PATENT DOCUMENT

Publication Number: US-8896487-B2
Application Number: US-50057009-A
Country: US
Kind Code: B2

Title: Cavity antennas for electronic devices

Abstract:
Antennas are provided for electronic devices such as portable computers. An electronic device may have a housing in which an antenna is mounted. The housing may have an antenna window for the antenna. The antenna window may be formed from dielectric or from antenna window slots in a conductive member such as a conductive wall of the electronic device housing. An antenna may have an antenna resonating element that is backed by a conductive antenna cavity. The antenna resonating element may have antenna resonating element slots or may be formed using other antenna configurations such as inverted-F configurations. The antenna cavity may have conductive vertical sidewalls and a conductive rear wall. The antenna cavity walls may be formed from conductive layers on a dielectric antenna support structure.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing having a curved housing surface; and 
 a cavity-backed antenna mounted in the housing that includes an antenna cavity formed from a dielectric support structure covered with a layer of conductive material and an antenna resonating element, wherein the layer of conductive material comprises a curved conductive wall formed opposite to the antenna resonating element, wherein the curved conductive wall extends parallel to the curved housing surface, wherein the dielectric support structure forms a separate structure from the housing and wherein the antenna resonating element comprises a multi-branch inverted-F antenna resonating element formed from conductive antenna traces on a printed circuit board, and wherein the housing is an integral piece that encloses the dielectric support structure. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the dielectric support structure comprises a plastic support structure and wherein the layer of conductive material comprises metal. 
     
     
       3. The electronic device defined in  claim 2  wherein the conductive antenna traces form an inverted-F antenna resonating element arm having at least two branches. 
     
     
       4. The electronic device defined in  claim 2  further comprising:
 radio-frequency transceiver circuitry; and 
 a transmission line that couples the radio-frequency transceiver circuitry to the cavity-backed antenna. 
 
     
     
       5. The electronic device defined in  claim 4  wherein the cavity-backed antenna comprises a positive antenna feed terminal connected to the conductive antenna traces and comprises a ground antenna feed terminal connected to the layer of conductive material. 
     
     
       6. The electronic device defined in  claim 2  wherein the printed circuit board comprises a flex circuit and wherein the conductive antenna traces and the layer of conductive material comprise copper. 
     
     
       7. The electronic device defined in  claim 1  wherein the housing comprises a conductive housing wall having antenna window slots that form a slot-based antenna window for the cavity antenna. 
     
     
       8. The electronic device defined in  claim 7  wherein the conductive housing wall comprises a curved portion of a portable computer lid. 
     
     
       9. The electronic device defined in  claim 7  wherein the antenna window slots are less than 100 microns in width and are more than 5 mm in length. 
     
     
       10. The electronic device defined in  claim 7  wherein the antenna window slots are filled with a solid dielectric. 
     
     
       11. An antenna in an electronic device housing having a curved housing surface, the antenna comprising:
 a dielectric support structure; 
 a metal layer on the dielectric support structure that forms a conductive antenna cavity, wherein the conductive antenna cavity has a curved conductive wall formed from part of the metal layer; and 
 an antenna resonating element having a printed circuit board with an inverted-F antenna resonating element trace, wherein the curved conductive wall is formed opposite to the antenna resonating element, and wherein the curved conductive wall extends parallel to the curved housing surface. 
 
     
     
       12. The antenna defined in  claim 11  further comprising a slot-based antenna window that is located adjacent to the conductive antenna cavity and the antenna resonating element. 
     
     
       13. The antenna defined in  claim 12  wherein the slot-based antenna window comprises a metal housing structure having a plurality of antenna window slots each having a width of less than 100 microns and each having a length of at least five millimeters. 
     
     
       14. The antenna defined in  claim 13  wherein the inverted-F antenna resonating element trace has multiple branches and resonates in at least two communications bands. 
     
     
       15. A portable computer, comprising:
 an upper housing portion having a continuous metal housing structure; 
 an antenna window formed from a plurality of antenna window slots in the metal housing structure 
 a lower housing portion that is pivotably attached to the upper housing portion; 
 radio-frequency transceiver circuitry; 
 a transmission line that is coupled to the radio-frequency transceiver circuitry; and 
 a cavity-backed antenna that is located under the antenna window, that is coupled to the transmission line, and that has an antenna cavity formed from a plastic support with vertical metal sidewalls and a rear metal layer, wherein the plastic support forms a separate structure from the upper and lower housing portions, and wherein the upper housing portion has a curved surface, the rear metal layer of the antenna cavity comprises a curved metal layer, and the curved metal layer extends parallel to the curved surface of the upper housing portion. 
 
     
     
       16. The portable computer defined in  claim 15  wherein the upper housing portion has a curved edge region in which the antenna window slots are formed. 
     
     
       17. The electronic device defined in  claim 1 , wherein the dielectric support structure is solid. 
     
     
       18. The electronic device defined in  claim 1 , wherein the curved conductive wall is formed adjacent to the curved housing surface. 
     
     
       19. The electronic device defined in  claim 18 , wherein the curved conductive wall lies flush with the curved housing surface. 
     
     
       20. The antenna defined in  claim 11 , wherein the curved conductive wall lies flush with the curved housing surface. 
     
     
       21. The portable computer defined in  claim 15 , wherein the rear metal layer is formed adjacent to the curved surface of the upper housing portion.

Description:
BACKGROUND 
     This relates generally to antennas, and, more particularly, to antennas for electronic devices. 
     Electronic devices such as portable computers and handheld electronic devices are becoming increasingly popular. Devices such as these are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry to communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz (e.g., the main Global System for Mobile Communications or GSM cellular telephone bands). Long-range wireless communications circuitry may also be used handle the 2100 MHz band and other bands. Electronic devices may use short-range wireless communications links to handle communications with nearby equipment. For example, electronic devices may communicate using the WiFi® (IEEE 802.11) bands at 2.4 GHz and 5 GHz (sometimes referred to as local area network bands) and the Bluetooth® band at 2.4 GHz. 
     It can be difficult to incorporate antennas successfully into an electronic device. Some electronic devices are manufactured with small form factors, so space for antennas is limited. In many electronic devices, the presence of electronic components in the vicinity of an antenna serves as a possible source of electromagnetic interference. Antenna operation can also be blocked by conductive structures. This can make it difficult to implement an antenna in an electronic device that contains conductive housing walls or other conductive structures that can potentially block radio-frequency signals. 
     It would therefore be desirable to be able to provide improved antennas for wireless electronic devices. 
     SUMMARY 
     Antennas may be provided for electronic devices. The electronic devices may be portable devices such as portable computers or cellular telephones. 
     An electronic device may be provided with a housing. The housing may contain conductive portions such as conductive walls. An antenna for the electronic device may be mounted in the housing. The antenna may be provided with an antenna cavity. The antenna cavity may be formed from a layer of conductive material on a plastic support structure. The antenna cavity may have vertical sidewalls and a planar rear wall. The conductive material may be a metal such as copper. 
     The antenna may have an antenna resonating element. The antenna resonating element may be configured to cover multiple communications bands of interest. For example, the antenna resonating element may be configured to cover communications bands at 2.4 GHz and 5 GHz. 
     The antenna resonating element may be located in the antenna cavity. The resonating element may be formed from a layer of conductive material such as metal on a substrate. The substrate may be a printed circuit board such as a flexible or rigid printed circuit board. The layer of conductive material on the printed circuit board may be configured to form one or more antenna resonating element antenna slots. The antenna resonating element slots may include open and closed slots. The layer of conductive material on the printed circuit board may also be configured to form an inverted-F antenna resonating element. With this type of configuration, a conductive trace on the printed circuit board may be patterned to form a main resonating element arm and multiple antenna resonating element branches. 
     The antenna may be provided with an antenna window. The antenna window may be formed from dielectric in an opening in the housing of the electronic device. The antenna window may also be formed from a plurality of slots in the conductive walls of the housing. Slot-based antenna windows such as these may be formed on a curved portion of a portable computer lid or other suitable housing structures. 
     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. 1A  is a front perspective view of an illustrative electronic device with an antenna in accordance with an embodiment of the present invention. 
         FIG. 1B  is a rear perspective view of an illustrative electronic device of the type shown in  FIG. 1A  with an antenna in accordance with an embodiment of the present invention. 
         FIG. 2A  is a front perspective view of another illustrative electronic device with an antenna in accordance with an embodiment of the present invention. 
         FIG. 2B  is a rear perspective view of an electronic device of the type shown in  FIG. 2A  in accordance with an embodiment of the present invention. 
         FIG. 3  is a schematic diagram of an illustrative electronic device with antenna structures in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of an illustrative electronic device with an antenna in accordance with an embodiment of the present invention. 
         FIG. 5  is a perspective view of an illustrative antenna cavity in accordance with an embodiment of the present invention. 
         FIG. 6  is a schematic diagram of an illustrative antenna based on an inverted-F antenna resonating element in accordance with an embodiment of the present invention. 
         FIG. 7  is a schematic diagram of an illustrative antenna based on an inverted-F antenna resonating element with multiple branches in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram of an illustrative antenna based on a slot antenna resonating element in accordance with an embodiment of the present invention. 
         FIG. 9  is a diagram of an illustrative antenna based on a slot antenna resonating element having multiple slots in accordance with an embodiment of the present invention. 
         FIG. 10  is a perspective view of an illustrative slot-based antenna window in accordance with an embodiment of the present invention. 
         FIG. 11  is a perspective view of an illustrative antenna cavity formed from a plastic support on which conductive cavity walls have been formed in accordance with an embodiment of the present invention. 
         FIG. 12  is cross-sectional side view of an illustrative antenna formed from an antenna cavity having a plastic support with conductive cavity walls in accordance with an embodiment of the present invention. 
         FIG. 13  is a top view of an illustrative antenna resonating element that may be used in a cavity antenna in accordance with an embodiment of the present invention. 
         FIG. 14  is a graph of an illustrative antenna frequency response that may be exhibited by a cavity antenna with an antenna resonating element of the type shown in  FIG. 13  in accordance with an embodiment of the present invention. 
         FIG. 15  is an exploded perspective view of a cavity antenna fed by an inverted-F resonating element in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 16  is a perspective view of a slot-based cavity antenna for an electronic device in accordance with an embodiment of the present invention. 
         FIG. 17  is a cross-sectional side view of a cavity antenna and an associated slot-based antenna window that allows radio-frequency antenna signals to pass through a curved portion of an electronic device housing in accordance with an embodiment of the present invention. 
         FIG. 18  is a cross-sectional side view of a cavity antenna and an associated slot-based antenna window that allows radio-frequency antenna signals to pass through a planar surface of an electronic device housing in accordance with an embodiment of the present invention. 
         FIG. 19  is a cross-sectional side view of a cavity antenna that transmits and receives radio-frequency antenna signals through a planar dielectric portion of an electronic device 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. Antenna structures in an electronic device may be used in transmitting and receiving radio-frequency signals. For example, single band and multiband antennas may be formed. Each antenna may have an antenna resonating element. The antenna resonating elements may be based on inverted-F designs, slot configurations, or other antenna resonating element arrangements. Antennas may be provided with antenna cavities. The antenna cavities may help to isolate the antennas from nearby electronic components in an electronic device and may help to improve antenna efficiency. Antennas may be mounted behind antenna windows. The antenna windows may be formed from slots in conductive structures. 
     Any suitable electronic devices may be provided with antennas. As an example, antennas may be formed in electronic devices such as desktop computers, portable computers such as laptop computers and tablet computers, handheld electronic devices such as cellular telephones, etc. With one suitable configuration, which is sometimes described herein as an example, antennas are formed in relatively compact electronic devices in which interior space can be valuable. These compact devices may be portable electronic devices. 
     Portable electronic devices that may be provided with antennas include laptop computers and small portable computers such as ultraportable computers, netbook computers, and tablet computers. Portable electronic devices may also be somewhat smaller devices. Examples of smaller portable electronic devices that may be provided with antennas include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, the portable electronic devices may be handheld electronic devices such as cellular telephones. 
     Space is at a premium in portable electronic devices and housings for these devices are sometimes constructed from conductive materials that block antenna signals. Arrangements in which antenna structures are formed behind an antenna window can help address these challenges. It may be desirable to form the antenna window in the conductive housing of the portable electronic device. Antenna windows may be formed in conductive housing walls by forming a dielectric antenna window structure in the conductive housing wall. If desired, slot-based antenna windows may be formed in conductive housing walls. In a slot-based antenna window, the window region is defined by a pattern of window slots. 
     An antenna resonating element and, if desired, an antenna cavity, may be formed under the antenna window. During operation, radio-frequency signals for the antenna can pass through the antenna window. The antenna cavity may help to isolate the antenna from surrounding electronic components. 
     Antennas with configurations such as these can be mounted on any suitable exposed portion of a portable electronic device. For example, antennas can be provided on the front or top surface of the device. In a handheld device or other device in which the rear of the device may be exposed during operation, it may be acceptable to form an antenna window on the rear device surface. Other configurations are also possible (e.g., with antennas mounted in more confined locations, on device sidewalls, etc.). The use of antenna mounting locations such as a top or rear surface is sometimes described herein as an example, but, in general, any suitable antenna mounting location may be used in an electronic device if desired. 
     Handheld devices that may be provided with antennas include cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, and handheld gaming devices. Handheld devices and other portable devices may include the functionality of multiple conventional devices. As an example, a handheld device with cellular telephone functions may include computing equipment resources that allow the handheld device to run games, media player applications, web browsers, productivity software, and other code. 
     An illustrative portable device such as a portable computer that may include an antenna is shown in  FIG. 1 . As shown in  FIG. 1 , device  10  may be a portable computer having a housing such as housing  12 . Housing  12  may have an upper portion such as upper housing  12 A, which is sometimes referred to as the lid or cover. Housing  12  may also have a lower portion such as lower housing  12 B, which is sometimes referred to as the housing base or main unit. Housing portions  12 A and  12 B may be pivotably attached to each other using a hinge structure such as hinge  52  (sometimes referred to as a clutch barrel hinge). A display such as display  14  may be mounted to the inner surface of upper housing  12 A. Other components such as keyboard  50  and touch pad  54  may be mounted in lower housing  12 B. 
     Housing  12 , which is sometimes referred to as a case, may be formed of any suitable materials including plastic, wood, glass, ceramics, metal, or other suitable materials, or a combination of these materials. In some situations, portions of housing  12  may be formed from a dielectric or other low-conductivity material, so as not to disturb the operation of conductive antenna elements that are located in proximity to housing  12 . In other situations, housing  12  may be formed from metal elements. An advantage of forming housing  12  from metal or other structurally sound conductive materials is that this may improve device aesthetics and may help improve durability and portability. 
     Particularly in configurations for device  10  in which some or all of housing  12  is formed from conductive materials, it may be advantageous to form an antenna for device  10  that has an antenna window. With this type of configuration, one or more of the antennas for device  10  may be hidden from view behind a dielectric member that serves as the antenna window. Antenna windows may also be formed from a pattern of slots in a conductive housing wall. When the slots are concealed sufficiently (e.g., by forming narrow slots or by covering the slots with an opaque dielectric to hide the slots from view), the antenna window will be hidden from view, thereby enhancing the aesthetics of the electronic device. 
     Suitable locations for an antenna in device  10  of  FIG. 1  include region  58  and region  56 . Region  58  is located on the edge of display  14 . Region  56  is located on the right front side of lower housing portion  12 B. As shown in  FIG. 1B , antennas can also be located on regions such as region  60  and region  62 . Region  60  is located in the middle of the top surface of the lid of device  10 . Region  62  is located in the corner of the lid. Other antenna locations may be used if desired (e.g., on the rear of device  10 , on the front of device  10 , on an exterior surface (e.g., the top of a lid), on an interior surface such as a surface adjacent to keys  50 , etc. 
     Another illustrative electronic device is shown in  FIGS. 2A and 2B . In the example of  FIGS. 2A and 2B , device  10  is a handheld electronic device such as a handheld device with cellular telephone capabilities. As shown in  FIG. 2A , device  10  may have housing  12 . Housing  12  may be formed from plastic, metal, other suitable dielectric materials, other suitable conductive materials, or combinations of such materials. A display such as display  14  may be provided on the front face of device  10 . Display  14  of  FIG. 2A  may be a touch screen display (as an example). Device  10  may have a speaker port  40  and other input-output ports. One or more buttons such as button  38  and other user input devices may be used to gather user input. As shown in  FIG. 2B , an antenna may be mounted in region  66 . Other suitable locations include regions  65  and  67 . These are merely illustrative examples. Antennas may, in general, be mounted in any suitable location within an electronic device. 
     A schematic diagram of device  10  showing how device  10  may include one or more antennas  26  and transceiver circuits that communicate with antennas  26  is shown in  FIG. 3 . Electronic device  10  of  FIG. 3  may be a portable computer such as a laptop computer, a portable tablet computer, a mobile telephone, a mobile telephone with media player capabilities, a handheld computer, a remote control, a game player, a global positioning system (GPS) device, a desktop computer, a combination of such devices, or any other suitable electronic device. 
     As shown in  FIG. 3 , electronic device  10  may include storage and processing circuitry  16 . Storage and processing circuitry  16  may include one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  16  may be used to control the operation of device  10 . Processing circuitry  16  may be based on a processor such as a microprocessor and other suitable integrated circuits. With one suitable arrangement, storage and processing circuitry  16  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. Storage and processing circuitry  16  may be used in implementing suitable communications protocols. Communications protocols that may be implemented using storage and processing circuitry  16  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, etc. 
     Input-output circuitry  15  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  18  such as touch screens and other user input interface are examples of input-output circuitry  15 . Input-output devices  18  may also include user input-output devices such as buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, etc. A user can control the operation of device  10  by supplying commands through such user input devices. Display and audio devices may be included in devices  18  such as liquid-crystal display (LCD) screens, light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), and other components that present visual information and status data. Display and audio components in input-output devices  18  may also include audio equipment such as speakers and other devices for creating sound. If desired, input-output devices  18  may contain audio-video interface equipment such as jacks and other connectors for external headphones and monitors. 
     Wireless communications circuitry  20  may include radio-frequency (RF) transceiver circuitry  23  formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  20  may include radio-frequency transceiver circuits for handling multiple radio-frequency communications bands. For example, circuitry  20  may include transceiver circuitry  22  that handles 2.4 GHz and 5 GHz bands for WiFi (IEEE 802.11) communications and the 2.4 GHz Bluetooth communications band. Circuitry  20  may also include cellular telephone transceiver circuitry  24  for handling wireless communications in cellular telephone bands such as the GSM bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz, and the 2100 MHz data band (as examples). Wireless communications circuitry  20  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  20  may include global positioning system (GPS) receiver equipment, wireless circuitry for receiving radio and television signals, paging circuits, etc. In WiFi and Bluetooth links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  20  may include antennas  26 . Some or all of antennas  26  may be cavity-backed antennas. A cavity-backed antenna includes an antenna cavity and an associated antenna resonating element. The cavity may, for example, be a substantially rectangular cavity with vertical conductive sidewalls and a planar rear surface (as an example). Antennas  26  may, if desired, include antenna windows. The antenna windows for antennas  26  may include dielectric antenna window structures and slot-based antenna windows. 
     Antennas  26  may be single band antennas that each cover a particular desired communications band or may be multiband antennas. A multiband antenna may be used, for example, to cover multiple cellular telephone communications bands. If desired, a dual band antenna may be used to cover two WiFi bands (e.g., 2.4 GHz and 5 GHz). Different types of antennas may be used for different bands and combinations of bands. For example, it may be desirable to form a dual band antenna for forming a local wireless link antenna, a multiband antenna for handling cellular telephone communications bands, and a single band antenna for forming a global positioning system antenna (as examples). 
     Transmission line paths  44  may be used to convey radio-frequency signals between transceivers  22  and  24  and antennas  26 . Radio-frequency transceivers such as radio-frequency transceivers  22  and  24  may be implemented using one or more integrated circuits and associated components (e.g., switching circuits, matching network components such as discrete inductors, capacitors, and resistors, and integrated circuit filter networks, etc.). These devices may be mounted on any suitable mounting structures. With one suitable arrangement, transceiver integrated circuits may be mounted on a printed circuit board. Paths  44  may be used to interconnect the transceiver integrated circuits and other components on the printed circuit board with antenna structures in device  10 . Paths  44  may include any suitable conductive pathways over which radio-frequency signals may be conveyed including transmission line path structures such as coaxial cables, microstrip transmission lines, etc. 
     Antennas  26  may, in general, be formed using any suitable antenna types. Examples of suitable antenna types for antennas  26  include antennas with resonating elements that are formed from patch antenna structures, inverted-F antenna structures, closed and open slot antenna structures, loop antenna structures, monopoles, dipoles, planar inverted-F antenna structures, hybrids of these designs, etc. All or part of each antenna may be formed from a conductive portion of housing  12 . For example, housing  12  or a part of housing  12  may serve as a conductive ground plane for an antenna. A conductive antenna cavity that is formed from part of housing  12 , an associated housing structure, or a separate cavity structure may be shorted to the conductive ground plane. 
     A cross-sectional view of an illustrative electronic device that contains a cavity-backed antenna located below a slot-based antenna window is shown in  FIG. 4 . As shown in  FIG. 4 , antenna  26  may have an antenna cavity  72  and antenna resonating element  70 . Antenna  26  may operate by transmitting and receiving radio-frequency antenna signals though antenna window  68 . 
     Antenna cavity  72  may be formed from conductive cavity surfaces such as conductive vertical cavity walls  74  and planar conductive cavity wall  76 . There may, for example, be five conductive cavity walls in cavity  72 . Four conductive vertical sidewalls may be connected to planar rear wall  76 . Antenna resonating element  70  may be located on the open side of cavity  72 . Antenna resonating element  70  may contain conductive antenna structures. These conductive antenna structures may be formed from wire, metal foil, portions of housing  12 , conductive support members, or other conductive materials. 
     With one suitable arrangement, the conductive structures for antenna resonating element  70  may be formed from conductive traces on a dielectric support. The conductive traces may be formed from copper or other metals (as an example). The dielectric support may be a printed circuit board or a plastic member. The printed circuit board may be rigid or flexible. Rigid printed circuit boards may be formed from epoxy (e.g., FR4) or other dielectric substrates. Flexible printed circuit boards (“flex circuits”) may be formed from flexible polymer sheets such as polyimide sheets or other flexible dielectrics. 
     Antenna  26  may be fed at positive antenna feed terminal  80  and ground antenna feed terminal  78 . Feed terminal  80  may be coupled to traces on the support structure for antenna resonating element  70 . Antenna feed terminal  78  may be shorted to conductive antenna cavity  72  and other antenna ground structures (e.g., portions of housing  12 , ground structures on antenna resonating element  70 , etc.). 
     As shown in  FIG. 4 , antenna  26  may be connected to a connector such as radio-frequency connector  88  on printed circuit board  84  by transmission line  44 . Transceiver circuitry  23  may be mounted to printed circuit board  84  and may be connected to the conductive lines in transmission line  44  via connector  88  and traces in board  84 . Transmission line  44  may have positive and ground conductors and may be used in conveying radio-frequency antenna signals between transceiver  23  and antenna  26 . 
     Antenna window  68  may be formed by placing a dielectric antenna window in an opening of housing  12 . With the illustrative arrangement shown in  FIG. 4 , antenna window  68  has been formed by forming slots  82  through a conductive housing structure (e.g., an upper conductive housing wall in housing  12 ). The longitudinal axis of each slot  82  may run into the page in the orientation of  FIG. 4  (as an example). 
     Electrical components  86  and antenna  26  may be mounted in close proximity to each other within housing  12  of device  10 . This gives rise to the potential for electromagnetic interference between components  86  and antenna  26 . The presence of antenna cavity  72  may help to reduce electromagnetic interference and may improve antenna efficiency by helping to direct radio-frequency antenna signals through slots  82  in antenna window  68 . 
     An illustrative configuration for antenna cavity  72  is shown in  FIG. 5 . As shown in  FIG. 5 , antenna cavity  72  may have a substantially rectangular shape with four conductive vertical sidewalls  74  and planar lower conductive surface  76 . Antenna cavity  72  may have a rectangular opening shape with a length LG that is longer than its width WD (as an example). Portions of antenna cavity  72  may, if desired, be formed from conductive housing structures (e.g., part of a machined metal housing  12 ). Antenna cavities may also be formed from metal traces on a dielectric support structure, from pieces of foil, from stamped or cast metal parts, etc. 
     Illustrative antenna structures that may be used in forming resonating elements  70  for antennas such as antenna  26  of  FIG. 4  include inverted-F antenna structures such as the inverted-F antenna structure of  FIG. 6 . Antenna  26  of  FIG. 6  may be fed by radio-frequency source  90  (transceiver  23 ) at positive antenna feed terminal  80  and ground antenna feed terminal  78 . Positive antenna feed terminal  80  may be coupled to antenna resonating element  70 . Ground antenna feed terminal  78  may be coupled to ground element  92 . Resonating element  70  may have a main arm  94  and a shorting branch  96  that connects main arm  94  to ground  92 . Ground  92  may be shorted to cavity  72 . 
       FIG. 7  shows an illustrative configuration that may be used for the antenna structures of antenna  26  in which resonating element  70  has multiple arms. In the  FIG. 7  example, antenna resonating element  70  has shorter arm  94 A and longer arm  94 B. Because arm  94 A is shorter than arm  94 B, arm  94 A is associated with higher frequencies of operation than arm  94 B. By using two or more separate resonating element structures of different sizes, antenna resonating element  70  can be configured to cover a wider bandwidth or more than a single communications band of interest. 
     In the example of  FIG. 8 , conductive antenna structures  98  are configured to define a closed slot  100  and an open slot  102 . The antenna formed from structures  98  of  FIG. 8  may be fed using positive antenna feed terminal  80  and ground antenna feed terminal  78 . In this type of arrangement, slots  100  and  102  serve as antenna resonating element structures for antenna  26 . The sizes of the antenna resonating element slots and their open and closed shapes may be selected so that antenna  26  operates in desired communications bands (e.g., 2.4 GHz and 5 GHz, etc.). 
     Another possible configuration for antenna  26  is shown in  FIG. 9 . In the arrangement of  FIG. 9 , antenna  26  has a single slot  104 . Antenna  26  of  FIG. 9  may be fed using positive antenna feed terminal  80  and ground antenna feed terminal  78 . Ground  78  may be associated with housing  12  or other suitable ground plane elements in device  10  such as the walls of conductive cavity  72 . 
     Antenna windows such as antenna window  68  of  FIG. 4  may be formed from slots in a conductive surface that covers antenna resonating element  70 . An illustrative slot-based antenna window is shown in  FIG. 10 . As shown in  FIG. 10 , slot-based antenna window  68  may be formed from openings  82  in conductive surface  106 . 
     Conductive surface  106  may be any conductive surface associated with electronic equipment such as electronic device  10  (e.g., a handle surface, a surface associated with a base or other support structure, a cover plate, a portion of an electronic component, etc.). In a typical scenario, conductive surface  106  is a substantially planar external conductive housing surface. Such conductive structures are sometimes referred to as device housings, devices cases, housing or case walls, housing or case surfaces, etc. 
     Openings  82  may be filled with a gaseous dielectric such as air or a solid dielectric such as plastic or epoxy. An advantage of filling openings  82  with a solid dielectric material is that this may help prevent intrusion of dust, liquids, or other foreign matter into the interior of device  10 . 
     Openings  82 , which are sometimes referred to as slots or microslots, may have any suitable shape (e.g., shapes with curved sides, shapes with bends, circular or oval shapes, non-rectangular polygonal shapes, combinations of these shapes, etc.). In a typical arrangement, which is described herein as an example, slots  82  may be substantially rectangular in shape and may have narrower dimensions (i.e., widths W measured parallel to lateral dimension  108 ) and longer dimensions (e.g., lengths L measured parallel to longitudinal slot dimension  110 ). This is merely illustrative. Slots  82  may have any suitable non-rectangular shapes (e.g., shapes with non-perpendicular edges, shapes with curved edges, shapes with bends, etc.). The use of substantially rectangular slot configurations is only described herein as an example. 
     Whether straight, curved, or having shapes with bends, the widths (i.e., the narrowest lateral dimensions) of slots  82  are generally much less than their lengths. For example, the widths of slots  82  are typically on the order of microns, tens of microns, or hundreds of microns (e.g., 5-200 microns, 10-30 microns, less than 100 microns, less than 50 microns, less than 30 microns, etc.), whereas the lengths of slots  82  are typically on the order of millimeters or centimeters (e.g., 5 mm or more, 10 mm or more, 15 mm or more, etc.). With one suitable arrangement, the lengths of slots  82  may be selected so that the slots are longer than a half of a wavelength at a desired antenna operating frequency (e.g., the lowest frequency associated with the communications bands being used). This helps to prevent slots  82  from resonating at the antenna operating frequency and thereby allows slots  82  to form a structure for antenna window  68  that is transparent to radio-frequency antenna signals at the operating frequencies of the antenna. If desired, the length of slots  82  may be selected so that the frequency response of the slots allows the slots to serve as a tuning element (e.g., a length-dependent tuning element in the lower frequency band). 
     Slots  82  that have particularly small widths (e.g., tens of microns) are generally invisible to the naked eye under normal observation. Slots  82  that have somewhat larger widths (e.g., hundreds of microns) may be barely visible, but will generally be unnoticeable under normal observation. For example, on a shiny metallic surface of a laptop computer, window  68  may be barely visible in the form of a slight change in the sheen of the surface when viewed from an oblique angle. The use of narrow slots  82  to form antenna window  68  therefore allows window  68  to be located in prominent device locations without becoming obtrusive. For example, antenna window  68  may be formed on normally exposed portions of housing  12 . Examples of normally exposed housing portions include the exterior surfaces of a laptop computer or other device  10 , surfaces of a laptop computer such as the housing surface adjacent to the keyboard or display (e.g., when the cover of a laptop computer has been opened for use), or housing sidewalls (see, e.g., antenna locations  56  and  58  of  FIG. 1A , antenna locations  60  and  62  of  FIG. 1B , and antenna locations  65 ,  66 , and  67  of  FIG. 2B ). 
     In the example of  FIG. 10 , there are seven antenna window slots  82  in antenna window  68 . This is merely illustrative. Antenna window  68  may have any suitable number of slots. For example, window  68  may have about 7-13 slots, 4-20 slots, more than 5 slots, more than 10 slots, more than 15 slots, etc. If desired, antenna window  68  may have smaller numbers of slots (e.g., 1-3 slots). In general, however, larger numbers of slots are helpful in increasing the transparency of the antenna window to radio-frequency antenna signals and may therefore be preferred. 
     Slots  82  may be spaced apart by any suitable amount. As an example, there may be about 1 to 1.5 mm, 0.5 to 2 mm, or 0.25 to 3 mm of lateral separation between adjacent pairs of slots. These are merely illustrative examples. Slots  82  may be separated by any suitable distance (e.g., less than 0.5 mm, less than 1 mm, less than 2 mm, more than 2 mm, etc.). An advantage of providing adequate separation (e.g., about 1 mm) between adjacent slots is that this helps the antenna window structure from becoming fragile due to an excessive density of slots. 
     The spacings between the slots in a given antenna window need not be uniform. For example, some slots may be spaced apart by 1 mm lateral separations and other slots may be spaced apart by 1.5 mm lateral separations. In other suitable configurations, each pair of adjacent slots may be separated by a different distance. Combinations of these slot spacing schemes may also be used. 
     If desired, the slots in antenna window  68  may have non-uniform lengths L. For example, each slot  82  may have a different length. Alternatively, some slots may have the same length and other slots may have different lengths. Slots  82  may also have different widths. The use of different combinations of slot widths, slot lengths, slot spacings, and slots shapes may be helpful when forming an antenna window around an obstacle in a given electronic device conductive surface or when forming a particular pattern of slots. Slot widths in antenna window  68  may, if desired, be made large enough to form a visible pattern on the surface of device  10  (e.g., to form a logo or other desirable antenna window pattern). In general, however, it is advantageous to ensure that the slots in window  68  are narrow enough to be invisible or unnoticeable to the naked eye under normal observation. 
     Slots  68  may be formed using any suitable technique. For example, slots may be machined in metal walls or other conductive wall structures in housing  12  using laser cutting, plasma arc cutting, micromachining (e.g., using grinding tools), or other suitable techniques. 
     Antenna cavities such as antenna cavity  72  of  FIG. 4  may be formed from portions of housing  12 , other conductive portions of device  10 , stamped, cast, or machined cavity structures, or any other suitable conductive structures. With one suitable arrangement, which is sometimes described herein as an example, the shape of antenna cavity  72  may be at least partly determined by the shape of an underlying dielectric support structure. Conductive layers of material may be formed on the dielectric support structure to form antenna cavity  72 . An example of this type of arrangement is shown in  FIG. 11 . 
     As shown in  FIG. 11 , antenna cavity  72  may have a dielectric support structure  112 . Support structure  112  may be formed from plastic or other suitable dielectric materials. Examples of plastic materials that may be used in forming support structure  112  include polycarbonate, acrylonitrile butadiene styrene (ABS) plastic, blends of plastic such as PC/ABS plastic, etc. Support structure  112  may be solid or hollow or may have both solid and hollow portions. In the example of  FIG. 11 , support structure  112  has a substantially solid rectangular shape. This is merely illustrative. Support structure  112  may have curved shapes, shapes that include curved and planar surfaces, closed shapes (e.g., shapes with no openings to an interior hollow portion), open shapes (e.g., shapes with an upper opening that exposes an internal hollow cavity region), etc. 
     In the  FIG. 11  example, support structure  112  has a rectangular shape with four vertical sidewalls and upper and lower planar surfaces. Layers of conductive materials such as copper or other metals are formed on the surfaces of the four vertical sidewalls of support structure  112  and the lower planar surface of support structure  112 . These conductive layers form vertical cavity sidewalls  74  and lower planar wall  76  for antenna cavity  72 . An antenna resonating element such as antenna resonating element  70  of  FIG. 4  may be mounted on the exposed upper surface of support structure  112 . In configurations in which support structure  112  has an opening in place of its upper surface, antenna resonating element  70  may be mounted within the opening or elsewhere in cavity  72 . 
     Any suitable fabrication technique may be used for forming conductive antenna cavity surfaces on an antenna cavity support structure such as support structure  112  of  FIG. 11 . As an example, metal can be deposited by evaporation, sputtering, or other physical vapor deposition techniques. Electrochemical deposition techniques may also be used (e.g., copper electroplating). Undesired portions of conductive layers can be removed by etching or other suitable techniques. Conductors on support structure  112  can also be patterned by selective growth techniques (e.g., by depositing a seed metal layer in a desired pattern prior to building up the metal to a desired thickness using electroplating). 
     A cross-sectional side view of an illustrative antenna  26  with a cavity formed on a dielectric support such as support  112  of  FIG. 11  is shown in  FIG. 12 . As shown in  FIG. 12 , antenna resonating element  70  may be formed on the upper surface of support structure  112 . Antenna cavity  72  may be formed from conductive layers on support  112  such as sidewall layers  74  and rear planar layer  76 . Antenna resonating element  70  may be formed from conductive traces on the surface of support  112  (e.g., copper traces formed directly on a plastic support surface) or may be formed by mounting a patterned rigid or flexible printed circuit board to support  112  (as examples). 
     An illustrative pattern of conductive traces that may be used to form antenna resonating element  70  in antenna  26  is shown in  FIG. 13 . In the example of  FIG. 13 , antenna resonating element  70  has been formed from conductive traces  114  on printed circuit board substrate  116 . Substrate  116  is surrounded by antenna ground structures such as the upper portions of the vertical walls of antenna cavity  72 . Antenna  26  may be fed by source  90  (transceiver circuitry  23 ) using positive antenna feed terminal  80  and ground antenna feed terminal  78 . Positive antenna feed terminal  80  may be coupled to antenna resonating element trace  114 . Ground antenna feed terminal  78  may be coupled to antenna ground (e.g., cavity  72 ). 
     Antenna resonating element  70  of  FIG. 13  has an inverted-F configuration in which the feed terminals  80  and  78  are located partway down the main arm of the antenna resonating element from short circuit branch SC. The main arm of trace  114  has branches that form associated lengths L 1 , L 2 , L 3 , and L 4  each of which contributes to the frequency response of antenna  26 . The frequency response of antenna resonating element  70  and antenna  26  can therefore be adjusted to cover communications bands of interest and to provide desired bandwidth by appropriate selection of the size and shape of trace  114  (e.g., the lengths L 1 , L 2 , L 3 , and L 4 ). 
     A graph in which the antenna response for an antenna formed using an antenna resonating element such as element  70  of  FIG. 13  is shown in  FIG. 14 . In the graph of  FIG. 14 , antenna response (voltage standing wave ratio—VSWR) is plotted as a function of operating frequency f. In this example, antenna  26  has been configured to cover two communications bands. The lower communications band covers frequency f 1  and is associated with long trace length L 1 . The upper communications band covers frequency f 1 . The bandwidth of the upper communications band is influenced by the different arm lengths L 2 , L 3 , and L 4  of antenna resonating element  70  ( FIG. 13 ) and has been configured so that the upper communications band has a relatively wide bandwidth. The lower and upper communications bands may correspond to 2.4 GHz and 5 GHz bands (e.g., for WiFi) or any other suitable communications bands. Antenna  26  can also be configured to handle only a single band or more than two communications bands if desired. The example of  FIGS. 13 and 14  is merely illustrative. 
     If desired, antenna  26  may be mounted in a peripheral region on upper housing  12 A (i.e., in region  58  of  FIG. 1A ). An illustrative configuration that may be used for antenna  26  when mounted in this location is shown in  FIG. 15 . As shown in  FIG. 15 , antenna cavity  72  may have a curved lower surface  76  that mates with a corresponding curved surface in recess  120 . Recess  120  may be, for example, a sunken portion of peripheral housing region  118  of upper housing  12 A. Recess  120  may be formed in an opening in a plastic bezel, in an opening in a metal housing wall or other housing structure, using frame members and other internal housing members, using parts of a housing, using a separate support structure (e.g., a dielectric insert or frame member), using other suitable device structures, or using combinations of these structures. 
     Once mounted in region  58  of housing  12 A or in other suitable portions of device  10 , antenna  26  may be covered with a dielectric (e.g., a portion of a display screen glass panel, a plastic bezel member, a dielectric antenna window, a slot-based antenna window in a conductive housing member or other conductive structure, etc.). 
       FIG. 16  shows how a curved antenna cavity such as cavity  72  may be provided with a slot-based antenna resonating element. In the  FIG. 16  example, antenna resonating element  70  has an open slot OS and a closed slot CS. Antenna resonating element  70  may, in general, have any suitable number of closed slots, any suitable number of open slots, and, if desired, additional resonating element structures (e.g., conductive traces that form resonating element arm branches of the type described in connection with  FIG. 13 , etc.). The two slot configuration of  FIG. 16  is merely illustrative. 
     As shown in  FIG. 17 , device  10  may have an upper housing  12 A with a curved edge portion such as portion  124 . Slot-based antenna window  68  may be formed in region  124  from slots  82 . Antenna resonating element  70  and antenna cavity  72  of antenna  26  may be formed adjacent to window  68 . Member  122  may be a cover glass for display  14 , a plastic cover, a conductive housing member, or other suitable structures for device  10  and housing  12 . The curved edge portion of housing  12 A and the rest of housing  12 A in  FIG. 17  may be, for example, machined aluminum. 
     As shown in  FIG. 18 , antenna  26  can be oriented so that antenna window  68  is formed on a planar inner surface of housing portion  12 A, rather than on a curved outer surface of housing portion  12 A in region  124 . 
     It is not necessary for antenna  26  to be provided with a slot-based antenna window. As shown in  FIG. 19 , for example, device  10  may have a housing such as upper housing  12 A in which a dielectric member is mounted such as dielectric member  122 . Dielectric member  122  may be, for example, a planar dielectric member such as a sheet of cover glass or plastic that is used to cover the exposed surface of display  14  ( FIG. 1 ). Antenna  26  may be oriented so that radio-frequency signals associated with antenna resonating element  70  and antenna cavity  72  may pass through a portion of dielectric member  122 , as indicated schematically by arrows  126 . Antenna  26  of  FIG. 19  may be mounted in curved peripheral region  124  of housing portion  12 A or other suitable portions of 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: 20090709
Publication Date: 20141125
Grant Date: 20141125
Priority Date: 20090709
Inventors: CHIANG BING
KOUGH DOUGLAS B.
AYALA VAZQUEZ ENRIQUE
SPRINGER GREGORY A.
XU HAO
SCHLUB ROBERT W.
CAMACHO EDUARDO LOPEZ
PASCOLINI MATTIA
GUTERMAN JERZY
JIANG YI
GOMEZ ANGULO RODNEY ANDRES
CABALLERO RUBEN
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1616", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1616", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1698", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1698", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2258", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1698", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1616", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 42555634