PATENT DOCUMENT

Publication Number: US-9257750-B2
Application Number: US-201313895194-A
Country: US
Kind Code: B2

Title: Electronic device with multiband antenna

Abstract:
An electronic device may have an antenna for providing coverage in wireless communications bands of interest. The wireless communications bands may include first, second, third, and fourth communications bands. The antenna may have an antenna resonating element with first, second, and third arms and may have an antenna ground. The antenna ground may be formed form metal housing structures and other conductive structures in the electronic device. The first arm may be configured to exhibit an antenna resonance in the first and third communications bands. The second arm may be configured to exhibit an antenna resonance in the second communications band. The third arm may be configured to exhibit an antenna resonance in the fourth communications band. The third arm may be located between the first arm and the ground. A diagonal crossover path may pass over a return path and may couple the second and third arms.

Claims:
What is claimed is: 
     
       1. An inverted-F antenna operable in at least first, second, third, and fourth communications bands, comprising:
 an antenna ground; and 
 an antenna resonating element having a first arm that resonates in the first and third communications bands, a second arm that resonates in the second communications band, and a third arm that resonates in the fourth communications band and having a return path that couples the antenna resonating element to the antenna ground, wherein the antenna resonating element includes a crossover path that crosses the return path without contacting the return path. 
 
     
     
       2. The inverted-F antenna defined in  claim 1  wherein the antenna resonating element further comprises a positive antenna feed terminal and a ground antenna feed terminal, wherein the crossover path has a first end that is coupled to the positive antenna feed terminal and a second end that is coupled to the second arm. 
     
     
       3. The inverted-F antenna defined in  claim 2  wherein the antenna resonating element further comprises a flexible printed circuit substrate on which the antenna resonating element is formed, wherein the first arm and the crossover path are formed from metal traces on different layers of the flexible printed circuit substrate. 
     
     
       4. The inverted-F antenna defined in  claim 3  wherein the return path extends along a first axis, wherein the crossover path is an elongated metal trace that extends along a second axis, and wherein the second axis lies at a non-zero angle with respect to the first axis. 
     
     
       5. The inverted-F antenna defined in  claim 3  wherein the crossover path is configured to cross over the return path at a non-perpendicular angle. 
     
     
       6. The inverted-F antenna defined in  claim 5  further comprising a capacitor that couples a portion of the first arm to the antenna ground. 
     
     
       7. The inverted-F antenna defined in  claim 6  further comprising at least one capacitive proximity sensor electrode. 
     
     
       8. The inverted-F antenna defined in  claim 1  wherein the crossover path has an end that is coupled to the second arm. 
     
     
       9. The inverted-F antenna defined in  claim 8  wherein the crossover path has an opposing end that is coupled to the third arm. 
     
     
       10. The inverted-F antenna defined in  claim 9  wherein the antenna ground comprises a portion of an electronic device housing. 
     
     
       11. The inverted-F antenna defined in  claim 10  wherein the crossover path is configured to cross over the return path at a non-perpendicular angle. 
     
     
       12. The inverted-F antenna defined in  claim 11  wherein the first communications band includes frequencies between 700 MHz and 960 MHz, wherein the first arm is configured to exhibit an antenna resonance at the frequencies between 700 MHz and 960 MHz, wherein the second communications band includes frequencies between 1710 MHz and 2170 MHz, wherein the second arm is configured to exhibit an antenna resonance at the frequencies between 1710 MHz and 2170 MHz, wherein the third communications band includes frequencies between 2300 MHz and 2700 MHz, wherein the first arm is configured to exhibit an antenna resonance at the frequencies between 2300 MHz and 2700 MHz, wherein the fourth communications band includes frequencies between 5150 MHz and 5850 MHz, and wherein the third arm is configured to exhibit an antenna resonance at the frequencies between 5150 MHz and 5850 MHz. 
     
     
       13. An inverted-F antenna operable in at least first, second, third, and fourth communications bands, comprising:
 an antenna ground; and 
 antenna resonating element having a first arm that resonates in the first and third communications bands, a second arm that resonates in the second communications band, and a third arm that resonates in the fourth communications band and having a return path that couples the antenna resonating element to the antenna ground, wherein the third arm is interposed between the first arm and the antenna ground and the second arm is interposed between the first arm and the antenna ground. 
 
     
     
       14. The inverted-F antenna defined in  claim 13  wherein the first communications band includes frequencies between 700 MHz and 960 MHz and wherein the first arm is configured to exhibit an antenna resonance at the frequencies between 700 MHz and 960 MHz. 
     
     
       15. The inverted-F antenna defined in  claim 14  wherein the second communications band includes frequencies between 1710 MHz and 2170 MHz and wherein the second arm is configured to exhibit an antenna resonance at the frequencies between 1710 MHz and 2170 MHz. 
     
     
       16. The inverted-F antenna defined in  claim 15  wherein the third communications band includes frequencies between 2300 MHz and 2700 MHz and wherein the first arm is configured to exhibit an antenna resonance at the frequencies between 2300 MHz and 2700 MHz. 
     
     
       17. The inverted-F antenna defined in  claim 16  wherein the fourth communications band includes frequencies between 5150 MHz and 5850 MHz and wherein the third arm is configured to exhibit an antenna resonance at the frequencies between 5150 MHz and 5850 MHz. 
     
     
       18. The inverted-F antenna defined in  claim 17  wherein the antenna resonating element includes a crossover path coupled to the second arm and wherein the crossover path crosses the return path at a non-perpendicular angle without touching the return path. 
     
     
       19. An antenna comprising:
 an antenna resonating element having first, second, and third arms, wherein the antenna resonating element is configured to exhibit antenna resonances in first, second, third, and fourth communications bands; 
 an antenna ground; 
 a return path that is coupled between the antenna resonating element and the antenna ground; and 
 a crossover path that crosses the return path without touching the return path and that is coupled between the second and third arms. 
 
     
     
       20. The antenna defined in  claim 19  wherein the third arm is configured to exhibit an antenna resonance at frequencies between 5150 MHz and 5850 MHz and wherein the third arm is between the first arm and the antenna ground.

Description:
BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to antennas in electronic devices. 
     Electronic devices such as portable computers and handheld electronic devices are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry to communicate using cellular telephone bands. Electronic devices may use short-range wireless communications links to handle communications with nearby equipment. 
     It can be difficult to incorporate antennas and electrical components successfully into an electronic device. Some electronic devices are manufactured with small form factors, so space is limited. In many electronic devices, the presence of conductive structures associated with components and housing structures can influence the performance of antennas. At the same time, it may be desirable for antennas to handle multiple communications bands. Configuring antennas to handle multiple communications bands can be challenging, particularly when antennas are mounted in an electronic device in close proximity to conductive structures such as housing structures and electrical components. 
     It would therefore be desirable to be able to provide improved antennas for handling multiple communications bands in electronic devices. 
     SUMMARY 
     An electronic device may have an antenna for providing coverage in wireless communications bands of interest. The wireless communications bands may include first, second, third, and fourth communications bands. 
     The antenna may have an inverted-F antenna resonating element with first, second, and third arms and may have an antenna ground. The antenna ground may be formed form metal housing structures and other conductive structures in the electronic device. The antenna resonating element may be formed form metal traces on a dielectric support structure such as a flexible printed circuit. 
     The first arm of the antenna resonating element may be configured to exhibit an antenna resonance in the first and third communications bands. The second arm may be configured to exhibit an antenna resonance in the second communications band. The third arm may be configured to exhibit an antenna resonance in the fourth communications band. The third arm may be located between the first arm and the ground. An electrical component such as a capacitor may be coupled between a tip portion of the first arm and the antenna ground. During operation, the first arm resonates in the first and third communications bands, the second arm resonates in the second communications band, and/or the third arm resonates in the fourth communications band. 
     The antenna may have an antenna feed coupled to a transmission line. The antenna feed may have a positive antenna feed terminal that is coupled to the third arm and a ground antenna feed coupled to the antenna ground. A return path may couple the antenna resonating element to the antenna ground. A crossover path may pass over the return path at a non-perpendicular angle without contacting the return path. The crossover path may have a first end that is coupled to the second arm and an opposing second end that is coupled to the third arm. The crossover path and antenna resonating element structures may be formed using multiple layers of metal traces on the flexible printed circuit substrate. A proximity sensor may be implemented using a capacitive proximity sensor electrode that is supported by the flexible printed circuit substrate. 
     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 front perspective view of an illustrative electronic device of the type that may be provided with antenna structures in accordance with an embodiment of the present invention. 
         FIG. 2  is a rear perspective view of an illustrative electronic device such as the electronic device of  FIG. 1  in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional side view of a portion of an electronic device having antenna structures in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of illustrative antenna structures and other wireless circuitry in accordance with an embodiment of the present invention. 
         FIG. 5  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency in accordance with an embodiment of the present invention. 
         FIG. 6  is a perspective view of an illustrative antenna in accordance with an embodiment of the present invention. 
         FIG. 7  is a perspective view of the antenna of  FIG. 6  showing illustrative current flow patterns when operated at a low band frequency in accordance with an embodiment of the present invention. 
         FIG. 8  is a perspective view of the antenna of  FIG. 6  showing illustrative current flow patterns when operated at a middle band frequency in accordance with an embodiment of the present invention. 
         FIG. 9  is a perspective view of the antenna of  FIG. 6  showing illustrative current flow patterns when operated at a high band frequency in accordance with an embodiment of the present invention. 
         FIG. 10  is a perspective view of the antenna of  FIG. 6  showing illustrative current flow patterns when operated at an upper band frequency above the high band frequency in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional side view of a portion of a flexible printed circuit of the type that may have metal antenna and proximity sensor electrode traces in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative wireless electronic device with antenna structures is shown in  FIG. 1 . As shown in  FIG. 1 , device  10  may have a display such as display  50 . Display  50  may be mounted on a front (top) surface of device  10  or may be mounted elsewhere in device  10 . Device  10  may have a housing such as housing  12 . Housing  12  may have curved, angled, or vertical sidewall portions that form the edges of device  10  and a relatively planar portion that forms the rear surface of device  10  (as an example). Housing  12  may also have other shapes, if desired. 
     Housing  12  may be formed from conductive materials such as metal (e.g., aluminum, stainless steel, etc.), carbon-fiber composite material or other fiber-based composites, glass, ceramic, plastic, or other materials. A radio-frequency-transparent window such as window  58  may be formed in housing  12  (e.g., in a configuration in which the rest of housing  12  is formed from conductive structures). Window  58  may be formed from plastic, glass, ceramic, or other dielectric material. Antenna structures, and, if desired, proximity sensor structures for use in determining whether external objects are present in the vicinity of the antenna structures may be formed in the vicinity of window  58 . If desired, antenna structures and proximity sensor structures that are formed adjacent to the antenna structures or as part of the antenna structures may be mounted behind a dielectric portion of housing  12  (e.g., in a configuration in which housing  12  is formed from plastic or other dielectric material). 
     Device  10  may have user input-output devices such as button  59 . Display  50  may be a touch screen display that is used in gathering user touch input. The surface of display  50  may be covered using a display cover layer such as a planar cover glass member or a clear layer of plastic. The central portion of display  50  (shown as region  56  in  FIG. 1 ) may be an active region that displays images and that is sensitive to touch input. Peripheral portions of display  50  such as region  54  may form an inactive region that is free from touch sensor electrodes and that does not display images. 
     An opaque masking layer such as opaque ink or plastic may be placed on the underside of display  50  in peripheral region  54  (e.g., on the underside of the display cover layer). This layer may be transparent to radio-frequency signals. The conductive touch sensor electrodes and display pixel structures and other conductive structures in region  56  tend to block radio-frequency signals. However, radio-frequency signals may pass through the display cover layer (e.g., through a cover glass layer) and opaque masking layer in inactive display region  54  (as an example). Radio-frequency signals may also pass through antenna window  58  or dielectric housing walls in a housing formed from dielectric material. Lower-frequency electromagnetic fields may also pass through window  58  or other dielectric housing structures, so capacitance measurements for a proximity sensor may be made through antenna window  58  or other dielectric housing structures, if desired. 
     With one suitable arrangement, housing  12  may be formed from a metal such as aluminum. Portions of housing  12  in the vicinity of antenna window  58  may be used as antenna ground. Antenna window  58  may be formed from a dielectric material such as polycarbonate (PC), acrylonitrile butadiene styrene (ABS), a PC/ABS blend, or other plastics (as examples). Window  58  may be attached to housing  12  using adhesive, fasteners, or other suitable attachment mechanisms. To ensure that device  10  has an attractive appearance, it may be desirable to form window  58  so that the exterior surfaces of window  58  conform to the edge profile exhibited by housing  12  in other portions of device  10 . For example, if housing  12  has straight edges  12 A and a flat bottom surface, window  58  may be formed with a right-angle bend and vertical sidewalls. If housing  12  has curved edges  12 A, window  58  may have a similarly curved exterior surface along the edge of device  10 . 
       FIG. 2  is a rear perspective view of device  10  of  FIG. 1  showing how device  10  may have a relatively planar rear surface  12 B and showing how antenna window  58  may be rectangular in shape with portions that match the shape of housing edges  12 A. Antenna window  58  may have curved walls, planar walls, or walls of other shapes, if desired. Display  50  may be mounted on the opposing front surface of housing  12  of device  10 . 
     A cross-sectional view of device  10  taken along line  1300  of  FIG. 2  and viewed in direction  1302  is shown in  FIG. 3 . As shown in  FIG. 3 , antenna structures  204  may be mounted within device  10  in the vicinity of antenna window  58 . Structures  204  may include conductive material that serves as an antenna resonating element for an antenna. The antenna may be fed using transmission line  212 . Transmission line  212  may have a positive signal conductor that is coupled to a positive antenna feed terminal (e.g., a feed terminal associated with a metal antenna resonating element trace on a dielectric support in structures  204 ) and a ground signal conductor that is coupled to a ground antenna feed terminal (i.e., antenna ground formed from conductive ground traces on a dielectric carrier in antenna structures  204  and/or grounded structures such as grounded portions of housing  12 ). 
     The antenna resonating element formed from structures  204  may be based on any suitable antenna resonating element design (e.g., structures  204  may form a patch antenna resonating element, a single arm inverted-F antenna structure, a dual-arm inverted-F antenna structure, a three-arm inverted-F antenna structure, other suitable multi-arm or single arm inverted-F antenna structures, a closed and/or open slot antenna structure, a loop antenna structure, a monopole, a dipole, a planar inverted-F antenna structure, a hybrid of any two or more of these designs, etc.). Configurations in which antenna structures  204  form an inverted-F antenna are sometimes described herein as an example. 
     Housing  12  may serve as antenna ground for an antenna formed from structure  204  and/or other conductive structures within device  10  and antenna structures  204  may serve as ground (e.g., conductive components, traces on printed circuits, etc.). 
     Structures  204  may include patterned conductive structures such as patterned metal structures. The patterned conductive structures may, if desired, be supported by a dielectric carrier. The conductive structures may be formed from a coating, from metal traces on a flexible printed circuit, or from metal traces formed on a plastic carrier using laser-processing techniques or other patterning techniques. Structures  204  may also be formed from stamped metal foil or other metal structures. In configurations for antenna structures  204  that include a dielectric carrier, metal layers may be formed directly on the surface of the dielectric carrier and/or a flexible printed circuit that includes patterned metal traces may be attached to the surface of the dielectric carrier. If desired, conductive material in structures  204  may also form one or more proximity sensor capacitor electrodes. 
     During operation of the antenna formed from structures  204 , radio-frequency antenna signals can be conveyed through dielectric window  58 . Radio-frequency antenna signals associated with structures  204  may also be conveyed through a display cover member such as cover layer  60 . Display cover layer  60  may be formed from one or more clear layers of glass, plastic, or other materials. Display  50  may have an active region such as region  56  in which cover layer  60  has underlying conductive structure such as display module  64 . The structures in display module  64  such as touch sensor electrodes and active display pixel circuitry may be conductive and may therefore attenuate radio-frequency signals. In region  54 , however, display  50  may be inactive (i.e., module  64  may be absent). An opaque masking layer such as plastic or ink  62  may be formed on the underside of transparent cover glass  60  in region  54  to block antenna structures  204  from view by a user of device  10 . Opaque material  62  and the dielectric material of cover layer  60  in region  54  may be sufficiently transparent to radio-frequency signals that radio-frequency signals can be conveyed through these structures during operation of device  10 . 
     Device  10  may include one or more internal electrical components such as components  23 . Components  23  may include storage and processing circuitry such as microprocessors, digital signal processors, application specific integrated circuits, memory chips, and other control circuitry. Components  23  may be mounted on one or more substrates such as substrate  79  (e.g., rigid printed circuit boards such as boards formed from fiberglass-filled epoxy, flexible printed circuits, molded plastic substrates, etc.). Components  23  may include input-output circuitry such as sensor circuitry (e.g., capacitive proximity sensor circuitry), wireless circuitry such as radio-frequency transceiver circuitry (e.g., circuitry for cellular telephone communications, wireless local area network communications, satellite navigation system communications, near field communications, and other wireless communications), amplifier circuitry, and other circuits. Connectors such as connector  81  may be used in interconnecting circuitry  23  to communications paths such as transmission line path  212 . 
     Conductive structures for antenna structures  204  may be supported by a dielectric carrier. Antenna structures  204  may, for example, have conductive structures such as metal structures that are supported by a solid plastic member, a hollow plastic member, or other dielectric carrier structures. The conductive structures may be metal traces that are formed on the surface of a dielectric carrier using laser-based deposition techniques, physical vapor deposition techniques, electrochemical deposition, blanket metal deposition followed by photolithographic patterning, ink-jet printing deposition techniques, etc. The conductive structures may also be metal traces that are formed on a rigid printed circuit board (e.g., a printed circuit board formed from a substrate such as fiberglass-filled epoxy), metal traces that are formed on a flexible printed circuit (e.g., a printed circuit formed from a layer of polyimide or a sheet of other polymer) that is mounted on a dielectric carrier (e.g., a carrier formed from molded plastic or other material), may be other metal structures supported by a carrier (e.g., patterned metal foil), or may be other conductive structures. 
     Dielectric carriers for supporting metal antenna traces or a flexible printed circuit or other structure that includes metal antenna traces may be formed from a dielectric material such as glass, ceramic, or plastic. As an example, a dielectric carrier for antenna(s) in device  10  may be formed from plastic parts that are molded and/or machined into a desired shape such as a rectangular prism shape (rectangular box shape), a three-dimensional solid shape with one or more curved surfaces (e.g., a box shape with a curved outer surface that matches a corresponding curved housing edge  12 A), or other shapes. In general, dielectric carrier shapes such as box or prism shapes with different numbers of sides and/or one or more curved surfaces or other three-dimensional carrier shapes may be used for antenna structures  204 . The illustrative configuration of  FIG. 3  in which antenna structures  204  have a rectangular cross-sectional shape is merely illustrative. 
     A diagram of an illustrative configuration that may be used for electronic device  10  is shown in  FIG. 4 . As shown in  FIG. 4 , electronic device  10  may include control circuitry  29 . Control circuitry  29  may include storage and processing circuitry for controlling the operation of device  10 . Control circuitry  29  may, for example, 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. Control circuitry  29  may include processing circuitry based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Control circuitry  29  may be used to run software on device  10 , such as operating system software and application software. Using this software, control circuitry  29  may, for example, transmit and receive wireless data, tune antennas to cover communications bands of interest, and perform other functions related to the operation of device  10 . 
     Input-output devices  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 communications circuitry such as wired communications circuitry. Device  10  may also use wireless circuitry such as transceiver circuitry  206  and antenna structures  204  to communicate over one or more wireless communications bands. 
     Input-output devices  30  may also include input-output components with which a user can control the operation of device  10 . A user may, for example, supply commands through input-output devices  30  and may receive status information and other output from device  10  using the output resources of input-output devices  30 . 
     Input-output devices  30  may include proximity sensor circuitry  224  such as capacitive proximity sensor circuitry that uses portions of antenna structures  204  or other conductive structures in device  10  as capacitive proximity sensor electrodes. Proximity sensor circuitry  224  may be coupled to proximity sensor electrode structures in antenna structures  204  or elsewhere in device  10  using paths such as path  226 . A capacitive proximity sensor may, for example, be used to determine when a user&#39;s body or other external object is in the vicinity of antenna structures  204 . Proximity sensors for device  10  may also be formed using light-based proximity sensor structures, acoustic proximity sensor structures, etc. 
     Input-output devices  30  may also include sensors and status indicators such as an ambient light sensor, a temperature sensor, a pressure sensor, a magnetic sensor, an accelerometer, and light-emitting diodes and other components for gathering information about the environment in which device  10  is operating and providing information to a user of device  10  about the status of device  10 . Audio components in devices  30  may include speakers and tone generators for presenting sound to a user of device  10  and microphones for gathering user audio input. 
     Devices  30  may include one or more displays such as display  50  of  FIG. 1 . Displays may be used to present images for a user such as text, video, and still images. Sensors in devices  30  may include a touch sensor array that is formed as one of the layers in display  14 . During operation, user input may be gathered using buttons and other input-output components in devices  30  such as touch pad sensors, buttons, joysticks, click wheels, scrolling wheels, touch sensors such as a touch sensor array in a touch screen display or a touch pad, key pads, keyboards, vibrators, cameras, and other input-output components. 
     Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry such as transceiver circuitry  206  that is formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas such as antenna structures  204 , 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 radio-frequency transceiver circuits for handling multiple radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  206  for handling cellular telephone communications, wireless local area network signals, and satellite navigation system signals such as signals at 1575 MHz from satellites associated with the Global Positioning System. Transceiver circuitry  206  may handle 2.4 GHz and 5 GHz bands for WiFi®(IEEE 802.11) communications or other wireless local area network communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry  206  may use cellular telephone transceiver circuitry for handling wireless communications in cellular telephone bands such as the bands in the range of 700 MHz to 2700 MHz (as examples). 
     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 also include circuitry for handing near field communications. 
     Wireless communications circuitry  34  may include antenna structures  204 . Antenna structures  204  may include one or more antennas. Antenna structures  204  may include inverted-F antennas, patch antennas, loop antennas, monopoles, dipoles, single-band antennas, dual-band antennas, tri-band or quad-band antennas, other antennas that cover more than two bands, or other suitable antennas. Configurations such as the illustrative configuration of  FIG. 4  in which at least one antenna in device  10  is formed from an inverted-F antenna structure such as a multiband inverted-F antenna are sometimes described herein as an example. 
     If desired, antenna structures  204  may be provided with one or more tunable components or other tunable circuitry. Discrete components such as capacitors, inductors, and resistors may be incorporated into the tunable circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). Tunable circuitry in antenna structures  204  may be controlled by control signals from control circuitry  29 . For example, control circuitry  29  may supply control signals to tunable circuitry via one or more control paths during operation of device  10  whenever it is desired to tune antenna structures  204  to cover a desired communications band. Path  222  may be used to convey data between control circuitry  29  and wireless communications circuitry  34  (e.g., when transmitting wireless data or when receiving and processing wireless data). 
     Transceiver circuitry  206  may be coupled to antenna structures  204  by signal paths such as signal path  212 . Signal path  212  may include one or more transmission lines. As an example, signal path  212  of  FIG. 4  may be a transmission line having a positive signal conductor such as line  214  and a ground signal conductor such as line  216 . Lines  214  and  216  may form parts of a coaxial cable or a microstrip transmission line (as examples). A matching network formed from components such as inductors, resistors, and capacitors may be used in matching the impedance of antenna structures  204  to the impedance of transmission line  212 . Matching network components may be provided as discrete components (e.g., surface mount technology components) or may be formed from housing structures, printed circuit board structures, traces on plastic supports, etc. Components such as these may also be used in forming fixed circuit elements such as a fixed capacitor coupled to an antenna resonating element trace in antenna structures  204  and/or a tunable element such as a tunable capacitor or other tunable circuitry in antenna structures  204 . 
     Transmission line  212  may be coupled to antenna feed structures associated with antenna structures  204 . As an example, antenna structures  204  may form an inverted-F antenna having an antenna feed with a positive antenna feed terminal such as terminal  218  and a ground antenna feed terminal such as ground antenna feed terminal  220 . Positive transmission line conductor  214  may be coupled to positive antenna feed terminal  218  and ground transmission line conductor  216  may be coupled to ground antenna feed terminal  220 . Other types of antenna feed arrangements may be used if desired. The illustrative feeding configuration of  FIG. 4  is merely illustrative. 
     Fixed and tunable circuitry in antenna structures  204  may be formed from one or more fixed and tunable circuits such as circuits based on capacitors, resistors, inductors, and switches. Fixed and tunable circuitry in antenna structures  204  may be implemented using discrete components mounted to a printed circuit such as a rigid printed circuit board (e.g., a printed circuit board formed from glass-filled epoxy) or a flexible printed circuit formed from a sheet of polyimide or a layer of other flexible polymer, a plastic carrier, a glass carrier, a ceramic carrier, or other dielectric substrate. As an example, fixed and/or tunable circuitry in antenna structures  204  may be coupled to a dielectric carrier of the type that may be used in supporting antenna resonating element traces for antenna structures  204  ( FIG. 3 ). If desired, antenna structures  204  may omit tunable circuitry (i.e., antenna structures  204  may be implemented using only fixed components). 
     In the example of  FIG. 4 , antenna structures  204  form a multiband inverted-F antenna. Inverted-F antenna  204  has inverted-F antenna resonating element  300  and antenna ground  302 . Inverted-F antenna resonating element  300  has three arms that help antenna  204  cover four communications bands. The four communications bands may include a low communications band (sometimes referred to as low band LB), a middle communications band (sometimes referred to as middle band MB), a high communications band (sometimes referred to as high band HB), and an upper communications band (sometimes referred to as upper or top band TB). Low band LB may cover frequencies in the range of 700 MHz to 960 MHz or other suitable frequency range. Middle band MB may cover frequencies in the range of 1710 MHz to 2170 MHz or other suitable frequency range. High band HB may cover frequencies in the range of 2300 MHz to 2700 MHz or other suitable frequency range. The frequencies associated with low band LB and middle band MB may be cellular telephone frequencies (as an example). The frequencies associated with high band HB may be cellular telephone frequencies and/or frequencies from 2400 MHz to 2480 MHz that are associated with 2.4 GHz IEEE 802.11 wireless local area network communications and/or Bluetooth signals (as examples). Upper band TB may cover frequencies in the range of 5150 MHz to 5850 MHz (e.g., 5 GHz IEEE 802.11 wireless local area network signals). 
     The three arms in inverted-F antenna resonating element  300  include arms  304 ,  312 , and  310 . Arm  304  is the longest of the three arms in element  300 . Arm  312  is shorter than arm  304  and longer than arm  310 . Conductive path  308  may couple arm  304  to arms  310  and  312 . Positive antenna feed terminal  218  may be coupled to path  308 , arm  310 , and arm  312  (via path  318 ) and may be coupled to arm  304  via the conductive structures of path portion  308  of resonating element  300 . Antenna feed terminal  220  may be coupled to antenna ground  302  across dielectric opening  316 . 
     Arm  304  includes a segment that runs parallel to edge  302 ′ of antenna ground  302 ′. Optional electrical component  322  (e.g., a fixed or tunable capacitor) may be coupled between end  321  of arm  304  and ground  302  to help tune the frequency response of arm  304  and antenna  204 . 
     The relatively long size of arm  304  allows arm  304  to exhibit a resonance in low band LB. Accordingly, arm  304  may sometimes be referred to as a low band arm in antenna resonating element  300 . Arm  304  is also preferably configured so that a harmonic resonance (e.g., a second or higher order harmonic) lies within band HB. Because arm  304  exhibits a resonance in band HB as well as band LB, arm  304  may sometimes be referred to as a high band arm or a low and high band arm. The relatively short length of arm  310  allows arm  310  to exhibit an antenna resonance in upper band TB. Arm  310  is therefore sometimes referred to as an upper band arm. Arm  312  has a length that lies between the length of arm  304  and the length of arm  310 . Arm  312  may support an antenna resonance in middle band MB and may therefore sometimes be referred to as a middle band arm of antenna resonating element  300 . The size of arms  312 ,  304 , and  314  can be independently configured to optimize performance in each of the multiple communications bands covered by antenna  204 . 
     Antenna  204  may have a return path (sometimes referred to as a short circuit path) such as return path  306  that couples the resonating element to ground. As shown in  FIG. 4 , return path  306  may be coupled in parallel with the antenna feed formed form terminals  218  and  220  across dielectric opening (gap)  316  between resonating element arm  304  and antenna ground  302 . Middle band arm  314  may be coupled to positive antenna feed terminal  218  and the other portions of antenna resonating element  300  by path (conductive line)  318 . Path  318  may cross return path  306  without touching path  306  and may therefore sometimes be referred to as a crossover path or crossover line. As shown in  FIG. 4 , crossover path  318  may be angled at a non-zero angle with respect to return path  306  (i.e., crossover path  318  may cross over return path  306  at a nonzero, non-perpendicular angle relative to the dimension along which return path extends). Use of this type of diagonal crossover arrangement for path  318  may help to reduce electromagnetic coupling between path  318  and return path  306 . The use of path  318  to couple middle band arm  314  directly to positive antenna feed terminal  218  without passing through arm  304  helps decouple arms  304  and  314  and therefore helps decouple the high band and middle band operating modes of antenna  204 , allowing independent optimization of the portions of antenna  204  associated with high band and middle band performance. 
     A graph in which antenna performance (i.e., standing wave ratio SWR) for antenna  204  has been plotted as a function of operating frequency f is shown in  FIG. 5 . As shown in  FIG. 5 , antenna  204  may exhibit four resonances, including low band resonance LB centered on frequency f 1 , middle band resonance MB centered on frequency f 2 , high band resonance HB centered on frequency f 3 , and upper band resonance UB centered on frequency f 4 . Because middle band arm  314  of antenna  204  is separate from high band arm  304 , the middle band and high band modes of antenna  204  are substantially independent. This helps increase the bandwidth of the antenna resonances for bands MB and HB and allows independent adjustment of the positions of center frequencies f 2  and f 3 . 
       FIG. 6  is a perspective view of illustrative structures that may be used in implementing antenna  204  of  FIG. 5 . In the example of  FIG. 6 , antenna  204  has been formed from conductive structure that include metal traces on dielectric support structure  320  (e.g., a flexible printed circuit mounted on a plastic carrier in a curved shape or other suitable shape, a plastic carrier for supporting metal traces, etc.). Component  322  may be a capacitor or other component that couples tip portion  321  of resonating element arm  304  to ground  302 . 
     Arm  304  may be formed from metal traces on substrate  320  and may have an elongated shape that extends along longitudinal axis  330 . Arm  310  may be formed from metal traces on carrier  320  (e.g., part of the same patterned metal layer that forms arm  304 ) and may have an elongated shape that extends along longitudinal axis  332  in parallel with arm  304 . Middle band arm  314  may extend along line  334 , perpendicular to arm  304  and perpendicular to arm  310 . Substrate  320  may have a curved shape or other suitable shape and line  334  may bend by a corresponding amount (if desired). Other shapes for substrate  320  may be used, if desired. 
     Crossover path  318  may extend along an axis that lies at a non-zero and non-perpendicular angle with respect to the axis along which return path  306  extends. The metal traces that form middle band arm  314  may be patterned portions of the same metal trace layer on substrate  320  that is used in forming arms  304  and  310 . Return path  306  and crossover path  318  may also be formed from metal traces on substrate  320 . Antenna ground  302  may be formed form portions of housing  12  (e.g., metal housing portions) and/or printed circuit board traces or other conductive structures in device  10 . 
       FIG. 7  is a diagram of antenna  204  of  FIG. 6  showing an illustrative current distribution that may be established when operating antenna  204  in a low band mode to cover low band LB at frequency f 1  . As illustrated by currents  336 , current primarily flows within low band arm  304  and ground  302  during operation of antenna  204  in the low band mode. 
       FIG. 8  is a diagram of antenna  204  of  FIG. 6  showing an illustrative current distribution that may be established when operating antenna  204  in a middle band mode to cover middle band MB at frequency f 2 . As illustrated by currents  338 , current primarily flows within middle band arm  314  and ground  302  during operation of antenna  204  in the middle band mode. 
       FIG. 9  is a diagram of antenna  204  of  FIG. 6  showing an illustrative current distribution that may be established when operating antenna  204  in a high band mode to cover high band HB at frequency f 3 . As illustrated by currents  340 , current primarily flows within low and high band arm  304  and ground  302  (e.g., in a second order or higher harmonic pattern) during operation of antenna  204  in the high band mode. 
       FIG. 10  is a diagram of antenna  204  of  FIG. 6  showing an illustrative current distribution that may be established when operating antenna  204  in an upper band mode to cover upper band TB at frequency f 4 . As illustrated by currents  342 , current primarily flows within upper band arm  310  and ground  302  during operation of antenna  204  in the upper band mode. 
     When upper band TB is significantly higher in frequency than lower band LB, arm  310  will generally be significantly shorter than arm  304 . The difference in size and resonant frequency between arms  304  and  310  allows arm  310  and arm  304  to be located on the same side of the antenna feed without producing interference between arms  304  and  310 . As shown in  FIG. 10 , this lack of interference allows arm  310  to be located in the space between arm  304  and ground  302 , which helps minimize the overall size of antenna  204 . 
       FIG. 11  is a cross-sectional side view of antenna structures  204 . As shown in  FIG. 11 , antenna structures  204  may be formed from metal traces on flexible printed circuit substrate  320  (e.g., a dielectric substrate layer such as a flexible printed circuit substrate formed from one or more polymer layers such as polyimide layers). Metal traces on substrate  320  may be used to form proximity sensor electrodes such as electrode  344 . Electrode  344  may be formed form metal that is patterned identically or similarly to underlying metal in traces that make up antenna resonating element  300 , thereby avoiding a situation in which the metal of electrode  344  adversely affects antenna performance of antenna resonating element  300 . Electrode  344  may be electromagnetically coupled to other portions of antenna structures  204  and may therefore sometimes be considered to form a part of antenna structures  204 . 
     Antenna resonating element  300  may be formed from multiple layers of metal traces on substrate  320  such as metal  300 - 1 , metal  300 - 2 , and metal  300 - 3 . Metal  300 - 1  and metal  300 - 3  may be metal traces formed on one or more of the dielectric layers in substrate  320  (e.g., metal traces formed by photolithography or other suitable patterning techniques). Metal structures  300 - 2  may be vias or other vertical structures that interconnect metal traces in different layers of flexible printed circuit substrate  320 . As an example, metal  300 - 1  may be used to form structures such as arms  304  and  310 , path  308 , and return path  306 , metal  300 - 3  may be used in forming crossover path  318  and middle band arm  314 , and metal  300 - 2  may be used in forming a connection (i.e., a via) between layers  300 - 1  and  300 - 3  at positive antenna feed terminal  218 . In this type of configuration, metal in layer  300 - 3  that is associated with crossover path  318  may pass over metal in layer  300 - 1  that is associated with return path  306  (e.g., using a diagonal path configuration in which path  318  extends along an axis that is oriented at a non-zero and non-perpendicular angle with respect to the axis along which return path  306  extends). 
     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: 20130515
Publication Date: 20160209
Grant Date: 20160209
Priority Date: 20130515
Inventors: VAZQUEZ ENRIQUE AYALA
SAMARDZIJA MIROSLAV
YARGA SALIH
SCHLUB ROBERT W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/38", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 51895369