PATENT DOCUMENT

Publication Number: US-10944156-B2
Application Number: US-201715721532-A
Country: US
Kind Code: B2

Title: Wireless earphone antennas

Abstract:
An electronic device such as a wireless earbud may have antenna structures that are configured to form one or more antenna portions or antennas for transmitting and receiving wireless signals. The device may include control circuitry that is configured to selectively activate one or more antennas or antenna portions to transmit and receive wireless signals for the device. The device may include sensor circuitry that provide sensor data to the control circuitry. The control circuitry may use the sensor data to select and activate an optimal antenna based on the orientation of the earbud or the environment of the device. The antennas may be formed on opposing sides of a housing for the device. By providing configurable antenna structures, the device may be configured to adapt to the current environment and efficiently perform communications operations.

Claims:
What is claimed is: 
     
       1. A wireless earbud, comprising:
 a housing having a speaker port; 
 a speaker in the housing and aligned with the speaker port; 
 control circuitry in the housing and configured to identify sensor data; and 
 first and second antennas in the housing and coupled to the control circuitry, wherein the control circuitry is configured to selectively activate a given one of the first and second antennas based on the identified sensor data. 
 
     
     
       2. The wireless earbud defined in  claim 1 , wherein the first antenna comprises a first antenna feed, and the second antenna comprises a second antenna feed, the wireless earbud further comprising:
 transceiver circuitry in the housing; 
 a first radio-frequency transmission line coupled between the first antenna feed and the transceiver circuitry; and 
 a second radio-frequency transmission line coupled between the second antenna feed and the transceiver circuitry. 
 
     
     
       3. The wireless earbud defined in  claim 2 , further comprising:
 switching circuitry interposed between the transceiver circuitry and the first antenna feed, and interposed between the transceiver circuitry and the second antenna feed, wherein the control circuitry is configured to selectively activate the given one of the first and second antennas by adjusting the switching circuitry. 
 
     
     
       4. The wireless earbud defined in  claim 1 , further comprising:
 sensor circuitry configured to generate the sensor data and to provide the generated sensor data to the control circuitry. 
 
     
     
       5. The wireless earbud defined in  claim 4 , wherein the sensor circuitry comprises an accelerometer, and the sensor data comprises orientation data indicative of an orientation of the wireless earbud. 
     
     
       6. The wireless earbud defined in  claim 4 , wherein the sensor circuitry comprises a proximity sensor, and the sensor data comprises proximity sensor data. 
     
     
       7. The wireless earbud defined in  claim 1 , wherein the control circuitry is configured to receive the sensor data from an external device via the first antenna. 
     
     
       8. The wireless earbud defined in  claim 1 , wherein the first antenna comprises a first inverted-F antenna having a first antenna resonating element arm coupled to an antenna ground via a first return path and the second antenna comprises a second inverted-F antenna having a second antenna resonating element arm coupled to the antenna ground via a second return path. 
     
     
       9. The wireless earbud defined in  claim 8 , wherein the first antenna resonating element arm has first and second opposing ends, the second antenna resonating element arm has third and fourth opposing ends, the second end of the first antenna resonating element faces the third end of the second antenna resonating element, the first return path is coupled to the first end of the first antenna resonating element, and the second return path is coupled to the fourth end of the second antenna resonating element. 
     
     
       10. The wireless earbud defined in  claim 8 , further comprising:
 a battery, wherein a portion of the battery forms a portion of the antenna ground, the first return path is coupled to the antenna ground at a first side of the battery, and the second return path is coupled to the antenna ground at a second side of the battery that opposes the first side. 
 
     
     
       11. The wireless earbud defined in  claim 10 , wherein the first side of the battery comprises a first curved surface and the first antenna resonating element arm extends parallel to the first curved surface, and the second side of the battery comprises a second curved surface and the second antenna resonating element arm extends parallel to the second curved surface. 
     
     
       12. A wireless earbud, comprising:
 a housing having an opening; 
 a speaker in the housing and aligned with the opening; 
 antenna structures in the housing; 
 an antenna ground; 
 first and second antenna feeds coupled between the antenna structures and the antenna ground; 
 transceiver circuitry in the housing; 
 switching circuitry coupled between the first antenna feed and the transceiver circuitry, and between the second antenna feed and the transceiver circuitry; and 
 control circuitry configured to identify sensor data and to control the switching circuitry to selectively couple a given one of the first and second antenna feeds to the transceiver circuitry based on the identified sensor data. 
 
     
     
       13. The wireless earbud defined in  claim 12 , wherein the antenna structures comprise a resonating element arm and a first return path coupled between a first end of the resonating element arm and the antenna ground. 
     
     
       14. The wireless earbud defined in  claim 13 , wherein the antenna structures comprise an additional resonating element arm and a second return path coupled between a second end of the additional resonating element arm and the antenna ground. 
     
     
       15. The wireless earbud defined in  claim 14 , wherein the control circuitry is configured to control the switching circuitry to couple the first antenna feed to the transceiver circuitry and decouple the second antenna feed from the transceiver circuitry in a first configuration for the antenna structures and to couple the second antenna feed to the transceiver circuitry and decouple the first antenna feed from the transceiver circuitry in a second configuration for the antenna structures. 
     
     
       16. A system, comprising:
 a first earbud that comprises a first housing, a first speaker port in the first housing, a first speaker in the first housing that is aligned with the first speaker port, and first control circuitry in the first housing that is configured to identify sensor data; and 
 a second earbud that is configured to wirelessly communicate with the first earbud and that comprises a second housing, a second speaker port in the second housing, a second speaker in the second housing that is aligned with the second speaker port, antenna structures in the second housing that include first and second antenna feeds, and second control circuitry in the second housing that is configured to control the antenna structures to convey radio-frequency signals over a selected one of the first and second antenna feeds based on the identified sensor data. 
 
     
     
       17. The system defined in  claim 16 , wherein the first earbud further comprises additional antenna structures in the first housing that include third and fourth antenna feeds, wherein the first control circuitry is configured to control the additional antenna structures to convey additional radio-frequency signals over a selected one of the third and fourth antenna feeds. 
     
     
       18. The system defined in  claim 17 , wherein the first earbud further comprises sensor circuitry in the first housing that is configured to generate the sensor data and the first earbud is configured to wirelessly transmit the sensor data to the second earbud. 
     
     
       19. The system defined in  claim 17 , wherein the second earbud further comprises sensor circuitry in the second housing that is configured to generate the sensor data and the second earbud is configured to wirelessly transmit the sensor data to the first earbud. 
     
     
       20. The system defined in  claim 19 , wherein the first control circuitry is configured to control the additional antenna structures to convey the additional radio-frequency signals over the selected one of the third and fourth antenna feeds based on the sensor data.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless circuitry. 
     Electronic devices such as electronic accessories for cellular telephones, computers, and other electronic equipment often include wireless circuitry. For example, headsets or earbuds are available that communicate wirelessly with cellular telephones and other equipment. 
     Challenges can arise in implementing wireless communications circuitry in a compact device such as an earbud. If care is not taken, antennas will not perform effectively. This can make it difficult or impossible to achieve desired levels of wireless communications performance. 
     It would therefore be desirable to be able to provide devices such as headsets or earbuds with improved wireless circuitry. 
     SUMMARY 
     An electronic device such as a wireless earbud may have antenna structures that are configured to form a plurality of antennas or antenna portions for transmitting and receiving wireless signals. In particular, the antenna structures may be configured to form a first antenna in a first mode of operation and a second antenna in a second mode of operation. 
     The antenna structures may be coupled to transceiver circuitry. Switching circuitry may be interposed between the transceiver circuitry and antenna feeds of respective antennas or antenna portions formed from the antenna structure. The device may include control circuitry that is configured to selectively activate one or more antennas of the plurality of antennas (or one or more antenna portions of the antenna structures) to transmit and receive wireless signals for the device by selecting a state of the switching circuitry. For example, a first state of the switching circuitry may couple the transceiver circuitry to an antenna feed of the first antenna or antenna region, and a second state of the switching circuitry may couple the transceiver circuitry an antenna feed of the second antenna or antenna region. 
     The device may include additional components, on which the antenna structures or portions of the antenna structures are formed. The additional components may include a battery or grounding structure. 
     The device may include sensor circuitry that provide sensor data to the control circuitry. The control circuitry may use the sensor data to select one or more optimal antennas based on the orientation of the device or the environment in which the device lies. By providing configurable antenna structures, the device may be configured to adapt to any environment and efficiently perform communications operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device with wireless circuitry in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of an illustrative antenna of the type that may be used in an electronic device in accordance with an embodiment. 
         FIG. 3  is a schematic diagram of an illustrative electronic device having antenna structures with switchable antenna configurations in accordance with an embodiment. 
         FIG. 4  is a schematic diagram of an illustrative electronic device having multiple switchable antennas in accordance with an embodiment. 
         FIG. 5  is a diagram showing how an illustrative electronic device having an antenna of the type shown in  FIG. 4  may be oriented with respect to the ear of a user during operation of the electronic device in accordance with an embodiment. 
         FIG. 6  is a perspective view of an illustrative electronic device such as a rotationally symmetric wireless earbud in accordance with an embodiment. 
         FIG. 7  is a flowchart of illustrative steps that may be performed by an electronic device to wirelessly communicate using antennas of the types shown in  FIGS. 3-6  in accordance with an embodiment. 
         FIG. 8  is a graph of illustrative antenna efficiency curves for antenna structures operating in multiple antenna configurations in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device of the type that may be provided with wireless circuitry is shown in  FIG. 1 . Device  10  of  FIG. 1  may be a wireless accessory such as a wireless headset, wireless headphones, a wireless earbud or earphone, or other small portable accessory. Device  10  may be used in conjunction with another electronic device such as electronic device  8  if desired. 
     Electronic device  8  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device, a pendant device, a headphone or earpiece device, a virtual or augmented reality headset device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, a wireless access point or base station (e.g., a wireless router or other equipment for routing communications between other wireless devices and a larger network such as the internet or a cellular telephone network), a desktop computer, a keyboard, a gaming controller, a computer mouse, a mousepad, a trackpad or touchpad, equipment that implements the functionality of two or more of these devices, or other electronic equipment. The above-mentioned examples are merely illustrative. Other configurations may be used for electronic devices if desired. If desired, electronic device  8  may also be referred to herein as an audio source, an audio device, or a wireless audio source (e.g., because device  8  may provide audio data to device  10  for performing playback operations on the audio data). If desired, device  10  may be a different type of electronic equipment than device  8 . Configurations in which device  10  is a wireless accessory may sometimes be described herein as an example. 
     If desired, device  10  may also communicate with another accessory electronic device such as electronic device  10 ′. In particular, device  10 ′ may also be a wireless accessory such as a wireless headset, a wireless earbud or earphone, or other smaller portable accessory (e.g., device  10 ′ and device  10  may both be the same type of device). Device  10  and  10 ′ may form a device pair that operate together, such as to play back audio data. For example, device  10  and  10 ′ may both be earbuds or earphones in a pair of earbuds or earphones. This is merely illustrative. If desired, device  10  and  10 ′ may operate in combination under any other suitable configurations. 
     Devices such as device  10  may communicate wirelessly with external electronic equipment such as device  8  over wireless communications link  36 . Similarly, device  10 ′ may communicate wirelessly with device  8  over wireless communications link  36 ′. Additionally, device  10  may communicate with matching device  10 ′ over wireless communications link  38 . Communications link  38  may be wired if desired (e.g., link  38  may be implemented using wires or other conductive paths). If desired, one of communications links  36  and  36 ′ may be omitted. As an example, in a scenario in which only communications link  36  is established, device  10 ′ may communicate with device  8  through device  10  (e.g., using communications links  36  and  38 , thereby omitting link  36 ′). In another suitable arrangement, communications link  38  may be omitted. In this scenario, device  8  may communicate with devices  10  and  10 ′ using communications links  36  and  36 ′ respectively, and devices  10  and  10 ′ may communicate with each other through device  8 . 
     Wireless communications links  36 ,  36 ′, and  38  may be cellular telephone links (e.g., wireless links at frequencies of 700 MHz to 2700 MHz or other suitable cellular telephone frequencies), may be wireless local area network links operating at 2.4 GHz, 5 GHz, or other suitable wireless local area network frequencies, may be Bluetooth® links operating at 2.4 GHz or other suitable wireless personal area network frequencies, may involve millimeter wave communications, may involve near-field communications, or may involve wireless communications in other communications bands. Configurations in which devices  10  and  10 ′ operate at 2.4 GHz to support short-range communications such as Bluetooth® communications may sometimes be described herein as an example. 
     As shown in  FIG. 1 , device  10  (e.g., a headset or other accessory) may include control circuitry such as storage and processing circuitry  16 . Storage and processing circuitry  16  may include storage such as 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  16  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 processor integrated circuits, application specific integrated circuits, etc. 
     Storage and processing circuitry  16  may be used to run software on device  10 . The software may handle communications, may process sensor signals and take appropriate action based on the processed sensor signals (e.g., to turn on or off functions in device  10 , to start or stop audio playback, etc.), and may handle other device operations. To support interactions with external equipment  8 , storage and processing circuitry  16  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  16  include wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi® and WiGig), protocols for other short-range wireless communications links such as the Bluetooth® protocol or other wireless personal area network protocols, cellular telephone protocols, etc. 
     Device  10  may include microphones, speakers, tone generators, and other audio components (see, e.g., one or more speakers  14 ). Microphones may gather voice signals and/or ambient noise signals for noise cancellation functions. Speakers may play back sound for a user. Device  10  may, for example, be a wireless earbud or earphone that plays audio for a user using speaker  14  when at least some of device  10  is placed on, over, or within a user&#39;s ear. Device  10  may be paired to another device such as an additional earbud (e.g., device  10 ′). Device  10  may form an earbud pair with the additional earbud. Device  10  and the additional earbud may wirelessly communicate with an audio source (e.g., audio source  8  via communications links  36  and  36 ′) and/or may communicate with each other (e.g., for conveying audio data from the audio source to device  10  and device  10 ′ and/or for conveying audio data between the earbuds via communications link  38 ). The speaker in device  10  may play a first channel of stereo audio data (e.g., a left or right channel) whereas the speaker in device  10 ′ may play a second channel of stereo audio data. Tone generators and other sound output devices may generate other audible or non-audible outputs. Sensors and other components  20  in device  10  may include proximity sensors (e.g., capacitive proximity sensors, light-based proximity sensors, etc.), force sensors, buttons, magnetic sensors, accelerometers and other components for measuring device orientation and/or motion, strain gauge sensors, vibrators, connector components, printed circuit board structures, wiring structures, etc. 
     Device  10  may include battery  18  to provide power to the circuitry of device  10 . Battery  18  may be, for example, a rechargeable battery. Battery  18  may be recharged wirelessly (e.g., by providing device  10  with wireless power) or may be recharged via a wired connection between external equipment and device  10 . Configurations in which battery  18  is not rechargeable (e.g., in which battery  18  is a replaceable non-rechargeable battery) may also be used. Components  20  may include, if desired, a connector that is configured to receive a cable or other structure that, when connected to the connector, provide power to device  10  for charging battery  18 . 
     The components of device  10  may be housed within device housing  12 , which may sometimes be referred to as an enclosure or case. Housing  12  may, for example, be formed from of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel or aluminum), other dielectrics such as silicone, foam, or rubber, or a combination of any two or more of these materials. If desired, housing  12  may include an internal frame structure that is enclosed within other housing structures such as a silicone, rubber, or plastic outer casing. The outer casing may include combinations of these materials if desired. Housing  12  may, if desired, include earbud housing structures (e.g., rubber, plastic, or silicone housing structures that are sometimes referred to as earbud tip structures) that enclose speaker  14  but that are otherwise separated from other portions of housing  12 . The portions of housing  12  that cover speaker  14  may include a hole or other openings that align with speaker  14  to allow sound to be conveyed from speakers  14  to the exterior of device  10 . If desired, a conductive and/or dielectric mesh or other protective layer may be formed over the opening to protect the opening and the speaker from contaminants. 
     Electronic device  10  may include wireless circuitry for supporting wireless communications with external equipment. The wireless circuitry may include radio-frequency transceiver  22  and one or more antennas such as antenna  40 . Antenna  40  may have a feed that includes positive antenna feed terminal  42  and ground antenna feed terminal  44 . Transmission line  30  may be used to couple radio-frequency transceiver circuitry  22  to antenna  40 . Transmission line  30  may have a positive signal path such as line  32  and a ground signal path such as line  34 . More than one feed may be used for antenna  40  if desired (e.g., each feed may be coupled to a corresponding transmission line  30 ). Transmission lines in device  10  such as transmission line  30  may include coaxial cable paths, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, transmission lines formed from combinations of transmission lines of these types, etc. Filter circuitry, switching circuitry, impedance matching circuitry, and other circuitry may be interposed within the transmission lines, if desired. 
     Circuitry  22  may include any desired circuitry associated with the transmission and reception of radio-frequency signals using antenna  40 . For example, circuitry  22  may include baseband processor circuitry, amplifier circuitry (e.g., low noise and/or power amplifier circuitry), mixing circuitry such as up-converter and/or down-converter circuitry, converter circuitry such as analog-to-digital converter circuitry and/or digital-to-analog converter circuitry, etc. 
     Antenna  40  may be formed using any suitable antenna type. For example, antenna  40  may be an antenna with a resonating element that is formed from a loop antenna structure, a patch antenna structure, an inverted-F antenna structure, a slot antenna structure, a planar inverted-F antenna structure, a helical antenna structure, a monopole, a dipole, hybrids of these designs, etc. If desired, antenna  40  may include tunable circuitry and control circuitry  16  may be used to select an optimum setting for the tunable circuitry to tune antenna  40 . Antenna adjustments may be made to tune antenna  40  to perform communications in a desired frequency range or to otherwise optimize antenna performance. Antenna  40  may also be implemented using a fixed (non-tunable) configuration if desired. Multiple antennas  40  may be formed within device  10  if desired. 
     Device  10 ′ may include some or all of the same circuitry as device  10 . In particular, device  10 ′ may include control circuitry, one or more speakers, a battery, sensor circuitry, transceiver circuitry, antenna structure, housing structures, and any other components described in connection with device  10 . Devices  10  and  10 ′ may be enclosed by separate housing structures, or if desired, devices  10  and  10 ′ may be enclosed by a shared housing structure. 
     If desired, the housing of device  10 ′ may have the same shape as the housing of device  10 . While the housings of device  10 ′ and device  10  may be substantially identical, devices  10  and  10 ′ may be configured to perform different functions. For example, during audio playback operations, device  10  may be configured to perform left-channel specific operations, while device  10 ′ may be configured to perform right-channel specific operations in a multiple-channel audio configuration (e.g., a stereo configuration). As an example, device  10  may be an earbud configured to be placed in a left ear of a user and device  10 ′ may be an earbud configured to be placed in a right ear of the user. These examples of device  10 ′ are merely illustrative. As an example, details of device  10  (e.g., internal structures of device  10 , functionality of device  10 , etc.) described herein may similarly describe device  10 ′. Device  10  may be configured to perform right-channel specific operations whereas device  10 ′ performs left-channel specific operations if desired. 
     An illustrative configuration for antenna  40  is shown in  FIG. 2 . In the example of  FIG. 2 , antenna  40  is an inverted-F antenna and has inverted-F antenna resonating element  100  and antenna ground  102  (sometimes referred to herein as ground  102 , antenna ground plane  102 , or ground plane  102 ). Antenna resonating element  100  may have a main resonating arm such as arm  104 . The length of arm  104  may be selected such that antenna structure  40  resonates at desired operating frequencies. For example, the length of arm  104  (or a branch of arm  104 ) may be a quarter of a wavelength at a desired operating frequency for antenna  40 . Antenna structure  40  may also exhibit resonances at harmonic frequencies. If desired, slot antenna structures or other antenna structure may be incorporated into an inverted-F antenna such as antenna  40  of  FIG. 2  (e.g., to enhance antenna response in one or more communications bands). 
     Antenna  40  may be fed by coupling a transmission line (e.g., transmission line  30  of  FIG. 1 ) to antenna feed  108 . Antenna feed  108  has positive antenna feed terminal  42  coupled to resonating element arm  104  of antenna resonating element  100  and has ground antenna feed terminal  44  coupled to ground  102 . Return path  106  (i.e., a short circuit path) may be coupled between antenna resonating element arm  104  and ground  102  in parallel with feed  108 . If desired, inverted-F antenna structures such as illustrative antenna structure  40  of  FIG. 2  may have more than one resonating arm branch (e.g., to create multiple frequency resonances to support operations in multiple communications bands) or may have other antenna structures (e.g., parasitic antenna resonating elements, tunable components to support antenna tuning, etc.). If desired, antennas such as inverted-F antenna  40  of  FIG. 2  may have tunable components. 
     Antenna ground  102  may be formed from ground traces in a printed circuit or other substrate, metal portions of a battery, metal housing structures, metal portions of internal device components, metal walls of a speaker or an acoustic cavity, other conductive ground structures, or a combination of these structures in device  10 . Antenna resonating element  100  may be formed from metal printed circuit traces and/or other conductive structures in device  10  (e.g., metal foil, metal housing structures, stamped sheet metal, portions of internal device components, etc.). 
     If desired, antenna  40  may be a planar inverted-F antenna. When configured as a planar inverted-F antenna, resonating element arm  100  may be formed using a conductive structure that extend across a planar lateral area above ground  102  (e.g., a conductive sheet, a conductive trace, conductive foil, etc. that is separated from ground  102  by a predetermined distance). The perimeter of the conductive structure forming resonating element arm  100  may help to define the resonant frequency of antenna  40 , for example. 
     When antenna  40  transmits radio-frequency signals provided by transceiver circuitry, the performance of antenna  40  may be hindered by external objects in proximity of antenna  40  (e.g., the presence of an external object in the vicinity of antenna  40  may load and thus detune antenna  40 ). Such loading and detuning may be particularly pronounced when antenna  40  is loaded close to antenna feed  108 . For example, when an external object is present in close proximity to feed  108  such as at location X, antenna  40  may be significantly loaded by the external object causing antenna  40  to become mismatched with the impedance of transmission line  30 . This may cause antenna  40  to become detuned or to otherwise exhibit deteriorated antenna performance. However, when an external object is present at location that is relatively far from feed  108  such as location Y, antenna  40  may be detuned (e.g., the antenna efficiency may be degraded) less than in scenarios where the external object is at location X. 
     In practice, when device  10  is placed within a user&#39;s ear, the loading of antenna  40  and thus the radio-frequency performance of antenna  40  may be dependent upon how device  10  is placed (e.g., rotated) within the ear. For example, different parts of the user&#39;s ear or body may load antenna  40  more than others. In practice, it may be desirable to orient device  10  within the user&#39;s ear in such a way so as to place portions of the user&#39;s ear that significantly load antenna  40  farther from feed  108  than portions of the user&#39;s ear that do not significantly load antenna  40 . 
     Additionally, in general, playback operations may provide audio data for multi-channel playback (e.g., dual-channel or stereo playback), thereby requiring earphones to provide first and second audio channels (e.g., a left (ear) audio channel and a right (ear) audio channel, etc.). In practice, earphones may have an asymmetric housing that is specific for a particular channel or placement (e.g., the housing of an earbud for playing the left audio channel may be shaped to only fit within a user&#39;s left ear and not the user&#39;s right ear and the housing of an earbud for playing the right audio channel may be shaped to only fit within a user&#39;s right ear and not the user&#39;s left ear). In other words, a left-ear earbud in this scenario cannot be used as a right-ear earbud and vice versa. 
     However, in practice it would desirable to provide a symmetric housing for earphone devices (e.g., devices  10  and  10 ′ of  FIG. 1 ). A symmetric housing would allow either one of devices  10  and  10 ′ to be placed in either the user&#39;s left or right ear. This may, for example, facilitate the use of devices  10  and  10 ′ as earbuds for a user, because the user does not need to focus on ensuring that the correct earbud goes into a particular corresponding ear. 
     In this scenario, sensor circuitry or other circuitry may provide sensor data to the control circuitry in earphone devices  10  and  10 ′ so that the devices are aware of which ear they are placed in. Once this information is identified, the control circuitry may communicate with device  8  (e.g., over link  36  of  FIG. 1 ) to begin receipt of wireless audio data for the audio channel corresponding to the appropriate ear in which each device is placed. However, if care is not taken, the antenna feed may be located close to a portion of the user&#39;s ear or a portion the user&#39;s body that significantly loads the corresponding antenna, which causes the antenna to be detuned. Details of illustrative antenna structures that may be implemented within devices  10  and  10 ′ to mitigate these issues are described below. 
       FIG. 3  shows an illustrative electronic device  10  such as a headset, an earphone, an earbud, or any other playback device or accessory, having illustrative antenna structures with switchable configurations. As shown in  FIG. 3 , antenna structures  40  in electronic device  10  may have multiple antenna feeds such as feeds  108 - 1  and  108 - 2 . Antenna feed  108 - 1  may be formed at a first side  41 - 1  of antenna  40  (sometimes referred to herein as antenna portion  41 - 1  or antenna region  41 - 1 ). Antenna feed  108 - 2  may be formed at a second side  41 - 2  of antenna  40  (sometimes referred to herein as antenna portion  41 - 2  or antenna region  41 - 2 ). Antenna feed  108 - 1  may include a positive feed terminal  42 - 1  coupled to resonating element arm  104  of antenna  40  and a ground terminal  44 - 1  coupled to ground  102 . Antenna feed  108 - 2  may include a positive feed terminal  42 - 2  coupled to resonating element arm  104  and a ground feed terminal  44 - 2  coupled to ground  102 . Respective transmission lines (e.g., transmission lines such as transmission line  30  of  FIG. 1 ) may couple feeds  108 - 1  and  108 - 2  to transceiver circuitry  114  (e.g., transceiver circuitry  22  of  FIG. 1 ). For example, a first transmission line  30 - 1  may couple feed  108 - 1  to transceiver circuitry  114  whereas a second transmission line  30 - 2  may couple feed  108 - 2  to transceiver circuitry  114 . 
     A first return path  106 - 1  may be coupled between one end of resonating element arm  104  and ground  102  (e.g., within antenna region  41 - 1 ). A second return path  106 - 2  may be coupled between the opposing end of arm  104  and ground  102  (e.g., within antenna region  41 - 2 ). As an example, ground  102  may be formed using one or more components  116 . Components  116  that are used in forming ground  102  may, for example, include a conductive portion (e.g., a conductive casing or frame) of a battery (e.g., battery  18  of  FIG. 1 ), a conductive portion of a speaker, a conductive portion a sensor, and/or a conductive wall of an acoustic chamber. If desired, antenna  40  may be mounted to components  116  (e.g., return paths  106 - 1  and  106 - 2  may be soldered or welded to components  116 ). 
     Device  10  may include switching circuitry for adjusting antenna  40  between at least two different antenna configurations. For example, device  10  may include switching circuitry  110 - 1  interposed on return path  106 - 1  and switching circuitry  110 - 2  interposed on return path  106 - 2 . If desired, antenna feed switching circuitry  112  (sometimes referred to herein as feed selection switching circuitry) may be coupled between transceiver circuitry  114  and feeds  108 - 1  and  108 - 2  (e.g., switching circuitry  112  may be interposed on transmission lines  30 - 1  and  30 - 2 ). Control circuitry (e.g., control circuitry  16  of  FIG. 1 ) may provide control signals to switching circuitry  112 ,  110 - 1 , and  110 - 2  to control the antenna configuration of antenna  40 . For example, circuitry  110 - 1  and  110 - 2  may be controlled to selectively couple one or both sides of resonating element arm  104  to ground  102 . Circuitry  112  may be controlled to selectively couple one of feeds  108 - 1  and  108 - 2  to transceiver circuitry  114  (e.g., so that one of feeds  108 - 1  and  108 - 2  is active at a given time). 
     As an example, the control circuitry on device  10  may configure antenna  40  to operate in a selected one of first and second antenna configurations. In the first configuration, switch  110 - 1  may be closed (turned on or enabled), switch  110 - 2  may be open (turned off or disabled), and switching circuitry  112  may couple transceiver circuitry  114  to feed  108 - 1  (e.g., feed  108 - 1  may be enabled whereas feed  108 - 2  is disabled). In this first configuration, antenna return path  106 - 1  may be coupled between antenna resonating element arm  104  and ground  102  and feed  108 - 1  may be active within region  41 - 1  of antenna  40 . At the same time, return path  106 - 2  may form an open circuit between the end of resonating element arm  104  in region  41 - 2  and ground  102 . 
     In the second configuration, control circuitry switch  110 - 2  may be closed, switch  110 - 1  may be open, switching circuitry  112  may couple transceiver circuitry  114  to feed  108 - 2 , and feed  108 - 1  may be disabled. In this second configuration, antenna return path  106 - 2  may be coupled between antenna resonating element arm  104  and ground  102  and feed  108 - 2  may be active within region  41 - 2  of antenna  40 . At the same time, return path  106 - 1  may form an open circuit between the end of resonating element arm  104  in region  41 - 2  and ground  102 . 
     Device  10  may include housing  12  that encloses (e.g., surrounds) antennas regions  41 - 1  and  41 - 2 , and other components (e.g., speakers, battery, sensors, processing circuitry, etc.) within device  10 . Housing  12  may have any suitable shape. As examples, housing  12  may have a main body portion that is anatomical to an ear of a user (e.g., that has a shape that fits within the ear of the user) and an elongated portion that protrudes from the main body portion, may have two separate elongated portions that protrude from two different sides of the main body portion, may have no elongated portions and only a main body portion, etc. As an example, housing  12  may have mirror symmetry (i.e., plane symmetry) about at least one plane of symmetry within device  10  (e.g., a central plane indicated by dashed plane  118  perpendicular to the page). If desired, housing  12  may also have mirror symmetry about an additional plane of symmetry and/or may have rotational symmetry about a central axis. These examples are merely illustrative. If desired, housing  12  may have any one or more of the above-mentioned characteristics. 
     By providing device  10  with a symmetrical housing, device  10  may be placed in either one of the user&#39;s ears such that the speaker port of device  10  is aligned with the ear canal of the respective ear. Device  10  may still provide satisfactory antenna performance using antenna  40  in either one of the user&#39;s ears by placing antenna  40  in one of the first or second configurations (e.g., by coupling different antenna feeds and/or antenna return paths to transceiver circuitry). 
     Antenna  40  may be toggled between the first and second antenna configurations to efficiently operate in the presence of external objects. As an example, in a first environment, an external object may be located at location Y. The external object may be located significantly closer to feed  108 - 2  of antenna portion  41 - 2  than to feed  108 - 1  of antenna portion  41 - 1 . As a result, in the first environment, antenna portion  41 - 1  may operate more efficiently as the active portion of antenna  40  than antenna portion  41 - 2  (e.g., antenna  40  may be significantly detuned if feed  108 - 2  is active). In other words, in the first environment, antenna  40  on device  10  may operate in the first configuration (e.g., a configuration in which feed  108 - 1  is active and return path  106 - 1  is coupled into use and feed  108 - 2  is inactive) instead of operating in the second configuration (e.g., a configuration in which feed  108 - 1  is inactive and feed  108 - 2  is active). 
     As another example, in a second environment, an external object may be located at location X. The external object may be located significantly closer to feed  108 - 1  of antenna portion  41 - 1  than to feed  108 - 2  of antenna portion  41 - 2 . As a result, in the second environment, antenna portion  41 - 2  may operate more efficiently as the active portion of antenna  40  than antenna  41 - 1  (e.g., antenna  40  may be significantly detuned if feed  108 - 1  is active). In other words, in the second environment, antenna  40  on device  10  may operate in the second configuration (e.g., a configuration in which feed  108 - 1  is inactive and feed  108 - 2  is active and return path  106 - 1  is couple into use) instead of operating in the first configuration. 
     Control circuitry  16  on device  10  may actively receive sensor data that monitors the environment of device  10  (e.g., determine whether device  10  is in the first or second environment, is in an environment more closely resembling the first or second environment, etc.) and adjust the configuration of the antenna structures on device  10  accordingly to maximize antenna efficiency, thereby enhancing antenna performance and lowering power consumption of device  10 . As described in connection with  FIG. 1 , device  10  may include sensors or sensor circuitry that generate the sensor data that is used to determine the current environment for device  10 . By determining the current environment for device  10  using the sensor data, control circuitry  16  in device  10  may select one of the two configurations described above to implement in antenna  40 . In other words, antenna  40  may implement a more optimal configuration of the two configurations with respect to the detuning characteristics of the environment. The example of  FIG. 3  is merely illustrative. If desired, the structures shown in  FIG. 3  may also be used in a paired device (e.g., device  10 ′ of  FIG. 1 ). 
     While  FIG. 3  shows an electronic device having a single antenna with switchable feeds and/or return paths, in another suitable embodiment, an electronic device such as device  10  may include multiple separate switchable antennas.  FIG. 4  shows an illustrative electronic device  10  (e.g., a headset, earphone, earbud, etc.) that includes two separate antennas (e.g., a first antenna  40 - 1  and a second antenna  40 - 2 ). 
     As shown in  FIG. 4 , antenna  40 - 1  may include a corresponding antenna resonating arm  104 - 1  that conveys antenna signals for feed  108 - 1 . Feed  108 - 1  may be coupled to transceiver circuitry  114  via a corresponding transmission line  30 - 1 . Antenna  40 - 1  may include return path  106 - 1  that couples one end of antenna resonating arm  104 - 1  to ground  102 . Similarly, antenna  40 - 2  may include antenna resonating arm  104 - 2  that conveys antenna signals for feed  108 - 2 . Feed  108 - 2  may be coupled to transceiver circuitry  114  via transmission line  30 - 2 . Antenna  40 - 2  may include return path  106 - 2  that couples one end of antenna resonating arm  104 - 2  to ground  102 . The other end of antenna resonating arm  104 - 2  (e.g., the floating end of arm  104 - 2  not coupled to return path  106 - 2 ) may be interposed between antenna resonating arm  104 - 1  (e.g., the floating end of antenna resonating arm  104 - 1 ) and antenna feed  108 - 2 . Similarly, the floating end of antenna resonating arm  104 - 1  may be interposed between the floating end of antenna resonating arm  104 - 2  and antenna feed  108 - 1 . In this configuration, antennas  40 - 1  and  40 - 2  may be formed on opposing sides of housing  12  and/or device  10 . In particular, antenna return paths  106 - 1  and  106 - 2  may be formed on opposing sides of housing  12  and/or device  10 , and antenna feeds  108 - 1  and  108 - 2  may be formed on opposing sides of housing  12  and/or device  10 . Antenna resonating arms  104 - 1  and  104 - 2  may be formed as separate conductors in this example. 
     As shown in  FIGS. 3 and 4 , antenna resonating arm  104  in  FIG. 3  and antenna resonating arm in  FIG. 4  may be curved. The curvature of these antenna resonating element arms may conform to a shape of ground structures such as ground  102 , a shape of internal components such as components  116  or battery  18 , and or a shape of housing  12 . This is merely illustrative. If desired, antenna resonating arms in antenna  40  of  FIGS. 3 and 4  may be planar and not curved. 
     Additionally, device  10  in  FIG. 4  may also include components such as a speaker, a battery, sensor circuitry, other components, similar to components  116  described in connection with  FIG. 3 . If desired, additional components such as speaker(s), a battery, sensor circuitry, control circuitry, etc.) may form portions of antennas  40 - 1  and  40 - 2  (e.g., grounding structures for antennas  40 - 1  and  40 - 2 ) as an example. If desired, antennas  40 - 1  and  40 - 2  may be mounted to these components (e.g., return paths  106 - 1  and  106 - 2  may be soldered or welded to these components). 
     If desired, antenna feed switching circuitry  120  may be coupled between feeds  108 - 1  and  108 - 2  and transceiver circuitry  114  (e.g., switching circuitry  120  may be interposed between the antenna feeds and the transceiver circuitry). Switching circuitry  120  may be controlled to selectively activate a given one of antennas  40 - 1  and  40 - 2  at a time (e.g., based on the locations of external objects in the environment of device  10  or based on other sensor information). 
     For example, when an object is present at location Y, control circuitry  16  may configure switch  120  to couple antenna  40 - 1  to transceiver circuitry  114  and to decouple antenna  40 - 2  from transceiver circuitry  114 . In this scenario, antenna  40 - 1  relatively far from location Y and would therefore not be significantly loaded or detuned by objects at location Y. However, antenna  40 - 2  is relatively close to location Y and, if active, would be significantly loaded and detuned. In contrast, when an object is present at location X, control circuitry  16  may configure switch  120  to exclusively couple antenna  40 - 2  to transceiver circuitry  114 . In this scenario, antenna  40 - 2  is relatively far from location X and would therefore not be significantly loaded or detuned by objects at location X. However, antenna  40 - 1  is relatively close to location X and, if active, would be significantly loaded detuned. In this way, an optimal antenna that is most immune to loading and detuning by external objects may be active at any given time. 
     The example of  FIG. 4  is merely illustrative. If desired, antennas  40 - 1  and  40 - 2  may be separately coupled to one or more transceiver circuits (e.g., switching circuitry  120  may be omitted). If desired, device  10  may include antennas or antenna structures in addition to antennas  40 - 1  and  40 - 2 , and control circuitry may configure antennas  40 - 1  and  40 - 2  such that both antennas are simultaneously inactive while the additional antennas are activate. 
     Antennas  40 - 1  and  40 - 1  in  FIG. 4  may have reflective symmetry about a central plane (e.g., a plane into and out of the page as indicated by plane  118 ). If desired, antennas  40 - 1  and  40 - 2  may have resonating element arms of the same length or different lengths (e.g., arms  104 - 1  and  104 - 2  may have the same or different lengths). Antennas  40 - 1  and  40 - 2  may cover the same frequencies or may cover two or more different frequencies. Using antennas having resonating element arms formed from separate conductive structures may reduce the amount of undesired current leakage relative to scenarios where the same conductive structure is used by both feeds  108 - 1  and  108 - 2  (e.g., as shown in  FIG. 3 ). 
       FIG. 5  shows a perspective view of an illustrative electronic device having antenna structures of the type shown in  FIG. 4  while placed in a user&#39;s left ear. As shown in  FIG. 5 , device  10  may include housing  12  that surrounds components  130 , antennas  40 - 1  and  40 - 2 , speaker  140 , and other components. Housing  12  may include a main body portion  132  and an extended or protruding portion  134 . Main body portion  132  may house control circuitry, processing circuitry, transceiver circuitry, antennas, a battery, and any other suitable components. Protruding portion  134  may house speaker port  142  that may be aligned with speakers  140  for device  10 . Speaker port  142  may be formed in the surface of housing  12  through which sound is provided to the ear of the user. Speaker port  142  may be formed from one or more openings in housing  12 . One or more plastic or metal mesh layers may be interposed between speaker  140  and the one or more openings that form the speaker port  142  (e.g., to help prevent the intrusion of dust and other contaminants into the speaker). Speaker  140  may be formed in main body portion  132 , as an example. Alternatively, protruding portion  134  may be omitted and openings that form speaker ports may be formed in main body portion  132 , as an example. 
     Antennas  40 - 1  and  40 - 2  may be formed on (mounted to) component  130  of device  10 . As examples, component  130  may include flexible substrates, rigid substrates, printed circuit substrates, a battery, a portion of housing  12 , a ground plane, or any combination of these components and any additional suitable components. In particular, component  130  may be a battery, and a portion of the battery (e.g., first and second opposing sides of the battery) may form a portion of ground  102 . Return paths  106 - 1  and  106 - 2  may be coupled to ground  102  at the first and second opposing sides of the battery, respectively. Component  130  such as a battery may have first and second curved surfaces (on different sides of component  130 ) over which antenna resonating element arms  104 - 1  and  104 - 2  are respectively formed. If desired, antenna resonating element arms  104 - 1  and  104 - 2  may extend parallel to the first and second respective curved surfaces of component  130  (e.g., resonating element arms  104 - 1  and  104 - 2  may also be curved and have the same curvature as a curved surface of component  130 ). Antenna structures (e.g., resonating element arms, feeds, return paths) associated with antennas  40 - 1  and  40 - 2  may have reflective symmetry about a plane into and out of the page such as plane  118 , as described in connection with  FIG. 4 . 
     When device  10  is placed in the left ear of a user (as shown in  FIG. 5 ), the antenna feed associated with antenna  40 - 1  (e.g., feed  108 - 1  as shown in  FIG. 4 ) may be in proximity to a higher-density portion of the user&#39;s ear than antenna  40 - 2 . The higher density portion of the user&#39;s ear will load and detune an adjacent antenna than lower density portions of the user&#39;s ear. As such, when device  10  is placed in the user&#39;s ear as shown in  FIG. 5 , antenna  40 - 1  may be loaded and detuned more than antenna  40 - 2 . 
     In order to mitigate this, control circuitry  16  on device  10  may configure switching circuitry (e.g., switching circuitry  120  shown in  FIG. 4 ) to couple feed  108 - 2  associated with antenna  40 - 2  to transceiver circuitry  114  as shown in  FIG. 4 , and optionally decouple feed  108 - 1  associated with antenna  40 - 1  from transceiver circuitry  114 , as an example. Configured in this way, device  10  may use antenna  40 - 2 , which is subject to less dielectric loading and detuning, to convey wireless signals. Feed  108 - 2  of antenna  40 - 2  may be pointed in an upward direction (e.g., away from the higher density portion of the ear) and away from an object at location z. By activating antenna  40 - 2 , device  10  may exhibit improved antenna performance (e.g., less data loss, reduce risk of dropping communications link  36 , etc.) than in scenarios where antenna  40 - 1  is activated. 
     Because antenna structures (e.g., antennas  40 - 1  and  40 - 2 ) may have at least reflective symmetry about a plane of symmetry that bisects antennas  40 - 1  and  40 - 2  into symmetrical halves, the same device  10  may also be used in a right ear of the user. In particular, when device  10  is placed in the right ear of the user, device  10  may have a configuration that is rotated about axis  118  by 180 degrees from the configuration in the user&#39;s left ear as shown in  FIG. 5 . In this rotated right-ear configuration, the antenna feed associated with antenna  40 - 2  in device  10  (e.g., the antenna feed of the downward facing antenna) may be in closer proximity to the body of the user than is the antenna feed associated with antenna  40 - 1  in device  10 . As such, the performance of antenna  40 - 2  in device  10  (e.g., the downward facing antenna) may be significantly affected by the presence of the body of the user. In this scenario, control circuitry  16  on device  10  may configure switching circuitry to couple the feed associated with antenna  40 - 1  (e.g., the upward facing antenna) to transceiver circuitry  114  in device  10 , and to optionally decouple the feed associated with antenna  40 - 2  from transceiver circuitry  114 . As such, when device  10  is placed in the right ear of the user, the active antenna may have an antenna feed that is pointed in an upward direction and away from the body of the user. In this way, an optimal antenna may be selected based on which ear device  10  is located in, allowing a user to place device  10  in either ear without significantly impacting antenna performance. 
     The symmetry of antennas  40 - 1  and  40 - 2  on device  10  allows device  10  to be placed in the left ear or the right ear of the user. When placed in the right ear, control circuitry  16  may activate antenna  40 - 1  (e.g., the upward facing antenna) and deactivate antenna  40 - 2 . Similarly, when placed in the left ear, control circuitry  16  may activate antenna  40 - 2  and deactivate antenna  40 - 1 . By providing this flexibility in using device  10 , a user is not required to place device  10  in a correct ear. 
     Control circuitry  16  may use sensor circuitry (e.g., sensors) in device  10  to determine the ear in which device  10  is placed (e.g., the current operating environment of device  10 ). As examples, sensors such as accelerometers, optical sensors, gyroscopes, proximity sensors (e.g., capacitive proximity sensors), ambient light sensors, and/or any other sensors may gather sensor data associated with the relative motion, position, and/or orientation of device  10 . Control circuitry  16  may receive the gathered sensor data and use the sensor data to determine the ear in which device  10  is placed. 
     The examples described in connection with  FIG. 5  are merely illustrative. If desired, the antenna structures shown in  FIG. 3  may similarly be used in device  10 . In this scenario, antenna feed  108 - 2  and return path  106 - 2  may be switched into use when device  10  is placed in the user&#39;s left ear and antenna feed  108 - 1  and return path  106 - 1  may be switched into use when device  10  is placed in the user&#39;s right ear, for example. Similar structures may also be used to form a device that is paired with device  10  (e.g., an earbud such as device  10 ′ of  FIG. 1  that forms a pair of earbuds with device  10 ). When configured in this way, device  10  may be operable as either a right-ear earbud or a left-ear earbud without significantly deteriorating antenna performance. This may, for example, facilitate use of device  10  by a user (e.g., so that the user need not focus on which ear device  10  is placed within) while still allowing a reliable wireless link with device  8  (e.g., thereby minimizing audio data errors and the risk of the wireless link being dropped). 
     Antenna performance of antennas on device  10  as shown in  FIGS. 3-5  may be sensitive to how device  10  is placed (e.g., rotated or oriented) within a user&#39;s ear canal. For example, in some orientations, both antennas  40 - 1  and  40 - 2  in  FIG. 5  may be unsatisfactorily detuned. As such, it may be desirable to provide devices with more than two antennas (or more than two switchable feeds and return paths in the example of  FIG. 3 ).  FIG. 6  shows an illustrative electronic device  10  that may be rotationally symmetric about axis  118 . In particular, device  10  may include more than two antennas such as antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 . Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may each have a respective antenna resonating element (e.g., antenna resonating element arms  104 - 1 ,  104 - 2 ,  104 - 3 , and  104 - 4 ). Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may also have corresponding return paths and corresponding antenna feeds such as return path  106  and feed  108 , which are omitted from  FIG. 6  for the sake of clarity. 
     The antenna resonating elements for antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  have the same length and/or perimeter. In other words, these antenna resonating elements may cover the same frequency bands. However, if desired, antenna resonating elements for antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may have different lengths and/or perimeters such that one or more of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  cover different frequency bands. 
     The antenna resonating elements may all be formed on a shared device component (e.g., component  156  or structure  156 ). Component  156  may be similar to component  116  described in connection with  FIGS. 3 and 4  (e.g., component  156  may be a speaker, a battery, a sensor, a substrate, or any other component). As examples, antenna resonating elements  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may share a common antenna ground formed from a portion of structure  156 , may all be mounted (e.g., soldered) to component  156 , etc. As shown in  FIG. 6 , each antenna resonating element arms  104 - 1 ,  104 - 2 ,  104 - 3 , and  104 - 3  may each be formed on a respective side of component  156  (e.g., on a respective side of housing  12  or device  10 ). As an example, component  156  may have a circular or spherical shape. However, this is merely illustrative. If desired, component  156  may be of any suitable shape. As an example, component  156  may be any of the components described in connection with component  130  in  FIG. 5 . 
     Antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may be evenly distributed about axis  118 . In other words, the antenna may be separated from each other by approximately 90 degrees about axis  118 . If desired, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may have reflective symmetry (i.e., plane symmetry) about at least two perpendicular planes of symmetry with respective to each other. Because component  156  may have a rectangular, cubic, spherical, or cylindrical shape, housing  12  may also have a rectangular, cubic, spherical, or cylindrical shape. The shape of housing  12  may also accommodate other components within device  10 . The example of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  being evenly distributed about axis  118  is merely illustrative. If desired, antennas may be unevenly distributed about axis  118  (e.g., on one side of housing  12 ), may be evenly distributed on a side of component  156 ), etc. As an example, device  10  may include antennas that are separated from each other by 15 degrees, 30 degrees, 45 degrees, 60 degrees, etc., about axis  118 . In particular, component  156  such as a battery may form a portion of an antenna ground. Antenna  40 - 1  may be mounted on a first side of component  156 , antenna  40 - 2  may be mounted on a second side of component  156 , antenna  40 - 3  may be mounted on a third side of component  156 , and antenna  40 - 4  may be mounted on a fourth side of component  156 . In other words, respective antenna resonating element arms of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may be formed on the first, second, third, and fourth sides of component  156 , respectively. 
     Housing  12  may include main body portion  152  that surrounds component  156 . Main body portion  152  may house control circuitry, processing circuitry, transceiver circuitry, antennas, a battery, and any other suitable components, as described in connection with  FIG. 5 . Housing  12  may also include protruding portion  154  that may house a speaker port and other suitable components. Alternatively, protruding portion  154  may be omitted and the speaker port may be formed from main body portion  152  of housing  12 . Housing  12 , which encloses symmetrical components within device  10  (e.g., symmetrical antenna structures  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 ) may have reflective symmetry about at least two perpendicular planes of symmetry. 
     Device  10  in  FIG. 6  may also include transceiver circuitry and switching circuitry (e.g., transceiver circuitry  114  and switching circuitry  120  as shown in  FIG. 4 ). Each of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may be selectively coupled (via respective antenna feeds) to the transceiver circuitry using the switching circuitry. In other words, the control circuitry in device  10  may control the switching circuitry to selectively couple an antenna, such as antenna  40 - 1 , to the transceiver circuitry. As an example, the coupling of a particular antenna (e.g., the most optimal of the antennas on device  10 , antenna  40 - 1 ) via the switching circuitry may be exclusive. In other words, when antenna  40 - 1  is coupled to the transceiver circuitry, antennas  40 - 2 ,  40 - 3 , and  40 - 4  may be decoupled from the transceiver circuitry. 
     Control circuitry in device  10  may select an optimal antenna to be used in device  10  based on the operating environment of device  10  (e.g., an antenna that is least susceptible to loading and detuning in the current environment, an antenna that is located furthest way from higher-density portion of a user&#39;s ear, an antenna facing away from a user&#39;s head). As an example, when the performance of antennas  40 - 2 ,  40 - 3 , and  40 - 4  are hindered by an external object (e.g., a user&#39;s torso, portions of a user&#39;s ear, etc.), the control circuitry may select and activate antenna  40 - 1  as the optimal antenna. As another example, when the performance of antennas  40 - 1 ,  40 - 2 , and  40 - 3  is hindered by an external object, the control circuitry may select and activate antenna  40 - 4  as the optimal antenna. By placing the most optimal antenna into use, device  10  may adapt to the environment in real-time such that a user no longer has to focus on how device  10  is oriented when placed the user&#39;s ear. As previously described in connection with  FIG. 5 , because device  10  in  FIG. 6  includes symmetrical antenna structures (e.g., antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 ), device  10  in  FIG. 6  may be placed in the user&#39;s left or right ears and the active antenna may be selected in real time to compensate for any potential detuning. 
     Alternatively, two or more antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  (e.g., both antennas  40 - 1  and  40 - 4 ) may be coupled to transceiver circuitry simultaneously. In this scenario, antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  may be configured to cover communications over different frequency bands, perform MIMO (multiple-input-multiple-out) functions over the same frequencies, perform transmitting and receiving functions separately, etc., as examples. Additionally, control circuitry  16  on device  10  may configure the switching circuitry to select more than one of antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4  as active antennas that mitigate detuning issues associated with the presence of the body of the user or other objects. The example of device  10  in  FIG. 6  is merely illustrative. If desired, device  10  in  FIG. 6  may include two antennas, three antennas, more than four antennas, etc. One or more of the antennas in device  10  may have the same shape or different shapes. The antennas may be located at any desired location on device  10 . 
     Details regarding the antenna feeds, return paths, transceiver circuitry, switching circuitry associated with the antennas structures for device  10  are omitted from  FIGS. 5 and 6  for the sake of clarity. In particular, device  10  in  FIG. 5  may also include antenna feeds, return paths, transceiver circuitry, and switching circuitry such as feeds  108 - 1  and  108 - 2 , return paths  106 - 1  and  106 - 2 , transceiver circuitry  114 , and switching circuitry  120  as shown in  FIG. 4 . Additionally, device  10  in  FIG. 6  may also include antenna feeds, return paths, transceiver circuitry, and switching circuitry similar to those shown in  FIG. 4 . As an example, switching circuitry may be interposed between each antenna feed of an antenna (e.g., antennas  40 - 1 ,  40 - 2 ,  40 - 3 , and  40 - 4 ) and transceiver circuitry. Control circuitry may be coupled to the switching circuitry to selectively activate one of the antennas. 
       FIG. 7  is a flowchart of illustrative steps for operating (e.g., configuring) devices having antennas structures of the types shown in  FIGS. 3-6 . At step  160 , sensor circuitry (e.g., sensors  20  in  FIG. 1 ) on device  10  may gather sensor data reflective of the operating environment of device  10 . As examples, sensors  20 , such as accelerometers, optical sensors, gyroscopes, proximity sensors (e.g., capacitive proximity sensors), ambient light sensors, and/or any other sensors, may gather sensor data associated with the relative motion, position, and/or orientation of device  10  (e.g., data indicative of whether a user has placed device  10  in a left ear, a right ear, or no ear and optionally indicative of how the device is oriented within the ear). If desired, electronic device  8  in  FIG. 1  may also provide sensor data to device  10  via communications link  36  to determine the relative motion, position, and/or orientation of device  10  (e.g., electronic device  8  may provide user input to device  10  regarding earbud position). If desired, control circuitry  16  in device  10  may identify a stereo channel based on the placement of device  10 . As an example, device  10  may also receive user input to determine the orientation of an earbud. 
     If desired, control circuitry  16  may monitor the signal quality of link  8  by gathering wireless performance metric data as sensor data associated with communications links  36  and  38 . The wireless performance of devices  10  and  10 ′ (e.g., the quality of communications link  36 ) may be characterized by one or more wireless performance metrics (e.g., radio-frequency performance metrics). Device  10  (e.g., control circuitry  16  or other circuitry on device  10 ) or device  8  may obtain data associated with wireless performance metrics. As an example, device  10  or  8  may generate wireless performance metric data and/or may receive wireless performance metric data from other devices. 
     As examples, device  10  may obtain wireless performance metric data associated with wireless performance metrics such as received power, receiver sensitivity, receive band noise (e.g., a receive band noise floor voltage level), frame error rate, bit error rate, packet error rate, channel quality measurements based on received signal strength indicator (RSSI) information, adjacent channel leakage ratio (ACLR) information (e.g., ACLR information in one or more downlink frequency channels), any desired combination of these performance metrics, rates of change over time of these performance metrics, and other information that is reflective of the performance of wireless circuitry on device  8  and/or device  10 . If desired, device  10  may gather wireless performance metric data on a per-antenna/per-antenna feed basis to determine the performance of each antenna and select an optimally performing antenna that may be activated in step  162 . As an example, antennas  40 - 1  and  40 - 2  of device  10  in  FIG. 5  may transmit test signals, and sensor circuitry on device  10  may generate wireless signal metrics data that determine whether antenna  40 - 1  is detuned. In response to determining that antenna  40 - 1  is detuned, control circuitry  16  may determine that device  10  is placed in a left ear of the user. 
     At step  162 , control circuitry  16  may configure antennas structures on device  10  with the appropriate settings (e.g., place one or more optimal antennas into active operation) based on the earbud orientation and/or gathered sensor data. As an example, in response to determining the relative positioning between antennas  40 - 1  and  40 - 2  based on the performance of the antennas, control circuitry  16  may activate the upper antenna (e.g., the antenna pointing towards the top of the user&#39;s ear or the sky) and deactivate the lower antenna (e.g., the antenna pointing towards the user&#39;s torso or the ground), as the lower antenna is more likely to be significantly detuned by the presence of the body of the user (e.g., due to a higher physiological density in the bottom part of a user&#39;s ear than the top part of the user&#39;s ear). As another example, in response to determining the relative positioning of antenna portions  41 - 1  and  41 - 2  in within device  10  in the example of  FIG. 3 , control circuitry may activate an upward facing portion such as portion  41 - 1  of antenna structures  40  (e.g., control circuitry may control switching circuitry to couple antenna feed  108 - 1  to transceiver circuitry  114  and to couple resonating element arm  104  to ground  102  using return path  106 - 1 ). If desired, device  10  may communicate with device  8  to convey configuration information of device  10  to device  8  (e.g., device  8  may receive information from device  10  that device  10  is in a left ear of the user). In response, device  8  may provide device  10  with an appropriate audio stream (e.g., a left-channel audio stream). These examples are merely illustrative. If desired, any suitable configuration of antenna structures on device  10  may be used. 
     Control circuitry may perform steps  160  and  162  in real-time, continuously, when prompted by user input, at a given time interval or frequency. As an example, sensor circuitry may be prompted to collect sensor data to determine device orientation, when awaken by the user (e.g. in response to touch, or in response to other stimuli). After device  10  is properly configured (e.g., after processing steps  160  and  160  one or more times), device  10  may perform operations such as receiving audio data over an antenna of device  10  and playing the audio data without interruption. The illustrative flowchart of  FIG. 7  may be performed continuously to update the configuration of device  10  (e.g., when the orientation of device  10  changes, when device  10  is removed from an ear, when device  10  is moved to the other ear, etc.). 
       FIG. 8  shows a diagram of illustrative antenna efficiency curves for antennas configured in multiple configurations such as the illustrative antennas described in connection with  FIGS. 3-6 . In particular,  FIG. 8  shows a graph in which antenna efficiency has been plotted as a function of frequency. As described in connection with  FIGS. 3-6 , an object in close proximity to a feed for an antenna may significantly detune the antenna. In order to mitigate the detuning of the antenna, antenna structures may be provided with multiple configurations that include multiple switchable feeds and/or antennas, and an optimal feed and/or antenna may be selected and activated. 
     For example, as described in connection with  FIG. 4 , the antennas structures  40  may be configured to activate either feed  108 - 1  or  108 - 2 . An active feed such as feed  108 - 1  may be selected instead of feed  108 - 2  when an object is located at location Y in  FIG. 4 . Curve  180  in  FIG. 8  provides an illustrative antenna efficiency curve for antenna structures having an optimal active feed (e.g., feed  108 - 1  in the presence of an object at location Y in  FIG. 4 ). Curve  182  in  FIG. 8  provides an illustrative antenna efficiency curve for antenna structures having a suboptimal feed (e.g., feed  108 - 2  in the presence of an object at location Y in  FIG. 4 ). When configuring antenna structures to use a suboptimal feed, antenna efficiency suffers over all frequencies in a frequency band (e.g., all frequencies between frequency F L  and F H ). As such, performing communications operations at a desired frequency (e.g., Bluetooth® frequency band center at 2.4 GHz) using the antenna structures may be severely degraded. However, by selecting an optimal active feed, antenna structure may perform communications operations with enhanced efficiency when compared to the scenario in which a suboptimal feed is used. 
     This example is merely illustrative. If desired, antenna structures as shown in  FIGS. 4-6  may similarly select an optimal active antenna and/or antenna feed to perform communications operations with enhance efficiency in the presence of an external object. Multiple bands may be covered if desired. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20170929
Publication Date: 20210309
Grant Date: 20210309
Priority Date: 20170929
Inventors: COUSINS, Benjamin A.
DI NALLO, CARLO
HUWE, ETHAN L.
GUTERMAN, Jerzy S.
HAMMERSCHMIDT, JOACHIM S.
PASCOLINI, MATTIA
CABALLERO, RUBEN
PARKER, Samuel G.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R2225/51", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q7/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/385", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2420/07", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/273", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/1058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q1/273", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/385", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2420/07", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/1058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1041", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1041", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q7/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2225/51", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/273", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1041", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q7/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/385", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2225/51", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2420/07", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 65896266