PATENT DOCUMENT

Publication Number: US-8174452-B2
Application Number: US-23838408-A
Country: US
Kind Code: B2

Title: Cavity antenna for wireless electronic devices

Abstract:
Wireless portable electronic devices such as laptop computers are provided with cavity-backed monopole antennas. A wireless device may have a housing. Conductive portions of the housing such as a conductive outer metal layer and internal frame structures may form a cavity having conductive walls. An antenna resonating element structure may be formed from monopole antenna resonating element arms of dissimilar lengths. One of the arms may be straight and another of the arms may be implemented using a meandering path. The antenna resonating element may be mounted over the cavity to form a cavity-backed monopole antenna. A display within the device may be covered by a cover glass. An opaque bezel region around the periphery of the cover glass may cover the antenna and block it from view. The antenna resonating element arms may run parallel to the longitudinal axis of the cavity.

Claims:
1. A cavity-backed monopole antenna for a portable wireless electronic device, comprising:
 a conductive cavity having a longitudinal axis; and 
 a monopole antenna resonating element structure with at least one conductive portion having a longitudinal axis parallel to the longitudinal axis of the cavity, wherein the monopole antenna resonating element structure has at least two traces that form at least first and second arms, wherein the first arm and the second arms have different lengths and each support radio-frequency communications with the cavity-backed monopole antenna in different and overlapping first and second frequency ranges. 
 
     
     
       2. The cavity-backed monopole antenna defined in  claim 1  wherein the portable electronic device has a metal frame and wherein portions of the metal frame comprise conductive sidewalls for the cavity. 
     
     
       3. A portable electronic device, comprising:
 housing structures defining a conductive cavity; and 
 an antenna resonating element structure formed on a substrate that is mounted to the cavity to form a cavity-backed antenna for the portable electronic device, wherein circuitry is mounted to the substrate. 
 
     
     
       4. The portable electronic device defined in  claim 3  further comprising:
 glass that covers the antenna resonating element structure. 
 
     
     
       5. The portable electronic device defined in  claim 4  wherein at least one spacer is mounted on the antenna resonating element structure that protects the antenna resonating element structure. 
     
     
       6. The portable electronic device defined in  claim 3 , wherein the circuitry comprises electrical components and wherein the antenna resonating element structure comprises a printed circuit board having an opening through which the electrical components protrude. 
     
     
       7. The portable electronic device defined in  claim 3  further comprising a cover having a metal layer and a metal frame, wherein the metal layer forms a lower surface of the cavity and wherein the frame forms sidewalls for the cavity. 
     
     
       8. The portable electronic device defined in  claim 7  further comprising:
 a display; and 
 a cover glass that covers the display, wherein the cover glass has a bezel portion that overlaps the cavity. 
 
     
     
       9. The portable electronic device defined in  claim 8  wherein the bezel portion is opaque and blocks the antenna from view. 
     
     
       10. The portable electronic device defined in  claim 3  wherein the antenna operates at a desired communications frequency and wherein the cavity has dimensions substantially less than a half of a wavelength at the desired communications frequency. 
     
     
       11. The portable electronic device defined in  claim 10  further comprising:
 an upper housing portion that contains the antenna; and 
 a lower housing portion to which the upper housing portion is rotationally mounted, wherein the desired communications frequency is in the range of 2.4 GHz to 2.5 GHz, wherein the portable electronic device further comprises a communications path that connects the antenna to circuitry in the lower housing portion, and wherein the communications path includes a flex circuit. 
 
     
     
       12. A portable electronic device, comprising:
 housing structures defining a conductive cavity; and 
 an antenna resonating element structure mounted to the cavity to form a cavity-backed antenna for the portable electronic device, wherein circuitry is mounted to the antenna resonating element structure, and wherein the cavity has a longitudinal axis and wherein the antenna resonating element structure has conductive traces that form multiple antenna resonating element arms that run substantially parallel to the longitudinal axis. 
 
     
     
       13. A portable electronic device, comprising:
 housing structures defining a conductive cavity; and 
 an antenna resonating element structure mounted to the cavity to form a cavity-backed antenna for the portable electronic device, wherein circuitry is mounted to the antenna resonating element structure, and wherein the antenna resonating element structure comprises straight and meandering antenna resonating element arms. 
 
     
     
       14. An antenna comprising:
 a conductive cavity formed at least partially from conductive structures in a laptop computer; and 
 a two-arm monopole antenna resonating element mounted over the cavity to form a cavity-backed monopole antenna for the laptop computer, wherein the two arms are of unequal lengths. 
 
     
     
       15. The antenna defined in  claim 14  wherein a conductive metal laptop computer housing layer forms at least one surface of the cavity. 
     
     
       16. The antenna defined in  claim 15  wherein the antenna operates in a frequency range of about 2.4 GHz to 2.5 GHz, wherein the two-arm monopole antenna resonating element has a substrate to which circuitry is mounted, and wherein the laptop computer has a frame in which a recess is formed within which the substrate is mounted. 
     
     
       17. The antenna defined in  claim 14  wherein the two-arm monopole antenna resonating element is formed from conductive traces on a planar substrate having a planar upper surface and wherein the cavity has a planar surface opening in which the planar upper surface lies. 
     
     
       18. The antenna defined in  claim 17  wherein the cavity has a longitudinal axis and wherein at least one of the two arms runs parallel to the longitudinal axis. 
     
     
       19. The antenna defined in  claim 18  further comprising at least one printed label mounted to the planar upper surface, wherein the printed label has a height measured from the planar upper surface that is higher than the conductive traces.

Description:
BACKGROUND 
     This invention relates to wireless electronic devices, and more particularly, to antennas for wireless electronic devices such as portable electronic devices. 
     Antennas are used in conjunction with a variety of electronic devices. For example, computers use antennas to support wireless local area network communications. Antennas are also used for long-range wireless communications in cellular telephone networks. 
     It can be difficult to design antennas for modern electronic devices, particularly in electronic devices in which compact size and pleasing aesthetics are important. If an antenna is too small or is not designed properly, antenna performance may suffer. At the same time, an overly-bulky antenna or an antenna with an awkward shape may detract from the appearance of an electronic device or may make the device larger than desired. 
     It would therefore be desirable to be able to provide improved antennas for electronic devices such as portable electronic devices. 
     SUMMARY 
     Wireless portable electronic devices such as laptop computers are provided with cavity-backed monopole antennas. A wireless device may have a housing. The housing may have an upper housing portion and a lower housing portion. The upper housing portion may be a structure such as the cover of a laptop computer. The lower housing portion may be the base portion of a laptop computer. 
     The housing of the portable electronic device may have conductive structures. These conductive structures may include a metal layer that forms an outer surface for the upper housing and a frame within the upper housing to which a display is mounted. A conductive cavity may be formed from the conductive structures. The lower surface of the cavity may be formed from the metal layer that forms the outer surface for the upper housing. Sidewalls for the cavity may be formed from portions of the frame. 
     An antenna resonating elements structure may be mounted over the cavity to form a cavity-backed monopole antenna. The antenna resonating element structure may have two arms that run parallel to the longitudinal axis of the cavity. The arms may have unequal lengths to broaden the bandwidth of the antenna. 
     The antenna may operate in a frequency range of about 2.4 GHz to 2.5 GHz or other suitable frequency range. The cavity may have dimensions that are substantially less than a half of a wavelength at the antenna&#39;s desired operating frequency. 
     A cover glass in the upper housing may be used to protect the display. A bezel region may be formed around the periphery of the cover glass. The interior of the cover glass may be transparent to allow the display to be viewed. The bezel region may be provided with an underlayer of ink or other substance that renders the bezel region opaque. 
     When the cover glass is mounted to the upper housing portion, the bezel may overlap and cover the antenna resonating element and cavity and thereby block the antenna from view. 
     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 wireless electronic device such as a laptop computer that may be provided with antenna structures in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional end view of a portion of a wireless electronic device structure such as a laptop cover showing how an antenna with a cavity may be formed in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an illustrative antenna cavity that may make up part of a cavity antenna in a wireless electronic device in accordance with an embodiment of the present invention. 
         FIG. 4  is a top view of an illustrative antenna showing how a flex circuit may be used to form a connection to the antenna and additional electronic components such as camera components in accordance with an embodiment of the present invention. 
         FIG. 5  is a graph showing an illustrative communications band in which a cavity antenna in a wireless electronic device may be designed to operate in accordance with an embodiment of the present invention. 
         FIG. 6  is a graph showing how a cavity antenna with a single resonating element arm may have a frequency response that covers only a portion of a desired communications band in a wireless electronic device in accordance with an embodiment of the present invention. 
         FIG. 7  is a graph showing how a cavity antenna with multiple resonating element arms may have a frequency response that fully covers a communications band of interest in a wireless electronic device in accordance with an embodiment of the present invention. 
         FIG. 8  is a perspective view of a resonating element portion of a cavity antenna for a wireless electronic device in accordance with an embodiment of the present invention. 
         FIG. 9  is a perspective view of an illustrative cavity antenna formed in a portion of a portable computer cover in accordance with an embodiment of the present invention. 
         FIG. 10  is a longitudinal cross-sectional perspective view of a portion of the illustrative cavity antenna of  FIG. 9  in accordance with an embodiment of the present invention. 
         FIGS. 11 and 12  are each lateral cross-sectional perspective views of respective portions of the illustrative cavity antenna of  FIG. 9  in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to antennas for wireless electronic devices. The wireless electronic devices may, in general, be any suitable electronic devices. As an example, the wireless electronic devices may be desktop computers or other computer equipment. The wireless electronic devices may also be portable electronic devices such as laptop computers or small portable computers of the type that are sometimes referred to as ultraportables. Portable wireless electronic devices may also be somewhat smaller devices. Examples of smaller portable electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, other wearable and miniature devices, and handheld electronic devices. The portable electronic devices may be cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controls, global positioning system (GPS) devices, and handheld gaming devices. Devices such as these may be multifunctional. For example, a cellular telephone may be provided with media player functionality or a tablet personal computer may be provided with the functions of a remote control or GPS device. 
     Arrangements in which cavity antennas are incorporated into portable computers such as laptops are sometimes described herein as an example. This is, however, merely illustrative. Cavity antennas in accordance with embodiments of the present invention may be used in any wireless electronic devices. 
     An illustrative electronic device such as a portable electronic device in accordance with an embodiment of the present invention is shown in  FIG. 1 . Device  10  may be any suitable electronic device. As an example, device  10  may be a laptop computer. 
     As shown in  FIG. 1 , device  10  may have a housing  12 . Housing  12 , which is sometimes referred to as a case, may have an upper portion such as portion  16  and lower portion such as portion  14 . Upper housing portion  16  may sometimes be referred to as a cover or lid. Lower housing portion  14  may sometimes be referred to as a base. A hinge mechanism such as hinge  38  may be used to attach cover  16  to base  14 . Hinge  38  may allow cover  16  to rotate relative to base  14  about rotational axis  40 . If desired, other attachment mechanisms may be used such as a rotating and pivoting hinge for a tablet computer. Device  10  may also be implemented using a one-piece housing. In devices with two-piece housings, the hinge portion of the device may contain a spring-like clutch mechanism and may therefore sometimes be referred to as a clutch barrel. 
     Device  10  may have a display such as display  20 . Display  20  may be, for example, a liquid crystal display (LCD), an organic light emitting diode (OLED) display, or a plasma display (as examples). If desired, touch screen functionality may be incorporated into display  20 . The touch screen may be responsive to user input. 
     Device  10  may also have other input-output devices such as keypad  36 , touch pad  34 , and buttons such as button  32 . Input-output jacks and ports  30  may be used to provide an interface for accessories such as a microphone and headphones. A microphone and speakers may also be incorporated into housing  12 . 
     The edges of display  20  may be surrounded by a bezel  18 . Bezel  18  may be formed from a separate bezel structure such as a plastic ring or may be formed as an integral portion of a cover glass layer that protects display  20 . For example, bezel  18  may be implemented by forming an opaque black glass portion for display  20  or an associated cover glass piece. This type of arrangement may be used, for example, to provide upper housing  16  with an attractive uncluttered appearance. Illustrative configurations in which device  10  uses a glass bezel formed from the outer periphery of a sheet of display cover glass are sometimes described herein as an example. 
     When cover  16  is in a closed position, display  20  will generally lie flush with the upper surface of lower housing  14 . In this position, magnets on cover  16  may help hold cover  16  in place. Magnets may be located, for example, behind bezel portion  18  in regions  42 . 
     A camera such as camera  26  may also be mounted behind bezel region  18 . A window such as window  44  may be used to provide an opening for a lens in camera  26 . 
     Housing  12  may be formed from any suitable materials such as plastics, metals, glass, ceramic, carbon fiber, composites, combinations of plastic and metal, etc. To provide good durability and aesthetics, it is often desirable to use metal to form at least the exterior surface layer of housing  12 . Interior portions such as frames and other support members may be formed from plastic in areas where light weight and radio-frequency transparency are desired and may be formed from metal in areas where good structural strength is desirable. 
     Particularly in devices in which cover  16  and lower housing portion  14  are formed from metal, it can be challenging to properly locate antenna structures. Antenna structures that are blocked by conductive materials such as metal will not generally function properly. 
     In accordance with embodiments of the present invention, an antenna may be formed from a conductive cavity that is located behind bezel region  18 . An antenna with this type of configuration is shown in  FIG. 1  as antenna  22 . 
     In general, cavity antennas and other types of antennas may be located in any suitable portion of device  10 . For example, antennas may be located in the exterior surface of upper housing  16 , in the exterior surface of lower housing  14 , along the edges of housing  12 , on the interior surface of housing portion  14 , behind bezel  18 , etc. An advantage of forming antenna  22  behind bezel  18  in the location shown in  FIG. 1  is that this type of location allows incoming radio-frequency signals to reach antenna  22  without being impeded by conductive display or housing portions and allows radio-frequency signals to be freely transmitted from antenna  22 . If desired, other locations may be used for antenna  22 . Antenna  22  is located on the upper left portion of bezel  18  on cover  16  in the example of  FIG. 1 , but this is merely illustrative. 
     Device  10  may be provided with any suitable number of antennas. There may be, for example, one antenna (antenna  22 ), two antennas, three antennas, or more than three antennas, in device  10 . Each antenna may handle communications over a single communications band or multiple communications bands. 
     Device  10  may use antennas such as antenna  22  to handle communications over any communications bands of interest. For example, antennas and wireless communications circuitry in device  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 device  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 3G bands (e.g., the UMTS band at 1920-2170). 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 and local area network data communications can be handled using a multiband wireless local area network antenna. As another example, device  10  may have a single multiband antenna for handling communications in two or more data bands (e.g., at 2.4 GHz and at 5 GHz). 
     With one illustrative arrangement, which is sometimes described herein as an example, antenna  22  is configured to handle Bluetooth® signals at 2.4 GHz (as an example). One or more additional antennas may be provided in device  10  if desired. 
     Device  10  may have integrated circuits such as a microprocessor. Integrated circuits may also be included in device  10  for memory, input-output functions, etc. Circuitry in device  10  such as integrated circuits and other circuit components may be located in lower housing portion  14 . For example, a main logic board (sometimes referred to as a motherboard) may be used to mount some or all of this circuitry. The main logic board circuitry may be implemented using a single printed circuit board or multiple printed circuit boards. Printed circuit boards in device  10  may be formed from rigid printed circuit board materials or flexible printed circuit board materials. An example of a rigid printed circuit board material is fiberglass filled epoxy. An example of a flexible printed circuit board material is polyimide. Flexible printed circuit board structures may be used for mounting integrated circuits and other circuit components and may be used to form communications pathways in device  10 . Flexible printed circuit board structures such as these are sometimes referred to as “flex circuits.” 
     If desired, circuitry in device  10  may be located in cover  16 . For example, circuitry for supporting camera functions for camera  26  may be mounted on a camera module in the vicinity of camera  26 . Wireless communications circuitry for supporting operations with antenna  22  may be mounted on a radio-frequency module associated with antenna  22 . Modules such as these may be located behind bezel  18  (as an example). 
     As shown in  FIG. 1 , a communications path such as path  24  may be used to interconnect antenna  22  and camera  26  to circuitry  28  in lower housing portion  14 . Path  24  may be implemented, for example, using a flex circuit that is connected to a radio-frequency antenna module associated with antenna  22  and to a camera module associated with camera  26 . Circuitry  28  may include wireless communications circuitry and other processing circuitry. This circuitry may be associated with a main logic board (motherboard) in lower housing  14  (as an example). Analog radio-frequency antenna signals and/or digital data associated with antenna  22  may be conveyed over path  24 . An advantage to locating radio-frequency circuitry in the immediate vicinity of antenna  22  is that this allows data to be conveyed between the motherboard in housing portion  14  and antenna  22  digitally without incurring radio-frequency transmission line losses. 
     A cross-sectional side view of an illustrative arrangement for antenna  22  when antenna  22  is formed in upper housing portion  16  is shown in  FIG. 2 . As shown in  FIG. 2 , antenna  22  may be formed from a conductive cavity  48  and antenna resonating element structure  50 . These structures may be located under bezel portion  18  of display structures  20 . Display structures  20  may include LCD display  54  and cover glass  52 . The portion of cover glass  52  in region  18  may have an undercoat of an opaque ink such as a black ink, preventing antenna  22  from being viewed by a user of device  10 . The opaque ink in region  18  may be provided in a layer that is sufficiently thin to ensure that the ink layer is transparent to radio-frequency signals. Because glass  52  is a dielectric and because the opaque ink is sufficiently thin, radio-frequency signals for antenna  22  are not blocked by glass  52  or the ink in bezel region  18 . 
     Cavity  48  in antenna  22  may be formed from a metal frame structure such as an aluminum frame structure associated with upper housing portion  16  or any other suitable conductive structures. The frame structure may, as an example, be mounted to an interior portion of exterior housing layer  46 . Housing layer  46  may be, for example, a thin metal sheet that makes up the exterior portion of upper housing portion  16 . 
     Antenna resonating element structure  50  in antenna  22  may be formed from printed metal foil structures, wires, conductive traces on a rigid printed circuit board, conductive traces on a flex circuit, combinations of these arrangements, or other suitable arrangements. With one particularly suitable configuration, which is sometimes described herein as an example, antenna resonating element portion  50  of antenna  22  may be formed from conductive traces on a printed circuit board substrate. The conductive resonating element traces may be, for example, traces of copper, gold, other metals, etc. 
     During operation of antenna  22 , radio-frequency signals may be transmitted out of cavity  48  as shown by arrows  53  and may be received by antenna  22  as shown by arrows  55 . Wireless signals are therefore directed outwards away from housing portion  46 . 
     A perspective view of an illustrative cavity  48  for antenna  44  is shown in  FIG. 3 . In the  FIG. 3  example, cavity  48  has conductive walls  56  that are formed from a metal frame structure (frame  62 ). Raised central portion  58  may be provided with a threaded screw hole such as hole  60 . A screw may be screwed into hole  60  to hold antenna resonating element structure  50  ( FIG. 2 ) in place. If desired, multiple screw holes or other attachment mechanisms may be used to attach antenna resonating element structure  50  to cavity  48  (e.g., rivets, adhesive, springs, etc.). 
     Cavity  48  may have any suitable shape. In the arrangement of  FIG. 3 , cavity  48  has a rectangular surface opening and forms a prism-shaped cavity within frame  62 . Other shapes may be used if desired (e.g., other polyhedral shapes, cylinders, cones, shapes with both curved and flat sidewalls, irregular openings, etc. When a prism-shaped cavity of the type shown in  FIG. 3  is used, cavity  48  may be characterized by a length L and a width W. Length L may be larger than width W. Longitudinal axis  64  may be aligned with the longer (longitudinal) dimension of cavity  48 . When in operation handling radio-frequency signals, the electric field of the radio-frequency signals may primarily be oriented as shown by E-field arrow  66  (i.e., with the electric field component of the radio-frequency signals perpendicular to longitudinal axis  64 ). 
     It may be desirable to implement antenna  22  using a cavity with compact dimensions. Efficiency may be maximized when cavity dimensions are about one half of a wavelength at a frequency of interest. At 2.4 GHz, this dimension is about 60 mm. If desired, antenna cavity  48  may be formed with more compact dimensions (e.g., dimensions less than 10 mm, about 6 mm, or other suitable dimensions less than a half wavelength in size). Despite the use of these smaller dimensions, antenna performance has been demonstrated to be satisfactory for a variety of applications (e.g., for Bluetooth® signal transmission and reception). In general, any suitable dimensions, polarization orientation, and cavity geometry may be used for cavity  48 . The configuration of  FIG. 3  is merely an example. 
     As described in connection with  FIG. 1 , a communications path such as communications path  24  may be used to interconnect antenna  22  and camera module  26  with circuitry  28  in lower housing portion  14  of device  10 . Communications path  24  may, for example, be formed at least partly from a flex circuit. A top view of antenna  22  and camera  26  is shown in  FIG. 4 . As shown in  FIG. 4 , path  24  may be formed from flex circuit portion  24 A and cable portion  24 B. Antenna  22  may be formed as part of an antenna module that has an associated connector  68  such as a zero insertion force (ZIF) connector to which flex circuit  24 A is connected. Camera  26  may have associated components  26 A and  26 B such as integrated circuits, a camera unit, etc. Components  26 A and  26 B may be mounted on flex circuit  24 A. Cable portion  24 B may be electrically connected to flex circuit portion  26 A to form path  24  or flex circuit portion  26 A may be extended to reach circuitry  28  ( FIG. 1 ). 
     Cavity antenna  22  may be configured to have a sufficiently wide bandwidth to cover a desired communications band. Consider, as an example, the graph of  FIG. 5 , which shows desired frequency coverage for a Bluetooth® antenna. In the graph of  FIG. 5  and the related graphs of  FIGS. 6 and 7 , antenna voltage standing wave ratio (VSWR) values are plotted as a function of signal frequency. As shown in  FIG. 5 , when used for Bluetooth® applications, antenna  22  preferably covers frequencies in the range of about 2.4 GHz to about 2.5 GHz. 
     The presence of a conductive cavity in an antenna such as cavity  48  in antenna  22  tends to narrow the frequency response of the antenna. If care is not taken and the antenna resonating elements in antenna  22  are not designed to support a sufficiently large antenna bandwidth, the overall frequency response of a cavity-backed antenna may too narrow. In the  FIG. 6  example, a single antenna resonating element arm is being used in antenna resonating element portion  50  of antenna  22 . As a result, the bandwidth of the antenna in the  FIG. 6  example is characterized by the relatively narrow bandwidth of curve  70 . This frequency response may be acceptable in some circumstances, but is not sufficiently wide to cover the entire communications band of interest in  FIG. 5 . 
     To extend the frequency coverage of antenna  22  sufficiently to cover the desired communications band of  FIG. 5 , antenna  22  may be provided with two or more antenna resonating element arms. As shown in  FIG. 7 , a first arm in this type of configuration may give rise to a first frequency response curve (curve  70 ) and a second arm may give rise to a second frequency response curve (curve  72 ). To ensure that the peak associated with curve  72  is slightly higher in frequency than the peak associated with curve  70 , the second arm in antenna resonating element  50  may be constructed to be slightly shorter than the first antenna resonating arm. 
     As shown by curve  74  of  FIG. 7 , when a two-arm antenna resonating element of this type is used, the resulting overall frequency response of antenna  22  will be sufficient to cover the entire desired communications band of  FIG. 5 . The use of an antenna resonating element with multiple arms or other features that tend to broaden the bandwidth of antenna  22  can therefore help to overcome bandwidth-narrowing characteristics of the type that are sometimes associated with using cavities such as cavity  48 . If desired, additional arms may be used in antenna resonating element structure  50 . The use of a two-arm arrangement for antenna resonating element structure  50  is illustrative. Antenna resonating element structure  50  may have any suitable number of resonating element portions (e.g., arms) and any suitable trace geometry. 
     An illustrative antenna resonating element structure that may be used in antenna  22  is shown in  FIG. 8 . As shown in  FIG. 8 , antenna resonating element structure  50  may have a first antenna resonating element arm such as arm  78  and a second antenna resonating element arm such as arm  76 . Arm  78  may have a longer length than arm  76 . In this type of configuration, arm  78  may be associated with a lower frequency response (e.g., curve  70  of the graph of  FIG. 7 ) and arm  76  may be associated with a higher frequency response (e.g., curve  72  of the graph of  FIG. 7 ). 
     If there is sufficient space available in device  10 , arms such as arms  76  and  78  may both be constructed using straight traces (i.e., traces that have the elongated straight shape of trace  76  in the  FIG. 8  example). In situations in which less area is available, one or both of arms  76  and  78  may be provided with bends. Bends may be used, for example, to fold an antenna arm back on itself. In the  FIG. 8  example, arm  78  has a series of bends that form indentations  80 . Arm  78  therefore follows a meandering path. The meandering path that is used for arm  78  lengthens arm  78  relative to arm  76  without extending the length of arm  78  along axis  64  past that of arm  76 . 
     Arms  76  and  78  may be formed on a flexible printed circuit substrate or a rigid printed circuit board substrate such as substrate  82 . If desired, integrated circuits and other circuitry may be mounted on substrate  82  to form an antenna module. As shown in  FIG. 8 , for example, radio-frequency integrated circuit  84  (e.g., a transceiver circuit) may be mounted to the underside of substrate  82 . Vias or other conductive structures may be used to electrically interconnect circuitry  84  with traces  76  and  78 . Traces  76  and  78  may be formed on the uppermost surface of substrate  82  as shown in  FIG. 8  or may be formed in an interior layer or backside layer of substrate  82 . 
     As shown in  FIG. 8 , trace  88  may be formed from an extended portion of arm  78 . Antenna trace  86 , which runs parallel to trace  88  in region  90  may be formed in a different layer of substrate  82  than trace  88 . For example, trace portion  88  may be formed on the uppermost surface of substrate  82 , whereas trace  86  may be formed on a lower layer of substrate  82 . Substrate  82  may be, for example, a multi-layer printed circuit board. 
     In region  90 , trace  86  and conductive portion  88  of arm  78  form a transmission line that conveys signals from circuit  84  to arms  76  and  78 . At point  92 , trace  88  may bend towards arm  76 . Trace portion  88  of arm  78  in region  90  may serve as a localized ground feed terminal. At point  94 , trace  86  may be interconnected to arm  76  to serve as a positive antenna feed terminal. 
     Arms such as arms  76  and  78  may be considered to form a two-arm monopole antenna architecture for antenna  22 . Cavity  48  serves as a cavity portion of antenna  22 . Antenna  22  may therefore sometimes be referred to as a cavity-backed monopole. The opposing conductive portions of arms  76  and  78  form slot  98 . Interaction between conductive walls  56  of cavity  48  and the monopole resonating element structures contribute an inductive impedance component to the input impedance for antenna  22 . This tends to make the optimum feed location for antenna  22  close to end  100  of slot  98 . If desired, other suitable feed arrangements may be used for feeding antenna  22 . The arrangement of  FIG. 8  in which traces in substrate  82  such as trace  86  and conductive arm portion  88  are used to convey signals between circuit  84  and antenna resonating element arms  76  and  78  is merely illustrative. 
     As shown in  FIG. 8 , substrate  82  of resonating element structure  50  may have a hole such as hole  102 . When mounting resonating element structure  50  into cavity  48  of antenna  22 , a screw may be inserted through hole  102  and into associated threaded screw hole  60  in cavity  48  ( FIG. 3 ). When inserted in this way, the screw may electrically connect with antenna traces in the vicinity of hole  102 , thereby grounding the antenna to portion  58  of cavity  48  ( FIG. 3 ) and shorting portion  58  to frame  62 . 
     A perspective view of an illustrative embodiment of antenna  22  formed by mounting antenna resonating element structure  50  in cavity  48  is shown in  FIG. 9 . As shown in  FIG. 9 , antenna resonating element structure  50  may have a shorter antenna resonating element arm such as arm  76  and a longer antenna resonating element arm such as meandering arm  78 . Because arms  76  and  78  form a two arm monopole antenna, antenna  22  may be referred to as cavity-backed monopole antenna. Arms  76  and  78  form monopole antenna resonating elements that are aligned with longitudinal axis  64  of cavity  48 . Each arm has a longitudinal axis that runs parallel to axis  64 . 
     Arms  76  and  78  run parallel to each other and form a slot (slot  98  of  FIG. 8 ). Arms  76  and  78  may be fed across this slot (e.g., using feeds such as feeds  94  and  96 , as described in connection with  FIG. 8 ). Substrate  82  has planar upper and lower surfaces. The traces on substrate  82  such as the traces of arms  76  and  78  therefore lie in the plane formed by the surface opening of cavity  48 . During operation, radio-frequency signals tend to be polarized so that the electric field of the signals is oriented as shown by E-field vector  66 , perpendicular to longitudinal axis  64  of cavity  48  and antenna  22 . The dimensions of cavity  48  (length, width, and depth) may each be substantially less than a half of a wavelength at the operating frequencies for antenna  22  (e.g., one half of a half wavelength or less, one quarter of a half wavelength or less, one fifth of a half wavelength or less, etc.). 
     Screw  106  may be used to screw substrate  82  to a threaded hole in frame  62  (hole  102  of  FIG. 8 ). Frame  62  may be, for example, a frame that is used to form a structural support for display  20  ( FIG. 1 ) in upper housing portion  16 . Frame  62  may be formed from aluminum or other suitable conductive materials. Because frame  62  is formed from a conductor, the walls of cavity  48  are conductive. Housing structure  46  may be, for example, a thin layer of metal that forms the outer surface layer of cover  16 . Frame  62  may be mounted to the inside surface of metal layer  46  using welds, adhesive, fasteners, or other suitable attachment mechanisms. 
     Gasket  104  may be interposed between frame  62  and edge  114  of housing layer  46 . Gasket  104  can be formed from a soft elastomeric material that helps prevent cover glass  52  ( FIG. 2 ) from becoming damaged by direct contact with edge  114 . Region  112  in frame  62  can be recessed and can include a flex circuit communications path such as flex circuit portion  24 A of  FIG. 4 . 
     Substrate  82  forms a support structure for traces  76  and  78 . Substrate  82  may have tabs  116  or other lateral protrusions that help align substrate  82  with cavity  48 . Spacers such as spacers  110  and  108  may be formed on the upper surface of substrate  82 . Spacers  110  and  108  may be formed from plastic film (tape) or any other suitable flexible layer. Spacers  110  and  108  may have a height measured from the planar upper surface of substrate  82  that is higher than the height of conductive traces  76  and  78 . When cover glass  52  is mounted to upper housing  16 , spacers  108  and  110  prevent the inner surface of glass  52  from bearing directly against surface features in substrate  82  such as antenna resonating element traces  76  and  78 . Spacers  108  and  110  therefore protect antenna  22  from damage by bezel region  18  of cover glass  52 . If desired, graphics and text may be may be printed on spacer  108  to serve as a label. 
     A cross-sectional view of antenna  22  of  FIG. 9  is shown in  FIG. 10 . As shown in  FIG. 10 , cavity  48  may have a lower face  118  (sometimes referred to as a lower wall or bottom surface) that is formed from the flat inner surface of metal layer  46 . Cavity sidewalls  56  are shown as being formed from the inwardly facing portions of frame  62 . If desired, cavity  48  may be formed using other conductive structures. For example, a metal insert may be used to form cavity  48  or the sidewalls and bottom surface of cavity  48  may be formed using other conductive structures in device  10 . 
     As described in connection with  FIG. 8 , circuitry  84  may be mounted to the lower portion of substrate  82 . Circuitry  84  may be electromagnetically shielded by metal can  124 . Frame  64  may be recessed to accommodate can  124  and the circuitry  84  that is mounted within can  124 . Circuitry  84  may include a radio-frequency transceiver integrated circuit such as radio  120 , other transceiver components such as components  122 , and other discrete and integrated circuit devices. These circuit components may be mounted on sub-board  126 . Sub-board  126  may be a printed circuit board that is mounted to the underside of substrate  82 . Zero insertion force connector  68  may also be mounted to the underside of substrate  82  and may be used to form a connection between circuitry  84  and flex circuit communications path  24 A. 
     A cross-sectional perspective view of the antenna assembly of  FIG. 10  taken along line  134  of  FIG. 10  is shown in  FIG. 11 . As shown in  FIG. 11 , adhesive  126  such as double-sided adhesive tape may be used to help attach frame  62  and gasket  104  to metal layer  46  of cover  16 . 
       FIG. 11  also shows how substrate  82  may have an opening in region  128  to accommodate components  130 . Components  130  may be mounted on printed circuit board  126 . By forming opening  128 , board  126  may be mounted with its upper surface flush with the lower surface of substrate  82 . In this configuration, circuit components  130  protrude upwardly in direction  132  into the interior of hole  128 . This arrangement allows circuitry  84  to be compactly mounted in antenna  22  (i.e., in the assembly formed by antenna  22 ). 
     A similar cross-sectional perspective view of antenna  22 , but taken along line  136  of  FIG. 10  is shown in  FIG. 12 . As shown in  FIG. 12 , screw  106  may be screwed into threaded screw hole  102  to help attach antenna resonating element structure  50  to frame  62 . This may be accomplished by attaching a washer such as washer  138  to the underside of substrate  82  and by pressing washer  138  against frame  62  by tightening screw  106 . Conductive traces (e.g., a conductive trace on the underside of substrate  82 ) may be used to form a ground path between screw  106  and the antenna ground of antenna resonating element  50 . If desired, a washer may be provided on the upper surface of substrate  82 . Frame  62  may be electrically connected to metal layer  46 , thereby grounding frame  62  to metal layer  46 . 
     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: 20080925
Publication Date: 20120508
Grant Date: 20120508
Priority Date: 20080925
Inventors: AYALA VAZQUEZ ENRIQUE
XU HAO
SPRINGER GREGORY A.
CHIANG BING
CAMACHO EDUARDO LOPEZ
KOUGH DOUGLAS B.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q5/371", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 42037101