PATENT DOCUMENT

Publication Number: US-9496608-B2
Application Number: US-201313864968-A
Country: US
Kind Code: B2

Title: Tunable multiband antenna with passive and active circuitry

Abstract:
An electronic device may have an antenna for providing coverage in wireless communications bands of interest such as a low frequency communications band and a high frequency communications band. The antenna may have an antenna ground and an antenna resonating element. The antenna resonating element may have a high band arm that contributes to a first high band resonance in the high band and may have a low band arm that exhibits a low band resonance in the low band. A passive filter that is coupled between first and second portions of the antenna resonating element may be configured to exhibit a short circuit impedance associated with a bypass path that allows the antenna resonating element to contribute to a second high band resonance in the high band.

Claims:
What is claimed is: 
     
       1. An antenna, comprising:
 an inverted-F antenna resonating element having a low band arm and a high band arm, wherein the high band arm has a bend and the low band arm has first, second, and third portions, the first portion extends parallel to the second portion, and the third portion extends between the first and second portions and perpendicular to the first and second portions;
 an antenna ground, wherein the low band arm and the antenna ground are configured to resonate in a low communications band and the high band arm and the antenna ground are configured to resonate in a first high communications band; 
 an antenna feed having a first feed terminal coupled to the inverted-F antenna resonating element and a second feed terminal coupled to the antenna ground; 
 a short circuit path coupled between the inverted-F antenna resonating element and the antenna ground, wherein the first portion of the low band arm and the high band arm extend from opposing sides of the short circuit path; 
 a filter coupled between the first portion of the low band arm and the second portion of the low band arm, wherein the filter is configured to form a short circuit between the first and second portions of the low band arm in a second high communications band, the short circuit forms a path length that is shorter than the low band arm, and the filter is configured to form an open circuit in the low communications band; and 
 a tunable component coupled between the second portion of the low band arm and the antenna ground, wherein the tunable component is configured tune the low communications band at which the low band arm and the antenna ground resonate. 
 
 
     
     
       2. The antenna defined in  claim 1  wherein the tunable component comprises an adjustable inductor. 
     
     
       3. The antenna defined in  claim 2  wherein the adjustable inductor comprises at least one inductor and switching circuitry that selectively switches the inductor into and out of use. 
     
     
       4. The antenna defined in  claim 2  wherein the adjustable inductor comprises switching circuitry and first and second inductors and wherein the switching circuitry is configured to selectively place the adjustable inductor in a first state in which the first inductor is switched into use, a second state in which the second inductor is switched into use, and a third state in which the first and second inductors are switched out of use. 
     
     
       5. The antenna defined in  claim 4  in which the filter comprises a passive filter. 
     
     
       6. The antenna defined in  claim 5  in which the filter comprises an inductor and capacitor coupled in parallel. 
     
     
       7. The antenna defined in  claim 1  wherein the filter comprises a passive filter that includes at least one inductor. 
     
     
       8. The antenna defined in  claim 7  wherein the filter further includes at least one capacitor. 
     
     
       9. The antenna defined in  claim 1  wherein the low band arm of the inverted-F antenna resonating element has a first bend between the first and third portions and a second bend between the third and second portions. 
     
     
       10. The antenna defined in  claim 1  wherein the inverted-F antenna resonating element comprises metal traces on a dielectric carrier. 
     
     
       11. The antenna defined in  claim 1  wherein the first and second high communications bands are configured to handle cellular telephone communications. 
     
     
       12. An electronic device, comprising:
 a metal housing having an opening; 
 an antenna window in the opening; 
 an antenna ground formed at least partly from the metal housing; 
 a plastic carrier adjacent to the opening; 
 an antenna resonating element formed from metal structures on the plastic carrier; 
 a short circuit path coupled between the antenna resonating element and the antenna ground; 
 a first antenna feed terminal coupled to the antenna ground; 
 a second antenna feed terminal coupled to the antenna resonating element, wherein the antenna resonating element has a first arm and a second arm, the first arm and the antenna ground are configured to exhibit a low band antenna resonance, the second arm and the antenna ground are configured to exhibit a high band antenna resonance; and 
 a passive filter that bridges an opening between a first portion of the first arm and a second portion of the first arm, wherein the first portion of the first arm extends parallel to the second portion of the first arm, the first and second portions of the first arm are coupled together by a third portion of the first arm that extends perpendicular to the first and second portions, the second arm and the first portion of the first arm extend from opposing sides of the short circuit path, and the passive filter forms a path length that is shorter than the first arm. 
 
     
     
       13. The electronic device defined in  claim 12  further comprising a tunable component coupled between the second portion of first arm and the antenna ground. 
     
     
       14. The electronic device defined in  claim 13  wherein the tunable component comprises an adjustable inductor and wherein the electronic device further comprises control circuitry that controls the adjustable inductor to tune the low band antenna resonance. 
     
     
       15. The electronic device defined in a  claim 14  wherein the passive filter comprises components configured to exhibit a short circuit impedance at a frequency within the high band resonance. 
     
     
       16. The electronic device defined in  claim 15  further comprising:
 a display cover layer having a portion that overlaps that antenna resonating element, wherein the antenna resonating element is configured to receive radio-frequency signals through the antenna window and the portion of the display cover layer that overlaps the antenna resonating element. 
 
     
     
       17. The electronic device defined in  claim 12  wherein the antenna comprises an inverted-F antenna and wherein the antenna resonating element comprises metal traces on the plastic carrier. 
     
     
       18. An antenna comprising:
 an antenna ground; 
 an antenna resonating element having a first arm and a second arm, wherein the antenna ground and the first arm are configured to resonate in a low frequency band, the antenna ground and the second arm are configured to resonate in a first high frequency band; 
 an antenna feed having a first feed terminal coupled to the antenna ground and a second feed terminal coupled to the antenna resonating element; 
 a short circuit path coupled between the antenna ground and the antenna resonating element; 
 a passive filter coupled between a first portion of the first arm and a second portion of the first arm, wherein the passive filter forms a short circuit that creates a path length that is shorter than the first arm at frequencies in a second high frequency band that is greater than the first high frequency band and forms an open circuit for at least some frequencies other than the frequencies in the second high frequency band; and 
 a dielectric carrier having a planar surface, wherein at least some of the first and second portions of the first arm, the second arm, and the short circuit path are formed from metal traces on the planar surface, and the short circuit path is interposed between the second arm and the second portion of the first arm on the planar surface. 
 
     
     
       19. The antenna defined in  claim 18  wherein the first and second portions of the first arm are coupled by a bent portion of the antenna resonating element and wherein the antenna further comprises an actively tuned tunable component coupled to the second portion. 
     
     
       20. The antenna defined in  claim 19  wherein the actively tuned tunable component comprises a tunable inductor having a terminal coupled to the antenna ground and wherein the antenna resonating element comprises an inverted-F antenna resonating element. 
     
     
       21. The antenna defined in  claim 18 , wherein the first portion extends parallel to the second portion and the first arm comprises a third portion on the planar surface that extends perpendicular to the first and second portions. 
     
     
       22. The antenna defined in  claim 18 , wherein the dielectric carrier has first, second, third, fourth, fifth, and sixth surfaces, the planar surface is the first surface, the second arm includes metal traces on the first and third surfaces, the first arm includes metal traces on the first, fourth, sixth, second, and fifth surfaces, the second portion of the first arm is formed on at least the first and second surfaces, and the first and second feed terminals are located on the second surface.

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 have wireless communications circuitry to communicate using cellular telephone bands and to support communications with satellite navigation systems and wireless local area networks. 
     It can be difficult to incorporate antennas and other electrical components successfully into an electronic device. Some electronic devices are manufactured with small form factors, so space for components is limited. In many electronic devices, the presence of conductive structures can influence the performance of electronic components, further restricting potential mounting arrangements for components such as antennas. 
     It would therefore be desirable to be able to provide improved electronic device antennas. 
     SUMMARY 
     An electronic device may have an antenna. Antenna structures for the antenna may be formed from patterned metal structures on a dielectric carrier. The dielectric carrier may be a plastic carrier having a shape with sides that create a three-dimensional layout for the antenna structures. 
     The antenna may be configured to provide coverage in wireless communications bands such as a low frequency communications band and a high frequency communications band. The antenna may have an antenna ground formed from structures such as conductive electronic device housing structures and an antenna resonating element such as an inverted-F antenna resonating element formed from the patterned metal structures on the plastic carrier. 
     The antenna resonating element may have a high band arm that contributes to a first high band resonance in the high band and may have a low band arm that gives rise to a low band resonance in the low band. A passive filter that is coupled between first and second portions of the low band arm in the antenna resonating element may be configured to exhibit a short circuit impedance at frequencies associated with a second high band resonance in the high band. The short circuit forms a bypass path that shorts together the first and second portions at frequencies in the second high band resonance. In this configuration, the first and second portions of the antenna resonating element form an antenna structure that contributes to the second high band resonance in the high band. 
     The low band resonance may be tuned using a tunable component. The tunable component may be a tunable inductor that is actively tuned during operation of the antenna and electronic device. The tunable inductor may be coupled between the second portion of the antenna resonating element and the antenna ground. Adjustments to the tunable inductor may be used to tune the low band resonance so that the entire low band is covered by the antenna. 
     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 diagram of antenna structures and associated circuitry in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 4  is a circuit diagram of an illustrative tunable component based on a series-connected inductor and switch in accordance with an embodiment of the present invention. 
         FIG. 5  is a circuit diagram of an illustrative tunable component based on a series-connected capacitor and switch in accordance with an embodiment of the present invention. 
         FIG. 6  is a circuit diagram of an illustrative tunable component based on a parallel inductor and bypass switch in accordance with an embodiment of the present invention. 
         FIG. 7  is a circuit diagram of an illustrative tunable component based on a parallel capacitor and bypass switch in accordance with an embodiment of the present invention. 
         FIG. 8  is a circuit diagram of an illustrative tunable component based on a variable capacitor in accordance with an embodiment of the present invention. 
         FIG. 9  is a circuit diagram of an illustrative tunable component based on a variable inductor in accordance with an embodiment of the present invention. 
         FIG. 10  is a circuit diagram of an illustrative tunable component based on multiple components such as fixed and tunable components coupled in series and in parallel in accordance with an embodiment of the present invention. 
         FIG. 11  is a diagram of an antenna in accordance with an embodiment of the present invention. 
         FIG. 12  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of frequency in low and high communications bands in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional side view of an illustrative electronic device having an antenna in accordance with an embodiment of the present invention. 
         FIG. 14  is a perspective view of an illustrative antenna having a three-dimensional carrier such as a box-shaped carrier with six sides in accordance with an embodiment of the present invention. 
         FIG. 15  is a top view of unwrapped metal structures from the illustrative antenna of  FIG. 14  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with antennas, and other electronic components. An illustrative electronic device in which electronic components such as antenna structures may be used 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 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 cover glass). 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 curved portions that match the shape of curved housing edges  12 A. Antenna window  58  may also have planar walls, if desired. 
     A schematic diagram of an illustrative configuration that may be used for electronic device  10  is shown in  FIG. 3 . As shown in  FIG. 3 , 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 sensors and status indicators such as an ambient light sensor, a proximity 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  38  for handling wireless communications in cellular telephone bands such as the bands in the range of 700 MHz to 2.7 GHz (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, antennas that cover more than two bands, or other suitable antennas. Configurations in which at least one antenna in device  10  is formed from an inverted-F antenna structure such as a dual band inverted-F antenna are sometimes described herein as an example. 
     To provide antenna structures  204  with the ability to cover communications frequencies of interest, antenna structures  204  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). 
     If desired, antenna structures  204  may be provided with adjustable circuits such as tunable circuitry  208 . Tunable circuitry  208  may be controlled by control signals from control circuitry  29 . For example, control circuitry  29  may supply control signals to tunable circuitry  208  via control path  210  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). 
     Passive filter circuitry in antenna structures  204  may help antenna structures  204  exhibit antenna resonances in communications bands of interest (e.g., passive filter circuitry in antenna structures  204  may short together different portions of antenna structures  204  and/or may form open circuits or pathways of other impedances between different portions of antenna structures  204  to ensure that desired antenna resonances are produced). 
     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. 3  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 passive filter circuitry in antenna structures  204  and tunable circuitry  208  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. 3  is merely illustrative. 
     Tunable circuitry  208  may be formed from one or more tunable circuits such as circuits based on capacitors, resistors, inductors, and switches. Tunable circuitry  208  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, tunable circuitry  208  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 ). Filter circuitry in antenna structures  204  such as passive filter circuitry may also be formed using these types of arrangement. 
       FIGS. 4, 5, 6, 7, 8, 9, and 10  are diagrams of illustrative tunable circuits of the types that may be used in implementing some or all of tunable antenna circuitry  208  of  FIG. 3 . Tunable antenna circuits  208  may have two or more terminals. For example, tunable antenna components  208  may each have respective first and second terminals  228  and  230 . Terminals  228  and  230  may be coupled to conductive structures at different respective locations within antenna structures  204 . During operation of device  10 , control circuitry  29  may issue commands on path  210  to adjust switches, variable components, and other adjustable circuitry in tunable circuitry  208 , thereby tuning antenna structures  204 . 
     As shown  FIG. 4 , tunable circuitry  208  may include a series-coupled inductor and switch such as inductor  224  and switch  226 . Inductor  224  and switch  226  may be connected in series between terminals  228  and  230 . Switch  226  may be closed to switch inductor  224  into use and may be opened when it is desired to remove inductor  224  from use in antenna structures  204 . There is one inductor  224  in tunable circuitry  208 , but two or more inductors may be switched into and out of use by switch  226  in component  208  if desired. 
     As shown in  FIG. 5 , tunable circuitry  208  may include a series-coupled capacitor and switch such as capacitor  232  and switch  234 . Capacitor  232  and switch  234  may be connected in series between terminals  228  and  230 . Switch  234  may be closed to switch capacitor  232  into use and may be opened when it is desired to remove capacitor  232  from use in antenna structures  204 . 
     Tunable components  208  may, if desired, use bypassable components. As shown in  FIG. 6 , for example, tunable circuit  208  may include an inductor such as inductor  236  that is coupled in parallel with a switch such as switch  238  between terminals  228  and  230 . Switch  238  may be closed when it is desired to bypass inductor  236 . As shown in  FIG. 7 , tunable circuit  208  may include a capacitor such as capacitor  240  that is coupled in parallel with a switch such as switch  242  between terminals  228  and  230 . Switch  242  may be closed when it is desired to bypass capacitor  240 . 
     Variable components such as varactors, variable inductors, and variable resistors may be used in tunable circuitry  208  to provide continuously adjustable component values.  FIG. 8  is a diagram of tunable circuitry  208  in a configuration based on varactor  244 .  FIG. 9  shows how variable inductor  246  may be used to form tunable circuitry  208 . Variable components may, if desired, be coupled in series or parallel with switches. 
     Switches in tunable circuitry  208  may be based on diodes, transistors, microelectromechanical systems (MEMS) devices, or other switching circuitry. 
     As shown in  FIG. 10 , tunable circuitry  208  may include multiple components  248 . Components  248  may be coupled in series and/or in parallel between terminals  228  and  230 . Each component  248  in  FIG. 10  may be implemented using one or more of the circuits of  FIGS. 4, 5, 6, 7, 8 , and  9 , switches, variable components, bypassable components, or other tunable components. As an example, tunable component  208  may be implemented using two or more or three or more adjustable inductors (e.g., inductors implemented using circuit  208  of  FIG. 4 , circuit  208  of  FIG. 6 , or circuit  208  of  FIG. 9  that are coupled in parallel between terminals  228  and  230 ). Multiple switches may be used in switching a desired inductor (or other component) into use or switching circuitry having one or more switches with multiple positions may be used in switching a desired inductor or inductors (or other components) into use. 
       FIG. 11  is a diagram of an illustrative antenna configuration that may be used for antenna structures  204  in device  10 . In the  FIG. 11  example, antenna structures  204  are implemented using a dual-arm inverted-F antenna (antenna  204 ) having antenna resonating element  252  and antenna ground  250 . Antenna ground  250  may be formed from metal electronic device housing structures  12 , may be formed from patterned metal traces on a dielectric support structure (e.g., a plastic carrier, printed circuit substrate, glass, ceramic, etc.), or may be formed from other conductive structures in device  10 . Antenna resonating element  252  may be formed from patterned metal traces on a plastic carrier, may be formed from patterned metal traces on a flexible printed circuit (e.g., a printed circuit formed from a layer of polyimide or a sheet of other flexible polymer), may be formed from patterned metal traces on a rigid printed circuit board substrate (e.g. a printed circuit board substrate formed from fiberglass-filled epoxy), may be formed from stamped metal foil or wires, or may be formed from other conductive structures. 
     Antenna  204  has main resonating element structure  254 . Main resonating element structure  254  may be formed from an elongated conductive structure (e.g., a strip of metal). Antenna feed path  256  and short circuit path SC may be coupled in parallel between main resonating element structures  254  and ground  250 . 
     Main resonating element structure  254  may have multiple arms. For example, structure  254  may have high band arm HB-1. High band arm HB-1 may be associated with a first high band resonance contribution to a high-frequency communications band. Structure  254  may also have low band arm LB for supporting an antenna resonance at a lower frequency than the first high band resonance frequency (i.e., in a low frequency band LB). 
     Main resonating element structure  254  (i.e., low band arm LB) may have a bend such as bend  262 . The bent portion of main resonating element  252  couples portion  254  to tip portion  264 , so that tip portion  264  of resonating element  252  runs parallel to main resonating element portion  254  of resonating element  252 . Tip segment  264  may lie between main portion (segment)  254  and antenna ground  250 . 
     Tunable element  208  may be coupled between tip segment  264  of antenna resonating element  252  and antenna ground  250 . During operation of antenna  204 , tunable element  208  may be adjusted to switch inductor L1 (having a first inductance value) or inductor L2 (having a second inductance value) into use. By adjusting whether inductor L1 or inductor L2 couples antenna segment  264  to antenna ground  250  or whether both inductors L1 and L2 are switched out of use so that an infinite impedance (open circuit) is formed by tunable element  208  so that segment  264  is isolated from ground  250 , control circuitry  29  can adjust low band performance for antenna  204  (e.g., control circuitry  29  can make adjustments to tunable element  208  to tune a low band antenna resonance for antenna  204 ). 
     The main segment of antenna resonating element  252  may be coupled to folded tip segment  264  of antenna resonating element  252  using filter circuitry F. Filter F may include components such as inductor  258  and capacitor  260 . The components of filter F such as inductor  258  and capacitor  260  may form a resonant circuit having a relatively low impedance (i.e., a short circuit impedance) at frequencies associated with a second high band resonance HB-2 in a high band HB and having a relatively high impedance (open circuit impedance) at other frequencies such as those associated with operation in low band LB. 
     At high band operating frequencies, filter F may form a short circuit that shorts main portion (segment)  254  of antenna resonating element  252  to tip portion  264  of antenna resonating element  252 , thereby allowing currents in antenna  204  to flow within high band path HB-2 of resonating element  252 , bypassing the rest of low band arm LB near bend  262 . Filter F therefore allows path  268  to serve as a bypass path in antenna resonating element  252  at high frequencies HB-2. At low frequencies associated with operation of antenna  204  in low band LB, currents in antenna  204  may flow within low band arm LB without passing through bypass path  268 . 
     The configuration of  FIG. 11  in which part of the antenna resonating element is bridged with a passive filter and in which a tip portion of the antenna resonating element is coupled to ground by a tunable component such as an adjustable inductor allows a dual-arm inverted-F antenna to exhibit three antenna resonances. Antenna resonance HB-1 forms a first contribution to high band resonance HB and is associated with the current path for high band arm HB-1. A second high band resonance HB-2 forms a second contribution to high band resonance HB and is associate with the current path through filter F (i.e., bypass path  268 ). Resonances HB-1 and HB-2 may overlap to form a combined overall high band resonance HB for antenna  204 . 
     A low band resonance, which is tuned by adjustment of the inductance between resonating element  252  and antenna ground  250 , may be associated with low band path LB. 
       FIG. 12  is a graph in which antenna performance (i.e., standing wave ratio SWR) has been plotted as a function of frequency f for an antenna such as antenna  204  of  FIG. 11 . As shown in  FIG. 12 , antenna  204  may exhibit coverage in lower communications band LB and in higher communications band HB. Bands LB and HB may be associated with cellular telephone traffic, wireless local area network traffic, and/or satellite navigation system signals (as examples). For example, low band LB may cover cellular telephone communications at frequencies from 700 MHz to 960 MHz and high band HB may cover cellular telephone communications and/or satellite navigation system signals at frequencies from 1560 MHz to 2170 MHz. Other communications bands may be covered using antenna  204  if desired. The frequency coverage of the graph of  FIG. 12  is merely illustrative. 
     Coverage for high band HB may be achieved using passive filter circuitry to form multiple antenna resonating element paths within antenna  204 . For example, resonance  276  may be formed using high band arm HB-1 and resonance  278  may be formed using high band bypass path HB-2 in low band path LB. Coverage across all of low band LB may be achieved by adjusting the inductance of tunable inductor  208  to tune the low band resonance of antenna  204 . Antenna  204  may, for example, exhibit antenna resonance  270  when inductor  208  is placed in a first state in which inductors L1 and L2 are switched out of use by switching circuitry  266  of tunable inductor  208 . In this first state for tunable inductor  208 , tunable inductor  208  may form an open circuit (i.e., the inductance of inductor  208  may effectively be infinite). Antenna  204  may exhibit antenna resonance  272  when inductor  208  is placed in a second state in which inductor L1 is switched into use and may exhibit antenna resonance  274  when inductor  208  is placed in a third state in which inductor  208  is placed in a third state in which inductor L2 is switched into use. 
     With the arrangement of  FIG. 2 , low band coverage is achieved using active tuning of tunable element  208  and high band coverage is achieved using passive filter tuning with frequency-dependent filter F. Configurations in which tunable inductor  208  can be adjusted to exhibit a different number of inductances and/or filter circuitry F may be used in forming different numbers of bypass paths may be used if desired. The example of  FIGS. 11 and 12  is merely illustrative. 
     A cross-sectional view of device  10  taken along line  1300  of  FIG. 2  and viewed in direction  1302  is shown in  FIG. 13 . As shown in  FIG. 13 , 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 such as positive antenna feed terminal  218  of  FIG. 3  and a ground signal conductor that is coupled to a ground antenna feed terminal such as ground antenna feed terminal  220  of  FIG. 3  (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, 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.). 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 panel module  64 . The structures in display panel  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., panel  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 such as control circuitry  29  of  FIG. 3 . 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  206  of  FIG. 3  (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 . 
       FIG. 14  shows how conductive structures for antenna structures  204  may be supported by a dielectric carrier. As shown in  FIG. 14 , antenna structures  204  may have conductive structures  280  such as metal structures that are supported by dielectric carrier  282 . Conductive structures  280  may be metal traces that are formed on the surface of dielectric carrier  282  (e.g., using laser-based deposition techniques, physical vapor deposition techniques, electrochemical deposition, etc.), may be metal traces on a flexible printed circuit that is mounted on dielectric carrier  282 , may be other metal structures supported by carrier  282  (e.g., patterned metal foil), or may be other conductive structures. 
     Dielectric carrier  282  may be formed from a dielectric material such as glass, ceramic, or plastic. As an example, dielectric carrier  282  may be formed from plastic parts that are molded and/or machined into a desired shape such as the illustrative rectangular prism shape (rectangular box shape) of  FIG. 14 . If desired, other dielectric carrier shapes (e.g., box or prism shapes with different numbers of sides or other three-dimensional carrier shapes) may be used for antenna structures  204 . The example of  FIG. 14  is merely illustrative. 
     As shown in the  FIG. 14  configuration, dielectric carrier  268  may have six sides: side I, side II, side III, side IV, side V, and side VI. Metal traces  280  may cover at least some of each of the six sides of carrier  268  or may cover a subset of the sides of carrier  268  so as to allow antenna structures  204  to efficiently use a limited volume within device  10  to form an antenna with resonances at desired frequencies. Openings in metal traces  280  (e.g., slot-shaped openings, etc.) may be used to help control the flow of currents in metal traces  280  and thereby adjust antenna performance. If desired, carrier  282  may have other numbers of sides (e.g., four sides, five sides, more than two sides, fewer than six sides, four or more sides, five or more sides, shapes with curved surfaces that take the place of one or more of the sides of  FIG. 14 , etc.). The use of six planar sides for carrier  282  is merely illustrative. 
       FIG. 15  is a diagram showing an illustrative pattern that may be used for metal structures  280 . In the arrangement of  FIG. 15 , structures  280  have been unwrapped from carrier  282  and laid out flat. Dashed lines  284  represent fold lines (i.e., axes along which structures  280  are folded when wrapped around carrier  282  to form antenna structures  204  of  FIG. 14 ). Openings such as openings  286  are used to form a desired pattern for conductive structures  280 . Metal strip portion SC of metal structures  270  may serve as short circuit SC of  FIG. 11 . Dashed line path HB-1 in metal structures  280  shows how portions of metal structures  280  may serve as high band resonating element arm HB-1 of  FIG. 11 . Dashed line path HB-2 though filter F shows how portions of metal structures  280  and filter F may serve as high band resonating element path HB-2 of  FIG. 11 . Dashed line LB in metal structures  280  show how portions of metal structures  280  may also serve as low band resonating element arm LB of  FIG. 11 . Transmission line  212  ( FIG. 3 ) may be coupled to antenna feed terminals  218  and  220 . Other patterns may be used for metal structures  280  if desired. The configuration of  FIG. 15  in which metal structures  280  form a three-dimensional wrapped metal sheet surrounding carrier  282  of  FIG. 14  to implement an inverted-F antenna of the type shown in  FIG. 11  is merely illustrative. 
     To provide antenna structures  204  with the ability to be tuned to cover different desired communications bands during use, antenna structures  204  may be provided with passive filter circuitry F and active tunable circuitry  208 . As an example, terminal  228  of tunable circuitry  208  may be coupled to a portion of conductive structures  280  and terminal  230  of tunable circuitry  208  may be coupled to antenna ground  250 . In general, the locations at which terminals  228  and  230  are coupled to antenna  204  may be positioned at any points on metal structures  280  that provide a desired amount of antenna response tuning. The illustrative coupling locations for terminals  228  and  230  are merely illustrative. 
     If desired, dielectric carrier  282  may be formed from a structure that contains one or more cavities (i.e., dielectric carrier  282  may be hollow). Cavities in carrier  282  may be filled with air, porous material with a low dielectric constant, foam, or other materials. Dielectric carrier  282  may have a body that is covered with a lid or other configurations. 
     Conductive structures  280  may be formed from patterned metal traces formed directly on the surface of dielectric carrier  282 . The pattern of metal used in forming structures  280  may be created by photolithographic patterning, using laser direct structuring (LDS) techniques in which applied laser light (or other activation mechanism) is used to selectively activate desired surface regions on a plastic carrier that are subsequently electroplated or otherwise coated with metal to form patterned metal structures  280 , or molded interconnect device (MID) techniques in which multiple shots of plastic (some metal-attracting and some metal-repelling) are used to create desired metal patterns  280  following electroplating or other metal coating operations. 
     If desired, a flexible printed circuit may be provided with metal traces such as metal traces  280 . Adhesive, solder, welds, screws, or other fastening arrangements may be used to attach flexible printed circuit to dielectric carrier  282 . 
     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: 20130417
Publication Date: 20161115
Grant Date: 20161115
Priority Date: 20130417
Inventors: JIANG YI
YONG SIWEN
COUTTS GORDON
ZHANG LIJUN
LI QINGXIANG
SCHLUB ROBERT W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q5/392", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/22", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/245", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/245", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/22", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 50771592