PATENT DOCUMENT

Publication Number: US-9166634-B2
Application Number: US-201313888110-A
Country: US
Kind Code: B2

Title: Electronic device with multiple antenna feeds and adjustable filter and matching circuitry

Abstract:
Electronic devices may include antenna structures. The antenna structures may form an antenna having first and second feeds at different locations. A first transceiver may be coupled to the first feed using a first circuit. A second transceiver may be coupled to the second feed using a second circuit. The first and second feeds may be isolated from each other using the first and second circuits. The second circuit may have a notch filter that isolates the second feed from the first feed at operating frequencies associated with the first transceiver. The first circuit may include an adjustable component such as an adjustable capacitor. The adjustable component may be placed in different states depending on the mode of operation of the second transceiver to ensure that the first feed is isolated from the second feed.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 an antenna having first and second feeds; 
 a first radio-frequency transceiver circuit operable in at least a first communications band; 
 a second radio-frequency transceiver circuit operable in at least second and third communications bands; 
 a first circuit coupled between the first radio-frequency transceiver circuit and the first feed; 
 a second circuit coupled between the second radio-frequency transceiver circuit and the second feed, wherein the first and second circuits are formed from separate components; and 
 control circuitry configured to place the first circuit in a first state while operating the second radio-frequency transceiver circuit in the second communications band and configured to place the first circuit in a second state that is different from the first state while operating the second radio-frequency transceiver circuit in the third communications band. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the second radio-frequency transceiver circuit is further operable in a fourth communications band and wherein the control circuitry is further configured to place the first circuit in a third state that is different from the first and second states while operating the second radio-frequency transceiver circuit in the fourth communications band. 
     
     
       3. The electronic device defined in  claim 2  wherein the first radio-frequency transceiver circuit is configured to receive signals with the antenna in the first communications band while the second radio-frequency transceiver circuit transmits signals with the antenna in the second communications band. 
     
     
       4. The electronic device defined in  claim 3  wherein the first communications band is a satellite navigation system communications band, wherein the second, third, and fourth communications bands are cellular telephone communications bands, and wherein the first circuit comprises an inductor. 
     
     
       5. The electronic device defined in  claim 4  wherein the first circuit comprises an adjustable capacitor. 
     
     
       6. The electronic device defined in  claim 5  wherein the adjustable capacitor is coupled in parallel with the inductor between the first feed and the first radio-frequency transceiver circuit. 
     
     
       7. The electronic device defined in  claim 6  wherein the adjustable capacitor is configured to exhibit a first capacitance in the first state, a second capacitance that is different from the first capacitance in the second state, and a third capacitance that is different from the first and second capacitances in the third state. 
     
     
       8. The electronic device defined in  claim 7  wherein the second circuit comprises a tuning circuit that is configured to tune the antenna. 
     
     
       9. The electronic device defined in  claim 8  wherein the control circuitry is configured to tune the tuning circuit to exhibit a selected capacitance value, wherein the tuning circuit adjusts an antenna resonance for the antenna in the second communications band. 
     
     
       10. The electronic device defined in  claim 1  wherein the first circuit comprises an adjustable band stop filter. 
     
     
       11. The electronic device defined in  claim 10  wherein the first feed is isolated from the second feed in the second communications band when the first circuit is placed in the first state and wherein the first feed is isolated from the second feed in the third communications band when the first circuit is placed in the second state. 
     
     
       12. The electronic device defined in  claim 11  further comprising a conductive housing structure that forms part of the antenna. 
     
     
       13. The electronic device defined in  claim 12 , wherein the electronic device has a rectangular periphery and wherein the conductive housing structure comprises a segment of a metal peripheral conductive housing structure that runs around the rectangular periphery. 
     
     
       14. The electronic device defined in  claim 12  wherein the antenna comprises an inverted-F antenna. 
     
     
       15. Apparatus, comprising:
 an antenna resonating element; 
 an antenna ground; 
 a return path between the antenna resonating element and the antenna ground; 
 a first feed coupled to the antenna resonating element; 
 a second feed coupled to the antenna resonating element; 
 a first transceiver; 
 a first circuit coupled between the first feed and the first transceiver; 
 a second transceiver; and 
 a second circuit coupled between the second feed and the second transceiver, wherein the second circuit is separate from the first circuit and the first circuit comprises an adjustable capacitor that is adjusted to isolate the first feed from the second feed at signal frequencies associated with operation of the second transceiver. 
 
     
     
       16. The apparatus defined in  claim 15  further comprising a peripheral conductive housing structure that forms at least part of the antenna resonating element. 
     
     
       17. The apparatus defined in  claim 16  further comprising an inductor coupled in parallel with the adjustable capacitor. 
     
     
       18. The apparatus defined in  claim 17  wherein the second circuit includes a notch filter. 
     
     
       19. An electronic device, comprising:
 an antenna having at least first and second feeds; 
 a first circuit coupled to the first feed; 
 a second circuit coupled to the second feed; 
 a satellite navigation system transceiver that receives signals from the antenna through the first circuit; 
 a cellular telephone transceiver operable in at least first, second, and third communications bands, wherein the first circuit has an adjustable component with a first setting that isolates the first feed from the second feed when the cellular telephone transceiver transmits signals with the antenna through the second circuit in the first communications band, a second setting that isolates the first feed from the second feed when the cellular telephone transceiver transmits signals with the antenna through the second circuit in the second communications band, and a third setting that isolates the first feed from the second feed when the cellular telephone transceiver transmits signals with the antenna through the second circuit in the third communications band. 
 
     
     
       20. The electronic device defined in  claim 19 , wherein the adjustable component comprises an adjustable capacitor, the first communications band includes at least one frequency from 700 to 960 MHz, the second communications band includes at least one frequency from 1710 to 2170 MHz, and the third communications band includes at least one frequency from 2300 to 2700 MHz.

Description:
BACKGROUND 
     This relates generally to electronic devices, and more particularly, to antenna structures for electronic devices with wireless communications circuitry. 
     Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry to communicate using cellular telephone bands. Electronic devices may use short-range wireless communications circuitry such as wireless local area network communications circuitry to handle communications with nearby equipment. Electronic devices may also be provided with satellite navigation system receivers and other wireless circuitry. 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components using compact structures. At the same time, it may be desirable to include conductive structures in an electronic device such as metal device housing components. Because conductive components can affect radio-frequency performance, care must be taken when incorporating antennas into an electronic device that includes conductive structures. Moreover, care must be taken to ensure that the antennas and wireless circuitry in a device are able to exhibit satisfactory performance over a range of operating frequencies. 
     It would therefore be desirable to be able to provide improved antenna structures for wireless electronic devices. 
     SUMMARY 
     Electronic devices may include antenna structures. The antenna structures may form an antenna having first and second feeds at different locations. The antenna may be an antenna such as an inverted-F antenna formed from a portion of a conductive housing structure such as a segment of a peripheral conductive housing structure. 
     A first transceiver may be coupled to the first feed using a first circuit. A second transceiver may be coupled to the second feed using a second circuit. The first and second feeds may be isolated from each other using the first and second circuits. The second circuit may have a notch filter that isolates the second feed from the first feed at operating frequencies associated with the first transceiver. The first circuit may include an adjustable component such as an adjustable capacitor. The adjustable component may be placed in different states depending on the mode of operation of the second transceiver to ensure that the first feed is isolated from the second feed. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of an illustrative antenna having multiple feeds in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of an illustrative planar inverted-F antenna with multiple feeds in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram of an illustrative slot antenna with multiple feeds in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of an illustrative inverted-F antenna with multiple feeds in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram of an illustrative loop antenna with multiple feeds in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram of an inverted-F antenna with multiple feeds showing how radio-frequency transceiver circuitry may be coupled to the feeds using transmission lines in accordance with an embodiment of the present invention. 
         FIG. 9  is a diagram of illustrative antenna structures with adjustable filter and matching circuitry in accordance with an embodiment of the present invention. 
         FIG. 10  is a diagram of an illustrative adjustable filter circuit having adjustable bandwidth and frequency tuning features in accordance with an embodiment of the present invention. 
         FIG. 11  is a graph of filter transmission as a function of operating frequency for an illustrative filter circuit of the type shown in  FIG. 10  in accordance with an embodiment of the present invention. 
         FIG. 12  is a top view of an illustrative electronic device of the type that may be provided with antenna structures in accordance with an embodiment of the present invention. 
         FIG. 13  is a diagram of illustrative antenna structures in an electronic device of the type shown in  FIG. 12  in accordance with an embodiment of the present invention. 
         FIG. 14  is a diagram of adjustable circuitry of the type that may be coupled to one of the antenna feeds in the antenna structures of  FIG. 13  in accordance with an embodiment of the present invention. 
         FIG. 15  is a diagram of adjustable circuitry of the type that may be coupled to another of the antenna feeds in the antenna structures of  FIG. 13  in accordance with an embodiment of the present invention. 
         FIG. 16  is a table showing how adjustment of the circuitry of  FIG. 15  may influence antenna performance when using a feed associated with the circuitry of  FIG. 14  in accordance with an embodiment of the present invention. 
         FIG. 17  is a state diagram showing different illustrative modes of operation for an electronic device in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. The wireless communications circuitry may include one or more antennas. 
     The antennas can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. The conductive electronic device structures may include conductive housing structures. The housing structures may include a peripheral conductive housing structure that runs around the periphery of an electronic device. The peripheral conductive structure may be formed from a peripheral conductive member that serves as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, and/or may form other housing structures. Gaps in the peripheral conductive member may be associated with the antennas. 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a cellular telephone, or a media player. Device  10  may also be a television, a set-top box, a desktop computer, a computer monitor into which a computer has been integrated, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. Parts of housing  12  may be formed from dielectric or other low-conductivity material. If desired, some or all of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable display pixel structures. A display cover layer formed from clear plastic or glass may cover the surface of display  14 . Buttons such as button  19  may pass through openings in the display cover layer. The cover layer may also have other openings such as an opening for speaker port  26 . 
     Housing  12  may include peripheral structures  16  formed from a peripheral housing member or other structures. As shown in the example of  FIG. 1 , member  16  may have a rectangular ring shape that runs around the periphery of device  10  and display  14 . Member  16  or part of member  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or helps hold display  14  to device  10 ). Member  16  may also, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, etc.). 
     Member  16  may be formed of a conductive material and may therefore sometimes be referred to as a peripheral conductive member or conductive housing structures. Member  16  may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, or more than two separate structures may be used in forming member  16 . 
     It is not necessary for member  16  to have a uniform cross-section. For example, the top portion of member  16  may, if desired, have an inwardly protruding lip that helps hold display  14  in place. If desired, the bottom portion of member  16  may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ) and/or may be formed as an integral portion of a planar rear surface structure. In the example of  FIG. 1 , member  16  has substantially straight vertical sidewalls. This is merely illustrative. The sidewalls of member  16  may be curved or may have any other suitable shape. In some configurations (e.g., when member  16  serves as a bezel for display  14 ), member  16  may run around the lip of housing  12  (i.e., member  16  may cover only the edge of housing  12  that surrounds display  14  and not the rear edge of housing  12  of the sidewalls of housing  12 ). 
     Display  14  may include conductive structures such as an array of capacitive electrodes, conductive lines for addressing pixel elements, driver circuits, etc. Housing  12  may include internal structures such as metal frame members, a planar housing member (sometimes referred to as a midplate) that spans the walls of housing  12  (i.e., a substantially rectangular member that is welded or otherwise connected between opposing sides of member  16 ), printed circuit boards, and other internal conductive structures. These conductive structures may be located in the center of housing  12  under display  14  (as an example). 
     In regions  22  and  20 , openings may be formed within the conductive structures of device  10  (e.g., between peripheral conductive structure  16  and opposing conductive structures such as conductive housing structures, a conductive ground plane associated with a printed circuit board, and conductive electrical components in device  10 ). These openings may be filled with air, plastic, and other dielectrics. Conductive housing structures and other conductive structures in device  10  may serve as a ground plane for the antennas in device  10 . The openings in regions  20  and  22  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, or may otherwise serve as part of antenna structures formed in regions  20  and  22 . 
     In general, device  10  may include any suitable number of antennas (e.g., one or more, two or more, three or more, four or more, etc.). The antennas in device  10  may be located at opposing first and second ends of an elongated device housing, along one or more edges of a device housing, in the center of a device housing, in other suitable locations, or in one or more of such locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral conductive housing structures  16  may be provided with gap structures. For example, structures  16  may be provided with one or more gaps such as gaps  18 , as shown in  FIG. 1 . The gaps may be filled with dielectric such as polymer, ceramic, glass, air, other dielectric materials, or combinations of these materials. Gaps  18  may divide structures  16  into one or more peripheral conductive structure (member) segments. There may be, for example, two segments of structures  16  (e.g., in an arrangement with two gaps), three segments of structures  16  (e.g., in an arrangement with three gaps), four segments of structures  16  (e.g., in an arrangement with four gaps, etc.). The segments of peripheral conductive structures  16  that are formed in this way may form parts of antennas in device  10 . 
     Device  10  may have upper and lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, etc. 
     A schematic diagram of an illustrative configuration that may be used for electronic device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , electronic device  10  may include storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, etc. 
     Circuitry  28  may be configured to implement control algorithms that control the use of antennas in device  10 . For example, circuitry  28  may perform signal quality monitoring operations, sensor monitoring operations, and other data gathering operations and may, in response to the gathered data and information on which communications bands are to be used in device  10 , control which antenna structures within device  10  are being used to receive and process data and/or may adjust one or more switches, tunable elements, adjustable circuitry in filter and impedance matching circuitry, or other adjustable circuits in device  10  to adjust antenna performance. As an example, circuitry  28  may control which of two or more antennas is being used to receive incoming radio-frequency signals, may control which of two or more antennas is being used to transmit radio-frequency signals, may control the process of routing incoming data streams over two or more antennas in device  10  in parallel, may tune an antenna to cover a desired communications band, may configure filter and matching circuitry to isolate a first antenna feed from a second antenna feed, etc. In performing these control operations, circuitry  28  may open and close switches, may turn on and off receivers and transmitters, may adjust impedance matching circuits, may configure switches in front-end-module (FEM) radio-frequency circuits that are interposed between radio-frequency transceiver circuitry and antenna structures (e.g., filtering and switching circuits used for impedance matching and signal routing), may adjust switches, tunable circuits, and other adjustable circuit elements that are formed as part of an antenna or that are coupled to an antenna or a signal path associated with an antenna, and may otherwise control and adjust the components of device  10 . 
     Input-output circuitry  30  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output circuitry  30  may include input-output devices  32 . Input-output devices  32  may include touch screens, buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  32  and may receive status information and other output from device  10  using the output resources of input-output devices  32 . 
     Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  34  may include satellite navigation system receiver circuitry such as Global Positioning System (GPS) receiver circuitry  35  (e.g., for receiving satellite positioning signals at 1575 MHz) or satellite navigation system receiver circuitry associated with other satellite navigation systems. Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in cellular telephone bands such as bands in frequency ranges of about 700 MHz to about 2700 MHz or bands at higher or lower frequencies. Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include wireless circuitry for receiving radio and television signals, paging circuits, etc. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  34  may include one or more antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structure, patch antenna structures, inverted-F antenna structures, closed and open slot antenna structures, planar inverted-F antenna structures, helical antenna structures, strip antennas, monopoles, dipoles, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link. 
     If desired, one or more of antennas  40  may be provided with multiple antenna feeds and/or adjustable components. Antennas such as these may be used to cover desired communications bands of interest. For example, a first antenna feed may be associated with a first set of communications frequencies and a second antenna feed may be associated with a second set of communications frequencies. The use of multiple feeds (and/or adjustable antenna components) may make it possible to reduce antenna size (volume) within device  10  while satisfactorily covering desired communications bands. 
     An illustrative configuration for an antenna with multiple feeds of the type that may be used in implementing one or more antennas for device  10  is shown in  FIG. 3 . As shown in  FIG. 3 , antenna  40  may have conductive antenna structures such as antenna resonating element  50  and antenna ground  52 . The conductive structures that form antenna resonating element  50  and antenna ground  52  may be formed from parts of conductive housing structures, from parts of electrical device components in device  10 , from printed circuit board traces, from strips of conductor such as strips of wire and metal foil, or other conductive materials. 
     Each antenna feed associated with antenna  40  may, if desired, have a distinct location. As shown in  FIG. 3 , antenna  40  may have a first feed such as feed FA at a first location in antenna  40 , a second feed such as feed FB at a second location in antenna  40 , and one or more additional antenna feeds at potentially different respective locations of antenna  40 . 
     Each feed may be coupled to an associated set of conductive signal paths using terminals such as positive antenna feed terminals (+) and ground antenna feed terminals (−). For example, path  54 A may have a positive conductor  58 A that is coupled to a positive antenna feed terminal in feed FA and a ground conductor  56 A that is coupled to a ground antenna feed terminal in feed FA, whereas path  54 B may have a positive conductor  58 B that is coupled to a positive antenna feed terminal in feed FB and a ground conductor  56 B that is coupled to a ground antenna feed terminal in feed FB. Paths such as paths  54 A and  54 B may be implemented using transmission line structures such as coaxial cables, microstrip transmission lines (e.g., microstrip transmission lines on printed circuits), stripline transmission lines (e.g., stripline transmission lines on printed circuits), or other transmission lines or signal paths. Circuits such as impedance matching and filter circuits and other circuitry may be interposed within paths  54 A and  54 B. 
     The conductive structures that form antenna resonating element  50  and antenna ground  52  may be used to form any suitable type of antenna. 
     In the example of  FIG. 4 , antenna  40  has been implemented using a planar inverted-F configuration having a first antenna feed (feed FA) and a second antenna feed (feed FB). 
       FIG. 5  is a top view of an illustrative slot antenna configuration that may be used for antenna  40 . In the  FIG. 5  example, antenna resonating element  50  is formed from a closed (enclosed) rectangular slot (e.g., a dielectric-filled opening) in ground plane  52 . Feeds FA and FB may each have a respective pair of antenna feed terminals (+/−) located at a respective position along the antenna slot. 
     In the illustrative configuration of  FIG. 6 , antenna  40  has been implemented using an inverted-F antenna design. Inverted-F antenna  40  of  FIG. 6  has a first antenna feed (feed FA with a corresponding positive terminal and ground terminal) and has a second antenna feed (feed FB with a corresponding positive terminal and ground terminal). Feeds FA and FB may be located at different respective locations along the length of the main resonating element arm that forms inverted-F antenna  40 . Inverted-F configurations for antenna  40  with multiple branches such as an inverted-F antenna having short (high band) and long (low band) portions of a shared main resonating element arm or arms of different shapes may be used, if desired. 
       FIG. 7  is a diagram showing how antenna  40  may be implemented using a loop antenna configuration with multiple antenna feeds. As shown in  FIG. 7 , antenna  40  may have a loop of conductive material such as loop  60 . Loop  60  may be formed from conductive structures  50  and/or conductive structures  52  ( FIG. 3 ). A first antenna feed such as feed FA may have a positive antenna feed terminal (+) and a ground antenna feed terminal (−) and may be used to feed one portion of loop  60  and a second antenna feed such as feed FB may have a positive antenna feed terminal (+) and a ground antenna feed terminal (−) and may be used to feed antenna  40  at a different portion of loop  60 . 
     The illustrative examples of  FIGS. 4 ,  5 ,  6 , and  7  are merely illustrative. Antenna  40  may, in general, have any suitable number of antenna feeds and may be formed using any suitable type of antenna structures. 
       FIG. 8  shows how antenna  40  may be coupled to transceiver circuitry  62 . Antenna  40  of  FIG. 8  is an inverted-F antenna, but, in general, any suitable type of antenna may be used in implementing antenna  40 . Antenna  40  may have multiple feeds such as illustrative first antenna feed FA with a positive antenna feed terminal (+) and a ground antenna feed terminal (−) and illustrative second antenna feed FB with a positive antenna feed terminal (+) and ground antenna feed terminal (−). Path  54 A may include one or more transmission line segments and may include positive conductor  56 A and ground conductor  58 A. Path  54 B may include one or more transmission line segments and may include positive conductor  56 B and ground conductor  58 B. One or more circuits such as filter circuits and impedance matching circuits and other circuits (not shown in  FIG. 8 ) may be interposed within paths  54 A and  54 B. Transceiver circuitry  62  may include radio-frequency receivers and/or radio-frequency transmitters such as transceivers  62 A and  62 B. 
     Path  54 A may be coupled between a first radio-frequency transceiver circuit such as transceiver  62 A and first antenna feed FA. Path  54 B may be used to couple a second radio-frequency transceiver circuit such as transceiver  62 B to second antenna feed FB. Feeds FA and FB may be used in transmitting and/or receiving radio-frequency antenna signals. Transceiver  62 A may include a radio-frequency receiver and/or a radio-frequency transmitter. Transceiver  62 B may also include a radio-frequency receiver and/or a radio-frequency transmitter. 
     As an example, transceiver  62 A may include a satellite navigation system receiver and transceiver  62 B may include a cellular telephone transceiver (having a cellular telephone transmitter and a cellular telephone receiver). As another example, transceiver  62 A may have a transmitter and/or a receiver that operate at frequencies associated with a first communications band (e.g., a first cellular or wireless local area network band) and transceiver  62 B may have a transmitter and/or a receiver that operate at frequencies associated with a second communications band (e.g., a second cellular or wireless local area network band). Other types of configurations may be used, if desired. Transceivers  62 A and  62 B may be implemented using separate integrated circuits or may be integrated into a common integrated circuit (as examples). One or more associated additional integrated circuits (e.g., one or more baseband processor integrated circuits) may be used to provide transceiver circuitry  62  with data to be transmitted by antenna  40  and may be used to receive and process data that has been received by antenna  40 . Baseband processors and other control circuitry  28  may also be used in controlling settings for antenna  40  during wireless operation of device  10 . 
     Filter circuitry and impedance matching circuitry may be interposed in paths such as paths  54 A and  54 B. As shown in  FIG. 9 , for example, filter and impedance matching circuitry  64 A may be interposed in path  54 A between feed FA and transceiver  62 A, so that signals that are transmitted and/or received using antenna feed FA are filtered by filter and impedance matching circuitry  64 A. Filter and impedance matching circuitry  64 B may likewise be interposed in path  54 B, so that signals that are transmitted and/or received using antenna feed FB are filtered by filter and impedance matching circuitry  64 B. Filter and matching circuitry  64 A and  64 B may include fixed and/or adjustable circuitry. In adjustable filter and matching circuit configurations, adjustable components may be placed in different states to adjust the signal transmittance and impedance characteristics of the circuits. 
     Circuits  64 A and  64 B may be configured so that the antenna feeds in antenna  40  operate satisfactorily, even in a configuration in which multiple feeds are coupled to antenna  40  simultaneously. Adjustable filter and matching circuitry  64 A and/or  64 B may, for example, be adjusted in real time by control circuitry  28  to optimize performance. 
     The adjustable filter and matching circuitry in device  10  may include circuitry that is adjusted to tune the frequency response of a filter and/or that is adjusted to tune the bandwidth of a filter. Consider, as an example, filter circuitry  98  of  FIG. 10 . Filter circuitry  98  of  FIG. 10  may have two filters FW and FN coupled in series between terminals  96  and  94 . Filter FW may include inductor  100  and parallel capacitor  104 . Filter FN may include inductor  106  and parallel capacitor  108 . Capacitors  104  and  108  may be adjusted to exhibit desired amounts of capacitance (e.g., to tune filter  98 ). Capacitance adjustments may be made in response to control signals from control circuitry  28  (e.g., a baseband processor or other controller). 
     Filters FW and FN may be band stop filters characterized by bandwidths BW and BN, respectively. Bandwidth BW may be larger than BN. As an example, bandwidth BW may be 400 MHz and BN may be 50 MHz. When it is desired to configure filter  98  to exhibit a large bandwidth (i.e., bandwidth BW), control circuitry  28  may open switch  102 , thereby switching filter FW into use. When it is desired to configure filter  98  to exhibit a narrow bandwidth (i.e., bandwidth BN), control circuitry  28  may close switch  102 , thereby bypassing band stop filter FW. 
       FIG. 11  is a graph in which filter transmission T has been plotted as a function of operating frequency f for the illustrative filter circuitry of  FIG. 10 . As shown in  FIG. 11 , filter FN may be characterized by a narrower bandwidth than filter FW. When switch  102  is closed, filter FW will be bypassed and filter  98  will be characterized by a transmission T of the type shown by line  110 . Adjustments  112  to the position of the stop band associated with curve  110  may be made by adjusting capacitor  108 . When switch  102  is open, filter FW will be switched into use and filter  98  will be characterized by a transmission T of the type shown by line  114  of  FIG. 11 . Adjustments  116  to the position of the stop band associated with curve  114  may be made by adjusting capacitor  104 . 
     The adjustable filter circuitry of  FIG. 10  is merely illustrative. Adjustable tuning and matching circuitry for antenna structures  40  in device  10  may include band stop filters (e.g., band stop filters with fixed or adjustable bandwidths) that are coupled in series and/or parallel, band pass filters, notch filters, low pass filters, high pass filters, or other filters. 
     One or more antennas  40  in device  10  may be provided with filter and matching circuitry such as circuitry  64 A and  64 B. Antenna(s)  40  may be formed from conductive structures in device  10  such as portions of a peripheral conductive housing structure, other conductive housing structures, and other conductive structures in device  10 .  FIG. 12  is a top interior view of device  10  in a configuration in which device  10  has a peripheral conductive housing structure such as housing structure  16  of  FIG. 1  with one or more gaps  18 . As shown in  FIG. 12 , device  10  may have an antenna ground plane such as antenna ground plane  52 . Ground plane  52  may be formed from traces on printed circuit boards (e.g., rigid printed circuit boards and flexible printed circuit boards), from conductive planar support structures in the interior of device  10 , from conductive structures that form exterior parts of housing  12 , from conductive structures that are part of one or more electrical components in device  10  (e.g., parts of connectors, switches, cameras, speakers, microphones, displays, buttons, etc.), or other conductive device structures. Gaps such as gaps  82  may be filled with air, plastic, or other dielectric. 
     One or more segments of peripheral conductive member  16  may serve as antenna resonating elements such as antenna resonating element  50  of  FIG. 3 . For example, the uppermost segment of peripheral conductive member  16  in region  22  may serve as an antenna resonating element for an antenna  40  in device  10 . The conductive materials of peripheral conductive member  16 , the conductive materials of ground plane  52 , and dielectric openings  82  (and gaps  18 ) may be used in forming one or more antennas in device  10  such as an upper antenna in region  22  and a lower antenna in region  20 . Configurations in which an antenna in upper region  22  is implemented using a dual feed arrangement of the type described in connection with  FIG. 14  are sometimes described herein as an example. 
     As shown in  FIG. 13 , antenna  40  may be a dual-arm inverted-F antenna (sometimes referred to as a T antenna). Resonating element  50  may have a main resonating element arm portion that is formed from a segment of peripheral conductive housing structure such as member  16  that extends between respective gaps  18  at one end of device  10  (e.g., the upper or lower end of device  10 ). Resonating element  50  may have first and second branches (e.g., a longer branch for handling lower frequencies and a shorter branch for handling higher frequencies). Other resonating element arm shapes may be used if desired. The use of a dual branch (dual arm) structure for antenna resonating element  50  is merely illustrative. 
     Return path  84  (sometimes referred to as a short circuit path) may be coupled between the main resonating element arm formed from segment  16  and antenna ground  52  across opening  82 . Feeds FA and FB may span opening  82  in parallel with return path  84 . 
     Antenna  40  may have adjustable filter and matching circuitry  64 A and adjustable filter and matching circuitry  64 B. Adjustable filter and matching circuitry  64 A may be coupled to feed FA in path  54 A. Adjustable filter and matching circuitry  64 B may be coupled to feed FB in path  54 B. Circuitry  64 A and  64 B may include antenna tuning circuitry. For example, circuitry  64 B may include circuitry for tuning antenna performance in a cellular telephone band such as a cellular telephone band extending from 700 to 960 MHz. Circuitry  64 A and  64 B may also be adjusted to allow efficient operation of antenna  40  in desired bands of interest while blocking undesired coupling between feeds (ports) FA and FB. 
     To ensure that antenna  40  can operate efficiently when feed FB is active, it may be desirable to ensure that circuitry  64 B is configured to impedance match path  54 B to antenna  40 . This helps prevent undesired signal reflections at the operating frequency associated with feed FB, so that signals can be efficiently transmitted and received through feed FB. At the same time, it may be desirable to ensure that circuitry  64 A is configured to isolate antenna feed FA from antenna  40  at the operating frequency associated with feed FB. Circuitry  64 A may, for example, be configured to create an open circuit or closed circuit at feed FA for signals at the current operating frequency associated with feed FB. By tuning circuitry  64 A, adequate isolation of feed FA from feed FB at the current operating frequency associated with feed FB may be assured, even when antenna  40  in device  10  has been configured to be capable of operating over a wide range of communications bands. Although circuitry  64 A will exhibit an impedance mismatch with antenna  40  at the operating frequency associated with feed FB to isolate feeds FB and FA from each other, circuitry  64 A will preferably impedance match feed FA to antenna  40  at the operating frequency associated with feed FA. This allows antenna  40  to simultaneously use feed FB for handling signals at one frequency and feed FA for handling signals at another frequency. 
     Illustrative adjustable filter and matching circuitry that may be used to implement adjustable filter and matching circuitry  64 B for coupling transceiver circuitry  62  to antenna  40  is shown in  FIG. 14 . Circuitry  64 B may be coupled to feed FB of antenna  40  (e.g., antenna  40  of  FIG. 13  or other suitable antenna  40 ). Baseband processor  132  may provide data to transceiver  38  for transmission over antenna  40  and may receive data from transceiver  38  that has been received over antenna  40 . Baseband processor  132  (or other control circuitry  28 ) may also issue control signals to adjustable circuitry in circuitry  64 B over paths such as path  128  (e.g., using digital signaling protocols such as serial bus protocols). 
     Switch  130  may be configured to couple transceiver  62 B to antenna  40 ′ when antenna  40  is not being used (e.g., because antenna  40  is impaired or because antenna  40 ′ is otherwise favored over antenna  40 ). Switch  130  may be configured to couple transceiver  62 B to antenna  40  via circuitry  64 B when antenna  40  is being used. Baseband processor  132  or other control circuitry in device  10  may be use to control the state of switch  130 . 
     Transceiver  62 B may be a cellular telephone transceiver (e.g., transceiver  38  of  FIG. 2 ) that is configured to operate in a low band at 700-960 MHz, a middle band at 1700-2170 MHz, and a high band at 2300-2700 MHz (as an example). Transceiver  62 A may be a satellite navigation system receiver such as a Global Positioning System (GPS) receiver operating at a frequency such as 1575 MHz (see, e.g., satellite navigation system receiver  35  of  FIG. 2 ). 
     Adjustable circuitry  64 B may include a notch filter such as notch filter  120 . Notch filter  120  may exhibit a low transmittance (i.e., a notch) at 1575 MHz. This low transmittance is associated with an impedance mismatch between antenna  40  and feed FB at 1575 MHz and isolates feed FB from antenna  40  and feed FA at 1575 MHz. By isolating feed FB from antenna  40  at 1575 MHz, the presence of feed FB will not adversely affect the performance of antenna  40  and feed FA in receiving satellite navigation system signals at 1575 MHz. 
     At frequencies other than the notch frequency (i.e., at frequencies other than 1575 MHz such as the low, middle, and high cellular telephone bands), notch filter  120  may exhibit a high transmission, thereby allowing transceiver  62 B and antenna  40  to be used in transmitting and/or receiving signals. 
     If desired, circuitry  64 B may include antenna tuning circuitry  122 . Tuning circuitry  122  may be adjusted in real time based on control signals from baseband processor  132  on path  128  to tune the frequency response of antenna  40  in the low, middle, or high band of antenna  40  that is being used by feed FB. In the example of  FIG. 14 , tuning circuitry  122  includes adjustable capacitor  124 . Adjustable capacitor  124  includes switching circuitry  134  for selectively switching capacitors  126  into use. Adjustable capacitor  124  can switch a selected set of one or more capacitors  124  into use or can switch a short circuit into use, thereby adjusting the capacitance interposed between switch  130  and notch filter  120 . The capacitance value used for capacitor  124  may tune the frequency response for antenna  40  when using feed FB. For example, adjustment of the capacitance exhibited by capacitor  124  may tune a low band resonant peak for antenna  40  between one of several different possible resonant peak locations within the low cellular telephone band (e.g., two, three, or four or more peak positions within the band from 700 to 960 MHz). Middle and high band performance may not be significantly affected by adjustments to capacitor  124 . Other types of antenna tuning may be implemented using tunable circuitry such as tuning circuit  122 . The illustrative configuration of  FIG. 14  is merely an example. 
     To ensure that antenna performance for antenna  40  when using feed FB is not degraded by the presence of undesired coupling into feed FA, adjustable filter  64 A for feed FA may be configured to exhibit an impedance mismatch with antenna  40  (e.g., an open circuit or short circuit) at the operating frequency associated with the low, middle, or high cellular telephone band being handled by feed FB. The impedance mismatch between circuitry  64 A and antenna  40  at the operating frequencies for feed FB will ensure that feed FA is isolated from feed FB at the operating frequencies associated with feed FB, so that the presence of feed FA will not adversely influence the performance of antenna  40  at the operating frequencies associated with feed FB. 
     It can be challenging to configure circuitry  64 A to isolate feed FA from feed FB, particularly when feed FB is capable of being used over a wide range of operating frequencies. Accordingly, circuitry  64 A may be provided with tunable circuitry. The tunable circuitry allows circuitry  64 A to be adjusted to form a satisfactory impedance mismatch with antenna  40  for each potential operating frequency of feed FB. If, for example, feed FB is capable of handling cellular telephone signals in the low, middle, and high cellular telephone bands, circuitry  64 A can be placed in a first configuration whenever feed FB is being operated in the low band, a second configuration whenever feed FB is being operated in the middle band, and a third configuration whenever feed FB is being operated in the high band. 
     Adjustable circuitry  64 A may include adjustable inductors, adjustable capacitors, and other adjustable circuitry. In the example of  FIG. 15 , adjustable circuitry  64 A is a band stop filter having an inductor such as inductor  136  coupled in parallel with adjustable capacitor  138  between feed FA and transceiver circuitry (e.g., satellite navigation system transceiver circuitry)  62 A. Adjustable capacitor  138  may have switching circuitry  140  that is controlled by control signals from baseband processor  132  that are received on control path  128 ′. Adjustable capacitor  138  may also have capacitors  142 . Capacitors  142  may have different values. Switching circuitry  140  can switch one or more selected capacitors  142  into use or can switch a short circuit into use to create a desired amount of capacitance between feed FA and transceiver circuitry  62 A in parallel with inductor  136 . Different capacitor settings may be used whenever it is desired to optimize the configuration of circuitry  64 A to ensure adequate isolation between feeds FA and FB at the current operating frequency of feed FB. 
       FIG. 16  is a table showing how the amount of isolation between feeds FA and FB can be influenced by the operating frequency of the signals associated with feed FB and the setting of circuitry  64 A. In the example of  FIG. 16 , device  10  is using transceiver  62 B to handle three different communications bands—a first (low) cellular telephone band extending from 700 to 960 MHz, a second (middle) cellular telephone band extending from 1710 to 2170 MHz, and a third (high) cellular telephone band extending from 2300 to 2700 MHz. There are three different possible capacitance settings for circuitry  64 A (which is located on the other feed-feed FA). As shown in the first row of the table of  FIG. 16 , when using feed FB to handle low band signals, optimum isolation of feed FA from feed FB and therefore optimum performance of antenna  40  for the low band signals passing through feed FB can be achieved when setting capacitor  138  of circuitry  64 A to a capacitance value of C 1 , whereas less than optimum isolation between feeds FA and FB and less than optimum performance of antenna  40  is achieved when using capacitance values C 2  and C 3 . The entries of the second row of the table of  FIG. 16  show that capacitor  138  should be set to capacitor value C 2  to achieve optimum performance when operating feed FB in the middle band. High band performance can be optimized for feed FB by setting capacitor  138  to a third value of capacitance C 3 , as shown by the entries in the third row of the table of  FIG. 16 . Capacitance values C 1 , C 2 , and C 3  are typically different from each other. When C 1  is switched into use, the stop band of circuitry  64 A may be aligned with the low band, when C 2  is switched into use, the stop band of circuitry  64 A may be aligned with the middle band, and when C 3  is switched into use, the stop band of circuitry  64 A may be aligned with the high band. 
       FIG. 17  is a diagram of illustrative modes of operation that may be used for wireless circuitry  34  in device  10 . During operation of device  10 , control circuitry  28  can adjust circuitry such as circuitry  64 A (and circuitry  64 B) dynamically based on knowledge (e.g., from baseband processor  132 ) of which cellular telephone frequencies are currently being handled by transceiver circuitry  62 B. For example, when device  10  is operating in mode  200  (sometimes referred to as a low band mode), cellular telephone transceiver circuitry  62 B may transmit and receive cellular telephone signals in the range of 700 MHz to 960 MHz while control circuitry  28  places circuit  64 A in a first state (i.e., while control circuitry  28  configures capacitor  138  in circuitry  64 A to exhibit a capacitance value of C 1 ). The C 1  capacitance value will align the stop band of circuitry  64 A with the low band from 700 MHz to 960 MHz and will thereby ensure that feed FA is isolated from feed FB in the low band. During low band operations, circuit  64 B may be adjusted to tune the antenna resonance of antenna  40  in the low band. 
     When device  10  is operating in mode  202  (sometimes referred to as a middle band mode), cellular telephone transceiver circuitry  62 B may transmit and receive signals in the range of 1710 MHz to 2170 MHz while control circuitry  28  places circuitry  64 A in a second state (i.e., while capacitor  138  in circuitry  64 A is set to exhibit a capacitance value of C 2 ). The value of C 2  will ensure that feeds FA and FB are isolated in the middle band so that antenna  40  can perform efficiently in the middle band when using feed FB. 
     xx Mode  204  (sometimes referred to as a high band cellular telephone mode) may involve transmitting and receiving high band cellular telephone signals with feed FB (i.e., signals in a frequency range of 2300 MHz to 2700 MHz). In this mode control circuitry  28  may adjust circuitry  64 A to place circuitry  64 A in a third mode (i.e., a mode in which capacitor  138  is set to C 3  to ensure satisfactory isolation between feeds FA and feed FB and satisfactory performance (antenna efficiency) for antenna  40  when using feed FB. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20130506
Publication Date: 20151020
Grant Date: 20151020
Priority Date: 20130506
Inventors: DARNELL DEAN F.
VAZQUEZ ENRIQUE AYALA
HU HONGFEI
OUYANG YUEHUI
PASCOLINI MATTIA
SCHLUB ROBERT W.
BEVELACQUA PETER
XU HAO
NATH JAYESH
ZHOU YIJUN
JIN NANBO
PRATT DAVID
MOW MATTHEW A.
TSAI MING-JU
HAN LIANG
BIEDKA THOMAS E.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 51841680