PATENT DOCUMENT

Publication Number: US-8102321-B2
Application Number: US-40159909-A
Country: US
Kind Code: B2

Title: Cavity antenna for an electronic device

Abstract:
A cavity antenna for an electronic device such as a portable computer is provided. The antenna may be formed from a conductive cavity and an antenna probe that serves as an antenna feed. The conductive cavity may have the shape of a folded rectangular cavity. A dielectric support structure may be used in forming the antenna cavity. A fin may protrude from one end of the dielectric support structure. The antenna probe may be formed from conductive structures mounted on the fin. An inverted-F antenna configuration or other antenna configuration may be used in forming the antenna probe. The electronic device may have a housing with conductive walls. When the cavity antenna mounted within an electronic device, a planar rectangular end face of the fin may protrude through a thin rectangular opening in the conductive walls to allow the antenna to operate without being blocked by the housing.

Claims:
1. An electronic device cavity antenna comprising:
 conductive cavity walls; 
 an inverted-F antenna probe that serves as a feed for the cavity antenna; and 
 a dielectric support structure on which the conductive cavity walls are formed, wherein the dielectric support structure has at least one fold. 
 
     
     
       2. The cavity antenna defined in  claim 1  wherein the fold comprises a 180° fold and wherein the dielectric support structure comprises a first cavity portion and a second cavity portion that are parallel to each other and that are connected at the fold. 
     
     
       3. The cavity antenna defined in  claim 1  wherein the dielectric support structure comprises a fin on which the inverted-F antenna probe is formed. 
     
     
       4. The cavity antenna defined in  claim 3  wherein conductive structures are formed on both sides of the fin that serve as ground for the inverted-F antenna probe. 
     
     
       5. The cavity antenna defined in  claim 4  wherein the inverted-F antenna probe comprises an antenna resonating element having first and second parallel shorting branches that short the antenna resonating element to at least some of the conductive structures. 
     
     
       6. The cavity antenna defined in  claim 5  wherein the conductive structures are electrically connected to the conductive cavity walls. 
     
     
       7. A cavity antenna, comprising:
 a dielectric support structure with at least one substantially 180° fold; 
 conductive walls on the dielectric support structure that form a folded antenna cavity for the cavity antenna; and 
 an antenna probe that serves as an antenna feed for the cavity antenna. 
 
     
     
       8. The cavity antenna defined in  claim 7  wherein the dielectric support structure has a cavity thickness and has a fin, wherein the fin has a fin thickness that is thinner than the cavity thickness. 
     
     
       9. The cavity antenna defined in  claim 8  wherein the antenna probe comprises an antenna resonating element on the fin. 
     
     
       10. The cavity antenna defined in  claim 9  wherein the antenna resonating element comprises an inverted-F antenna resonating element. 
     
     
       11. An electronic device, comprising:
 a conductive housing having an opening; and 
 a cavity antenna having a dielectric support structure with a fin in the opening, wherein the conductive housing comprises metal walls in which the opening is formed and wherein the fin has a fin end face that passes through the opening. 
 
     
     
       12. The electronic device defined in  claim 11  wherein the cavity antenna comprises a folded cavity. 
     
     
       13. The electronic device defined in  claim 12  wherein the cavity antenna comprises an inverted-F antenna probe portion formed on the fin. 
     
     
       14. The electronic device defined in  claim 13  further comprising a coaxial cable that feeds the cavity antenna, wherein the fin has first and second sides and wherein the coaxial cable has a center conductor that extends through the fin from the first side to the second side. 
     
     
       15. The electronic device defined in  claim 11  further comprising a coaxial cable that feeds the cavity antenna, wherein the fin has first and second sides and wherein the coaxial cable has a center conductor that extends through the fin from the first side to the second side. 
     
     
       16. The electronic device defined in  claim 15  wherein the dielectric support structure has a 180° fold and wherein the cavity antenna comprises a folded cavity with conductive walls. 
     
     
       17. The electronic device defined in  claim 16  wherein the electronic device comprises a portable computer having a battery that is separated from the conductive housing by a gap and wherein the cavity antenna is mounted within the gap. 
     
     
       18. The electronic device defined in  claim 11  wherein the fin end face that passes through the opening is flush with an outer surface of the metal walls. 
     
     
       19. The electronic device defined in  claim 11 , wherein the opening is substantially rectangular and wherein the fin end face that passes through the opening comprises a substantially rectangular planar fin end face. 
     
     
       20. A portable computer, comprising:
 a conductive housing having an opening; 
 radio-frequency transceiver circuitry within the conductive housing; and 
 a cavity antenna coupled to the radio-frequency housing, wherein the cavity antenna has a dielectric support structure with a fin structure in the opening and wherein the fin has a fin end face that passes through at least part of the opening. 
 
     
     
       21. The portable computer defined in  claim 20  wherein the conductive housing comprises metal walls in which the opening is formed. 
     
     
       22. The portable computer defined in  claim 20  wherein at least some of the metal walls form a base for the portable computer. 
     
     
       23. The portable computer defined in  claim 22 , wherein the opening is substantially rectangular and wherein the fin end face that passes through at least part of the opening comprises a substantially rectangular planar fin end face.

Description:
BACKGROUND 
     This invention relates to electronic devices and, more particularly, to antennas for electronic devices. 
     Portable computers and other electronic devices often use wireless communications circuitry. For example, wireless communications circuitry may be used to communicate with local area networks and remote base stations. 
     Wireless computer communications systems use antennas. It can be difficult to design antennas that perform satisfactorily in electronic devices such as portable computers. It is generally desirable to create efficient antennas. For example, efficient antennas are desirable for portable computers, because efficient antennas help conserve battery power during wireless operations. However, optimum antenna efficiency can be difficult to obtain, because portable computer designs restrict the possible locations for implementing the antennas and require that the antennas be constructed as small light-weight structures. For example, it can be difficult to implement efficient antennas in portable computers that contain conductive housing structures, because the conductive housing structures can block radio-frequency signals and thereby reduce the effectiveness of the antennas. 
     It would therefore be desirable to be able to provide improved antenna arrangements for electronic devices such as portable computers. 
     SUMMARY 
     An antenna for an electronic device such as a portable computer is provided. The antenna may use a cavity-backed configuration in which conductive cavity walls are placed in the vicinity of an antenna feed structure formed from an antenna probe. 
     A dielectric support structure may be provided for the cavity antenna. The dielectric support structure may have a folded rectangular cavity shape. Conductive sidewalls such as metal sidewalls may be formed over the surface of the folded rectangular support structure to form a conductive cavity for the cavity antenna. 
     A fin may protrude from one end of the dielectric support structure near an opening in the cavity walls. The fin may be used in forming the antenna probe. An inverted-F configuration may be used in forming the antenna probe. With this type of arrangement, an antenna resonating element arm may be mounted on the fin. 
     One or more conductive branches may be used to selectively short portions of the antenna resonating element arm to ground. Ground plane structures for the inverted-F antenna may be formed from portions of the conductive cavity walls on the front and back of the fin. 
     A transmission line such as a coaxial cable may be coupled to the antenna probe at antenna feed terminals. A center conductor in the coaxial cable may pass from the back of the fin to the front of the fin. On the front of the fin, the center conductor may be electrically connected to the antenna resonating element arm of the inverted-F antenna. An outer ground conductor in the coaxial cable can be shorted to the ground plane structures on the rear surface of the fin. 
     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 portable computer in which an antenna may be implemented 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 showing where antennas may be located in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an interior portion of an electronic device such as a portable computer showing gaps that may be provided to space internal components away from housing walls and that may be used to house antennas in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of an illustrative electronic device such as a portable computer showing how an antenna that is located between an internal component such as a battery and a conducive housing wall may have a thin portion such as a dielectric fin that is used to convey electromagnetic signals through a gap in the conductive housing in accordance with an embodiment of the present invention. 
         FIG. 5  is a front view of an illustrative portable computer housing showing how an antenna of the type shown in  FIG. 4  may have a slot-shaped dielectric face through which electromagnetic signals pass in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of an illustrative antenna having a cavity portion and an antenna probe portion that serves as an antenna feed for the antenna in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of an antenna of the type shown in  FIG. 6  in which the cavity portion of the antenna has been folded to conserve space in accordance with an embodiment of the present invention. 
         FIG. 8  is cross-sectional side view of an illustrative antenna of the type shown in  FIG. 7  in which the antenna has a thin dielectric fin portion that serves to convey radio-frequency signals through a gap in a conductive housing in accordance with an embodiment of the present invention. 
         FIG. 9  is a perspective view of dielectric support structure portions of an antenna of the type shown in  FIG. 8  in accordance with an embodiment of the present invention. 
         FIG. 10  is a rear perspective view of an antenna of the type shown in  FIG. 8  in which inner dielectric support structures have been covered with a conductive material such as metal to form the antenna cavity and antenna probe in accordance with an embodiment of the present invention. 
         FIG. 11  is a front perspective view of an antenna of the type shown in  FIG. 8  in which inner dielectric support structures have been covered with a conductive material such as metal to form the antenna cavity and antenna probe in accordance with an embodiment of the present invention. 
         FIG. 12  is a rear view of an antenna of the type shown in  FIG. 8  showing how a coaxial cable may have an outer ground conductor connected to a rear ground plane element on the antenna and may have a center conductor that serves as a positive antenna feed and that is routed to the front side of the antenna through a hole in the dielectric fin portion of the antenna in accordance with an embodiment of the present invention. 
         FIG. 13  is a side view of an illustrative dielectric support structure for an antenna with a folded cavity showing how a gap may be formed between folded portions of the dielectric support to accommodate conductive cavity layers in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to antenna structures for electronic devices. The antennas may be used to convey wireless signals for suitable communications links. For example, an electronic device antenna may be used to handle communications for a short-range link such as an IEEE 802.11 link (sometimes referred to as WiFi®) or a Bluetooth® link. An electronic device antenna may also handle communications for long-range links such as cellular telephone voice and data links. 
     Antennas such as these may be used in various electronic devices. For example, an antenna may be used in an electronic device such as a handheld computer, a miniature or wearable device, a portable computer, a desktop computer, a router, an access point, a backup storage device with wireless communications capabilities, a mobile telephone, a music player, a remote control, a global positioning system device, devices that combine the functions of one or more of these devices and other suitable devices, or any other electronic device. With one suitable arrangement, which is sometimes described herein as an example, the electronic devices in which the antennas are provided may be portable computers such as laptop (notebook) computers. This is, however, merely illustrative. Antennas may, in general, be provided in any suitable electronic device. 
     An illustrative electronic device such as a portable computer in which an antenna may be provided is shown in  FIG. 1 . As shown in  FIG. 1 , portable computer  10  may have a housing  12 . Housing  12 , which is sometimes referred to as a case, may be formed from one or more individual structures. For example, housing  12  may have a main structural support member that is formed from a solid block of machined aluminum or other suitable metal. Multipart housings may be used in which two or more individual housing structures are combined to form housing  12 . The structures in housing  12  may include internal frame members, external coverings such as sheets of metal, etc. Housing  12  and its associated components may, in general, be formed from any suitable materials such as such as plastic, ceramics, metal, glass, etc. An advantage of forming housing  12  at least partly from metal is that metal is durable and attractive in appearance. Metals such as aluminum may be anodized to form an insulating oxide coating. 
     Case  12  may have an upper portion  26  and a lower portion  28 . Lower portion  28  may be referred to as the base unit housing or main unit of computer  10  and may contain components such as a hard disk drive, battery, and main logic board. Upper portion  26 , which is sometimes referred to as a cover or lid, may rotate relative to lower portion  28  about rotational axis  16 . Portion  18  of computer  10  may contain a hinge and associated clutch structures and may sometimes be referred to as a clutch barrel. 
     Lower housing portion  28  may have an opening such as slot  22  through which optical disks may be loaded into an optical disk drive. Lower housing portion  28  may also have touchpad  24 , keys  20 , and other input-output components. Touch pad  24  may include a touch sensitive surface that allows a user of computer  10  to control computer  10  using touch-based commands (gestures). A portion of touchpad  24  may be depressed by the user when the user desires to “click” on a displayed item on screen  14 . If desired, additional components may be mounted to upper and lower housing portions  26  and  28 . For example, upper and lower housing portions  26  and  28  may have ports to which cables can be connected (e.g., universal serial bus ports, an Ethernet port, a Firewire port, audio jacks, card slots, etc.). Buttons and other controls may also be mounted to housing  12 . 
     If desired, upper and lower housing portions  26  and  28  may have transparent windows through which light may be emitted from light-emitting diodes. Openings such as perforated speaker openings  30  may also be formed in the surface of housing  12  to allow sound to pass through the walls of the housing. 
     A display such as display  14  may be mounted within upper housing portion  26 . Display  14  may be, for example, a liquid crystal display (LCD), organic light emitting diode (OLED) display, or plasma display (as examples). A glass panel may be mounted in front of display  14 . The glass panel may help add structural integrity to computer  10 . For example, the glass panel may make upper housing portion  26  more rigid and may protect display  14  from damage due to contact with keys or other structures. 
     Portable computer  10  may contain circuitry  32 . Circuitry  32  may include storage and processing circuitry  32 A and input-output circuitry  32 B. 
     Storage and processing circuitry  32 A 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. Storage and processing circuitry  32 A may be used in controlling the operation of computer  10 . Processing circuitry in circuitry  32 A may be based on processors such as microprocessors, microcontrollers, digital signal processors, dedicated processing circuits, power management circuits, audio and video chips, and other suitable integrated circuits. Storage and processing circuitry  32 A may be used to run software on computer  10 , such as operating system software, application software, software for implementing control algorithms, communications protocol software etc. 
     Input-output circuitry  32 B may be used to allow data to be supplied to computer  10  and to allow data to be provided from computer  10  to external devices. Examples of input-output devices that may be used in computer  10  include display screens such as touch screens (e.g., liquid crystal displays or organic light-emitting diode displays), buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers and other devices for creating sound, cameras, sensors, etc. A user can control the operation of computer  10  by supplying commands through these devices or other suitable input-output circuitry  32 B. Input-output circuitry  32 B may also be used to convey visual or sonic information to the user of computer  10 . Input-output circuitry  32 B may include connectors for forming data ports (e.g., for attaching external equipment such as accessories, etc.). 
     Computer  10  may include one or more antennas. For example, computer  10  may include one or more cavity-backed antennas. Computer  10  may also include one or more additional antennas. The antennas in computer  10  may be coupled to wireless communications circuitry (e.g., radio-frequency transceiver circuits) in input-output circuitry  32 B using coaxial cables, microstrip transmission lines, or other suitable transmission lines such as transmission line  34 . 
     The antenna structures in computer  10  may be used to handle any suitable communications bands of interest. For example, antennas and wireless communications circuitry in circuitry  32 B of computer  10  may be used to handle cellular telephone communications in one or more frequency bands and data communications in one or more communications bands. Typical data communications bands that may be handled by the wireless communications circuitry in computer  10  include the 2.4 GHz band that is sometimes used for Wi-Fi® (IEEE 802.11) and Bluetooth® communications, the 5 GHz band that is sometimes used for Wi-Fi communications, the 1575 MHz Global Positioning System band, and 2G and 3G cellular telephone bands. These bands may be covered using single-band and multiband antennas. For example, cellular telephone communications can be handled using a multiband cellular telephone antenna. A single band antenna may be provided to handle Bluetooth® communications. Computer  10  may, as an example, include a multiband antenna that handles local area network data communications at 2.4 GHz and 5 GHz (e.g., for IEEE 802.11 communications), a single band antenna that handles 2.4 GHz IEEE 802.11 communications and/or 2.4 GHz Bluetooth® communications, or a single band or multiband antenna that handles other communications frequencies of interest. These are merely examples. Any suitable antenna structures may be used by computer  10  or other electronic device to cover communications bands of interest. 
     The antennas in computer  10  may be implemented using any suitable antenna configuration. For example, an antenna for computer  10  may be implemented as a cavity antenna, a monopole antenna, a dipole antenna, a patch antenna, an inverted-F antenna, an L-shaped antenna, a planar inverted-F antenna (PIFA), a slot antenna, a helical antenna, a hybrid antenna including two or more of these antenna structures, or any other suitable antenna structures. 
     With one suitable arrangement, which is described herein as an example, at least one of the antennas used in computer  10  is implemented using a cavity antenna arrangement. With this type of configuration, a conductive cavity is formed from conductive materials such as metal. An antenna probe structure is formed adjacent to an opening in the antenna cavity. The antenna probe structure may be coupled to a transmission line such as a coaxial cable. During operation, the antenna probe may excite the cavity antenna and thereby serve as a feed for the antenna. 
     The cavity may have cavity walls. The cavity walls may be formed by conductive structures such as housing structures or may be formed from metal layers or other conductive layers that are supported by a dielectric support structure. The dielectric support structure may be formed from a dielectric such as fiberglass-filled epoxy or fiberglass-filled polyarylamide. Other dielectrics may also be used if desired. 
     The cavity may be folded along its length so that the cavity may be mounted within a relatively confined space such as the interior of housing  12  without excessively decreasing its length. The fold in the cavity may have any suitable shape. For example, the fold may form a 180° bend in the cavity. 
     A thinned portion of the dielectric support structure may form a fin-shaped protrusion. The fin may be used for supporting portions of the antenna probe. The fin may also be used to help the antenna convey radio-frequency signals through a gap in housing  12  or other conductive device structures. The fin may have a thin profile that allows the antenna to be used in devices with correspondingly thin gaps. For example, the fin may have a thickness of about 0.2 mm, which allows the antenna to be used in devices with conductive housings having gaps (i.e., slot-shaped surface openings) of about 0.2 mm. The length of this type of opening and the corresponding lateral dimension of the fin of the antenna may be, for example, about 60 mm (as an example). 
     Because the antenna can be used to convey signals in and out of a housing that has a gap of only about 0.2 mm (as an example), the antenna can be used in portions of electronic device  10  in which larger and more visible structures would not be acceptable. In general, the antenna may be used to convey signals through any suitable opening in housing  12 . Examples of gaps in which the antenna may be used include gaps formed between mating housing portions (e.g., a lid and base, a cover and lid, a cover and base, etc.) and gaps in a single housing portion (e.g., a gap formed in a lid, a gap formed in a base housing structure, a gap formed in a housing sidewall, etc.). Illustrative locations at which gaps such as these may be formed in housing  12  of electronic device  10  and which may therefore serve as suitable locations for mounting the cavity antenna include lower edge locations such as locations  36  and  38  in  FIG. 2 . 
     Electronic device  10  may include a battery and other internal components. Electrical components in the interior of housing  12  may sometimes be intentionally spaced by a certain distance from the interior surfaces of housing walls in housing  12 . This helps the structures of device  10  to survive sharp impacts of the type that may arise if a user inadvertently drops the electronic device to the ground. As shown in  FIG. 3 , for example, device  10  may have gaps such as gaps  42  between housing portion  28  of housing  12  and component  40 . Component  40  may be, for example, a battery or other electrical component within the interior of device  10 . Gaps  42  may prevent damage to battery  40  upon impact. At least some of the space provided by gaps  42  may, if desired, be used to house antenna  44 . 
     As shown in  FIG. 4 , for example, antenna  44  may be mounted within opening  42  between interior surface  49  of the wall of housing  12  and surface  51  of battery  40 . Antenna  44  may have a fin portion such as fin  48  mounted to a larger body portion such as body  46 . The end of fin  48  may form a flat planar region such as planar fin end surface  53  (as an example). When mounted as shown in  FIG. 4 , fin  48  may extend from the interior of device  10  and housing  12  to the exterior of device  10  and housing  12  through opening  50 . If desired, front face  53  of fin  48  may lie flush with the exterior surface of housing  12 . 
     A front view of opening  50  from the exterior of device  10  is shown in  FIG. 5 . As shown in  FIG. 5 , opening  50  may have a substantially rectangular shape (as an example). The thickness of opening  50  may be relatively thin compared to its width. With this type of arrangement, rectangular planar fin end surface  53  may have one lateral dimension (i.e., thickness T) that is much smaller (e.g., 5 times smaller or more, ten times smaller or more, etc.) than its other lateral dimension (i.e., width W). With one illustrative arrangement, dimension T may be about 0.2 mm and dimension W may be about 60 mm (as an example). In some configurations, such as the portable computer configuration shown in  FIG. 1 , different portions of housing  12  (e.g., upper housing portion  26  and lower housing portion  28 ) may be placed in either an open position (as shown in  FIG. 1 ) or a closed position. In the closed position, housing portions  12  may meet along an interface such as interface  52 . Interface  52  may include elastomeric gasket structures or other structures that allow fin end portion  53  to protrude through opening  50 . If desired, opening  50  may be formed directly through a rigid housing wall. Openings such as opening  50  may also be formed partly from elastomeric gasket structures and partly from openings in rigid housing walls in housing  12 . Other arrangements may be used if desired. The illustrative configuration for opening  50  that is shown in  FIGS. 4 and 5  is merely illustrative. 
     As shown in  FIG. 6 , antenna  44  may have a cavity portion such as cavity  62  and a probe portion such as probe  54 . Probe  54  may have antenna feed terminals such as positive antenna feed terminal  58  and ground antenna feed terminal  56  and may serve as an antenna feed for antenna  44 . Cavity  62  may be formed from conductive cavity walls such as walls  64 . Walls  64  and the conductive structures of probe  54  may be formed from conductive materials such as metal. In device  10 , a coaxial cable or other transmission line  34  may have positive and ground lines that are respectively connected to antenna feed terminals  58  and  56 . During operation, when antenna  44  is transmitting and receiving radio-frequency antenna signals, the electric field component of the antenna signals may be oriented as shown by electric field polarization vectors  66  of  FIG. 6  (i.e., with the electric field E oriented transversely across the interior width WD of cavity  62 , perpendicular to its longer dimension, length L). 
     Cavity  62  may have conductive members such as walls  64  formed on a dielectric support that forms the shape of antenna body  46  ( FIG. 4 ). Antenna probe  54  may be used to excite cavity  62  and thereby couple transmission line  34  ( FIG. 1 ) to antenna  44 . Any suitable antenna structure may be used for probe  54 . With one suitable arrangement, which is sometimes described herein as an example, antenna probe  54  is formed from an inverted-F antenna structure. As shown in  FIG. 6 , this type of antenna probe may have an antenna resonating element  60  that is separated by gap  57  from cavity wall  64 . Positive antenna feed terminal  58  may be electrically connected to antenna resonating element  60  and ground antenna feed terminal  56  may be electrically connected to conductive antenna wall  64 . In this context, the portions of wall  64  that are separated from antenna resonating element  60  by gap  57  serve as a ground element for the inverted-F antenna structure formed from antenna resonating element  60 . 
     Probe  54  may, if desired, have other configurations. For example, additional conductive members may be placed in the vicinity of antenna resonating element  60  to serve as additional ground structures for probe  54 . Moreover, other antenna designs may be used for probe  54 . The use of an inverted-F antenna structure for antenna probe  54  of antenna  44  is merely illustrative. 
     As shown in  FIG. 7 , cavity  62  may be folded back on itself or otherwise configured to make antenna  44  more compact while maintaining a given cavity length. In the  FIG. 7  example, cavity  62  has been folded once with a 180° fold, so that the interior of antenna  44  is formed from body region  46 A and parallel body region  46 B. Body region  46 B is folded back on body region  46 A, so that antenna dimension L 2  is roughly half of original unfolded cavity length L ( FIG. 6 ), while the overall cavity length L is unchanged. In this type of configuration, dimension WD 2  (i.e., the width or thickness of cavity body  46 ) may increase slightly (i.e., to twice that of width/thickness dimension WD of  FIG. 6 ), but because the length L 2  is substantially less than length L of  FIG. 6 , an antenna with a folded configuration of the type shown in  FIG. 7  will sometimes be more capable of fitting within relatively confined housing locations than an antenna with an unfolded configuration of the type shown in  FIG. 7 . Configurations with cavities that have more folds or that have folds with different angles may also be used. The example of  FIG. 7  in which cavity  62  has been provided with a single 180° fold is merely illustrative. 
     A cross-sectional side view of an illustrative folded cavity antenna such as antenna  44  of  FIG. 7  that has been mounted within housing  12  of device  10  is shown in  FIG. 8 . As shown in  FIG. 8 , antenna  44  may be fed by a transmission line  34  such as a coaxial cable. Fin portion  48  of antenna  44  may pass through opening  50  in housing  12 . In the example of  FIG. 8 , housing  12  is formed from housing portions  12 A and  12 B. Housing portion  12 A may be, for example, a cover portion that covers interior components  70  such as battery  40  of  FIG. 3  within the interior of device  10 . Housing portion  12 B may be, for example, a main housing unit. Antenna  44  may be mounted to interior surfaces of housing portion  12 B using adhesive  72  or other suitable mounting structures. Body  46  may have a folded configuration of the type described in connection with  FIG. 7 . In this type of configuration, dimension D 1  may be about 2.5 mm, dimension D 2  may be about 7 mm, and dimension D 3  may be about 1.5 mm, which helps make antenna  44  compact and able to fit. 
     Cavity antenna  44  may be implemented by forming conductive cavity walls over a dielectric support structure. An illustrative dielectric support structure for antenna  44  is shown in the perspective view of  FIG. 9 . As shown in  FIG. 9 , dielectric support structure  74  may have a portion that forms fin  28  and a portion that forms body  46  for antenna  44 . (The conductive portions of antenna  44  are not shown in  FIG. 9 .) Coaxial cable  34  may be cradled along a recessed portion in the rear of dielectric support structure  74 . Cable  34  may have a conductive outer braid conductor and a center conductor or other suitable conductive lines. The outer conductor may serve as a ground conductor and may be coupled to planar ground structures in antenna  44  such as portions of conductive cavity sidewalls using a conductive ground terminal such as terminal  56  of  FIG. 6 . The center conductor may serve as a positive transmission line conductor and may be coupled to antenna terminal  58  ( FIG. 6 ). Terminal  58  may, for example, be formed on the front side of antenna fin  28 . A conductive member such as pin  76  may be used to route the center conductor of cable  34  on the back side of fin  28  to positive antenna terminal  58  and associated resonating element structures on the front side of fin  28 . 
       FIG. 10  is a perspective view of antenna  44  of  FIG. 9  as viewed from the rear of dielectric support structure  74 . As shown in  FIG. 10 , support structure  74  may be covered with conductive structures  78  such as metal layers. The metal layers may include patterned copper traces or other metal structures. These metal structure may include planar metal regions (e.g., for the sidewalls of the antenna cavity) and narrower lines (e.g., for forming portions of probe  54  ( FIG. 6 ). Portion  80  of dielectric support structure  74  may be recessed to accommodate coaxial cable  34 . 
     Dielectric support structure  74  may be formed from any suitable dielectric such as fiberglass-filled epoxy or fiberglass-filled polyarylamide. If desired, materials such as flexible printed circuit board materials (e.g., polyimide) and rigid printed circuit board materials (e.g., fiberglass-filled epoxy) may be used in the cavity antenna. 
     An advantage of using a solid dielectric in forming some or all of dielectric support structure  74  is that this type of arrangement may help prevent intrusion of dust, liquids, or other foreign matter into portions of antenna cavity  62 . Dielectric in cavity  62  may also be used as a structural support that physically helps hold cavity walls  64  and other conductive antenna structures in place. Dielectric materials are transparent to radio-frequency signals, so dielectric materials may be used in portions of cavity antenna  44  where it is desired not to block radio-frequency signals. 
     In general, any suitable dielectric material can be used to form dielectric cavity antenna structures for computer  10 . Dielectric structures that surround or are located within the cavity of a cavity antenna may be formed from a completely solid dielectric, a porous dielectric, a foam dielectric, a gelatinous dielectric (e.g., a coagulated or viscous liquid), a dielectric with grooves or pores, a dielectric having a honeycombed or lattice structure, a dielectric having spherical voids or other voids, a combination of such non-gaseous dielectrics, etc. Hollow features in solid dielectrics may be filled with air or other gases or lower dielectric constant materials. Examples of dielectric materials that may be used in a cavity antenna and that contain voids include epoxy with gas bubbles, epoxy with hollow or low-dielectric-constant microspheres or other void-forming structures, polyimide with gas bubbles or microspheres, etc. Porous dielectric materials used in a cavity antenna in device  10  can be formed with a closed cell structure (e.g., with isolated voids) or with an open cell structure (e.g., a fibrous structure with interconnected voids). Foams such as foaming glues (e.g., polyurethane adhesive), pieces of expanded polystyrene foam, extruded polystyrene foam, foam rubber, or other manufactured foams can also be used in a cavity antenna in device  10 . If desired, the dielectric antenna materials can include layers or mixtures of different substances such as mixtures including small bodies of lower density material. 
     The conductive antenna elements that form the sidewalls and other portions of a cavity antenna may be formed from conductive portions of housing  12 , conductive sheets such as planar metal sheets, wires, traces on rigid printed circuit boards or flex circuit substrates, stamped metal foil patterns, milled or cast metal parts, or any other suitable conductive structures. 
     Any suitable fabrication techniques may be used in forming an antenna having conductive structures such as these. For example, certain surface regions of dielectric support structure  74  may be selectively activated for subsequent metal plating operations using light (e.g., using laser light). With this type of approach, metal will only adhere to dielectric support structure  74  during electroplating operations in the surface regions that were exposed to the laser light. Unexposed portions of dielectric support structure  74  will remain uncovered with metal. Light deactivation schemes may also be used where metal adheres to only those portions of dielectric that have not been exposed to light. 
     With another suitable arrangement, plastic for dielectric support structure  74  is molded using a so-called double-shot technique. One portion of the dielectric (the first “shot”) is injected to form a first part of the support, followed by injection of a second dielectric shot to form a second part of the support. Because of the different metal adhering qualities of the first and second shots, metal will only adhere to one of the two shots during electroplating operation (e.g., to the second shot portions). 
     Dielectric support structure  74  can also be provided with patterned metal layers by coating all or some of dielectric support structure  74  with metal and ablating undesired portions of the coating. Ablation operations may be implemented using a pulsed laser (as an example). 
     In another illustrative arrangement, masking techniques are used to pattern conductive structures on dielectric support structure  74 . As an example, dielectric support structure  74  can be coated with a layer of metal. The metal layer can then be coated with a layer of photoresist, which is exposed and developed in a desired pattern (e.g., using a photomask or directed laser light). Unprotected metal surfaces can then be removed by etching. Tape and other substances can also be used as mask layers. If desired, patterned conductors for antenna  44  can be formed using conductive ink. 
     Illustrative conductive structures that may be formed on dielectric support structure  74  are shown in  FIG. 11 . In the example of  FIG. 11 , conductive traces have been formed on dielectric support structure  74  that form an inverted-F antenna (probe  54 ). Probe  54  of  FIG. 11  is formed from inverted-F antenna resonating element  60 . antenna resonating element  60  has a shorting branch  82  at one end of antenna resonating element  60  that shorts antenna resonating element  60  to ground portions  86  of cavity sidewalls  64 . Antenna resonating element  60  also has a second branch  84  that shorts the main arm of antenna resonating element  60  to ground structures  86  at an intermediate location along antenna resonating element  60 . Positive antenna feed terminal  58  may be connected to antenna resonating element  60  at a location that is to the left of both arms  84  and  82  (in the orientation of  FIG. 11 ). With this type of arrangement, arms  84  and  82  are spaced from antenna terminal  58  at two respective distances along the longitudinal axis of antenna resonating element  60  (i.e., arm  84  is closer to antenna terminal  58  than arm  82 ). The position of each arm along element  60  contributes a different impedance to antenna  44 . These different impedance contributions tend to broaden the bandwidth of the antenna. If desired, other feed positions can be used for probe  54 . For example, antenna feed terminal  58  may be located at different locations along arm  60 . 
       FIG. 12  is a rear view of antenna  44  showing how coaxial cable  34  may have a center conductor such as center conductor  88  that passes through a hole in dielectric support structure  74  and thereby connects to antenna terminal  58  on the front of fin  28 . Center conductor  88  may be surrounded by an insulator such as insulating jacket  92 . Outer conductor  96  may be connected to the metal layers on dielectric support structure  74  such as cavity wall metal layers  64  in regions such as region  90  (e.g., using solder, welds, conductive adhesive, conductive paste, etc.). Metal  64  may have a rectangular portion such as rectangular portion  98  that extends up the lower side of fin  28  and forms a secondary portion of the ground for antenna probe  54 . Notch  94  in ground plane  98  helps allow center conductor  88  to pass from the rear of antenna  44  to the front of antenna  44  without becoming shorted to antenna cavity walls  64  in portion  98 . With this type of configuration, ground plane structures  86  of  FIG. 11  forms a first ground plane that is co-planar with antenna probe  54 . Ground plane structures  86  are relatively easy to access, which allows the shape and size of front-side ground plane structures  86  to be modified to tune antenna  44  (if desired). Ground plane structures  98  of  FIG. 12  form a second ground plane on the opposite side of fin  28 . This second ground plane helps to excite the electric field E in fin  28 . This field, in turn, excites the field E in cavity  62  ( FIG. 7 ) that is ultimately radiated out of antenna  44  during signal transmission operations. 
     As shown in the cross-sectional view of  FIG. 13 , dielectric support structure  74  may include a gap  100  that is filled with conductor to form the sidewalls  64  of cavity  62 . Conductor may be formed in gap  100  using any suitable technique (e.g., by inserting a layer of foil in gap  100 , by folding an unfolded dielectric support structure  74  that is coated with foil or plated metal layers, etc.). 
     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: 20090310
Publication Date: 20120124
Grant Date: 20120124
Priority Date: 20090310
Inventors: CHIANG BING
SPRINGER GREGORY A.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q9/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 42730261