PATENT DOCUMENT

Publication Number: US-9350069-B2
Application Number: US-201213343657-A
Country: US
Kind Code: B2

Title: Antenna with switchable inductor low-band tuning

Abstract:
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 arm and an antenna ground. The antenna resonating element arm may have a shorter portion that resonates at higher communications band frequencies and a longer portion that resonates at lower communications band frequencies. A short circuit branch may be coupled between the shorter portion of the antenna resonating element arm and the antenna ground. A series-connected inductor and switch may be coupled between the longer portion of the antenna resonating element arm and the antenna ground. An antenna feed branch may be coupled between the antenna resonating element arm and the antenna ground at a location that is between the short circuit branch and the series-connected inductor and switch.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 control circuitry; 
 an antenna having an antenna resonating element arm and an antenna ground configured to resonate in at least a first communications band and a second communications band that is higher in frequency than the first communications band, having an inductor, and having a switch, wherein the inductor and switch are coupled in series between antenna resonating element arm and the antenna ground, the inductor contacts the antenna resonating element, the switch is configured to switch between an open state and a closed state in response to control signals from the control circuitry, the antenna is configured to resonate in a lower frequency portion of the first communications band and at a frequency in the second communications band in response to placing the switch in the closed state, and the antenna is configured to resonate in a higher frequency portion of the first communications band and at the frequency in the second communications band in response to placing the switch in the open state; and 
 a housing containing conductive structures that form the antenna ground for the antenna and having a peripheral conductive member that runs around at least some edges of the housing, wherein a segment of the peripheral conductive member forms the antenna resonating element arm for the antenna, the segment is separated from the antenna ground by first and second dielectric gaps, and the first and second dielectric gaps are formed on opposing external surfaces of the electronic device. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the antenna comprises an antenna feed branch coupled between the segment of the peripheral conductive member and the antenna ground. 
     
     
       3. The electronic device defined in  claim 2  further comprising a cellular telephone transceiver coupled to the antenna at the antenna feed branch. 
     
     
       4. The electronic device defined in  claim 3  further comprising a short circuit branch coupled between the segment of the peripheral conductive member and the antenna ground. 
     
     
       5. The electronic device defined in  claim 4  wherein the antenna feed branch is interposed between the short circuit branch and the inductor and switch that are coupled in series. 
     
     
       6. The electronic device defined in  claim 1  wherein the antenna resonating element arm has a longer portion that resonates in the first communications band and a shorter portion that resonates in the second communications band. 
     
     
       7. The electronic device defined in  claim 1 , wherein the second communications band is centered at the frequency in the second communications band. 
     
     
       8. The electronic device defined in  claim 7 , wherein the second communications band comprises a Long Term Evolution cellular telephone band extending from approximately 1710 MHz to 2200 MHz and the first communications band comprises a Long Term Evolution cellular telephone band extending from approximately 700 MHz to 960 MHz. 
     
     
       9. The electronic device defined in  claim 8 , wherein the lower frequency portion of the first communications band extends from approximately 700 MHz to 820 MHz and wherein the higher frequency portion of the first communications band extends from approximately 820 MHz to 960 MHz. 
     
     
       10. The electronic device defined in  claim 1 , further comprising third and fourth dielectric gaps in the peripheral conductive member, wherein the third dielectric gap is formed on a first of the opposing external surfaces of the electronic device and the fourth dielectric gap is formed on a second of the opposing external surfaces of the electronic device. 
     
     
       11. The electronic device defined in  claim 10 , further comprising:
 an additional antenna having an additional antenna resonating element arm, wherein an additional segment of the peripheral conductive member forms the additional resonating element arm for the additional antenna, and the additional antenna is separated from the antenna ground by the third and fourth dielectric gaps. 
 
     
     
       12. The electronic device defined in  claim 11 , wherein the segment of the peripheral conductive member forms a third external surface of the electronic device, the additional segment of the peripheral conductive member forms a fourth external surface of the electronic device, and the third and fourth external surfaces extend substantially perpendicular to the first and second opposing external surfaces of the electronic device. 
     
     
       13. An antenna, comprising:
 an antenna resonating element arm that comprises a segment of a peripheral conductive member of an electronic device housing; 
 an antenna ground, wherein the segment of the peripheral conductive member is separated from the antenna ground by first and second dielectric gaps formed at opposing external surfaces of the electronic device housing; 
 a series-connected inductor and switch coupled between the resonating element arm and the antenna ground, wherein the inductor is connected in series between the switch and the resonating element arm and contacts the resonating element arm; 
 a short circuit branch coupled between the antenna resonating element arm and the antenna ground; 
 an antenna feed coupled between the antenna resonating element arm and the antenna ground at a location along the antenna resonating element arm that is between the short circuit branch and the series-connected inductor and switch, wherein the antenna is configured to resonate in a lower frequency portion of a first communications band and at a frequency in a second communications band that is at higher frequencies than the first communications band in response to placing the switch in a closed state and the antenna is configured to resonate in a higher frequency portion of the first communications band and at the frequency in the second communications band in response to placing the switch in an open state; and 
 an impedance matching circuit coupled in parallel with the antenna feed and in parallel with the series-connected inductor and switch, wherein a first terminal of the impedance matching circuit is coupled to the segment of the peripheral conductive member and a second terminal of the impedance matching circuit is coupled to the antenna ground. 
 
     
     
       14. The antenna defined in  claim 13  wherein the antenna resonating element arm is configured to handle cellular telephone signals. 
     
     
       15. The electronic device defined in  claim 14  wherein the antenna resonating element arm has a longer portion that resonates in the first communications band and a shorter portion that resonates in the second communications band. 
     
     
       16. The electronic device defined in  claim 13  wherein the antenna resonating element arm has a longer portion that resonates in the first communications band and a shorter portion that resonates in the second communications band. 
     
     
       17. An antenna, comprising:
 an antenna resonating element arm that has a longer portion that resonates in a first communications band and a shorter portion that resonates in a second communications band that is associated with higher frequencies than the first communications band, wherein the antenna resonating element arm comprises a segment of a peripheral conductive member of a housing for an electronic device and the segment is located between first and second dielectric gaps in the peripheral conductive member, the first and second dielectric gaps being formed at opposing exterior surfaces of the electronic device; 
 an antenna ground; 
 a series-connected inductor and switch coupled between the resonating element arm and the antenna ground; 
 a short circuit branch coupled between the antenna resonating element arm and the antenna ground; and 
 an antenna feed coupled between the segment and the antenna ground, wherein the longer and shorter portions of the antenna resonating element arm extend from opposing sides of the antenna feed in a common plane. 
 
     
     
       18. The antenna defined in  claim 17  wherein the antenna feed is coupled between the antenna resonating element and the antenna ground at a location along the antenna resonating element arm that is between the short circuit branch and the series-connected inductor and switch. 
     
     
       19. The antenna defined in  claim 18  wherein the short circuit branch is coupled between the shorter portion of the antenna resonating element and the antenna ground. 
     
     
       20. The antenna defined in  claim 19  wherein the series-connected inductor and switch are coupled between the longer portion of the antenna resonating element arm and the antenna ground. 
     
     
       21. The antenna defined in  claim 17 , wherein the first dielectric gap is formed at a first end of the shorter portion and the second dielectric gap is formed at a first end of the longer portion, and the antenna feed contacts the segment of the peripheral conductive member at a second end of the longer portion that opposes the first end of the longer portion and at a second end of the shorter portion that opposes the first end of the shorter portion. 
     
     
       22. The antenna defined in  claim 21 , wherein the shorter portion comprises a perpendicular bend and the longer portion comprises an additional perpendicular bend, wherein the short circuit branch is coupled to the segment of the peripheral conductive member at a location between the perpendicular bend of the shorter portion and the antenna feed, and wherein the series-connected inductor and switch are coupled to the segment of the peripheral conductive member at a location between the perpendicular bend of the longer portion and the antenna feed. 
     
     
       23. The antenna defined in  claim 17 , wherein the electronic device has a length, a width that is less than the length, and a height that is less than the width, and the first and second dielectric gaps extend across the height of the electronic device from a rear face to a front face of the electronic device. 
     
     
       24. The antenna defined in  claim 17 , wherein the segment of the peripheral conductive member comprises a first portion adjacent to the first dielectric gap, a second portion adjacent to the second dielectric gap, and a third portion extending between the first and second portions, the third portion extending substantially perpendicular to the first and second portions. 
     
     
       25. The antenna defined in  claim 24 , wherein the third portion is longer than the first and second portions. 
     
     
       26. The antenna defined in  claim 24 , wherein the antenna comprises an inverted-F antenna.

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 arm and an antenna ground. The antenna resonating element arm may be formed from a segment of a peripheral conductive housing member in an electronic device. 
     The antenna resonating element arm may have a shorter portion that resonates at higher communications band frequencies and a longer portion that resonates at lower communications band frequencies. A short circuit branch may be coupled between the shorter portion of the antenna resonating element arm and the antenna ground. A series-connected inductor and switch may be coupled between the longer portion of the antenna resonating element arm and the antenna ground. An antenna feed branch may be coupled between the antenna resonating element arm and the antenna ground at a location along the antenna resonating element arm that is between the short circuit branch and the series-connected inductor and switch. 
     The switch may be adjusted to configure the antenna to resonate at different frequencies. When the switch is closed, the antenna may be configured to cover a higher portion of the lower communications bands and the higher communications band. When the switch is open, the antenna may be configured to cover a lower portion of the lower communications bands and the higher communications band. Control circuitry within an electronic device may adjust the switch in real time so that the antenna covers desired frequencies of operation. 
     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 antenna having an antenna resonating element of the type that may be formed form a segment of a peripheral conductive housing member and that has portions that support communications in low and high bands in accordance with an embodiment of the present invention. 
         FIG. 6A  is a diagram of an illustrative antenna of the type shown in  FIG. 5  that has been provided with a matching circuit and in which a main resonating element arm has been coupled to ground using an inductor in accordance with an embodiment of the present invention. 
         FIG. 6B  is a graph in which antenna performance for an antenna configuration of the type shown in  FIG. 6A  has been plotted as a function of frequency in accordance with an embodiment of the present invention. 
         FIG. 7A  is a diagram of an illustrative antenna of the type shown in  FIG. 6A  in which the shunt inductor has been removed in accordance with an embodiment of the present invention. 
         FIG. 7B  is a graph in which antenna performance for an antenna configuration of the type shown in  FIG. 7A  has been plotted as a function of frequency in accordance with an embodiment of the present invention. 
         FIG. 8A  is a diagram of an illustrative dual-band antenna having a tunable low band response in accordance with an embodiment of the present invention. 
         FIG. 8B  is a graph in which antenna performance for an antenna configuration of the type shown in  FIG. 8A  has been plotted as a function of frequency showing how antenna response can be tuned by opening and closing the switch of  FIG. 8A  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 cover glass layer may cover the surface of display  14 . Buttons such as button  19  may pass through openings in the cover glass. The cover glass 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 ). 
     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 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 2200 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, for example, 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 antenna in its closed position, the antenna may exhibit a second frequency response. As an example, antenna  40  may exhibit both a low band response and a high band response. Adjustment of the state of the switch may be used to tune the low band response of the antenna without appreciably affecting the high band response. The ability to adjust the low band 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  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 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 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. 
       FIG. 4  is a diagram showing how a radio-frequency signal path such as path  44  may be used to convey radio-frequency signals between antenna  40  and radio-frequency transceiver  42 . Antenna  40  may be one of antennas  40  of  FIG. 2 . Radio-frequency transceiver  42  may be a receiver and/or transmitter in wireless communications circuitry  34  ( FIG. 3 ) such as receiver  35 , wireless local area network transceiver  36  (e.g., a transceiver operating at 2.4 GHz, 5 GHz, 60 GHz, or other suitable frequency), cellular telephone transceiver  38 , or other radio-frequency transceiver circuitry for receiving and/or transmitting radio-frequency signals. 
     Signal path  44  may include one or more transmission lines such as one or more segments of coaxial cable, one or more segments of microstrip transmission line, one or more segments of stripline transmission line, or other transmission line structures. Signal path  44  may include a positive conductor such as positive signal line  44 A and may include a ground conductor such as ground signal line  44 B. Antenna  40  may have an antenna feed with a positive antenna feed terminal (+) and a ground antenna feed terminal (−). If desired, circuitry such as filters, impedance matching circuits, switches, amplifiers, and other circuits may be interposed within path  44 . 
       FIG. 5  is a diagram showing how structures such as peripheral conductive member segment  16 ′ of  FIG. 3  may be used in forming antenna  40 . In the illustrative configuration of  FIG. 5 , antenna  40  includes antenna resonating element  90  and antenna ground  52 . Antenna resonating element may have a main resonating element arm formed from peripheral conductive member  16 ′ (e.g., a segment of peripheral conductive member  16  of  FIG. 1 ). Gaps such as gaps  18 A and  18 B may be interposed between the ends of resonating element arm  16 ′ and ground  52 . Short circuit branch  94  may be coupled between arm  16 ′ and ground  52 . Antenna feed branch  92  may be coupled between arm  16 ′ and ground  52  in parallel with short circuit branch  94 . Antenna feed branch  92  may include a positive antenna feed terminal (+) and a ground antenna feed terminal (−). As described in connection with  FIG. 4 , lines  44 A and  44 B in signal path  44  may be respectively coupled to terminals (+) and (−) in antenna feed  92 . 
     Resonating element arm  16 ′ may have a longer portion (LB) that is associated with a low band resonance and that can be used for handling low band wireless communications. Resonating element arm  16 ′ may also have a shorter portion (HB) that is associated with a high band resonance and that can be used for handling high band wireless communications. The low band portion of arm  16 ′ may, for example, be used in handling signals at frequencies of 700 MHz to 960 MHz (as an example). The high band portion of arm  16 ′ may, for example, be used in handling signals at frequencies of 1710 MHz to 2200 MHz (as an example). These are merely illustrative low band and high band frequencies of operation for antenna  40 . Antenna  40  may be configured to handle any suitable frequencies of interest for device  10 . 
       FIG. 6A  shows how antenna  40  may be provided with an impedance matching circuit such as impedance matching circuit  96 . Matching circuit  96  may be formed from a network or one or more electrical components (e.g., resistors, capacitors, and/or inductors) and may be configured so that antenna  40  exhibits a desired frequency response (e.g., so that antenna  40  covers desired communications bands of interest). As an example, matching circuit  96  may include an inductor coupled in parallel with feed  92  and/or additional electrical components. 
     As shown in  FIG. 6A , impedance matching circuit  96  may be coupled between antenna resonating element arm  16 ′ and antenna ground  52  in parallel with antenna feed branch  92 . Short circuit branch  94  may be coupled in parallel with feed branch  92  between resonating element arm  16 ′ and ground (e.g., on the high band side of feed  92 , which is to the left of feed  92  in the illustrative configuration of  FIG. 6A ). Shunt inductor  98  may also be coupled in parallel with antenna feed branch  92  between arm  16 ′ and ground  52  (e.g., on the low band side of feed  92 , which is to the right of feed  92  in the illustrative configuration of  FIG. 6A ). 
     The antenna configuration of  FIG. 6A  may be characterized by a performance curve such as standing-wave-ratio versus frequency curve  100  of  FIG. 6B . As shown in  FIG. 6B , antenna  40  of  FIG. 6A  may be characterized by a low band resonance centered at a frequency f 1  (e.g., a resonance produced using portion LB of antenna  40  of  FIG. 6A ) and may be characterized by a high band resonance at frequency f 3  (e.g., a resonance produced using portion HB of antenna  40  of  FIG. 6A ). 
     The low band resonance of curve  100  at frequency f 1  may not be sufficiently wide to cover all low band frequencies of interest.  FIG. 7A  shows how antenna  40  of  FIG. 6A  may be modified so that the low band resonance cover a different set of low band frequencies. In the illustrative configuration of  FIG. 7A , shunt inductor  98  of  FIG. 6A  has been removed. The antenna configuration of  FIG. 7A  may be characterized by a performance curve such as standing-wave-ratio versus frequency curve  102  of  FIG. 7B . As shown in  FIG. 7B , antenna  40  of  FIG. 7A  may be characterized by a low band resonance centered at a frequency f 2  (e.g., a resonance produced using portion LB of antenna  40  of  FIG. 6A  that is higher in frequency than frequency f 1 ). The high band resonance of antenna  40  of  FIG. 7A  may cover the same high band frequencies as antenna  40  of  FIG. 6A  (as an example). 
     It may be desirable to cover both the low frequency band at frequency f 1  ( FIG. 6B ) and the low frequency band at frequency f 2  ( FIG. 7B ) in device  10 . This can be accomplished by providing antenna  40  with switching circuitry such as switch  104  of  FIG. 8A . As shown in  FIG. 8A , short circuit branch  94  may be coupled between antenna resonating element arm  16 ′ and antenna ground  52  at a first location along the length of antenna resonating element arm  16 ′. Switch  104  and inductor  98  may be coupled in series and may be used to form an adjustable inductor circuit that is coupled between antenna resonating element arm  16 ′ and antenna ground  52  at a second location along the length of antenna resonating element arm  16 ′. Antenna feed branch  92  may be coupled between antenna resonating element arm  16 ′ and antenna ground  52  at a third location along the length of antenna resonating element arm  16 ′ interposed between the short circuit branch at the first location and the series-connected inductor and switch and the second location. 
     As shown in  FIG. 8A , switch  104  may be provided with control signals at control input  105  from control circuitry  28  ( FIG. 2 ). The control signals may be adjusted in real time to control the frequency response of antenna  40 . For example, when it is desired to configure antenna  40  of  FIG. 8A  to cover the communications band at frequency f 1  of  FIG. 6B , switch  104  may be placed in its closed state. When switch  104  is closed, inductor  98  will be electrically coupled between resonating element arm  16 ′ and ground  52 , so that antenna  40  of  FIG. 8A  will have a configuration of the type shown in  FIG. 6A . When switch  104  is placed in its open state, an open circuit will be formed that electrically decouples inductor  98  from antenna  40  of  FIG. 8A . With inductor  98  switched out of use in this way, antenna  40  of  FIG. 8A  will have a configuration of the type shown in  FIG. 7A . 
     The antenna configuration of  FIG. 8A  may be characterized by a performance curve such as standing-wave-ratio versus frequency curve  106  of  FIG. 8B . As shown in  FIG. 8B , antenna  40  of  FIG. 8A  may be characterized by a low band resonance centered at a frequency f 1  (curve  108 ) when switch  104  is closed and may be characterized by a low band resonance centered at a frequency f 2  (curve  106 ) when switch  104  is open. The high band resonance at frequency f 3  may be relatively unaffected by the position of switch  104  (i.e., the high band resonance of antenna  40  of  FIG. 8A  may cover a communications band centered at frequency f 3  when switch  104  is in its open position and when switch  104  is in its closed position). 
     The frequency bands associated with antenna  40  of  FIGS. 8A and 8B  may correspond to wireless local area network bands, satellite navigation bands, television bands, radio bands, cellular telephone bands, or other communications band of interest. For example, the communications band associated with frequency f 1  may extend from about 700 to 820 MHz and may be used to handle Long Term Evolution (LTE) cellular telephone communications, the communications band associated with frequency f 2  may extend from about 820 to 960 MHz and may be associated with Global System for Mobile Communications (GSM) cellular telephone communications, Universal Mobile Telecommunications System (UMTS) cellular telephone communications, and/or optional LTE cellular telephone communications, and the communications band associated with frequency f 3  may extend from about 1710 to 2200 MHz and may be used in handling GSM, LTE, and/or UMTS cellular telephone communications (as examples). Other types of communications traffic may be handled using antenna  40  of  FIG. 8A  if desired. These are merely illustrative examples. 
     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: 20120104
Publication Date: 20160524
Grant Date: 20160524
Priority Date: 20120104
Inventors: PASCOLINI MATTIA
SCHLUB ROBERT W.
JIN NANBO
MOW MATTHEW A.
HU HONGFEI
NICKEL JOSHUA G.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/357", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/357", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/357", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 47553472