PATENT DOCUMENT

Publication Number: US-9509343-B2
Application Number: US-201514962084-A
Country: US
Kind Code: B2

Title: Antenna switching system with adaptive switching criteria

Abstract:
Apparatuses may be provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry coupled to multiple antennas. Signal strength measurements may be gathered using the antennas and corresponding signal strength difference measurements may be produced to reflect which of the antennas is exhibiting superior performing. Information may be gathered relating to the fading environment of the communications circuitry, such as whether the wireless communications circuitry is transitioning between a fast fading environment and a slow fading environment. For example, the wireless communications circuitry may further include a satellite positioning system receiver or an accelerometer, which may be used in gathering the information. The difference measurements may be filtered and compared to antenna switching criteria such as antenna switching thresholds. An antenna switching threshold may be adjusted in real time based at least in part on the gathered information.

Claims:
What is claimed is: 
     
       1. An apparatus, comprising:
 control circuitry configured to switch a selected one of a first antenna and a second antenna into use for wireless communications traffic for the apparatus; 
 wherein the control circuitry is configured to cause the apparatus to:
 obtain a difference measurement reflecting how much received antenna signal strength differs between the first antenna and the second antenna; 
 filter the difference measurement; 
 gather information relating to whether the apparatus is operating in a fast fading environment or a slow fading environment; and 
 apply antenna switching criteria to the filtered difference measurement to determine whether to switch the first antenna or the second antenna into use for the wireless communications traffic, wherein the antenna switching criteria are based at least in part on the gathered information. 
 
 
     
     
       2. The apparatus defined in  claim 1 , wherein the gathering the information further comprises:
 gathering information indicating whether the apparatus is transitioning between a fast fading environment and a slow fading environment. 
 
     
     
       3. The apparatus defined in  claim 1 , further comprising:
 a satellite positioning system receiver; 
 wherein the gathering the information comprises producing movement data based at least in part on signals from the satellite positioning system receiver. 
 
     
     
       4. The apparatus defined in  claim 1 , further comprising:
 an accelerometer; 
 wherein the gathering the information comprises producing movement data based at least in part on signals from the accelerometer. 
 
     
     
       5. The apparatus defined in  claim 1 , wherein the applying the antenna switching criteria comprises comparing the filtered difference measurement to a threshold. 
     
     
       6. The apparatus defined in  claim 5 , further comprising adjusting the threshold in real time based at least in part on the gathered information. 
     
     
       7. The apparatus defined in  claim 6 , wherein the adjusting the threshold in real time comprises raising the threshold in response to the gathered information indicating that the apparatus is transitioning from a fast fading environment to a slow fading environment. 
     
     
       8. An apparatus, comprising:
 control circuitry configured to switch a selected one of a first antenna and a second antenna into use for wireless communications traffic for the apparatus; 
 wherein the control circuitry is configured to cause the apparatus to:
 obtain a difference measurement reflecting how much received antenna signal strength differs between the first antenna and the second antenna; 
 filter the difference measurement to produce one or more filtered difference measurements; 
 determine whether one of the first antenna and the second antenna has a lower maximum transmit power limit than the other of the first antenna and the second antenna; and 
 apply antenna switching criteria to the filtered difference measurements to determine whether to switch the first antenna or the second antenna into use for the wireless communications traffic, wherein the antenna switching criteria are based at least in part on whether one of the first antenna and the second antenna has a lower maximum transmit power limit. 
 
 
     
     
       9. The apparatus defined in  claim 8 , wherein the applying the antenna switching criteria comprises comparing the filtered difference measurements to a threshold. 
     
     
       10. The apparatus defined in  claim 9 , further comprising adjusting the threshold in real time based at least in part on information relating to whether the apparatus is operating in a fast fading environment or a slow fading environment. 
     
     
       11. The apparatus defined in  claim 8 , wherein the filtering the difference measurement comprises applying first and second filters with different filtering speeds to the difference measurement to produce respective first and second filtered difference measurements. 
     
     
       12. The apparatus defined in  claim 11 , wherein the applying the antenna switching criteria comprises comparing the first filtered difference measurements to a first threshold and comparing the second filtered difference measurements to a second threshold that is different than the first threshold. 
     
     
       13. The apparatus defined in  claim 12 , wherein the control circuitry is further configured to cause the apparatus to adjust the second threshold in real time. 
     
     
       14. The apparatus defined in  claim 13 , wherein the control circuitry is further configured to cause the apparatus to compute how much variation is exhibited between the first filtered difference measurements and the second filtered difference measurements, wherein adjusting the second threshold comprises adjusting the second threshold in response to the computed variation. 
     
     
       15. A non-transitory computer readable medium comprising software instructions executable by a processor of an apparatus, the software instructions configured to cause the apparatus to:
 obtain a difference measurement reflecting how much received antenna signal strength differs between a first antenna and a second antenna; 
 filter the difference measurement to produce one or more filtered difference measurements; 
 determine whether one of the first antenna and the second antenna has a lower maximum transmit power limit than the other of the first antenna and the second antenna; and 
 apply antenna switching criteria to the filtered difference measurements to determine whether to switch the first antenna or the second antenna into use for wireless communications traffic, wherein the antenna switching criteria are based at least in part on whether one of the first antenna and the second antenna has a lower maximum transmit power limit. 
 
     
     
       16. The non-transitory computer readable medium defined in  claim 15 , wherein the applying the antenna switching criteria comprises comparing the filtered difference measurements to a threshold. 
     
     
       17. The non-transitory computer readable medium defined in  claim 16 , wherein the software instructions are further configured to cause the apparatus to:
 adjust the threshold in real time based at least in part on information relating to whether the apparatus is operating in a fast fading environment or a slow fading environment. 
 
     
     
       18. The non-transitory computer readable medium defined in  claim 15 , wherein the filtering the difference measurement comprises applying first and second filters with different filtering speeds to the difference measurement to produce respective first and second filtered difference measurements. 
     
     
       19. The non-transitory computer readable medium defined in  claim 18 , wherein the applying the antenna switching criteria comprises comparing the first filtered difference measurements to a first threshold and comparing the second filtered difference measurements to a second threshold that is different than the first threshold. 
     
     
       20. The non-transitory computer readable medium defined in  claim 19 , wherein the software instructions are further configured to cause the apparatus to adjust the second threshold in real time.

Description:
CONTINUATION DATA 
     This application is a continuation of U.S. patent application Ser. No. 14/645,501, filed Mar. 12, 2015, and entitled “Antenna Switching System with Adaptive Switching Criteria,” which is a continuation of U.S. Pat. No. 9,002,283, filed Aug. 1, 2011, having the same title, both of which are incorporated herein by reference in their entirety as though fully and completely set forth herein. 
    
    
     This relates generally to wireless communications circuitry, and more particularly, to electronic devices that have wireless communications 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 communications 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. 
     Antenna performance affects the ability of a user to take advantage of the wireless capabilities of an electronic device. If antenna performance is not satisfactory, calls may be dropped or data transfer rates may become undesirably slow. To ensure that antenna performance meets design criteria, it may sometimes be desirable to provide an electronic device with multiple antennas. In some situations, control circuitry within a device may be able to switch between antennas to ensure that an optimum antenna is being used to handle call traffic. 
     The ability to switch to an optimum antenna rapidly can help ensure that wireless communications are not disrupted. At the same time, accuracy should not be sacrificed. In real-world environments a variety of factors may affect antenna performance, such as path loss fluctuations and antenna blocking events involving the momentary presence of external objects over part of an antenna. If care is not taken, antenna switching response may be rapid but inaccurate or accurate but slow. 
     It would therefore be desirable to be able to provide improved ways for electronic devices such as devices with multiple antennas to determine how to switch between antennas during operation. 
     SUMMARY 
     Electronic devices may be provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry coupled to multiple antennas. 
     Signal strength measurements may be gathered using the antennas and a corresponding signal strength difference measurement may be produced. The difference measurement may reflect whether one of the antennas is exhibiting superior performance to the other. If it is determined that an alternate antenna is performing better than a currently used antenna, the alternate antenna may be switched into use. 
     Signal strength difference measurements may be processed using a control algorithm in the electronic device to determine whether or not to switch antennas. The signal strength difference measurements may be filtered using time-based averaging filters with different speeds. Corresponding filtered difference measurements may be compared to antenna switching criteria such as antenna switching thresholds. 
     The electronic device may be operated in environments in with the difference measurements fluctuate slowly (sometimes referred to as slow fading environments) and may be operated in environments in which the difference measurements fluctuate more rapidly (sometimes referred to as fast fading environments). 
     The averaging filters may include a slow filter and a fast filter. The slow filter may average the difference measurements over a relatively long time period to produce accurate results in both slow fading and fast fading environments The fast filter may average the difference measurements over a shorter time period to allow the control algorithm to respond more rapidly to difference measurement fluctuations than is possible using the slow filter alone. 
     The output of the slow filter and the output of the fast filter may be compared to respective slow filter and fast filter threshold values to determine whether or not to request that an alternative antenna be switched into use in place of the currently active antenna. 
     The fast filter threshold may be adjusted in real time based on computations of how much variation is exhibited as a function of time between the filtered difference measurements In fast fading environments in which the output of the last filter is close to that of the slow filter, the fast filter threshold can be reduced to allow increased antenna switching speed using the fast filter branch of the control algorithm. In slow fading environments in which the output of the fast filter and the slow filter differ, the fast filter threshold can be increased to ensure that the fast-filter branch of the control algorithm does not produce inaccurate antenna switching requests. To ensure that the device responds appropriately when transitioning from fast fading to slow fading environments, information on device movement or other data may be used in making threshold adjustments. 
     Further features of the inventions its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with wireless communications circuitry 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 communications 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. 
         FIG. 4  is a flow chart of illustrative operations involved in controlling the operation of an electronic device with multiple antennas to ensure an optimum antenna is used in accordance with an embodiment of the present invention. 
         FIG. 5  is a graph showing how antenna switching criteria may be applied to measured antenna signal strengths to determine when to switch antennas in an environment with a relatively small difference in received signal strength between antennas and relatively slow signal strength fluctuations in accordance with an embodiment of the present invention. 
         FIG. 6  is a graph showing how antenna switching criteria may be applied to measured antenna signal strengths to determine when to switch antennas in an environment with a relatively small difference in signal strength between antennas and relatively rapid signal strength fluctuations in accordance with an embodiment of the present invention. 
         FIG. 7  is a graph showing how antenna switching criteria may be applied to measured antenna signal strengths to determine when to switch antennas in an environment with a relatively large difference in signal strength between antennas in accordance with an embodiment of the present invention. 
         FIG. 8  is a graph showing how antenna switching criteria may be adjusted based on external input such as movement data from a satellite positioning system receiver or a sensor in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. The wireless communications circuitry may include multiple antennas arranged to implement an antenna diversity system. 
     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, 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 covets 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 tear 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 of 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 ). 
     It 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 art 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. 
     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. 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, accelerometers (motion sensors), ambient light sensors, and other 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 communications circuitry  34  may include radio-frequency (RE) 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 communications 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 communications 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 communications 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 . These antennas 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 diversity control 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.) end 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, 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 to circuitry  28  and/or processor  58  and, in response, storage arid 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 . 
     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  20  more radio-frequency transceivers such as transceivers  57  and  63  (e.g., one or mare 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  67 ). 
     Baseband processor  58  may receive digital data that is to be transmitted from storage and processing circuitry  26  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 based on signal strength data measurements such as these. 
     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 . 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 ). 
     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 objects that interfere with proper antenna operation, or due to other factors (e.g., device orientation relative to its surroundings, etc.). To ensure that an optimum antenna is used, device  10  may monitor the signals received on each antenna and can switch an appropriate antenna into use for handling the wireless communications traffic for device  10  based on the monitored signals. 
     An antenna switching algorithm that runs on the circuitry of device  10  can be used to automatically perform antenna switching operations based on the evaluated signal quality of received signals. The antenna switching algorithm may direct device  10  to select a new antenna for use in handling wireless signals (e.g., cellular telephone signals or other wireless traffic) whenever antenna performance on the currently used antenna has degraded relative to an available alternate antenna or when other antenna switching criteria have been satisfied. With this type of arrangement, it is not necessary to simultaneously use multiple antennas and associated circuits for handling wireless signals, thereby minimizing power consumption. 
     Arrangements in which device  10  has a first antenna and a second 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. 
     In performing antenna switching operations, device  10  may measure signal strength using any suitable signal quality metric. As an example, device  10  may measure received signal power, may gather received signal strength indicator (RSSI) information, may gather received signal code power (RSCP) information, or may gather other information on received signal strength. 
     Received signal strength information may be gathered for each antenna in device  10 . For example, if device  10  includes upper and lower antennas, the signal strength for signals received in both the upper and lower antennas can be gathered. The received signal strengths of the upper and lower antennas may be processed by an antenna switching control algorithm. The switching algorithm may use switching criteria and the measured received antenna signal strengths to determine in real time whether the antenna assignments in device  10  should be switched. If the switching criteria are satisfied, the antennas can be swapped. If, for example, it is determined by comparing received signal strength data to threshold settings that the lower antenna is being blocked, the upper antenna may be switched into use in place of the lower antenna. 
     To ensure that device  10  remains responsive during a variety of environmental conditions, switching criteria (i.e., one or more switching thresholds or other switching algorithm parameters) may be adjusted in real time. Arrangements in which device  10  adjusts the value of one or more thresholds based on measured values of received signal strength may sometimes be referred to as adaptive threshold arrangements. 
     To suppress noise while ensuring rapid response to changing conditions, time-based averaging filters may be applied to received signal strength measurements. Multiple filters may be used, each with different associated filtering characteristics. For example, there may be two, three, or more than three filters each of which has different associated filtering characteristics. With one suitable arrangement, which may sometimes be described herein as an example, device  10  may use a pair of time-based filters. 
     The time-based filters may average signals over relatively longer time periods (sometimes referred to as slow filtering) and relatively shorter time periods (sometimes referred to as fast filtering). Slow filters produce accurate data, but do not respond quickly to abrupt change in true signal strength. Fast filters respond quickly. However, because fast fitters average signals over shorter time windows than slow filters, fast-filtered signal strength measurements tend to be noisier than slow-filter signal strengths. It may therefore be necessary to compare fast-filtered signal measurements to larger threshold values than slow-filtered signal measurements to avoid false alarms (i.e., to avoid situations in which antennas are switched at inappropriate times). 
     If desired, input from an external source may be used in making an antenna switching decision. Input from an external source may include, for example, information from one or more sensors in device  10 . As an example, data from an accelerometer in input-output devices  32  may be used to produce information on the motion of device  10 . Accelerometer data may be used to determine whether device  10  is in a rapidly moving environment (e.g., within a car or other moving vehicle) or has suddenly stopped moving. Satellite navigation system receiver data such as Global Positioning System (GPS) data can also be used to determine the velocity of device  10  (i.e., whether device  10  is moving or is stationary). Information on device movement and other external data may be used to adjust threshold values and other antenna switching criteria in real time. For example, motion information from a GPS receiver or accelerometer or other data may be used to ensure that device  10  adjusts an antenna switching threshold quickly when device  10  comes to rest after being in motion. 
     A flow chart of illustrative steps involved in controlling antenna assignments in device  10  is shown in  FIG. 4 . The example of  FIG. 4  involves a configuration for device  10  that has two antennas (e.g., upper and lower antennas in regions  22  and  24 ). 
     During the operations of step  100 , signal strength measurements may be made for each of the two antennas. In particular, a signal strength RC may be measured for a first of the antennas (i.e., the current antenna being used to handle wireless traffic for device  10 ) and a signal strength RA may be measured for a second of the antennas (i.e. an alternate antenna that is available to take the place of the current antenna). The difference between these signals strengths (i.e., signal strength ΔR=RA−RC) may then be computed. 
     When receiver diversity functions are available in wireless circuitry  34  (i.e., in configurations for device  10  in which the circuitry baseband processor  58  supports receive diversity operations), receivers  65  and  61  and corresponding first and second antennas can be used in receiving signals. In situations in which receiver diversity functions are unavailable, only one of the antennas in device  10  (i.e., the current antenna) is generally used at a time to transmit and receive wireless communications traffic. To determine the signal strength for received signals on the other antenna (i.e. the alternate antenna), device  10  may sample the received signal strength on the alternate antenna by momentarily using a receiver that is associated with the alternate antenna to gather and process incoming signals or by momentarily switching the alternate antenna into use to gather a signal strength sample without disrupting the ability of the currently active antenna to handle its wireless traffic. 
     The operations of  FIG. 4  such as signal measurement and signal processing activities may be performed using wireless circuitry  34  (e.g., transceiver circuitry  60 ) and control circuitry  42  (e.g., baseband processor  58  and/or circuitry  28 ). When the computed signal strength difference between the antennas indicates that the alternate antenna is receiving weaker signals than the current antenna or is receiving signals that are only slightly stronger than the current antenna, device  10  may maintain the current antenna assignments in device  10 . When the computed signal strength difference between the antennas indicates that the alternate antenna is switched into use in place of the current antenna. 
     The difference between the signal strengths of the received signals for the antennas (i.e., difference measurement Δ, which reflects how much received antenna signal strength differs between the two antennas) may be time averages (time filtered) using time-based filters with different associated time windows (averaging periods). Any suitable filtering scheme may be used (e.g., a linear average, a weighted averaged that favors more recent activity, finite impulse response (FIR) or infinite impulse response (IIR) filters, etc.). As shown in  FIG. 4 , two different filters may be applied to the measured ΔR data. A slow filter (i.e., a filter that averages measured ΔR values over a relatively longer time period such as a time period of 0.5 to 2 seconds or other suitable time period) may be applied at step  102 . Application of the slow filter to the raw measured values of ΔR produced a slow-filtered version of ΔR at the output of the slow filter. A fast filter (i.e., a filter that averages measured ΔR values over a relatively shorter time period such as a time period of 50-150 ms or other suitable time period) may be applied at step  104 . Application of the fast filter to the measured difference values ΔR produces a fast-filtered version of ΔR at the output of the fast filter. 
     Antenna switching criteria may be applied to the slow-filtered version of the measured ΔR data during the operations of step  112 . For example, the slow-filter version of the measured ΔR data may be compared to a threshold (sometimes referred to as a slow threshold or slow-filter threshold) at step  112 . Antenna switching criteria may also be applied to the fast-filtered version of the measured ΔR data during the operations of step  110 . For example, the fast-filter version of the measured ΔR data may be compared to a threshold (sometimes referred to as a fast threshold or fast-filter threshold) at step  110 . 
     The outcome of the comparison operations of steps  110  and  112  may be used to generate corresponding requests to switch the antennas. For example, if the fast-filtered version of ΔR is greater than a fast-filter threshold Δfast, a request to switch antennas may be generated at step  110 . If the slow-filtered version of ΔR is greater than the slow-filter threshold Δslow, a request to switch antennas may be generated at step  112 . The requests that are generated may be represented by Boolean values (e.g., a logical “1” may represent a request to swap antennas and a logical “0” may represent a desire to maintain the current set of antenna assignments). 
     During the operations of step  114 , device  10  can use control circuitry  42  to issue corresponding commands to wireless circuitry  34 . With one suitable arrangement, the requests produced at steps  110  and  112  may be processed using a logical “OR” function. If no request to swap antennas was generated at step  110  and if no request to swap antennas was generated at step  112 , device  10  may decline to swap antennas at step  114 . If either the fast-threshold comparison operations of step  110  or the slow-threshold comparison operations of step  112  indicate that the antennas are to be swapped (or if the operations of both step  110  and step  112  indicate that the antennas should be swapped), device  10  may, at step  114 , switch antennas so that the current antenna is replaced with the alternate antenna. Following switching, the newly selected antenna may be used to receive and/or transmit radio-frequency signals for device  10 . In situations in which receiver diversity is available in device  10 , device  30  may use both antennas to receive signals while using the newly selected antenna for transmission. Device  10  way continuously use the steps of  FIG. 4  to ensure that an optimum antenna is switched into use at all times. 
     In situations in which the magnitude of difference signal ΔR varies slowly, the fast-filtered output of step  102  may closely track ΔR. To avoid premature antenna switching when the fast-filtered output rises quickly due to a rapid upwards fluctuation in ΔR, it may be desirable to set Δfast to a higher value than Δslow. For example, the default (unadjusted) value for Δfast may be 10 dB (as an example) and the (typically fixed) value of Δslow may be 3 dB (as an example). In general, Δfast and Δslow may have values of about 0.5 to 13 dB (as examples). 
     In environments in which the values of the slow-filtered and fast-filtered versions of ΔR are close to one another the use of the fast-filter branch of the process shown it  FIG. 4  will generally yield antenna switching requests that are comparable to antenna switching requests produced using the slow-filtered branch of the process shown in  FIG. 4 . In this type of situation, it may be desirable to adaptively lower the value of Δfast. For example, it may be desirable to lower Δfast to a level equal to or comparable to Δslow. Lowering Δfast in this way allows device  10  to respond more quickly to moderately sized variations in ΔR than would otherwise be possible. 
     To allow the fast threshold Δfest or other antenna switching criteria to be adjusted, it may be desirable to determine the variation (V) between the slow-filtered and fast-filtered versions of ΔR. As shown in  FIG. 4 , the variation between the slow-filtered and fast-filtered versions of ΔR may be computed at step  106 . Any suitable metric may be used to gauge the amount of variation between the slow-filtered and fast-filtered versions of ΔR (e.g., standard deviation, variance, a variation value that is based on a standard deviation calculation in which the average of the slow-filtered data serves as the mean, a sum of squares, etc.) 
     When variation V is small, the fast-filtered data is close in magnitude to the slow-filtered data (i.e., the fast-filtered data is accurate and will not result in false alarms and premature switching). It is therefore acceptable to make switching decisions at step  110  based on the fast-filtered data. This may be accomplished by lowering the value of Δfast as a function of reduced values of V. When variation V is large, potentially inaccurate switching decisions based on fast-filtered data may be suppressed by raising Δfast. 
     The variation V between the slow-filtered and fast-filtered data tends to be low whenever the value of ΔR varies quickly (sometimes referred to as fast fading). Device  30  may be subjected to relatively rapid variations in ΔR when moving quickly (e.g., when device  10  is located in a moving vehicle). 
     The variation V between the slow-filtered and fact-filtered data tends to be high whenever the value of ΔR varies slowly (sometimes referred to as a slow fading environment) Device  10  may be subject to slow fading when device  10  is moving slowly or is stationary. 
     After sustained operation in a fast fading environment such as the interior of a moving automobile, the value of variation V will generally be low and Δfast will have been reduced to a correspondingly low value. If the automobile stops suddenly, device  10  may rapidly transition from a fast fading to a slow fading environment. To minimize false alarms and undesired antenna switching, it may be desirable to automatically increase the value of Δfast whenever sensors, satellite navigation system signals (GPS data) or other data reveals that device  10  has transitioned from a fast fading to a slow fading environment (e.g., when GPS or sensor data detects that device  10  has transitioned from a moving to a stationary environment). The use of GPS data, sensor data, and other data to serve as input to threshold adjustment step  108  is illustrated by line  116  of  FIG. 4 . 
     Adjustments to threshold Δfast or other antenna switching criteria adjustments during step  108  may be made in a stepwise fashion (e.g., by returning Δfast immediately to a default higher Δfast value), may be made relatively slowly (e.g., without influence from input  116 ), or may be made at a moderate speed (e.g., more slowly than an immediate change but, by using input  116 , more quickly than would otherwise be possible). 
     When making comparisons between antennas in steps  110  and  112 , it may be desirable to take into account different antenna receiving efficiencies and maximum transmit power limits. For example, if the transmit efficiency Lot a first antenna is 1 dB larger than the receive efficiency on a second antenna, a 1 dB compensating offset may be added to the threshold comparisons to ensure that the favorable transmit performance of the first antenna is taken into account. As another example, if the maximum transmit power for the second antenna is 3 dB lower than the maximum transmit power for the first antenna (e.g., due to a need to comply with specific absorption rate limits), this  3  dB performance limit may be taken into account when determining whether it would be favorable to witch to use of the second antenna. 
     The graph of  FIG. 5  illustrates how the operations of  FIG. 4  may be used to switch antennas in device  10  when device  10  is in a slow fading environment (e.g., an environment where AR changes with a time constant of about 0.4 to 0.5 seconds) and when the magnitude of the change in ΔR actual (the actual value of the relative performance of the antennas in device  10 ) during an antenna blocking event is relatively small (e.g., less than 10 dB). During times between t 0  and t 1 , the current antenna is not blocked and is performing 5 dB better than the alternate antenna. At time t 1 , the current antenna is blocked by an external object. As result, at time t 1 , the alternate antenna is performing 4 dB better than the current antenna. 
     To determine whether or not to switch from the current antenna to the alternate antenna, device  10  applies a slow filter to signal ΔR to produce slow-filtered ΔR and applies a fast filter to signal ΔR to produce fast-filtered ΔR. Because device  10  in the  FIG. 5  scenario is in a slow fading environment, fast-filtered ΔR closely tracks signal ΔR, whereas between times t 0  and t 1 , slow-filtered ΔR is close to the actual value of ΔR actual. 
     Because device  10  is being operated in a slow fading environment, the variance V between slow-filtered ΔR and fast-filtered ΔR is large. During the operations of step  108 , device  10  therefore maintains threshold Δfast at its nominal (default) value of 10 dB. Because Δfast remains at 10 dB, device  10  does not exhibit a false alarm at time tf (i.e., the antennas axe not switched at time tf, because fast-filtered ΔR is less than Δfast at time tf). 
     The abrupt transition in ΔR (actual) at time t 1  causes signal ΔR to increase. Fast-filtered ΔR follows ΔR, but, because Δfast is set to the relatively high value of 10 dB, the comparison operations of step  110  do not result in a request from the fast branch of the control algorithm to swap antennas. 
     After time t 1 , the value of slow-filtered ΔR rises until this value exceeds Δslow (3 dB in this example) at tine t 2 . When slow-filtered ΔR exceeds Δslow, the comparison operations of step  112  generate a request to swap antennas. Device  10  therefore swaps antennas at time t 2  (step  114  of  FIG. 4 ). Then the alternate antenna is switched into use in place of the current antenna at time t 2 , the ability of device  10  to properly receive and transmit signals is restored. At times t greater than time t 2 , the current antenna is performing 4 dB better than the alternate antenna and no switching is taking place. 
     The graph of  FIG. 6  illustrates how device  10  may respond to an antenna blocking event in a fast fading environment (e.g., an environment where ΔR changes with a time constant of about 2-10 milliseconds) where the change in magnitude of ΔR actual during the antenna blocking event is relatively small (e.g., less than 10 dB). Because device  10  is being operated in a fast fading environment in the  FIG. 6  example, fast-filtered a does not track ΔR, but rather represents an accurate average of ΔR that is close in magnitude to ΔR actual. In this situation, the variation V between slow-filtered ΔR and fast-filtered ΔR is small. When V is small, device  10  adaptively adjusts Δfast, as shown by the decreasing value of Δfast as a function of time in the graph of  FIG. 6 . The decreased value of Δfast helps device  10  switch antennas quickly based on decisions from the fast-filter branch of the control algorithm. 
     At time t 1 , the current antenna is blocked, causing ΔR actual to increase to 4 dB (indicating that the alternate antenna is performing 4 dB better than the current antenna). Slow-filtered ΔR does not respond quickly to the change in ΔR following time t 1 . However, fast-filtered ΔR responds quickly. At time t 2  fast-filtered ΔR exceeds threshold Δfast and, in response, the alternate antenna is switched into use in place of the current antenna. 
       FIG. 7  illustrates the performance of device  10  in a scenario in which an antenna blocking event causes a relatively large change (more than 10 dB) in ΔR actual. In the  FIG. 7  example, device  10  is being operated in a slow fading environment. Due to the slow fading environment, slow-filtered ΔR and fast-filtered ΔR differ substantially at times t before t 1 . As a result, variation V is relatively high and Δfast remains at its nominal value of 10 dB. At time t 1 , the current antenna is blocked. Slow-filtered ΔAR responds slowly and does not exceed Δslow. However, fast-filtered ΔR responds quickly. At time t 2 , fast-filtered ΔR exceeds Δfast (e.g., 10 dB) and device  10  swaps the alternate antenna into use in place of the current antenna. The  FIG. 7  example shows how the fast-filter branch of the control algorithm can issue accurate antenna switching requests even in a slow fading environment, provided that the change in ΔR actual during an antenna blocking event is larger than the default value of Δfast. 
     As illustrated in the  FIG. 6 and 7  examples, the presence of a fast filter branch in the antenna switching control algorithm allows device  10  to switch optimum antenna into use more rapidly than would be possible in a device that only contained a slow branch. When conditions allow (e.g., in the fast fading environment of  FIG. 6 ), the value of the fast threshold Δfast may be reduced to increase the rate at which device  10  can respond to momentary antenna degradation events. 
       FIG. 8  illustrates the performance of device  10  in a scenario in which device  10  is initially operated in a fast fading environment and is subsequently operated in a slow fading environment. This type of scenario may arise, for example, when a user is using device  10  in a moving automobile that stops (at time t 3 ). During operation in the fast-fading environment, Δfast is adaptively reduced from its default value of 10 dB to its minimum value of 3 dB. 
     At time t 3 , the environment in which device  10  is operating changes from a fast fading environment to a slow fading environment. Device  10  can detect this change in operating environment at time t 3  using GPS data, accelerometer data, or other external input. In response, device  10  can increase Δfast to prevent false alarms (i.e., inappropriate antenna triggering requests due to situations in which fast-filtered ΔR exceeds the reduced 3 dB Δfast threshold). As shown by line  200 , for example, Δfast may be immediately restored to its default value of 10 dB at time t 3 . As shown by line  202 , Δfast may, if desired, be restored gradually (without feedback from input  116 ). Another possibility, which is illustrated by line  204  involves increasing the speed at which Δfast is restored to an appropriate level beyond the relatively slow speed of line  202 . Line  204  may correspond to a scheme in which the speed of computing variation V is momentarily increased in response to detection of the transition between the fast fading and slow fading regimes. In the  FIG. 8  example, use of the threshold adaptation scheme associated with line  202  may result in an undesired antenna switching event at time t 4 . This can be avoided by using an accelerated adoption scheme such as the scheme associated with line  200  or the scheme associated with line  204 . 
     If desired, an optional timer operation may be incorporated into the control algorithm. Using a timer, the control algorithm on device  10  may impose a requirement for antenna switching that a particular threshold condition be met a certain number of tines pet unit time. The timer may, for example, be incorporated into the slow filter branch of the control algorithm (and/or the fast filter branch of the control algorithm). Using the timer, a tradeoff may be made between the size of the antenna switching threshold such as the size of Δslow for the slow filter branch (or the size of Δfast for the fast filter branch) and the number of times per unit time that the threshold condition must be met. If, for example, the threshold is required to be exceeded 5 times per every 15 ms, then the magnitude of the threshold may be lowered relative to the threshold value that would be used in the absence of the timer. The use of a timer limit that requires the threshold to be exceeded 5 times per every 15 ms is merely illustrative. Other suitable limit values that specify how many times per unit time the threshold must be exceeded before antenna switching operations are performed may be used if desired. Moreover, timer limits or other time-based criteria may be adaptively adjusted in real time (instead of or in addition to making adaptive adjustments to threshold values such as Δslow and Δfast). Optional timing criteria such as these may be applied and adjusted (and optional adaptive adjustments to threshold values such as Δslow and Δfast may be made) during the operations of steps  110  and  112  of  FIG. 4   
     Although the illustrative antenna switching operations of  FIG. 4  were described in the context of an arrangement that has two filters with different filtering speeds (e.g., slow and fast), more time-averaging filter branches may be incorporated into the control algorithm if desired. For example, the control algorithm may include three branches with respective slow, medium, and fast filtering characteristics. 
     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: 20151208
Publication Date: 20161129
Grant Date: 20161129
Priority Date: 20110801
Inventors: MUJTABA SYED A.
SONG KEE-BONG
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W64/006", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0064", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/0808", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B7/0834", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/1027", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/082", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S19/13", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/082", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W64/006", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0834", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S19/13", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W84/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0808", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0064", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B7/0808", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/1027", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/7115", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/0834", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 46634565