PATENT DOCUMENT

Publication Number: US-8583187-B2
Application Number: US-89950910-A
Country: US
Kind Code: B2

Title: Shielding structures for wireless electronic devices with displays

Abstract:
Electronic devices such as computers and handheld devices are provided. The electronic devices may have electrical components such as displays that are driven by driver circuitry. During operation, the driver circuitry may generate radio-frequency noise. Communications circuitry in the electronic devices may be shielded from the radio-frequency noise by radio-frequency shielding structures. The shielding structures may be mounted on portions of the display module, on a cover glass layer, or on other structures such as housing structures. The radio-frequency shielding structures may be formed from one or more metal segments. The metal segments may run along edges of the display. A device housing may have a ground formed from a conductive peripheral member that runs around peripheral edges of the housing and a conductive plate that is connected to the conductive peripheral member. The radio-frequency shielding structure may be connected to the ground using conductive structures.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 antenna structures; 
 a display module that generates radio-frequency display module noise signals; and 
 a radio-frequency shielding structure having at least one conductive segment that runs along an edge of the display module, wherein at least part of the radio-frequency shielding structure is interposed between the display module and the antenna structures and shields the antenna structures from the radio-frequency display module noise signals. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the display module comprises a substrate, wherein the at least one conductive segment comprises three conductive segments that respectively run along three edges of the display module, and wherein the three conductive segments comprise conductive traces on the substrate. 
     
     
       3. The electronic device defined in  claim 2  wherein the substrate comprises a thin-film-transistor layer that includes a plurality of thin-film transistors. 
     
     
       4. The electronic device defined in  claim 3  wherein the thin-film-transistor layer comprises a layer of glass and wherein the conductive segments comprise metal traces on the glass. 
     
     
       5. The electronic device defined in  claim 4  wherein the display module comprises gate lines, common voltage lines, and data lines and wherein the metal traces are formed from a material that is also used in forming at least part of the gate lines, common voltage lines, and data lines. 
     
     
       6. The electronic device defined in  claim 1  wherein the shielding structure comprises metal tape. 
     
     
       7. The electronic device defined in  claim 1  wherein the display module has a front surface and a rear surface, wherein the at least one conductive segment comprises three conductive segments that respectively run along three edges of the display module, and wherein the shielding structure wraps around the three edges of the display module so that at least some of the front surface and at least some of the rear surface of the display module are covered by the shielding structure. 
     
     
       8. The electronic device defined in  claim 1  wherein the display module comprises conductive lines and display driver circuitry that is configured to drive pulses onto the conductive lines that have smoothed edges to reduce frequency harmonics in the radio-frequency display module noise signals. 
     
     
       9. The electronic device defined in  claim 1  wherein the display module comprises display driver circuitry and conductive lines onto which the display driver circuitry drives display control pulses, wherein the conductive lines include loading circuitry that is configured to smooth edges in the display control pulses to reduce frequency harmonics in the radio-frequency display module noise signals. 
     
     
       10. The electronic device defined in  claim 1 , wherein the display module has opposing first and second ends, the electronic device further comprising:
 a display driver integrated circuit mounted at the first end of the display module, wherein the conductive segment is at the second end of the display module and wherein the conductive segment is interposed between the display module and the antenna structures. 
 
     
     
       11. The electronic device defined in  claim 10  wherein the display module includes a color filter layer and a thin-film-transistor layer and wherein the radio-frequency shielding structure is formed on the thin-film-transistor layer. 
     
     
       12. The electronic device defined in  claim 10  further comprising a cover layer that covers the display module, wherein the radio-frequency shielding structure is formed on the cover layer. 
     
     
       13. The electronic device defined in  claim 12  wherein the cover layer comprises a glass substrate having a patterned opaque masking layer and wherein the radio-frequency shielding structure comprises a metal trace formed on the opaque masking layer. 
     
     
       14. The electronic device defined in  claim 10  further comprising a housing in which the display module is mounted, wherein the housing comprises a peripheral conductive member that runs along peripheral edges of the housing, wherein the housing comprises a conductive plate that is connected to the peripheral conductive member, and wherein the conductive plate comprises a protrusion on which the radio-frequency shielding structure is formed. 
     
     
       15. The electronic device defined in  claim 14  further comprising a layer of plastic interposed between the protrusion and the radio-frequency shielding structure. 
     
     
       16. The electronic device defined in  claim 10  further comprising:
 a housing that forms a ground element; and 
 a flexible printed circuit having a ground trace, wherein the radio-frequency shielding structure is electrically connected to the ground element at least partly by the ground trace on the flexible printed circuit. 
 
     
     
       17. The electronic device defined in  claim 1  further comprising:
 a housing, wherein the antenna structures comprise a cellular telephone antenna at a first end of the housing, wherein the display module has opposing first and second ends and an active region between the first and second ends, wherein the display has a display driver circuit at the first end of the display module, wherein the cellular telephone antenna is located adjacent to the second end of the display module, wherein the radio-frequency shielding structures area interposed between the cellular telephone antenna and the active region of the display module. 
 
     
     
       18. The electronic device defined in  claim 17  wherein the display module has a longitudinal axis that passes through the first and second ends and wherein the radio-frequency shielding structures comprise at least one metal segment that runs perpendicular to the longitudinal axis. 
     
     
       19. The electronic device defined in  claim 18  wherein the metal segment is formed on a substrate layer in the display module. 
     
     
       20. The electronic device defined in  claim 18  further comprising a layer of cover glass that covers the display module, wherein the metal segment is formed on the cover glass. 
     
     
       21. The electronic device defined in  claim 18  wherein the housing comprises a conductive plate having a portion that is covered by a plastic layer and wherein the metal segment is formed on the plastic layer. 
     
     
       22. The electronic device defined in  claim 18  wherein the housing comprises conductive portions that form a ground element and wherein the electronic device further comprises conductive structures that electrically connect the metal segment to the ground element. 
     
     
       23. The electronic device defined in  claim 22  wherein the conductive structures comprise conductive foam. 
     
     
       24. The electronic device defined in  claim 22  wherein the conductive structures comprise a metal spring. 
     
     
       25. The electronic device defined in  claim 22  wherein the conductive structures comprise a metal path on a thin-film-transistor layer in the display module. 
     
     
       26. The electronic device defined in  claim 1  further comprising:
 a conductive housing structure that forms a system ground, wherein the antenna structures comprise a cellular telephone antenna that is formed at least partly using the conductive housing structure; 
 a printed circuit board on which integrated circuits are mounted; and 
 a flex circuit that grounds the printed circuit board to the display module, wherein the flex circuit has at least one ground trace that is connected to the conductive housing structure by conductive adhesive and wherein the flex circuit is devoid of vias in a region overlapping the conductive adhesive. 
 
     
     
       27. The electronic device defined in  claim 26  wherein the flex circuit has at least three layers including a first outer layer and a second outer layer, wherein the ground trace is formed from the first outer layer, and wherein the second outer layer forms an additional ground trace, and wherein the flex circuit is devoid of vias that connect the ground trace and the additional ground trace in the region overlapping the conductive adhesive, wherein the ground trace forms a ground path between the printed circuit board and the conductive housing structure, and wherein the additional ground trace forms a ground path between the printed circuit board and the display module. 
     
     
       28. The electronic device defined in  claim 27  wherein the ground trace has a gap that is devoid of metal, wherein the gap is located between the display module and the region overlapping the conductive adhesive, and wherein the gap forms an open circuit in the ground trace between the display module and the system ground.

Description:
BACKGROUND 
     This relates generally to wireless electronic devices and, more particularly, to reducing signal interference in wireless electronic devices with displays. 
     Electronic devices such as cellular telephones and other devices often contain wireless communications circuitry. The wireless communications circuitry may include, for example, cellular telephone transceiver circuits for communicating with cellular telephone networks. Wireless communications circuitry in an electronic device may also include wireless local area network circuits and other wireless circuits. Antenna structures are used in transmitting and receiving wireless signals. 
     Electronic devices also often contain displays. For example, liquid crystal displays are often provided in cellular telephones. Displays contain arrays of image pixels. For example, liquid crystal displays contain arrays of image pixels based on liquid crystal material. Electrodes in the arrays are used to apply controlled electric fields to the liquid crystal material to change its optical properties and thereby create an image on the display. Display driver circuits are used to generate drive signals for the electrodes in the array. 
     Challenges arise when mounting displays and wireless circuitry within electronic devices. In many devices, for example, space is at a premium, so there is a desire to locate antennas and displays in close proximity to each other. At the same time, the display driver circuits that are used in driving signals into a display can produce signals that can interfere with the operation of wireless circuits. This potential for signal interference tends to be exacerbated when display structures are located in the vicinity of antennas and other wireless circuitry. 
     It would therefore be desirable to provide improved ways in which to incorporate displays and wireless circuits in wireless electronic devices. 
     SUMMARY 
     An electronic device such as a portable device may have an electrical component such as a display. The display may be implemented using a rectangular display module that is located on a front surface of an electronic device. A cover layer such as a layer of cover glass may be used to cover the display module. The display module may be based on a liquid crystal display configuration having a layer of liquid crystal material interposed between opposing color filter and thin-film-transistor layers. The color filter layer and thin-film-transistor layer may have substrates formed from materials such as glass. 
     Display driver circuitry may be used to drive signals into the display. The display driver circuitry may include a driver integrated circuit that is mounted to one end of the thin-film-transistor layer. Control lines such as gate lines may be used to distribute signals to the display from the display driver circuitry. 
     During operation of the display module, the display module may generate radio-frequency noise signals. The noise signals may serve as a source of potential interference for other circuitry in the device such as wireless circuitry. Wireless circuitry may include antenna structures such as cellular telephone antenna structures and wireless local area network antenna structures. 
     Radio-frequency shielding structures may provide electromagnetic shielding that helps prevent radio-frequency noise signals from the display module from interfering with the operation of wireless circuitry. Radio-frequency shielding structures may be formed from conductive segments of material such as metal lines. The conductive segments may run along one or more of the edges of the display module. For example, three conductive segments may be configured to form a U-shaped shielding structure. A single conductive strip may be located along the end of the display module opposite to the end that contains the display driver integrated circuit (as an example). In locations such as these, the shielding structure may help to block radio-frequency noise from the display. 
     Shielding structures may be formed from patterned conductive material that is located on part of a display module such as on a thin-film-transistor layer substrate, may be formed on a cover glass layer, or may be formed on other structures such as a protruding portion of a housing plate or other housing structure. Conductive structures such as conductive adhesive, conductive lines, conductive foam, conductive springs, and conductive traces on flex circuit substrates and other substrates may be used in electrically connecting radio-frequency shielding structures to a ground element in an electrical device. The ground element may be formed by conductive housing structures such as a conductive peripheral housing structure that runs around the edges of the device and a conductive plate structure that spans the width of the device and that is connected on its left and right edges to the conductive peripheral housing structure. 
     The display driver circuitry may issue control pulses for image pixels in the display. The display driver circuitry may, for example, issue gate control pulses on gate lines. The shape of the control pulses that are issued may be smoothed internally by the display driver circuitry or externally using discrete or distributed loading circuitry on the signal lines. Smoothing the control pulses so that their edges have reduced abruptness may help reduce frequency harmonics in the radio-frequency noise produced by the display module and may therefore reduce interference with the wireless circuitry. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with a display and wireless circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of a display module and display cover layer in accordance with an embodiment of the present invention. 
         FIG. 3  is a circuit diagram of a liquid crystal display image pixel circuit in accordance with an embodiment of the present invention. 
         FIG. 4  is a schematic diagram of an illustrative image pixel array and associated driver circuitry in which gate drivers have been implemented using circuitry adjacent to the image pixel cells in accordance with an embodiment of the present invention. 
         FIG. 5  is a schematic diagram of an illustrative image pixel array and associated driver circuitry in which gate drivers have been implemented using circuitry within a driver integrated circuit in accordance with an embodiment of the present invention. 
         FIG. 6  is a circuit diagram of an image pixel array and associated driver circuitry in accordance with an embodiment of the present invention. 
         FIG. 7  is a graph of an illustrative data line signal of the type that may be used in the circuitry of  FIG. 6  in accordance with an embodiment of the present invention. 
         FIG. 8  is a graph of an illustrative red channel demultiplexing control signal of the type that may be used in the circuitry of  FIG. 6  in accordance with an embodiment of the present invention. 
         FIG. 9  is a graph of an illustrative blue channel demultiplexing control signal of the type that may be used in the circuitry of  FIG. 6  in accordance with an embodiment of the present invention. 
         FIG. 10  is a graph of an illustrative green channel demultiplexing control signal of the type that may be used in the circuitry of  FIG. 6  in accordance with an embodiment of the present invention. 
         FIG. 11  is a graph of an illustrative gate line signal that may be used in the circuitry of  FIG. 6  in accordance with an embodiment of the present invention. 
         FIG. 12  is a circuit diagram of an illustrative pulse smoothing circuit that may be used in circuitry of the type shown in  FIG. 6  in accordance with an embodiment of the present invention. 
         FIG. 13  is a circuit diagram of a signal line of the type shown in  FIG. 6  showing how the signal line may exhibit distributed resistance that may serve as the resistance of  FIG. 12  in accordance with an embodiment of the present invention. 
         FIG. 14  is a circuit diagram of a signal line of the type shown in  FIG. 6  showing how the signal line may exhibit distributed capacitance that may serve as the capacitance of  FIG. 12  in accordance with an embodiment of the present invention. 
         FIG. 15  is a graph showing how gate line and demultiplexing control signals in circuitry of the type shown in  FIG. 6  may be smoothed to minimize the generation of signal harmonics with the potential to interfere with wireless circuit operation in accordance with an embodiment of the present invention. 
         FIG. 16  is a graph of a conventional display driver signal spectrum showing how harmonic signals that may potentially interfere with wireless circuit operation may be generated during device operation. 
         FIG. 17  is a graph of a display driver signal spectrum of the type that may be produced using smoothed signals of the type shown in  FIG. 15  in accordance with an embodiment of the present invention. 
         FIG. 18  is a top view of an illustrative electronic device with antenna structures formed at upper and lower ends of the device in accordance with an embodiment of the present invention 
         FIG. 19  is a top view of an illustrative electronic device showing how an antenna may be formed at least partly using conductive device housing structures in accordance with an embodiment of the present invention. 
         FIG. 20  is a top view of an illustrative electronic device showing how a strip-shaped conductive element may serve as a shielding structure that helps minimize radio-frequency interference between a display and wireless circuitry in the device in accordance with an embodiment of the present invention. 
         FIG. 21  is a top view of an illustrative electronic device showing how a U-shaped conductive element may serve as a shielding structure that helps minimize radio-frequency interference between a display and wireless circuitry in the device in accordance with an embodiment of the present invention. 
         FIG. 22  is a top view of an illustrative electronic device showing how a conductive element having the shape of a rectangular ring that surrounds a display may serve as a shielding structure that helps minimize radio-frequency interference between the display and wireless circuitry in the device in accordance with an embodiment of the present invention. 
         FIG. 23  is a cross-sectional side view of display structures with signal shielding structures formed at the interface with a display cover layer in accordance with an embodiment of the present invention. 
         FIG. 24  is a cross-sectional side view of a signal shielding structure of the type shown in  FIG. 23  showing how the shielding structure may be grounded to a conductive housing wall structure in accordance with an embodiment of the present invention. 
         FIG. 25  is a cross-sectional side view of a signal shielding structure of the type shown in  FIG. 24  showing how the shielding structure may be grounded to a conductive housing structure using conductive structures interposed between the shielding structure and the conductive housing structure in accordance with an embodiment of the present invention. 
         FIG. 26  is a cross-sectional side view of an electronic device with shielding structures that cover one or more edges in a display to help minimize radio-frequency interference between the display and wireless circuitry in the device in accordance with an embodiment of the present invention. 
         FIG. 27  is a top view of a conventional display module with a flex circuit tail and copper tape that covers a display driver integrated circuit in the display module. 
         FIG. 28  is a top view of a display module having shielding structures that connect to a conductive layer on a flex circuit tail and that help minimize radio-frequency interference between the display and wireless circuitry in the device in accordance with an embodiment of the present invention. 
         FIG. 29  is a cross-sectional side view of an electronic device having shielding structures of the type shown in  FIG. 28  in accordance with an embodiment of the present invention. 
         FIG. 30  is a cross-sectional side view of shielding structures and conductive housing structures showing how the shielding structures may be grounded to conductive housing structures such as conductive housing walls in accordance with an embodiment of the present invention. 
         FIG. 31  is a perspective view of a thin-film-transistor (TFT) layer on which shielding structures have been formed to help minimize radio-frequency interference between the display and wireless circuitry in the device in accordance with an embodiment of the present invention. 
         FIG. 32  is a cross-sectional side view of a conventional display module grounding configuration in a cellular telephone. 
         FIG. 33  is a cross-sectional side view of a display module grounding configuration in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in one or more wireless communications bands. Antenna structures in an electronic device may be used in transmitting and receiving radio-frequency signals. The electronic device may have a display. Shielding structures may be provided along one or more edges of the display to minimize signal interference between the display and the wireless communications circuitry. 
     An illustrative electronic device that contains wireless communications circuitry, a display, and shielding structures that minimize interference between the display and wireless communications circuitry is shown in  FIG. 1 . Device  10  of  FIG. 1  may be a notebook computer, a tablet computer, a computer monitor with an integrated computer, a desktop computer, or other electronic equipment. If desired, electronic device  10  may be a portable device such as a cellular telephone, a media player, a wrist-watch device, a pendant device, an earpiece device, or other compact portable device. 
     As shown in  FIG. 1 , device  10  may have a housing such as housing  12 . Housing  12  may be formed from materials such as plastic, metal, carbon fiber and other fiber composites, ceramic, glass, wood, other materials, or combinations of these materials. Device  10  may be formed using a unibody construction in which some or all of housing  12  is formed from a single piece of material (e.g., a single cast or machined piece of metal, a single piece of molded plastic, etc.) or may be formed from frame structures, housing sidewall structures, and other structures that are assembled together using fasteners, adhesive, and other attachment mechanisms. 
     Device  10  may include components such as buttons, input-output port connectors, ports for removable media, sensors, microphones, speakers, status indicators, and other device components. As shown in  FIG. 1 , for example, device  10  may include buttons such as menu button  16 . Device  10  may also include a speaker port such as speaker port  18  (e.g., to serve as an ear speaker for device  10 ). 
     One or more antennas may be formed in device  10 . The antennas may, for example, be formed in locations such as locations  24  and  26  to provide separation from the conductive elements of display  14 . Antennas may be formed using single band and multiband antenna structures. Examples of communications bands that may be covered by the antennas include cellular telephone bands (e.g., the bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz), satellite navigation bands (e.g., the Global Positioning System band at 1575 MHz), wireless local area network bands such as the IEEE 802.11 (WiFi®) bands at 2.4 GHz and 5 GHz, the Bluetooth band at 2.4 GHz, etc. Examples of antenna configurations that may be used for the antennas in device  10  include monopole antennas, dipole antennas, strip antennas, patch antennas, inverted-F antennas, coil antennas, planar inverted-F antennas, open slot antennas, closed slot antennas, loop antennas, hybrid antennas that include antenna structures of multiple types, or other suitable antenna structures. 
     Device  10  may include one or more displays such as display  14 . Display  14  may be a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, a plasma display, an electronic ink display, etc. A touch sensor may be incorporated into display  14  (i.e., display  14  may be a touch screen). The touch sensor may be an acoustic touch sensor, a resistive touch sensor, a piezoelectric touch sensor, a capacitive touch sensor (e.g., a touch sensor based on an array of indium tin oxide capacitor electrodes), or a touch sensor based on other touch technologies. 
     Display  14  may be covered by a transparent planar conductive member such as a layer of glass or plastic. The cover layer for display  14 , which is sometimes referred to as a cover glass layer or cover glass and which is shown as layer  37  in  FIG. 2 , may extend over substantially all of the front face of device  10 , as shown in  FIG. 1 . The rectangular center portion of the cover glass (surrounded by dashed line  20  in  FIG. 1 ) contains an array of image pixels and is sometimes referred to as the active portion of display  20 . The peripheral outer portion of the cover glass (i.e., rectangular peripheral ring  22  of  FIG. 1 ) does not contain any active image pixels and is sometimes referred to as the inactive portion of display  14 . A patterned opaque masking layer such as a peripheral ring of black ink may be formed under inactive portion  22  to hide interior device components from view by a user. 
     A cross-sectional side view of display  14  taken along the longitudinal axis of device  10  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , black ink  28  may be formed on the interior surface of cover glass  37  under inactive portion  22  of display  14 . In the example of  FIG. 2 , display  14  is a liquid crystal display (LCD) and has a display module (display module  30 ) that is formed from color filter layer  32  and thin-film transistor (TFT) layer  34 . A layer of liquid crystal material (layer  36 ) may be interposed between thin-film-transistor layer  34  and color filter layer  32 . 
     Driver circuitry  38  (e.g., a driver integrated circuit) may receive image data from processing circuitry in device  10  and may produce corresponding control signals for display module  30 . Display module  30  may contain image pixels that contain electrodes. The electrodes may be used to impose an electric field on an associated portion of the liquid crystal material, thereby altering its optical properties and modulating the amount of light that is transmitted through that image pixel. Color filter layer  32  may contain an array of colored filter elements such as red, green, and blue color filter elements to provide display module  30  with the ability to display color images. Thin-film-transistor layer  34  may contain an array of transistors for controlling the application of the electric field to the electrodes. The transistors of the array may be controlled by the control signals from driver circuitry  38 . 
     Substrate materials that may be used for thin-film-transistor layer  34  and color filter layer  32  include glass, ceramic, plastic, etc. If desired, a touch sensor may be incorporated into module  30  to provide display  14  with touch sensitivity. The touch sensor may be formed from an array of transparent indium tin oxide capacitor electrodes in a capacitive touch sensor configuration or may be formed using other touch technologies. Capacitive touch sensor electrodes may be provided on a substrate layer in module  30 , on the underside of cover layer  37 , or on other suitable substrate layers (e.g., a substrate layer formed from glass, ceramic, plastic, etc.). 
     The signals that driver circuit  38  uses to control the image pixels in display module  30  have the potential to lead to undesirable radio-frequency interference. Typical signal frequencies associated with the signals produced by circuit  38  are in the 1-100 kHz range (e.g., 30 kHz). The signals that are output by circuit  38  and associated harmonics can interfere with radio-frequency signals being handled by wireless communications circuitry in device  10 . For example, cellular telephone communications can be disrupted. The potential for undesirable interference can be particularly acute when antennas are mounted within housing  12  in close proximity to display module  30  (e.g., in locations such as locations  24  and  26  of  FIG. 1 ). 
     Drive (control) signals from driver circuitry  38  may include, for example, analog data line signals DL, gate line signals GL, and common voltage signals Vcom. An illustrative image pixel circuit for an LCD pixel in display module  30  is shown in  FIG. 3 . Image pixel circuit  52  of  FIG. 3  may be used to control the state of a single pixel of display module  30 . In a typical display, display module  30  will contain thousands or millions of pixels. 
     As shown in  FIG. 3 , liquid crystal material  36  may be located between respective electrodes  40  and  42 . Electrodes  40  and  42  impose an electric field on liquid crystal material  36 , which controls the polarization properties of material  36  and, in conduction with polarizer layers and other optical films in display module  30 , controls the amount of transmitted light associated with the image pixel. Data line voltage DL on data line  48  may be an analog voltage (e.g., a 0-5V voltage that has one of 256 possible voltage values in an 8-bit system). The magnitude of signal DL may be used to establish a desired grayscale level for the light transmission through liquid crystal pixel  36 . Gate line voltage GL on gate line  46  may be a digital control pulse of about 16 microseconds in width that is used to activate image pixel  52 . Pulses GL may be spaced about 16 ms from each other (i.e., signal GL may contain a train of 16 microsecond pulses each spaced 16 ms from each other). Other pulse widths and pulse spacings may be used if desired. These numerical values are provided as an example. 
     When gate line signal GL in a given pixel goes high, the thin-film transistor in that pixel (i.e., transistor  50 ) is turned on and the signal DL on data line  48  is conveyed to electrode  40 . Electrode  42  is electrically connected to common voltage line (Vcom line)  44 . Lines such as line  44  may be controlled individually or in groups (e.g., one or more Vcom lines in the image array may be shorted together). The voltage signal Vcom on line  44  is generally equal in magnitude and opposite in sign to that of data line signal DL to effectively double the electric field between electrodes  40  and  42 . 
       FIG. 4  is a top view of an illustrative layout that may be used for the signal lines in display module  30 . As shown in  FIG. 4 , the driver circuitry of driver integrated circuit  38  may be coupled to driver circuitry  54  and  56 . The output of driver integrated circuit  38  may include data line signals that contain grayscale information for multiple color channels, such as red, green, and blue channels. Demultiplexing circuitry  54  may demultiplex this data line signal into respective R, G, and B data line signals on respective data lines  48 . Driver circuitry  56  may be used to drive voltage signal Vcom and gate signals GL onto lines  44  and  46 . 
     Driver integrated circuit  38  may be mounted on thin-film-transistor layer  34 , as shown in  FIG. 34 . Some or all of data demultiplexing circuitry  54  and/or driver circuitry  56  may be implemented as part of driver integrated circuit  38  or may be implemented using circuit components fabricated on the thin-film-transistor substrate layer  34 . For example, in configurations in which transistors on thin-film-transistor layer  34  are fabricated using low temperature polysilicon (LIPS) fabrication techniques, the performance of the transistors may be satisfactory for forming both demultiplexing circuitry  54  and Vcom and gate driver circuitry  56  from transistor structures on substrate  34 . In configurations in which amorphous silicon transistor technology is used to form transistors on substrate  34 , it may be desirable to incorporate the circuitry of Vcom and gate drivers  56  into driver integrated circuit  38 , while implementing the circuitry of data line demultiplexer circuitry  54  using amorphous silicon transistors on substrate  34 . An illustrative circuit layout that may be associated with this type of arrangement is shown in  FIG. 5 . 
       FIG. 6  is a circuit diagram showing circuitry that may be used to implement circuits of the type shown in  FIGS. 4 and 5 . In the  FIG. 6  example, Vcom and gate line driver circuitry  56  has been implemented using transistors that are separate from driver integrated circuit  38 . This is merely illustrative. If desired, circuitry  56  may be implemented within driver integrated circuit  38 . 
     As shown in the example of  FIG. 6 , display demultiplexer control circuitry  58  in driver integrated circuit  38  may be used to supply data line demultiplexer control signals R, G, and B (corresponding to red, green, and blue channels in this example) to the gates GT of demultiplexer transistors  60 . Drivers  62  may produce data line output signals SO 1 , S 02 , . . . (sometimes referred to as source output signals) on data line paths  64 . The source output signals contain analog pixel data for image pixels of all three colors (i.e., red, blue, and green). The control signals that are applied to the gates of demultiplexing transistors  60  turn transistors  60  on and off in a pattern that routes red channel information from the source output signals to red data lines RGL, that routes green channel information from the source output signals to green data lines GDL, and that routes blue channel information from the source output signals to blue data lines BDL. 
     Optional loading circuits  66  may be implemented using one or more discrete components (e.g., capacitors, inductors, and resistors) that are interposed within lines  54  or may be implemented in a distributed fashion using some or all of the structures that form lines  54 . Optional loading circuits  66  and/or circuitry in integrated circuit (e.g., circuit  58 ) and/or circuit  56  may be used to control the shape of the gate signals GL and demultiplexing control signals R, G, and S. Signal shaping techniques such as these may be used to smooth display control signal pulses such as the gate line and demultiplexer control signal pulses and thereby reduce harmonic signal production and radio-frequency interference. 
       FIG. 7  is a graph of a typical source output signal SO. As shown in  FIG. 7 , signal SO contains red channel information (the magnitude of signal SO at point RD), green channel information (the magnitude of signal SO at point GN), and blue channel information (the magnitude of signal SO at point BL). Demultiplexer control signals R ( FIG. 8 ), G ( FIG. 9 ), and B ( FIG. 10 ) may be formed from pulses that lie within the pulse window formed by gate line signal GL ( FIG. 11 ). When both the demultiplexing control signal and the gate line signal are being asserted, the relevant portion of the source output signal SO is routed to electrode  40  ( FIG. 3 ). For example, when signal R ( FIG. 8 ) and gate line signal GL ( FIG. 11 ) are both high, the demultiplexing transistor that is controlled by signal R is turned on and transistor  50  in the image pixel cell is turned on, so that signal RD is applied to electrode  40 . This electrode is associated with a red color filter in a red pixel. Similarly, the G demultiplexing control signal works with gate line signal GL to apply signal GN to the electrode in a green pixel and the B demultiplexing control signal works with the gate line signal GL to apply signal BL to the electrode in a blue pixel. 
     Conventionally, signals R, G, B, and GL have shapes that are substantially rectangular. However, the sharp transitions at the rising and falling edges of this type of display control signal can lead to undesirable frequency harmonics and may create unsatisfactory radio-frequency signal interference with wireless circuitry. 
     Signal harmonics and interference may, if desired, be reduced by shaping the R, G, B, and GL pulses. For example, the R, G, B, and GL signals may be smoothed so that they exhibit more gradual rising and falling edges (e.g., as in a sinusoidal signal). 
       FIG. 12  shows an illustrative loading circuit that may be used within a demultiplexer control signal path (e.g., one of the paths for the R, G, and B signals in  FIG. 16 ) and/or the gate line driver path (e.g., path  46  of  FIG. 6 ). As shown in  FIG. 12 , loading circuit  66  may include a resistance (resistor R) and capacitance (capacitor C). If desired, other loading circuit designs may be used (e.g., loading circuits that include inductors, etc.). The arrangement of  FIG. 12  is merely illustrative. 
     Resistor R may be implemented using one or more discrete resistors (as an example). Capacitor C may be implemented using one or more discrete capacitors. If desired, there may be multiple loading circuits (i.e., multiple circuits such as circuit  66  of  FIG. 12 ) interposed within a given control line (i.e., within one of multiplexer control lines  54  of  FIG. 6  or within one of gate lines  46  of  FIG. 6 ). 
     Resistors, capacitors, and inductors for loading circuit  66  may also be implemented using distributed structures. Resistor R may, for example, be implemented by narrowing the width and/or thickness of a control line sufficiently that the resistance of the control line itself forms resistor R. In this type of arrangement, resistor R may be modeled as being formed from numerous series-connected resistors R′, as shown in  FIG. 14 . Similarly, capacitance C of loading circuit  66  may be implemented by placing the conductive trace that forms the control line path adjacent to a ground plane or other structure that allows the line itself to form a distributed capacitor (illustrated as capacitors C′ in the example of  FIG. 14 ). 
     When loading circuitry such as circuitry  66  of  FIGS. 12 ,  13 , and  14  is present within the display module control lines, the signals that are carried on the control lines tend to exhibit reduced rise and fall times (i.e., the control pulses tend to be smoothed out due to R-C effects) and therefore exhibit noise with reduced higher-order frequency harmonics. Control pulse smoothing may also be implemented by the display driver circuitry (e.g., circuitry in display demultiplexer control circuitry  58  that generates signals R, G, and B), control circuitry in drivers  56  (e.g., circuitry that generates gate line signals GL), etc. The pulse shaping circuitry may generate smoothed control pulses such as smoothed pulse  68  of  FIG. 15 . As shown in  FIG. 15 , pulse  68  may have more gradual rising and falling edges than conventional rectangular control pulse  70 . Pulse  68  may have a sinusoidal shape or nearly sinusoidal shape or other pulse shape that is smoothed relative to conventional rectangular pulse  70 . Smoothed (gradual rising and falling edge) pulses such as pulse  68  of  FIG. 15  may be used for signals R, G, B, and DL in displays having circuitry of the type shown in  FIG. 6  (as an example). 
       FIG. 16  shows a typical noise spectrum of the type that is produced when driving conventional (rectangular) pulses into a display module. As shown in  FIG. 16 , there are noise components  72  associated with the control pulses. Noise components  72  may include a 30 kHz fundamental noise component, a 60 kHz second harmonic noise component, and numerous additional higher-order harmonics. Collectively, noise components  72  lead to a relatively broad spectrum of display-generated noise, as shown by noise spectrum curve  74 . 
     When smoothed pulses such as pulses  68  are used in the display control circuitry of  FIG. 6 , the sharp rising and falling edges of the control pulses are absent. As a result, higher-order frequency harmonics are substantially reduced. This is illustrated by the relatively small number of illustrative noise components  78  and the small size of noise spectrum curve  76  of  FIG. 17 . 
     The potential for interference between display module  30  and wireless circuitry in device  10  may be exacerbated in configurations where antenna structures in device  10  are located adjacent to display module  30 . As shown in  FIG. 18 , for example, antenna(s)  80  may be located in regions such as end regions  24  and  26  in device  10 , adjacent to the ends of display module  30 . When control signals are applied to the image pixels in display module  30  by driver integrated circuit  38  and driver circuitry such as demultiplexer  54  and drivers  56 , noise signals (e.g., noise signals of the type shown in  FIG. 16  or noise signals of the type shown in  FIG. 17 ) may be coupled into antenna(s)  80 . If care is not taken, the operation of the wireless circuitry such as cellular telephone circuitry, wireless local area network circuitry, or other wireless communications circuitry with which antenna(s)  80  are used may be adversely affected. 
     If desired, antennas may be formed using parts of housing  12 . As shown in  FIG. 19 , for example, antenna  80  may be formed in lower region  26  of housing  12 . Housing  12  may contain a peripheral conductive member such as peripheral band member  12 B that runs around the periphery of device  10 . Member  12 B may, for example, form a bezel for display  14  or may form vertical housing sidewalls for housing  12 . Planar member  12 M (sometimes referred to as a planar housing member, housing plate, or midplate) may be connected to the sides of housing band  12 B (i.e., on the left and right in the orientation of  FIG. 19 ). Gap  94  may be formed between the lower edge of housing plate  12 M and peripheral conductive member  12 B. Gap  96  may be formed between the upper edge of housing plate  12 M and peripheral conductive member  12 B. Gaps such as gaps  94  and  96  may be filled with air and other dielectrics and may be used in forming antenna structures  80 . For example, gaps  94  and  96  may be used in forming slot antenna structures, hybrid antenna structures that include slot antenna structures, loop antennas, or other antenna structures. Gap  96  may be used in forming an antenna in region  24 . Gap  94  may be used in forming an antenna in region  26 . 
     As shown in  FIG. 19 , antenna  80  in region  26  may include a gap such as gap  82  in peripheral conductive member  12 B. Gap  82  may be formed from plastic or other dielectric material. There may be one or more gaps such as gap  82  in the portion of peripheral conductive member  12 B that forms each antenna. A radio-frequency transceiver (sometimes referred to as a radio) such as transceiver  84  may be used to feed each antenna. Transceiver  84  may be used to handle any suitable communications bands of interest (e.g., cellular telephone bands, wireless local area network bands, etc.). Device  10  may contain one or more transmission lines. For example, a transmission line such as transmission line  86  may be used to couple transceiver  84  to an antenna feed for antenna  80  of  FIG. 19 . 
     In the example of  FIG. 19 , midplate  12 M is formed from a conductive material such as metal and forms a ground element. Antenna  80  has an antenna feed that includes positive antenna feed terminal  90  that is connected to peripheral conductive member  12 B and ground antenna feed terminal  88  that is connected to midplate  12 M. Midplate  12 M and conductive peripheral member  12 B may be shorted to each other (e.g., using welds, fasteners, etc.). Transmission line  86  may be a microstrip transmission line, a stripline transmission line, a coaxial cable, etc. Transmission line  86  may have a ground conductor such as an outer braid conductor on a coaxial cable that is connected to ground terminal  88  and may have a positive signal conductor such as a coaxial cable center conductor (conductor  92  of  FIG. 19 ) that is connected to positive antenna feed terminal  90 . Matching networks, other types of antenna structures, and other feed arrangements may be used if desired. The illustrative structures for feeding antenna  80  in  FIG. 19  are merely illustrative. 
     When a display module such as display module  30  of  FIG. 2  is mounted within device  10  of  FIG. 19 , display module  30  and active display region  20  may overlap midplate  12 M without protruding substantially into gaps  96  and  94  (as an example). In this type of configuration, gaps  94  and  96  may be relatively unaffected by the conductive lines and other conductive structures in display module  30 . Nevertheless, due to the close proximity between display module  30  and antennas  80 , there is a potential for interference. 
     To prevent interference from display module  30  from interfering with the operation of antennas  80 , one or more strips of conductive shielding material may be provided along one or more of the edges of the display. The shielding structures may be formed from metals or other conductive materials and may be formed on display module structures, cover glass  37 , housing structures, or other suitable structures within device  10 . 
     In some configurations of device  10 , device  10  may include cellular telephone antenna structures in lower region  26 . Region  24  may be used for wireless local area network antenna structures, cellular telephone antennas, and other antenna structures. The cellular telephone antenna structures in region  26  and associated cellular telephone transceiver circuitry may be sensitive to interference. In this type of arrangement, it may be desirable to form a shielding structure from a strip of conductor that is located along the lower edge of display active region  20 . As shown in  FIG. 20 , for example, shielding structure  98  may have an elongated shape with a longitudinal axis (axis  100 ) that runs perpendicular to longitudinal axis  102  of device  10  (as an example). In the arrangement of  FIG. 20 , shielding structure  98  is grounded and is interposed between the lower portion of display  20  (display module  30 ) and antenna(s)  80  in region  26 . Shielding structure  98  may serve to block electromagnetic signals from display  20  and may therefore help to block radio-frequency noise signals from the display that might otherwise be received by the antenna in region  26  and associated cellular telephone circuitry. Shielding structure  98  may be grounded by electrically connecting shielding structure  98  to a ground element such as a ground plane formed by midplate  12 M ( FIG. 19 ). 
     Another illustrative shielding arrangement is shown in  FIG. 21 . In the configuration of  FIG. 21 , shielding structure  98  has three segments. Left and right shielding segments L and R respectively run parallel to longitudinal axis  102  of device  10  and module  30 . Bottom segment B runs parallel to axis  100  and perpendicular to axis  102 . Shielding structure  98  may be grounded by connecting shielding structure  98  to a grounded conductive housing structure or other ground plane element using a conductive path. Shielding structure  98  may be configured so as to surround three sides of active region  20  of display module  30 . 
     A U-shaped shielding structure of the type shown in  FIG. 21  may be satisfactory for shielding antenna structure  80  in lower housing region  26  of device  10  from interference produced by display module  30 . The omission of an upper segment of shielding structure  98  interposed between display module  30  and antenna structures  80  in region  24  may allow some radio-frequency noise from display module  30  to reach these antenna structures, but may help reduce capacitive coupling between display module  30  and antenna structures  80  in lower region  26  and therefore may help improve isolation between display module  30  and antenna structures  80  in lower region  26 . The amount of noise that is coupled to antenna structures  80  in region  24  may be acceptable, particularly when antenna structures  80  operate at frequencies that are relatively unaffected by lower frequency noise (e.g., when antenna structures  80  in region  24  are generally operated in wireless local area network bands at 2.4 GHz and 5 GHz, etc.). 
     If desired, shielding structures  98  may be configured to surround all or substantially all four sides of the display in device  10 . For example, shielding structure  98  may be formed in the shape of a rectangular ring that surrounds active region  20  of display module  30  as shown in the example of  FIG. 22 . In this type of configuration, shielding structures  98  may be provided with an upper segment such as conductive segment T that is connected to left segment L and right segment R. Lower segment B may be connected between left and right segments L and R. As shown in  FIG. 22 , segment T of shielding structure  98  may be interposed between antenna structures  80  in upper region  24  of device  10 , which may help reduce interference between display module  30  and antenna structures  80  in upper region  24 . 
     Other configurations may be used for shielding structure  98  if desired. For example, shielding structure  98  may be formed by a rectangular ring of conductor that surrounds active region  20  of module  30 , but that has one or more gaps. Conductive structures for forming shielding structure  98  may include elemental metals, metal alloys, and other conductive materials. The width of shielding structure  98  may be, for example, less than 2 mm, less than 1 mm, less than 0.5 mm, in the range of 0.3 to 1.3 mm, in the range of 0.5 to 1 mm, etc. Shielding structures  98  may be formed by screen printing, painting, pad printing, ink jet printing, physical vapor deposition, chemical vapor deposition, photolithography, electroplating, etc. 
     Some or all of the material that makes up shielding structure  98  may be formed on or adjacent to cover glass layer  37  or housing structures in housing  12 . As shown in  FIG. 23 , for example, shielding structure  98  may be formed on or adjacent to opaque masking layer  28  (e.g., black ink) on cover glass layer  38 . Shielding structure  98  may, for example, be formed from patterned metal traces that are formed on the underside of cover glass  37  (e.g., by depositing and patterning shielding structures  98  on cover glass  37 ). If desired, shielding structure  98  may be formed on a housing structure such as midplate structure  12 M of  FIG. 23 . Midplate  12 M may be formed from metal and may be welded to conductive housing sidewall structures  12 B as described in connection with  FIG. 19 . Midplate  12 M may form part of a ground element in device  10 . As shown in  FIG. 23 , shielding structure  98  may be formed on layer  106  on a protrusion such as portion  104  of midplate  12 M. Layer  106  may be formed from a material such as plastic or other dielectric material (as an example). Adhesive  108  may be interposed between layer  106  and cover glass  37  to help hold the structures of  FIG. 23  together when assembled within device  10 . Shielding structure  98  of  FIG. 23  may be implemented as a single strip of conductor (as shown in  FIG. 20 ), as a U-shaped shielding conductor (as shown in  FIG. 21 ), as a rectangular ring of conductor (as shown in  FIG. 22 ), or using other suitable layouts. 
     Shielding structures such a shielding structure  98  of  FIG. 23  may be shorted to ground by electrically connecting shielding structure  98  to conductive housing structures such as midplate  12 M, housing walls in housing  12  (e.g., walls formed from a band shaped peripheral conductive member that runs around the periphery of device  10 , a conductive bezel that runs around the periphery of device  10  along the front of device  10 , etc.).  FIG. 24  is a cross-sectional side view of a portion of shielding structure  98  showing how shielding structure  98  may have a shape that forms a connection with conductive housing portion  12 S. Portion  12 S may be a band shaped peripheral conductive member that runs around the periphery of device  10 , other conductive sidewall portions of housing  12 , a conductive bezel that runs around the periphery of device  10  along the front of device  10 , or other suitable conductive portion of housing  12 . Welds, conductive adhesive, conductive fasteners, conductive springs, conductive foam, wires, portions of flex circuits, and other conductive attachment mechanisms may be used to electrically (and, if desired, mechanically) attach shielding structure  98  to ground (e.g., to conductive portions of housing  12 ). An illustrative configuration in which metal spring  110  and resilient conductive material  112  (e.g., conductive foam, conductive adhesive, etc.) are being used to electrically connect shielding structure  98  to a conductive ground structure such as housing member  12 M is shown in the cross-sectional diagram of  FIG. 25 . 
     In the illustrative configuration of  FIG. 26 , shielding structure  98  has been formed from a metal or other conductive material that has been wrapped around the edge of display module  30  in a way that covers both the upper (front) and lower (rear) surfaces of display module  30  and the vertical side edges of display module  30 . Shielding structure  98  of  FIG. 23  may be implemented as a single strip of conductor (as shown in  FIG. 20 ), as a U-shaped shielding conductor (as shown in  FIG. 21 ), as a rectangular ring of conductor (as shown in  FIG. 22 ), or using other suitable layouts. Materials such as copper tape, other metal tapes, or other conductive materials may be used in forming shielding structures such as shielding structure  98  of  FIG. 26 . When forming a three-sided structure of the type shown in  FIG. 21  (as an example), conductive tape may be wrapped over the edges of display module  30  on the left, right, and lower portions of the display. A conductive path such as a conductive path formed by structure  112  may be used to electrically connect shielding structure  98  to ground (e.g., midplate  12 M and/or a sidewall in housing  12 ). Structure  112  may be formed from a layer of conductive foam, a layer of conductive adhesive, a conductive spring, etc. 
     A top view of a conventional display module showing how a flexible printed circuit (“flex circuit”) may be pigtailed to the display module is shown in  FIG. 27 . Flex circuit  114  may be used to carry signals between display module  126  and a logic board. Flex circuits may be formed from patterned conductive traces on flexible sheets of substrate such as polyimide sheets. As shown in  FIG. 27 , display module  126  may have a rectangular substrate  124  on which display driver integrated circuit  122  is mounted. Flex circuit  114  may have portions  116  and  118 . The outermost layer of portion  116  (out of the page in the orientation of  FIG. 27 ) is formed from conductive flex circuit traces. In portion  118 , copper tape may be used to provide supplemental signal shielding by covering driver integrated circuit  122 . 
     Structures of the type shown in  FIG. 27  generally do not provide desired amounts of signal shielding (e.g., for antenna structures located adjacent to end  128  of substrate  124  along the edge of substrate  124  opposing driver integrated circuit  122 ). To address this shortcoming, display module  30  may be provided with shielding structure segments such as shielding structure segments  98 B between display active region  20  of display module  30  and antenna structures  80  in region  26  of device  10 , as shown in  FIG. 28 . Display module  30  of  FIG. 28  may have a flex circuit such as flex circuit  130 . Flex circuit  130  may contain patterned conductive traces that form signal lines. These signal lines may be used to route signals to display driver integrated circuit  38  from circuitry on a printed circuit board in device  10 . 
     As shown in  FIG. 28 , flex circuit  130  may have pigtail portion  132 . The outermost layer of flex circuit  130  in region  132  may be formed from an exposed conductive flex circuit trace (e.g., a ground trace). In region  134 , a copper tape layer or other structure may be electrically connected to the ground trace and may help shield driver integrated circuit  138  on thin-film-transistor substrate  34 . 
     Shielding structure  98  may surround all of part of active region  20  of display module  30 . For example, conductive paths  136  may be used to electrically connect the ground portion of flex circuit  130  and the overlying copper in region  134  to left shielding structure segment  98 L and right shielding structure segment  98 R. Lower shielding structure  98 B may run along the lower edge of display module  30  between active region  20  and antenna structures  80  in region  26 . Shielding structure segments  98 R,  98 L, and  98 B (and, if desired, connecting paths  136  and conductive layers covering display driver integrated circuit  38  in region  134 ) may be formed from copper tape, other metal structures, patterned traces deposited on thin film transistor substrate layer  34 , or other conductive materials. The flex circuit in region  132  may be folded to help fit flex circuit  130  within housing  12  of device  10 . End  138  of flex circuit  130  may be connected to circuitry on a printed circuit board (as an example). The outermost conductive layer on flex circuit  130  may be used in grounding shielding structure  98 . 
     A cross-sectional side view showing how flex circuit  130  may be routed between display module  30  and printed circuit board  144  is shown in  FIG. 29 . As shown in  FIG. 29 , flex circuit  130  may be connected to traces  142  on thin-film-transistor layer  34 . Traces  142  may be used in interconnecting signal paths on flex circuit  130  to driver circuitry  38 . Encapsulant  140  may be used to cover circuitry  38 . 
     Shielding structure  98  may be formed in a rectangular ring shape around active portion  20  of display module  30 , in a U-shape, in a segment that is interposed between antenna structures  80  in region  26  and active portion  20  of display module  30 , etc. The conductive structures that overlap display driver  38  (shown as conductive structures  98 U in the example of  FIG. 29 ) may be formed from copper tape that shields driver circuitry  38  or other materials and may be connected to shielding structures  98  that surround other portions of active display region  20  using conducive paths such as paths  136  of  FIG. 28 . 
     Flex circuit  130  may be routed to printed circuit board substrate  144  through opening  148  (e.g., a recess) in midplate  12 M. Integrated circuits and other components  146  may be mounted on printed circuit board  144 . Patterned traces on flex circuit  130  may be used to form signal paths that convey data signals between the circuitry on board  144  and display module  30 . A ground trace (e.g., the outermost layer of flex circuit  130 ) may be used in grounding structure  98 U and shielding structures  98  such as the shielding structure shown on the left hand portion of display module  30  in the example of  FIG. 29 . Conductive structures such as structures  150  may be used to electrically connect the ground trace on the outermost surface of flex circuit  130  to ground elements within device  10  such as conductive housing member  12 M and conductive housing sidewalls  12 S (i.e., the grounding of shielding structures  98  may be handled exclusively or at least partly using one or more ground traces on flex circuit  130 ). Rear plate  12 R of housing  12  in device  10  may be formed from glass, plastic, metal, etc. Structures  150  may be formed from conductive adhesive, conductive foam, conductive springs, etc. 
     Another illustrative arrangement for shielding structures  98  is shown in  FIG. 30 . As shown in  FIG. 30 , shielding structures  98  may wrap around one or more of the edges of display module  30 . Shielding structure  98  may, for example, cover the upper (front) and lower (rear) surfaces of display module  30 , as shown by solid portion  152  of structure  98 . Dashed line portion  154  of shielding structure  98  shows how shielding structure  98  may have portions that run vertically (i.e., parallel to vertical housing sidewalls  12 S). Vertical portions  154  may, for example, be formed along the right and left edges of display module  30  and device  10 . Screws such as screw  156  or other conductive attachment structures may be used to electrically connect shielding structure  98  to conductive housing member  12 S (e.g., a peripheral conductive housing member that runs around the periphery of device  10 ). Midplate  12 M may have a recess or other opening that allows portion  154  to extend downwards from display module  30  along the side of optional metal housing structure  156 . Structure  156  may be a metal frame or a metal bracket that is electrically and mechanically connected to conductive housing member  12 S, may be a portion of housing structure  12 S, may be other grounded conductive structures in device  10 , etc. As illustrated by touch sensor electrode array  158 , display  14  in device  10  may be a touch screen display. 
       FIG. 31  is a perspective view of thin-film transistor substrate  34  showing how shielding structure  98  may be formed from conductive traces such as patterned metal traces on thin-film transistor substrate  34 . Shielding structure  98  may be formed in a rectangular ring shape around active portion  20  of display module  30 , in a U-shape, in a segment that is interposed between antenna structures  80  in region  26  and active portion  20  of display module  30 , etc. Shielding structure  98  may, for example, have left trace segment  98 L (e.g., a metal line that runs parallel to the left edge of active region  20 ), right trace segment  98 R (e.g., a metal line that runs parallel to the right edge of active region  20 ), and lower trace segment  98 B (e.g., a metal line that is shorted to segments  98 L and  98 R and that runs parallel to the lower edge of display module  30  at the opposite end of active region  20  from display driver integrated circuit  38 ). Structures  98  may be formed from metal or other suitable conductive materials. 
     To avoid undue complexity during fabrication, it may be desirable to form the traces of shielding structure  98  from the same material that is being used to form other conductive structures in display module  30  such as a metal or metal alloy that is being used to form the circuitry of demultiplexer  54 , Vcom (common voltage) and gate driver circuitry  56 , and the signal lines in active region  20 . Examples of materials that may be used in this type of display circuitry include NiAl, and TiAlTi, and MoW (e.g., to satisfy requirements such as being able to form satisfactory ohmic contacts with polysilicon transistors, being lift-off compatible, etc.), so with one suitable arrangement structures  98  may be formed form NiAl, TiAlTi, and/or MoW (i.e., structures  98  may be formed at least partly using the same material that is used in forming some or all of the gate lines, common voltage lines, and data lines in display module  30 ). Indium tin oxide (ITO) may sometimes be used to form Vcom lines and may, if desired, be used in forming some or all of shielding structures  98 . Other illustrative conductive materials that may be used for forming shielding structures  98  include silver paint, nickel paint, printed conductors, etc. 
     If desired, the impact of display noise on antenna performance may be mitigated by disrupting the ground path between the display and system ground that is present in conventional cellular telephones. A cross-sectional side view of a portion of a conventional cellular telephone is shown in  FIG. 32 . As shown in  FIG. 32 , display module  234  is connected to printed circuit board  244  via flex circuit  230 . Flex circuit  230  is a three-layer flex circuit that contains signal traces  259  in a central layer and contains outer layer traces  255  and  257  on opposing outer flex circuit layers. Traces  255  and  257  form ground paths between printed circuit board  244  and display module  234 . Board-to-board connector  273  connects flex circuit  230  to printed circuit board  244 . 
     Electrical components  246  are mounted on printed circuit board  244  and are covered by electromagnetic shield  247 . Shield  251  is used to cover electrical components (capacitors)  253  on flex circuit  230 . Spring  249  forms a short circuit path between shield  251  and shield  247 . 
     Metal housing midplate  212  forms system ground (shown schematically as ground  267  in  FIG. 32 ). Vias  263  in flex circuit  230  are used to electrically connect ground trace  257  to ground trace  255 . Vias  263  are formed in the region of flex circuit  230  that overlaps conductive adhesive  263 . Conductive adhesive  265  electrically connects ground trace  255  to midplate  212 . Traces  255  and  257  are grounded to display module  234  at end  273  of flex circuit  230 . 
     During operation of display  234 , noise signals are able to flow between display module  234  and printed circuit board  244  via ground trace  257 , shield  251 , spring  249 , and shield  247 . This ground path is depicted as ground path  269  in  FIG. 32 . Another ground path that is formed using the conventional arrangement of  FIG. 32  is depicted as ground path  271  in  FIG. 32 . Path  271  allows noise signals to pass from display module  234  directly to system ground  267  (e.g., through trace  257 , vias  263 , and trace  255 ). The presence of vias  263  in the region of flex circuit  230  that overlaps conductive adhesive  265  and the presence of ground trace  255  in region  275  of flex circuit  230  help form path  271 . Path  271 , however, serves as a source of undesired coupling between the display driver circuitry of module  234  and antenna structures in the cellular telephone of  FIG. 32 , because system ground  267  (e.g., midplate  212 ) is used in forming antenna ground for the antenna structures. 
     Arrangements of the type shown in  FIG. 33  do not form undesired path  271  and may therefore help mitigate the effects of display noise on antenna performance. 
     The structures of  FIG. 33  may be formed in a device such as device  10  of  FIG. 1 . As shown in  FIG. 33 , printed circuit board  144  (e.g., a main logic board) may be connected to flex circuit  130  using a connector such as board-to-board connector  308 . Flex circuit  130  may have multiple layers. For example, flex circuit  130  may have two layers, three layers, or more than three layers. In the illustrative configuration shown in  FIG. 33 , flex circuit  130  has three layers. Inner layer  159  may be used in forming signal traces. Outer layers  155  and  157  may be used for signal traces (if desired) and may be used in forming ground paths. When forming ground paths, most or all of the outermost surfaces of flex circuit  130  may be occupied by ground traces  155  and  157 . 
     Path  155  may be shorted to path  157  using vias  304  (e.g., vias in the vicinity of board-to-board connector  308  and at end  310  of flex circuit  130 ). Region  302  (i.e., the region of flex circuit  130  that overlaps conductive adhesive  165 ) of flex circuit  130  is preferably devoid of vias. There is also preferably a gap in ground trace  155  in region  300  (i.e., there is no metal for ground trace  155  in region  300  of flex circuit  130 , so gap  300  forms an open circuit between traces such as trace  306  at end  310  of flex circuit  130  at display module  30  and system ground  167 ). 
     Because region  302  is via free and because ground trace  155  is missing in region  300 , there is no direct ground path between display module  30  and system ground  167  (metal housing midplate structure  12 M). Ground trace  155  may still be used to ground printed circuit board  144  to system ground  12 M using conductive adhesive  165 , but there is no direct coupling between the potentially noisy ground in display module  30  and conductive housing structure  12 M. Housing structure  12 M may be used in forming antenna ground for antenna structures  80  in device  10  (as shown in  FIG. 33 ), so the absence a conventional direct ground path between display module  30  and system ground  167  may help reduce interference between display module  30  and antenna structures  80 . 
     As shown in  FIG. 33 , path  169  may be used to help ground display module  30  to printed circuit board  144 . Printed circuit board  144  may have components  146  (e.g., integrated circuits, etc.) that are shielded using electromagnetic (radio-frequency) shield  147 . Shield  147  may be connected to shield  151  using spring  149  or other conductive structures. Shield  151  may be used to shield components  153  such as capacitors on flex circuit  130 . Shield  151  may be electrically connected to ground trace  157 , so signals in path  169  may flow along trace  157 , shield  151 , conductive structures  149 , and shield  147 . Path  169  does not flow directly to system ground  167 , so noise from display module  30  is not strongly coupled to antenna structures  80 . Arrangements of the type shown in  FIG. 33  may be used in conjunction with the interference-reducing shielding structures of device  10  to help further reduce interference. 
     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: 20101006
Publication Date: 20131112
Grant Date: 20131112
Priority Date: 20101006
Inventors: KIM MOON
JAMSHIDI ROUDBARI ABBAS
YU QISHAN
YAO WEI
MULLINS SCOTT
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B15/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/0266", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/0266", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B15/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 45924966