) information, channel quality measurements based on signal quality data such as Ec/lo or Ec/No data, information on whether responses (acknowledgements) are being received from a cellular telephone tower corresponding to requests from the electronic device, information on whether a network access procedure has succeeded, information on how many re-transmissions are being requested over a cellular link between the electronic device and a cellular tower, information on whether a loss of signaling message has been received, and other information that is reflective of the performance of wireless circuitry  34 . This information may be analyzed by storage and processing circuitry  28  and/or processor  58  and, in response, storage and processing circuitry  28  (or, if desired, baseband processor  58 ) may issue control commands for controlling wireless circuitry  34 . For example, storage and processing circuitry  28  may issue control commands on path  52  and path  50  and/or baseband processor  58  may issue control commands on path  51 . 
     Wireless circuitry  34  may include radio-frequency transceiver circuitry such as radio-frequency transceiver circuitry  60  and radio-frequency front-end circuitry  62 . Radio-frequency transceiver circuitry  60  may include one or more radio-frequency transceivers such as transceivers  57  and  63  (e.g., one or more transceivers that are shared among antennas, one transceiver per antenna, etc.). In the illustrative configuration of  FIG. 3 , radio-frequency transceiver circuitry  60  has a first transceiver such as transceiver  57  that is associated with path (port)  54  (and which may be associated with path  44 ) and a second transceiver such as transceiver  63  that is associated with path (port)  56  (and which may be associated with path  46 ). Transceiver  57  may include a transmitter such as transmitter  59  and a receiver such as receiver  61  or may contain only a receiver (e.g., receiver  61 ) or only a transmitter (e.g., transmitter  59 ). Transceiver  63  may include a transmitter such as transmitter  67  and a receiver such as receiver  65  or may contain only a receiver (e.g., receiver  65 ) or only a transmitter (e.g., transmitter  59 ). 
     Baseband processor  58  may receive digital data that is to be transmitted from storage and processing circuitry  28  and may use path  46  and radio-frequency transceiver circuitry  60  to transmit corresponding radio-frequency signals. Radio-frequency front end  62  may be coupled between radio-frequency transceiver  60  and antennas  40  and may be used to convey the radio-frequency signals that are produced by transmitters  59  and  67  to antennas  40 . Radio-frequency front end  62  may include radio-frequency switches, impedance matching circuits, filters, and other circuitry for forming an interface between antennas  40  and radio-frequency transceiver  60 . 
     Incoming radio-frequency signals that are received by antennas  40  may be provided to baseband processor  58  via radio-frequency front end  62 , paths such as paths  54  and  56 , receiver circuitry in radio-frequency transceiver  60  such as receiver  61  at port  54  and receiver  63  at port  56 , and paths such as paths  44  and  46 . Baseband processor  58  may convert these received signals into digital data that is provided to storage and processing circuitry  28 . Baseband processor  58  may also extract information from received signals that is indicative of signal quality for the channel to which the transceiver is currently tuned. For example, baseband processor and/or other circuitry in control circuitry  42  may analyze received signals to produce bit error rate measurements, measurements on the amount of power associated with incoming wireless signals, strength indicator (RSSI) information, received signal code power (RSCP) information, signal-to-interference ratio (SINR) information, signal-to-noise ratio (SNR) information, channel quality measurements based on signal quality data such as Ec/lo or Ec/No data, etc. This information may be used in controlling which antenna(s) to use in device  10 . For example, a control algorithm running on control circuitry  42  may be used to switch a particular antenna into use for performing system acquisition operations or other functions based received signal strength information, signal power measurements associated with various channels, or other signal information. 
     Radio-frequency front end  62  may include a switch that is used to connect transceiver  57  to antenna  40 B and transceiver  63  to antenna  40 A or vice versa. The switch may be configured by control signals received from control circuitry  42  over path  50  and/or path  51 . Circuitry  42  may, for example, adjust the switch to select which antenna is being used to transmit radio-frequency signals (e.g., when it is desired to share a single transmitter in transceiver  60  between two antennas) or which antenna is being used to receive radio-frequency signals (e.g., when it is desired to share a single receiver between two antennas). 
     If desired, antenna selection may be made by selectively activating and deactivating transceivers without using a switch in front end  62 . For example, if it is desired to use antenna  40 B, transceiver  57  (which may be coupled to antenna  40 B through circuitry  62 ) may be activated and transceiver  63  (which may be coupled to antenna  40 A through circuitry  62 ) may be deactivated. If it is desired to use antenna  40 A, circuitry  42  may activate transceiver  63  and deactivate transceiver  57 . Combinations of these approaches may also be used to select which antennas are being used to transmit and/or receive signals. 
     Control operations such as operations associated with configuring wireless circuitry  34  to transmit or receive radio-frequency signals through a desired one of antennas  40  may be performed using a control algorithm that is implemented on control circuitry  42  (e.g., using the control circuitry and memory resources of storage and processing circuitry  28  and baseband processor  58 ). 
     With one suitable arrangement, which is sometimes described herein as an example, control circuitry  42  may be used in controlling antenna selection to support system acquisition operations. System acquisition operations may be performed on power up or in response to detection of an out-of-service condition. By selecting an appropriate antenna to use during system acquisition operations, the ability of device  10  to form a communications link with base station  21  may be enhanced, particularly in situations in which the performance of one or more of the antennas in device  10  has been disrupted. 
     Control circuitry  42  may be used in measuring how much power is associated with various frequencies (i.e., different channel numbers) in system  11 . Device  10  may, for example, use control circuitry  42  and wireless circuitry  34  to measure the signal power associated with each of a number of frequencies in a list of recently used frequencies (i.e., a channel history list). The signal strength at each frequency will be affected by factors such as the relative distance between device  10  and nearby base stations such as base station  21  of  FIG. 2 , the capabilities of each base station, and which antenna (e.g.,  40 A or  40 B or other suitable antenna) is being used in making the signal strength measurements. To ensure that functions such as system acquisition operations are performed satisfactorily, control circuitry  42  may select a suitable antenna to use in performing system acquisition operations based on information such as signal strength information that has been gathered using control circuitry  42  and one or more of the antennas in device  10 . 
       FIGS. 4 and 5  are flow charts of two illustrative ways in which device  10  may use control circuitry  42  to control the selection of a suitable antenna to use in performing system acquisition operations. 
     With the approach of  FIG. 4 , system acquisition operations may be initiated at step  100 . In particular, device  10  may use control circuitry  42  to initiate system acquisition operations following power-up of device  10  or following an out-of-service condition. 
     To determine which antenna to use in performing system acquisition operations, device  10  may evaluate received signal strength (e.g., the amount of power received by device  10  using transceiver  60 ) using antennas  40 . For example, in a configuration in which device  10  has first and second antennas  40 , device  10  may use the first antenna to make received signal power measurements and may use the second antenna to make received signal power measurements. These signal power measurements (or other suitable signal measurements) may then be used by control circuitry  42  in evaluating which of the antennas should be selected to use in performing system acquisition operations. If, for example, the first antenna is disrupted due to the presence of an external object in the vicinity of that antenna, the first antenna may not perform as well as the second antenna. In response to detecting that the second antenna is able to receive stronger signals than the first antenna, control circuitry  42  may select the second antenna to use in performing system acquisition operations. 
     In making the measurements of steps  102  and  104 , device  10  may evaluate signal strength (e.g., received signal power at device  10 ) for each frequency in a list of known frequencies (also sometimes referred to as channel numbers). The list of known frequencies may be a list of 5-10 frequencies or other suitable number of frequencies that have been most recently used by device  10  in conveying data traffic. Device  10  may maintain this type of frequency usage list during normal operation of device  10  in a cellular network. Maintaining a history of recently used frequencies may help device  10  rapidly identify a satisfactory frequency to use in communicating with the cellular network (e.g., as device  10  moves between cells in the wireless network). 
     As shown in  FIG. 4 , device  10  may gather information on the performance of the first antenna (i.e., the currently active antenna) during the operations of step  102 . In particular, device  10  may make signal measurements such as received signal power measurements with the current antenna for each frequency in the list of recently used frequencies. 
     Device  10  may then, at step  104 , gather information on the performance of the second antenna (sometimes referred to as the alternate antenna). In particular, device  10  may make signal measurements such as received signal power measurements with the alternate antenna for each frequency in the list of recently used frequencies. 
     After compiling information on the received signal power (or other signal strength measurement) for each of the recently used frequencies with both the current and alternate antennas, device  10  may select an appropriate antenna to use in performing system acquisition operations. In particular, during the operations of step  106 , device  10  may analyze the measured signal power data to determine which measured signal power is greatest. The largest measured signal power may be associated with the current antenna or the alternate antenna and will be associated with a given one of the most recently used frequencies. 
     During step  106 , after identifying the largest measured signal power and the corresponding frequency and antenna that were used in receiving signals at that power, device  10  may switch the appropriate antenna and frequency into use. For example, control circuitry  42  may configure transceiver circuitry  60  and/or switching circuitry  62  to route incoming signals from the antenna that is associated with the largest signal power to an active transceiver while adjusting the transceiver to operate at the frequency that is associated with the largest measured signal power. 
     During step  108 , device  10  may then use the selected antenna and frequency to perform system acquisition operations (i.e., to establish a wireless communications link between device  10  and base station  21 ). 
     At step  110 , the wireless link that was established during the operations of step  108  may be used in communicating data traffic between device  10  and base station  21  (e.g., data associated with a voice call or a data session). 
     Although described in the context of a device that contains two antennas, device  10  may, if desired, contain three or more antennas. In this type of arrangement, signal power measurements for each of the three or more antennas may be made before evaluating the signal power measurements to determine which of the antennas is to be used in performing system acquisition operations. 
     With the illustrative approach of  FIG. 5 , device  10  may evaluate the performance of alternate antennas only in the event that the current antenna is not performing satisfactorily. Device  10  may, for example, evaluate the performance of each antenna in turn until a satisfactory antenna is identified. 
     As shown in  FIG. 5 , device  10  may initiate system acquisition operations at step  112  (e.g., in response to a power up event or in response to detection of an out-of-service condition). At step  114 , device  10  may use the currently active antenna (e.g., a default antenna or most recently used antenna) to measure received signal strength (e.g., received signal power) for each frequency in a list of known (e.g., recently used) frequencies (e.g., 5-10 most recently used frequencies or other suitable number of most recently used frequencies). Device  10  may then identify which of the measured signal powers is greatest and may attempt to perform system acquisition operations using the frequency associated with the largest measured signal power. 
     Device  10  may determine whether system acquisition operations were successful at step  114 . If system acquisition operations are successful, device  10  may use a wireless communications link that is established during system acquisition operations to convey data traffic to and from base station  21  (step  120 ). 
     If, however, system acquisition operations were not successful using the current antenna, device  10  may, at step  116 , determine whether another of antennas  40  is available (i.e., device  10  can, in response to determining that system acquisition operations with the current antenna were unsuccessful, determine whether all of antennas  40  have been evaluated or whether antennas remain that have yet to be evaluated). If it is determined during the operations of step  116  that additional antennas are available for evaluation, device  10  may, at step  118 , switch the next available antenna into use using transceiver circuitry  60  and/or switching circuitry  62 . Processing may then loop back to step  114 , as indicated by line  126 , so that device  10  can evaluate the performance of the new current antenna. 
     If it is determined at step  116  that no additional antennas are available for testing (i.e., if device  10  has already made received signal power measurements using each of the antennas in device  10 ), device  10  can, at step  122 , direct transceiver circuitry  60  and/or switching circuitry  62  to switch a default antenna into use. The default antenna may be, for example, the lower antenna in device  10  of  FIG. 1 . System acquisition operations may be performed using the default antenna during step  122 . If system acquisition operations during step  122  are successful, device  10  may use the communications link that was established during the system acquisition operations to carry normal data traffic (step  120 ). If system acquisition operations during step  122  are unsuccessful, device  10  may enter an out-of-service condition (step  124 ). Following the out-of-service condition or in response to other events such as a power-up event, device  10  can initiate system acquisition operations (step  112 ). 
     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: 20111003
Publication Date: 20141028
Grant Date: 20141028
Priority Date: 20111003
Inventors: NUKALA GAURAV
SEBENI JOHNSON O.
XING LONGDA
RAMASAMY VENKATASUBRAMANIAN
SANE SACHIN J.
SHAMIM TAHIR
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W48/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W48/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/318", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W48/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W48/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/382", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W48/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/0057", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/0077", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W48/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/382", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/318", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 47116303