PATENT DOCUMENT

Publication Number: US-9276319-B2
Application Number: US-201313889987-A
Country: US
Kind Code: B2

Title: Electronic device antenna with multiple feeds for covering three communications bands

Abstract:
Electronic devices may be provided that include radio-frequency transceiver circuitry and antennas. An antenna may be formed from an antenna resonating element and an antenna ground. The antenna resonating element may have a shorter portion that resonates at higher communications band frequencies and a longer portion that resonates at lower communications band frequencies. An extended portion of the antenna ground may form an inverted-F antenna resonating element portion of the antenna resonating element. The antenna resonating element may be formed from a peripheral conductive electronic device housing structure that is separated from the antenna ground by an opening. A first antenna feed may be coupled between the peripheral conductive electronic device housing structures and the antenna ground across the opening. A second antenna feed may be coupled to the inverted-F antenna resonating element portion of the antenna resonating element.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 control circuitry; and 
 an antenna that is tuned by the control circuitry, wherein the antenna has an inverted-F antenna resonating element and an antenna ground that are separated by a gap, wherein the antenna has a first antenna feed coupled across the gap, wherein the inverted-F antenna resonating element has conductive structures configured to form an additional inverted-F antenna resonating element portion of the inverted-F antenna resonating element, wherein the additional inverted-F antenna resonating element portion has a resonating element arm formed from the conductive structures that is separated from the antenna ground by an opening and has a return path formed from a portion of the conductive structures, and wherein the antenna has a second antenna feed coupled across the opening. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the antenna is configured to resonate in at least a first communications band, a second communications band that is higher in frequency than the first communications band, and a third communications band that is higher in frequency than the first communications band. 
     
     
       3. The electronic device defined in  claim 1  wherein the antenna includes an adjustable inductor that bridges the gap and that is controlled by the control circuitry to tune the antenna. 
     
     
       4. The electronic device defined in  claim 1  wherein the inverted-F antenna resonating element has at least first and second arms, wherein the first arm is longer than the second arm, wherein the first arm is configured to resonate in at least a first communications band, and wherein the second arm is configured to resonate in at least a second communications band that is higher in frequency than the first communications band. 
     
     
       5. The electronic device defined in  claim 4  wherein the additional inverted-F antenna resonating element portion of the inverted-F antenna resonating element is configured to resonate in at least a third communications band that is higher in frequency than the second communications band. 
     
     
       6. The electronic device defined in  claim 5  wherein the first arm includes first and second branches that resonate in the first communications band. 
     
     
       7. The electronic device defined in  claim 6  wherein the first and second branches are configured to produce first and second antenna resonances at different respective frequencies in the first communications band and wherein the antenna includes an adjustable inductor that bridges the gap and that is controlled by the control circuitry to tune the first and second antenna resonances in the first communications band. 
     
     
       8. The electronic device defined in  claim 1  further comprising an adjustable electrical component that is coupled in parallel with the first antenna feed across the gap. 
     
     
       9. The electronic device defined in  claim 8  further comprising a short circuit path formed from a portion of the conductive structures, wherein the short circuit path is coupled between the inverted-F antenna resonating element and the antenna ground in parallel with the first antenna feed. 
     
     
       10. The electronic device defined in  claim 9  wherein the first antenna feed is between the adjustable electrical component and the short circuit path. 
     
     
       11. The electronic device defined in  claim 1  further comprising a peripheral conductive housing member, wherein the inverted-F antenna resonating element comprises a portion of the peripheral conductive housing member. 
     
     
       12. An electronic device, comprising:
 control circuitry; and 
 an antenna that is tuned by the control circuitry, wherein the antenna has an antenna resonating element and an antenna ground configured to resonate in at least a first communications band, a second communications band that is at a higher frequency than the first communications band, and a third communications band that is higher in frequency than the second communications band, and wherein the antenna resonating element has a first arm that is separated from the antenna ground by an opening and is configured to resonate in the first communications band and a second arm that is separated from the antenna ground by the opening and that is configured to resonate in the second communications band and conductive structures that are configured to resonate in the third communications band. 
 
     
     
       13. The electronic device defined in  claim 12  wherein the antenna comprises a tunable component coupled between the antenna resonating element and the antenna ground and wherein the control circuitry tunes that antenna by controlling the tunable component. 
     
     
       14. The electronic device defined in  claim 13  wherein the tunable component includes switching circuitry and an inductor. 
     
     
       15. The electronic device defined in  claim 14  wherein the conductive structures comprise an extended portion of the antenna ground, wherein a portion of the extended portion of the antenna ground is separated from the antenna ground by a gap, wherein the antenna has a first feed coupled between the antenna resonating element and the antenna ground across the opening, and wherein the antenna has a second antenna feed that is coupled across the gap. 
     
     
       16. The electronic device defined in  claim 15  wherein the portion of the extended portion of the antenna ground forms an inverted-F arm that is coupled to a positive antenna feed terminal in the second antenna feed. 
     
     
       17. The electronic device defined in  claim 16  further comprising:
 a ground antenna feed terminal in the second antenna feed that is coupled to the antenna ground; and 
 additional conductive structures in the antenna, wherein the first arm comprises a portion of a peripheral conductive housing member, wherein the portion of the peripheral conductive housing member forms a first branch of the first arm and wherein the additional conductive structures form a second branch of the first arm. 
 
     
     
       18. An antenna, comprising:
 a portion of a peripheral conductive electronic device housing structure; and 
 an antenna ground that is separated from the portion of the peripheral conductive electronic device housing structure by an opening; 
 a first antenna feed that bridges the opening; and 
 a second antenna feed coupled to an extended portion of the antenna ground, wherein the extended portion of the antenna ground forms an inverted-F antenna resonating element. 
 
     
     
       19. The antenna defined in  claim 18  wherein a portion of the extended portion of the antenna ground forms a short circuit path between the portion of the peripheral conductive electronic device housing structure and the antenna ground, wherein the portion of the peripheral conductive electronic device housing structure and the antenna ground are configured to resonant in first and second communications bands using at least the first antenna feed, wherein the inverted-F antenna resonating element is configured to resonate in a third communications band using the second antenna feed, and wherein the second communications band is at frequencies between the first communications band and the third communications band. 
     
     
       20. The antenna defined in  claim 19  wherein the portion of the peripheral conductive electronic device housing structure forms a first branch of an inverted-F antenna resonating element arm that resonates in the first communications band and wherein the antenna further comprises a second branch of the inverted-F antenna resonating element arm.

Description:
BACKGROUND 
     This relates generally to electronic devices, and more particularly, to antennas 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 structures 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 wireless communications circuitry for wireless electronic devices. 
     SUMMARY 
     Electronic devices may be provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antennas. An antenna may be formed from an antenna resonating element and an antenna ground. 
     The antenna resonating element may have a longer portion that resonates at first communications band frequencies and a shorter portion that resonates at second communications band frequencies above the first communications band frequencies. The resonating element may be formed from peripheral conductive electronic device housing structures that are separated from the antenna ground by an opening. 
     An extended portion of the antenna ground may form an inverted-F antenna resonating element portion of the antenna resonating element that resonates at third communications band frequencies above the first and second communications band frequencies. 
     A first antenna feed may be coupled between the peripheral conductive electronic device housing structures and the antenna ground across the opening. A second antenna feed may be coupled to the inverted-F antenna resonating element portion of the antenna resonating element. 
     An adjustable component such as a tunable inductor may be coupled between the antenna resonating element and antenna ground for tuning the antenna. The shorter portion of the antenna resonating element may be formed from a portion of the peripheral conductive electronic device housing structures and may serve as a first branch of an inverted-F antenna resonating element arm. The inverted-F antenna resonating element arm may also have a second branch. The first and second branches may be characterized by respective first and second antenna resonance peaks within the first communications band. 
     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 top view of an illustrative electronic device of the type shown in  FIG. 1  in which antennas may be formed using conductive housing structures such as portions of a peripheral conductive housing member in accordance with an embodiment of the present invention. 
         FIG. 4  is a circuit diagram showing how an antenna in the electronic device of  FIG. 1  may be coupled to radio-frequency transceiver circuitry in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram of an illustrative adjustable inductor based on a single fixed inductor that may be used in a tunable antenna in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of an illustrative adjustable inductor based on multiple fixed inductors that may be used in a tunable antenna in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram of an illustrative antenna with multiple feeds for covering multiple communications bands in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 8  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency when using a first feed of an antenna of the type shown in  FIG. 7  in accordance with an embodiment of the present invention. 
         FIG. 9  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency when using a second feed of an antenna of the type shown in  FIG. 7  in accordance with an embodiment of the present invention. 
         FIG. 10  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency when using both first and second feeds in an antenna of the type shown in  FIG. 7  in accordance with an embodiment of the present invention. 
         FIG. 11  is a diagram of an illustrative antenna with multiple feeds and multiple low band antenna resonating element branches for covering multiple communications bands in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 12  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency when using a first feed of an antenna of the type shown in  FIG. 11  in accordance with an embodiment of the present invention. 
         FIG. 13  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency when using a second feed of an antenna of the type shown in  FIG. 11  in accordance with an embodiment of the present invention. 
         FIG. 14  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency when using both first and second feeds in an antenna of the type shown in  FIG. 11  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 member that runs around the periphery of an electronic device. The peripheral conductive member may serve 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. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable image pixel structures. A display cover layer formed from clear glass, transparent plastic, or other transparent dielectric 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 a peripheral member such as member  16 . Member  16  may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape, member  16  may have a rectangular ring shape (as an example). 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 surrounding the periphery of device  10 , etc.). 
     Member  16  may be formed of a conductive material and may therefore sometimes be referred to as a peripheral conductive member, peripheral conductive housing 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 (e.g., segments) 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 ). 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 ). Integral portions of the metal structure that forms member  16  may, if desired, extend across the rear of device  10  (e.g., housing  12  may have a planar rear portion and portions of peripheral conductive member  16  may be formed from sidewall portions of that extend vertically upwards from the planar rear portion). 
     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 member  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 member  16  may be provided with gap structures. For example, member  16  may be provided with one or more gaps (splits) 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 member  16  into one or more peripheral conductive member segments. There may be, for example, two segments of member  16  (e.g., in an arrangement with two gaps), three segments of member  16  (e.g., in an arrangement with three gaps), four segments of member  16  (e.g., in an arrangement with four gaps, etc.). The segments of peripheral conductive member  16  that are formed in this way may form parts of antennas in device  10 . 
     In a typical scenario, 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 control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  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, 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, 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 wireless local area network communications. For example, 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 tunable circuitry. The tunable circuitry may include switching circuitry based on one or more switches. The switching circuitry may, for example, include a switch that can be placed in an open or closed position. When control circuitry  28  of device  10  places the switch in its open position, an antenna may exhibit a first frequency response. When control circuitry  28  of device  10  places the switch in its closed position, the antenna may exhibit a second frequency response. Tunable circuitry for one or more of antennas  40  may also be based on switching circuitry that can switch selected circuit components into use. For example, an adjustable inductor may operate in a first mode in which a first inductor is switched into use and a second mode in which a second inductor is switched into use. An adjustable inductor may optionally also be switched into a mode in which a short circuit is switched into use or in which an open circuit is formed. Using adjustable inductors such as these or other adjustable circuit components, the performance of antenna  40  may be adjusted in real time to cover operating frequencies of interest. 
     Antenna  40  may exhibit multiple resonances. For example, antenna  40  may be configured to exhibit resonances in a low band, a middle band, and a high band (as examples). Low band communications frequencies may include communications frequencies from 700 MHz to 960 MHz, middle band communications frequencies may include communications frequencies from 1710 to 2170 MHz, and high band communications frequencies may include communications frequencies from 2300 to 2700 MHz (as examples). Other communications frequencies can be covered using antenna  40 , if desired. Configurations in which antenna  40  covers low, middle, and high communications bands are merely illustrative. 
     Adjustment of the state of adjustable inductors or other adjustable circuit components may be used to tune antenna  40 . For example, adjustments to the state of one or more adjustable inductor circuits may be used to tune the low band response of antenna  40  without appreciably affecting the middle and high band responses. The ability to adjust the response of the antenna may allow the antenna to cover communications frequencies of interest. 
     A top interior view of device  10  in a configuration in which device  10  has a peripheral conductive housing member such as housing member  16  of  FIG. 1  with one or more gaps  18  is shown in  FIG. 3 . As shown in  FIG. 3 , 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 (openings)  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 for an antenna in device  10 . For example, the uppermost segment of peripheral conductive member  16  in region  22  may serve as an antenna resonating element for an upper antenna in device  10  and the lowermost segment of peripheral conductive member  16  in region  20  (i.e., segment  16 ′, which extends between gap  18 A and gap  18 B) may serve as an antenna resonating element for a lower antenna in device  10 . The conductive materials of peripheral conductive member  16 , the conductive materials of ground plane  52 , and dielectric-filled 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 lower region  20  is implemented using a tunable frequency response configuration are sometimes described herein as an example. 
     Illustrative antenna structures of the type that may be used in device  10  (e.g., in region  20  and/or region  22 ) are shown in  FIG. 4 . Antenna structures  40  of  FIG. 4  include an antenna resonating element of the type that is sometimes referred to as a dual arm inverted-F antenna resonating element or T antenna resonating element. As shown in  FIG. 4 , antenna structures  40  may have conductive antenna structures such as dual arm inverted-F 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 may be formed using other conductive structures. 
     As shown in  FIG. 4 , antenna structures  40  may be coupled to wireless circuitry  90  such as transceiver circuitry, filters, switches, duplexers, impedance matching circuitry, and other circuitry using transmission line structures such as transmission line structures  92 . Transmission line structures  92  may include transmission lines such as transmission line  92 - 1  and transmission line  92 - 2 . Transmission line  92 - 1  may have positive signal path  92 - 1 A and ground signal path  92 - 1 B. Transmission line  92 - 2  may have positive signal path  92 - 2 A and ground signal path  92 - 2 B. Paths  92 - 1 A,  92 - 1 B,  92 - 2 A, and  92 - 2 B may be formed from metal traces on rigid printed circuit boards, may be formed from metal traces on flexible printed circuits, may be formed on dielectric support structures such as plastic, glass, and ceramic members, may be formed as part of a cable, or may be formed from other conductive signal lines. Transmission line structures  92  may be formed using one or more microstrip transmission lines, stripline transmission lines, edge coupled microstrip transmission lines, edge coupled stripline transmission lines, coaxial cables, or other suitable transmission line structures. Circuits such as impedance matching circuits, filters, switches, duplexers, diplexers, and other circuitry may, if desired, be interposed in the transmission lines of structures  92 . 
     Transmission line structures  92  may be coupled to antenna feeds formed using antenna feed terminals  94 - 1  and  96 - 1  (which form a first antenna feed F1) and antenna feed terminals  94 - 2  and  96 - 2  (which form a second antenna feed F2). Terminal  94 - 1  may be a positive antenna feed terminal and terminal  96 - 1  may be a ground antenna feed terminal for first antenna feed F1. Terminal  94 - 2  may be a positive antenna feed terminal and terminal  96 - 2  may be a ground antenna feed terminal for second antenna feed F2. 
     The antenna feeds in antenna structures  40  may be used in handling the same types of signals or different types of signals. For example, the first feed may be used for transmitting and/or receiving antenna signals in a first communications band or first set of communications bands and the second feed may be used for transmitting and/or receiving antenna signals in a second communications band or second set of communications bands or the first and second feeds may collectively be used in transmitting signals in multiple communications bands (e.g., in a configuration in which transmission lines  92 - 1  and  92 - 2  are branches of a common transmission line that are coupled together using a splitter). 
     If desired, tunable components such as adjustable capacitors, adjustable inductors, filter circuitry such as band-pass filter circuitry, band-stop filter circuitry, high pass filter circuitry, and low pass filter circuitry, switches, impedance matching circuitry, duplexers, diplexers, splitters, and other circuitry may be interposed within transmission line paths  92  (i.e., between wireless circuitry  90  and the respective feeds of antenna structures  40 ). The different feeds in antenna structures  40  may each exhibit a different impedance and antenna resonance behavior as a function of operating frequency. Wireless circuitry  90  may therefore use different feeds or combinations of feeds for different signal frequencies, if desired. Duplexers or other filter circuitry may route signals to and from the feeds of antenna  40  as a function of frequency. 
     Antenna resonating element  50  may include a short circuit branch such as branch  98  that couples resonating element arm structures such as arms  100  and  102  to antenna ground  52 . Arms such as arms  100  and  102  may be formed from segment  16 ′ of peripheral conductive housing member  16  or other conductive structures in device  10 . Dielectric opening (gap)  82  separates arms  100  and  102  from antenna ground  52 . Antenna ground  52  may be formed from housing structures such as a metal midplate member, printed circuit traces, metal portions of electronic components, or other conductive ground structures. Opening  82  may be formed by air, plastic, and other dielectric materials. Short circuit branch  98 , which may sometimes be referred to as a return path or short circuit path, may be implemented using a strip of metal, a metal trace on a dielectric support structure such as a printed circuit or plastic carrier, or other conductive path that is coupled across dielectric-filled opening  82  and therefore bridges opening  82  between resonating element arm structures (e.g., arms  102  and/or  100 ) and antenna ground  52 . 
     Antenna feed F1, which is formed using terminals  94 - 1  and  96 - 1 , may be coupled in a path that bridges opening  82 . Antenna feed F2, which is formed using terminals  94 - 2  and  96 - 2 , may be coupled in a path that bridges opening  82  in parallel with feed F1 and in parallel with short circuit path  98 . 
     Resonating element arms  100  and  102  may form respective arms in a dual arm inverted-F antenna resonating element. Arms  100  and  102  may have one or more bends. The illustrative arrangement of  FIG. 4  in which arms  100  and  102  run parallel to ground  52  and have bent ends that are separated from ground plane  52  by gaps  18  is merely illustrative. 
     Arm  100  may be a longer low-band arm that handles lower frequencies, whereas arm  102  may be a shorter high-band arm that handles higher frequencies. Arm  100  may allow antenna  40  to exhibit an antenna resonance at low band (LB) frequencies such as frequencies from 700 MHz to 960 MHz or other suitable frequencies. Arm  102  may allow antenna  40  to exhibit one or more antenna resonances at higher frequencies such as resonances at one or more frequencies in the range of 1710 to 2170 MHz (sometimes referred to as mid-band frequencies). Antenna  40  may also contain antenna resonating element structures (e.g., inverted-F antenna structures) that allow antenna  40  to resonate at higher frequencies such as frequencies between 2300 MHz to 2700 MHz (sometimes referred to as high band frequencies) or other suitable frequencies. The frequencies handled by antenna  40  may be cellular telephone frequencies and/or wireless local area network frequencies. Other frequencies (e.g., satellite navigation system frequencies, etc.) may also be handled if desired. 
     To provide antenna  40  with tuning capabilities, antenna  40  may include adjustable circuitry. The adjustable circuitry may be coupled between different locations on antenna resonating element  50 . As shown in  FIG. 4 , for example, antenna  40  may include a tunable circuit such as adjustable inductor  110 . Adjustable inductor  110  may have a first terminal (terminal  122 ) coupled to arm  100  of antenna resonating element  50  and a second terminal (terminal  124 ) coupled to antenna ground  52 . Adjustable inductor  110  may be coupled across opening  82  in parallel with return path  98 . 
     The adjustable circuitry of antenna  40  such as adjustable inductor  110  or other adjustable circuitry may be tuned using control signals from control circuitry  28  ( FIG. 2 ). Control signals from control circuitry  28  may, for example, be provided to an adjustable capacitor, adjustable inductor, or other adjustable circuit using a control signal path that is coupled between control circuitry  28  and the adjustable circuit. In the example of  FIG. 4 , control circuitry  28  may provide control signals to input  112  to adjust the inductance exhibited by adjustable inductor  110 , thereby tuning the frequency response of antenna structures  40 . 
       FIG. 5  is a schematic diagram of illustrative adjustable inductor circuitry  110  of the type that may be used in tuning antenna  40 . In the  FIG. 5  example, adjustable inductor circuitry  110  can be adjusted to produce different amounts of inductance between terminals  122  and  124 . Switch  120  is controlled by control signals on control input  112 . When switch  120  is placed in a closed state, inductor L is switched into use and adjustable inductor  110  exhibits an inductance L between terminals  122  and  124 . When switch  120  is placed in an open state, inductor L is switched out of use and adjustable inductor  110  exhibits an open circuit between terminals  122  and  124 . 
       FIG. 6  is a schematic diagram of adjustable inductor circuitry  110  in a configuration in which multiple inductors are used in providing an adjustable amount of inductance. Adjustable inductor circuitry  110  of  FIG. 6  can be adjusted to produce different amounts of inductance between terminals  122  and  124  by controlling the state of switching circuitry such as switch  120  (e.g., a single pole double throw switch) using control signals on control input  112 . For example, control signals on path  112  may be used to switch inductor L1 into use between terminals  122  and  124  while switching inductor L2 out of use, may be used to switch inductor L2 into use between terminals  122  and  124  while switching inductor L1 out of use, may be used to switch both inductors L1 and L2 into use in parallel between terminals  122  and  124 , or may be used to switch both inductors L1 and L2 out of use. The switching circuitry arrangement of adjustable inductor  110  of  FIG. 6  is therefore able to produce inductance values such as L1, L2, an inductance value associated with operating L1 and L2 in parallel, and an open circuit (when L1 and L2 are switched out of use simultaneously). 
       FIG. 7  is a diagram of an illustrative antenna of the type that may be used to form antenna  40  of device  10 . As shown in  FIG. 7 , dual arm inverted-F antenna resonating element  50  may be formed from portions  16 ′ of peripheral conductive housing structures  16 . Antenna resonating element  50  may include a first resonating element arm portion (arm)  102  and may include a second resonating element arm portion (arm)  100 . 
     Ground  52  may have an extended portion  52 E (sometimes referred to as planar conductive structures) that may be configured to form return path  98  between inverted-F antenna resonating element  50  and ground plane  52 . Extended portion  52 E may also form additional inverted-F antenna resonating element  50 ′ for supporting high band (HB) communications when feed by antenna feed F2. A gap such as slot  204  may form an opening between portion  202  of extended portion  52 E and portion  206  of ground  52 . Portion  202  of extended portion  52 E serves as the main arm of additional inverted-F antenna resonating element portion  50 ′ of antenna resonating element  50  and antenna  40 . Portion  200  of extended portion  52 E serves as a return path (short circuit path) in additional inverted-F antenna resonating element portion  50 ′ and is used to couple main arm portion  202  to ground  206 . 
     Openings  18  between arms  100  and  102  may give rise to respective capacitances such as capacitances C1 and C2. Inductors may be incorporated into antenna  40  to compensate for one or both of capacitances C1 and C2. As shown in  FIG. 7 , for example, optional inductor LC may bridge the gap  18  that is associated with capacitance C1 to compensate for the presence of capacitance C1. Adjustable inductor  110  may be controlled by control signals applied to input  112 . Inductor  110  may bridge opening  82  to couple the main resonating element arm formed from peripheral conductive structures  16 ′ to ground  52 . 
       FIG. 8  is a graph in which antenna performance (standing wave ratio SWR) for antenna  40  of  FIG. 7  has been plotted as a function of operating frequency f when radio-frequency signals are being transmitted and/or received through antenna feed F1. As shown in  FIG. 8 , the first antenna feed (feed F1) of antenna  40  may exhibit a low band resonance LB and a mid-band resonance MB. 
     In antenna  40  of  FIG. 7 , arm  100  may be longer than arm  102 , so that arm  100  may be used in supporting an antenna resonance within low band LB. Arm  102  may contribute to an antenna resonance within mid-band MB. Low band (band LB) may extend from 700 to 960 MHz or may cover another suitable range of frequencies. Mid-band MB may lie within a frequency range of 1710 MHz to 2170 MHz or other suitable frequency range above low band LB. As indicated by line  210 , adjustable inductor  110  of antenna  40  of  FIG. 7  may be used to tune the antenna resonance associated with low band LB to ensure that all of low band LB is covered by antenna  40 . When using feed F1, antenna  40  may not exhibit an appreciable response at frequencies above mid-band MB. 
       FIG. 9  is a graph in which antenna performance (standing wave ratio SWR) has been plotted as a function of operating frequency f when radio-frequency signals are being transmitted and/or received through antenna feed F2. Due to the presence of inverted-F antenna resonating element  50 ′ within inverted-F antenna resonating element  50 , antenna  40  may exhibit an antenna resonance in high band HB when using feed F2. Band HB may be a communications band in the range of 2300 to 2700 MHz or other suitable range of frequencies. Antenna  40  may also exhibit resonances in low band LB (e.g., a resonance tuned using inductor  110  as indicated by line  210 ) and mid-band MB when fed using antenna feed F2. 
     When both feeds are active in antenna  40  (e.g., when a shared transmission line is used that a splitter divides into a first transmission line coupled to feed F1 and a second transmission line coupled to feed F2 or when other paths are used to couple wireless circuitry  90  to antenna  40 ), antenna  40  may exhibit a response of the type shown in  FIG. 10 . As shown in  FIG. 10 , antenna  40  may exhibit a tunable resonance in band LB, a mid-band resonance in band MB, and a high band resonance in band HB. In low band LB, the resonance from feed F1 may dominate. Contributions from feeds F1 and F2 may participate in the resonance in mid-band MB. At frequencies in band HB, the antenna may exhibit the resonance associated with use of feed F2. 
     If desired, additional conductive structures may be added to antenna  40  to modify the frequency performance of antenna  40 . As shown in  FIG. 11 , for example, antenna  40  may have an additional conductive structure such as resonating element arm structure  100 ′. Resonating element arm structure  100 ′ may be formed from a strip of metal, patterned metal foil, traces on a printed circuit, a length of wire, internal housing structures, portions of conductive electronic components, an elongated metal path with a spiral shape, or other conductive components in device  10 . Structure  100 ′ may have a length that differs from that of arm  100 . In this way, the portion of peripheral conductive housing structures  16  that form arm  100  may serve as a first low-frequency arm (branch) of the low-frequency (longer) arm in inverted-F antenna resonating element  50  and structure  100 ′ may serve as a second low-frequency arm (branch) of the low-frequency (longer) arm in inverted-F antenna resonating element  50 . 
     The lengths of each branch may be about a quarter of a wavelength at a low band resonant frequency of interest. The longer of the two branches of the low band resonating element arm may resonant at a lower frequency than the shorter of the two branches of the low band portion of antenna resonating element  50 . The presence of two branches of the low-frequency portion of inverted-F antenna resonating element arm may give rise to two corresponding resonances in low band LB. The resonances may be overlapping (to broaden low band performance) or may be distinct (i.e., a region of unsatisfactory antenna performance may separate two acceptable low band resonances). 
       FIG. 12  is a graph in which antenna performance (standing wave ratio SWR) for antenna  40  of  FIG. 11  has been plotted as a function of operating frequency f when radio-frequency signals are being transmitted and/or received through antenna feed F1. As shown in  FIG. 12 , the first antenna feed (feed F1) of antenna  40  of  FIG. 12  may exhibit a low band resonance LB and a mid-band resonance MB. Low band resonance LB may be made up of first and second resonances LB-1 and LB-2 associated with the two different lengths of resonating element branch  100  and resonating element branch  100 ′ of inverted-F arm  100  of resonating element  50 . Arm  102  may contribute to an antenna resonance within mid-band MB. 
     Low band LB may extend from 700 to 960 MHz or may cover another suitable range of frequencies. Mid-band MB may lie within a frequency range of 1710 MHz to 2170 MHz or other suitable frequency range. As indicated by line  210 , adjustable inductor  110  of antenna  40  of  FIG. 12  may be used to tune the antenna resonances LB-1 and LB-2 that are associated with low band LB to ensure that all of low band LB is covered by antenna  40 . When using feed F1, antenna  40  may not exhibit an appreciable response at frequencies above mid-band MB. 
       FIG. 13  is a graph in which antenna performance (standing wave ratio SWR) has been plotted as a function of operating frequency f when radio-frequency signals are being transmitted and/or received through antenna feed F2 of antenna  40  in  FIG. 11 . As with antenna  40  of  FIG. 7 , the presence of inverted-F antenna resonating element portion  50 ′ of resonating element  50  may give rise to an antenna resonance in high band HB when using feed F2. Band HB may be a communications band in the range of 2300 to 2700 MHz or other suitable range of frequencies. Antenna  40  may also exhibit resonances in low band LB (e.g., resonances LB-1 and LB-2 that are tuned using inductor  110  as indicated by line  210 ) and mid-band MB when fed using antenna feed F2. 
     When both feeds are active in antenna  40  (e.g., when a shared transmission line is used that a splitter divides into a first transmission line coupled to feed F1 and a second transmission line coupled to feed F2 or when wireless circuitry  90  is otherwise coupled to feeds F1 and F2), antenna  40  may exhibit a response of the type shown in  FIG. 14 . As shown in  FIG. 14 , antenna  40  may exhibit tunable resonances LB-1 and LB-2 in band LB, a mid-band resonance in band MB, and a high band resonance in band HB. In low band LB, the resonances from feed F1 may dominate. Contributions from feeds F1 and F2 may participate in the resonance in mid-band MB. At frequencies in band HB, antenna  40  of  FIG. 11  may exhibit the resonance associated with use of feed F2 and resonating element structure  50 ′. 
     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: 20130508
Publication Date: 20160301
Grant Date: 20160301
Priority Date: 20130508
Inventors: VAZQUEZ ENRIQUE AYALA
HU HONGFEI
PASCOLINI MATTIA
MOW MATTHEW A.
TSAI MING-JU
SCHLUB ROBERT W.
DARNELL DEAN F.
OUYANG YUEHUI
JIN NANBO
HAN LIANG
PRATT DAVID
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/35", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q13/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/27", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q9/27", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/35", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/27", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 50736174