PATENT DOCUMENT

Publication Number: US-9236659-B2
Application Number: US-201314096417-A
Country: US
Kind Code: B2

Title: Electronic device with hybrid inverted-F slot antenna

Abstract:
An electronic device may be provided with a housing. The housing may have a periphery that is surrounded by peripheral conductive structures such as a segmented peripheral metal member. A segment of the peripheral metal member may be separated from a ground by a slot. An antenna feed may have a positive antenna terminal coupled to the peripheral metal member and a ground terminal coupled to the ground and may feed both an inverted-F antenna structure that is formed from the peripheral metal member and the ground and a slot antenna structure that is formed from the slot. Control circuitry may tune the antenna by controlling adjustable components that are coupled to the peripheral metal member. The adjustable components may include adjustable inductors and adjustable capacitors.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing having peripheral conductive structures; and 
 a hybrid inverted-F slot antenna, wherein the hybrid inverted-F slot antenna has an inverted-F antenna portion formed from an inverted-F antenna resonating element and an antenna ground, wherein the inverted-F antenna resonating element is formed from the peripheral conductive structures, wherein the hybrid inverted-F slot antenna has a slot antenna portion formed from an opening between the inverted-F antenna resonating element and the antenna ground, and wherein the hybrid inverted-F slot antenna has an antenna feed that feeds both the inverted-F antenna portion and the slot antenna portion. 
 
     
     
       2. The electronic device defined in  claim 1  further comprising an adjustable component coupled to the peripheral conductive structures. 
     
     
       3. The electronic device defined in  claim 2  further comprising control circuitry that controls the adjustable component to tune the hybrid inverted-F slot antenna. 
     
     
       4. The electronic device defined in  claim 3  wherein the adjustable component comprises an adjustable inductor that bridges the opening. 
     
     
       5. The electronic device defined in  claim 3  wherein the adjustable component comprises an adjustable capacitor that bridges the opening. 
     
     
       6. The electronic device defined in  claim 3  wherein the hybrid inverted-F slot antenna is configured to operate in low, medium, and high communications bands and wherein the adjustable component comprises an adjustable inductor that is controlled by the control circuitry to tune the low communications band. 
     
     
       7. The electronic device defined in  claim 6  wherein the inverted-F antenna portion is configured to exhibit respective resonances in at least the low and medium communications bands and wherein the slot antenna portion is configured to exhibit a resonance in the high communications band. 
     
     
       8. The electronic device defined in  claim 6  further comprising an additional adjustable inductor bridging the opening that is controlled by the control circuitry to tune the middle communications band. 
     
     
       9. The electronic device defined in  claim 3  wherein the hybrid inverted-F slot antenna is configured to operate in low, medium, and high communications bands and wherein the adjustable component comprises a capacitor with which the high communications band is pulled to a lower frequency. 
     
     
       10. The electronic device defined in  claim 9  wherein the inverted-F antenna portion is configured to exhibit resonances in at least the low and medium communications bands and wherein the slot antenna portion is configured to exhibit a resonance in the high communications band. 
     
     
       11. The electronic device defined in  claim 1  further comprising a display with an active area, wherein the antenna ground has a first portion that is overlapped by the active area and a second portion that extends from the first portion and wherein the second portion is separated from the peripheral conductive structure by the opening. 
     
     
       12. The electronic device defined in  claim 1  further comprising a tunable inductor coupled to the peripheral conductive structures and a tunable capacitor coupled to the peripheral conductive structures. 
     
     
       13. The electronic device defined in  claim 12  further comprising a rectangular housing, wherein the peripheral conductive structures are portions of a metal housing sidewall that runs around the housing and that includes gaps to create a metal segment and wherein the metal segment forms short and long branches of an arm in the inverted-F antenna resonating element. 
     
     
       14. A hybrid inverted-F slot antenna, comprising:
 a peripheral conductive member of an electronic device housing; 
 a ground with an extended portion adjacent to the peripheral conductive member so that the extended portion of the ground and the peripheral conductive member are separated by a slot; and 
 an antenna feed having a positive antenna feed terminal coupled to the peripheral conductive member and a ground antenna feed terminal coupled to the ground plane, wherein the antenna feed feeds an inverted-F antenna portion of the hybrid inverted-F slot antenna formed from the peripheral conductive member and the ground and feeds a slot antenna portion of the hybrid inverted-F slot antenna formed from the slot. 
 
     
     
       15. The hybrid inverted-F slot antenna defined in  claim 14  wherein the electronic device housing comprises a handheld electronic device housing, wherein the peripheral conductive member includes a metal segment of a peripheral housing sidewall structure of the electronic device housing, and wherein the inverted-F antenna portion of the hybrid inverted-F slot antenna comprises a first branch and a second branch of a resonating element arm that is formed from the metal segment. 
     
     
       16. The hybrid inverted-F slot antenna defined in  claim 15  wherein the inverted-F antenna portion and the slot antenna portion are configured so that the hybrid inverted-F slot antenna resonates in a low band, a middle band, and a high band. 
     
     
       17. The hybrid inverted-F slot antenna defined in  claim 16  further comprising an adjustable component that bridges that slot to tune the low band. 
     
     
       18. A hybrid inverted-F slot antenna comprising:
 a peripheral conductive member that runs along at least part of an electronic device housing periphery; 
 a ground that is separated from the peripheral conductive member by a slot; 
 an adjustable component coupled to the peripheral conductive member; and 
 an antenna feed having a positive antenna feed terminal coupled to the peripheral conductive member and a ground antenna feed terminal coupled to the ground, wherein the antenna feed feeds an inverted-F antenna structure formed from the peripheral conductive member and the ground and feeds a slot antenna structure formed from the slot. 
 
     
     
       19. The hybrid inverted-F antenna defined in  claim 18  wherein the inverted-F antenna structure is configured to resonate in a first communications band and wherein the adjustable component comprises an adjustable inductor that bridges the slot. 
     
     
       20. The hybrid inverted-F antenna defined in  claim 19  wherein the inverted-F antenna structure is configured to resonate in a second communications band and wherein the slot is configured to resonate in a third communications band, wherein the second communications band covers higher frequencies than the first communications band, and wherein the third communications band covers higher frequencies than the second communications band.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with antennas. 
     Electronic devices often include 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 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 be provided with a housing. The housing may have a periphery that is surrounded by peripheral conductive structures such as a peripheral metal member. A segment of the peripheral metal member may be separated from a ground by a slot that runs along an inner edge of the peripheral metal member. An antenna feed may have a positive antenna feed terminal coupled to the peripheral metal member and a ground antenna feed terminal coupled to the ground and may feed both an inverted-F antenna structure that is formed from the peripheral metal member and the ground and a slot antenna structure that is formed from the slot. 
     Control circuitry may tune the antenna by controlling adjustable components that are coupled to the peripheral metal member. The adjustable components may include adjustable inductors and adjustable capacitors. A hybrid antenna may be formed from the inverted-F antenna structure and the slot antenna structure, which are fed using a common antenna feed. The hybrid antenna may be configured to resonant in multiple communications bands. For example, the hybrid antenna may be configured to cover a low band, a middle band, and a high band. The inverted-F antenna may have a resonating element arm with a long branch that generates an antenna resonance in the low band and a short branch that generates an antenna resonance for the middle band. The high band response of the antenna may be supported by the slot and using a harmonic of an inverted-F antenna resonance. 
     The adjustable components may bridge the slot. The control circuitry may tune the low band using an inductor that bridges the slot, may tune the middle band using an inductor that bridges the slot, or may otherwise use an adjustable inductor or multiple adjustable inductors to tune antenna performance. High band antenna adjustments may be performed using an adjustable capacitor that bridges the slot or other adjustable components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with wireless circuitry 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 inverted-F antenna with an inductor to tune the antenna to cover desired operating frequencies in accordance with an embodiment. 
         FIG. 6  is a schematic diagram of an illustrative inverted-F antenna with a capacitor to tune the antenna to cover desired operating frequencies in accordance with an embodiment. 
         FIG. 7  is a diagram of an illustrative slot antenna in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram of an illustrative hybrid inverted-F slot antenna having optional tuning components in accordance with an embodiment. 
         FIG. 9  is a graph in which antenna performance (standing wave ratio) has been plotted as a function of operating frequency for an illustrative antenna of the type shown in  FIG. 8  in accordance with an embodiment. 
         FIG. 10  is a diagram of an illustrative electronic device having a slot that may be used in forming an antenna in accordance with an embodiment. 
         FIG. 11  is a diagram of an illustrative electronic device with a narrow loop-shaped opening that has a portion running between an extended portion of a ground plane and a peripheral conductive housing member 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 or more antennas. 
     The antennas can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. The conductive electronic device structures may include conductive housing structures. The housing structures may include peripheral structures such as a peripheral conductive member that runs around the periphery of an electronic device. The peripheral conductive member may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, and/or may form other housing structures. Gaps may be formed in the peripheral conductive member that divide the peripheral conductive member into segments. One or more of the segments may be used in forming one or more antennas for electronic device  10 . 
     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 television, a set-top box, a desktop computer, a computer monitor into which a computer has been integrated, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable image pixel structures. A display cover layer such as a layer of clear glass or plastic may cover the surface of display  14 . 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 a peripheral housing member 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 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, etc.). 
     Peripheral housing structures  16  may be fomled 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. If desired, 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 ). In the example of  FIG. 1 , peripheral housing structures  16  have substantially straight vertical sidewalls. This is merely illustrative. The sidewalls formed by peripheral housing structures  16  may be 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 left and right sides of housing  12  may be formed as 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. 
     Display  14  may include conductive structures such as an array of capacitive electrodes, conductive lines for addressing pixel elements, driver circuits, etc. Housing  12  may include internal structures such as metal frame members, a planar housing member (sometimes referred to as a midplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more parts that is welded or otherwise connected between opposing sides of member  16 ), 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  under active area AA of display  14  (e.g., the portion of display  14  that contains circuitry and other structures for displaying images). 
     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. 
     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, extensions of the ground plane under active area AA of display  14  and/or other metal structures in device  10  may have portions that extend into parts of the dielectric-filled openings in regions  20  and  22 . 
     In general, device  10  may include any suitable number of antennas (e.g., one or more, two or more, three or more, four or more, etc.). The antennas in device  10  may be located at opposing first and second ends of an elongated device housing (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 such locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral housing structures  16  may be provided with gap structures. For example, peripheral 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 gaps), three peripheral conductive segments (e.g., in an arrangement with three gaps), four peripheral conductive segments (e.g., in an arrangement with four gaps, etc.). The segments of peripheral conductive housing structures  16  that are formed in this way may form parts of antennas in device  10 . 
     In a typical scenario, device  10  may have upper and lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, etc. 
     A schematic diagram 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, 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 may include touch screens, displays without touch sensor capabilities, buttons, joysticks, click wheels, 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, motion sensors (accelerometers), capacitance sensors, proximity sensors, 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 hands. 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 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  40  with the ability to cover communications frequencies of interest, antenna structures  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 structures  26  may be provided with adjustable circuits such as tunable components  102  to tune antennas over communications bands of interest. 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  103  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 structures  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 structures  40 . 
     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  92 . Other types of antenna feed arrangements may be used if desired. The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
       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  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 . 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.). 
       FIG. 5  is a diagram of an illustrative inverted-F antenna configuration of the type that may be used to implement a tunable antenna. As shown in  FIG. 5 , antenna  40  may be provided with an inductor L that couples a portion of antenna resonating element arm  108  (e.g., a tip of arm  108 ) in resonating element  106  to antenna ground  104 . Inductor L may be a fixed inductor or may be a variable inductor. For example, inductor L may be an adjustable inductor that is formed from one or more switches or other switching circuitry and a set of fixed inductors. During operation of device  10 , control circuitry  28  can issue control signals that adjust the switching circuitry (e.g., that open and close switches in the switching circuitry), thereby switching desired patterns of the set of fixed inductors into and out of use to adjust the inductance value of inductor L. Adjustments such as these may be made to vary the inductance of inductor L when it is desired to tune the frequency response of antenna  40  (e.g., when it is desired to tune the low band resonance of antenna  40 , when it is desired to tune a mid-band resonance of antenna  40 , etc.). For example, increases to the value of L may be made to increase the frequency of the communications band(s) in which antenna  40  is operating (e.g., to increase a low-band resonant frequency or a mid-band resonant frequency). One or more inductors such as inductor L may be coupled between arm  108  and ground  104  at one or more locations along the length of arm  108 . The configuration of  FIG. 5  is illustrative. 
       FIG. 6  is a diagram of an illustrative inverted-F antenna structure with a capacitor that may be used to implement a tunable antenna. As shown in  FIG. 6 , antenna  40  may be provided with a capacitor C that couples a tip portion of antenna resonating element arm  108  in resonating element  106  to antenna ground  104 . Capacitors such as capacitor C may also be coupled to arm  108  at other locations. Capacitor C may be a fixed capacitor or may be a variable capacitor. For example, capacitor C may be formed from one or more switches or other switching circuitry and a set of fixed capacitors (e.g., a programmable capacitor) or a varactor. During operation of device  10 , control circuitry  28  can issue control signals that open and close switches in the switching circuitry to switch desired capacitors into and out of use or that otherwise make adjustments to capacitor C, thereby varying the capacitance value exhibited by capacitor C. Adjustments such as these may be made to vary the capacitance of capacitance C when it is desired to tune the frequency response of antenna  40  (e.g. when it is desired to tune the low band resonance of antenna  40 , when it is desired to tune a mid-band resonance of antenna  40 , or when it is desired to tune a high band resonance of antenna  40 ). For example, increases to the value of C may be made to decrease the frequency range of the communications band(s) in which antenna  40  is operating (e.g., to decrease a high-band resonant frequency). Capacitor C need not be located at the tip of arm  108 . For example, the resonant frequency decrease associated with inclusion of capacitor C in antenna  40  can be enhanced by locating capacitor C closer to feed  112 . 
     Antenna  40  may include a slot antenna resonating element. As shown in  FIG. 7 , for example, antenna  40  may be a slot antenna having an opening such as slot  114  that is formed within antenna ground  104 . Slot  114  may be filled with air, plastic, and/or other dielectric. The shape of slot  14  may be straight or may have one or more bends (i.e., slot  114  may have an elongated shape follow 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. 7  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. 
     If desired, antenna  40  may incorporate conductive device structures such as portions of housing  12 . As an example, peripheral conductive structures  16  may include multiple segments such as segments  16 - 1 ,  16 - 2 , and  16 - 3  of  FIG. 8  that are separated from each other by gaps  18  (e.g., spaces between the adjoining ends of the segments that are filled with plastic or other dielectric). In antenna  40  of  FIG. 8 , segment  16 - 1  may be formed from a strip of stainless steel or other metal that forms a segment of a peripheral conductive housing member (e.g., a stainless steel member or other peripheral metal housing structure) that runs around the entire periphery of device  10 . Segment  16 - 1  may form an antenna resonating arm  108  in an inverted-F antenna. For example, segment  16 - 1  may form a dual-band inverted-F antenna resonating element having a longer branch that contributes an antenna response in a low frequency communications band (low band LB) and having a shorter branch that contributes an antenna response in a middle frequency communications band (middle band MB). Dual-band inverted-F antenna structures of this type may sometimes be referred to as T-shaped antennas or T-antennas. A return path conductor such as a strip of metal may be used to form return path  110  between peripheral conductive segment  16 - 1  (i.e., the main resonating element arm of the T-antenna resonating element) and antenna ground  104 . 
     Antenna ground  104  may have ground structures such as a substantially rectangular antenna ground plane portion in the center of device  10  (e.g. the portion of device underlying active area AA of display  14  of  FIG. 1 ). Antenna ground  104  may also have a portion such as ground plane extension  104 E that extends outwards from the main antenna ground region in device  10 . Ground plane extension  104 E may protrude into an end region of device  10  such as lower end region  20 . Ground plane extension  104 E of antenna ground  104  may be separated from the main portion of antenna ground  104  and peripheral segment  16 - 1  by an opening that forms antenna slot  114 . Antenna slot  114  may be fed using antenna feed  112  (i.e., using antenna feed terminals on opposing sides of slot  114  such as positive antenna feed terminal  98  and ground antenna feed terminal  100 ). The magnitude of the periphery of antenna slot  108  may determine the frequency at which slot  114  resonances and may therefore be used to produce a desired resonance for antenna  40  (e.g., a high band resonance HB that complements low band resonance LB and midband resonance MB associated with the T-antenna formed from segment  16 - 1 ). 
     When operating antenna  40  in device  10 , both the T-antenna formed from segment  16 - 1  of peripheral conductive housing member  16  (i.e., the inverted-F antenna) and the slot antenna formed from slot  114  may contribute to the overall response of the antenna. Because two different types of antenna contribute to the operation of antenna  40  (i.e., the inverted-F antenna portion and the slot antenna portion), antenna  40  may sometimes be referred to as a hybrid inverted-F slot antenna or hybrid antenna. If desired, optional electrical components such as inductors and/or capacitors may be coupled to antenna  40 . For example, one or more inductors such as inductors L 1 , L 2 , and L 3  may bridge slot  114  or may be coupled to different locations along the periphery of slot  114  and/or one or more capacitors such as capacitors C 1  and C 2  may bridge slot  114  or may be coupled to different locations along the periphery of slot  114 . These optional electrical components may be fixed and/or adjustable components. For example, the values of L 1 , L 2 , L 3 , C 1 , and/or C 2  or a subset of one or more of these components may be adjusted to tune antenna  40 . 
       FIG. 9  is a graph in which antenna performance (standing-wave ratio SWR) has been plotted as a function of operating frequency for an illustrative antenna such as antenna  40  of  FIG. 8 . As shown in  FIG. 9 , antenna  40  may exhibit multiple resonances to support operation in multiple communications bands. For example, antenna  40  may exhibit three resonances for operating in a low band LB, a middle band MB, and a high band HB. Low band LB may cover communications frequencies from 700 to 960 MHz or other suitable low band frequencies. Middle band MB may cover communications frequencies from 1710 to 2170 MHz or other suitable midband frequencies. High band HB may cover communications frequencies from 2300 to 2700 MHz or other suitable high band frequencies. 
     The size and shape of conductive antenna structures such as inverted-F antenna resonating element  108 , slot antenna resonating element  114  and ground  104  affect the frequency response of antenna  40 . 
     With one suitable arrangement, the antenna resonance of  FIG. 9  that is associated with low band LB is produced by the inverted-F antenna structures of antenna  40  of  FIG. 8  (i.e., LB is generated by the longer of the two branches of inverted-F resonating element arm  108 ), the antenna resonance that is associated with middle hand MB may be produced partly by the shorter branch of inverted-F arm  108  and partly by slot  114  (or just by the shorter branch), and the antenna resonance that is associated with high band HB may be produced partly by slot antenna  114  and partly by a harmonic of low band LB (e.g. a second harmonic that is tuned to lower frequencies using one or more capacitors such as capacitors C 1  and/or C 2 ). Tunable inductor L 2  may be used to tune low band LB. Tunable inductor L may be used to tune midband MB. Optional inductor L 3  may have a fixed value that helps ensure that the low band resonance LB covers desired low band frequencies. 
     The total inductance bridging slot  114  in the vicinity of inductor L 1  and return path  110  is affected by both the inductance of inductor L 1  and the inductance of return path  110 , which bridges slot  114  in parallel with inductor L 1 . The inductance of return path  110  may be about 6 nH (as an example). Tunable inductor L 1  may, as an example, have an inductance value that is adjustable between a first state of 0 nH and a second state of 12 nH (as an example). With this type of arrangement, inductor L 1  operating in parallel with return path  110  may be used to generate a first inductance of 0 nH (when inductor L 1  exhibits a 0 nH inductance) or 6 nH (when inductor L 1  is 12 nH and the parallel inductance of return path  110  is 12 nH). 
     There may be one capacitor bridging slot  114 , two capacitors bridging slot  114 , or three or more capacitors bridging slot  114 . The capacitors can be located at the position shown by capacitors C 1  and C 2  of  FIG. 8  or other locations in antenna  40 . In the presence of one or more optional capacitors such as capacitors C 1  and C 2  of  FIG. 8 , the frequency response of antenna  40  can be pulled lower as described in connection with  FIG. 6 . 
     Device  10  may include connectors for data ports and other electrical components. One or more of these electrical components may be mounted in housing  12  in a position that minimizes interference with antenna  40 . For example, a data port connector or other electrical component may be mounted in device  10  in a location such as location  116  that overlaps ground plane extension  104 E. 
     With another suitable arrangement for antenna  40  of  FIG. 8 , inductor L 1  may be omitted. Inductor L 3  may be a fixed or variable inductor that helps configure antenna  40  so that low band resonance LB covers desired operating frequencies. Low band LB may be covered using the long branch of antenna resonating element  108  and may be tuned by adjusting the inductance value produced by adjustable inductor L 2 . Middle band MB may be covered using the short branch of antenna resonating element  108 . Antenna slot  114  may be used to create antenna resonance HB (and, if desired, a second harmonic of the low band resonance from element  108  may contribute to resonance HB). 
     In the illustrative configuration of  FIG. 8 , antenna  40  has a single port (i.e., antenna feed  112  is the sole antenna feed for antenna  40 ). Antenna feed  112  is formed from antenna feed terminals  98  and  100  that extend between resonating element arm  108  and ground  104 , bridging slot  114 . Antenna feed terminals  98  simultaneously serve as a feed for the inverted-F antenna portion of hybrid antenna  40  and as a feed for the slot antenna portion of hybrid antenna  40 . During operation at frequencies in which the inverted-F antenna resonating element portion of antenna  40  is active, the antenna feed formed from terminals  98  and  100  feeds the inverted-F antenna resonating element portion of antenna  40 . During operation at frequencies in which the slot antenna resonating element portion of antenna  40  is active, the antenna feed formed from terminals  98  and  100  feeds the slot antenna resonating element portion of antenna  40 . The antenna feed is used to feed both the inverted-F antenna portion and the slot antenna portion of antenna  40  at frequencies in which both the inverted-F structures and slot structures contribute to antenna performance. 
     Antenna structures such as antenna  40  of  FIG. 8  may be provided with multiple ports if desired. For example, a first feed may be located at one point along the length of slot  114  and a second feed may be located at a different point along the length of slot  114 . In a configuration with multiple feeds, each of the multiple feeds may serve as an inverted-F feed and a slot feed or some of the feeds may be associated primarily or exclusively with the inverted-F antenna and other feeds may be associated primarily or exclusively with the slot antenna. 
     If desired, the conductive structures of antenna  40  may be configured to form slot resonating elements and inverted-F antenna resonating elements of different configurations. In the example of  FIG. 10 , antenna  40  has an antenna resonating element slot  114  that extends across the entire width of device  10 . In the example of  FIG. 11 , a resonating element is formed from a slot-shaped opening such as opening  114 ′ that loops around ground plane extension  104 E. 
     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: 20131204
Publication Date: 20160112
Grant Date: 20160112
Priority Date: 20131204
Inventors: VAZQUEZ ENRIQUE AYALA
HU HONGFEI
PASCOLINI MATTIA
OUYANG YUEHUI
ZHOU YIJUN
MOW MATTHEW A.
SCHLUB ROBERT W.
IRCI ERDINC
YARGA SALIH
TSAI MING-JU
HAN LIANG
BIEDKA THOMAS E.
REIMNITZ NICHOLAS S.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/357", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/145", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/357", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/145", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/145", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/357", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 53348512