PATENT DOCUMENT

Publication Number: US-9972891-B2
Application Number: US-201514819280-A
Country: US
Kind Code: B2

Title: Electronic device antenna with isolation mode

Abstract:
An electronic device may have wireless circuitry with antennas. An antenna resonating element arm for a given antenna may be formed from metal structures supported by a plastic carrier. The antenna resonating element arm may be coupled to switching circuitry to isolate the antenna resonating element arm when the antenna resonating element arm is not being used to handle communications in a communications band. The electronic device may have a metal housing. A slot may separate a peripheral portion of the housing such as a sidewall portion from a planar rear portion. The sidewall portion and the planar rear portion may form an additional antenna that operates at communications frequencies outside of the communications band handled by the given antenna. A parasitic antenna resonating element arm may be formed in the slot to enhance the frequency response of the additional antenna.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing having a peripheral conductive structure; 
 a first antenna that has a first resonating element arm formed from the peripheral conductive structure, that has an antenna ground that is separated from the first antenna resonating element arm by a slot that runs parallel at least one edge of the housing, and that has a first antenna feed; 
 a second antenna formed from a second resonating element arm and the antenna ground, wherein the second antenna has a second antenna feed and the peripheral conductive structure forms a parasitic antenna resonating element for the second antenna; 
 a first transmission line coupled to the first antenna feed; 
 switching circuitry; and 
 a second transmission line coupled to the second antenna feed by the switching circuitry. 
 
     
     
       2. The electronic device defined in  claim 1  further comprising control circuitry that is configured to place the switching circuitry in a freespace mode of operation in which the second transmission line transmits and receives antenna signals for the second antenna through the switching circuitry. 
     
     
       3. The electronic device defined in  claim 2  wherein the control circuitry is further configured to place the switching circuitry in an isolation mode of operation in which the second antenna is electrically isolated from the second transmission line. 
     
     
       4. The electronic device defined in  claim 3  wherein the control circuitry is further configured to place the switching circuitry in at least one additional mode of operation in which the antenna is tuned to ensure operation at a desired frequency range when gripped by a user. 
     
     
       5. The electronic device defined in  claim 3  wherein the second antenna further comprises a plastic carrier that supports the second resonating element arm. 
     
     
       6. The electronic device defined in  claim 5  further comprising a flexible printed circuit, wherein the second transmission line includes conductive lines on the flexible printed circuit. 
     
     
       7. The electronic device defined in  claim 6  further comprising an additional parasitic antenna resonating element in the slot. 
     
     
       8. The electronic device defined in  claim 7  wherein the switching circuitry is mounted on the flexible printed circuit. 
     
     
       9. The electronic device defined in  claim 3  wherein the second antenna comprises a tunable inverted-F antenna. 
     
     
       10. The electronic device defined in  claim 9  wherein the second antenna is configured to resonate in a frequency band that includes a frequency of 1400 MHz. 
     
     
       11. The electronic device defined in  claim 1  wherein the first antenna feed has a first positive antenna feed terminal coupled to the first antenna resonating element arm and wherein the second antenna feed has a second positive antenna feed terminal coupled to the second antenna resonating element arm. 
     
     
       12. The electronic device defined in  claim 1  wherein the second antenna resonating element arm has at least four segments and three right-angle bends. 
     
     
       13. An electronic device, comprising:
 a metal housing with a slot that separates the metal housing into a peripheral conductive housing structure that forms a first antenna resonating element arm and an antenna ground, wherein the first antenna resonating element arm and the antenna ground form a first antenna; 
 switching circuitry having first and second states; and 
 a second antenna coupled to the switching circuitry, wherein the second antenna includes a second antenna resonating element arm and the antenna ground, the second antenna resonating element arm is coupled to radio-frequency transceiver circuitry when the switching circuitry is in the first state, and the second antenna resonating element arm is configured to serve as a parasitic antenna resonating element for the first antenna when the switching circuitry is in the second state. 
 
     
     
       14. The electronic device defined in  claim 13  further comprising a transmission line that couples the transceiver circuitry to the switching circuitry. 
     
     
       15. The electronic device defined in  claim 14  further comprising control circuitry that is configured to adjust the switching circuitry to place the switching circuitry in a selected one of the first and second states. 
     
     
       16. The electronic device defined in  claim 15  wherein the transceiver circuitry is configured to transmit and receive antenna signals with the first antenna while the switching circuitry is in the second state. 
     
     
       17. The electronic device defined in  claim 16  further comprising a plastic carrier that supports the second antenna resonating element. 
     
     
       18. The electronic device defined in  claim 17  wherein the second antenna resonating element arm is configured to resonate at a communications band including a frequency of 1400 MHz. 
     
     
       19. An electronic device, comprising:
 a metal housing having a sidewall portion that runs along an edge of the electronic device and having a planar rear wall portion that forms a portion of a ground, wherein the sidewall portion and the planar rear wall portion are separated by a slot; 
 an antenna resonating element arm formed from a metal structure on at least two sides of a plastic carrier; 
 switching circuitry coupled to the antenna resonating element arm; and 
 transceiver circuitry coupled to the antenna resonating element arm by the switching circuitry, wherein the switching circuitry is operable in a first mode in which the switching circuitry couples the transceiver circuitry to the antenna resonating element arm and a second mode in which the switching circuitry isolates the transceiver circuitry from the antenna resonating element arm. 
 
     
     
       20. The electronic device defined in  claim 19  wherein the antenna resonating element arm serves as part of an antenna that operates in a communications band, the electronic device further comprising a parasitic antenna resonating element arm in the slot, wherein the sidewall portion, the parasitic antenna resonating element arm, and the ground form an additional antenna that operates at frequencies that are outside of the communications band. 
     
     
       21. The electronic device defined in  claim 20  wherein the antenna resonating element arm of the antenna serves as a parasitic antenna resonating element for the additional antenna at the frequencies that are outside of the communications band while the switching circuitry is operated in the second mode.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless circuitry with antennas. For example, cellular telephones, computers, and other devices often contain antennas for supporting wireless communications. 
     It can be challenging to form electronic device antenna structures with desired attributes. In some wireless devices, the presence of conductive structures such as conductive housing structures can influence antenna performance. Antenna performance may not be satisfactory if the housing structures are not configured properly and interfere with antenna operation. Device size can also affect performance. It can be difficult to achieve desired performance levels in a compact device, particularly when the compact device has conductive housing structures. 
     It would therefore be desirable to be able to provide improved wireless circuitry for electronic devices such as electronic devices that include conductive housing structures. 
     SUMMARY 
     An electronic device may have wireless circuitry with antennas. An antenna resonating element arm for an antenna may be formed from metal structures supported by a plastic carrier. The antenna resonating element arm may be coupled to a transceiver using switching circuitry. Control circuitry may be used to place the switching circuitry in either a state that couples the transceiver to the antenna or that isolates the transceiver from the antenna. When the antenna is isolated, an additional antenna may be used by the transceiver to transmit and receive wireless signals. 
     The electronic device may have a metal housing. A slot may separate a peripheral portion of the housing such as a sidewall portion from a planar rear portion. The additional antenna may be formed from the sidewall portion and the planar rear portion. The antenna and additional antenna may operate in different communications bands. A parasitic antenna resonating element arm may be formed in the slot to enhance the frequency response of this additional antenna. The antenna resonating element arm for the antenna may have multiple segments coupled at bends. The segments may include a segment that overlaps the slot and runs parallel to the slot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of illustrative circuitry in an electronic device in accordance with an embodiment. 
         FIG. 3  is a schematic diagram of illustrative wireless circuitry in accordance with an embodiment. 
         FIG. 4  is a schematic diagram of an illustrative inverted-F antenna in accordance with an embodiment. 
         FIG. 5  is a schematic diagram of an illustrative slot antenna in accordance with an embodiment of the present invention. 
         FIGS. 6 and 7  are diagrams of illustrative antenna structures that include a parasitic antenna resonating element arm embedded within an antenna slot in accordance with an embodiment. 
         FIG. 8  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency in accordance with an embodiment. 
         FIG. 9  is a diagram of a switchable antenna in accordance with an embodiment. 
         FIG. 10  is a perspective view of an illustrative antenna of the type shown in  FIG. 9  in accordance with an embodiment. 
         FIG. 11  is a perspective view of a metal antenna resonating element for the antenna of  FIG. 10  in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. 
     The wireless communications circuitry may include one more antennas. The antennas of the wireless communications circuitry can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. 
     The conductive electronic device structures may include conductive housing structures. The housing structures may include peripheral structures such as peripheral conductive structures that run around the periphery of an electronic device. The peripheral conductive structure may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, may have portions that extend upwards from an integral planar rear housing (e.g., to form vertical planar sidewalls or curved sidewalls), and/or may form other housing structures. 
     Gaps may be formed in the peripheral conductive structures that divide the peripheral conductive structures into peripheral segments. One or more of the segments may be used in forming one or more antennas for electronic device  10 . Antennas may also be formed using an antenna ground plane formed from conductive housing structures such as metal housing midplate structures and other internal device structures. Rear housing wall structures may be used in forming antenna structures such as an antenna ground. 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Device  10  may also be a set-top box, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may be mounted on the front face of device  10 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or may be insensitive to touch. The rear face of housing  12  (i.e., the face of device  10  opposing the front face of device  10 ) may have a planar housing wall. The rear housing wall may be have slots that pass entirely through the rear housing wall and that therefore separate housing wall portions (and/or sidewall portions) of housing  12  from each other. Housing  12  (e.g., the rear housing wall, sidewalls, etc.) may also have shallow grooves that do not pass entirely through housing  12 . The slots and grooves may be filled with plastic or other dielectric. If desired, portions of housing  12  that have been separated from each other (e.g., by a through slot) may be joined by internal conductive structures (e.g., sheet metal or other metal members that bridge the slot). 
     Display  14  may include pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable pixel structures. A display cover layer such as a layer of clear glass or plastic may cover the surface of display  14  or the outermost layer of display  14  may be formed from a color filter layer, thin-film transistor layer, or other display layer. Buttons such as button  24  may pass through openings in the cover layer. The cover layer may also have other openings such as an opening for speaker port  26 . 
     Housing  12  may include peripheral housing structures such as structures  16 . Structures  16  may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape with four edges, structures  16  may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges (as an example). Peripheral structures  16  or part of peripheral structures  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or that helps hold display  14  to device  10 ). Peripheral structures  16  may also, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral housing structures  16  may be formed of a conductive material such as metal and may therefore sometimes be referred to as peripheral conductive housing structures, conductive housing structures, peripheral metal structures, or a peripheral conductive housing member (as examples). Peripheral housing structures  16  may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, or more than two separate structures may be used in forming peripheral housing structures  16 . 
     It is not necessary for peripheral housing structures  16  to have a uniform cross-section. For example, the top portion of peripheral housing structures  16  may, if desired, have an inwardly protruding lip that helps hold display  14  in place. The bottom portion of peripheral housing structures  16  may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). Peripheral housing structures  16  may have substantially straight vertical sidewalls, may have sidewalls that are curved, or may have other suitable shapes. In some configurations (e.g., when peripheral housing structures  16  serve as a bezel for display  14 ), peripheral housing structures  16  may run around the lip of housing  12  (i.e., peripheral housing structures  16  may cover only the edge of housing  12  that surrounds display  14  and not the rest of the sidewalls of housing  12 ). 
     If desired, housing  12  may have a conductive rear surface. For example, housing  12  may be formed from a metal such as stainless steel or aluminum. The rear surface of housing  12  may lie in a plane that is parallel to display  14 . In configurations for device  10  in which the rear surface of housing  12  is formed from metal, it may be desirable to form parts of peripheral conductive housing structures  16  as integral portions of the housing structures forming the rear surface of housing  12 . For example, a rear housing wall of device  10  may be formed from a planar metal structure and portions of peripheral housing structures  16  on the sides of housing  12  may be formed as flat or curved vertically extending integral metal portions of the planar metal structure. Housing structures such as these may, if desired, be machined from a block of metal and/or may include multiple metal pieces that are assembled together to form housing  12 . The planar rear wall of housing  12  may have one or more, two or more, or three or more portions. 
     Display  14  may have an array of pixels that form an active area AA that displays images for a user of device  10 . An inactive border region such as inactive area IA may run along one or more of the peripheral edges of active area AA. 
     Display  14  may include conductive structures such as an array of capacitive electrodes for a touch sensor, conductive lines for addressing pixels, driver circuits, etc. Housing  12  may include internal conductive structures such as metal frame members and a planar conductive housing member (sometimes referred to as a midplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more parts that is welded or otherwise connected between opposing sides of member  16 ). Device  10  may also include conductive structures such as printed circuit boards, components mounted on printed circuit boards, and other internal conductive structures. These conductive structures, which may be used in forming a ground plane in device  10 , may be located in the center of housing  12  and may extend under active area AA of display  14 . 
     In regions  22  and  20 , openings may be formed within the conductive structures of device  10  (e.g., between peripheral conductive housing structures  16  and opposing conductive ground structures such as conductive housing midplate or rear housing wall structures, a printed circuit board, and conductive electrical components in display  14  and device  10 ). These openings, which may sometimes be referred to as gaps, may be filled with air, plastic, and other dielectrics and may be used in forming slot antenna resonating elements for one or more antennas in device  10 . 
     Conductive housing structures and other conductive structures in device  10  such as a midplate, traces on a printed circuit board, display  14 , and conductive electronic components may serve as a ground plane for the antennas in device  10 . The openings in regions  20  and  22  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, may contribute to the performance of a parasitic antenna resonating element, or may otherwise serve as part of antenna structures formed in regions  20  and  22 . If desired, the ground plane that is under active area AA of display  14  and/or other metal structures in device  10  may have portions that extend into parts of the ends of device  10  (e.g., the ground may extend towards the dielectric-filled openings in regions  20  and  22 ), thereby narrowing the slots in regions  20  and  22 . In configurations for device  10  with narrow U-shaped openings or other openings that run along the edges of device  10 , the ground plane of device  10  can be enlarged to accommodate additional electrical components (integrated circuits, sensors, etc.) 
     In general, device  10  may include any suitable number of antennas (e.g., one or more, two or more, three or more, four or more, etc.). The antennas in device  10  may be located at opposing first and second ends of an elongated device housing (e.g., at ends  20  and  22  of device  10  of  FIG. 1 ), along one or more edges of a device housing, in the center of a device housing, in other suitable locations, or in one or more of these locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral housing structures  16  may be provided with peripheral gap structures. For example, peripheral conductive housing structures  16  may be provided with one or more gaps such as gaps  18 , as shown in  FIG. 1 . The gaps in peripheral housing structures  16  may be filled with dielectric such as polymer, ceramic, glass, air, other dielectric materials, or combinations of these materials. Gaps  18  may divide peripheral housing structures  16  into one or more peripheral conductive segments. There may be, for example, two peripheral conductive segments in peripheral housing structures  16  (e.g., in an arrangement with two of gaps  18 ), three peripheral conductive segments (e.g., in an arrangement with three of gaps  18 ), four peripheral conductive segments (e.g., in an arrangement with four gaps  18 , etc.). The segments of peripheral conductive housing structures  16  that are formed in this way may form parts of antennas in device  10 . 
     If desired, openings in housing  12  such as grooves that extend partway or completely through housing  12  may extend across the width of the rear wall of housing  12  and may penetrate through the rear wall of housing  12  to divide the rear wall into different portions. These grooves may also extend into peripheral housing structures  16  and may form antenna slots, gaps  18 , and other structures in device  10 . Polymer or other dielectric may fill these grooves and other housing openings. In some situations, housing openings that form antenna slots and other structure may be filled with a dielectric such as air. 
     In a typical scenario, device  10  may have upper and lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, etc. 
     A schematic diagram showing illustrative components that may be used in device  10  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, multiple-input and multiple-output (MIMO) protocols, antenna diversity protocols, etc. 
     Input-output circuitry  30  may include input-output devices  32 . Input-output devices  32  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 devices  32  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  32  may include touch screens, displays without touch sensor capabilities, buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, position and orientation sensors (e.g., sensors such as accelerometers, gyroscopes, and compasses), capacitance sensors, proximity sensors (e.g., capacitive proximity sensors, light-based proximity sensors, etc.), fingerprint sensors (e.g., a fingerprint sensor integrated with a button such as button  24  of  FIG. 1  or a fingerprint sensor that takes the place of button  24 ), etc. 
     Input-output circuitry  30  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, transmission lines, 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 circuitry  90  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  42 . Transceiver circuitry  36  may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a low-midband from 960-1710 MHz, a midband from 1710 to 2170 MHz, and a high band from 2300 to 2700 MHz or other communications bands between 700 MHz and 2700 MHz or other suitable frequencies (as examples). Circuitry  38  may handle voice data and non-voice data. 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 60 GHz transceiver circuitry, circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. Wireless communications circuitry  34  may include global positioning system (GPS) receiver equipment such as GPS receiver circuitry  42  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. 
     As shown in  FIG. 3 , transceiver circuitry  90  in wireless circuitry  34  may be coupled to antenna structures  40  using paths such as path  92 . Wireless circuitry  34  may be coupled to control circuitry  28 . Control circuitry  28  may be coupled to input-output devices  32 . Input-output devices  32  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures such as antenna(s)  40  with the ability to cover communications frequencies of interest, antenna(s)  40  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(s)  40  may be provided with adjustable circuits such as tunable components  102  to tune antennas over communications bands of interest. Tunable components  102  may be part of a tunable filter or tunable impedance matching network, may be part of an antenna resonating element, may span a gap between an antenna resonating element and antenna ground, etc. Tunable components  102  may include tunable inductors, tunable capacitors, or other tunable components. Tunable components such as these may be based on switches and networks of fixed components, distributed metal structures that produce associated distributed capacitances and inductances, variable solid state devices for producing variable capacitance and inductance values, tunable filters, or other suitable tunable structures. During operation of device  10 , control circuitry  28  may issue control signals on one or more paths such as path  120  that adjust inductance values, capacitance values, or other parameters associated with tunable components  102 , thereby tuning antenna structures  40  to cover desired communications bands. 
     Path  92  may include one or more transmission lines. As an example, signal path  92  of  FIG. 3  may be a transmission line having a positive signal conductor such as line  94  and a ground signal conductor such as line  96 . Lines  94  and  96  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(s)  40  to the impedance of transmission line  92 . 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 filter circuitry in antenna(s)  40  and may be tunable and/or fixed components. 
     Transmission line  92  may be coupled to antenna feed structures associated with antenna structures  40 . As an example, antenna structures  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed with a positive antenna feed terminal such as terminal  98  and a ground antenna feed terminal such as ground antenna feed terminal  100 . Positive transmission line conductor  94  may be coupled to positive antenna feed terminal  98  and ground transmission line conductor  96  may be coupled to ground antenna feed terminal  100 . Other types of antenna feed arrangements may be used if desired. For example, antenna structures  40  may be fed using multiple feeds. The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     Control circuitry  28  may use an impedance measurement circuit to gather antenna impedance information. Control circuitry  28  may use information from a proximity sensor (see, e.g., sensors  32  of  FIG. 2 ), received signal strength information, device orientation information from an orientation sensor, information from one or more antenna impedance sensors, or other information in determining when antenna  40  is being affected by the presence of nearby external objects or is otherwise in need of tuning. In response, control circuitry  28  may adjust an adjustable inductor, adjustable capacitor, switch, or other tunable component  102  to ensure that antenna  40  operates as desired. Adjustments to component  102  may also be made to extend the coverage of antenna  40  (e.g., to cover desired communications bands that extend over a range of frequencies larger than antenna  40  would cover without tuning). 
       FIG. 4  is a diagram of illustrative inverted-F antenna structures that may be used in implementing antenna  40  for device  10 . Inverted-F antenna  40  of  FIG. 4  has antenna resonating element  106  and antenna ground (ground plane)  104 . Antenna resonating element  106  may have a main resonating element arm such as arm  108 . The length of arm  108  and/or portions of arm  108  may be selected so that antenna  40  resonates at desired operating frequencies. For example, if the length of arm  108  may be a quarter of a wavelength at a desired operating frequency for antenna  40 . Antenna  40  may also exhibit resonances at harmonic frequencies. 
     Main resonating element arm  108  may be coupled to ground  104  by return path  110 . An inductor or other component may be interposed in path  110  and/or tunable components  102  may be interposed in path  110  and/or coupled in parallel with path  110  between arm  108  and ground  104 . 
     Antenna  40  may be fed using one or more antenna feeds. For example, antenna  40  may be fed using antenna feed  112 . Antenna feed  112  may include positive antenna feed terminal  98  and ground antenna feed terminal  100  and may run in parallel to return path  110  between arm  108  and ground  104 . If desired, inverted-F antennas such as illustrative antenna  40  of  FIG. 4  may have more than one resonating arm branch (e.g., to create multiple frequency resonances to support operations in multiple communications bands) or may have other antenna structures (e.g., parasitic antenna resonating elements, tunable components to support antenna tuning, etc.). For example, arm  108  may have left and right branches that extend outwardly from feed  112  and return path  110 . Multiple feeds may be used to feed antennas such as antenna  40 . 
     Antenna  40  may be a hybrid antenna that includes one or more slot antenna resonating elements. As shown in  FIG. 5 , for example, antenna  40  may be based on a slot antenna configuration having an opening such as slot  114  that is formed within conductive structures such as antenna ground  104 . Slot  114  may be filled with air, plastic, and/or other dielectric. The shape of slot  114  may be straight or may have one or more bends (i.e., slot  114  may have an elongated shape following a meandering path). The antenna feed for antenna  40  may include positive antenna feed terminal  98  and ground antenna feed terminal  100 . Feed terminals  98  and  100  may, for example, be located on opposing sides of slot  114  (e.g., on opposing long sides). Slot-based antenna resonating elements such as slot antenna resonating element  114  of  FIG. 5  may give rise to an antenna resonance at frequencies in which the wavelength of the antenna signals is equal to the perimeter of the slot. In narrow slots, the resonant frequency of a slot antenna resonating element is associated with signal frequencies at which the slot length is equal to a half of a wavelength. Slot antenna frequency response can be tuned using one or more tunable components such as tunable inductors or tunable capacitors. These components may have terminals that are coupled to opposing sides of the slot (i.e., the tunable components may bridge the slot). If desired, tunable components may have terminals that are coupled to respective locations along the length of one of the sides of slot  114 . Combinations of these arrangements may also be used. 
     Antenna  40  may be a hybrid slot-inverted-F antenna that includes resonating elements of the type shown in both  FIG. 4  and  FIG. 5 . An illustrative configuration for an antenna with slot and inverted-F antenna structures is shown in  FIG. 6 . As shown in  FIG. 6 , antenna  40  (e.g., a hybrid slot-inverted-F antenna) may be fed by transceiver circuitry that is coupled to antenna feed  112 . One or more additional feeds may be coupled to antenna  40 , if desired. Antenna  40  may include a slot such as slot  114  that is formed from an elongated gap between peripheral conductive structures  16  and ground  104  (e.g., a slot formed in housing  12  using machining tools or other equipment). The slot may be filled with dielectrics such as air and/or plastic. For example, plastic may be inserted into the portions of slot  114  that are flush with the outside of housing  12 . 
     Portions of slot  114  may contribute slot antenna resonances to antenna  40 . Peripheral conductive structures  16  may form an antenna resonating element arm such as arm  108  of  FIG. 4  that extends between gaps  18 - 1  and  18 - 2  (e.g., gaps  18  in peripheral conductive structures  16 ). A return path such as path  110  of  FIG. 4  may be formed by a fixed conductive path bridging slot  114  or an adjustable component such as a switch that can be closed to form a short circuit across slot  114 . 
     To enhance frequency coverage for antenna  40 , antenna  40  may be provided with a parasitic antenna resonating element such as parasitic antenna resonating element  158 . Device  10  may also have one or more supplemental antennas such as antenna  150  to enhance the frequency coverage of antenna  40 . Antenna  150  may be fed using a feed that is separate from feed  112 . 
     Optional adjustable components such as components  152 ,  154 , and  156  may be used in adjusting the operation of antenna  40 . Components  152 ,  154 , and  156  may include switches, switches coupled to fixed components such as inductors and capacitors and other circuitry for providing adjustable amounts of capacitance, adjustable amounts of inductance, etc. Adjustable components in antenna  40  may be used to tune antenna coverage, may be used to restore antenna performance that has been degraded due to the presence of an external object such as a hand or other body part of a user, and/or may be used to adjust for other operating conditions and to ensure satisfactory operation at desired frequencies. 
     Parasitic antenna resonating element  158  may have a first end such as end  160  that protrudes into slot  114  from antenna ground  104  at a given location along the length of slot  114  and may have a second end such as end  162  that lies within slot  114 . Slot  114  may have an elongated shape (e.g., a slot shape) or other suitable elongated gap shape. In the example of  FIG. 6 , slot  114  has a U shape that runs along the periphery of device  10  between peripheral conductive structures  16  (e.g., housing sidewalls) and portions of the rear wall of device  10  (e.g., ground  104 ). In this type of configuration, parasitic antenna resonating element  158  may extend from end  160  to end  162  along the length of slot  114  without touching peripheral conductive structures  16  or ground  104  on the opposing side of slot  114  (i.e., without allowing the edges of element  158  to contact the inner surfaces of the metal housing forming slot  114 ). 
     The length of slot  114  may be about 4-20 cm, more than 2 cm, more than 4 cm, more than 8 cm, more than 12 cm, less than 25 cm, less than 15 cm, less than 10 cm, or other suitable length. Element  158  may have a width D3 of about 0.5 mm (e.g., less than 0.8 mm, less than 0.6 mm, more than 0.3 mm, 0.4 to 0.6 mm, etc.) or other suitable width. Slot  114  may have a width of about 2 mm (e.g., less than 4 mm, less than 3 mm, less than 2 mm, more than 1 mm, more than 1.5 mm, 1-3 mm, etc.) or other suitable width. The length of element  158  may be 1-10 cm, more than 2 cm, 2-7 cm, 1-5 cm, less than 10 cm, less than 5 cm, or other suitable length). The portions of slot  114  that separate element  158  from ground  104  and peripheral conductive housing structures  16  may have a width D2 of about 0.75 (e.g., more than 0.4, more than 0.6, less than 0.8, less than 1 mm, 0.3-1.2 mm, etc.). 
     Element  158  may resonate in a desired communications band and thereby provide enhanced frequency coverage for antenna  40  in the desired communications band (e.g., element  158  may resonant at frequencies in a high communications band at 2300-2700 MHz or other suitable band). Element  158  may be formed from a metal structure on a printed circuit, from a portion of a conductive housing structure, or from other conductive structures in device  10 . 
     In the example of  FIG. 6 , slot  114  has a U shape. If desired, slot  114  may have other shapes such as the straight slot shape of slot  114  of  FIG. 7 . In an arrangement of the type shown in  FIG. 6 , the tip of element  158  may be bent to accommodate a bend of slot  114  at the corner of device  10 . In the illustrative arrangement of  FIG. 7 , element  158  is straight and unbent. In other configurations for antenna  40 , slot  114  and element  158  may have different shapes. The arrangements of  FIGS. 6 and 7  are illustrative. 
       FIG. 8  is a graph in which antenna performance (standing-wave ratio SWR) has been plotted as a function of operating frequency f for an illustrative antenna such as antenna  40  of  FIGS. 6 and 7  (including parasitic element  158  and supplemental antenna element  150 ). As shown in  FIG. 8 , antenna  40  may exhibit resonances in a low band LB, low-middle band LMB, midband MB, and high band HB. 
     Low band LB may extend from 700 MHz to 960 MHz or other suitable frequency range. Peripheral conductive structures  16  may serve as an inverted-F resonating element arm such as arm  108  of  FIG. 4 . The resonance of antenna  40  at low band LB may be associated with the distance along peripheral conductive structures  16  between component  152  of  FIG. 6  and gap  18 - 2 . Gap  18 - 2  may be one of gaps  18  in peripheral conductive housing structures  16 .  FIG. 6  is a rear view of device  10 , so gap  18 - 2  of  FIG. 6  lies on the left edge of device  10  when device  10  is viewed from the front. Component  152  may include a switch that can be closed to form a return path for an inverted-F antenna (e.g., an inverted-F antenna that has a resonating element arm formed from structures  16 ) and/or other return path structures may be formed for antenna  40 . 
     Low midband LMB may extend from 1400 MHz to 1710 MHz or other suitable frequency range. An antenna resonance for supporting communications at frequencies in low midband LMB may be associated with a monopole element, inverted-F antenna element, or other antenna element such as element  150 . 
     Midband MB may extend from 1710 MHz to 2170 MHz or other suitable frequency range. Antenna  40  may exhibit first and second resonances in midband MB. A first of these midband resonances may be associated with the distance between feed  112  and gap  18 - 2 . A second of these resonances may be associated with the distance between feed  112  and component  152  (e.g., a switch that may be used in forming a return path). 
     High band HB may extend from 2300 MHz to 2700 MHz or other suitable frequency range. Antenna performance in high band HB may be supported by the resonance of parasitic antenna resonating element  158  (e.g., the length of element  158  may exhibit a quarter wavelength resonance at operating frequencies in band HB). 
       FIG. 9  is a diagram of an illustrative feed arrangement for antenna  150  (e.g., an inverted-F antenna). As shown in  FIG. 9 , radio-frequency transceiver circuitry  90  may be coupled to antenna  150  using a transmission line such as transmission line  92 ′. Transmission line  92 ′ may have positive signal line  94 ′ and ground signal lines  96 ′. Switching circuitry such as switching circuitry  200  may be interposed in transmission line  92 ′ between feed  112 ′ of antenna  150  and transceiver circuitry  90 . Feed  112 ′ may have a positive antenna feed terminal such as positive antenna feed terminal  98 ′ and a ground antenna feed terminal such as ground antenna feed terminal  100 ′. Switching circuitry  200  may have switches such as switches S 1 , S 2 , and S 3 . Switches S 1 , S 2 , and S 3  may be controlled by control signals from control circuitry  28 . 
     As shown in  FIG. 9 , switch S 3  may have a first terminal such as terminal  206  that is coupled to positive antenna feed terminal  98 ′ and may have a corresponding second terminal such as terminal  204  that is coupled to positive signal line  94 ′ in transmission line  92 ′. Switch S 1  may have a first terminal such as terminal  210  that is coupled to ground antenna feed terminal  100 ′ and a second terminal such as terminal  208  that is coupled to ground signal line  96 ′ in transmission line  92 . Switch S 2  may have a first terminal such as terminal  212  that is coupled to terminal  98 ′ and a second terminal such as terminal  214  that is coupled to impedance matching network M. Matching network M may be coupled between terminal  214  and line  96 ′. 
     Control circuitry  28  may operate antenna  150  in multiple states using switching circuitry  200 . These states may include an isolation mode in which antenna  150  is isolated from the other antenna structures of device  10 , a free space mode in which antenna  150  is configured for optimal operation in free space, a narrowband grip mode in which antenna  150  is configured to operate in a narrow communications band while held by a user, and a wideband grip mode in which antenna  150  is configured to operate in a wide communications band (e.g., a band that is wider than the narrow communications band) while held by a user. In the free space mode, antenna  150  may be configured to operate at a frequency of 1400 MHz (or other suitable frequency). When being used by a user, the resonance of antenna  150  has the potential to shift to a lower frequency. In the narrowband grip mode and the wideband grip mode, antenna  150  is configured to operate at its desired operation frequency (i.e., the resonance of antenna  150  is tuned upwards to its desired frequency by configuring switches S 1 , S 2 , and S 3 ). 
     Antenna  150  may be configured to operate in the isolation mode by opening switches S 1 , S 2 , and S 3 . In this mode, antenna  150  is isolated from transmission line  92 ′ and floats. While isolated in this way, antenna  150  may serve as a parasitic antenna resonating element for antenna  40  at frequencies of 2300-2700 MHz or other suitable frequencies (e.g., high band frequencies). Antenna  150  may be placed in the free space mode by closing switches S 1  and S 3  and opening S 2  (to switch matching circuit M out of use). In the narrowband grip mode, switch S 3  may be closed and switches S 1  and S 2  may be turned off. With switch S 3  closed, antenna matching circuit M is switched into use to ensure that antenna  150  operates properly, even when gripped by a user. In the wideband grip mode, switches S 1  and S 3  are turned on and switch S 2  is opened, providing antenna  150  with a wider bandwidth than the narrowband grip mode (although with somewhat reduced efficiency). 
       FIG. 10  is a perspective view of antenna  150 . Antenna  150  may be an inverted-F antenna that includes an antenna resonating element (see, e.g., arm  108  of  FIG. 4 ) and antenna ground  104 . The antenna resonating element of antenna  150  may have antenna resonating element arm segments  108 A,  108 B,  108 C,  108 D, and  108 E. The resonating element may be formed from metal having the shape of shown in  FIG. 11  (as an example). As shown in  FIG. 11 , the resonating element arm may have three or more right-angle bends and three or more or four or more segments. This resonating element may be supported by a dielectric support structure such as plastic support structure  310  of  FIG. 10 . 
     Transmission line  92 ′ may be implemented using signal traces on flexible printed circuit  300 . Matching network M may be formed by components mounted on flexible printed circuit  300  such as component  302 . Components such as component  302  may also be used to form switching circuitry  200 . Pads  304  and  306  allow the transmission line signal conductors of printed circuit  300  and the matching network M of component(s)  302  to be coupled to respective antenna terminals  100 ′ and  98 ′. Antenna  150  may be electromagnetically coupled to the antenna (e.g., antenna  40 ) formed from peripheral conductive structures  16 . During use of antenna  150 , structures  16  may serve as a parasitic antenna resonating element for antenna  150  that improves antenna efficiency. 
     Although described in the context of an inverted-F antenna, antenna  150  may be implemented using any suitable type of antenna (patch, inverted-F, monopole, loop, slot, hybrid, etc.) and may be implemented using conductive structures formed from portions of housing  12 , internal metal structures in device  10  (e.g., interior metal housing members), metal traces on a printed circuit such as a rigid printed circuit board or a flexible printed circuit, laser-patterned electroplated traces on a plastic carrier, metal foil, metal parts embedded into or attached to a molded plastic carrier or other dielectric support structure, wire, or other conductive structures. In the arrangement of  FIG. 10 , antenna structures for antenna  150  may be formed from metal structures (metal traces, metal foil, etc.) that form an antenna resonating element arm supported by a plastic carrier (carrier  310 ). This type of support arrangement for the metal structures of antenna  150  is merely illustrative. Other types of antenna structures may be used in forming antenna  150 , if desired. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20150805
Publication Date: 20180515
Grant Date: 20180515
Priority Date: 20150805
Inventors: AYALA VAZQUEZ, ENRIQUE
HU, HONGFEI
JIN, NANBO
MOW, MATTHEW A.
HAN, LIANG
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/2258", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/22", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/378", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/50", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/378", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/36", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/242", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/378", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 57989534