PATENT DOCUMENT

Publication Number: US-8058954-B2
Application Number: US-39898509-A
Country: US
Kind Code: B2

Title: Transmission line with a cross-hatched ground plane that is either filled with conductive paint or covered by a conductive foil

Abstract:
Transmission lines for electronic devices such as microstrip and stripline transmission lines may be provided that include patterned conductive lines and a conductive paint in the patterned conductive lines. The transmission lines may include one or more planar ground conductors. The ground conductors may include conductive lines arranged in a crosshatch pattern with spaces between the conductive lines. The ground conductors may also include conductive paint in spaces within the crosshatched pattern. The ground conductors may form one or more ground planes for the transmission lines.

Claims:
1. A method of forming a transmission line, comprising:
 forming a transmission line signal conductor; and 
 forming a transmission line planar ground conductor that is separated from the transmission line signal conductor by a dielectric, wherein forming the transmission line planar ground conductor comprises:
 forming a conductor having a pattern of openings; and 
 depositing conductive paint in the openings, wherein forming the conductor having the pattern of openings comprises forming cross-hatched conductive lines, wherein at least one portion of the transmission line bends around an edge of a component of an electronic device and has a bend radius that is less than or equal to 1.5 mm and wherein forming the transmission line planar ground conductor further comprises depositing the conductive paint on the conductor that has the pattern of openings. 
 
 
     
     
       2. The method defined in  claim 1  wherein depositing the conductive paint in the openings comprises depositing a silver paint in the openings. 
     
     
       3. The method defined in  claim 1  wherein forming the cross-hatched conductive lines comprises forming cross-hatched copper lines. 
     
     
       4. A transmission line in an electronic device, comprising:
 a dielectric; 
 a signal conductor; and 
 a planar ground conductor separated from the signal conductor by the dielectric, wherein the planar ground conductor comprises conductive lines arranged in a pattern with spaces between the conductive lines and comprises a conductive paint in the spaces between the conductive lines, wherein the conductive lines comprise crosshatched metal lines, wherein the transmission line has two sections each of which has a length, wherein a first section of the two sections comprises the crosshatched metal lines and the conductive paint, wherein the crosshatched metal lines and the conductive paint extend along the length of the first section, wherein a second section of the two sections comprises a second planar ground conductor formed from a solid metal line that extends along the length of the second section, and wherein the crosshatched metal lines and the conductive paint are electrically coupled to the solid metal line. 
 
     
     
       5. The transmission line defined in  claim 4  wherein the conductive lines comprise crosshatched copper lines. 
     
     
       6. The transmission line defined in  claim 4  wherein the conductive paint comprises silver paint. 
     
     
       7. A transmission line in an electronic device, comprising:
 a dielectric; 
 a signal conductor; and 
 a planar ground conductor separated from the signal conductor by the dielectric, wherein the planar ground conductor comprises conductive lines arranged in a pattern with spaces between the conductive lines and comprises a conductive foil that covers the conductive lines and the spaces. 
 
     
     
       8. The transmission line defined in  claim 7  wherein the conductive foil comprises metal foil. 
     
     
       9. The transmission line defined in  claim 7  further comprising:
 an additional planar ground conductor, wherein the signal conductor and the dielectric are sandwiched between the planar ground conductor and the additional planar ground conductor. 
 
     
     
       10. The transmission line defined in  claim 9  wherein the additional planar ground conductor comprises additional conductive lines arranged in a pattern with spaces between the additional conductive lines and an additional conductive foil that covers the additional conductive lines and the spaces between the additional conductive lines. 
     
     
       11. The transmission line defined in  claim 9  further comprising:
 a plurality of vias that electrically connect the planar ground conductor and the additional planar ground conductor. 
 
     
     
       12. An electronic device comprising:
 a radio-frequency transceiver; 
 a component; 
 an antenna; and 
 a transmission line coupled between the radio-frequency transceiver and the antenna, wherein the transmission line comprises:
 a dielectric; 
 a signal conductor; 
 a planar ground conductor that is separated from the signal conductor by the dielectric, wherein the planar ground conductor has patterned portions that define openings; and 
 a conductive paint in the openings, wherein at least one portion of the transmission line bends around an edge of the component and has a bend radius that is less than or equal to 1.0 mm. 
 
 
     
     
       13. The electronic device defined in  claim 12  wherein the component is a battery. 
     
     
       14. The electronic device defined in  claim 12  wherein the transmission line has at least two sections each of which has a length, wherein a first section of the at least two sections comprises the conductive lines and the conductive paint, wherein the conductive lines and the conductive paint extend along the length of the first section, wherein a second section of the at least two sections comprises a second planar ground conductor formed from a solid metal line that extends along the length of the second section, and wherein the conductive lines and the conductive paint are electrically coupled to the solid metal line. 
     
     
       15. The electronic device defined in  claim 14  wherein the second section comprises a portion of the transmission line that runs along a flat surface of the component. 
     
     
       16. The electronic device defined in  claim 14  wherein the first section comprises the at least one portion of the transmission line that bends around the edge of the component. 
     
     
       17. A transmission line in an electronic device, comprising:
 a dielectric; 
 a signal conductor; and 
 a planar ground conductor separated from the signal conductor by the dielectric, wherein the planar ground conductor comprises conductive lines arranged in a pattern with spaces between the conductive lines and comprises a conductive paint in the spaces between the conductive lines, wherein the transmission line has two sections each of which has a length, wherein a first section of the two sections comprises the conductive lines and the conductive paint, wherein the conductive lines and the conductive paint extend along the length of the first section, wherein a second section of the two sections comprises a second planar ground conductor formed from a solid metal line that extends along the length of the second section, and wherein the conductive lines and the conductive paint are electrically coupled to the solid metal line. 
 
     
     
       18. The transmission line defined in  claim 17  wherein the conductive paint comprises silver paint.

Description:
BACKGROUND 
     This invention relates generally to transmission lines, and more particularly, to microstrip and stripline transmission lines for electronic devices. The transmission lines may be used as part of wireless communications circuitry in handheld electronic devices, as an example. 
     Handheld electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type. 
     Due in part to their mobile nature, handheld electronic devices are often provided with wireless communications capabilities. Handheld 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). Handheld electronic devices may also use other types of communications links. For example, handheld electronic devices may communicate using wireless networking technology bands such as the 2.4 GHz and 5 GHz band used in the WIFI® (IEEE 802.11) wireless networking technology and the 2.4 GHz band used in the BLUETOOTH® wireless networking technology. Communications are also possible in data service bands such as the 3G data communications band at 2170 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. At the same time, manufacturers are continually striving to maximize the performance of wireless communications circuitry and antennas. As one example, manufacturers have made attempts to route transmission lines such as microstrip and stripline transmission lines through the potentially complex geometry of small form factor products while maximizing the efficiency of the transmission lines. 
     When transmission lines are routed through complex geometry of small form factor products, manufacturers may desire to bend the transmission lines at sharp angles (e.g., a small bend radius may help minimize wastes space inside a small form factor housing). Because a typical transmission line includes relatively stiff ground planes formed from solid copper, it can be difficult or impossible to bend the rigid transmission line at all desired angles. Manufacturers have attempted to alleviate some of the problems of these rigid transmission lines by forming flexible transmission lines that have ground planes formed from cross-hatched lines of copper. The cross-hatched lines of copper, however, include gaps in the ground plane that lead to less effective grounding and a less efficient transmission line. 
     It would therefore be desirable to be able to provide improved transmission lines such as microstrip and stripline transmission lines for electronic devices. 
     SUMMARY OF THE INVENTION 
     In accordance with an embodiment of the present invention, transmission lines such as microstrip and stripline transmission lines for electronic devices are provided. The transmission lines may include signal lines and ground conductors. 
     The conductors in the microstrip and stripline transmission lines may be formed from patterned conductive lines with spaces between the conductive lines. The patterned conductive lines may be formed from copper, as an example. The conductors in the transmission lines may also include conductive paint. The conductive paint may be any suitable conductive paint such as a silver paint. If desired, a conductive film may be used in place of the conductive paint. For example, a thin film or sheet of silver may be placed over the patterned conductive lines. The thin film or sheet of silver may cover the spaces between the conductive lines as well as the conductive lines. As an example, the conductors may include conductive paint or conductive film in the spaces between the conductive lines. With another suitable arrangement, each conductor may include conductive paint or conductive film throughout the conductor (e.g., including between the spaces between the conductive lines as well as over the conductive lines). By forming conductors with patterned conductive lines and conductive paint or conductive film, the transmission lines may exhibit increased flexibility and conductivity (e.g., transmission efficiency) relative to conventional transmission lines. 
     Each microstrip transmission line may include a ground conductor that forms a ground plane and at least one signal line. Each stripline transmission line may include at least two ground conductors which may also be shorted together to form a single ground plane. With one suitable arrangement, the ground conductors may be shorted together by a suitable number of vias along the length of each microstrip transmission line. Each stripline transmission line may also include at least one signal line sandwiched between the ground conductors. In general, transmission lines may include any suitable number of signal conductors (e.g., the transmission lines may carry any suitable number of signals along parallel signal lines). 
     With one suitable arrangement, each signal line in some or all of the transmission lines may be formed from a single line of copper and one or more of the ground conductors may be formed from patterned conductive lines and conductive paint. If desired, any suitable number of the signal lines may be formed from patterned conductive lines and conductive paste, conductive paint, and/or conductive film. 
     The transmission lines of the present invention may be used as part of any suitable electronic device. For example, the transmission lines may be used as radio-frequency transmission lines coupled between radio-frequency transceivers and antennas in a wireless electronic device. The transmission lines may also be routed though complex geometry of a small form factor electronic device and may be bent at relatively sharp angles (e.g., the transmission lines may have bend radii such as 1.5 mm or less, 1.0 mm or less, 0.8 mm or less, 0.5 mm or less, etc.). 
     If desired, the signal and ground conductors in a transmission line may be formed from solid lines (e.g., solid lines of copper) along lengths of the transmission line that are not bent at relatively sharp angles. For example, if the transmission line for an electronic device does not need to be bent at a sharp angle along one or more particular lengths of the transmission line, those particular lengths of the transmission line may be formed with conductors formed from solid lines. With this type of arrangement, portions of the transmission line that are bent at sharp angles during manufacturing or in the assembled device may be selectively formed from patterned conductive lines with spaces and with conductive paint or conductive film to fill in the spaces. 
     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 handheld electronic device in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative handheld electronic device in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional end view of an illustrative microstrip transmission line in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional end view of an illustrative stripline transmission line in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional end view of an illustrative stripline transmission line that has vias that electrically couple together a first and a second ground conductor in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional end view of an illustrative stripline transmission line that includes multiple signal lines in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional end view of an illustrative stripline transmission line that includes multiple signal lines and that may include vias along the sides of the transmission line in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional end view of an illustrative stripline transmission line that includes multiple signal lines and that may include vias between at least some of the signals lines in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional top view of an illustrative stripline transmission line that includes patterned conductive lines with spaces between the conductive lines and conductive paint in the spaces between the conductive lines in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional side view of the illustrative stripline transmission line of  FIG. 9  in accordance with an embodiment of the present invention. 
         FIG. 11  is a side view of an illustrative electronic device that may include a flexible transmission line with a hybrid ground plane that may be formed from crosshatched ground conductors and a conductive paint in accordance with an embodiment of the present invention. 
         FIG. 12  is a top view of the illustrative electronic device and the flexible transmission line shown in  FIG. 11  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates generally to transmission lines and, more particularly, to microstrip and stripline transmission lines for electronic devices. The transmission lines may include trace lines (e.g., copper traces or other metal traces that form signal lines) and one or more ground conductors. The ground conductors may include conductive lines arranged in a pattern. There may be spaces in the pattern between the conductive lines. The spaces between the conductive lines may be filled with conductive paint such as a silver paint material. Materials such as silver paint have previously been used to fill copper-lined vias. A typical silver paint includes solvent and silver particles. When dried, the silver paint forms a conductor. 
     The ground conductor may be formed from a conductive structure such as a planar layer of metal with pattern of openings. The patterned metal in the ground conductor may be, for example, a pattern of crosshatched lines (e.g., a pattern of crosshatched copper lines). The conductive paint and crosshatched conductive lines may form one or more ground planes for the transmission lines. As one example, the transmission lines may be used as part of wireless electronic devices. 
     Conductors for transmission lines that are formed from solid metal structures can be inflexible if they are thick. By providing spaces between the solid metal structures, flexibility may be increased. Conductivity may be enhanced in this type of flexible structure by incorporating conductive paint. For example, conductive paint may be placed in the spaces between the solid metal structures. Conductive paint or conductive foil may also be used as an ancillary conductive layer that is placed over the solid metal structures with spaces (e.g., over the spaces and over the solid metal structures). Any suitable conductive foil such as aluminum foil or silver foil may be used. 
     Solid metal structures for forming transmission line conductors may be formed using techniques such as evaporation, sputtering, and electroplating. Conductive paints tend to be more flexible than solid metals because they are formed from thin layers of conductive particles rather than thick lines of solid metal. Initially, a conductive paint is a liquid solution including a solvent, conductive particles, and additional agents such as binders. Typical solvents include ethanol and acetone. Typical conductive particles include metals such as silver and platinum. Other solvents and conductive particles may be used if desired. After a liquid conductive paint has been applied to a transmission line, the solvent may be evaporated so that the conductive particles coalesce and form a good conductor. Conductive paints are sometimes referred to as conductive pastes or conductive inks. 
     The wireless electronic devices may 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, which is sometimes described herein as an example, the portable electronic devices are handheld electronic devices. 
     The handheld devices may be, for example, cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, and handheld gaming devices. The handheld devices may also be hybrid devices that combine the functionality of multiple conventional devices. Examples of hybrid handheld 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, and supports web browsing. These are merely illustrative examples. 
     An illustrative handheld electronic device in accordance with an embodiment of the present invention is shown in  FIG. 1 . Device  10  may be any suitable portable or handheld electronic device. 
     Device  10  may have housing  12 . Device  10  may include one or more antennas for handling wireless communications. Embodiments of device  10  that contain one antenna and embodiments of device  10  that contain two or more antennas are sometimes described herein as examples. 
     Device  10  may handle communications over one or more communications bands. For example, in a device  10  with two antennas, a first of the two antennas may be used to handle cellular telephone communications in one or more frequency bands, whereas a second of the two antennas may be used to handle data communications in a separate communications band. With one suitable arrangement, which is sometimes described herein as an example, the second antenna is configured to handle data communications in a communications band centered at 2.4 GHz (e.g., communications frequencies used in wireless networking technologies such as the WIFI® and/or BLUETOOTH® wireless networking technologies). 
     Housing  12 , which is sometimes referred to as a case, may be formed of any suitable materials including, plastic, glass, ceramics, metal, or other suitable materials, or a combination of these materials. 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 antennas and may be used as part of transmission lines in device  10 . For example, metal portions of housing  12  may be shorted to one or more transmission line ground planes. Housing  12  may be shorted to an internal ground plane in device  10  to create a larger ground plane element for that device  10 . 
     Housing  12  may have a bezel  14 . The bezel  14  may be formed from a conductive material, if desired. Bezel  14  may serve to hold a display or other device with a planar surface in place on device  10 . As shown in  FIG. 1 , for example, bezel  14  may be used to hold display  16  in place by attaching display  16  to housing  12 . 
     Display  16  may be a liquid crystal diode (LCD) display, an organic light emitting diode (OLED) display, a plasma display, multiple displays that use one or more different display technologies, 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  or may be provided using a separate touch pad device. 
     Display screen  16  (e.g., a touch screen) is merely one example of an input-output device that may be used with handheld electronic device  10 . If desired, handheld electronic device  10  may have other input-output devices. For example, handheld electronic device  10  may have user input control devices such as button  19 , and input-output components such as port  20  and one or more input-output jacks (e.g., for audio and/or video). Button  19  may be, for example, a menu button. Port  20  may contain a 30-pin data connector (as an example). Openings  24  and  22  may, if desired, form microphone and speaker ports. 
     With one suitable arrangement, the antennas of device  10  are located in the lower end  18  of device  10 , in the proximity of port  20 . 
     Device  10  may have one or more transmission lines that convey signals between components in device  10 . For example, device  10  may have a transmission line  30  coupled between transceiver circuitry  26  and an antenna  28 . Transmission line  30  may be, for example, a stripline transmission line, a microstrip transmission line, or any other suitable type of transmission line. Transmission line  30  may convey radio-frequency signals between transceiver  26  and antenna  28 . 
     With one suitable arrangement, transmission line  30  may include a ground plane formed from patterned conductive lines and a conductive paint. As one example, there may be spaces between the conductive lines. The conductive paint may fill the spaces between the conductive lines. The conductive paint may increase the efficiency of the ground plane and thereby increase the transmission efficiency of line  30 . Because the conductive lines are patterned with spaces between the conductive lines, the flexibility of transmission line  30  may be improved relative to transmission lines with ground planes formed from a solid line of metal. 
     A schematic diagram of an embodiment of an illustrative handheld electronic device is shown in  FIG. 2 . Handheld device  10  may be 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 electronic device. 
     As shown in  FIG. 2 , handheld 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. 
     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 , button  19 , microphone port  24 , speaker port  22 , and dock connector port  20  of  FIG. 1  are examples of input-output devices  38 . 
     Input-output devices  38  can include user input-output devices  40  such as buttons, touch screens, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, etc. 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, transmission lines such as microstrip and stripline transmission lines, one or more antennas, and other circuitry for handling RF wireless signals. 
     Device  10  can communicate with external devices such as accessories  46  and computing equipment  48  (e.g., a media host), 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 (router) 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 handheld electronic device  10 ), or any other suitable computing equipment. 
     A cross-sectional end view of an illustrative microstrip transmission line  52  is shown in  FIG. 3 . As shown in  FIG. 3 , a microstrip  52  includes a strip of conductor  54  sometimes referred to as a trace line or a signal line above a ground plane  56 . Conductor  54  and ground plane  56  may be formed using any suitable materials. As one suitable example, conductor  54  and ground plane  56  may be formed from sheets or lines of copper. Ground plane  56  may be a somewhat planar structure, as an example. 
       FIG. 4  shows a cross-sectional end view of an illustrative stripline transmission line  60 . As shown in  FIG. 4 , stripline  60  includes a strip of conductor  54  sandwiched between two substantially parallel ground planes  56  and  70 . 
     Microstrip  52  and stripline  60  may be fabricated using any suitable technique. With one suitable arrangement, transmission lines such as microstrip  52  and stripline  60  may be formed using a printed circuit board (PCB) technology. For example, stripline  60  may be formed by depositing the lower ground conductor  56  on a non-conductive substrate  72  (e.g., a dielectric substrate). Alternatively, a subtractive method may be used in which the non-conductive substrate  72  is covered by a sheet of conductor material and the lower ground conductor  56  is formed by etching away the portions of the sheet of conductor material that do not correspond to the lower conductor  56 . 
     After forming the lower conductor  56 , a dielectric layer  74  may be deposited over the lower conductor  56  and conductor  54  may be formed in, or over, the dielectric layer  74 . As described above in connection with the lower ground conductor  56 , signal conductor  54  may be formed using any suitable method such as an additive method or a subtractive method. In the additive method, conductive material is deposited onto layer  74  along the length of the transmission line to form conductor  56 . In the subtractive method, conductive material is first deposited as a sheet over the surface of the dielectric  74 . Subsequently, the conductive material that does not correspond to conductor  54  is etched away using a patterned etching process. With another suitable arrangement, conductor  54  may be formed by etching a trench into dielectric  74  and filling the trench with conductive material. 
     Once conductor  56  is formed, another dielectric layer  76  may be deposited as shown in  FIG. 4 . The upper ground conductor  70  (e.g., the upper ground conductor  70  shown in  FIGS. 4 and 5 ) may formed over or within dielectric layer  76 . As with the lower ground conductor  56  and the signal conductor  54  described above, the upper ground conductor  70  may be formed using any suitable technique. 
     If desired, substrate and dielectric material in transmission lines such as lines  52  and  60  may extend beyond the dimensions of the transmission lines. For example, substrate  72  and dielectric layers  74  and  76  may be somewhat wider than conductors  56 ,  54 , and  70 . If desired, dielectric layers  74  and  76  may extend widthwise beyond the dimensions of vias  58  of  FIG. 5 . 
     The substrate and the dielectric layers in the circuit board forming transmission lines  52  and  60  may be formed using any suitable materials. For example, the substrate and the dielectric layers in microstrip  52  and stripline  60  may be formed from polytetrafluoroethylene (PTFE), FR-2 (phenolic cotton paper), FR-3 (cotton paper and epoxy), FR-4 (woven glass and epoxy), FR-5 (woven glass and epoxy), FR-6 (matte glass and polyester), G-10 (woven glass and epoxy), CEM-1 (cotton paper and epoxy), CEM-2 (cotton paper and epoxy), CEM-3 (woven glass and epoxy), CEM-4 (woven glass and epoxy), CEM-5 (woven glass and polyester), paper impregnated with phonolic resin, resins reinforced with glass fibers such as fiberglass mat impregnated with epoxy resin (sometimes referred to as FR-4), plastics, polystyrene, polyimide, ceramics, or any other suitable material. Circuit boards with substrate and dielectric materials fabricated from materials such as FR-4 are commonly available, are not cost-prohibitive, and can be fabricated with multiple layers of metal (e.g., three layers). So-called flex circuits, which are flexible circuit board materials such as polyimide, may also be used in device  10 . By using flex circuits, a manufacturer can increase the flexibility of the substrate and the dielectric layers in transmission lines such as lines  30 ,  52 , and  60 . 
     If desired, stripline  60  may include a plurality of vias  58  that connect ground planes  56  and  70  together. For example, as shown in  FIG. 5 , stripline  60  may include vias  58  on each side of conductor  54  that electrically connect the top and bottom ground planes  56  and  70  together. While  FIG. 5  only shows a cross-sectional end view of vias  58 , stripline  60  may include multiple vias  58  at suitable positions along the length of stripline  60 . For example, vias may be placed at regular intervals along the length stripline  60 , near bends in stripline  60 , at regular intervals along the length of stripline  60  except near bends in stripline  60 , near the end of stripline  60  (e.g., near connectors connected to stripline  60 ), and at any other suitable locations. As shown in  FIG. 5 , stripline  60  may include dielectric layer  72 . 
     Vias such as vias  58  may be formed at any suitable time during the fabrication of a transmission line. For example, vias  58  may be formed after the dielectric layer  74  above conductor  54  is deposited. With another suitable arrangement, a lower half of vias  58  may be formed after the dielectric layer  74  above the lower conductor  56  is formed and an upper half of vias  58  may be formed after the dielectric layer  76  above conductor  54  is deposited. 
     As shown in  FIG. 6 , transmission lines such as lines  52  ( FIG. 3) and 60  ( FIGS. 4 and 5 ) may include multiple transmission lines (e.g., microstrip  52  and stripline  60  may include multiple signal lines). The transmission lines may include multiple signals lines arranged side-by-side, as an example. In general, a transmission line such as microstrip line  62  may include any suitable number of signal conductors  54  as well as any suitable number of ground planes  56  and  70 . 
     If desired, transmission lines that include multiple signals lines may also include one or more vias  58 . For example, as shown in  FIG. 7 , transmission line  62  may include vias  58  along each side of the transmission line  62 . Vias  58  may serve to extend the ground plane of line  62  formed by ground plane conductors  56  around the sides of the transmission line  62 . As shown in  FIG. 7 , transmission line  62  may include conductor  70 . 
       FIG. 8  shows one potential arrangement for transmission line  62 . In the arrangement shown in  FIG. 8 , transmission line  62  may include one or more vias that are between some of the signal lines that make up the line  62 . In the example of  FIG. 8 , there may be vias on either side of signal lines  55 . The arrangement shown in  FIG. 8  may be particularly useful when, as an example, signal lines  55  carry relatively high power signals and/or when a manufacturer wants to ensure that radio-frequency signals carried on signal lines  55  are not degraded (e.g., the manufacturer desires to minimize interference and maximize the transmission efficiency of signal lines  55  relative to signal lines  54 ). As shown in  FIG. 8 , transmission line  62  may include conductors  56  and  70 . 
     As shown in  FIG. 9 , a transmission line such as transmission line  52  ( FIG. 3 ),  60  ( FIGS. 4 and 5 ), or  62  ( FIGS. 6 ,  7 , and  8 ) may include one or more planar ground conductors formed from patterned conductive lines with spaces between the lines and a conductive paint or conductive film that electrically bridges the spaces. For example, the cross-sectional top view shown in  FIG. 9  illustrates how a signal conductor  54  may run over a lower ground conductor  56  separated by a dielectric (not shown in  FIG. 9 ). 
     The ground conductor  56  may include conductive lines  64 . The conductive lines  64  may be patterned and there may be spaces between the conductive lines  64 . With one suitable arrangement, the conductive lines  64  may be arranged in a crosshatched pattern (e.g., the pattern shown in  FIG. 9 ). In general, conductive lines  64  may be formed in any suitable pattern. For example, conductive lines  64  may be a plurality of parallel conductive lines that are aligned along the length of line  60 , across the width of line  60 , or at any suitable angle to the lengthwise dimension of line  60  (e.g., the direction in which signals travel along signal line  54 ). If desired, conductive lines  64  may be arranged randomly while leaving at least some spaces which are not covered by conductive lines  64 . 
     Ground conductor  56  may also include a conductive film  80  (shown as dotted lines in  FIG. 10 ) or a conductive paint  66 . As one example, the conductive paint  66  may be applied to the spaces between the conductive lines  64  (e.g., the shaded areas of  FIG. 9 ). If desired, the conductive paint  66  may be selectively applied in specific regions of ground conductor  56 . With one suitable arrangement, the conductive paint  66  may be applied over the conductive lines and the spaces between the conductive lines. If desired, the conductive paint  66  may be applied to substrate  72  and to dielectric  76  before conductive lines such as lines  64  are formed (e.g., the conductive paint may be below the conductive lines  64 ) as shown in  FIG. 10 . Conductive paint  66  may be applied below and above the conductive lines such that the conductive paint surrounds the conductive lines  66 , as an example. Conductive paint  66  may be applied using any suitable technique. For example, conductive paint  66  may be applied using a screen printing technique and conductive paint  66  may be applied by a squeegee technique in which a liquid form of the paint  66  is spread in one or more locations and a mechanical pressure is used to spread the paint  66  across the spaces between conductive lines  64 . 
     A side view of the stripline  60  shown in  FIG. 9  is illustrated by  FIG. 10 . As shown in  FIG. 10 , transmission line  60  may be formed with a first dielectric layer  72  (e.g., a substrate), a lower ground conductor layer  56 , a first optional conductive film layer  80 , a second dielectric layer  74 , a signal conductor layer  54 , a third dielectric layer  76 , an upper ground conductor layer  70 , a second optional conductive film layer  80 , and an optional fourth dielectric layer  78  (e.g., a layer that covers transmission line  60 ). This is merely one example and, in general, transmission line  60  may be formed using any suitable number of layers, any suitable arrangement of layers, and any suitable types of layers. 
     As shown in  FIG. 10 , there may be spaces between the conductive lines  64 . The conductive lines  64  are illustrated by the shaded portions in conductors  56  and  70  of  FIG. 10 . The spaces between conductive lines  64  are illustrated by the un-shaded portions of conductors  56  and  70 . Conductive paint  66  may be applied in the spaces to electrically bridge the spaces (e.g., to electrically couple together conductive lines  64  across the spaces between the conductive lines). Alternatively or in addition to the conductive paint  66 , a conductive film  80  may be applied above and/or below conductors  56  and  70 . The conductive film may help to electrically bridge the spaces between the conductive lines. 
       FIGS. 11 and 12  illustrate one potential way in which a transmission line  100  (e.g., a transmission line  52  ( FIG. 3 ),  60  ( FIGS. 4 and 5 ), or  62  ( FIGS. 6 ,  7 , and  8 )) may be routed through the geometry of an electronic device  10 . In the example of  FIGS. 11 and 12 , transmission line  100  may be routed around a first component  82  and line  100  may be coupled between a second component  84 , a third component  86 , and a fourth component  88 . Signal lines and ground conductors may be coupled to components  84 ,  86 , and  88  at connectors  90 . As one example, components  82 ,  84 ,  86 , and  88  may be a battery, a motherboard, a radio-frequency transceiver, and an antenna, respectively. 
     As illustrated by arrows  92  in  FIGS. 11 and 12  and by the shaded regions in  FIG. 12 , there may be regions of transmission line  100  that are bent relatively sharply (e.g., there may be at least one portion of transmission line  100  that bends around an edge of a component such as component  82 ,  84 ,  86 , and  88  and that has a bend radius that is less than or equal to 1.0 mm). With one suitable arrangement, transmission line  100  may be bent at an angle of approximately 90° in each of the regions  92 . If desired, transmission line  100  may have ground conductors formed from conductive lines with spaces and conductive paint in the spaces in the shaded regions (e.g., regions  92 ) of  FIG. 12  and may have ground conductors that are formed from a solid line of conductive material in the un-shaded regions. 
     As shown in  FIG. 12 , transmission line  100  may include signal lines  94  that convey signals between components  84  and  86  and may include one or more signal lines  96  that convey signals between components  86  and  88 . With one suitable arrangement, signal lines  94  may convey data signals between motherboard  84  and transceiver  86  and signal lines  96  may convey radio-frequency signals that are to be transmitted to antenna  88  from transceiver  86  or that have been received by antenna  88  from antenna  88  to transceiver  86 . 
     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: 20090305
Publication Date: 20111115
Grant Date: 20111115
Priority Date: 20090305
Inventors: YEATES KYLE H.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01P3/08", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01P11/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/49124", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01P3/08", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01P11/003", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 42677722