Abstract:
An apparatus comprising a first substrate, a second substrate, and one or more embedded devices. A lower surface of the first substrate generally has disposed thereon a plurality of first lines comprising a thin-film conductive material. An upper surface of the second substrate generally has disposed thereon a plurality of second lines comprising the thin-film conductive material. The plurality of second lines is generally arranged orthogonally to the plurality of first lines. The lower surface of first substrate generally faces the upper surface of the second substrate and the substrates are generally separated by a predefined distance. The one or more embedded devices are generally coupled between one or more of the first lines and one or more of the second lines. The embedded devices are generally configured to temporarily electrically connect the respective lines to form a radiating structure during an RF operation.

Description:
FIELD OF THE INVENTION 
     The invention relates to mobile communications generally and, more particularly, to a method and/or apparatus for implementing a transitory touchscreen antenna structure. 
     BACKGROUND OF THE INVENTION 
     Resistive touchscreens and touchscreen overlays are used to provide touch-sensitive computer displays. Conventional resistive touchscreens and touchscreen overlays are composed of two flexible sheets coated with a resistive material such as indium tin oxide (ITO) and separated by an air gap or microdots. Conventional resistive touchscreens typically have high resolution (e.g., 4096×4096 DPI or higher), providing accurate touch control. There are two different types of resistive touchscreens, analogue and matrix (or digital). 
     The analogue type of resistive touchscreens consists of transparent electrodes without any patterning facing each other. During operation of a four-wire analogue touchscreen, a uniform, unidirectional voltage gradient is applied to the first sheet. When the two sheets are pressed together, the second sheet measures the voltage as distance along the first sheet, providing the X coordinate. When this contact coordinate has been acquired, the voltage gradient is applied to the second sheet to ascertain the Y coordinate. These operations occur within a few milliseconds, registering the exact touch location as contact is made. 
     The matrix (or digital) type of resistive touchscreen has two substrates such as glass or plastic facing each other. Each substrate is coated with a resistive material such as indium tin oxide (ITO). The ITO coating on each substrate is patterned as striped electrodes. The striped electrodes are patterned as horizontal and vertical lines that, when pushed together, register the precise location of the touch. 
     Resistive touchscreens and overlays are commonly used in portable devices such as cellular telephones, tablets, etc. because they are inexpensive and generally available. Portable devices generally include support for wireless communication. Wireless communication generally is provided using radio frequency (RF) links. Radio frequency (RF) communication support requires some sort of antenna (or radiating structure) be included in the portable devices, which increases the number of components and the cost. 
     It would be desirable to implement a transitory touchscreen antenna structure. 
     SUMMARY OF THE INVENTION 
     The invention concerns an apparatus comprising a first substrate, a second substrate, and one or more embedded devices. A lower surface of the first substrate generally has disposed thereon a plurality of first lines comprising thin-film conductive material. An upper surface of the second substrate generally has disposed thereon a plurality of second lines comprising thin-film conductive material. The plurality of second lines is generally arranged orthogonally to the plurality of first lines. The lower surface of first substrate generally faces the upper surface of the second substrate and the substrates are generally separated by a predefined distance. The one or more embedded devices are generally coupled between one or more of the first lines and one or more of the second lines. The embedded devices are generally configured to temporarily electrically connect the respective lines to form a radiating structure during an RF operation. 
     The objects, features and advantages of the invention include providing a transitory touchscreen antenna structure that may (i) be implemented using embedded diodes in a digital resistive touchscreen, (ii) allow an antenna (or radiating structure) that is assembled during periods of RF operations and otherwise dis-assembled, and/or (iii) form a radiating element (or structure) from conductive lines on two indium tin oxide layers of a matrix resistive touchscreen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, features and advantages of the invention will be apparent from the following detailed description and the appended claims and drawings in which: 
         FIG. 1  is a diagram illustrating layers of a matrix resistive touchscreen in accordance with an embodiment of the invention; 
         FIG. 2  is a diagram illustrating an example placement of diodes in accordance with an embodiment of the invention; 
         FIG. 3  is a diagram illustrating a cross-section of the matrix resistive touchscreen of  FIG. 2  along the line A-A′; 
         FIG. 4  is a diagram illustrating an example antenna formed when the diodes of  FIG. 2  are forward biased; 
         FIG. 5  is a diagram illustrating an example circuit allowing an RF source to be connected to a number of antenna structures; 
         FIG. 6  is a diagram illustrating another example of a circuit allowing connections between multiple RF sources and antenna structures; and 
         FIG. 7  is a flow diagram illustrating an example broadcast operation in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a diagram is shown illustrating various layers of a touchscreen  100  in accordance with an embodiment of the invention. In one example, the touchscreen  100  may include a first substrate  102 , a first conductive layer  104 , an insulating (or separating) layer  106 , a second conductive layer  108 , a second substrate  110 , and a display layer  112 . The first substrate  102  may comprise a flexible optical grade plastic (e.g., polyethylene terephthalate (PET), polyester, etc.). The first conductive layer  104  may comprise a first circuit layer having a transparent thin-film conducting material (e.g., indium tin oxide (ITO), indium zinc oxide (IZO), etc.). The transparent thin-film conducting material may be deposited (e.g., sputtered, etc.) on an underside (lower surface) of the first substrate  102 . The transparent thin-film conducting material of the first conductive layer  104  may be patterned (e.g., etched) to form a plurality of conductive lines (or electrodes) that may be aligned with a first (e.g., horizontal) axis. 
     The insulating (or separating) layer  106  may comprise, for example, an air gap, an array of spacer (separator) dots, an array of dielectric dots, or some other way of maintaining a predefined distance between the lower surface of the first substrate  102  and an upper surface of the second substrate  110  while no pressure is being applied to the touchscreen. The predefined distance is generally selected to prevent unwanted and/or accidental contacts between the first conductive layer  104  and the second conductive layer  108  deposited on the upper surface of the second substrate  110 . In one example, the separation provided by the insulating layer  106  may range from 0.002 inch to 0.010 inch. The separating layer  106  may include a number of openings (or spaces) through which the layers  104  and  108  may make contact with each other when pressure (e.g., from a finger, stylus, etc.) is applied. A number of the openings may also be configured to allow semiconductor devices (e.g., diodes, etc.) embedded in one or both of the layers  104  and  108 , or placed between the layers  104  and  108  during assembly, to make contact with the opposing layers  108  and  104 , respectively. 
     The layer  108  may comprise a second circuit layer having a transparent thin-film conducting material (e.g., indium tin oxide (ITO), indium zinc oxide (IZO), etc.). The transparent thin-film conducting material may be deposited (e.g., sputtered, etc.) on the upper surface (or upperside) of the second substrate  110 . The transparent thin-film conducting material of the layer  108  may be patterned (e.g., etched) to form a plurality of conductive lines (electrodes) that may be aligned with a second (e.g., vertical) axis. The conductive lines of the layer  104  are generally orthogonal to the conductive lines of the layer  108  (e.g., rows and columns). The second substrate  110  generally comprises a stable support (backing) material (e.g., glass, acrylic, etc.). The layer  112  generally implements a display (e.g., LCD, LED, etc.). The layers  102 - 110  are generally held together and sealed with a gasket adhesive, which isolates the touchscreen from the external environment. 
     One or both of the conductive layers  104  and  108  may include embedded devices (e.g., diodes) configured to temporarily electrically connect the lines on the layers  104  and  108  to form a radiating (antenna) structure during an RF operation (e.g., transmitting, receiving, performing near field communication, etc.) of a device utilizing the touchscreen. For example, beam lead or chip diodes may be placed in-between the layers  104  and  108 . In one example, embedding the diodes in the orthogonal planes of the conductive layers  104  and  108  may be done similarly to techniques used in microwave technology for embedding diodes in strip line assemblies. In one example, the diodes may be about 0.005 inch thick. In one example, interconnect technology to the touchscreen layers may be implemented using conventional techniques (e.g., bump contacts). 
     The conducting layers  104  and  108  are generally sufficient for forming a radiating structure. In general, the skin effect at 2.5 and 5.2 GHz keeps most of the electrons in the outer surface, so the fact that the conducting layers  104  and  108  comprise a thin wire is generally not an issue. Although the radiation resistance and dissipation resistance may be higher than for a very thick copper line, the higher radiation resistance and dissipation resistance may be compensated for with a transceiver matching circuit. In comparison, conventional antennas are typically electrically small and have less than desirable directivity (e.g., 1.2 to 1.8 dBi). 
     Referring to  FIG. 2 , a diagram is shown illustrating an example placement of a number of devices (e.g., diodes) in accordance with an embodiment of the invention. In one example, a number of diodes may be embedded in the touchscreen  100 . During a touchscreen operation, a controller (not shown) may poll, strobe, and/or multiplex the row and column electrodes to sense when and where the touchscreen  100  is touched. During an RF operation, the controller may be idled, predetermined lines of the touchscreen  100  may be temporarily electrically coupled, and an RF module  150  may be coupled to the touchscreen  100 . The RF module  150  may comprise a RF transmitter (or RF source), an RF receiver (or RF detector), and/or an RF transceiver. For example, the RF module  150  may be configured to utilize elements of the thin-film conducting layers  104  and  108  coupled by the diodes to form an antenna (radiating structure) for broadcasting (transmitting), receiving, and/or performing near field communication (NFC) using a radio frequency (RF) signal. 
     In one example, the RF module  150  may comprise a module  152 , a module  154 , and a module  156 . The module  152  may implement an RF signal source (e.g., a transmitter, transceiver, etc.). In another example, the module  152  may implement an RF signal receiver. The module  154  may implement an RF choke. The module  156  may implement a DC bias circuit. In one example, the DC bias circuit  156  may be configured to generate a bias signal that may be coupled to the touchscreen  100  via the RF choke  154  to configure elements of the touchscreen  100  as the radiating structure (e.g., a di-pole antenna, an inverted F antenna, a loop antenna, etc.). For example, the DC bias circuit  156  may generate a signal that forward biases the diodes coupled between the layers  104  and  108 , thus electrically connecting the associated conducting lines on the layers  104  and  108  to assemble the desired radiating structure. When the DC bias circuit stops generating the bias signal, the radiating structure is dis-assembled by essentially disconnecting the elements of the radiating structure and the associated conducting lines on the layers  104  and  108  are returned to the touchscreen configuration. 
     Referring to  FIG. 3 , a diagram is shown illustrating a cross-section of the touchscreen  100  of  FIG. 2  along the line A-A′. In one example, one or both of the conductive layers  104  and  108  may include embedded devices (e.g., diodes) configured to temporarily electrically connect one or more lines on the layer  104  with one or more lines on the layer  108  in order to form a radiating structure during an RF operation of a device utilizing the touchscreen  100 . In another example, discrete devices (e.g., beam lead, chip diodes, etc.) may be placed in-between the layers  104  and  108  during assembly of the layers. In one example, the diodes may be implemented with a thickness of about 0.005 inch, which should fit well within the space provided by the insulating layer  106 . Because resistive touchscreens typically have high resolution (e.g., 4096×4096 DPI or higher), the addition of the diodes between the layers  104  and  108  will generally have little effect on the operation of the touchscreen  100  in the touchscreen mode. In one example, embedding the diodes in the orthogonal planes of the conductive layers  104  and  108  may be done similarly to techniques used in microwave technology for embedding diodes in strip line assemblies. For example, an amorphous silicon process may be used where the diodes are fabricated on the substrates. 
     Referring to  FIG. 4 , a diagram is shown illustrating an example radiating structure formed when the diodes of  FIG. 2  are forward biased in response to the bias signal generated by the DC bias circuit  156 . The forward biased diodes generally provide a temporary electrical connection of the lines of the conductive layers  104  and  108  to form a radiating structure  160  that may be appropriate for transmission using WiFi, Bluetooth, ZigBee, near filed communication (NFC), etc. The RF module  150  may be configured to provide the WiFi, Bluetooth, ZigBee, NFC, or other RF capability. In one example, the DC bias circuit  156  may forward bias the diodes just prior to an RF operation (e.g., transmission, reception, etc.), interconnecting the appropriate lines and forming the appropriate antenna (e.g., a di-pole antenna, inverted F antenna, NFC loop antenna, etc.). Upon completion of the RF operation, the radiating structure  160  may be returned to isolated lines as soon as the forward biasing of the diodes is discontinued. 
     Referring to  FIG. 5 , a diagram is shown illustrating an example circuit in accordance with another embodiment of the invention. In one example, the touchscreen may be configured to allow an RF module to be connected to a number of different antenna structures. For example, a number of sets of diodes may be embedded in the conductive layers  104  and  108  to provide a number of different antennae (or radiating structures)  180   a - 180   n . An antenna selector  182  may be implemented to select the particular radiating structure connected to the RF module  150  at a particular time. In one example, the antenna selector  182  may have a control input that may receive a signal indicating the particular radiating structure to be formed. For example, by connecting the RF module  150  to the input line(s) associated with one of the radiating structures  180   a - 180   n , the desired antenna configuration may be formed when the DC bias circuit  156  forward biases the diodes associated with the particular one of the radiating structures  180   a - 180   n.    
     Referring to  FIG. 6 , a diagram is shown illustrating another example of a circuit allowing connections between multiple RF modules and multiple radiating structures. In one example, a number of sets of diodes may be embedded between the layers  104  and  108  to provide a number of different radiating structures. A number of RF modules  200   a - 200   n  may also be implemented. An antenna control and multiplexing module  210  may be configured to couple the touchscreen configured to implement the number of radiating structures with the number of RF modules  200   a - 200   n . The antenna control and multiplexing module  210  may be configured to select the particular radiating structure and a particular one of the RF modules  200   a - 200   n  to be connected at a particular time. In one example, the antenna control and multiplexing module  210  may have a control input that may receive a signal (e.g., CHANNEL) indicating the particular radiating structure and transmitter. In another example, the antenna control and multiplexing module  210  may have a second control input that may receive a signal (e.g., BROADCAST) indicating when to turn on the DC bias for forward biasing the appropriate diodes. It would be apparent to those of skill in the pertinent art(s) that the functionality described in connection with the signals CHANNEL and BROADCAST may be implemented as a single or multiple signals. 
     Referring to  FIG. 7 , a flow diagram is shown illustrating a process  300  in accordance with an embodiment of the invention. In one example, the process (or method)  300  may comprise a step (or state)  302 , a step (or state)  304 , a step (or state)  306 , a step (or state)  308 , a step (or state)  310 , a step (or state)  312 , and a step (or state)  314 . The process  300  may start in the step  302  and move to the step  304 . In the step  304 , the process  300  may disable touch detecting circuitry associated with all or a portion of a matrix resistive touchscreen. In the step  306 , the process  300  may temporarily connect lines on conductive layers of the matrix resistive touchscreen to form a radiating structure (e.g., di-pole antenna, inverted F antenna, loop antenna, etc.). In the step  308 , the process  300  may use the radiating structure formed in the step  306  to transmit and/or receive information. In the step  310 , the process  300  may disconnect the lines in the conductive layers of the touchscreen to disassemble the radiating structure and return the touchscreen to a touch sensitive mode. In the step  312 , the process  300  may re-enable the touch detecting circuitry associated with the touchscreen. The process  300  generally ends in the step  314 . 
     Although the examples provide above refer to indium tin oxide (ITO) and/or indium zinc oxide (IZO), it will be apparent to those of ordinary skill in the art that the thin-film conductive (or conducting) material used to form the conductive layers  104  and  108  may include, for example, (i) conductive polymers (e.g., including polypyrrole, polyaniline or polythiophene), (ii) transparent conducting oxides (e.g., including tin doped indium oxide (ITO), fluorine doped zinc oxide (FZO), aluminum doped zinc oxide AlZO, indium doped zinc oxide (IZO), antimony doped tin oxide (SbTO), and fluorine doped tin oxide (FTO)), and (iii) low-resistance metallic material such as molybdenum (Mo), silver (Ag), titanium (Ti), copper (Cu), aluminum (Al), and/or molybdenum/aluminum/molybdenum (Mo/Al/Mo). The terms “may” and “generally” when used herein in conjunction with “is(are)” and verbs are meant to communicate the intention that the description is exemplary and believed to be broad enough to encompass both the specific examples presented in the disclosure as well as alternative examples that could be derived based on the disclosure. The terms “may” and “generally” as used herein should not be construed to necessarily imply the desirability or possibility of omitting a corresponding element. 
     While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the scope of the invention.