PATENT DOCUMENT

Publication Number: US-10978806-B2
Application Number: US-201816141793-A
Country: US
Kind Code: B2

Title: Electronic device slot antennas

Abstract:
An electronic device may be provided an antenna, a display, and a housing. The display may include a conductive display structure and a cover layer. The housing may include peripheral conductive structures and a conductive rear wall. The peripheral structures may include a ledge separated from the conductive display structure by a gap. The peripheral structures and the rear wall may define opposing edges of a slot element for the antenna. Conductive bridging structures may be coupled between the conductive display structure and the ledge across the gap. The bridging structures may at least partially overlap locations along the length of the slot element where antenna currents around the slot element exhibit a maximum magnitude. The bridging structures may align the phase of current induced on the ledge with the phase of the current induced on the conductive display structure to maximize antenna efficiency through the cover layer.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a conductive housing; 
 a display having a conductive display structure and a display cover layer, wherein the display cover layer overlaps the conductive display structure and is mounted to the conductive housing; 
 a gap that separates the conductive housing from the conductive display structure; 
 an antenna having a slot element and an antenna feed coupled across the slot element, wherein the slot element is configured to convey radio-frequency signals through the gap and the display cover layer; and 
 a conductive bridging structure coupled between the conductive housing and the conductive display structure across the gap, wherein the conductive bridging structure at least partially overlaps the slot element. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the slot element has a first edge and the conductive bridging structure at least partially overlaps the first edge. 
     
     
       3. The electronic device defined in  claim 2 , wherein the slot element has a second edge opposite the first edge, a third edge extending between the first and second edges, and a fourth edge opposite the third edge that extends between the first and second edges, the antenna feed being coupled to the third and fourth edges. 
     
     
       4. The electronic device defined in  claim 3 , wherein the conductive housing comprises peripheral conductive housing structures that define the third edge of the slot element and a conductive rear housing wall that defines the fourth edge of the slot element. 
     
     
       5. The electronic device defined in  claim 4 , wherein the slot element has a length extending between the first and second edges that is approximately equal to one-half of a wavelength in a wireless local area network communications band. 
     
     
       6. The electronic device defined in  claim 3 , further comprising:
 an additional conductive bridging structure coupled between the conductive housing and the conductive display structure across the gap, wherein the additional conductive bridging structure at least partially overlaps the second edge of the slot element. 
 
     
     
       7. The electronic device defined in  claim 2 , wherein the antenna comprises a tuning element coupled across the slot element at a given location along a length of the slot element, the electronic device further comprising:
 an additional conductive bridging structure coupled between the conductive housing and the conductive display structure, wherein the additional conductive bridging structure is aligned with the given location along the length of the slot. 
 
     
     
       8. The electronic device defined in  claim 7 , wherein the additional conductive bridging structure comprises a conductive bridging structure selected from the group consisting of: a conductive clip and a conductive air loop gasket. 
     
     
       9. The electronic device defined in  claim 1 , wherein the conductive housing comprises peripheral conductive housing structures extending around a periphery of the electronic device, the peripheral conductive housing structures comprise a ledge, the display cover layer is mounted to the ledge, and the conductive bridging structure is coupled to the ledge. 
     
     
       10. The electronic device defined in  claim 9 , wherein a portion of the conductive bridging structure is interposed between the ledge and the display cover layer. 
     
     
       11. The electronic device defined in  claim 9 , wherein the conductive bridging structure comprises a conductive structure selected from the group consisting of: conductive tape, a conductive gasket, a conductive spring, a conductive wire, and conductive foam. 
     
     
       12. The electronic device defined in  claim 1 , wherein the electronic device has opposing front and rear faces, the display cover layer is formed at the front face, and the slot element is formed at the rear face. 
     
     
       13. An electronic device comprising:
 an antenna resonating element having a length; 
 an antenna feed coupled to the antenna resonating element and configured to convey an antenna current over the length of the antenna resonating element; 
 a first conductive structure; 
 a second conductive structure separated from the first conductive structure by a gap, wherein the antenna resonating element is configured to convey radio-frequency signals associated with the antenna current through the gap; and 
 a third conductive structure coupled between the first and second conductive structures across the gap, wherein the third conductive structure at least partially overlaps a location along the length of the antenna resonating element where the antenna current exhibits a maximum magnitude. 
 
     
     
       14. The electronic device defined in  claim 13 , wherein the antenna resonating element is configured to induce a first current on the first conductive structure and a second current on the second conductive structure, the third conductive structure being configured to align a phase of the first current with a phase of the second current. 
     
     
       15. The electronic device defined in  claim 13 , further comprising:
 peripheral conductive housing structures; and 
 a display having conductive display structures and a display cover layer, wherein the first conductive structure comprises a ledge portion of the peripheral conductive housing structures, the display cover layer being mounted to the ledge portion of the peripheral conductive housing structures. 
 
     
     
       16. The electronic device defined in  claim 15 , wherein the conductive display structures comprise the second conductive structure. 
     
     
       17. The electronic device defined in  claim 16 , wherein the antenna resonating element comprises a slot antenna resonating element having a first edge defined by the peripheral conductive housing structures. 
     
     
       18. The electronic device defined in  claim 17 , further comprising:
 a conductive housing wall that defines a second edge of the slot antenna resonating element. 
 
     
     
       19. An electronic device comprising:
 peripheral conductive housing structures; 
 a conductive rear housing wall; 
 a slot element having opposing edges defined by the peripheral conductive housing structures and the conductive rear housing wall; 
 an antenna feed coupled to the peripheral conductive housing structures and the conductive rear housing wall across the slot element; 
 an antenna tuning element coupled between the peripheral conductive housing structures and the conductive rear wall across the slot element; 
 a display having a display cover layer and conductive display structures, wherein the display cover layer is mounted to the peripheral conductive housing structures and overlaps the slot element, the conductive housing wall, and the conductive display structures; and 
 a conductive structure coupled between the conductive display structures and the conductive rear housing wall, wherein the conductive structure is aligned with the antenna tuning element. 
 
     
     
       20. The electronic device defined in  claim 19 , wherein the slot element is configured to induce a first current on the peripheral conductive housing structures and a second current on the conductive display structures, the conductive structure being configured to align a phase of the first current with a phase of the second current.

Description:
BACKGROUND 
     This relates to electronic devices, and more particularly, to antennas for electronic devices with wireless communications circuitry. 
     Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components using compact structures. At the same time, there is a desire for wireless devices to cover a growing number of communications bands. 
     Because antennas have the potential to interfere with each other and with components in a wireless device, care must be taken when incorporating antennas into an electronic device. Moreover, care must be taken to ensure that the antennas and wireless circuitry in a device are able to exhibit satisfactory performance over a range of operating frequencies in one or more directions with satisfactory efficiency bandwidth. 
     It would therefore be desirable to be able to provide improved wireless communications circuitry for wireless electronic devices. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry, a conductive housing, and a display. The display may include a conductive display structure and a display cover layer that overlaps the conductive display structure. The conductive housing may include peripheral conductive housing structures and a conductive rear housing wall. The peripheral conductive housing structures may include a ledge separated from the conductive display structure by a gap. The display cover layer may be mounted to the ledge using adhesive. 
     The wireless circuitry may include one or more antennas such as a wireless local area network antenna. The peripheral conductive housing structures and the conductive rear housing wall may define opposing edges of an antenna resonating element such as a slot element for the antenna. The slot element may convey radio-frequency signals through the rear face of the device. The slot element may also convey radio-frequency signals through the gap and the display cover layer. If care is not taken, the slot element may induce out-of-phase currents on the conductive display structure and the ledge that limit efficiency for the antenna through the display cover layer. 
     In order to mitigate these effects, one or more conductive bridging structures may be coupled between the conductive display structure and the ledge across the gap. The conductive bridging structures may at least partially overlap locations along the length of the slot element where antenna currents around the slot element exhibit a maximum magnitude. For example, the conductive bridging structures may overlap one or more edges of the slot element. If desired, the conductive bridging structures may be coupled to the conductive rear housing wall at a location aligned with an antenna tuning element that is coupled across the slot element. The conductive bridging structures may serve to align the phase of the current induced on the ledge with the phase of the current induced on the conductive display structure to maximize antenna efficiency through the display cover layer. 
    
    
     
       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 communications circuitry in accordance with an embodiment. 
         FIG. 4  is a diagram of illustrative slot antenna structures in accordance with an embodiment. 
         FIG. 5  is a rear view of an illustrative electronic device having slot antennas formed from conductive housing structures in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view showing how illustrative conductive bridging structures may overlap a slot antenna to optimize radio-frequency performance through a display in accordance with an embodiment. 
         FIG. 7  is a top-down view showing how illustrative bridging structures may overlap different locations along the length of a slot antenna in accordance with an embodiment. 
         FIG. 8  is a top-down view of illustrative bridging structures coupled to a conductive housing wall within gaps in a layer of pressure-sensitive adhesive in accordance with an embodiment. 
         FIG. 9  is a plot of antenna performance (antenna efficiency) as a function of frequency for an antenna of the type shown in  FIGS. 3-7  in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device such as electronic device  10  of  FIG. 1  may be provided with wireless circuitry that includes antennas. The antennas may be used to transmit and receive wireless signals. 
     The wireless circuitry of device  10  may handle one or more communications bands. For example, the wireless circuitry of device  10  may include a Global Position System (GPS) receiver that handles GPS satellite navigation system signals at 1575 MHz or a GLONASS receiver that handles GLONASS signals at 1609 MHz. Device  10  may also contain wireless communications circuitry that operates in communications bands such as cellular telephone bands and wireless circuitry that operates in communications bands such as the 2.4 GHz Bluetooth® band and the 2.4 GHz and 5 GHz Wi-Fi® wireless local area network bands (sometimes referred to as IEEE 802.11 bands or wireless local area network communications bands). Device  10  may also contain wireless communications circuitry for implementing near-field communications at 13.56 MHz or other near-field communications frequencies. If desired, device  10  may include wireless communications circuitry for communicating at 60 GHz, circuitry for supporting light-based wireless communications, or other wireless communications. 
     The wireless communications circuitry may include antenna structures. The antenna structures may include antennas for wireless local area network communications and/or other far-field (non-near-field) communications. The antenna structures may include loop antenna structures, inverted-F antenna structures, strip antenna structures, planar inverted-F antenna structures, slot antenna structures, hybrid antenna structures that include antenna structures of more than one type, or other suitable antenna structures. Conductive structures for the antenna structures may, if desired, be formed from conductive electronic device structures. 
     The conductive electronic device structures may include conductive housing structures. The conductive housing structures may include peripheral structures such as peripheral conductive structures that run around the periphery of the 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, a wireless access point, wireless base station, an electronic device incorporated into a kiosk, building, or vehicle, 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 substantially planar housing wall such as rear housing wall  12 R (e.g., a planar housing wall). Rear housing wall  12 R may have slots that pass entirely through the rear housing wall and that therefore separate portions of housing  12  from each other. Rear housing wall  12 R may include conductive portions and/or dielectric portions. If desired, rear housing wall  12 R may include a planar metal layer covered by a thin layer or coating of dielectric such as glass, plastic, sapphire, or ceramic. Housing  12  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). 
     Housing  12  may include peripheral housing structures such as peripheral structures  12 W. Peripheral structures  12 W and rear housing wall  12 R may sometimes be referred to herein collectively as conductive structures of housing  12 . Peripheral structures  12 W 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, peripheral structures  12 W may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges and that extend from rear housing wall  12 R to the front face of device  10  (as an example). Peripheral structures  12 W or part of peripheral structures  12 W 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 ) if desired. Peripheral structures  12 W may, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral structures  12 W 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, peripheral conductive sidewalls, peripheral conductive sidewall structures, conductive housing sidewalls, peripheral conductive housing sidewalls, sidewalls, sidewall structures, or a peripheral conductive housing member (as examples). Peripheral conductive housing structures  12 W 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 conductive housing structures  12 W. 
     It is not necessary for peripheral conductive housing structures  12 W to have a uniform cross-section. For example, the top portion of peripheral conductive housing structures  12 W may, if desired, have an inwardly protruding lip that helps hold display  14  in place. The bottom portion of peripheral conductive housing structures  12 W may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). Peripheral conductive housing structures  12 W 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 conductive housing structures  12 W serve as a bezel for display  14 ), peripheral conductive housing structures  12 W may run around the lip of housing  12  (i.e., peripheral conductive housing structures  12 W may cover only the edge of housing  12  that surrounds display  14  and not the rest of the sidewalls of housing  12 ). 
     If desired, rear housing wall  12 R may be formed from a metal such as stainless steel or aluminum and may sometimes be referred to herein as conductive rear housing wall  12 R or conductive rear wall  12 R. Conductive rear housing wall  12 R may lie in a plane that is parallel to display  14 . In configurations for device  10  in which rear housing wall  12 R is formed from metal, it may be desirable to form parts of peripheral conductive housing structures  12 W as integral portions of the housing structures forming the conductive rear housing wall of housing  12 . For example, conductive rear housing wall  12 R of device  10  may be formed from a planar metal structure and portions of peripheral conductive housing structures  12 W on the sides of housing  12  may be formed as flat or curved vertically extending integral metal portions of the planar metal structure (e.g., housing structures  12 R and  12 W may be formed from a continuous piece of metal in a unibody configuration). 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 . Conductive rear housing wall  12 R may have one or more, two or more, or three or more portions. Peripheral conductive housing structures  12 W and/or the conductive rear housing wall  12 R 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  12 W and/or  12 R 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 . For example, active area AA may include an array of display pixels. The array of pixels may be formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels or other light-emitting diode pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. If desired, active area AA may include touch sensors such as touch sensor capacitive electrodes, force sensors, or other sensors for gathering a user input. 
     Display  14  may have an inactive border region that runs along one or more of the edges of active area AA. Inactive area IA may be free of pixels for displaying images and may overlap circuitry and other internal device structures in housing  12 . To block these structures from view by a user of device  10 , the underside of the display cover layer or other layers in display  14  that overlap inactive area IA may be coated with an opaque masking layer in inactive area IA. The opaque masking layer may have any suitable color. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, transparent ceramic, sapphire, or other transparent crystalline material, or other transparent layer(s). The display cover layer may have a planar shape, a convex curved profile, a shape with planar and curved portions, a layout that includes a planar main area surrounded on one or more edges with a portion that is bent out of the plane of the planar main area, or other suitable shapes. The display cover layer may cover the entire front face of device  10 . In another suitable arrangement, the display cover layer may cover substantially all of the front face of device  10  or only a portion of the front face of device  10 . Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button. An opening may also be formed in the display cover layer to accommodate ports such as speaker port  8  or a microphone port. Openings may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.) and/or audio ports for audio components such as a speaker and/or a microphone if desired. 
     Display  14  may include a display module having 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 peripheral conductive structures  12 W). 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  16  and  20 , openings may be formed within the conductive structures of device  10  (e.g., between peripheral conductive housing structures  12 W and opposing conductive ground structures such as conductive portions of conductive rear housing wall  12 R, 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  16  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  16 . 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  16 ), thereby narrowing the slots in regions  20  and  16 . 
     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 within regions  20  and  16  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 conductive housing structures  12 W may be provided with peripheral gap structures. For example, peripheral conductive housing structures  12 W may be provided with one or more gaps such as gaps  18 , as shown in  FIG. 1 . The gaps in peripheral conductive housing structures  12 W may be filled with dielectric such as polymer, ceramic, glass, air, other dielectric materials, or combinations of these materials. Gaps  18  may divide peripheral conductive housing structures  12 W into one or more peripheral conductive segments. There may be, for example, two peripheral conductive segments in peripheral conductive housing structures  12 W (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 ), six peripheral conductive segments (e.g., in an arrangement with six gaps  18 ), etc. The segments of peripheral conductive housing structures  12 W 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 conductive housing structures  12 W 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 structures 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  16 . 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, near-field communications, etc. 
     In order to provide an end user of device  10  with as large of a display as possible (e.g., to maximize an area of the device used for displaying media, running applications, etc.), it may be desirable to increase the amount of area at the front face of device  10  that is covered by active area AA of display  14 . Increasing the size of active area AA may reduce the size of inactive area IA within device  10 . This may reduce the area of regions  20  and  16  that is available for forming antennas within device  10 . In general, antennas that are provided with larger operating volumes or spaces may have higher bandwidth efficiency than antennas that are provided with smaller operating volumes or spaces. If care is not taken, increasing the size of active area AA may reduce the operating space available to the antennas, which can undesirably inhibit the efficiency bandwidth of the antennas (e.g., such that the antennas no longer exhibit satisfactory radio-frequency performance). It would therefore be desirable to be able to provide antennas that occupy a small amount of space within device  10  (e.g., to allow for as large of a display active area AA as possible) while still allowing the antennas to operate with optimal efficiency bandwidth. 
     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 Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol or other wireless personal area network protocols, cellular telephone protocols, multiple-input and multiple-output (MIMO) protocols, antenna diversity protocols, near-field communications (NFC) protocols, etc. 
     Input-output circuitry  22  may include input-output devices  24 . Input-output devices  24  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  24  may include user interface devices, data port devices, and other input-output components. 
     Input-output devices  24  may include display components such as display  14 . Display  14  may include a display cover layer such as display cover layer  26  and a display module such as display module  30 . Display module  30  may include active circuitry such as pixel circuitry, touch sensor circuitry, and/or force sensor circuitry. Display cover layer  26  may overlap display module  30 . Display module  30  may emit image light through display cover layer  26  and may receive user input through display cover layer  26 . Display module  30  may, for example, form active area AA of display  14  ( FIG. 1 ). 
     Display module  30  may include conductive display structures such as conductive display structures  32 . Conductive display structures  32  may include a conductive frame for the active components of display module  30 , conductive layers in the display module (e.g., a conductive backplate for the display module or conductive layers embedded within the dielectric layers of the display module), conductive shielding structures, ground layers in display module  30 , and/or other conductive structures in display module  30 . If desired, conductive display structures  32  may include portions of the pixel circuitry, touch sensor circuitry, force sensor circuitry, and/or other components in display module  30 . Conductive display structures  32  may include conductive portions of display  14  that are not a part of display module  30  if desired. Conductive display structures  32  may laterally extend across active area AA of  FIG. 1 . As active area AA of display  14  is maximized, the space within device  10  occupied by display module  30  and conductive display structures  32  is also maximized, thereby limiting the amount of space available within device  10  for forming other component such as antennas. 
     Input-output devices  24  of  FIG. 2  may include other input-output components. For example, input-output devices  24  may include 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), etc. 
     Input-output circuitry  22  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  44  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  42 . Transceiver circuitry  38  may handle wireless local area network (WLAN) bands such as 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications and/or wireless personal area network (WPAN) bands such as the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use remote wireless transceiver circuitry  42  such as cellular telephone transceiver circuitry 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 2300 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  42  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 satellite navigation receive equipment such as global positioning system (GPS) receiver circuitry  36  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data (e.g., Global Navigation Satellite System (GLONASS) signals, etc.). In Wi-Fi® 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  44  in wireless communications circuitry  34  may be coupled to a given antenna  40  using paths such as path  50 . Wireless communications circuitry  34  may be coupled to storage and processing circuitry  28 . Storage and processing circuitry  28  may be coupled to input-output devices  24 . Input-output devices  24  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  40  with the ability to cover communications frequencies of interest, antenna  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  40  may be provided with adjustable circuits such as tunable components  46  to tune the antenna over communications bands of interest. Tunable components  46  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  46  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 , storage and processing circuitry  28  may issue control signals on one or more paths such as path  48  that adjust inductance values, capacitance values, or other parameters associated with tunable components  46 , thereby tuning antenna  40  to cover desired communications bands. 
     Path  50  may include one or more transmission lines. As an example, path  50  of  FIG. 3  may be a radio-frequency transmission line having a positive signal conductor such as conductor  52  and a ground signal conductor such as conductor  54 . Transmission line structures used to form path  50  (sometimes referred to herein as transmission lines  50  or radio-frequency transmission lines  50 ) may include parts of a coaxial cable, a stripline transmission line, microstrip transmission line, coaxial probes realized by metalized vias, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, waveguide structures, transmission lines formed from combinations of transmission lines of these types, etc. 
     Transmission lines in device  10  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, transmission lines in device  10  may also include transmission line conductors (e.g., signal and ground conductors) integrated within multilayer laminated structures (e.g., layers of a conductive material such as copper and a dielectric material such as a resin that are laminated together without intervening adhesive) that may be folded or bent in multiple dimensions (e.g., two or three dimensions) and that maintain a bent or folded shape after bending (e.g., the multilayer laminated structures may be folded into a particular three-dimensional shape to route around other device components and may be rigid enough to hold its shape after folding without being held in place by stiffeners or other structures). All of the multiple layers of the laminated structures may be batch laminated together (e.g., in a single pressing process) without adhesive (e.g., as opposed to performing multiple pressing processes to laminate multiple layers together with adhesive). 
     A matching network (e.g., an adjustable matching network formed using tunable components  46 ) may include components such as inductors, resistors, and capacitors used in matching the impedance of antenna  40  to the impedance of transmission line  50 . 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  40  and may be tunable and/or fixed components. 
     Transmission line  50  may be coupled to antenna feed structures associated with antenna  40 . As an example, antenna  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed  55  with a positive antenna feed terminal such as terminal  56  and a ground antenna feed terminal such as terminal  58 . Positive transmission line conductor  52  may be coupled to positive antenna feed terminal  56  and ground transmission line conductor  54  may be coupled to ground antenna feed terminal  58 . Other types of antenna feed arrangements may be used if desired. For example, antenna  40  may be fed using multiple feeds (e.g., switchable feeds where a selected feed may be switched into use at any given time). The illustrative feeding configuration of  FIG. 3  is merely illustrative. In scenarios where electronic device  10  includes multiple antennas  40 , each antenna  40  may include its own antenna feed  55  and a corresponding transmission line  50 , for example. 
     Storage and processing circuitry  28  may use information from a proximity sensor, 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 a speaker, 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, storage and processing circuitry  28  may adjust an adjustable inductor, adjustable capacitor, switch, or other tunable component  46  and/or may switch one or more antennas  40  into or out of use to ensure that wireless communications circuitry  34  operates as desired. 
     The presence or absence of external objects such as a user&#39;s hand may affect antenna loading and therefore antenna performance. Antenna loading may differ depending on the way in which device  10  is being held. For example, antenna loading and therefore antenna performance may be affected in one way when a user is holding device  10  in a portrait orientation and may be affected in another way when a user is holding device  10  in a landscape orientation. To accommodate various loading scenarios, device  10  may use sensor data, antenna measurements, information about the usage scenario or operating state of device  10 , and/or other data from input-output devices  24  to monitor for the presence of antenna loading (e.g., the presence of a user&#39;s hand, the user&#39;s head, or another external object). Device  10  (e.g., storage and processing circuitry  28 ) may then adjust tunable components  46  in antenna  40  and/or may switch other antennas into or out of use to compensate for the loading (e.g., multiple antennas  40  may be operated using a diversity protocol to ensure that at least one antenna  40  may maintain satisfactory communications even while the other antennas are blocked by external objects). 
     In the example of  FIG. 3 , a single antenna is shown. When operating using a single antenna, a single stream of wireless data may be conveyed between device  10  and external communications equipment (e.g., one or more other wireless devices such as wireless base stations, access points, cellular telephones, computers, etc.). This may impose an upper limit on the data rate (data throughput) obtainable by wireless communications circuitry  34  in communicating with the external communications equipment. As software applications and other device operations increase in complexity over time, the amount of data that needs to be conveyed between device  10  and the external communications equipment typically increases, such that a single antenna may not be capable of providing sufficient data throughput for handling the desired device operations. In order to increase the overall data throughput of wireless communications circuitry  34 , multiple antennas  40  may be operated using a multiple-input and multiple-output (MIMO) scheme. When operating using a MIMO scheme, two or more antennas on device  10  may be used to convey multiple independent streams of wireless data at the same frequencies. This may significantly increase the overall data throughput between device  10  and the external communications equipment relative to scenarios where only a single antenna is used. In general, the greater the number of antennas that are used for conveying wireless data under the MIMO scheme, the greater the overall throughput of circuitry  34 . 
     The radio-frequency performance of antenna  40  may be influenced by the presence of conductive structures in the vicinity of antenna  40 . For example, the presence of conductive display structures  32  in the vicinity of antenna  40  can block or otherwise deteriorate the radio-frequency performance of antenna  40  in one or more directions (e.g., a direction through display  14  of  FIG. 1 ). Conductive display structures  32  may have a particularly strong effect on the radio-frequency performance of antenna  40  as active area AA of display  14  ( FIG. 1 ) is increased, thereby minimizing the volume available for forming antennas  40 . 
     In order to minimize the electromagnetic influence of conductive display structures  32  on the radio-frequency performance of antenna  40 , one or more conductive bridging structures  60  may be used to electrically couple (e.g., ground) conductive display structures  32  to antenna  40 . For example, each bridging structure  60  may have a first terminal  62  coupled to antenna  40  and a second terminal  64  coupled to conductive display structures  32 . 
     Bridging structures  60  (sometimes referred to herein as conductive structures  60 , conductive bridging structures  60 , conductive grounding structures  60 , or grounding structures  60 ) may include conductive tape (e.g., a layer of copper, gold, or other metals provided with a layer of pressure sensitive adhesive on one or both faces), conductive foam, a conductive gasket (e.g., an air loop gasket), other conductive adhesives, conductive wire, sheet metal, conductive wire, conductive springs, solder, welds, conductive traces on an underlying substrate, conductive pins, combinations of these, and/or any other desired conductive structures. In scenarios where bridging structures  60  include conductive tape, the conductive tape may have an end that is wrapped (folded) around a layer of heat-activated film. 
     Operation of antenna  40  may induce current on conductive display structures  32 . Some current may leak across bridging structures  60  so that currents in the conductive structures of antenna  40  are in phase with the currents induced by antenna  40  on conductive display structures  32 . This may ground conductive display structures  32  (e.g., by coupling conductive display structures  32  to a ground potential through the conductive structures in antenna  40 ) and may serve to minimize the electromagnetic impact of conductive display structures  32  on the radio-frequency signals handled by antenna  40 . 
     An illustrative slot antenna structure that may be used for forming antenna  40  is shown in  FIG. 4 . As shown in  FIG. 4 , antenna  40  may include a conductive structure such as conductive structure  66  that has been provided with a dielectric-filled opening such as dielectric opening  68 . Openings such as opening  68  of  FIG. 4  are sometimes referred to as slots, slot elements, slot radiating elements, slot resonating elements, or slot antenna resonating elements of antenna  40 . In the configuration of  FIG. 4 , slot  68  is a closed slot, because portions of conductive structure  66  completely surround and enclose slot  68 . Open slot antenna structures may also be formed in conductive materials such as conductive structure  66  (e.g., by forming an opening in the right-hand or left-hand end of conductive structure  66  so that slot  68  protrudes through conductive structure  66 ). 
     Antenna feed  55  for antenna  40  may be formed using positive antenna feed terminal  56  and ground antenna feed terminal  58 . In general, the frequency response of an antenna is related to the size and shapes of the conductive structures in the antenna. Slot antenna structures of the type shown in  FIG. 4  tend to exhibit response peaks when slot perimeter P is equal to the wavelength of operation of the antenna (e.g. where perimeter P is equal to two times length L plus two times width W). Antenna currents may flow between antenna feed terminals  56  and  58  around perimeter P of slot  68 . 
     Antenna feed  55  may be coupled across slot  68  at a location along elongated length L. For example, antenna feed  55  may be located at a distance  70  from one side of slot  68 . Distance  70  may be adjusted to match the impedance of antenna  40  to the impedance of the corresponding transmission line (e.g., transmission line  50  of  FIG. 3 ). For example, the antenna current flowing around slot  68  may experience an impedance of zero at the left and right edges of slot  68  (e.g., a short circuit impedance) and an infinite (open circuit) impedance at the center of slot  68  (e.g., at a fundamental frequency of the slot). Antenna feed  55  may be located between the center of slot  68  and the left edge at a location where the antenna current experiences an impedance that matches the impedance of the corresponding transmission line (e.g., distance  70  may be between 0 and ¼ of the wavelength of operation of antenna structures  40 ). Distance  70  may, for example, be 9 mm, between 5 mm and 10 mm, between 2 mm and 12 mm, or any other suitable distance. Slot  68  may have a width W perpendicular to length L. 
     In scenarios where slot  68  is a closed slot, length L may be approximately equal to (e.g., within 15% of) one-half of a wavelength of operation of the antenna (e.g., a wavelength of a fundamental mode of the antenna). Harmonic modes of slot  68  may also be configured to cover desired frequency bands. In scenarios where slot  68  is an open slot, length L may be approximately equal to one-quarter of the wavelength of operation. The wavelength of operation may, for example, be an effective wavelength of operation based on the dielectric material within slot  68 . 
     The frequency response of slot  68  can be tuned using one or more tuning components (e.g., tunable components  46  of  FIG. 3 ). These components may have terminals that are coupled to opposing sides of slot  68  (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  68 . Combinations of these arrangements may also be used. Antenna  40  may sometimes be referred to herein as slot antenna  40 . 
     The example of  FIG. 4  is merely illustrative. In general, slot  68  may have any desired shape (e.g., where the perimeter P of slot  68  defines radiating characteristics of the antenna). For example, slot  68  may have a meandering shape with different segments extending in different directions, may have straight and/or curved edges, may have more than one open end, etc. Conductive structure  66  may be formed from any desired conductive electronic device structures. For example, conductive structure  66  may include conductive traces on printed circuit boards or other substrates, sheet metal, metal foil, conductive structures associated with display  14  ( FIG. 1 ), conductive portions of housing  12  (e.g., conductive structures  12 W and/or  12 R of  FIG. 1 ), and/or other conductive structures within device  10 . If desired, different sides (edges) of slot  68  may be defined by different conductive structures. In one suitable arrangement that is sometimes described herein as an example, one side of slot  68  may be formed from peripheral conductive structures  12 W ( FIG. 1 ) whereas the other side of slot  68  is formed from conductive rear housing wall  12 R. 
       FIG. 5  is a rear view of region  16  at the upper end of device  10 . As shown in  FIG. 5 , multiple antennas  40  such as a first antenna  40 - 1  and a second antenna  40 - 2  may be formed within region  16 . Each antenna may include a corresponding slot  68  that is fed using a corresponding antenna feed  55 . In the example of  FIG. 5 , antenna  40 - 1  includes slot  68 - 1  that is fed using antenna feed  55 - 1 . Antenna  40 - 2  includes slot  68 - 2  that is fed using antenna feed  55 - 2 . Slot  68 - 1  may be fed using antenna feed  55 - 1  at any desired location between edges (ends)  74  and  72  (e.g., at any desired location along the elongated length of slot  68 - 1 ). The locations of the positive and ground antenna feed terminals in antenna feed  55 - 1  may be swapped if desired. Similarly, slot  68 - 2  may be feed using antenna feed  55 - 2  at any location along its length and the positive and ground antenna feed terminals in antenna feed  55 - 2  may be swapped if desired. 
     As shown in  FIG. 5 , slots  68 - 1  and  68 - 2  each have a first edge (side) defined by peripheral conductive housing structures  12 W and an opposing second edge (side) defined by conductive rear housing wall  12 R. Slots  68 - 1  and  68 - 2  may be filled with dielectric material (e.g., dielectric material that lies flush with the rear exterior surface of device  10 ). Slots  68 - 1  and  68 - 2  may be covered by a dielectric cover layer (not shown) that obscures slots  68 - 1  and  68 - 2  from view if desired. Slots  68 - 1  and  68 - 2  may each include perpendicular portions to allow antennas  40 - 1  and  40 - 2  to cover relatively low frequencies while still fitting within the rear face of device  10 . In scenarios where slots  68 - 1  and  68 - 2  are open slots, one or both ends of each slot (e.g., end  74  of slot  68 - 1 ) may be continuous with a corresponding gap  18  ( FIG. 1 ) in peripheral conductive housing structures  12 W. 
     Antennas  40 - 1  and  40 - 2  may both cover the same radio-frequency communications bands if desired. For example, antennas  40 - 1  and  40 - 2  may both convey radio-frequency signals in one or more wireless local area network bands. A given one of antennas  40 - 1  and  40 - 2  may be switched into use at a given time (e.g., using an antenna diversity scheme) or both antennas  40 - 1  and  40 - 2  may be active at a given time (e.g., using a MIMO scheme). While the structures of antenna  40 - 1  are described in greater detail herein as an example, similar structures may also be used to form antenna  40 - 2  and/or any other desired antennas within device  10 . 
     As shown in  FIG. 5 , radio-frequency signals conveyed over antenna feed  55 - 1  may produce antenna currents I 1  and I 2  running around the periphery of slot  68 - 1 . Antenna currents I 1  and I 2  may generate corresponding radio-frequency signals that are radiated by antenna  40 - 1 . Similarly, radio-frequency signals received by antenna  40 - 1  may generate antenna currents I 1  and I 2  that are conveyed to transceiver circuitry  44  ( FIG. 3 ) over antenna feed  55 - 1 . The length of slot  68 - 1  (e.g., from end  74  to end  72 ) may define the frequencies of operation for antenna  40 . Radio-frequency signals conveyed by antenna  40  may propagate freely through the rear face of device  10  (e.g., due to the absence of other conductive structures over the rear face of device  10  within region  16 ). However, if care is not taken, conductive display structures  32  in display  14  ( FIG. 2 ) may block radio-frequency signals conveyed by antenna  40  from propagating freely through the front face of device  10 . 
       FIG. 6  is a cross-sectional side view of device  10  (e.g., as taken along line AA′ of  FIG. 5 ) showing how bridging structure  60  ( FIG. 3 ) may be used to optimize the radio-frequency performance of antenna  40 - 1  through display  14 . As shown in  FIG. 6 , display cover layer  26  may be mounted over conductive structures  32  in display  14 . Display cover layer  26  may be transparent and may be formed from any desired materials such as glass, plastic, or sapphire. Portions of display cover layer  26  may be provided with an opaque masking layer such as an ink layer if desired. 
     Display  14  may be mounted to peripheral conductive housing structures  12 W. Peripheral conductive housing structures  12 W may be separated from conductive rear housing wall  12 R by slot  68 - 1  in antenna  40 - 1 . Dielectric material such as dielectric  76  (e.g., plastic, ceramic, glass, or other dielectric material) may be placed within slot  68 - 1  and may lie flush with the outer surface of conductive rear housing wall  12 R. If desired, a dielectric cover layer such as a glass or ceramic layer (not shown) may cover the outer surfaces of conductive rear housing wall  12 R and dielectric  76 . In this way, peripheral conductive housing structures  12 W and conductive rear housing wall  12 R may define opposing sides of slot  68 - 1  for antenna  40 - 1 . 
     Peripheral conductive housing structures  12 W may have an inwardly-protruding portion (extension)  82  that is sometimes referred to herein as ledge  82  or datum  82 . Ledge  82  may have a lateral surface that extends parallel to inner surface  79  of display cover layer  26 . Display  14  may be secured to peripheral conductive housing structures  12 W by attaching (affixing) display cover layer  26  to ledge  82  using adhesive material. 
     Conductive display structures  32  may be separated from ledge  82  by gap  80 . Antenna  40  may transmit and receive radio-frequency signals through the rear face of device  10 , as shown by arrow  84 . In scenarios where gap  80  is suitably large, antenna  40  may freely transmit and receive radio-frequency signals through gap  80 . However, as the size of gap  80  is reduced (e.g., to maximize active area AA for display  14  as shown in  FIG. 1 ), the presence of conductive display structures  32  in the vicinity of slot  68 - 1  can serve to block radio-frequency signals from passing freely through gap  80 , as shown by arrow  86 . For example, radio-frequency signals generated by antenna  40  may induce current I 4  on ledge  82  and an opposing current I 3  on conductive display structures  32 . In the absence of grounding (bridging) structures for display  14 , current I 3  may be out of phase with current I 4  at one or more locations along the length of slot  68 - 1 . This may cause current I 3  to cancel out at least some of current I 4  on ledge  82 , which serves to deteriorate the efficiency and bandwidth of antenna  40  through the front face of device  10  (e.g., through gap  80  and display  14 ). 
     To minimize these effects and maximize antenna efficiency through gap  80 , bridging structure  60  may be coupled between peripheral conductive housing structures  12 W and conductive display structures  32  across gap  80 . For example, as shown in  FIG. 6 , bridging structure  60  may have a first terminal  62  coupled to ledge  82  and a second terminal  64  coupled to conductive display structures  32 . Some of the current produced by antenna  40  may pass between ledge  82  and conductive display structures  32  over bridging structure  60 , allowing current I 3  on conductive display structures  32  to be in phase with current I 4  on ledge  82 . This may serve to minimize the electromagnetic impact of conductive display structures  32  on the radio-frequency signals handled by antenna  40 , and may allow antenna  40  to convey the radio-frequency signals through gap  80  with maximum efficiency and bandwidth, as shown by arrow  88 . 
     In the example of  FIG. 6 , bridging structure  60  is coupled to an upper surface of ledge  82  (e.g., terminal  62  and a portion of bridging structure  60  may be interposed between ledge  82  and display cover layer  26 ). In this scenario, bridging structure  60  may include adhesive that helps to secure display cover layer  26  to ledge  82 . For example, the end of bridging structure  60  that includes terminal  62  may include conductive tape that is folded around a layer of heat-activated film. During assembly of display  14  to peripheral conductive housing structures  12 W, the heat-activated film may be heated and pressed down until exterior surface  81  of display cover layer  26  lies flush with the top surface of peripheral conductive housing structures  12 W. When cooled, the heat-activated film may hold display cover layer  26  in place while the conductive material in the conductive tape electrically couples ledge  82  to conductive display structures  32 . In this way, bridging structure  60  may be used both to electrically couple ledge  82  to conductive display structures  32  and to help adhere display cover layer  26  to peripheral conductive housing structures  12 W. 
     This example is merely illustrative. In general, bridging structure  60  may be coupled to any desired location on peripheral conductive housing structures  12 W. As another example, bridging structure  60  may be coupled to the bottom surface of ledge  82 , as shown by terminal  62 ′ and path  78 . In this scenario, bridging structure  60  may be formed from conductive foam or a conductive gasket that exerts a force upwards onto terminals  64  and  62 ′ (e.g., to help maintain reliable mechanical contact between the bridging structure, ledge  82 , and conductive display structures  32 ). Bridging structure  60  may include any other desired conductive structures that serve to align the phases of currents I 4  and I 3 . As yet another example, bridging structure  60  may be coupled to conductive rear housing wall  12 R within an inner region  77  located adjacent to (e.g., to the right of) slot  68 - 1 , as shown by terminal  62 ″ and path  75 . Region  77  may, for example, lie within a few millimeters of the edge of slot  68 - 1  (e.g., terminal  62 ″ may be offset with respect to slot  68 - 1  on conductive rear housing wall  12 R). In one suitable arrangement, region  77  and/or terminal  62 ″ may lie directly beneath terminal  64 . In scenarios where bridging structure  60  follows path  75 , bridging structure  60  may be formed from a conductive air loop gasket, a conductive clip (e.g., a clip that clips into an attachment structure at terminal  64 ), conductive springs, conductive pins, conductive adhesive, solder, and/or any other desired conductive structures. 
     Conductive bridging structures such as bridging structure  60  of  FIG. 6  may bridge gap  80  at one or more desired locations over slot  68 - 1  (e.g., bridging structures such as bridging structure  60  may overlap one or more portions of slot  68 - 1 ). Each bridging structure may be coupled to ledge  82  (e.g., at terminals such as terminals  62 ′ or  62 ), may each be coupled to conductive rear housing wall  12 R (e.g., at terminals such as terminal  62 ″), or different bridging structures may be coupled to different portions of housing  12  (e.g., some of the conductive bridging structures may be coupled to ledge  82  whereas other conductive bridging structures are coupled to conductive rear housing wall  12 R). Bridging gap  80  at multiple locations may, for example, allow the phase of current I 4  to be aligned with the phase of current I 3  across the entire length of slot  68 - 1 . However, care should be taken when placing the bridging structures over slot  68 - 1 . For example, if there are an excessive number of bridging structures overlapping slot  68 - 1 , the bridging structures, which include conductive material, may block radio-frequency signals from passing through gap  80  (e.g., efficiency losses from blocking may outweigh gains in efficiency due to aligning the phases of currents I 3  and I 4 ). In order to balance these factors to optimize antenna efficiency through gap  80 , bridging structures may be formed over slot  68 - 1  using an arrangement such as the arrangement shown in  FIG. 7 . 
       FIG. 7  is a top-down view of antenna  40  (e.g., as taken in the direction of arrow  90  of  FIG. 6 ) showing how multiple bridging structures may be used to bridge gap  80 . In the example of  FIG. 7 , display cover layer  26  ( FIG. 6 ) has been omitted, antenna feed  55 - 1  ( FIG. 5 ) has been omitted, and slot  68 - 1  is shown with a rectangular shape for the sake of clarity. In general, slot  68 - 1  may have any other desired shape (e.g., an L-shape as shown in  FIG. 5 ). 
     As shown in  FIG. 7 , slot  68 - 1  may have opposing first and second edges defined by peripheral conductive housing structures  12 W and conductive rear housing wall  12 R. The length of slot  68 - 1  between third and fourth edges  72  and  74  may define the radiating frequencies for antenna  40 - 1 . For example, the length of slot  68 - 1  between edges  74  and  72  may be approximately one-half of the wavelength of operation for antenna  40 - 1 . When antenna  40 - 1  is active, current I 4  may be induced in peripheral conductive housing structures  12 W whereas current I 3  is induced in conductive display structures  32 . Conductive display structures  32  may be laterally offset from the outline of slot  68 - 1  (as shown in  FIG. 7 ) or may partially overlap the lateral outline of slot  68 - 1 . 
     Curve  92  of  FIG. 7  illustrates the voltage V across the width of slot  68 - 1  at different points between edges  74  and  72 . As shown by curve  92 , voltage V is maximum (e.g., V=V MAX ) at the center of slot  68 - 1 . Voltage V is equal to zero at edges  74  and  72  (e.g., due to the short circuit impedance between rear housing wall  12 R and peripheral conductive housing structures  12 W). 
     Curve  94  illustrates the current I across the width of slot  68 - 1  at different points between edges  74  and  72 . As shown by curve  94 , current I across slot  68 - 1  is maximum (i.e., has a maximum magnitude |I|=I MAX ) at edges  74  and  72 . Current I may exhibit a minimum magnitude at the center of slot  68 - 1 . 
     Multiple bridging structures  60  such as a first bridging structure  60 - 1 , a second bridging structure  60 - 2 , and a third bridging structure  60 - 3  may be coupled between conductive display structures  32  and housing  12  (e.g., to either peripheral conductive housing structures  12 W across gap  80  or to rear housing wall  12 R beneath conductive structures  32 ). Each of the bridging structures coupled to peripheral conductive housing structures  12 W may at least partially overlap the underlying slot  68 - 1 . Bridging structures  60 - 1  and  60 - 3  may be coupled to peripheral conductive housing structures  12 W at respective terminals  62 - 1  and  62 - 3 . Bridging structure  60 - 2  may be coupled to rear housing wall  12 R at terminal  62 - 2  (e.g., at terminal  62 ″ of  FIG. 6 ). As shown in  FIG. 7 , bridging structures  60 - 1 ,  60 - 2 , and  60 - 3  may be coupled to conductive display structures  32  at respective terminals  64 - 1 ,  64 - 2 , and  64 - 3 . 
     Bridging structures  60 - 1 ,  60 - 2 , and  60 - 3  may have any desired width (e.g., parallel to the X-axis of  FIG. 7 ). Bridging structures  60 - 1 ,  60 - 2 , and  60 - 3  may each have the same width or two or more of these structures may have different widths. In the example of  FIG. 7 , bridging structures  60 - 2  and  60 - 3  are shown as having a greater width than bridging structure  60 - 1 . This is merely illustrative. In general, greater widths may allow the bridging structure to include more conductive adhesive that provides greater adhesion for display cover layer  26  ( FIG. 6 ) than thinner widths. At the same time, thinner widths may block fewer radio-frequency signals from propagating through gap  80  (e.g., parallel to the Z-axis) than greater widths. 
     In order to ensure that current I 4  is in phase with current I 3  (and thus that antenna  40  exhibits maximum efficiency through gap  80 ), the bridging structures may overlap slot  68  at locations where the magnitude of current I is maximum. In the example of  FIG. 7 , bridging structure  60 - 1  overlaps edge  74  and bridging structure  60 - 3  overlaps edge  72  of slot  68 - 1 , where current I exhibits maximum magnitude I MAX . In general, bridging structure  60 - 1  may at least partially overlap edge  74  (e.g., the entire width of bridging structure  60 - 1  may overlap slot  68 - 1  at edge  74 , part of the width of bridging structure  60 - 1  may overlap the conductive material defining edge  74  whereas part of the width overlaps slot  68 - 1 , or the entire width of bridging structure  60 - 1  may overlap the conductive material defining edge  74 ). Similarly, bridging structure  60 - 3  may at least partially overlap edge  72  (e.g., the entire width of bridging structure  60 - 3  may overlap slot  68 - 1  at edge  72 , part of the width of bridging structure  60 - 3  may overlap the conductive material defining edge  72  whereas part of the width overlaps slot  68 - 1 , or the entire width of bridging structure  60 - 3  may overlap the conductive material defining edge  72 ). Locating bridging structures  60 - 1  and  60 - 3  in this way may ensure that the bridging structures align the phases of currents I 4  and I 3  where currents I 4  and I 3  are most likely to exhibit a maximum magnitude, thereby resulting in a maximum increase in antenna efficiency through gap  80 . 
     In the example of  FIG. 7 , a tuning component such as tuning component  46  is coupled across the width of slot  68 - 1 . The impedance provided across slot  68 - 1  by tuning component  46  may alter the current across slot  68 - 1  such that induced currents I 4  and current I 3  may be slightly out of phase over the location of tuning component  46 . Bridging structure  60 - 2  may be aligned with tuning component  46  (relative to the length of slot  68 - 1 ) to align the phases of currents I 4  and I 3  at this location to further optimize antenna efficiency through gap  80 . Bridging structure  60 - 2  may be aligned with some or all of tuning component  46  (e.g., structure  60 - 2  may be aligned with terminal  95  of tuning component  46 , terminal  93  of tuning component  46 , and/or may be aligned with the active/passive circuitry within tuning component  46 ). 
     If desired, bridging structures  60  that overlap edges  74  and  72  of slot  68 - 1  such as bridging structures  60 - 1  and  60 - 3  of  FIG. 7  may be coupled to ledge  82  of peripheral conductive housing structures  12 W (e.g., at terminals  62  and/or  62 ′ of  FIG. 6 ) whereas bridging structures  60  that are aligned with tuning components  46  such as bridging structure  60 - 2  may be coupled to rear housing wall  12 R (e.g., at terminal  62 ″ of  FIG. 6 ). 
     In general, bridging structures  60  may overlap slot  68 - 1  (e.g., may be coupled to peripheral conductive housing structures  12 W) and/or may be coupled to rear housing wall  12 R (e.g., without overlapping slot  68 - 1 ) at any locations along the length of slot  68 - 1  where current I exhibits a maximum magnitude and at any locations along the length of slot  68 - 1  where tuning components such as tuning components  46  are formed. Bridging structures  60  may overlap locations along the length of slot  68 - 1  where current I exhibits a global maximum (e.g., edges  72  and  74 ) and/or a local maximum (e.g., due to harmonic modes of slot  68 - 1 ). In this way, bridging structures  60  may serve to align the phases of currents I 3  and I 4  along the entire length of slot  68 - 1  (thereby maximizing antenna efficiency) without significantly blocking radio-frequency signals from passing through gap  80 . 
     The example of  FIG. 7  is merely illustrative. Bridging structures  60  need not overlap every location where slot  68 - 1  exhibits a maximum current and need not overlap every location where tuning components are formed. One or more of bridging structures  60 - 1 ,  60 - 2 , and  60 - 3  of  FIG. 7  may be omitted if desired. Bridging structures  60  may overlap other portions of slot  68 - 1  if desired. 
     The ends of bridging structures  60 - 1 ,  60 - 2 , and/or  60 - 3  may, if desired, include adhesive material that is used to help attach display cover layer  26  ( FIG. 6 ) to peripheral conductive housing structures  12 W. Additional adhesive material such as pressure sensitive adhesive may be used to help secure display cover layer  26  to peripheral conductive housing structures  12 W.  FIG. 8  is a top-down view (e.g., as taken in the direction of arrow  90  of  FIG. 6 ) showing how two conductive bridging structures such as conductive bridging structures  60 - 1  and  60 - 3  of  FIG. 7  may be used to help secure display cover layer  26  ( FIG. 6 ) to peripheral conductive housing structures  12 W. In the example of  FIG. 8 , display cover layer  26  has been omitted for the sake of clarity. 
     As shown in  FIG. 8 , a layer of adhesive such as pressure sensitive adhesive  104  may be formed on ledge  82  of peripheral conductive housing structures  12 W. When display cover layer  26  is pressed onto ledge  82  during assembly, this pressure may activate pressure sensitive adhesive  104  to adhere display cover layer  26  to ledge  82 . Pressure sensitive adhesive  104  may include notches or gaps such as gaps  106 . End  96  of bridging structure  60 - 1  may be coupled to ledge  82  within a first notch  106  in pressure sensitive adhesive  104 . End  98  of bridging structure  60 - 3  may be coupled to ledge  82  within a second notch  106  in pressure sensitive adhesive  104 . End  100  of bridging structure  60 - 1  and end  102  of bridging structure  60 - 3  may be coupled to conductive display structures  32  (e.g., at terminals  64 - 1  and  64 - 3  of  FIG. 7 , respectively). 
     End  96  of bridging structure  60 - 1  and end  98  of bridging structure  60 - 3  may include adhesive that is used to help secure display cover layer  26  ( FIG. 6 ) to ledge  82 . If desired, end  96  of bridging structure  60 - 1  and end  98  of bridging structure  60 - 3  may each include conductive tape that is folded around a layer of heat-activated film. The heat-activated film may allow the display cover layer to be mounted flush with the top surface of peripheral conductive housing structures  12 W during assembly, for example. Similar structures may be used to form one or more (e.g., all) of the bridging structures  60  overlapping antenna  40 - 1 . 
       FIG. 9  is a graph in which antenna performance (antenna efficiency) through display  14  has been plotted as a function of operating frequency for antenna  40 - 1  of  FIGS. 5-7 . As shown in  FIG. 9 , curve  108  plots the antenna efficiency of the antenna  40 - 1  in the absence of display  14  (e.g., prior to mounting display  14  to peripheral conductive housing structures  12 W). As shown by curve  108 , antenna  40 - 1  may exhibit a relatively high efficiency across a corresponding frequency band from frequency F 1  to frequency F 2  (e.g., a wireless local area network band at 2.4 GHz). 
     Curve  110  plots the antenna efficiency for antenna  40 - 1  in the presence of display  14  (e.g., after mounting display  14  to peripheral conductive housing structures  12 W) and in the absence of bridging structures  60 . As shown by curve  110 , out-of-phase currents I 3  and I 4  on ledge  82  and conductive display structures  32  ( FIG. 7 ) may significantly reduce the efficiency of antenna  40 - 1  between frequencies F 1  and F 2 . 
     Curve  112  plots the antenna efficiency for antenna  40 - 1  when conductive display structures  32  are coupled to peripheral conductive housing structures  12 W using one or more bridging structures  60 . The presence of bridging structures  60  may align the phases of currents I 3  and I 4  to minimize the electromagnetic impact of conductive display structures  32  on the radio-frequency signals propagating through display  14 . This may serve to increase antenna efficiency between frequencies F 1  and F 2  relative to scenarios where bridging structures  60  are omitted from device  10 , as shown by arrow  114 . 
     The example of  FIG. 9  is merely illustrative. In practice, curves  108 ,  112 , and  110  may have different shapes. Antenna  40 - 1  may exhibit any desired number of response peaks in any desired frequency bands. Similar structures may be used to optimize antenna efficiency through display  14  for any desired antennas  40  in device  10 . 
     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: 20180925
Publication Date: 20210413
Grant Date: 20210413
Priority Date: 20180925
Inventors: Garrido Lopez, David
RAJAGOPALAN, HARISH
AZAD, Umar
GOMEZ ANGULO, RODNEY A.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/0407", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0407", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/103", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 69883842