PATENT DOCUMENT

Publication Number: US-8373610-B2
Application Number: US-95898807-A
Country: US
Kind Code: B2

Title: Microslot antennas for electronic devices

Abstract:
Microslot antennas may be provided for electronic devices such as portable electronic devices. The microslot antennas may have dielectric-filled microslots that are formed in a ground plane element. The ground plane element may be formed from part of a conductive device housing. The microslots may be narrow enough that they are not readily noticeable to the naked eye. The microslots may have lengths that allow the microslot antenna to provide antenna coverage in one or more communications bands. A first group of the microslots may be used to provide coverage in a first communications band and a second group of the microslots may be used to provide coverage in a second communications band.

Claims:
1. An antenna comprising:
 a ground plane element having portions comprising at least first and second dielectric-filled slots that serve as resonating elements for the antenna and that each have a width of less than 100 microns, wherein the at least first and second dielectric-filled slots are formed in a surface of the ground plane element and wherein the widths of the at least first and second dielectric-filled slots are dimensions of the at least first and second dielectric-filled slots that are coplanar with the surface of the ground plane element; 
 a ground terminal located between the at least first and second dielectric-filled slots and coupled to a ground conductor in a transmission line; and 
 first and second antenna feed terminals coupled to a common signal conductor in the transmission line, wherein the first dielectric-filled slot is between the ground terminal and the first antenna feed terminal and wherein the second dielectric-filled slot is between the ground terminal and the second antenna feed terminal. 
 
     
     
       2. The antenna defined in  claim 1  wherein the ground plane element portions are configured so that at least one of the at least first and second dielectric-filled slots has an open end. 
     
     
       3. The antenna defined in  claim 1  wherein the at least first and second dielectric-filled slots form first and second groups of slots, wherein the first group of slots includes the first slot and covers a first communications band, and wherein the second group of slots includes the second slot and covers a second communications band. 
     
     
       4. The antenna defined in  claim 1  wherein the at least first and second dielectric-filled slots form first and second groups of slots, wherein the first group of slots includes the first slot and covers a first communications band at 2.4 GHz, and wherein the second group of slots includes the second slot and covers a second communications band at 5.0 GHz. 
     
     
       5. The antenna defined in  claim 1  wherein the at least first and second dielectric-filled slots form first and second groups of slots, wherein the first group of slots covers a first communications band at 2.4 GHz and contains at least the first slot and a third slot, and wherein the second group of slots covers a second communications band at 5.0 GHz and contains at least the second slot and a fourth slot. 
     
     
       6. The antenna defined in  claim 5  wherein the first slot has a first length, the second slot has a second length, the third slot has a third length, and the fourth slot has a fourth lengths and wherein each of the first, second, third, and fourth lengths is unique. 
     
     
       7. The antenna defined in  claim 1  wherein the at least first and second dielectric-filled slots form first and second groups of slots, wherein the first group of slots covers a first communications band at 2.4 GHz and contains at least the first slot and a third slot, wherein the second group of slots covers a second communications band at a second frequency and contains more than the second slot and a fourth slot, and wherein the second communications frequency is larger than the first communications frequency. 
     
     
       8. The antenna defined in  claim 1  wherein each of the at least first and second dielectric-filled slots has a width that is less than 30 microns and wherein the at least first and second dielectric-filled slots each have a length of at least 10 mm. 
     
     
       9. An electronic device comprising:
 transceiver circuitry; 
 a transmission line coupled to the transceiver circuitry; 
 a conductive case in which the transceiver circuitry and the transmission line are housed, wherein the conductive case has at least one dielectric-filled opening; 
 an antenna having a ground plane element formed from the conductive case and antenna resonating element formed from the at least dielectric-filled opening, wherein the at least opening comprises a microslot having a width of less than 100 microns, wherein the microslot formed in a surface of the conductive case, wherein the width of the microslot dimension of the microslot that coplanar with the surface of the conductive case, wherein the microslot comprises a first microslot, and wherein the antenna comprises a second microslot; 
 a ground terminal located between the first and second microslots and coupled to a ground conductor in the transmission line; and 
 first and second antenna feed terminals coupled to a common signal conductor in the transmission line, wherein the first microslot is between the ground terminal and the first antenna feed terminal and wherein the second microslot is between the ground terminal and the second antenna feed terminal. 
 
     
     
       10. The electronic device defined in  claim 9  further comprising epoxy that fills the dielectric-filled opening. 
     
     
       11. The electronic device defined in  claim 9  wherein the electronic device comprises a portable electronic device, wherein the conductive case comprises a metal case, and wherein the antenna comprises a plurality of microslots formed in the conductive case. 
     
     
       12. The electronic device defined in  claim 9  wherein the electronic device comprises a portable computer, wherein the conductive case comprises a conductive computer housing for the portable computer, wherein the antenna comprises a plurality of microslots formed in the conductive computer housing, and wherein each microslot has a width of less than 100 microns and a length of at least 10 mm. 
     
     
       13. The electronic device defined in  claim 9  wherein the antenna comprises a plurality of microslots formed in the conductive case, and wherein each microslot has a width of less than 30 microns. 
     
     
       14. The electronic device defined in  claim 9  wherein the electronic device comprises a portable electronic device, wherein the conductive case comprises a conductive housing for the portable electronic device, wherein the antenna comprises a plurality of microslots formed from openings in the conductive housing, wherein each microslot has a width of less than 100 microns and a length of at least 10 mm, wherein a first group of the microslots is configured to provide coverage for the antenna in a first communications band and wherein a second group of the microslots is configured to provide coverage for the antenna in a second communications band, wherein the first and second communications bands have respective center frequencies, wherein the center frequency of the second communications band is higher than the center frequency of the first communications band, and wherein each of the microslots in the second group has a length that is less than each of the microslots in the first group. 
     
     
       15. A portable electronic device antenna comprising:
 a ground plane element formed from a conductive housing for the portable electronic device; and 
 a plurality of microslots formed in the ground plane element, wherein each of the microslots has a width of less than 100 microns, wherein each of the microslots is formed in a surface of the ground plane element, wherein the width of each of the microslots is a dimension of that microslot that is coplanar with the surface of the ground plane element, wherein each microslot in the plurality of microslots has a length that is different from the lengths of all of the other microslots in the plurality of microslots, wherein a first plurality of the microslots are configured to provide antenna coverage in a first communications band, and wherein a second plurality of the microslots are configured to provide antenna coverage in a second communications band; and 
 a ground terminal located between the first and second pluralities of microslots and coupled to a ground conductor in a transmission line; and 
 first and second antenna feed terminals coupled to a common signal conductor in the transmission line, wherein the first plurality of microslots is between the ground terminal and the first antenna feed terminal and wherein the second plurality of microslots is between the ground terminal and the second antenna feed terminal. 
 
     
     
       16. The portable electronic device antenna defined in  claim 15  wherein the first plurality of the microslots are configured to provide antenna coverage in a 2.4 GHz communications band and wherein the second plurality of the microslots are configured to provide antenna coverage in a 5.0 GHz communications band. 
     
     
       17. The portable electronic device antenna defined in  claim 16  wherein the first plurality of microslots includes at least two microslots and wherein the second plurality of microslots includes at least four microslots. 
     
     
       18. The portable electronic device antenna defined in  claim 15  wherein the first plurality of the microslots comprises first and second microslots, wherein the second plurality of the microslots comprises third and fourth microslots, wherein the first microslot is configured to provide antenna coverage in a first communications sub-band within the first communications band, wherein the second microslot is configured to provide antenna coverage in a second communications sub-band within the first communications band, wherein the third microslot is configured to provide antenna coverage in a third communications sub-band within the second communications band, and wherein the second microslot is configured to provide antenna coverage in a fourth communications sub-band within the second communications band.

Description:
BACKGROUND 
     This invention relates to antennas, and more particularly, to antennas for electronic devices such as portable electronic devices. 
     Due in part to their mobile nature, portable electronic devices are often provided with wireless communications capabilities. Portable electronic devices may use wireless communications to communicate with wireless base stations. For example, cellular telephones may 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). Portable electronic devices may also use other types of communications links. For example, portable electronic devices may communicate using the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz and the Bluetooth® band at 2.4 GHz. Communications are also possible in data service bands such as the 3G data communications band at 2100 MHz band (commonly referred to as UMTS or Universal Mobile Telecommunications System). 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to reduce the size of components that are used in these devices. For example, manufacturers have made attempts to miniaturize the antennas used in portable electronic devices. 
     A typical antenna may be fabricated by patterning a metal layer on a circuit board substrate or may be formed from a sheet of thin metal using a foil stamping process. These techniques can be used to produce antennas that fit within the tight confines of a compact portable device such as a handheld electronic device. With conventional portable electronic devices, however, design compromises are made to accommodate compact antennas. These design compromises may include, for example, compromises related to antenna efficiency and antenna bandwidth. 
     It would therefore be desirable to be able to provide improved antennas for electronic devices such as portable electronic devices. 
     SUMMARY 
     Microslot antennas may be provided for electronic devices such as portable electronic devices. The microslot antennas may have dielectric-filled openings that are formed in a ground plane element. The dielectric-filled openings may be filled with air, plastic, epoxy, or other dielectrics. 
     The dielectric-filled openings may form microslots having relatively narrow widths. As an example, microslots may be used for the microslot antennas that have widths that are so narrow that the microslots are invisible to the naked eye. 
     The ground plane element may be formed from a conductor on a printed circuit board or other suitable conductive structure. With one suitable arrangement, the ground plane element may be formed from a conductive housing for an electronic device. 
     The electronic device may be a portable electronic device such as a portable computer or a handheld electronic device. By forming the microslots of the microslot antenna within the housing of the device, the need for potentially unsightly dielectric antenna covers and external antenna arrangements can be eliminated. 
     The microslots may have lengths that allow a microslot antenna to provide antenna coverage in one or more communications bands. In a dual-band configuration, a first group of the microslots may be used to provide coverage in a first communications band and a second group of the microslots may be used to provide coverage in a second communications band. 
     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 electronic device in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative electronic device in accordance with an embodiment of the present invention. 
         FIG. 3  is a top view of an illustrative microslot antenna in accordance with an embodiment of the present invention. 
         FIG. 4  is a graph showing the performance of an illustrative dual-band microslot antenna in which multiple microslots of similar length have been used to broaden coverage bandwidth in each of the two bands in accordance with an embodiment of the present invention. 
         FIG. 5  is a top view of an alternative feed arrangement that may be used for a microslot antenna in accordance with an embodiment of the present invention. 
         FIG. 6  is a graph showing how coupling efficiency may vary as a function of microslot position in a microslot antenna having an antenna feed arrangement of the type shown in  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 7  is a graph showing how coupling efficiently may vary as a function of microslot position in a microslot antenna having an antenna feed arrangement of the type shown in  FIG. 5  in accordance with an embodiment of the present invention. 
         FIG. 8  is a top view of an illustrative microslot antenna having three microslots that are aligned along one end of the microslots in accordance with an embodiment of the present invention. 
         FIG. 9  is a top view of an illustrative microslot antenna having open ends in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to electronic devices, and more particularly, to antennas for wireless electronic devices. 
     The wireless electronic devices may 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 electronic devices may also be somewhat smaller devices. Examples of smaller portable electronic devices 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. 
     Examples of portable and handheld electronic devices include 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. The devices may also be hybrid devices that combine the functionality of multiple conventional devices. Examples of hybrid devices include a cellular telephone that includes media player functionality, a gaming device that includes a wireless communications capability, a cellular telephone that includes game and email functions, and a handheld device that receives email, supports mobile telephone calls, has music player functionality and supports web browsing. These are merely illustrative examples. 
     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. 
     Device  10  may handle communications over one or more communications bands. For example, 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 5.0 GHz band that is sometimes used for Wi-Fi communications, the 1575 MHz Global Positioning System band, and 3G data bands (e.g., the UMTS band at 1920-2170). These bands may be covered by using single 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 5.0 GHz). 
     Device  10  may have housing  12 . Housing  12 , which is sometimes referred to as a case, may be formed of any suitable materials including plastic, glass, ceramics, metal, other suitable materials, or a combination of these materials. In some situations, housing  12  or 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 . 
     Housing  12  or portions of housing  12  may also be formed from conductive materials such as metal. An illustrative metal housing material that may be used is anodized aluminum. Aluminum is relatively light in weight and, when anodized, has an attractive insulating and scratch-resistant surface. If desired, other metals can be used for the housing of device  10 , such as stainless steel, magnesium, titanium, alloys of these metals and other metals, etc. In scenarios in which housing  12  is formed from metal elements, one or more of the metal elements may be used as part of the antenna in device  10 . For example, metal portions of housing  12  and metal components in housing  12  may be shorted together to form a ground plane in device  10  or to expand a ground plane structure that is formed from a planar circuit structure such as a printed circuit board structure (e.g., a printed circuit board structure used in forming antenna structures for device  10 ). 
     Device  10  may have one or more buttons such as buttons  14 . Buttons  14  may be formed on any suitable surface of device  10 . In the example of  FIG. 1 , buttons  14  have been formed on the top surface of device  10 . Buttons  14  may form a keyboard on a laptop computer (as an example). 
     If desired, device  10  may have a display such as display  16 . Display  16  may be a liquid crystal diode (LCD) display, an organic light emitting diode (OLED) display, a plasma display, or any other suitable display. The outermost surface of display  16  may be formed from one or more plastic or glass layers. If desired, touch screen functionality may be integrated into display  16 . Device  10  may also have a separate touch pad device such as touch pad  26 . An advantage of integrating a touch screen into display  16  to make display  16  touch sensitive is that this type of arrangement can save space and reduce visual clutter. Buttons  14  may, if desired, be arranged adjacent to display  16 . With this type of arrangement, the buttons may be aligned with on-screen options that are presented on display  16 . A user may press a desired button to select a corresponding one of the displayed options. 
     Device  10  may have circuitry  18 . Circuitry  18  may include storage, processing circuitry, and input-output components. Wireless transceiver circuitry in circuitry  18  may be used to transmit and receive radio-frequency (RF) signals. Transmission lines such as coaxial transmission lines and microstrip transmission lines may be used to convey radio-frequency signals between transceiver circuitry and antenna structures in device  10 . As shown in  FIG. 1 , for example, transmission line  22  may be used to convey signals between antenna structure  20  and circuitry  18 . Transmission line  22  may be, for example, a coaxial cable that is connected between an RF transceiver (sometimes called a radio) and a multiband antenna. Antenna structures such as antenna structure  20  may be located adjacent to keys  14  as shown in  FIG. 1  or in other suitable locations (e.g., on top surface  24  of housing  12 ). 
     A schematic diagram of an embodiment of an illustrative electronic device such as a portable electronic device is shown in  FIG. 2 . Portable device  10  may be a notebook 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 combination of such devices, or any other suitable portable or handheld electronic device. 
     As shown in  FIG. 2 , portable device  10  may include storage  34 . Storage  34  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., battery-based static or dynamic random-access-memory), etc. 
     Processing circuitry  36  may be used to control the operation of device  10 . Processing circuitry  36  may be based on a processor such as a microprocessor and other suitable integrated circuits. With one suitable arrangement, processing circuitry  36  and storage  34  are 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. Processing circuitry  36  and storage  34  may be used in implementing suitable communications protocols. Communications protocols that may be implemented using processing circuitry  36  and storage  34  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, protocols for handling 3G data services such as UMTS, cellular telephone communications protocols, etc. 
     Input-output devices  38  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. Display screen  16 , keys  14 , and touchpad  26  of  FIG. 1  are examples of input-output devices  38 . 
     Input-output devices  38  may include user input-output devices  40  such as buttons, touch screens, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, speakers, tone generators, vibrating elements, etc. A user can control the operation of device  10  by supplying commands through user input devices  40 . 
     Display and audio devices  42  may include liquid-crystal display (LCD) screens or other screens, light-emitting diodes (LEDs), and other components that present visual information and status data. Display and audio devices  42  may also include audio equipment such as speakers and other devices for creating sound. Display and audio devices  42  may contain audio-video interface equipment such as jacks and other connectors for external headphones and monitors. 
     Wireless communications devices  44  may include communications circuitry such as radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, passive RF components, one or more antennas (e.g., antenna structures such as antenna structures  20  of  FIG. 1 ), and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Device  10  can communicate with external devices such as accessories  46  and computing equipment  48 , as shown by paths  50 . Paths  50  may include wired and wireless paths. Accessories  46  may include headphones (e.g., a wireless cellular headset or audio headphones) and audio-video equipment (e.g., wireless speakers, a game controller, or other equipment that receives and plays audio and video content). 
     Computing equipment  48  may be any suitable computer. With one suitable arrangement, computing equipment  48  is a computer that has an associated wireless access point or an internal or external wireless card that establishes a wireless connection with device  10 . The computer may be a server (e.g., an internet server), a local area network computer with or without internet access, a user&#39;s own personal computer, a peer device (e.g., another portable electronic device  10 ), or any other suitable computing equipment. 
     The antenna structures and wireless communications devices of device  10  may support communications over any suitable wireless communications bands. For example, wireless communications devices  44  may be used to cover communications frequency bands such as the cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz, data service bands such as the 3G data communications band at 2100 MHz band (commonly referred to as UMTS or Universal Mobile Telecommunications System), Wi-Fi® (IEEE 802.11) bands (also sometimes referred to as wireless local area network or WLAN bands), the Bluetooth® band at 2.4 GHz, and the global positioning system (GPS) band at 1575 MHz. Wi-Fi bands that may be supported include the 2.4 GHz band and the 5.0 GHz bands. The 2.4 GHz Wi-Fi band extends from 2.412 to 2.484 GHz. Commonly-used channels in the 5.0 GHz Wi-Fi band extend from 5.15-5.85 GHz, so the 5.0 GHz band is sometimes referred to by the 5.4 GHz approximate center frequency for this range (i.e., these communications frequencies are sometimes referred to as making up a 5.4 GHz communications band). Device  10  can cover these communications bands and/or other suitable communications bands with proper configuration of the antenna structures in wireless communications circuitry  44 . 
     A top view of illustrative antenna structures in accordance with an embodiment of the present invention is shown in  FIG. 3 . As shown in  FIG. 3 , antenna  20  may be formed from a ground plane structure such as ground plane  52 . Antenna resonating elements for antenna  20  may be formed from openings in ground plane such as openings  54  and  56 . These openings, which are sometimes referred to as slots or microslots, may be filled with air or other suitable dielectrics such as plastic or epoxy. Microslots  54  and  56  may be substantially rectangular in shape and may have narrower dimensions (i.e., widths measured parallel to lateral dimension  58 ) and longer dimensions (e.g., lengths measured parallel to longitudinal dimension  60 ). If desired, microslots  54  and  56  may also have non-rectangular shapes (e.g., shapes with non-perpendicular edges, shapes with curved edges, shapes with bends, etc.). The use of rectangular microslot configurations is generally described herein as an example. 
     The widths of microslots  54  and  56  are generally much less than their lengths. For example, the widths of microslots  54  and  56  may be 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 microslots  54  and  56  may be on the order of millimeters or centimeters (e.g., 10 mm or more). With one suitable arrangement, the lengths of microslots  54  and  56  may be selected so that the microslots form antenna resonances at desired operating frequencies. The lengths of microslots  54  and  56  may, for example, be adjusted to be equal to a half of a wavelength at a desired operating frequency (for slots that are closed at both ends) or equal to a quarter of a wavelength (for slot structures that are open at one end). The spacing between respective microslots may be, for example, on the order of microns to millimeters. 
     Ground plane  52  may be formed from a printed circuit board, a planar metal structure, conductive electrical components, conductive housing walls, other suitable conductive structures, or combinations of these structures. A printed circuit board substrate that is used for all or part of ground plane  52  may be rigid or flexible. An example of a rigid circuit board substrate is the dielectric sometimes referred to as FR4. An example of a flexible printed circuit board material is polyimide. Flexible printed circuits are sometimes referred to as flex circuits and may be mounted to dielectric support structures such as plastic supports. 
     Although antennas such as microslot antenna  20  of  FIG. 3  may be formed from printed circuit board structures, it may be advantageous to form antennas such as antenna  20  from conductive housing structures. With this type of arrangement, it is possible to integrate an antenna into housing  12 . 
     Because microslots such as microslots  56  and  58  are typically narrow (e.g., 10-30 microns), the microslots in antenna  20  may be invisible to the naked eye or may at least be barely noticeable under normal observation. This allows microslot antenna  20  to 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. When antenna  20  is formed on an exterior surface of device  10 , antenna  20  will not generally be blocked by surrounding conductive materials (e.g., conductive housing walls). This allows antenna  20  to operate freely without requiring the formation of potentially unsightly and structurally weak dielectric windows (antenna caps) in device  10 . 
     The microslots of a microslot antenna may be filled with a dielectric such as epoxy to prevent intrusion of liquids, dust, or other foreign matter. This type of filling arrangement may be particularly advantageous in situations in which antenna  20  is formed on a metal wall or other exterior surface of housing  12  where antenna  20  is exposed to the environment. 
     Microslots may be formed in ground plane  52  using any suitable technique. For example, when ground plane  52  is formed from a printed circuit board substrate, microslots may be formed by patterning a conductive layer on the printed circuit board using wet or dry chemical etching (as examples). Other techniques may be used when forming microslots in conductive housing walls. For example, microslots 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 any other suitable techniques. 
     Microslots may be formed in housing  12  (or other suitable ground plane elements  52 ) before such structures are assembled to form device  10  or after device  10  has been assembled. Microslots are typically formed for antenna  20  after housing walls  12  have been formed, but before the other components of device  10  have been mounted in housing  12 . 
     The microslots in antenna  20  such as microslots  54  and  56  serve as antenna resonating elements for antenna  20 , whereas ground plane  52  serves as a ground plane element for antenna  20 . The microslots and ground plane are sometimes referred to as forming “poles” for antenna  20 . Each microslot may form a respective first pole in a pair of antenna poles, whereas ground plane  52  may serve as the second pole in that pair of antenna poles. 
     There may be any suitable number of microslots in an antenna such as antenna  20  of  FIG. 3 . For example, antenna  20  may include two or more microslots having two or more respective lengths. This type of arrangement may be used to provide coverage in one or more communications bands. In a typical arrangement, the length of each microslot may be selected to adjust its resonant frequency. In this way, the frequency coverage of antenna  20  may be configured to coincide with one or more communications bands of interest. 
     If desired, the lengths of the microslots may be selected so that one group of microslots provides coverage in a first communications band, another group of microslots provides coverage in a second communications band, and optional additional groups of microslots provide coverage in respective additional communications bands. The lengths of the microslots may also be selected to provide coverage in only a single band (as an example). 
     In the example of  FIG. 3 , slots  54  form a first group of microslots. This group of slots includes slot  54 A and slot  54 B. The lengths of slots  54 A and  54 B may be slightly different, so that each slot provides coverage at a slightly different frequency (i.e., each slot&#39;s length may be equal to a half of a wavelength at a slightly different frequency). Microslots  56  form a second group of microslots. With the illustrative example of  FIG. 3 , there are five microslots in slot group  56  (i.e., microslots  56 A,  56 B,  56 C,  56 D, and  56 E). Microslots  56 A,  56 B,  56 C,  56 D, and  56 E may each have a different length to collectively provide coverage over a range of frequencies. 
     An illustrative performance graph for an antenna such as antenna  20  of  FIG. 3  is shown in  FIG. 4 . As shown in  FIG. 4 , antenna  20  may be used to cover two communications bands. A first of the two communications bands may be located at frequency f 1  and the other of the two communications bands communications frequency may be located at f 2 . The first band may be (for example) the 2.4 GHz IEEE 802.11 band and the second band may be (for example) the 5.0 GHz IEEE 802.11 band (sometimes referred to by its approximate center frequency of 5.4 GHz). 
     The frequency response of microslot  54 A of  FIG. 3  is given by dashed line  54 A in  FIG. 4 . The frequency response of microslot  54 B of  FIG. 3  is given by dashed line  54 B in  FIG. 4 . Collectively, microslots  54 A and  54 B of microslot group  54  ( FIG. 3 ) may produce the frequency response given by portion  62  of line  66 . This frequency response may cover one or more communications channels associated with the first communications band. The use of multiple microslots (i.e., two microslots  54  in this example) may help to broaden the frequency coverage of antenna  20  in the first communications band. 
     The microslots in microslot group  56  collectively serve to provide frequency coverage for the second communications band. The frequency response of microslot  56 A of  FIG. 3  is given by dashed line  56 A in  FIG. 4 . The frequency response of microslot  56 B of  FIG. 3  is given by dashed line  56 B in  FIG. 4 . Similarly, the frequency responses of microslots  56 C,  56 D, and  56 E of  FIG. 3  are given by respective dashed lines  56 C,  56 D, and  56 E in  FIG. 4 . Collectively, the microslots of microslot group  56  ( FIG. 3 ) may produce the frequency response given by portion  64  of line  66  in  FIG. 4 . 
     As this example demonstrates, the use of multiple microslots may help to broaden the frequency coverage of antenna  20  in each communications band of operation. For example, microslots  54 A and  54 B may provide a greater antenna bandwidth in the vicinity of frequency f 1  than would be possible using only microslot  54 A or  54 B independently. Similarly, microslots  56 A,  56 B,  56 C,  56 D, and  56 E may provide a greater antenna bandwidth at frequency f 2  than would be possible using only a subset of these microslots. 
     Any suitable feed arrangement may be used to feed antenna  20 . As shown schematically in the example of  FIG. 3 , a transmission line such as transmission line  22  may be used to convey radio-frequency signals between antenna  20  and radio-frequency transceiver circuitry such as radio-frequency transceiver circuitry  68 . Transceiver circuitry  68  may include one or more transceivers for handling communications in one or more discrete communications bands. For example, transceiver circuitry  68  may be used to handle communications in 2.4 GHz and 5.4 GHz communications bands. Transceiver circuitry  68  may include a diplexer or other suitable circuitry for combining the signals associated with multiple individual transceivers. For example, transceiver circuitry  68  may include a 2.4 GHz transceiver, a 5.0 GHz transceiver, and a diplexer that allows the 2.4 GHz and 5.0 GHz transceivers to be connected to a common transmission line  22 . 
     Transmission line  22  may be coupled to antenna  20  at feed terminals such as feed terminals  70  and  72 . Feed terminal  70  may be referred to as a ground or negative feed terminal and may be shorted to the outer (ground) conductor of transmission line  22 . Feed terminal  72  may be referred to as the positive antenna terminal. Transmission line center conductor  74  may be used to connect transmission line  22  to positive feed terminal  72 . If desired, other types of antenna coupling arrangements may be used (e.g., based on near-field coupling, using impedance matching networks, etc.). 
     As shown schematically by dashed line  76  in  FIG. 3 , the feed arrangement for antenna  20  may include a matching network. Matching network  76  may include a balun (to match an unbalanced transmission line to a balanced antenna) and/or an impedance transformer (to help match the impedance of the transmission line to the impedance of the antenna). 
     If desired, microslot antennas such as antenna  20  may be fed using different arrangements. In the example of  FIG. 5 , antenna  20  is being fed from a central location. In the configuration of  FIG. 5 , antenna ground terminal  70  is connected to ground plane  52  at a position that is located between microslots  54  and  56 . As a result, some of the microslots (i.e., microslots  54 A and  54 B in this example) are located on one side of ground terminal  70  and other microslots (i.e., microslots  56 A,  56 B,  56 C,  56 D, and  56 E) are located on the other side of ground terminal  70 . Signal conductor  74  may be split into two conductive paths at point  78 . Conductive branch  74 A may be connected between point  78  and first positive antenna feed terminal  72 A. Conductive branch  74 B may be connected between point  78  and second positive antenna feed terminal  72 B. 
     Although antenna feed terminal  70  is located between the microslots of microslot group  54  and the microslots of microslot group  56  in the  FIG. 5  example, this is merely illustrative. Antenna feed terminal  70  may be located between any two adjacent microslots in antenna  20  if desired. 
     The coupling efficiency between transmission line  22  and the microslots of antenna  20  may be greatest for the microslots nearest the positive antenna feed terminal(s). The use of different feed arrangements for feeding microslot antenna  20  may therefore result in different coupling efficiencies for the individual microslot elements in the antenna. This effect is illustrated in the graphs of  FIGS. 6  and  FIG. 7 . 
     In the graph of  FIG. 6 , antenna coupling efficiency is plotted as a function of slot position for an antenna feed arrangement of the type shown in  FIG. 3 . In this illustrative arrangement, microslot  54 A is located in slot position S 1 , microslot  54 B is located in slot position S 2 , microslot  56 A is located in slot position S 3 , microslot  56 B is located in slot position S 4 , microslot  56 C is located in slot position S 5 , microslot  56 D is located in slot position S 6 , and microslot  56 E is located in slot position S 7 . As curve  80  indicates, coupling efficiency is greatest for the microslots located in the vicinity of positive antenna terminal  72 . As the distance from positive antenna feed terminal  72  increases and the distance to ground antenna feed terminal  70  decreases, coupling efficiency tends to decrease. 
     In the graph of  FIG. 7 , antenna coupling efficiency is plotted as a function of slot position for an antenna feed arrangement of the type shown in  FIG. 5 . As with the arrangement of  FIG. 3 , microslot  54 A is located in slot position S 1 , microslot  54 B is located in slot position S 2 , microslot  56 A is located in slot position S 3 , microslot  56 B is located in slot position S 4 , microslot  56 C is located in slot position S 5 , microslot  56 D is located in slot position S 6 , and microslot  56 E is located in slot position S 7 . Coupling efficiency for an antenna that is fed using a configuration of the type shown in  FIG. 5  is represented by curve  82 . 
     As curve  82  of  FIG. 7  indicates, coupling efficiency is greatest for the microslots located in the vicinity of positive antenna terminal  72 A and in the vicinity of positive antenna terminal  72 B. As the distance from positive antenna feed terminals  72 A and  72 B increases and the distance to ground antenna feed terminal  70  decreases, coupling efficiency tends to decrease. 
     As the graphs of  FIGS. 6 and 7  indicate, antenna feed configurations may affect coupling efficiency. Feed arrangements of the type shown in  FIG. 5  may be result in coupling efficiencies that are more uniform than arrangements of the type shown in  FIG. 3 . Because the microslots of  FIG. 5  are fed from a central position (e.g., using a ground feed terminal  70  that lies between the microslots), the maximum distance between the positive and ground feed terminals is less than in configurations of the type shown in  FIG. 3 . As a result, coupling efficiency drops less between the positive and ground feed terminals in center-feed arrangements of the type shown in  FIG. 5  than in edge-feed arrangements of the type shown in  FIG. 3 . If desired, other microslot antenna feed arrangements may be used (e.g., using near-field coupling, using matching network  76 , etc.). The antenna feed arrangements shown in  FIGS. 3 and 5  are merely illustrative. 
     In the examples of  FIGS. 3 and 5 , microslots  54  and  56  are positioned so that the microslots are aligned along their lengths. With this type of configuration, each microslot is oriented so that a point midway along its length overlaps with signal conductor  74  (as an example). This is merely illustrative. For example, the microslots may be oriented so that some of the microslots are bridged by the antenna feed terminals at different points along their lengths (i.e., at points that are near to one of the ends of the microslots). As shown in  FIG. 8 , the microslots may be oriented so that ends  84  of microslots  88  are aligned along common axis  86 . Other configurations (e.g., in which one or more of microslots  88  are horizontally shifted with respect to their positions in  FIG. 8 ) may also be used. 
     If desired, some or all of the microslots in antenna  20  may be open-ended slots. In the examples of  FIGS. 3 ,  5 , and  8 , the microslots are close-ended slots that are surrounded by conductive portions of ground plane element  52 . As shown in  FIG. 9 , open-ended slots  90  may have open ends  92 . Open ends  92  may be filled with air, epoxy, plastic, or other dielectrics. Open-ended microslots and closed-ended microslots may be used together in the same antenna  20  or antenna  20  may be formed from only closed-ended microslots or only open-ended microslots. Antennas  20  such as antenna  20  of  FIG. 9  may be fed using matching network  76  or other suitable feed arrangements. Feed terminals  72  and  70  may be placed at any suitable locations along the lengths of microslots  90 . The arrangement of  FIG. 9  is merely illustrative. 
     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: 20071218
Publication Date: 20130212
Grant Date: 20130212
Priority Date: 20071218
Inventors: CHIANG BING
SPRINGER GREGORY ALLEN
KOUGH DOUGLAS B.
AYALA ENRIQUE
MCDONALD MATTHEW IAN
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q13/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q13/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/40", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 40752498