PATENT DOCUMENT

Publication Number: US-8948310-B2
Application Number: US-55407709-A
Country: US
Kind Code: B2

Title: Use of RDS data to select matching network

Abstract:
Devices and methods for dynamically selecting a matching network for an antenna are provided. In one example, an electronic device capable of selecting such a matching network may include an antenna, several selectable matching networks, a radio receiver, and matching network control circuitry. The radio receiver may couple to the antenna via one of the selectable matching networks to receive a radio signal with both an analog and digital component. The matching network control circuitry may select the matching network from among the several selectable matching networks based at least in part on a characteristic of the digital component of the radio signal.

Claims:
What is claimed is: 
     
       1. A method comprising:
 receiving a radio broadcast signal from an antenna into a radio receiver via one of a plurality of selectable matching networks, the antenna comprising a flexible conductor, a network profile of the antenna varying when the flexible conductor is physically reconfigured; 
 decoding an analog audio signal and a digital signal from the radio broadcast signal using the radio receiver; 
 evaluating a signal quality of the digital signal and a signal quality of the analog audio signal or of the radio broadcast signal using the radio receiver; and 
 selecting another one of the plurality of selectable matching networks when the signal quality of the digital signal, the signal quality of the analog audio signal, or the signal quality of the radio broadcast signal falls beneath a threshold using matching network control circuitry; 
 wherein the signal quality of the digital signal is evaluated based at least in part by applying a discrete value to a signal characteristic of the digital signal, and wherein the other one of the plurality of selectable matching networks is selected when the discrete value falls beneath the threshold. 
 
     
     
       2. The method of  claim 1 , wherein the signal quality of the digital signal is evaluated based at least in part on a locking speed of the digital signal; a completeness of the digital signal; a block error rate of the digital signal; or a confidence of the digital signal; or any combination thereof. 
     
     
       3. The method of  claim 1 , wherein the other one of the plurality of selectable matching networks is selected when the signal quality of the digital signal falls beneath the threshold, wherein the threshold is lower when the digital signal indicates that the analog audio signal comprises spoken audio than when the digital signal indicates that the analog audio signal comprises music. 
     
     
       4. An electronic device comprising:
 a headphone jack configured to connect to a wired headset; 
 a radio receiver configured to decode an audio signal and a non-audio signal from a broadcast radio signal; 
 matching network circuitry electrically disposed between the headphone jack and the radio receiver and configured to selectably function as one of a plurality of matching networks between the wired headset and the radio receiver, such that the radio receiver is capable of receiving the broadcast radio signal when the wired headset is connected to the headphone jack, a network profile of the wired headset varying when a flexible conductor in the wired headset is physically reconfigured; 
 matching network control circuitry configured to supply a control signal to the matching network circuitry to cause the matching network circuitry to function as the one of the plurality of matching networks; and 
 data processing circuitry configured to control the matching network control circuitry based at least in part on a quality of the non-audio signal and the audio signal, wherein the quality of the audio signal is determined by evaluating a received signal strength indicator of the broadcast radio signal; a signal-to-noise ratio of the broadcast radio signal; or the presence of multipath characteristics in the broadcast radio signal; or any combination thereof; 
 wherein the matching network control circuitry comprises common matching network circuitry coupled to one or more switches, wherein the one or more switches are coupled to a plurality of matching network elements, wherein the matching network control circuitry is configured to function as the one of the plurality of matching networks when a corresponding one of the plurality of matching network elements is coupled to the common matching network circuitry, and wherein the control signal is configured to cause the one or more switches to couple the one of the plurality of matching network elements to the common matching network circuitry. 
 
     
     
       5. The electronic device of  claim 4 , wherein the plurality of matching networks comprises a first matching network configured to transmit the broadcast radio signal when the broadcast radio signal is in a first radio frequency band and a second matching network configured to transmit the broadcast radio signal when the broadcast radio signal is in a second radio frequency band. 
     
     
       6. The electronic device of  claim 4 , wherein the matching network circuitry comprises a first switch configured to electrically couple the headphone jack to one of the plurality of matching networks and a second switch configured to electrically couple the one of the plurality of matching networks to the radio receiver, wherein the control signal is configured to cause the first switch and the second switch to connect to the one of the plurality of matching networks. 
     
     
       7. A method comprising:
 receiving a broadcast radio signal from an antenna into a radio receiver via one of a plurality of selectable matching networks, the antenna comprising a flexible conductor, an antenna network profile of the antenna varying when the flexible conductor is physically reconfigured; 
 decoding an analog audio signal and a digital signal from the radio broadcast signal using the radio receiver; 
 selecting the one of the plurality of selectable matching networks from among the plurality of selectable matching networks based at least in part on a quality of the digital signal using matching network control circuitry; 
 storing data relating to a context of use and the one of the plurality of selectable matching networks into volatile or nonvolatile memory, wherein the data comprises data relating to a frequency of the broadcast radio signal; a location determined by location-sensing circuitry; an orientation determined by one or more accelerometers; or a global unique identifier associated with the antenna; or any combination thereof; and 
 initializing the radio receiver after the data relating to the context of use the one of the plurality of selectable matching networks has been stored, evaluating a new context of use, and selecting the one of the plurality of selectable matching networks or another of the plurality of selectable matching networks using the matching network control circuitry based at least in part on a comparison between the new context of use and the stored context of use. 
 
     
     
       8. The method of  claim 7 , comprising storing data relating to the quality of the digital signal when data relating to the context of use and the one of the plurality of selectable matching networks are stored.

Description:
BACKGROUND 
     The present disclosure relates generally to impedance matching for an antenna and, more particularly, to selecting a matching network for an antenna based on certain signal characteristics. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     To efficiently transfer a received radio frequency (RF) signal from an antenna to a radio receiver, a matching network may be employed. Electrically coupled between the antenna and the receiver, the matching network may compensate for impedance differences between the antenna and the receiver. When the impedances of the antenna and the radio receiver are known, a single matching network may be configured for efficient RF signal transfer over a range of RF frequencies. Generally, the impedances of the antenna and the radio receiver may be known when the antenna is fixed in place and/or is located at a known physical location relative to an RF signal source. 
     Certain electronic devices, however, may employ antennas having variable impedances, or antenna network profiles. For example, many handheld electronic devices may use headsets or other flexible external wiring as antennas. In general, different varieties of headsets may have different antenna network profiles. Moreover, the antenna network profiles of such headsets may vary during normal use, as the headsets may move. When headset wiring changes shape by flexing, wrapping, twisting, and so forth, the antenna network profile of the headset may accordingly change, potentially causing the impedance of the headset to become unmatched to the radio receiver, which may cause a degradation of signal quality. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     Present embodiments relate generally to dynamically selecting a matching network for an antenna. In one example, an electronic device capable of selecting such a matching network may include an antenna, several selectable matching networks, a radio receiver, and matching network control circuitry. The radio receiver may couple to the antenna via one of the selectable matching networks to receive a radio signal with both an analog and digital component. The matching network control circuitry may select the matching network from among the several selectable matching networks based at least in part on a characteristic of the digital component of the radio signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a block diagram illustrating an embodiment of an electronic device capable of performing the techniques disclosed herein; 
         FIG. 2  is a schematic illustration of a handheld embodiment of the electronic device of  FIG. 1 ; 
         FIG. 3  is a schematic diagram of broadcast data that may be sent to the system of  FIG. 2 , in accordance with an embodiment; 
         FIG. 4  is a flow diagram representing the reception of radio broadcast information, in accordance with an embodiment; 
         FIG. 5  is a schematic block diagram illustrating a radio receiver having multiple selectable matching networks, in accordance with an embodiment; 
         FIG. 6  is a schematic block diagram illustrating an alternative embodiment of the radio receiver having multiple selectable matching networks of  FIG. 5 ; 
         FIG. 7  is a schematic diagram representing various signal characteristics that may serve as a basis for selecting one of the matching networks of  FIG. 5 , in accordance with an embodiment; 
         FIG. 8  is a flowchart describing an embodiment of a method for selecting one of the matching networks of  FIG. 5 ; 
         FIG. 9  is a flowchart describing an embodiment of another method for selecting the one of the matching networks of  FIG. 5 ; 
         FIG. 10  is a flowchart describing an embodiment of a method for selecting an initial matching network from among the matching networks of  FIG. 5 ; 
         FIG. 11  is a flowchart describing an embodiment of another method for selecting the initial matching network from among the matching networks of  FIG. 5 ; 
         FIG. 12-14  are flowcharts describing embodiments of methods for evaluating the proper matching network after a radio signal is being received; 
         FIG. 15  is a flowchart describing an embodiment of a method for selecting a matching network when a user selects a new frequency; 
         FIG. 16  is a flowchart describing an embodiment of a method for maintaining a historical record of device characteristics; and 
         FIG. 17  is a flowchart describing an embodiment of a method for selecting one of the matching networks of  FIG. 5  based on a historical record of device characteristics. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     Embodiments of the presently disclosed subject matter relate generally to systems, methods, and devices for selecting a matching network for an antenna. In particular, certain flexible antennas of conductive wiring, such as headsets for use with handheld electronic devices, may have antenna network profiles that vary as the antennas flex, wrap, twist, and so forth. Rather than employ a single matching network for such an antenna, presently disclosed embodiments of electronic devices employing such flexible antennas may select a suitable matching network from among several selectable matching networks. 
     Presently disclosed embodiments of electronic devices may receive radio signals that include a digital component over flexible antennas. For example, certain broadcast FM radio signals may include both an analog audio component and a supplementary digital signal in the Radio Data System or Radio Broadcast Data System (both of which are referred to herein as “RDS”) format. Rather than select the matching network based solely on certain signal characteristics of the received raw radio signal or only the analog component of the received raw radio signal, presently disclosed embodiments of electronic devices may select the matching network based at least in part on signal characteristics of the digital component of the radio signal. As described below, such digital component signal characteristics may include, for example, a locking speed of the digital component, the completeness of the digital component, a block error rate (BER) of the digital component, and/or a confidence of the digital component, among other things. 
     With the foregoing in mind, a general description of suitable electronic devices for performing the presently disclosed techniques is provided below with reference to  FIGS. 1 and 2 . In particular,  FIG. 1  is a block diagram depicting various components that may be present in an electronic device suitable for use with the present techniques, and  FIG. 2  represents one example of a suitable electronic device, which may be, as illustrated, a handheld electronic device having an antenna, a radio receiver, and two or more selectable matching networks. 
     Turning first to  FIG. 1 , electronic device  10  for performing the presently disclosed techniques may include, among other things, central processing unit (CPU)  12 , main memory  14 , nonvolatile storage  16 , display  18 , user interface  20 , location-sensing circuitry  22 , input/output (I/O) interface  24 , network interfaces  26 , radio receiver  28 , and accelerometers  30 . By way of example, electronic device  10  may represent a block diagram of the handheld device depicted in  FIG. 2  or a similar device. 
     In electronic device  10  of  FIG. 1 , CPU  12  may be operably coupled to main memory  14  and nonvolatile memory  16  to perform various algorithms for carrying out the presently disclosed techniques. Display  18  may be a touch-screen display, which may enable users to interact with user interface  20  of electronic device  10 . Location-sensing circuitry  22  may represent device capabilities for determining the relative or absolute location of electronic device  10 . By way of example, location-sensing circuitry  22  may represent Global Positioning System (GPS) circuitry, algorithms for estimating location based on proximate wireless networks, such as local Wi-Fi networks, and/or magnetometer circuitry for estimating a current facial direction of electronic device  10 . I/O interface  24  may enable electronic device  10  to interface with various other electronic devices, as may network interfaces  26 . Network interfaces  26  may include, for example, interfaces for a personal area network (PAN), such as a Bluetooth network, for a local area network (LAN), such as an 802.11x Wi-Fi network, and/or for a wide area network (WAN), such as a 3G cellular network. Accelerometers  30  may indicate a current movement or orientation of electronic device  10 . 
     Electronic device  10  may receive radio broadcasts using radio receiver  28 . Radio receiver  28  may receive broadcasts in one or more specific bands of spectrum, such as the FM radio band, and may detect both an audio signal and a concurrently-encoded digital signal when tuned to a desired frequency. By way of example, the audio signal may be an analog or digital FM radio signal and the concurrently-encoded digital signal may be a digital signal in the Radio Data System (RDS) or Radio Broadcast Data System (RBDS) (collectively referred to herein as “RDS”) format. Radio receiver  28  may receive the radio signal from an antenna, which may include the conductive wiring of a headset attached to electronic device  10 . The antenna may join to radio receiver  28  via one of a number of selectable matching networks, as described in greater detail below. 
       FIG. 2  depicts handheld device  32 , which may represent one embodiment of electronic device  10 . Handheld device  32  may be, for example, a portable phone, a media player, a personal data organizer, a handheld game platform, or any combination of such devices. By way of example, handheld device  32  may be a model of an iPod® or iPhone® available from Apple Inc. of Cupertino, Calif. 
     Handheld device  32  may couple to antenna  34 , illustrated as a headset connected to handheld device  32  via flexible conductive wiring. Enclosure  36  may protect interior components from physical damage and to shield them from electromagnetic interference. Enclosure  36  may surround display  18 , which may display interface  20 . I/O interfaces  24  may open through enclosure  36  and may include, for example, a proprietary I/O port from Apple Inc. to connect to external devices. 
     User input structures  38 ,  40 ,  42 , and  44  may, in combination with display  18 , allow a user to control handheld device  32 . For example, input structure  38  may activate or deactivate handheld device  32 , input structure  40  may navigate user interface  20  to a home screen or a user-configurable application screen, input structures  42  may provide volume control, and input structure  44  may toggle between vibrate and ring modes. Microphones  46  and speaker  48  may enable playback of audio and/or may enable certain phone capabilities. Headset input  50  may provide a connection to antenna  34  when antenna  34  is a headset. Headset input  50  may provide an electrical connection to radio receiver  28  via one of a number of selectable matching networks, as described in greater detail below. 
       FIG. 3  is a schematic diagram illustrating a radio broadcast signal that may be received by electronic device  10 . As shown in  FIG. 3 , radio broadcaster  52  may broadcast a radio signal at a specific frequency that includes both audio data  54  and non-audio data, such as digital RDS data  56 . By way of example, radio broadcaster  52  may be an FM radio broadcaster, audio data  54  may be an analog or digital FM radio signal, and digital RDS data  56  may include digital text data or other digital data relating to currently-playing audio in audio data  54 . Such digital RDS data  56  may identify currently-playing audio in audio data  54  by listing an artist, a title, and/or a global unique identifier (GUID) for the currently-playing audio, among other things. The broadcast audio data  54  and RDS data  56  may be received by handheld device  32 , or a similar electronic device  10 , via antenna  34 . As described below, the quality of audio data  54  and digital RDS data  56  may vary as a network profile of antenna  34  varies. Thus, from time to time, handheld device  32  may select from a number of selectable matching networks to improve reception. 
     Flow diagram  58  of  FIG. 4  schematically represents a manner of receiving such a broadcast radio signal having both audio data  54  and non-audio data, such as digital RDS data  56 . Raw radio broadcast signal  60 , which may include both audio data  54  and digital RDS data  56 , may enter radio receiver  28  of handheld device  32  through antenna  34 . Matching network  62  may be selected such that, when coupled to antenna  34 , raw radio broadcast signal  60  is efficiently transferred to FM receiver  64  with sufficient signal quality. FM receiver  64  may process raw radio broadcast signal  60  to obtain digital RDS data  66  and audio stream  68 . As such, FM receiver  64  may include analog-to-digital (A/D) circuitry for digitizing and/or compressing audio data  54  to obtain audio stream  68 . 
     Digital RDS data  66  may include various textual information relevant to audio currently playing in audio stream  68 . Specifically, digital RDS data  66  may supply blocks of digital data that identify, for example, radio broadcaster  52  call letters, an artist name, a song title, and/or a global unique identifier (GUID) associated with currently-playing audio, among other things. Certain signal characteristics of the received blocks of digital RDS data  66  may enable handheld device  32  to select matching network  62 . Many such techniques are described below with reference to  FIGS. 5-17 . 
       FIG. 5  schematically illustrates certain blocks of the flow diagram of  FIG. 4 . In particular, antenna  34  may couple to radio receiver  28 , which may include matching network  62  coupled to FM receiver  64 . Since antenna  34  may include flexible conductive wiring for a headset, as illustrated above with reference to  FIG. 2 , the impedance, or antenna network profile, of antenna  34  may vary as antenna  34  is shifted, bent, coiled, turned, and so forth. As the antenna network profile of antenna  34  changes, a signal quality of raw broadcast signal  60  may degrade if not properly matched to FM receiver  64 . To effectively transfer raw broadcast signal  60  on antenna  34  through to FM receiver  64 , matching network  62  may include two or more selectable matching networks, illustrated in  FIG. 5  as matching network A and matching network B, that may best match the current profile of antenna  34 . Although  FIG. 5  illustrates two selectable matching networks employed by matching network  62 , matching network  62  may employ any suitable number of matching networks. 
     To efficiently transfer raw broadcast signal  60  from antenna  34  to FM receiver  64 , matching network  62  may include switch  70 , which may selectively join antenna  34  to either matching networks  72  or  74 , which are also labeled matching network A and matching network B. Similarly, FM receiver  64  may include switch  76 , which may selectively join matching network A or matching network B to FM receiver input path  78 . Alternatively, switch  76  may be a component independent of FM receiver  64 . Matching network control circuitry  80  may control switches  70  and  76 , causing the signal path to flow through matching network A or matching network B. Matching network control circuitry  80  may include logic for selecting either matching network A or matching network B based on various received radio signal characteristics. Additionally or alternatively, CPU  12  may control matching network control circuitry  80  to cause the selection of the matching network based on such signal characteristics. 
     The selectable matching networks of matching network  62 , such as matching network A and matching network B, may be designed to accommodate various antenna network profiles of antenna  34  and/or various frequencies of radio signals. For example, matching network A may be designed for lower FM-band frequencies and matching network B may be designed for higher FM-band frequencies. Additionally or alternatively, matching network A and matching network B may be designed respectively for certain types of headsets generally sharing similar antenna network profiles, and/or matching network A and matching network B may be designed to match certain physical configurations of antenna  34 , such as bending, wrapping, twisting, and so forth. 
     Matching network control circuitry  80  may select a suitable matching network from among those provided in matching network  62  based on the quality of a received radio signal. For example, matching network control circuitry  80  may select, or may be controlled by CPU  12  to select, either matching network A or matching network B based on certain signal characteristics of the received raw broadcast signal  60  or its components, audio signal  54  or digital RDS signal  56 . Many such signal characteristics are described below with reference to  FIG. 7 . 
       FIG. 6  represents another embodiment of the matching network circuitry illustrated in  FIG. 5 . It should be appreciated that all techniques disclosed herein for selecting one of the matching networks A or B using the circuitry of  FIG. 5  may similarly apply to the circuitry of  FIG. 6 . As illustrated in  FIG. 6 , antenna  34  may couple to matching network  62 , which may couple to FM receiver input path  78 . Matching network circuitry  62  may include common matching network  82 , which may represent circuitry common to all selectable matching networks of matching network  62 . 
     Matching network  62  may selectably function as one of several matching networks depending on which elements are switched into common matching network  82 . In the embodiment illustrated in  FIG. 6 , matching network  62  may selectably function as either matching network A or matching network B, but may be adapted to selectably function as any suitable number of matching networks. To function as matching network A, switches  70  and  76  of matching network  62  may respectively couple to matching element A circuitry. Similarly, to function as matching network B, switches  70  and  76  of matching network  62  may respectively couple to matching element B circuitry. In this way, matching network A may be defined as the combination of common matching network  82  and matching element A circuitry, while matching network A may be defined as the combination of common matching network  82  and matching element A circuitry. By controlling switches  70  and  76  to select between matching elements A or B, matching network control circuitry  80  may respectively cause matching network  62  to function as matching network A or B. 
       FIG. 7  provides a diagram describing various signal characteristics  84  of the received raw broadcast signal  60  or its components. Based on such signal characteristics  84 , electronic device  10  may determine which of the selectable matching networks in matching network  62  most efficiently transfers raw broadcast signal  60  from antenna  34  to FM receiver  64 . Specifically, as noted above, the antenna network profile of antenna  34  may vary with movement and/or location, and improper impedance matching between antenna  34  and FM receiver  64  may cause raw broadcast signal  60  to degrade. As such, when the quality of raw broadcast signal  60  or its components falls beneath a threshold level, a currently-selected matching network of matching network  62  may not properly match the impedances of the antenna  34  and FM receiver  64 . Thus, when the quality of raw broadcast signal  60  or its components falls beneath such a threshold level, matching network control circuitry  80  may select another selectable matching network of matching network  62 . 
     CPU  12  or logic circuitry employed by matching network control circuitry  80  may determine the quality of raw broadcast signal  60  or its components by observing certain signal characteristics  84  associated with raw broadcast signal  60 , such as received signal strength indicator (RSSI)  86 , signal-to-noise ratio (SNR)  88 , and/or a level of multipath distortion  90 . Additionally or alternatively, signal characteristics  84  associated with digital RDS data  66  may be observed, which may include a locking speed  92 , a completeness  94 , a block error rate (BER)  96 , and/or a signal confidence  98  of digital RDS data  66 . Signal characteristics  84  may be assessed by radio receiver  28  when the raw broadcast signal  60  is processed to produce digital RDS data  66  and digital analog stream  68 . Additionally or alternatively, CPU  12  or other specialized hardware may evaluate the produced digital RDS data  66  and digital analog stream  68  to estimate certain signal characteristics  84 . It should be understood that the listed signal characteristics  84  described herein are intended to be exemplary and not exhaustive. 
     Received signal strength indicator (RSSI)  86  may provide an indication of how efficiently raw broadcast signal  60  has been transferred from antenna  34  to FM receiver  64  via matching network  62 . While RSSI  86  remains above a threshold value, the currently-selected matching network A or B of matching network  62  may be proper, and the currently-selected matching network A or B may remain selected. Similarly, when RSSI  86  drops below a threshold value, the currently-selected matching network A or B of matching network  62  may be improper, and a different matching network of matching network  62  may be selected. 
     Signal-to-noise ratio (SNR)  88  may similarly indicate how efficiently raw broadcast signal  60  has been transferred from antenna  34  to FM receiver  64  via matching network  62  and, accordingly, whether the currently-selected matching network A or B of matching network  62  is proper. SNR  88  may vary depending on a level noise present in raw broadcast signal  60  after passing through matching network  62 . Because FM receiver  64  may generally employ techniques for noise suppression, such as preemphasis and/or deemphasis, signal noise from raw broadcast signal  60  may not readily appear in digital RDS data  66  or audio stream  68  output by FM receiver  64 . As such, FM receiver  64  may provide a determination of SNR  88  before noise suppression techniques have removed much of the noise originally present in raw broadcast signal  60 . In certain embodiments, FM receiver  64  may additionally or alternatively provide a determination of SNR  88  after noise suppression techniques have been applied. 
     Multipath interference  90  characteristics, which may be caused by reflections and echoes of the raw broadcast signal  60  prior to reception by antenna  34 , may also form a basis for selecting from among the selectable matching networks of matching network  62 . Generally, FM receiver  64  may detect and/or compensate for certain levels of multipath interference  90 . As such, FM receiver  64  may also provide such a detected level of multipath interference  90 . 
     As noted above with reference to  FIGS. 3 and 4 , raw broadcast signal  60  may include both audio data  54  and a supplementary digital component such as digital audio data  56 . FM receiver  64  may process raw broadcast signal  60  to obtain audio stream  68 , based on audio data  54 , and processed digital RDS data  66 , based on digital RDS data  56 . When processing digital RDS data  56  to obtain processed digital RDS data  66 , FM receiver  64  may observe certain characteristics specifically associated with this digital component of raw broadcast signal  60 . 
     In one example, when digital RDS data  56  is received and decoded by FM receiver  64 , the quality of the digital RDS data  56  component of raw broadcast signal  60  may be reflected by the amount of time required for FM receiver  64  to lock onto digital RDS data  56  within raw broadcast signal  60 . This digital RDS data  56  locking speed  92  may indicate signal quality because a higher-quality signal may result in a faster locking speed  92 , while a lower-quality signal may result in a slower locking speed  92 . Thus, if raw broadcast signal  60  has been efficiently transferred between antenna  34  and FM receiver  64  via the selected matching network A or B of matching network  62 , locking speed  92  may be relatively fast. If not, locking speed  92  may be relatively slow. 
     In another example, as FM receiver  64  receives and decodes blocks of digital RDS data  56 , various additional signal characteristics  84  may be determined. As described in the Radio Data System (RDS) specification, digital RDS data  56  from raw broadcast stream  60  may include defined blocks of data having predetermined lengths. Specifically, each block may include an information word of 16 bits and a checkword of 10 bits for a total of 26 bits. By applying error-checking techniques that compare the data received in the information word to the checkword, FM receiver  64  may determine a measure of the completeness  94  of the received digital RDS data  56 , a measure of the general block error rate (BER)  96  of the received digital RDS data  56 , and a measure of the signal confidence  98  of the received digital RDS data  56 . 
     A relatively higher measure of completeness  94  or signal confidence  98 , or a relatively lower measure of BER  96 , may indicate a higher signal quality of raw broadcast signal  60 . Similarly, a relatively lower measure of completeness  94  or signal confidence  98 , or a relatively higher measure of BER  96 , may indicate a lower signal quality of raw broadcast signal  60 . Since the signal quality of raw broadcast signal  60  may vary depending on which of the selectable matching networks of matching network  62  is currently selected, selection of the proper selectable matching network may involve the consideration of completeness  94 , BER  96 , and/or signal confidence  98  of digital RDS data  56 . 
     Any one or a combination of signal characteristics  84  representing the quality of raw broadcast signal  60 , such as those described above, may be employed to select the proper selectable matching network of matching network  62  using a variety of techniques, many of which are described below. Matching network control circuitry  80  may select the proper matching network after CPU  12  or logic within matching network control circuitry  80  has evaluated one or more of the signal characteristics  84 , which may be assigned digital values. These digital values, as well as various thresholds associated with the digital values for signal quality, may be used by CPU  12  or logic of matching network control circuitry  80  to select the appropriate selectable matching network from matching network  62 . 
     By way of example, signal characteristics  84  may be evaluated in the following manner. Certain signal characteristics  84 , such as RSSI  86 , locking speed  92 , and block error rate (BER)  96  may be individually evaluated and assigned a digital value (e.g., a number between 0 and 10). These digital values may be added together, or may be applied in a function weighting certain signal characteristics  84  differently according to how the certain signal characteristics  84  may relate to impedance matching. The resulting combination of digital values may be compared to a number representing a threshold level of signal quality. For example, if three signal characteristics  84  are each assigned a value from 0 to 10, and the values are simply summed for a maximum level of quality of 30, a threshold level of quality may be, for example, a digital value of 20. Any or all of signal characteristics  84  described above may be evaluated in such a manner when, as described below, the signal quality of raw broadcast signal  60  is tested to determine whether the proper selectable matching network of matching network  62  is selected. Alternatively, threshold values associated with certain signal characteristics  84  may relate to raw values, such as, for example, a specific maximum acceptable block error rate (BER)  96 . 
     One embodiment of a method for selecting between several selectable matching networks of matching network  62 , such as selecting between matching network A and matching network B, is represented by flowchart  100  of  FIG. 8 . Generally, flowchart  100  may describe an embodiment of a method for selecting between matching network A and matching network B when radio receiver  28  is first initialized. In step  102 , radio receiver  28  may be initialized, as may occur when electronic device  10  is powered on or when headset antenna  34  is inserted into electronic device  10 . 
     In step  104 , matching network control circuitry  80  may control switches  70  and  76  such that one of the two matching networks A or B is selected. Which of the matching networks A or B is selected as the first matching network to test in step  104  may be preset (e.g., always start with matching network A) or may be determined based on other factors (e.g., last requested radio frequency, headset global unique identifier (GUID), etc.), as described below with reference to  FIGS. 10 ,  11 , and  17 . In step  106 , FM receiver  64  may tune to a particular test frequency. The test frequency may be, for example, the frequency last requested by a user, an approximately median frequency of the radio frequency (RF) band that radio receiver  28  is able to receive, or one or more saved favorite radio frequencies. 
     In step  108 , matching network control circuitry  80  may evaluate certain signal characteristics  84  of raw broadcast signal  60  at the test frequency. In the manner described above, CPU  12  or logic associated with matching network control circuitry  80  may assign discrete values to certain signal characteristics  84  associated with raw broadcast signal  60  received at the test frequency. For example, RSSI  86 , locking speed  92 , and block error rate (BER)  96  may be individually evaluated and assigned a digital value (e.g., a number between 0 and 10). The sum of the digital values may approximate a signal quality of raw broadcast signal  60 . 
     In decision block  110 , if the values associated with signal characteristics  84  of raw broadcast signal  60  exceed a threshold value (e.g., a value of 20 when three signal characteristics  84  are evaluated), the process may flow to step  112 , and the connection to the currently-selected matching network A or B may be maintained. Alternatively, decision block  110  may involve determining whether a particular one or more signal characteristics  84  of interest remains above a threshold value. The threshold value compared in decision block  110  may be predetermined, or may vary depending on other factors, such as the current type of programming as indicated by digital RDS data  66 . For example, the threshold associated with spoken word programming may be lower than the threshold associated with music programming. Additionally or alternatively, the threshold value may be relatively high when first tested in decision block  110 , and may gradually drop as decision block  110  may repeat, as noted below, until an optimal matching network is selected from among the selectable matching networks of matching network  62 . 
     If the signal characteristics  84  evaluated in step  108  fall below the threshold, as tested in decision block  110 , the raw broadcast signal  60  may not be efficiently transferred between antenna  34  and FM receiver  64  because the impedance may not be properly matched. Thus, in step  114 , matching network control circuitry  80  may switch to the next matching network. For example, if matching network control circuitry  80  had selected matching network A in step  104 , matching network control circuitry  80  may select matching network B in step  114 . Subsequently, steps  106 ,  108 ,  110 , and  114  may continue indefinitely until the signal characteristics  84  improve and rise above the required threshold of decision block  110 . 
       FIG. 9  depicts flowchart  116 , providing another embodiment of a method for selecting the proper matching network upon initialization of radio receiver  28 . In step  118 , radio receiver  28  may be initialized, as may occur when electronic device  10  is powered on or when headset antenna  34  is inserted into electronic device  10 . In step  120 , matching network control circuitry  80  may select matching network A. In step  122 , FM receiver  64  may tune to a test frequency. As noted above, the test frequency may be, for example, the frequency last requested by a user, an approximately median frequency of the radio frequency (RF) band that radio receiver  28  is able to receive, or one or more saved favorite radio frequencies. 
     In step  124 , CPU  12  or logic associated with matching network control circuitry  80  may evaluate one or more signal characteristics  84  in the manner described above with reference to step  108  of flowchart  100 . Subsequently, in step  126 , the results of the evaluation of the one or more signal characteristics  84  of step  124  may be stored in memory  14 . In step  128 , matching network control circuitry  80  may select matching network B. In step  130 , FM receiver  64  may remain tuned to the same test frequency as in step  122 , and in step  132 , the same signal characteristics  84  may be evaluated. The results of the evaluation of the signal characteristics  84  of step  132  also may be stored in memory  14  in step  134 . 
     In decision block  136 , the stored test results of steps  126  and  134  may be compared to determine which selectable matching network of matching network  62  should be selected. If the evaluation of step  126  is higher than the evaluation of step  134 , the received raw broadcast signal  60  may be of a higher quality when matching network A is selected, and the process may flow to step  138 . In step  138 , matching network control circuitry  80  may select matching network A. If the evaluation of step  126  is lower than the evaluation of step  134 , the received raw broadcast signal  60  may be of a higher quality when matching network B is selected, and the process may flow to step  140 . In step  140 , matching network control circuitry  80  may continue to select matching network B. 
     As described above with reference to flowchart  100  of  FIG. 8 , when radio receiver  28  is initialized, matching network control circuitry  80  may initially connect to a first matching network to begin testing. Flowchart  142  of  FIG. 10  describes one embodiment of a method for selecting such a first matching network from among the selectable matching networks of matching network  62 . The use of the method of flowchart  142  to select the first matching network may increase the likelihood that the first selected matching network properly matches antenna  34  to FM receiver  64 . 
     Flowchart  142  of  FIG. 10  may begin when electronic device  10  is powered on or when headset antenna  34  is inserted into electronic device  10  in step  144 , which may cause radio receiver  28  to initialize. In step  146 , a radio frequency expected to be requested by a user of electronic device  10  may be recalled from memory  14  or nonvolatile storage  16 . Such an expected radio frequency may include, for example, the most recently requested radio frequency, most commonly requested radio frequency, or a radio frequency often used during current circumstances. For example, if a user last requested a particular radio frequency when the user was at a particular location (e.g., a local area FM broadcast at a fitness facility), and location-sensing circuitry  22  indicates that electronic device  10  is at that particular location, electronic device  10  may recall the particular recalled radio frequency from memory  14  or nonvolatile storage  16 . 
     As noted above, the selectable matching networks of matching network  62 , such as matching network A and matching network B, may be designed to best match antenna  34  and FM receiver  64  in different circumstances. In some embodiments, matching network A and matching network B may be designed for particular bands of frequency spectrum. If, in decision block  148 , matching network A is generally designed for a frequency band that includes the frequency recalled in step  146 , matching network control circuitry  80  may select matching network A as the first network to test, in step  150 . On the other hand, if matching network B is generally designed for a frequency band that includes the frequency recalled in step  146 , matching network control circuitry  80  may instead select matching network B as the first network to test, in step  152 . 
     Flowchart  154  of  FIG. 11  describes another embodiment of a method for selecting a first matching network to test from among the selectable matching networks of matching network  62 , as described above with reference to flowchart  100  of  FIG. 8 . After radio receiver  28  is initialized in step  156 , which may occur when electronic device  10  is powered on or when headset antenna  34  is inserted into electronic device  10 , CPU  12  or logic associated with matching network control circuitry  80  may obtain a global unique identifier (GUID) associated with headset antenna  34  from a signal provided by headset antenna  34  in step  158 . Because a user of electronic device  10  may frequently use a particular headset in the same context (e.g., at a fitness facility, walking through the city, while sitting at a desk, etc.), the antenna network profile of headset antenna  34  may be similar under such circumstances. 
     To properly match the antenna network profile of headset antenna  34  to FM receiver  64 , the proper selectable matching network of matching network  62  also may be similar. Thus, the GUID obtained in step  158  may be used to estimate a proper matching network when the user initializes electronic device  10  with the headset. In step  160 , based on the obtained GUID, CPU  12  or logic associated with matching network control circuitry  80  may recall which of the selectable matching networks of matching network  62  was last used with the current headset antenna  34 . Matching network control circuitry  80  may select this recalled matching network to be the first test matching network. 
       FIGS. 12-15  provide flowcharts describing embodiments of methods for reevaluating the proper selectable matching network after raw broadcast signal  60  is being received and/or played. Turning first to  FIG. 12 , flowchart  162  describes an embodiment of a method for continually evaluating signal characteristics  84  associated with the received raw broadcast signal  60 . In step  164 , electronic device  10  may receive and/or play raw broadcast signal  60  in the manner described above with reference to  FIG. 4 . In decision block  166 , electronic device  10  may evaluate and test certain signal characteristics  84  continually. If these certain signal characteristics  84  drop beneath a threshold, matching network control circuitry  80  may switch to a different matching network in an attempt to improve the signal characteristics  84 , in step  168 . The certain signal characteristics  84  that are continually tested in decision block  166  may relate to digital RDS data  56  received by FM receiver  64 . As digital RDS data  56  are received and processed by FM receiver  64 , FM receiver may continually provide signal characteristics  84  specifically associated with digital RDS data  56 . 
     Flowchart  170  of  FIG. 13  describes an embodiment of a method for periodically, rather than continually, evaluating signal characteristics  84  associated with the currently-selected matching network of matching network  62 . In step  172 , electronic device  10  may be receiving and/or playing raw broadcast signal  60 . In step  174 , matching network control circuitry  80  may periodically evaluate signal characteristics  84 . For example, matching network control circuitry  80  may test or may evaluate certain signal characteristics  84  every second, 5 seconds, 10 seconds, 30 seconds, minute, 2 minutes, 5 minutes, and so forth. If, in decision block  176 , signal characteristics  84  fall below a given threshold, in step  178 , matching network control circuitry  80  may switch to another matching network. The method of flowchart  170  may be particularly useful for evaluating analog signal characteristics  84  of raw broadcast signal  60 , such as received signal strength indicator (RSSI), signal-to-noise ratio (SNR)  88 , and/or multipath characteristics  90 . 
     Flowchart  180  of  FIG. 14  describes another embodiment of a method for evaluating the currently-selected matching network of matching network  62 . In step  182 , electronic device  10  may be receiving and/or playing the raw broadcast signal  60 , and in step  184 , FM receiver  64  may decode a series of blocks of digital RDS data  56 . As each block of digital RDS data  56  is processed, completeness  94 , block error rate (BER)  96 , or signal confidence  98  may be determined and provided. In decision block  186 , after each RDS block is decoded, signal characteristics associated with the recently-decoded block may be evaluated. If these signal characteristics  84  fall beneath a threshold, matching network control circuitry  80  may select another matching network in step  188 . 
     Flowchart  190  of  FIG. 15  describes an embodiment of a method for selecting a matching network when a user selects a new frequency. In step  192 , electronic device  10  may receive and/or play information from raw broadcast signal  60 , and in step  194 , a user may tune to a new radio frequency. In doing so, the currently-selected matching network of matching network  62  may not be optimal for the new frequency. 
     Because the selectable matching networks of matching network  62 , such as matching network A and matching network B, may be designed to best match antenna  34  and FM receiver  64  for particular bands of frequency spectrum, decision block  195  may test whether one of the selectable matching networks of matching network  62  is best suited for the requested frequency. If, in decision block  195 , matching network A is generally designed for a frequency band that includes the frequency requested in step  194 , matching network control circuitry  80  may select matching network A in step  150 . On the other hand, if matching network B is generally designed for a frequency band that includes the frequency requested in step  194 , matching network control circuitry  80  may instead select matching network B in step  197 . 
       FIGS. 16-17  represent manners of employing historical signal characteristics  84  and various other data to determine the proper selectable matching network of matching network  62 . Turning first to  FIG. 16 , flowchart  198  describes an embodiment of a method for maintaining historical signal characteristic  84  data and historical matching network data. In first step  200 , electronic device  10  may be receiving and/or playing information received from raw radio broadcast  60 . In step  202 , various signal characteristics  84  may be evaluated periodically, in the manner described above with reference to  FIG. 7 . In step  204 , the current evaluations of signal characteristics  84  may be recorded and stored in non-violate storage  16 . In addition to those signal characteristics  84  evaluated in step  202 , other information, such as the currently applied matching network A or B, a GUID associated with the current headset antenna  34 , an orientation or location of electronic device  10  as determined from location-sensing circuitry  22  or accelerometers  30 , and/or a current radio frequency of raw broadcast signal  60 . 
     Storing the periodically-tested signal characteristics  84 , currently-selected matching network of matching network  62 , and various other data relating to the context in which electronic device  10  is being used may enable the later determination of meaningful associations between raw broadcast signal  60  quality and the proper matching network. For example, electronic device  10  may be used in a particular location and orientation (e.g., on a user&#39;s arm at a fitness facility), which may affect how raw broadcast signal  60  is received (e.g., through building walls and at a particular distance from broadcast station  52 ) and which may also affect the antenna network profile of headset antenna  34  (e.g., as the flexible wiring of antenna  34  is wrapped, bent, twisted, etc.). A particular matching network A or B of matching network  62  may be employed to match antenna  34  to FM receiver  64  under such conditions. Thereafter, signal characteristics  84 , contextual data, and the selected matching network may be stored in memory  14  or nonvolatile storage  16 . 
     Flowchart  206  of  FIG. 17  describes an embodiment of a method for selecting a first test matching network based on such stored historical signal characteristics  84  and other contextual data. In step  208 , radio receiver  28  may be initialized, which may occur when electronic device  10  is powered on or antenna  34  is inserted into electronic device  10 . In step  210 , the current electronic device  10  context of use may be compared to the historical signal characteristics  84  and other contextual data stored in step  204 . In step  212 , the first matching network to be tested may be selected based on the comparison of step  210 . 
     The embodiment of the method of flowchart  206  may be exemplified using the example introduced above. When a user begins to use electronic device  10 , the current context of use may be considered. If the current context of use resembles a prior context of use (e.g., on the user&#39;s arm at a fitness facility), and the signal characteristics  84  of that prior context of use were acceptable, the selectable matching network of matching network  62  that was employed in the prior context may be selected for the current context. 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

Metadata:
Filing Date: 20090904
Publication Date: 20150203
Grant Date: 20150203
Priority Date: 20090904
Inventors: WARREN DANIEL ADAM
FISHER, JR. JOSEPH ROI
YANG JAMES TSUNG-TAI
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H7/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H7/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/18", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 43647761