PATENT DOCUMENT

Publication Number: US-8766858-B2
Application Number: US-87076610-A
Country: US
Kind Code: B2

Title: Antennas mounted under dielectric plates

Abstract:
Electronic devices are provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. The antenna structures may include antennas such as inverted-F antennas that contain antenna resonating elements and antenna ground elements. Antenna resonating elements may be formed from patterned conductive traces on substrates such as flex circuit substrates. Antenna ground elements may be formed from conductive device structures such as metal housing walls. Support and biasing structures such as dielectric support members and layer of foam may be used to support and bias antenna resonating elements against planar device structures. The planar device structures against which the antenna resonating elements are biased may be planar dielectric members such as transparent layers of display cover glass or other planar structures. Adhesive may be interposed between the planar structures and the antenna resonating elements.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display having a transparent planar display member through which the display presents images; 
 a patterned opaque masking layer on an inner surface of the transparent planar display member, wherein the patterned opaque masking layer is located along a peripheral portion of the transparent planar display member; and 
 an antenna having an antenna resonating element; 
 adhesive that is interposed between the antenna resonating element and the patterned opaque masking layer and that adheres the antenna resonating element to the inner surface; and 
 a conductive housing in which the display is mounted. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the conductive housing comprises a portion that forms an antenna ground element and wherein the antenna ground element forms part of the antenna. 
     
     
       3. The electronic device defined in  claim 2  further comprising a positive antenna feed terminal coupled to the antenna resonating element and a ground antenna feed terminal coupled to the conductive housing. 
     
     
       4. The electronic device defined in  claim 3  further comprising:
 a radio-frequency transceiver; and 
 a transmission line that is coupled between the radio-frequency transceiver and the positive and ground antenna feed terminals. 
 
     
     
       5. The electronic device defined in  claim 4  wherein the transmission line comprises portions of a flexible printed circuit substrate having at least one flexible polymer sheet and conductive traces. 
     
     
       6. The electronic device defined in  claim 5  wherein the antenna resonating element is formed from at least some of the conductive traces of the flexible printed circuit. 
     
     
       7. The electronic device defined in  claim 6  wherein the conductive housing comprises metal housing walls. 
     
     
       8. The electronic device defined in  claim 7  further comprising biasing structures that bias the antenna resonating element towards the inner surface. 
     
     
       9. The electronic device defined in  claim 8  wherein the biasing structures include a layer of foam. 
     
     
       10. The electronic device defined in  claim 1  further comprising:
 a metal housing structure that forms an antenna ground element for the antenna; and 
 biasing and support structures that are interposed between the metal housing structure and the antenna resonating element and that press the antenna resonating element against the inner surface. 
 
     
     
       11. The electronic device defined in  claim 10  wherein the biasing and support structures include a dielectric support structure that supports the antenna resonating element and a layer of foam that biases the antenna resonating element towards the inner surface. 
     
     
       12. The electronic device defined in  claim 11  wherein the transparent planar display member comprises a layer of display cover glass, wherein the opaque masking layer comprises black ink, and wherein the antenna comprises an inverted-F antenna. 
     
     
       13. Apparatus, comprising:
 an antenna; 
 an antenna resonating element for the antenna; 
 a metal electronic device housing that forms an antenna ground element for the antenna; 
 a planar dielectric member having a planar surface; and 
 a layer of adhesive that attaches the antenna resonating element to the planar surface of the planar dielectric member. 
 
     
     
       14. The apparatus defined in  claim 13  wherein the planar dielectric member comprises a rectangular display cover glass member. 
     
     
       15. The apparatus defined in  claim 14  further comprising an opaque masking layer that is interposed between the planar surface and the layer of adhesive. 
     
     
       16. The apparatus defined in  claim 15  further comprising a conductive cavity for the antenna, wherein the conductive cavity has edges located at the planar surface. 
     
     
       17. An electronic device, comprising:
 a display having a planar display member with an exposed exterior surface and an interior surface; 
 conductive housing wall structures; 
 an inverted-F antenna having an antenna resonating element that is fed by a positive antenna feed terminal and having an antenna ground element that is formed from the conductive housing wall structures and that is fed by a ground antenna feed terminal; and 
 support and biasing structures that are interposed between the conductive housing wall structures and the planar display member and that bias the antenna resonating element against the interior surface, wherein the antenna resonating element comprises a flex circuit antenna resonating element having at least one flexible polymer sheet with patterned conductive traces and wherein the support and biasing structures include a layer of foam that presses the flex circuit antenna resonating element against the interior surface. 
 
     
     
       18. The electronic device defined in  claim 17  further comprising:
 a layer of adhesive interposed between the antenna resonating element and the interior surface.

Description:
BACKGROUND 
     This relates generally to wireless communications, and, more particularly, to wireless electronic devices and antenna structures for wireless electronic devices. 
     Electronic devices such as cellular telephones, portable music players, and computers contain wireless communications circuitry. For example, electronic devices may have antennas for handling wireless communications in cellular telephone bands and communications bands associated with wireless local area networks. 
     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, it may be desirable to include conductive structures in an electronic device such as metal device housing components. Because conductive components can affect radio-frequency performance, care must be taken when incorporating antennas into an electronic device that includes conductive structures. 
     It would therefore be desirable to be able to provide improved ways in which to incorporate antennas into electronic devices. 
     SUMMARY 
     Electronic devices may be provided with wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. The antenna structures may include antennas such as inverted-F antennas that contain antenna resonating elements and antenna ground elements. 
     Antenna resonating elements may be formed from patterned conductive traces on substrates such as flex circuit substrates. Antenna ground elements may be formed from conductive device structures such as metal housing walls. Radio-frequency transceiver circuits, displays, and other device components may be mounted within the metal housing walls. 
     A display may have a rectangular outline. The outermost layer of the display may be formed from a transparent rectangular display member such as a layer of cover glass. An array of image pixel elements may be used to display an image on the display through the layer of cover glass. The image may be displayed in an active portion of the display such as a central rectangular region. Peripheral portions of the display such as the edges of the transparent rectangular display member may be inactive. A layer of opaque masking material such as a layer of patterned black ink may be provided on the underside of the transparent rectangular display member to block interior device components from view. 
     Antenna structures may be mounted in a device so that radio-frequency signals can be transmitted and received through planar dielectric structures. The planar dielectric structures may be housing structures such as dielectric housing plates. The planar dielectric structures may also be associated with display structures. For example, the planar dielectric structures may be transparent rectangular display members. An antenna that is formed from an antenna resonating element and an antenna ground that is formed from metal housing walls may, for example, be mounted on the interior surface of a transparent rectangular display member. The antenna may be mounted in the inactive portion of the display, so that the antenna resonating element is located under the opaque masking layer. 
     An antenna resonating element may be mounted in an electronic device using support and biasing structures. The support and biasing structures may include dielectric support members such as polymer support structures. The support and biasing structures may also include flexible structures that force the antenna resonating element against the inner surface of the transparent display member. The biasing structures may be formed from foam or other structures that impart outwards force on the antenna resonating element. 
     A layer of adhesive may be interposed between an antenna resonating element and the inner surface of a display cover glass or other planar dielectric member. The layer of adhesive may be used to attach the antenna resonating element to the display cover glass or other dielectric member. 
     An antenna in an electronic device may have a conductive cavity. The conductive cavity may be formed from a metal can or other conductive structure. Support and biasing structures may be used to force the edges of the conductive cavity against the inner surface of a planar dielectric member. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a handheld electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a portable computer with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an illustrative electronic device that includes a display and wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 4  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional diagram of an electronic device in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of an illustrative antenna that may be used in a wireless electronic device in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of an antenna mounted adjacent to a planar dielectric layer in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional side view of the antenna of  FIG. 7  showing how there is a potential for air gaps to form between portions of the antenna and the planar dielectric layer if care is not taken when mounting the antenna. 
         FIG. 9  is a graph showing how the frequency response of an antenna such as the antenna of  FIG. 7  may shift if gaps of the type shown in  FIG. 8  develop during operation of an electronic device. 
         FIG. 10  is a cross-sectional side view of a portion of an electronic device showing how structures such as biasing and support structures may be used in mounting an antenna behind a planar dielectric structure in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional side view of a portion of an electronic device showing how an antenna may be mounted behind a planar dielectric layer using a support structure on a device housing and a biasing structure such as a foam structure that is interposed between the support structure and the antenna in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of a portion of an electronic device showing how an antenna may be mounted behind a planar dielectric layer using a support structure that supports the antenna and using a biasing structure such as a foam structure that is interposed between the support structure and a device housing in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional side view of a portion of an electronic device showing how an antenna may be mounted behind a planar dielectric layer using a biasing structure such as a foam structure that is interposed between the antenna and a device housing in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional side view of a portion of an electronic device showing how an antenna and a conductive cavity structure for the antenna may be mounted behind a planar dielectric layer using biasing structures that are interposed between the cavity structure and the antenna in accordance with an embodiment of the present invention. 
         FIG. 15  is a perspective view of an illustrative conductive cavity structure that may be used for the antenna of  FIG. 14  in accordance with an embodiment of the present invention. 
         FIG. 16  is a cross-sectional side view of an illustrative electronic device in which an antenna has been mounted under a planar dielectric layer such as a planar transparent display cover glass layer with peripheral opaque masking layer regions in accordance with an embodiment of the present invention. 
         FIG. 17  is a top view of an electronic device of the type shown in  FIG. 16  showing how the antenna may be mounted in one of the four corners of the device in accordance with an embodiment of the present invention. 
         FIG. 18  is a cross-sectional side view of an antenna and associated structures in an electronic device having a planar dielectric layer such as a layer of display cover glass in accordance with an embodiment of the present invention. 
         FIG. 19  is a top view of the antenna an associated structures of  FIG. 18  in accordance with an embodiment of the present invention. 
         FIG. 20  is a cross-sectional side view of illustrative structures that may be used in mounting and grounding an antenna of the type shown in  FIGS. 18 and 19  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in one or more wireless communications bands such as cellular telephone bands, satellite navigation bands, and local wireless area network bands (e.g., 2.4 GHz and 5 GHz to support IEEE 802.11 communications or 2.4 GHz to support Bluetooth® communications). Other wireless communications bands may also be supported. 
     The wireless communications circuitry may include one or more antennas. The antennas may be based on antenna structures such as patch antennas, monopole antenna structures, dipoles, loop antennas, closed slot antennas, open slot antennas, planar inverted-F antennas, inverted-F antennas, hybrid antennas that include more than one antennas of these types, and other antenna structures. 
     To ensure that the antennas operate satisfactorily while being hidden from view, antenna structures may be mounted behind dielectric structures such as planar dielectric layers. In devices with displays, the displays may include one or more planar dielectric layers such as a cover glass layer, a polarizer layer, a color filter array layer, a thin-film transistor layer, etc. A device may also include one or more planar dielectric layers that are not associated with a display. For example, a device may include one or more planar dielectric housing structures. 
     An illustrative electronic device such as a handheld electronic device in which one or more antennas may be mounted behind planar dielectric layer is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may be, for example, a handheld electronic device such as a cellular telephone, media player, or gaming device (as examples). 
     Device  10  may include a housing such as housing  12 . Housing  12  may be formed from plastic, metal, fiber composites such as carbon fiber, glass, ceramic, other materials, and combinations of these materials. Housing  12  may be formed using a unibody construction in which housing  12  is formed from an integrated piece of material or may be formed from frame structures, housing walls, and other components that are attached to each other using fasteners, adhesive, and other attachment mechanisms. In some situations, housing  12  may be formed from dielectrics such as plastic and glass. In other situations, housing  12  may be formed from conductive materials such as metal. Particularly in arrangements where housing  12  includes metal structures, care should be taken in locating antennas in device  10 , because the metal of housing  12  may affect antenna performance. 
     Device  10  may have input-output devices such as a track pad or other touch sensitive devices, a keyboard, microphones, speakers, and other input-output devices. These devices may be used to gather user input and to supply a user with output. Ports such as port  26  may receive mating connectors (e.g., an audio plug, a connector associated with a data cable, etc.). 
     Device  10  may have buttons such as buttons  13  and  24 . Buttons such as buttons  12  may be mounted in housing  12  (e.g., in a housing sidewall). Buttons such as button  24  may be mounted on the front face of device  10  (e.g., to serve as a menu button). 
     Device  10  may include a display such a display  14 . Display  14  may be a liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, an electronic ink display, or a display implemented using other display technologies. A touch sensor may be incorporated into display  14  (i.e., display  14  may be a touch screen display). Touch sensors for display  14  may be resistive touch sensors, capacitive touch sensors, acoustic touch sensors, light-based touch sensors, force sensors, or touch sensors implemented using other touch technologies. 
     Display  14  may contain multiple layers. For example, display  14  may contain a backlight unit, optical films such as polarizers and birefringent films, a touch sensor array, a thin-film transistor layer, and a color filter array layer. The outermost layer of display  14  may be formed from one of these display layers (e.g., a color filter array layer or a polarizer layer) or may be formed from a protective cover layer. A protective cover layer for display  14  may, for example, be formed from a transparent cover plate such as a clear plastic plate or a layer of glass (sometimes referred to as a cover glass, cover glass layer, or cover glass plate). 
     In the illustrative arrangement of  FIG. 1 , display  14  has an outermost layer (e.g., a cover glass layer) that extends over the front surface of device  10 . The central portion of display  14  may contain active images pixels for forming an image and may therefore sometimes be referred to as the active region of the display. The surrounding portions of display  14  do not contain image pixels and are therefore sometimes said to form an inactive region of the display. In the example of  FIG. 1 , rectangular dashed line  18  denotes the border between interior rectangular active region  16  and surrounding inactive region  20 . Region  20  has a substantially rectangular ring shape formed by left, right, top, and bottom edge regions. 
     Active region  16  of display  14  may contain conductive structures such as touch sensor electrodes, transistors and interconnect lines associated with a thin-film transistor array or other image pixel array, etc. Because conductors may affect the operation of the antennas in device  10 , it may be desirable to locate antennas in device  10  at locations other than those immediately under active region  16  such as under top edge portion  28  of inactive region  20  or lower edge portion  22  of inactive region  20 . Antennas may also be formed behind other portions of inactive display region  20  (e.g., to the left or right of active region  16 ). 
     When antennas are located under inactive display region  20 , antenna signals may be transmitted and received through region  20  (i.e., portions of inactive region  20  such as upper rectangular region  28  at the top end of device  10  or lower rectangular region  22  at the lower end of device  10 ) and need not be conveyed through conductive structures such as conductive sidewalls and conductive planar rear wall structures in housing  12 . If desired, device  10  may contain other planar dielectric structures. For example, the rear surface of device  10  (i.e., the surface opposing the front side that contains display  14 ) may be formed from a planar dielectric structure (e.g., a glass plate, a ceramic plate, etc.). Antennas may be formed under this type of rear plate or under other dielectric device structures. 
     As shown in  FIG. 2 , electronic device  10  may be a device such as a portable computer or other device that has a two-part housing formed from upper housing  12 A and lower housing  12 B. Upper housing  12 A may include display  14  and may sometimes be referred to as a display housing. Lower housing  12 B may sometimes be referred to as a base or main housing. Housings  12 A and  12 B may be connected to each other using a hinge (e.g., a hinge located along the upper edge of lower housing  12 B and the lower edge of upper housing  12 A). The hinge may allow upper housing  12 A to rotate about axis  38  in directions  36  relative to lower housing  12 B. Device  10  may include input-output components such as keyboard  30  and track pad  32 . 
     Display  14  may be surrounded by inactive regions  20 . Inactive regions  20  may be associated with portions of a cover glass layer or other dielectric layer that does not have underlying active image pixel elements. A cosmetic trim structure (e.g., a bezel formed from a dielectric such as plastic) may, if desired, be used to hide portions  20  from view. In configurations where it is desired to minimize the size of such trim structures, inactive portions  20  may be formed as integral portions of a cover plate on display  14  (e.g., a rectangular ring portion of display  14  that surrounds a central active display region and forms a peripheral border for display  14 ). Antennas may be formed under inactive display portions  20  or other planar dielectric structures in device  10  of  FIG. 2  (e.g., dielectric plates such as glass plates that are formed as part of housing  12 , etc.). 
     As shown in  FIG. 3 , electronic device  10  may be a computer that is integrated into a computer monitor housing, may be a computer monitor, or may be a television. In this type of configuration, display  14  may be mounted on a support structure such as stand  40 . Inactive border region  20  of display  14  may be covered with a trim structure such as a bezel formed from plastic or other dielectric material or may be an uncovered peripheral portion of a display structure such as a layer of cover glass. Antennas may be formed under regions  20  at the edges of display  14  or may be formed behind other planar dielectric structures in device  10  of  FIG. 3 . As an example, housing  12  may have a planar dielectric structure such as a dielectric plate on its rear surface. Antennas for device  10  may be formed under the surface of this type of dielectric plate if desired. 
     Illustrative circuitry that may be included in electronic device  10  (e.g., electronic devices of the types shown in  FIGS. 1 ,  2 , and  3  and other electronic equipment) is shown in  FIG. 4 . As shown in  FIG. 4 , device  10  may include control circuitry  42 . Control circuitry  42  may include storage such as flash memory, hard disk drive memory, solid state storage devices, other nonvolatile memory, random-access memory and other volatile memory, etc. Control circuitry  42  may also include processing circuitry. The processing circuitry of control circuitry  42  may include digital signal processors, microcontrollers, application specific integrated circuits, microprocessors, power management unit (PMU) circuits, and processing circuitry that is part of other types of integrated circuits. 
     Circuitry  42  may include input-output devices such as displays, speakers, microphones, status indicator light-emitting diodes, sensors such as proximity sensors and accelerometers, touch screens, data port circuits coupled to data ports, analog input-output circuits coupled to audio connectors and other analog signal ports, track pads and other pointing devices, etc. 
     Wireless communications circuitry such as radio-frequency transceiver circuitry  44  may be used in transmitting and receiving radio-frequency signals. Circuitry  44  may be used to handle one or more communications bands. Examples of communications bands that may be handled by circuitry  44  include cellular telephone bands, satellite navigation bands (e.g., the Global Positioning System band at 1575 MHz), bands for short range links such as the Bluetooth® band at 2.4 GHz and wireless local area network (WLAN) bands such as the IEEE 802.11 band at 2.4 GHz and the IEEE 802.11 band at 5 GHz, etc. 
     Paths such as path  48  may include one or more radio-frequency transmission lines. Transmission lines in path  48  may include coaxial cable paths, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, transmission lines formed from combinations of transmission lines of these types, etc. 
     Transmission line path  48  may be used to couple radio-frequency transceiver circuitry  44  to one or more antennas  46 . Antenna structures in antennas  46  may receive incoming radio-frequency signals that are routed to radio-frequency transceiver circuitry  44  by path  48 . During signal transmission operations, radio-frequency transceiver circuitry  44  may transmit radio-frequency signals that are conveyed by path  48  to antenna structures  46  and transmitted to remote receivers. 
     Device housings such as housings  12  of  FIGS. 1 ,  2 , and  3 , often contain conductive structures such as portions of display  14  and portions of housing  12 . Some of these structures (e.g., parts of metal housing walls in housing  12  or other structural device members) may sometimes be used in forming antennas for device  10  and may therefore be considered to form part of antennas  46  of  FIG. 4 . For example, parts of a metal housing (e.g., parts of housings  12  of  FIGS. 1 ,  2 , and  3 ) may form some or all of an antenna ground element for antenna(s)  46 . 
     Antennas  46  may also contain antenna resonating element structures that work with the antenna ground elements. Antenna resonating element structures for antennas  46  may be formed from patterned metal foil, wires, parts of conductive housing structures or other conductive structures. With one suitable arrangement, antenna resonating element structures for antennas  46  are formed from conductive traces on substrates such as rigid printed circuit boards and flex circuits (i.e., printed circuits formed from patterned traces on thin sheets of flexible polymers such as polyimide). 
     In devices that contain conductive structures such as conductive housing structures, conductive display structures, and other conductive components that may interfere with radio-frequency signals, it may be desirable to mount some or all of the structures that make up antennas  46  under an inactive display region or other such dielectric structure. For example, it may be desirable to locate an antenna resonating element that is formed from patterned traces on a substrate on the inner surface of a display cover glass member or a dielectric housing plate. 
     As shown in the cross-sectional diagram of  FIG. 5 , device  10  may have antenna structures  46  that are mounted adjacent to inner surface  50  of dielectric structure  52 . Dielectric structure  52  may be a planar member having an upper (exterior) surface (surface  60 ) that is parallel to inner surface  50 . The thickness of structure  52  (i.e., the vertical distance between inner surface  50  and outer surface  60 ) may be less than 5 mm, less than 3 mm, less than 1 mm, less than 0.5 mm, or less than 0.3 mm (as examples). Structure  52  may be formed from glass, ceramic, fiber composites, plastic, other materials, or combinations of these materials. 
     With one suitable arrangement, structure  52  may form a planar structure such as a rectangular dielectric plate. The plate may serve as a cover for a display, as a housing structure, etc. As shown in  FIG. 5 , for example, structure  52  may serve to cover the front face of device  10 , whereas housing portion  12 R may form a substantially planar rear housing structure. Housing sidewalls  12 S and housing structure  12 R may be integral portions of housing  12 . Antenna structures  46  and internal device components  54  may be mounted within housing  12 . In configurations in which sidewalls  12 S and structure  12 R form part of an integral housing, sidewalls  12 S may be curved. Housing sidewalls  12 S and structure  12 R may also be formed from separate structures. For example, housing structure  12 R may be a rectangular planar member and housing sidewalls  12 S may be formed from a metal peripheral housing band that surrounds rectangular structure  52 . 
     Internal components  54  may include printed circuit boards, a battery, sensors, integrated circuits, display structures, touch sensor structures (e.g., for a touch screen display), discrete components (e.g., inductors, resistors, and capacitors), connectors for input-output ports, and other device circuitry. 
     Antenna structures  46  may include mounting and biasing structures, antenna resonating element structures such as conductive antenna traces on substrates such as printed circuit boards, adhesive, etc. Radio-frequency transceiver  44  may be mounted on a support such as printed circuit board  66 . A connector such as connector  68  may be used to couple transmission line  48  to board  66 . Transmission line  48  may be coupled to antenna feed  58 . 
     Antenna feed  58  may have a positive antenna feed terminal such as antenna feed terminal  64  and a ground antenna feed terminal such as ground antenna feed terminal  62 . Parts of housing  12  such as parts of rear housing structure  12 R and/or portions of housing sidewalls  12 S may form a ground element for antenna structures  46  (i.e., portions of housing  12  may be considered to form portions of antenna structures  46 ). Antenna ground terminal  62  may be electrically connected to the antenna ground element for antenna structures  46  (e.g., by connecting feed terminal  62  to housing  12  using conductive structures such as wires, metal screws or other fasteners, conductive support brackets, metal traces on printed circuit boards, metal traces on plastic supports and other substrates, conductive housing structures, etc.). Positive antenna feed terminal  64  may be connected to an antenna resonating element that, in combination with the antenna ground element, forms an antenna for device  10 . 
     Antenna structures  46  may contain one or more antennas that are fed using this type of configuration. For example, antenna structures  46  may contain one or more antenna resonating elements each of which is configured to operate in a different respective communications band. Antenna structures  46  may also contain one or more multiband antennas (i.e., one or more antennas that are each configured to operate at more than one different communications band). 
     The antenna or antennas formed by structures  46  may be monopoles, dipoles, planar inverted-F antennas, patch antennas, inverted-F antennas, loop antennas, closed or open slot antennas, other antenna designs, or antennas that use hybrid arrangements incorporating one or more of these antennas. An illustrative inverted-F antenna of the type that may be used for structures  46  is shown in  FIG. 6 . As shown in  FIG. 6 , inverted-F antenna  46  may include a ground plane element  46 G and an antenna resonating element (element  46 R). Antenna resonating element  46 R may have a main resonating element branch B, a short circuit branch SC, and a feed branch F. Antenna feed terminals  64  and  62  may be coupled in feed branch F. Antenna resonating element  46 R may be formed from conductive structures such as patterned metal traces. The patterned metal traces may be formed on a substrate such as a single-layer or multilayer printed circuit board substrate, a plastic support structure, a ceramic substrate, a glass substrate, or other structures. Examples of printed circuits that may be used in forming antenna resonating element  46 R include rigid printed circuit boards such as fiberglass filled epoxy boards (e.g., FR4), flex circuits (i.e., printed circuits formed from one or more laminated polymer layers such as sheets of polyimide that are connected using interposed layers of adhesive), and rigid flex (e.g., boards that include both rigid and flexible regions). 
     As shown in the cross-sectional side view of  FIG. 7 , antenna structures  46  may be mounted against inner surface  50  of dielectric structures  52 . In this configuration, radio-frequency antenna signals  68  may be transmitted and received through structures  52 . As shown in  FIG. 8 , there is a potential for structures  46  that are loosely secured to separate from surface  50 . For example, some or all of structures  46  may separate sufficiently from surface  50  to give rise to air gaps such as air gaps  70 . 
     The presence of air gaps such as air gaps  70  may cause unpredictable changes in the impedance of antenna structures  46  that can undesirably influence the performance for antenna structures  46 . Antenna structures  46  that are mounted directly against surface  50  of structures  52  in  FIG. 7  may, for example, have an antenna resonance curve such as curve  72  of  FIG. 9  that peaks at a frequency f r . Frequency f r  may coincide with the center frequency of a communications band of interest such as the center of a 2.4 GHz or 5 GHz IEEE 802.11 band (i.e., antenna structures  46  may function properly when mounted as shown in  FIG. 7 ). If, however, gaps such as air gaps  70  of  FIG. 8  develop between antenna structures  46  and surface  50  of structures  52 , antenna structures  46  may be characterized by antenna resonance curve  74  of  FIG. 9 . As shown in  FIG. 9 , the frequency peak of curve  74  may be shifted significantly (e.g., by 50 MHz) from the peak of curve  72 , because gaps  70  detune antenna structures  46 . When mounted so that gaps such as gaps  70  can unexpectedly form between structures  46  and surface  50 , antenna performance may be unpredictable. 
     To ensure that antenna performance in device  10  is predictable and does not change unexpectedly over time, antenna structures  46  may be mounted against surface  50  of structures  52  as shown in  FIG. 7 . Arrangements of the type shown in  FIG. 10  may be used to ensure satisfactory mounting. 
     As shown in  FIG. 10 , antenna structures  46  (e.g., an antenna resonating element) may be mounted against surface  50  of structures  52  using adhesive  76 . Adhesive  76  may be a pressure sensitive adhesive, a liquid adhesive such as epoxy, adhesive-coated tape, or other adhesives. Adhesive  76  may be cured by application of light (e.g., ultraviolet light), by raising the temperature of adhesive  76  (e.g., to over 100° to thermally cure adhesive  76 ), by using a two-part formulation for adhesive  76 , etc. 
     Biasing and support structures  78  may include support members such as dielectric supports formed from rigid plastic, flexible plastic (e.g., soft plastic such as polytetrafluoroethylene), glass, ceramic, etc. Support members may be used, for example, to form a spacer that separates antenna resonating element  46  from housing  12  (which may form a ground element for the antenna). Biasing structures in structures  78  may include layers of foam, rubber, or other compressible substances, coil springs, leaf springs, other spring structures, etc. Biasing structures in structures  78  may be compressed between antenna resonating element  46  (e.g., the flex circuit or other substrate from which antenna resonating element  46  is formed) and housing  12  (or structures mounted on housing  12 ). When compressed in this way, the biasing structures can create a restoring force that presses downwards in direction  82  against housing  12  (or other underlying structures in device  10 ) and that presses upwards in direction  82 . The upwards (outwards) pressure in direction  80  that is produced by support structures  78  helps press antenna resonating element  46  against adhesive  76 , thereby helping to attach antenna resonating element  46  securely against lower (interior) surface  50 . 
     Over time, the upwards force produced by the biasing structures in structures  78  may lessen (e.g., because the restoring force generated by the compressed foam or other biasing structure tends to weaken under continuous load). This effect will help lessen the likelihood that structures  52  will be undesirably forced out of device  10 . Because adhesive  76  will preferably have formed a permanent adhesive bond by the time that the biasing force from structures  78  has faded, there will generally not be a risk of detachment between antenna resonating element  46  and surface  50 . 
     In some assembly scenarios it may be possible to attach antenna resonating element  46  to surface  50  using adhesive  76  before structures  52  are mounted within housing  12 . In some device architectures, however, it may be difficult or impossible to attach antenna resonating element  46  to surface  50  before structures  52  are mounted within housing  12 . It may, for example, be desirable to form transmission line  48  ( FIG. 5 ) from an integral portion of the same flex circuit (or other substrate) that is being used to form antenna resonating element  46 . This type of arrangement may help minimize part count and may avoid interposing potentially unreliable radio-frequency interfaces between connector  68  on board  66  and antenna resonating element  46 . If, however, transmission line  48  and antenna resonating element  46  are formed from a single piece of flex circuit material, antenna resonating element  46  may become tethered to connector  68  during assembly. The finite length of the transmission line portion of the flex circuit may not be sufficient to accommodate the amount of relative movement between structures  52  and housing  12  that would allow antenna resonating element  46  to be attached to surface  50  of structures  52  before structures  52  are inserted into housing  12 . 
       FIG. 11  is a cross-sectional side view of an illustrative mounting arrangement of the type that may be used to mount antenna resonating element  46  within device  10 . Antenna resonating element  46  may be formed from a single layer substrate or a substrate that contains multiple layers such as a multilayer printed circuit board substrate (e.g., a flex circuit or rigid board). The presence of multiple layers in antenna resonating element  46  of  FIG. 11  is indicated by dashed lines  86 . One or more layers of patterned conductive traces such as traces  92  may be formed in the layers of the flex circuit. Conductive traces  92  may be formed from a metal such as copper (as an example). 
     Support structures  78  may contain one or more support structures such as structure  90  and one or more biasing structures such as compressible layer  88 . Compressible layer  88  may be formed from a compressible material such as foam (as an example). Structure  90  may be formed from plastic or other suitable dielectric materials. As an example, structure  90  may be formed from a material such as polytetrafluoroethylene. Optional adhesive may be used to attach structure  90  to housing  12 . Housing  12  may be formed from a conductive material such as metal (e.g., stainless steel, aluminum, etc.) and may form an antenna ground element that, in conjunction with antenna resonating element  46 , forms an antenna for device  10 . 
     Dielectric structures  52  may be formed from a glass plate or other planar dielectric member. For example, dielectric structure  52  may be a clear layer of cover glass that forms the outermost layer of display  14 . In this type of arrangement, some of the cover glass layer will cover active display region  16  and will allow an image from underlying image pixels to be viewed and some of the cover glass layer (i.e., the portion that overlaps antenna resonating element  46 ) may be associated with inactive display region  20  (see, e.g.,  FIGS. 1 ,  2 , and  3 ). 
     To hide antenna resonating element  46  from view in direction  94 , a coating layer of opaque material such as coating  84  may be formed on interior surface  50  of structure  52 . Coating  84 , which may sometimes be referred to as an opaque masking layer, may be formed from a layer of black ink, a layer of ink having other suitable colors (e.g., white, blue, green, red, etc.), paint, polymer, or other suitable materials. If desired, the light-blocking functions of opaque masking layer  84  may be provided by incorporating opaque material into adhesive coating  76  (i.e., so that masking layer  84  may be omitted in favor of using only coating  76 ). 
     In a typical configuration, structure  52  may have a thickness of less than 1 mm (e.g., 0.8 mm) and may have a dielectric constant (∈ r ) of 8-13. Opaque masking layer may have a thickness of less than 0.2 microns (as an example). Adhesive layer  76  may have a thickness of less than 60 μm (e.g., 40-50 μm) and a dielectric constant of 4-5. Antenna resonating element  46  may be formed from a substrate such as a polyimide flex circuit substrate having a thickness of less than 0.2 mm (e.g., about 0.1 mm) and a dielectric constant of about 3.5-4. Foam layer  88  may have a thickness of less than 2 mm (e.g., about 1.5 mm) and may have a dielectric constant of about 1.5 to 1.6. Support structure (sometimes referred to as a plastic carrier) may have a thickness of less than 5 mm (e.g., 3-4 mm) and may have a dielectric constant of about 2.2. 
       FIG. 12  shows how the order of biasing structure (e.g., the layer of foam or other compressible material) and support structure  90  may be reversed. In the  FIG. 12  arrangement, antenna resonating element  46  may rest on support structure  90  and support structure  90  may rest on biasing structure  88 . Optional layers of adhesive may be used to secure biasing member  88  to support member  90 , to secure support member  90  to antenna resonating element  46 , and to secure biasing member  88  to housing  12 . 
     In the illustrative configuration of  FIG. 13 , biasing structures  78  contain little or no support structures and contain exclusively (or nearly exclusively) biasing structures  88 . Biasing structures  88  may be formed from a layer of compressible material such as foam, an elastomeric material, etc. In this type of configuration, biasing structures  88  may serve to provide both supporting and biasing functions. When only foam is included between antenna resonating element  46  and housing structures  12  it may be desirable to limit the vertical spacing between antenna resonating element  46  and housing  12  to limit the propensity of this type of stacked arrangement to tip to the side. In arrangements of the type shown in  FIGS. 11 and 12 , support structures  90  are typically stiffer (more rigid) that compressible biasing member  88 , which reduces the likelihood of tipping. 
     If desired, one or more antennas in electronic device  10  may be implemented as cavity antennas. As shown in  FIG. 14 , for example, antenna resonating element  46  may be mounted in a cavity such as cavity  98 . Cavity  98  may have sidewalls  98 S and a rear cavity surface such as planar cavity surface  98 L. As shown in  FIG. 15 , cavity  98  may have a rectangular shape. Other shapes may be used for cavity  98  if desired (e.g., circular, oval, shapes with curved and straight sidewalls when viewed from the top, shapes with depths (vertical dimensions) of varying magnitude, etc. Metal or other conductive materials may be used in forming the walls of cavity  98 . 
     As shown in  FIG. 14 , cavity  98  may be biased in direction  80  towards structure  52  using biasing structures  78 . Biasing structures  78  may be based on one or more layers of compressible material such as foam or elastomeric polymers, springs, or other biasing members. If desired, support structures (e.g., plastic, metal, etc.) may be included in structures  78 . Integral portions of housing  12  may be used as supports, because close proximity between conductive portions of housing  12  and antenna resonating element  46  will not affect antenna performance in the  FIG. 14  configuration, as cavity  98  surrounds and encloses antenna resonating element  46 . To ensure that the spacing between lower cavity wall  98 L and antenna resonating element  46  is well controlled so that antenna performance is within design specifications, the upper edges of walls  98 S and antenna resonating element  46  may both be biased upwards in direction  80  against adhesive layer  76 , optional opaque masking layer  84 , and surface  50 . 
       FIG. 16  is a cross-sectional side view of an illustrative configuration that may be used in mounting antenna resonating element  46  within device  10 . As shown in  FIG. 16 , biasing and support structures  78  may be used to mount antenna resonating element  46  against the inner surface  50  of cover glass  52 . Antenna resonating element  46  may be located under part of inactive display region  20  in display  14 . Display module  100  (e.g., a liquid crystal display module with an optional integrated touch sensor array) may be formed under active region  16  of display  14 . Radio-frequency transceiver  44  may be mounted to printed circuit board  66 . Housing  12  may be formed from a conductive material such as metal and may form an antenna ground element. Antenna resonating element  46  and the ground antenna element formed from housing  12  may form an antenna for device  10 . Transmission line  48  may be used to convey radio-frequency signals between radio-frequency transceiver  44  and the antenna. The transmission line may have a positive conductor that is electrically connected to a positive antenna feed terminal and a ground conductor that is electrically connected to a ground antenna feed terminal. 
       FIG. 17  is a top view of electronic device  10  of  FIG. 16  showing how the antenna formed from antenna resonating element  46  of  FIG. 16  may be located in a region such as region  102 . Region  102  may be located in a corner of device housing  12  (e.g., the upper left corner in the orientation of  FIG. 17 ). This region may lie within upper end region  28  of device  10 . Antennas may also be mounted under other portions of structure  52  (e.g., in other inactive display regions). If desired, structure  52  may form a rear plate for device  10  (e.g., a rear dielectric plate such as a rear glass plate, rear ceramic plate, etc.). In this type of configuration, antenna resonating element  46  may be mounted under portions of structure  52  such as portions at one of the ends of device  10  or in the center of the rear of device  10  (as examples). 
       FIG. 18  is a more detailed cross-sectional view of device  10  of  FIG. 16  showing how support structure  90  may be mounted on housing  12 . Antenna resonating element  46  and transmission line  48  may be formed as integral parts of a common flex circuit. Biasing layer  88  may be interposed between support structure  90  and antenna resonating element  46 . Adhesive  76  may be used to attach antenna resonating element  46  to structure  52  (which may be coated with an optional layer of opaque masking material such as layer  84 ). A support structure such as metal bracket  106  or other conductive structure may be electrically (and, if desired, mechanically) connected to housing  12 . A conductive screw such as metal screw  104  may be used to short conductive ground traces on the flex circuit that contains element  46  and transmission line  48  to bracket  106 . This grounds the flex circuit ground traces to housing  12 , which forms an antenna ground element. Transmission line  48  may extend continuously from antenna resonating element  46  to connector  68  on board  66  and thereby to transceiver  44 , as indicated by dashed line  48  in  FIG. 16 . 
     A flex circuit of the type that may be used to form antenna resonating element  46  and transmission line  48  (i.e., flex circuit  110 ) is shown in the top view of  FIG. 19 . As shown in  FIG. 19 , flex circuit  110  may have dielectric layers such as polyimide layers  108 . Conductive traces such as traces  92  may be formed in one or more layers of flex circuit  110 . In antenna resonating element portion  46  of flex circuit  110 , traces  92  form main branch B of an inverted-F antenna such as the antenna of  FIG. 6 . Feed path F and short circuit path SC are also formed from portions of traces  92 , as shown in  FIG. 19 . In transmission line region  48 , one part of traces  92  (upper trace  92 L) runs on top of another part of traces  92  (lower trace  92 U). A layer of polyimide flex circuit material separates traces  92 L and  92 U to form a microstrip transmission line. Trace  92 L may serve as the ground conductor and trace  92 U may serve as the positive conductor in microstrip transmission line  48 . If desired, one or more upper layers of polyimide in flex circuit  110  may cover traces  92  in antenna resonating element  46  and transmission line  48 . In the vicinity of screw  104 , a ring-shaped portion of traces  92  is exposed and forms an electrical connection with the lower surface of the head of screw  104 . Screw  104  screws into grounded bracket  106  ( FIG. 18 ), thereby grounding traces  92  at screw  104  to antenna ground. 
       FIG. 20  shows how screw  104  may be shorted to an exposed portion of traces  92  on flex circuit  110 . Bracket  106  may have a threaded bore that receives mating threads on the shaft of screw  104 , thereby shorting bracket  106  and screw  104  together. Some of carrier  90  may be interposed between flex circuit  110  and bracket  106  to support flex circuit  110  and bracket  106  within the interior of housing  12  and device  10 . 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20100827
Publication Date: 20140701
Grant Date: 20140701
Priority Date: 20100827
Inventors: LI QINGXIANG
SCHLUB ROBERT W.
ROTHKOPF FLETCHER R.
MITTLEMAN ADAM D.
JIANG YI
MCMILIN EMILY
ZHANG LIJUN
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 44651139