PATENT DOCUMENT

Publication Number: US-10158384-B1
Application Number: US-201715699869-A
Country: US
Kind Code: B1

Title: Electronic devices with indirectly-fed adjustable slot elements

Abstract:
An electronic device may be provided with wireless circuitry and control circuitry. The wireless circuitry may include multiple antennas and transceiver circuitry. An antenna in the electronic device may have an inverted-F antenna resonating element formed from portions of a peripheral conductive electronic device housing structure and may have an antenna ground that is separated from the antenna resonating element by a gap. The antenna may also include an indirectly-fed antenna resonating element that is indirectly fed by a harmonic mode of the inverted-F antenna resonating element via near field electromagnetic coupling. The indirectly-fed antenna resonating element may be a slot. The antenna ground may define at least three edges of the slot and the slot may be aligned with a dielectric-filled gap in the peripheral conductive housing structures. An adjustable circuit may be coupled across the slot to tune the indirectly-fed antenna resonating element.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing having peripheral conductive housing structures; 
 an antenna resonating element arm formed from a segment of the peripheral conductive housing structures and configured to resonate in a first frequency band; 
 an antenna ground that comprises an indirectly-fed antenna resonating element, wherein the indirectly-fed antenna resonating element is configured to resonate in a second frequency band that is higher than the first frequency band and is indirectly fed by a harmonic mode of the antenna resonating element arm; 
 an antenna feed having a positive antenna feed terminal coupled to the peripheral conductive housing structures and a ground antenna feed terminal coupled to the antenna ground; and 
 an additional antenna resonating element arm formed from an additional segment of the peripheral conductive housing structures, wherein the segment of the peripheral conductive housing structures and the additional segment of the peripheral conductive housing structures extend from opposing sides of the positive antenna feed terminal. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the indirectly-fed antenna resonating element comprises a slot in the antenna ground. 
     
     
       3. The electronic device defined in  claim 2 , wherein the antenna ground defines at least three edges of the slot and the slot is aligned with a dielectric-filled gap in the peripheral conductive housing structures. 
     
     
       4. The electronic device defined in  claim 3 ,
 wherein the additional segment is configured to resonate in a third frequency band that is different than the first and second frequency bands. 
 
     
     
       5. The electronic device defined in  claim 4 , further comprising an adjustable component that is coupled between first and second terminals on the antenna ground and that bridges the slot. 
     
     
       6. The electronic device defined in  claim 5 , wherein the adjustable component is configured to adjust a resonance of the slot between the second frequency band and a fourth frequency band. 
     
     
       7. The electronic device defined in  claim 6 , wherein the fourth frequency band is higher than the third frequency band and lower than the second frequency band. 
     
     
       8. The electronic device defined in  claim 7 , wherein the adjustable circuitry comprises a component that is coupled to a switch, and the switch is adjustable between a first state in which the switch couples the component across the slot and a second state in which the switch decouples the component across the slot. 
     
     
       9. The electronic device defined in  claim 8 , wherein the second frequency band comprises frequencies between 3400 MHz and 3700 MHz and the fourth frequency band comprises frequencies between 2300 MHz and 2700 MHz. 
     
     
       10. An antenna comprising:
 an antenna ground; 
 an inverted-F antenna resonating element arm configured to resonate in a first frequency band; 
 an antenna feed having a positive antenna feed terminal coupled to the inverted-F antenna resonating element arm and a ground antenna feed terminal coupled to the antenna ground; 
 a slot having at least three edges defined by the antenna ground; and 
 an adjustable circuit having a first terminal coupled to the antenna ground at a first side of the slot and a second terminal coupled to the antenna ground at a second side of the slot, wherein the adjustable circuit is configured to tune the slot between a second frequency band that is higher than the first frequency band and a third frequency band that is a higher than the second frequency band. 
 
     
     
       11. The antenna defined in  claim 10 , wherein the slot is indirectly fed by a harmonic mode of the inverted-F antenna resonating element arm via near field electromagnetic coupling. 
     
     
       12. The antenna defined in  claim 10 , wherein an additional slot separates the inverted-F antenna resonating element arm from the antenna ground and the slot has an open end defined by an end of the additional slot. 
     
     
       13. The antenna defined in  claim 10 , wherein the adjustable circuit comprises an electronic component coupled in series with a switch between the first and second terminals. 
     
     
       14. The antenna defined in  claim 13 , wherein the slot is configured to resonate in the second frequency band when the switch is in a first state and the slot is configured to resonate in the third frequency band when the switch is in a second state. 
     
     
       15. The antenna defined in  claim 14 , wherein the component comprises a capacitor, the switch couples the capacitor between the first and second terminals and the slot resonates in the second frequency band when the switch is in the first state, and the switch decouples the capacitor between the first and second terminals and the slot resonates in the third frequency band when the switch is in the second state. 
     
     
       16. The antenna defined in  claim 15 , wherein the adjustable circuit further comprises an inductor that is coupled between the first and second terminals in parallel with the capacitor and the switch. 
     
     
       17. The antenna defined in  claim 14 , wherein the component comprises an inductor, the switch decouples the inductor between the first and second terminals and the slot resonates in the second frequency band when the switch is in the first state, and the switch couples the inductor between the first and second terminals and the slot resonates in the third frequency band when the switch is in the second state. 
     
     
       18. The antenna defined in  claim 17 , wherein the adjustable circuit further comprises a capacitor that is coupled between the first and second terminals in parallel with the inductor and the switch. 
     
     
       19. An electronic device, comprising:
 a housing having first and second conductive sidewalls and a planar conductive layer extending between the first and second conductive sidewalls; 
 a dielectric-filled gap in the first conductive sidewall that divides the first conductive sidewall into first and second portions; 
 an antenna resonating element formed from at least the first portion of the first conductive sidewall; 
 an antenna ground formed from at least the planar conductive layer and the second portion of the first conductive sidewall, wherein the planar conductive layer defines an elongated slot having a length extending along a longitudinal axis that is aligned with the dielectric-filled gap; 
 a flexible printed circuit having a first ground terminal coupled to the antenna ground at a first side of the elongated slot and a second ground terminal coupled to the antenna ground at a second side of the elongated slot, wherein the flexible printed circuit has a first portion that extends parallel to the planar conductive layer and a second portion that is bent relative to the first portion; and 
 adjustable circuitry on the flexible printed circuit and configured to adjust an operating frequency of the elongated slot. 
 
     
     
       20. The electronic device defined in  claim 19 , further comprising:
 a vibrator; and 
 a fastener that shorts both the first ground terminal of the flexible printed circuit and the vibrator to the planar conductive layer.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. 
     It can be challenging to form electronic device antenna structures with desired attributes. In some wireless devices, antennas are bulky. In other devices, antennas are compact, but are sensitive to the position of the antennas relative to external objects. If care is not taken, antennas may become detuned, may emit wireless signals with a power that is more or less than desired, or may otherwise not perform as expected. 
     It would therefore be desirable to be able to provide improved wireless circuitry for electronic devices. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry and control circuitry. The wireless circuitry may include multiple antennas and transceiver circuitry. The antennas may include antenna structures at opposing first and second ends of the electronic device. The antenna structures at a given end of the device may include adjustable components that are adjusted by the control circuitry to place the antenna structures and the electronic device in one of a number of different operating modes or states. 
     The antenna may have an inverted-F antenna resonating element formed from portions of a peripheral conductive electronic device housing structure and may have an antenna ground that is separated from the antenna resonating element by a gap. A short circuit path may bridge the gap. An antenna feed may be coupled across the gap in parallel with the short circuit path. 
     The antenna may include an indirectly-fed antenna resonating element. The indirectly-fed antenna resonating element may be indirectly fed by a harmonic mode of the inverted-F antenna resonating element via near field electromagnetic coupling. The indirectly-fed antenna resonating element may be a slot. The antenna ground may define at least three edges of the slot and the slot may be aligned with a dielectric-filled gap in the peripheral conductive housing structures. 
     An adjustable circuit may be included on a flexible printed circuit that is coupled across the slot. The adjustable circuit may have a first ground terminal coupled to a first side of the slot and a second ground terminal coupled to a second side of the slot. The adjustable circuit may adjust the resonance of the slot between a frequency in a high band and a frequency in an ultra-high band. The adjustable circuit may include a component in series with a switch between the first ground terminal and the second ground terminal. The slot may resonate at the frequency in the high band when the switch is in a first state and may resonate at the frequency in the ultra-high band when the switch is in a second state. 
    
    
     
       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 diagram of an illustrative tunable antenna in accordance with an embodiment. 
         FIG. 5  is a diagram of an illustrative tunable antenna having an indirectly-fed adjustable slot element in accordance with an embodiment. 
         FIG. 6  is a diagram of illustrative current distribution in an antenna of the type shown in  FIG. 5  in accordance with an embodiment. 
         FIG. 7  is a graph of antenna performance (antenna efficiency) as a function of frequency for a tunable antenna of the type shown in  FIG. 5  in accordance with an embodiment. 
         FIG. 8  is a top view of illustrative adjustable components that may bridge an indirectly-fed slot in a tunable antenna in accordance with an embodiment. 
         FIG. 9  is a top perspective view of an illustrative electronic device having adjustable components formed over an indirectly-fed slot in a tunable antenna in accordance with an embodiment. 
         FIGS. 10A and 10B  are circuit diagrams of illustrative adjustable circuitry that may be used to bridge an indirectly-fed slot in a tunable antenna 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 structures 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 and/or an antenna resonating element formed from conductive housing structures (e.g., internal and/or external structures, support plate structures, etc.). 
     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 (e.g., glass, ceramic, plastic, sapphire, etc.). 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 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. The rear housing wall may include conductive portions and/or dielectric portions. If desired, the rear housing wall may include a planar metal layer covered by a thin layer or coating of dielectric such as glass, plastic, sapphire, or ceramic. 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 if desired. 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, 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 or wall. 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. Peripheral conductive housing structures  16  and/or the conductive rear wall of housing  12  may form one or more exterior surfaces of device  10  (e.g., surfaces that are visible to a user of device  10 ) and/or may be implemented using internal structures that do not form exterior surfaces of device  10  (e.g., conductive housing structures that are not visible to a user of device  10  such as conductive structures that are covered with layers such as thin cosmetic layers, protective coatings, and/or other coating layers that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide structures  16  from view of the user). 
     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 backplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more metal parts that is welded or otherwise connected between opposing sides of member  16 ). The backplate may form an exterior rear surface of device  10  or may be covered by layers such as thin cosmetic layers, protective coatings, and/or other coatings that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide the backplate from view of the user. 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 extend under active area AA of display  14 , for example. 
     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 portions of housing  12 , conductive traces on a printed circuit board, conductive electrical components in display  14 , etc.). These openings, which may sometimes be referred to as gaps, may be filled with air, plastic, and/or other dielectrics and may be used in forming slot antenna resonating elements for one or more antennas in device  10 , if desired. 
     Conductive housing structures and other conductive structures in device  10  may serve as a ground plane for the antennas in device  10 . The openings in regions  20  and  22  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, 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 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 of 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 one or more upper antennas and one or more 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 to 1710 MHz, a midband from 1710 to 2170 MHz, a high band from 2170 to 2700 MHz, an ultra-high band from 3400 to 3700 MHz or other communications bands between 600 MHz and 4000 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, dipole antenna structures, monopole 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  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, a stripline transmission line, or a microstrip transmission line (as examples). A matching network (e.g., an adjustable matching network formed using tunable components  102 ) may include components such as inductors, resistors, and capacitors 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  110  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 information from a proximity sensor (see, e.g., sensors  32  of  FIG. 2 ), wireless performance metric data such as received signal strength information, device orientation information from an orientation sensor, device motion data from an accelerometer or other motion detecting sensor, information about a usage scenario of device  10 , information about whether audio is being played through speaker  26 , information from one or more antenna impedance sensors, and/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). 
     An illustrative antenna of the type that may be used in device  10  (e.g., in region  20  and/or region  22  of  FIG. 1 ) is shown in  FIG. 4 . As shown in  FIG. 4 , antenna  40  may include a directly-fed antenna resonating element such as inverted-F antenna resonating element  50 , an indirectly fed antenna resonating element such as slot-based indirectly-fed antenna element  54  (sometimes referred to herein as slot  54  or indirectly-fed slot  54 ), and ground structures such as antenna ground  52 . The conductive structures that form inverted-F antenna resonating element  50 , slot-based indirectly-fed antenna element  54 , and antenna ground  52  may be formed from conductive housing structures, from electrical device components in device  10 , from printed circuit board traces, from strips of conductor such as strips of wire and metal foil, or other conductive structures. 
     As shown in  FIG. 4 , transceiver circuitry  90  may be coupled to antenna  40  using transmission line structures  92  that include positive transmission line conductor  94  and ground transmission line conductor  96 . 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  of antenna feed  110 . Circuits such as impedance matching circuits, filters, switches, duplexers, diplexers, and other circuitry may, if desired, be interposed in transmission line path  92 . 
     Antenna resonating element  50  may include one or more inverted-F antenna resonating element arms such as arms  106  and  108  (e.g., resonating element  50  may be a dual band inverted-F antenna resonating element). Arms  106  and  108  may, for example, extend from opposing sides of antenna feed  110 . A short circuit (return) path such as short circuit path  104  may couple resonating element arms  106  and  108  to antenna ground  52 . Arms  106  and  108  of resonating element  50  may be separated from antenna ground  52  by a dielectric-filled opening such as dielectric gap  101 . Gap  101  may be formed using air, plastic, and/or other dielectric materials that separate the conductive material in arms  106  and  108  from ground  52 . Short circuit path  104  may be coupled between arms  106  and  108  and ground  52  in parallel with feed  110 , for example. In one suitable arrangement, arms  106  and  108  of resonating element  50  may be formed from a segment of peripheral conductive housing structures  16  extending between two peripheral dielectric gaps  18  ( FIG. 1 ) whereas antenna ground  52  is formed from conductive portions of housing  12  (e.g., portions of a rear wall of housing  12  and portions of peripheral conductive housing structures  16  that are separated from arms  106  and  108  by peripheral gaps  18 ). 
     The lengths of arms  106  and  108  may be selected to allow antenna  40  to support communications in one or more desired frequency bands. For example, the length of each arm may be approximately equal to one-quarter of the corresponding wavelength of operation. Arms  106  and  108  may have different lengths to support different frequencies of operation. In the example of  FIG. 4 , arm  108  is longer than arm  106  and may therefore support lower frequencies than arm  106  (e.g., arm  106  may sometimes be referred to herein as high band or midband arm  106  whereas arm  108  is sometimes referred to herein as low band arm  108 ). As an example, arm  108  may support an antenna resonance in a cellular low band (LB) between 700 MHz and 960 MHz or other suitable frequencies whereas arm  106  supports an antenna resonance in cellular midband and/or high band (HB). The example of  FIG. 4  is merely illustrative. If desired, arm  106  may be longer than arm  108  or arms  106  and  108  may have the same length. Resonating element arms  106  and  108  may have one or more bends or may follow any desired paths (e.g., paths having curved and/or straight segments). 
     Inverted-F antenna resonating element arms  106  and  108  may be directly fed using feed terminals  98  and  100  (e.g., transmission line  92  may contact feed terminals  98  and  100  and may convey antenna currents that flow over arms  106  and  108  via feed terminal  98 ). If desired, antenna  40  may include one or more antenna resonating elements that are not directly fed (i.e., one or more indirectly fed antenna resonating elements). For example, antenna  40  may include an indirectly fed antenna element such as slot-based indirectly fed antenna element  54 . Slot-based indirectly fed antenna element  54  may be coupled to antenna resonating element  50  by near field electromagnetic coupling and may be used to modify the frequency response of antenna  40  so that antenna  40  operates at desired frequencies. 
     Slot-based element  54  may support a resonance of antenna  40  in one or more desired frequency bands. The length or perimeter of slot-based element  54  may be selected to resonate in one or more desired frequency bands. In one suitable arrangement, slot-based element  54  may support a resonance in a frequency band that is not covered by arms  106  and  108  of inverted-F antenna resonating element  50 . For example, slot-based element  54  may have an elongated length that is selected to support a resonance in an ultra-high band between 3400 MHz and 3700 MHz (e.g., a length between 10 mm and 15 mm, between 5 mm and 20 mm, between 1 mm and 15 mm, etc.). 
     In order to minimize the amount of space required to implement antenna  40  within device  10 , slot-based element  54  may handle antenna signals that are conveyed over transmission line  92  and feed  110  of inverted-F antenna resonating element  50  (e.g., without requiring a separate feed and transmission line directly connected to slot-based element  54 ). In this example, slot-based element  54  may be indirectly-fed by inverted-F antenna resonating element  50  via near field electromagnetic coupling. For example, while a fundamental mode of low band arm  108  may support resonance in low band LB, a harmonic mode of low band arm  108  may near field couple to slot-based element  54  to induce antenna currents to flow around the perimeter of slot-based element  54  within the ultra-high band between 3400 MHz and 3700 MHz. 
     In the example of  FIG. 4 , slot-based indirectly fed antenna element  54  is based on a slot antenna structure. Slot antenna structures may include open slot structures (i.e., slots with one open end and one closed end) and closed slot structures (i.e., slots that are completely surrounded by metal). Slots for a slot-based indirectly fed antenna element may be formed between metal structures in antenna resonating element  50  and/or antenna ground  52 . Plastic, air, and/or other dielectric materials may fill the slot. 
     If desired, the frequencies supported by slot-based indirectly fed antenna element  54  may be adjusted using adjustable circuitry (e.g., adjustable circuitry including one or more tunable components  102  of  FIG. 3 ). The adjustable circuitry for controlling the resonance of slot-based indirectly fed antenna element  54  may be adjusted (tuned) using control signals  112  generated by control circuitry  28  ( FIG. 2 ) or any other desired control circuitry. By tuning the adjustable circuitry associated with slot-based indirectly fed antenna element  54  using control signals  112 , antenna  40  may be tuned to cover different operating frequencies of interest. 
     If desired, tuning circuitry  114  (e.g., circuitry including one or more tunable components  102  of  FIG. 3 ) may be coupled between antenna resonating element  50  and ground  52 . As shown in  FIG. 4 , tuning circuitry  114  includes an adjustable inductor coupled between antenna resonating element  50  and antenna ground  52  (i.e., adjustable inductor  114  may bridge gap  101 ). Adjustable inductor  114  may exhibit an inductance value that is adjusted in response to control signals  116  received from control circuitry  28 . Adjustable inductor  114  may be adjusted to tune the frequency response of antenna resonating element  50 . The example of  FIG. 4  is merely illustrative. If desired, multiple adjustable circuits  114  (e.g., adjustable inductors) may be coupled between resonating element  50  and ground  52  and/or between different portions of resonating element  50 . 
       FIG. 5  is a diagram showing how antenna  40  having dual-arm inverted-F antenna resonating element  50  and slot-based indirectly-fed antenna resonating element  54  may be formed using conductive portions of housing  12 . As shown in  FIG. 5 , gap  101  (sometimes referred to herein as slot  101 ) may have an elongated shape extending between peripheral conductive structures  16  and ground  52 . Slot  101  may be filled with dielectric material such as air and/or plastic. For example, plastic may be inserted into portions of slot  101  and this plastic may be flush with the outside of housing  12 . 
     Arms  106  and  108  of inverted-F antenna resonating element  50  may be formed using a segment of peripheral conductive structures  16  that extends between two peripheral gaps  18  (e.g., a first peripheral gap  18 - 1  and a second peripheral gap  18 - 2 ). Feed  110  may be coupled across slot  101  (e.g., positive antenna feed terminal  98  may be coupled to peripheral conductive structures  16  whereas ground antenna feed terminal  100  is coupled to ground plane  52 ). One or more return paths for inverted-F antenna resonating element  50  such as path  104  of  FIG. 4  may be formed using a fixed conductive path bridging slot  101  or using adjustable components such as adjustable components  120 ,  122 , and/or  124 . Adjustable components  120 ,  122 , and  124  may sometimes be referred to herein as tuning components, tunable components, tuning circuits, tunable circuits, or adjustable tuning components (e.g., components  120 ,  122 , and  124  may be formed using tunable circuits  102  of  FIG. 3 ). 
     In the example of  FIG. 5 , adjustable component  120  bridges slot  101  at a first location along slot  101  (e.g., component  120  may be coupled between terminal  126  on ground plane  52  and terminal  128  on peripheral conductive structures  16 ). Adjustable component  122  may bridge slot  101  at a second location along slot  101  (e.g., component  122  may be coupled between terminal  130  on ground plane  52  and terminal  132  on peripheral conductive structures  16 ). Adjustable component  124  may bridge slot  101  at a third location along slot  101  (e.g., component  124  may be coupled between terminal  134  on ground plane  52  and a terminal  136  on peripheral conductive structures  16 ). Terminal  130  may be interposed between ground antenna feed terminal  100  and terminal  126  on ground plane  52 . Terminal  132  may be interposed between positive antenna feed terminal  98  and terminal  128  on peripheral conductive structures  16 . Ground antenna feed terminal  100  may be interposed between terminal  130  and terminal  134  on ground plane  52 . Positive antenna feed terminal  98  may be interposed between terminal  132  and terminal  136  on peripheral conductive structures  16 . 
     Antenna  40  may include an adjustable matching network such as adjustable matching circuitry  140  that is interposed on transmission line path  92  ( FIGS. 3 . and  4 ). Control circuitry  28  ( FIG. 2 ) may provide control signals to adjust matching circuitry  140  (e.g., to provide a selected matching impedance between transmission line  92  and antenna feed  110 ). If desired, impedance sensing circuitry such as coupler circuitry (e.g., a directional coupler or other radio-frequency coupler) may be used to tap antenna signals flowing to and from antenna  40 . The tapped antenna signals from the coupler circuitry may be conveyed to control circuitry  28  over a feedback path and may be used to determine the impedance (e.g., phase and magnitude data) of antenna  40  during operation of wireless circuitry  34 , if desired. 
     Adjustable matching circuitry  140  may include switching circuitry and circuit components such as resistive, capacitive, and/or inductive components coupled in any desired manner between transmission line  92 , ground  52 , antenna feed  110 , and/or peripheral conductive structure  16 . The switching circuitry in adjustable matching circuitry  140  may be controlled to place circuitry  140  in one of any desired number of states. Matching circuitry  140  may exhibit different impedances in each of the states. For example, matching circuitry  140  may have a first state at which matching circuitry  140  exhibits a first impedance and a second state at which matching circuitry exhibits a second impedance. This is merely illustrative and, in general, any desired components may be formed in matching network  140  to adjust the impedance in any desired manner. 
     Components  120 ,  122 , and  124  may include switches coupled to fixed components such as inductors for providing adjustable amounts of inductance or an open circuit between ground  52  and peripheral conductive structures  16 . Components  120 ,  122 , and  124  may also include fixed components that are not coupled to switches (e.g., capacitor  144 ) or a combination of components that are coupled to switches and components that are not coupled to switches. These examples are merely illustrative and, in general, components  120 ,  122 , and  124  may include other components such as adjustable return path switches, switches coupled to capacitors, or any other desired components. 
     Adjustable component  120  may include one or more inductors coupled to a radio-frequency switching circuit. In one illustrative example, adjustable component  120  may include two inductors coupled in parallel between terminals  126  and  128 . A radio-frequency switching circuit may selectively couple the inductors between terminals  126  and  128 . Adjustable component  122  may include one or more inductors coupled to a radio-frequency switching circuit. In one illustrative example, adjustable component  122  may include four inductors coupled in parallel between terminals  130  and  132 . A radio-frequency switching circuit may selectively couple the inductors between terminals  130  and  132 . Adjustable component  124  may include a radio-frequency switching circuit such as switch  150 . A first inductor  146  and a second inductor  148  may be coupled in parallel between terminal  136  and switch  150 . A capacitor  144  may also be coupled between terminals  134  and  136 . 
     Using multiple adjustable components at different locations along slot  101  may provide antenna  40  with flexibility to accommodate different loading conditions (e.g., different loading conditions that may arise due to the presence of a user&#39;s hand or other external object on various different portions of device  10  adjacent to various different corresponding portions of antenna  40 ). 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. Adjustable components  120 ,  122 , and  124 , and matching circuitry  140  may be controlled (i.e., placed in a desired state) using control signals received from control circuitry  28 . For example, component  122  may be adjusted to tune the response of antenna  40  within the low band, component  124  may be adjusted to tune the response of antenna  40  within the midband, and component  120  may be adjusted to account for different antenna loading conditions (e.g., different loading conditions that may arise due to the presence of a user&#39;s hand or other external object adjacent to different locations on device). 
     Slot  101  may have an elongated shape. In the example of  FIG. 5 , slot  101  has a U shape that runs along the periphery of device  10  between peripheral conductive structures  16  (e.g., housing sidewalls) and other conductive portions of device  10  (e.g., ground  52 ). The ends of slot  101 , which may sometimes be referred to as open ends, may be formed by gaps  18  (e.g., gaps  18 - 1  and  18 - 2  of  FIG. 5 ). The length of slot  101  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. Slot  101  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. In the example of  FIG. 5 , slot  101  has a U shape. If desired, slot  101  may have other shapes. 
     As shown in  FIG. 5 , in some configurations, an additional slot  162  may be formed in ground plane  52  (e.g., ground  52  may define at least three edges of slot  162 ). Slot  162  may have a width  176  and an elongated length  178  that is greater than width  176 . Slot  162  may extend from an end of slot  101 . For example, slot  162  may be aligned with gap  18 - 2  and may have the same width as gap  18 - 2  if desired. Slot  162  may have any desired width  176  (e.g., about 2 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, more than 0.5 mm, more than 1.5 mm, more than 2.5 mm, 1-3 mm, etc.). Length  178  of slot  162  may, for example, extend perpendicular to width  176  from an end of slot  101  to an opposing end defined by ground plane  52 . Slot  162  may have any desired length  178  (e.g., 10-15 mm, more than 5 mm, more than 10 mm, more than 15 mm, more than 30 mm, less than 30 mm, less than 20 mm, less than 15 mm, less than 10 mm, between 5 and 20 mm, etc.). 
     Slot  162  may form indirectly-fed slot antenna resonating element  54 . Slot  162  may therefore contribute to the frequency response of antenna  40 . Length  178  and width  176  of slot  162  (i.e., the perimeter of slot  162 ) may be selected so that slot  162  supports desired operating frequencies. For example, in scenarios where length  178  is sufficiently greater than width  176 , length  176  may be selected to be approximately equal to one-half of the desired wavelength of operation (e.g., a wavelength corresponding to an ultra-high band frequency) given the dielectric loading conditions at slot  162 . In the example of  FIG. 5 , slot  162  is an open slot having an open end defined by an end of slot  101  and gap  18 - 2 . This is merely illustrative and, if desired, slot  162  may be implemented using a closed slot that is surrounded by ground plane  52 . 
     In one suitable arrangement, inverted-F antenna resonating element  50  may support a resonance at low band (LB) frequencies (e.g., 700-960 MHz), midband (MB) frequencies (e.g., 1710-2170 MHz), and high band (HB) frequencies (e.g., 2170-2700 MHz). For example, the length of low band arm  108  may be selected to support a resonance at the low band frequencies (e.g., in a fundamental mode of arm  108 ) whereas the length of midband arm  106  may be selected to support a resonance at the midband frequencies. If desired, a harmonic mode of arm  108  may support a resonance in a portion of the high band frequencies (e.g., from approximately 2170-2400 MHz). Inverted-F antenna resonating element  50  may be directly fed using antenna feed  110  to cover these frequencies of operation. 
     The harmonic mode of arm  108  may induce antenna currents around the perimeter of slot  162  via near field electromagnetic coupling at the operating frequency associated with slot  162  (e.g., as defined by the perimeter of slot  162 ). For example, the harmonic mode of arm  108  may induce antenna currents at slot  162  at ultra-high band (UHB) frequencies (e.g., frequencies from 3400-3700 MHz). In this way, slot  162  may be induced to exhibit a resonance in the ultra-high band for antenna  40 . 
     In some scenarios, the harmonic mode of low band arm  108  may not be capable of providing satisfactory coverage of the upper end of the high band HB (e.g., at frequencies from approximately 2400-2700 MHz). In order to cover the entirety of the high band (e.g., including frequencies up to 2700 MHz), tuning circuits such as adjustable circuitry  165  may be coupled across slot  162 . 
     As shown in  FIG. 5 , adjustable circuitry  165  may include inductive, switching, and/or capacitive components such as inductor  168 , switching circuit  164 , and capacitor  166 . Inductor  168  may be coupled between terminals  170  and  172  on ground  52 . Terminals  170  and  172  may be coupled to ground  52  on opposing sides of slot  162 . Inductor  168  may be, for example, a fixed inductor having a fixed inductance value. Inductor  168  may serve to pull some of the antenna current induced at slot  162  to adjust the resonant frequency of the slot to a higher frequency than would otherwise be present in the absence of inductor  168  (e.g., to a frequency in the ultra-high band between 3400 and 3700 MHz). Capacitor  166  and radio-frequency switching circuit  164  may be coupled in series between terminals  172  and  170  (in parallel with inductor  168 ). Switching circuit  164  may be toggled to couple or decouple capacitor  166  between terminals  170  and  172 . When capacitor  166  is also coupled across slot  162 , the capacitor may effectively nullify at least a portion of the inductance of inductor  168 . By lowering the effective inductance across slot  162  when capacitor  166  is coupled across slot  162 , the resonant frequency of slot  162  may be shifted from the ultra-high band to the upper end of the high band (e.g., to frequencies between approximately 2400 and 2700 MHz). In this way, antenna  40  may be controlled to cover the entirety of the high band from 2170 MHz to 2700 MHz even if the harmonic mode of low band arm  108  is unable to cover the upper end of the high band. As examples, inductor  168  may exhibit an inductance of approximately 10 nH, between 8 nH and 12 nH, between 5 nH and 15 nH, or other desired inductances. Capacitor  166  may exhibit a capacitance of 0.5 pF, between 0.3 and 0.7 pF, between 0.1 and 0.9 pF, or other desired capacitances, as examples. 
     Switching circuit  164  may include any desired switches. For example, switching circuit  164  may include a single-pole single-throw switch coupled between terminal  170  and capacitor  166 . In a first state, the single-pole single-throw switch may be open and capacitor  166  may be decoupled from terminal  170 . In a second state, the single-pole single-throw switch may be closed to couple capacitor  166  to terminal  170  in parallel with inductor  168 . In the first state, the slot resonance of slot  162  may be at a given frequency (e.g., in the ultra-high band), whereas in the second state, the slot resonance may be at a lower frequency (e.g., in the high band). This example is merely illustrative and, if desired, other switch arrangements may be used. 
     Terminals  170  and  172  coupled to ground plane  52  may sometimes be referred to herein as ground or grounding terminals. If desired, one or both of terminals  170  and  172  may be coupled to antenna ground  52  (e.g., to conductive portions of housing  12 ) using conductive fasteners such as screws. The conductive fasteners may, if desired, be shared with other components in device  10 . For example, the conductive fasteners may be used to short other components to ground  52  and/or to mechanically secure the components to ground  52 . Sharing the conductive fasteners between antenna  40  and the other components may optimize space consumption within device  10 , for example. 
     In the example of  FIG. 5 , a shared conductive fastener may short both ground terminal  172  associated with adjustable component  165  of indirectly-fed slot element  162  and electronic component  174  to ground  52 . The shared conductive fastener may also serve to mechanically secure adjustable component  165  and electronic component  174  to ground  52  (e.g., to a conductive wall of housing  12 ). Electronic component  174  may be any desired component in electronic device  10 . For example, electronic component  174  may be an input-output device such as a sensor, speaker, microphone, button, or status indicator, may be a shielding structure, a conductive portion of display  14 , a portion of transceiver circuitry  90 , or any other desired component. In one suitable arrangement, electronic component  174  may include circuitry for providing haptic feedback for a user such as a motor or vibrator. This example is merely illustrative and, if desired, the conductive fasteners used to short terminals  172  and  170  to ground  52  may be shared between two or more components or may be unshared, if desired. 
     The shapes and dimensions of slot  162 , ground  52 , and slot  101  in  FIG. 5  are merely illustrative. If desired the slots can have multiple segments extending in different angles/directions, may include straight and/or curved edges, and may in general have any desired shape. Similarly, ground  52  may include any desired conductive structures and may have any desired shape. 
       FIG. 6  is a diagram showing the current distribution on antenna  40  associated with the resonance of slot  162  in the ultra-high band (e.g., 3500 MHz or 3400 to 3700 MHz). In the example of  FIG. 6 , the adjustable circuitry of  FIG. 5  is not shown for the sake of clarity. 
     As shown in  FIG. 6 , directly-fed antenna currents  180  may flow over arms  106  and  108  of inverted-F antenna resonating element  50  and ground plane  52  (i.e., antenna currents corresponding to radio-frequency antenna signals conveyed directly to antenna resonating element  50  over transmission line  92  and feed  110 ). Antenna currents  180  at harmonic frequencies of low band arm  106  may induce indirectly-fed antenna currents  180 ′ on ground plane  52  around the perimeter of slot  162  (e.g., via near field electromagnetic coupling). Antenna currents  180 ′ may flow around slot  162  at frequencies within the ultra-high band (e.g., between 3400 MHz and 3700 MHz). At frequencies within the ultra-high band (e.g., at 3500 MHz), there may be a relatively high density of antenna currents  180 ′ within region  182  of ground plane  52  around slot  162 . In this way, slot  162  may contribute to the coverage of antenna  40  within the ultra-high band. 
       FIG. 7  is a graph of antenna performance (antenna efficiency) as a function of frequency for an illustrative antenna of the type shown in  FIGS. 5 and 6 . As shown in  FIG. 7 , antenna  40  may exhibit resonances in a low band LB, midband MB, high band HB, and ultra-high band UHB. This example is merely illustrative and, if desired, antenna  40  may exhibit resonances in a subset of these bands and/or in additional bands (e.g., a low-middle band LMB extending from 1400 MHz to 1710 MHz or other suitable frequency ranges). 
     Low band LB may extend from 700 MHz to 960 MHz or another suitable frequency range. Tunable components such as components  120 ,  122 ,  124 , and/or matching circuitry  140  may be used to tune the response of antenna  40  in low band LB. As shown in  FIG. 7 , antenna  40  may have an antenna efficiency characterized by curve  184  in low band LB. The antenna efficiency of curve  184  may be achieved by tuning antenna  40  to place antenna  40  in one of four or more tuning states (e.g., a first state characterized by curve  186 , a second state characterized by curve  188 , a third state characterized by curve  190 , a fourth state characterized by curve  192 , etc.). For example, adjustable component  122  may include four inductors with each state associated with one of the inductors being coupled between terminals  130  and  132 . 
     Midband MB may extend from 1710 MHz to 2170 MHz or another suitable frequency range. Tunable components such as components  120 ,  122 ,  124 , and/or matching circuitry  140  may be used to tune the response of antenna  40  in midband MB. As shown in  FIG. 7 , antenna  40  may have an antenna efficiency characterized by curve  194  in midband MB. The antenna efficiency of curve  194  may be achieved by tuning antenna  40  to place antenna  40  in one of two or more tuning states (e.g., a first state characterized by curve  196 , a second state characterized by curve  198 , etc.). For example, coupling inductor  146  of  FIG. 5  between terminals  134  and  136  may place the antenna in the first tuning state, whereas coupling inductor  148  of  FIG. 5  between terminals  134  and  136  may place the antenna in the second tuning state. 
     High band HB may extend from 2170 MHz to 2700 MHz or another suitable frequency range. Ultra-high band UHB may extend from 3400 MHz to 3700 MHz or another suitable frequency range. As shown in  FIG. 7 , antenna  40  may have an antenna efficiency characterized by curves  200 ,  202 , and  204  in high band HB and curve  206  in ultra-high band UHB. The antenna efficiency of curves  200  and  206  may be achieved by tuning antenna  40  to place antenna  40  in one of two or more tuning states (e.g., a first state characterized by curve  204 , a second state characterized by curve  206 , etc.). For example, coupling capacitor  166  of  FIG. 5  between terminals  170  and  172  using switch  164  may place the antenna in the first tuning state (with improved antenna performance in high band HB as characterized by curve  204 ). In the first tuning state, the harmonic mode of low band arm  108  covers frequencies shown by curve  202  and the resonant frequency of slot  162  covers frequencies shown by curve  204  so that antenna  40  collectively exhibits response  200 . Opening switch  164  so that only inductor  168  (and not capacitor  166 ) is coupled between terminals  170  and  172  may place the antenna in the second tuning state (with improved antenna performance in ultra-high band UHB as characterized by curve  206 ). In the second tuning state, the harmonic mode of low band  108  covers frequencies shown by curve  202  and the resonant frequency of slot  162  covers frequencies shown by curve  206 . 
     If desired, adjustable component  165  for slot  162  may be formed on a substrate such as a flexible printed circuit board.  FIG. 8  is a diagram showing how adjustable component  165  may include a flexible printed circuit board that bridges slot  162 . As shown in  FIG. 8 , adjustable component  165  may be formed on a flexible printed circuit board such as flexible printed circuit board  220 . Flexible printed circuit board  220  may be a printed circuit formed from sheets of polyimide or other flexible polymer layers. Flexible printed circuit board  220  may include patterned metal traces for carrying signals between components on the flexible printed circuit board. If desired, the patterned metal traces may form grounding pads to be coupled to additional conductive components within electronic device  10 . 
     Flexible printed circuit board  220  may be coupled between two ground terminals (e.g., terminals  170  and  172 ). Ground terminals  170  and  172  may be formed from any desired components. For example, ground terminal  170  may include a conductive structure  228  whereas ground terminal  172  includes a conductive structure  222 . Conductive structures  228  and  222  may include conductive traces on flexible printed circuit board  220 , conductive contact pads on flexible printed circuit board  220 , conductive brackets, metal support plates or stiffeners, and/or other conductive structures. Flexible printed circuit board  220  may be fastened or attached to housing  12  or other structures using one or more conductive fasteners such as fasteners  224  and  230 . Fastener  224  may include a conductive screw, conductive pin, conductive clip, conductive spring, conductive bracket, or other conductive fastener that extends through an opening in flexible printed circuit to attach the flexible printed circuit to antenna ground  52  (e.g., to a conductive portion of housing  12 ). Fastener  230  may include a conductive screw, conductive pin, conductive clip, conductive spring, conductive bracket, or other conductive fastener that extends through an opening in conductive structure  228  to attach the flexible printed circuit to antenna ground  52  (e.g., to a conductive portion of housing  12 ). Fastener  230  may mechanically secure conductive structure  228  to ground plane  52  (e.g., a conductive portion of housing  12 ). Conductive structure  228  may electrically couple trace  226  (e.g., trace portion  226 - 4 ) on flexible printed circuit  220  to fastener  230 , thereby electrically coupling trace  226  to ground. If desired, fastener  230  may also be used to short and/or mechanically secure other electronic components such as component  174  of  FIG. 5  to ground  52 . 
     Trace  226  may include trace portions  226 - 1 ,  226 - 2 ,  226 - 3 , and  226 - 4  and may be formed on flexible printed circuit  220 . First trace portion  226 - 1  may be coupled to ground via conductive structure  222  and fastener  224 . Portions  226 - 2  and  226 - 3  may extend in parallel from portion  226 - 1 . Portion  226 - 2  may bypass switch  164  and couple portion  226 - 1  to inductor  168  (e.g., without any intervening components). Because portion  226 - 2  is not coupled to switch  164 , inductor  168  may always be connected across slot  162 . Portion  226 - 3 , on the other hand, is coupled to capacitor  166  through switch  164 . In a first state, switch  164  may connect capacitor  166  across slot  162 . In a second state, switch  166  may be open and capacitor  166  is disconnected across slot  162 . By switching capacitor  166  on and off, the resonance of antenna  40  may be tuned (e.g., to cover a portion of high band HB or ultra-high band UHB as shown in  FIG. 7 ). 
     If desired, flexible printed circuit  220  may be bent about bend axis  232 . The bend in flexible printed circuit  220  may result in a first portion ( 220 - 1 ) of the flexible printed circuit being bent at an angle relative to the second portion ( 220 - 2 ) of the flexible printed circuit. First portion  220 - 1  of the flexible printed circuit may be bent at an angle of approximately 90° or another desired angle relative to second portion  220 - 2  of the flexible printed circuit. In one illustrative embodiment, portion  220 - 1  of flexible printed circuit  220  may be positioned adjacent to a peripheral conductive structure (e.g., peripheral conductive structure  16  in  FIG. 5 ) that forms a sidewall for the electronic device. The example of  FIG. 8  where flexible printed circuit  220  is bent around one bend axis (i.e., axis  232 ) is merely illustrative. If desired, flexible printed circuit  220  may have two or more bends around two or more bend axes. Alternatively, flexible printed circuit  220  may be unbent if desired. 
       FIG. 9  is a perspective view of electronic device  10  showing how flexible printed circuit  220  may bridge slot  162 . As shown in  FIG. 9 , antenna ground  52  may include a conductive portion  236  of housing  12 . Conductive housing portion  236  may, for example, form a conductive support plate or wall (e.g., a conductive backplate or rear housing wall) for device  10 . Conductive housing portion  236  may, if desired, extend across the width of device  10  (e.g., between two opposing sidewalls formed by peripheral housing structures  16 ). If desired, conductive housing portion  236  and the opposing sidewalls of device  10  may be formed from a single integral piece of metal or portion  236  may otherwise be shorted to the opposing sidewalls of device  10 . Conductive housing portion  236  may form an exterior rear surface of device  10  or may be covered with a dielectric layer  238  such as a thin glass, sapphire, ceramic, or sapphire layer or other dielectric coating. In scenarios where layer  238  is formed, layer  238  may form the exterior rear surface of device  10  and may or may not serve to hide conductive housing portion  236  from the view of the user. Fasteners  224 ,  230 , and  234  may be screws or other fasteners (e.g., conductive adhesive, conductive clips, conductive springs, clips, etc.) that are attached to threaded openings, holes, or other structures on conductive housing portion  236 . 
     As shown in  FIG. 9 , peripheral dielectric gap  18 - 2  may be filled with a dielectric  240  such as plastic. Capacitor  166  and inductor  168  on flexible printed circuit  168  may be aligned with slot  162  in conductive housing portion  236  and gap  18 - 2  in peripheral conductive structures  16  (e.g., capacitor  166  and inductor  168  may overlap slot  162  and/or gap  18 - 2  when circuit board  220  is mounted or assembled in device  10 ). Flexible printed circuit  220  may be bent around bend axis  232  such that first portion  220 - 1  of flexible printed circuit  220  (a portion on which capacitor  166  and inductor  168  are formed) is positioned in the Y-Z plane and second portion  220 - 2  of flexible printed circuit  220  (a portion on which switch  164  is formed) is positioned in the X-Y plane. 
     Fastener  224  may couple second flexible printed circuit portion  220 - 2  to conductive housing portion  236  whereas fastener  230  may couple first flexible printed circuit portion  220 - 1  to conductive housing portion  236 . As shown in  FIG. 9 , trace  226 - 4  of flexible printed circuit  220  may be coupled to conductive structure  228  (e.g., a metal bracket or clip). Fastener  230  may pass through an opening in bracket  228  and an opening in a portion of component  174  to reach conductive housing portion  236 . Fastener  230  may be coupled to a bracket portion of electronic component  174  that both grounds component  174  and attaches component  174  to conductive housing portion  236 , for example. If desired, additional fasteners such as fastener  234  may attach an additional bracket portion of electronic component  174  to conductive housing portion  236 . 
     The example of  FIGS. 6 and 8  in which adjustable circuitry  165  includes a series-coupled switch  164  and capacitor  166  coupled in parallel with inductor  168  between terminals  170  and  172  is merely illustrative. If desired, other arrangements may be used to form adjustable circuitry  165 .  FIGS. 10A and 10B  are circuit diagrams of illustrative switching arrangements that may be used to form adjustable component  165  across slot  162 . 
     As shown in  FIG. 10A , if desired, capacitor  166  may be implemented as a bypass capacitor coupled between ground terminals  170  and  172 . In this arrangement, inductor  168  may be a switchable inductor formed using switch  164  coupled in series with inductor  168  terminals  170  and  172  and in parallel with capacitor  166 . In this arrangement, capacitor  166  is always coupled across slot  162 . Capacitor  166  may serve to adjust the resonant frequency of slot  162  to a lower frequency than would otherwise be supported in the absence of capacitor  166 . For example, antenna  40  may be configured to resonate in the high band (e.g., from 2300 to 2700 MHz) when capacitor  166  is coupled across slot  162 . When switch  164  is closed and inductor  168  is also coupled across slot  162 , the inductor may effectively nullify at least a portion of the capacitance of capacitor  166 . By lowering the effective capacitance across slot  162 , the resonant frequency of slot  162  may be raised from the high band to the ultra-high band (e.g., to frequencies from 3400 to 3700 MHz). 
     As shown in  FIG. 10B , if desired, adjustable circuit  165  may include inductor  168  and switch  164  coupled in series between terminals  170  and  172  across slot  162  (e.g., without any capacitors). In this embodiment, when switch  164  is closed, the length of slot  162  is effectively shortened from L to L′. This may serve to increase the frequency coverage of slot  162  (e.g., from frequencies within high band HB to frequencies within ultra-high band UHB). 
     The examples of  FIGS. 10A and 10B  are merely illustrative. The components of adjustable circuit  165  may be arranged in any desired manner between terminals  170  and  172 . If desired, adjustable circuit  165  may include one or more (e.g., a network) of discrete components such as surface mount technology capacitors and inductors and/or may include distributed capacitances and inductances. 
     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: 20170908
Publication Date: 20181218
Grant Date: 20181218
Priority Date: 20170908
Inventors: YARGA, SALIH
GAO, XU
ATMATZAKIS, GEORGIOS
HAN, XU
AVSER, BILGEHAN
XU, HAO
ZHOU, YIJUN
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0483", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/106", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0458", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/0483", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 64604848