Patent Publication Number: US-2007117520-A1

Title: Communication unit

Description:
TECHNICAL FIELD  
      The present invention relates to a sheet-like communication unit that has a plurality of communication elements which are embedded in the communication unit, and trasmits information as the communication elements communicate with neighboring communication elements to form a network.  
     BACKGROUND ART  
      The inventors of this application have proposed a technology regarding a sheet-like (cloth-like, paper-like, foil-like, tabular, or the like, which spreads in a plane and is thin) communication unit in which a plurality of communication elements are embedded. For example, proposed in the following literature is a communication unit that transits a signal as a plurality of communication elements, embedded in a sheet-like member (hereinafter, called “sheet-like body”) without forming individual wirings, relay the signal.  
      Patent Literature 1: Unexamined Japanese Patent Publication KOKAI Publication No. 2004-007448  
      According to the technology disclosed in the “Patent Literature 1”, the communication elements are laid out at the vertices of a grid-like, triangular, or honeycomb-like drawing on the surface of the sheet-like body. Each communication element communicates only with other communication elements laid out around it by using the fact that a change in electric potential generated by the communication element is to be intensively transitted to the neighborhood, but transmitted to a distant place in an attenuation manner.  
      This local communication allows successive transmission of a signal between the communication elements, thereby transmitting the signal to the destination communication element. The plurality of communication elements are hierarchically divided by management functions, and routing data is set in each hierarchy, so that a signal can be efficiently transmitted to the final destination communication element.  
     DISCLOSURE OF INVENTION  
      Problem to be Solved by the Invention  
      In such a communication unit that has communication elements approximately regularly embedded in the sheet-like body, and transmits information as the communication elements communicate form a network, various new technical proposals are strongly desired to meet various demands and applications regarding how to structure the sheet-like body, and how to lay out the communication elements.  
      The invention meets such demands, and it is an object of the invention to provide a sheet-like communication unit that transmits information and transmits information as the communication elements communicate with neighboring communication elements to form a network.  
      Means for Solving the Problem  
      To achieve the object, the following subject matters are disclosed according to the principle of the invention.  
      A communication unit according to the first aspect of the invention comprises a ground layer section, a power-source layer section, a plurality of conductive layer sections, a plurality of coupling resistor sections, a plurality of pull resistor sections, and a plurality of communication element sections, and is structured as follows.  
      That is, the ground layer section is a sheet-like conductive material.  
      The power-source layer section is a sheet-like conductive material laid out opposite to the ground layer section, and whose electric potential to the ground layer section becomes a predetermined reference electric potential.  
      The plurality of conductive layer sections are sheet-like conductive materials laid out between the ground layer section and the power-source layer section.  
      The plurality of coupling resistor sections are laid out between the ground layer section and the power-source layer section, and couple adjacent ones of the plurality of conductive layer sections with each other  
      The plurality of pull resistor sections couple the power-source layer section and the plurality of conductive layer sections, respectively.  
      The pull resistor means either a pull-up resistor or a pull-down resistor, and whether it functions as the pull-up resistor to the ground layer section or functions as the pull-down resistor depends on whether the electric potential of the power-source layer section is positive or negative. The same is true of the following.  
      As the pull resistor section, a resistor which couples the power-source layer section and the conductive layer section may be used, or the clearance between those sections may be filled with a material having a certain resistivity. The same is true of the following.  
      The power-source layer section is the plurality of communication elements which are respectively associated with the plurality of conductive layer sections, transmit information by changing electric potentials of the associated conductive layer sections to the ground layer section, and acquire the transmitted information by detecting changes in electric potentials to be propagated to those conductive layer sections which are adjacent to the associated conductive layer sections through any of the plurality of coupling resistor sections.  
      A communication unit according to another aspect of the invention comprises a ground layer section, a power-source layer section, first and second conductive layer sections, a coupling resistor section, first and second pull resistor sections, and first and second communication element sections, and is structured as follows.  
      That is, the ground layer section is a sheet-like conductive material.  
      The power-source layer section is a sheet-like conductive material laid out opposite to the ground layer section, and whose electric potential to the ground layer section becomes a predetermined reference electric potential.  
      The first conductive layer section and the second conductive layer section are sheet-like conductive materials laid out between the ground layer section and the power-source layer section.  
      The coupling resistor section is laid out between the ground layer section and the power-source layer section, and couples the first conductive layer section and the second conductive layer section with each other.  
      The first pull resistor section couples the power-source layer section and the first conductive layer section.  
      The second pull resistor section couples the power-source layer section and the second conductive layer section.  
      The first communication element section changes the electric potential of the first conductive layer section to the ground layer section in accordance with information to be transmitted  
      The second communication element section acquires the transmitted information by detecting a change in electric potential to be propagated to the second conductive layer section through the coupling resistor section as the electric potential of the first conductive layer section to the ground layer section changes.  
      The communication unit of the invention may be structured in such a way that the first communication element section lets a current to flow between the first communication element section and the ground layer section to change the electric potential of the first conductive layer section to the ground layer section, and the second communication element section compares an electric potential of the second communication element section to the ground layer section with the predetermined reference electric potential, and detects a change in electric potential.  
      In the communication unit of the invention, the first communication element section and the second communication element section may be so structured in such a way as to be operated with a potential difference between the power-source layer section and the ground layer section as power.  
      The communication unit of the invention may be structured in such a way that the first conductive layer section, the second conductive layer section and the coupling resistor section constitute a sheet-like signal layer section which is laid out between the ground layer section and the power-source layer section, and the first communication element and the second communication element are operated with a potential difference between the signal layer section and the ground layer section as power.  
      The communication unit of the invention may be structured in such a way that the signal layer section comprises a sheet-like conductive material whose resistivity changes locally, and an average resistivity of an area of the sheet-like conductive material corresponding to the first conductive layer section and the second conductive layer section is smaller than an average resistivity of an area of the sheet-like conductive material corresponding to the coupling resistor section.  
      The communication unit of the invention may be structured in such a way that the first conductive layer section and the second conductive layer section have approximately square shapes, and the first communication element and the second communication element are respectively laid out at centers of the first conductive layer section and second conductive layer section. Instead of the approximate square shape, a polygon such as an approximately equilateral triangle, or an approximately equal hexagon which can fill up a plane may be used. The communication element may be laid out at other than the center.  
      A communication unit according to the other aspect comprises a ground layer section, a power-source layer section, a plurality of conductive layer sections, a plurality of pull resistor sections, and a plurality of communication elements, and is structured as follows.  
      That is, the ground layer section is a sheet-like conductive material.  
      The power-source layer section is a sheet-like conductive material laid out opposite to the ground layer section, and whose electric potential to the ground layer section becomes a predetermined reference electric potential.  
      The plurality of conductive layer sections are sheet-like conductive materials laid out between the ground layer section and the power-source layer section.  
      The plurality of pull resistor sections couple the power-source layer section and the plurality of conductive layer sections, respectively.  
      The plurality of communication element sections couple adjacent ones of the plurality of conductive layer sections with each other.  
      Each of the plurality of communication element sections changes an electric potential of one of the conductive layer sections coupled by the communication element section with respect to the ground layer section in accordance with information to be transmitted, and acquires the transmitted information by detecting a change in an electric potential of the other one of the conductive layer sections coupled by the communication element section with respect to the ground layer section.  
      A communication unit according to another aspect of the invention comprises a ground layer section, a power-source layer section, a conductive layer section, a pull resistor section, and first and second communication element sections, and is structured as follows.  
      That is, the ground layer section is a sheet-like conductive material.  
      The power-source layer section is a sheet-like conductive material laid out opposite to the ground layer section, and whose electric potential to the ground layer section becomes a predetermined reference electric potential.  
      The conductive layer section is a sheet-like conductive material laid out between the ground layer section and the power-source layer section.  
      The pull resistor section couples the power-source. layer section and the conductive layer section.  
      The first communication element section changes an electric potential of the conductive layer section to the ground layer section in accordance with information to be transmitted.  
      The second communication element section acquires the transmitted information by detecting a change in the electric potential of the conductive layer section to the ground layer section.  
      The communication unit of the invention may be structured in such a way that the first communication element section lets a current to flow between the first communication element section and the ground layer section to change the electric potential of the first conductive layer section to the ground layer section, and the second communication element section compares an electric potential of the second communication element section to the ground layer section with the predetermined reference electric potential, and detects a change in electric potential.  
      In the communication unit of the invention, the first communication element section and the second communication element section may be structured in such a way as to be operated with a potential difference between the power-source layer section and the ground layer section as power.  
      In the communication unit of the invention, the first communication element section and the second communication element section may be structured in such a way as to be operated with a potential difference between the signal layer section and the ground layer section as power.  
      The communication unit of the invention may be structured in such a way that the conductive layer section has an approximately square shape, and the first communication element section and the second communication element section are respectively laid out at centers of different edges of the approximate square of the conductive layer section.  
      In addition, the communication unit of the invention may be structured in such a way that the plurality of conductive layer sections are laid out in such a manner as to sandwich the power-source layer section with the ground layer section or sandwich the ground layer section with the power-source layer section instead of being laid out between the ground layer section and the power-source layer section.  
      That is, the positions of the plurality of conductive layer sections, power-source layer section, and ground layer section may be changed with one another.  
      Effect of the Invention  
      According to the invention, it is possible to provide a sheet-like communication unit that has a plurality of communication elements which are embedded in the communication unit, and transmits information as the communication elements communicate with neighboring communication elements to form a network. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  An explanatory diagram for explaining the basic structure of the invention.  
       FIG. 2  An explanatory diagram illustrating how individual conductive layer section are coupled by resistors which are coupling resistors.  
       FIG. 3  An explanatory diagram illustrating how individual conductive layer sections are coupled by communication elements.  
       FIG. 4  An explanatory diagram illustrating how a part of a central-layout type communication unit is.  
       FIG. 5  An exemplarily diagram illustrating a schematic structure of a tree-layer-contact type communication element.  
       FIG. 6  An explanatory diagram illustrating typical circuit structures of a reception circuit and a transmission circuit.  
       FIG. 7  An exemplarily diagram illustrating a schematic structure of a two-layer-contact type communication element.  
       FIG. 8  An explanatory diagram illustrating typical circuit structures of a reception circuit and a transmission circuit.  
       FIG. 9  An explanatory diagram illustrating how a signal layer section has a coupling resistor section filling between conductive layer sections in a sheet-like manner.  
       FIG. 10  An explanatory diagram of a boundary-layout type communication unit.  
       FIG. 11  An explanatory diagram of a boundary-layout type and three-layer-contact type communication element.  
       FIG. 12  An explanatory diagram of a boundary-layout type and two-layer-contact type communication element.  
       FIG. 13  An explanatory diagram illustrating how a power-source layer section, a ground layer section, and a conductive layer section are patterned.  
       FIG. 14  An explanatory diagram explaining another embodiment of a signal layer section.  
       FIG. 15  An explanatory diagram explaining an embodiment of a central-layout type communication unit which interchanges the order of a power-source layer section and a conductive layer section.  
       FIG. 16  An explanatory diagram explaining an embodiment of a boundary-layout type communication unit which interchanges the order of a power-source layer section and a conductive layer section  
       FIG. 17  An explanatory diagram explaining an embodiment of a communication unit which uses a coupling body comprising a resistor and a capacitor or a coupling body comprising a capacitor, instead of a coupling resistor section. 
    
    
     DESCRIPTION OF REFERENCE NUMBERS  
       100  communication unit  
       101  ground layer section  
       102  power-source layer section  
       103  conductive layer section  
       104  pull resistor section  
       105  circuit of transmission communication element  
       106  circuit of reception communication element  
       107  coupling resistor section  
       301  communication element section  
       401  communication element  
       501  communication circuit  
       502  contact  
       503  contact  
       504  contact  
       511  reception circuit  
       512  transmission circuit  
       513  control circuit  
       701  communication element  
       702  contact  
       703  contact  
       704  diode  
       705  resistor  
       706  capacitor  
       711  reception circuit  
       712  transmission circuit  
       713  control circuit  
       801  signal layer section  
       901  communication element  
       951  resistor  
       952  good conductor  
       971  coupling body  
     BEST MODE FOR CARRYING OUT THE INVENTION  
      Embodiments of the invention will now be explained below. The embodiments to be discussed below are for explanation, and do not for limit the scope of the invention. Accordingly, a person skilled in the art can adapt embodiments which replace each component or all components with equivalents, and those embodiments are to be included within the scope of the invention.  
      (Basic Structure)  
       FIG. 1  is an explanatory diagram for explaining the basic structure of the invention.  FIG. 1 ( a ) is a top plan view (plan view),  FIG. 1 ( b ) is a cross-sectional view, and  FIG. 1 ( c ) is an equivalent circuit diagram. An explanation will be hereinafter given with reference to this figure.  
      In a communication unit  100 , a ground layer section  101  which is a sheet-like (foil-like) conductive material (good conductor) and a power-source layer section  102  which is a sheet-like (foil-like) conductive material (good conductor) are laid out in such a way that their one sides face with each other. The clearance between them is approximately constant, and because a voltage is applied to the power-source layer section  102  in such a way that the power-source layer section becomes a predetermined reference electric potential to the ground layer section  101 , they are laid out like a plate capacitor.  
      A plurality of conductive layer sections  103  having smaller shapes than those of these sheet-like bodies are laid out between the ground layer section  101  and the power-source layer section  102 . Accordingly, the space between each conductive layer section  103  and the power-source layer section  102 , and the space between each conductive layer section  103  and the ground layer section  101  also structurally look like plate capacitors.  
      The clearance between each conductive layer section  103  and the ground layer section  101  are also constant, the shapes of the individual conductive layer sections  103  are squares in  FIG. 1 , and the individual conductive layer sections  103  are laid out like grids as viewed from above at equal intervals. In this figure, 4×4=16 conductive layer sections  103  are laid out, but their layout number can be appropriately changed, and, in general, a larger number of them are laid out.  
      Members with predetermined resistivities are filled between individual conductive layer sections  103  and the power-source layer section  102 , and constitute a plurality of pull resistor sections  104 .  
      Because the pull resistor sections  104  allow electric charges to pass, and a voltage is applied to the power-source layer section  102  in such a way that the power-source layer section becomes the predetermined reference electric potential, the electric potentials of the individual conductive layer sections  103  to the ground layer section  101  also become the reference electric potential.  
      An equivalent circuit such as one illustrated in  FIG. 1 ( c ) is constituted in this manner. That is, a resistance corresponding to the pull resistor section  104  is R 2 , and the capacitance of a part which constitutes a capacitor is C.  
      In a case of such a structure, when a current is let to pass with a circuit  105  formed between a conductive layer section  103  and the ground layer section  101 , the electric potential of that conductive layer section  103  changes. For example, when the electric potential of the power-source layer section  102  is positive and a current is let to flow to the ground layer section  101  from the conductive layer section  103 , the electric potential of the conductive layer section  103  decreases.  
      In this way, the communication element transmits a signal by forming the circuit  105  between the conductive layer section  103  and the ground layer section  101 , and letting a current flow to thereby change the electric potential of the conductive layer section  103 .  
      In a case where the communication elements receive signals, on the other hand, there are two conceivable methods such as detecting changes in the electric potentials to be propagated from the individual conductive layer sections  103  and directly detecting changes in the electric potentials of the individual conductive layer sections  103 . In view of the layout of the communication elements, the former is called a central-layout type, and the latter is called a boundary-layout type  
      (Central-Layout Type)  
      In a case of the central-layout type, coupling the adjacent conductive layer sections  103  by a resistor allows a change in voltage to be propagated.  
       FIG. 2  is an explanatory diagram illustrating how individual conductive layer sections are coupled together by resistors which are coupling resistors.  FIG. 2 ( a ) is a top view,  FIG. 2 ( b ) is a cross-sectional view,  FIG. 2 ( c ) is an equivalent circuit diagram, and  FIG. 2 ( d ) is an explanatory diagram illustrating how a change in electric potential propagates. An explanation will be hereinafter given with reference to this figure.  
      As illustrated in  FIG. 2 , with the adjacent conductive layer sections  103  being coupled together by a coupling resistor section  107 , when the electric potential of a conductive layer section  103  changes, this change in electric potential is intensively transmitted to the neighborhood, but the propagation of the change to a distant place is attenuated exponentially with respect to a distance.  
      Therefore, provided that a change in electric potential is detected by using a comparator when a transmission communication element (circuit  105 ) changes the electric potential of the conductive layer section  103  connected to that communication element, if the threshold of the comparator is appropriately set, a signal is to be transmitted only to a reception communication element (circuit  106 ) connected to the conductive layer section  103  adjacent to the transmission communication element (circuit  105 ).  
      It is understood that the conductive layer sections  103  and the coupling resistor sections  107 , observed as a whole, like the ground layer section  101  and the power-source layer section  102  are in a sheet-like shape. This sheet-like structure is hereinafter called “signal layer section”, as needed.  
      When an equivalent circuit is constituted as illustrated in FG  2 ( c ), if the circuit  105  changes the electric potential at a conductive layer section  103 , as illustrated in  FIG. 2 ( d ), the change in electric potential at the adjacent conductive layer section  103  is to be divided by a resistor, a certain level of a change in electric potential can be detected at the adjacent circuit  106 , but the change in electric potential further decreases at a further distant circuit  106 . In a case where a signal is transmitted in this manner, it is necessary to change the electric potential based on a frequency.  
      In this figure, the resistor of the coupling resistor section  107  is R 1 , the resistor of the pull resistor section  104  is R 2 , the capacitances of a capacitor between the ground layer section  101  and the conductive layer section  103 , and a capacitor between the power-source layer section  102  and the conductive layer section  103  are C, respectively. Provided the impedance of the resistor R 2  is so set as to be smaller than the impedance of the capacitance C at a signal frequency band to be used, even if a change in electric potential at a conductive layer section  103  changes at one frequency band, the pattern of that change is divided and transmitted to the adjacent conductive layer section  103 .  
      In contrast in the latter case, a signal is transmitted from a transmission communication element (circuit  105 ) to a reception communication element (circuit  106 ) by arranging the transmission circuit  105  for letting a current to flow around the conductive layer section  103  and the reception circuit  106  for detecting electric potentials. In this figure, to facilitate understanding, one communication element (circuit  105 ) and the plurality of reception communication elements (circuit  106 ) are illustrated, but typically, for each conductive layer section  103 , one transmission communication element (circuit  105 ) and one reception communication element ( 106 ) are disposed, or a communication element which includes both circuits is disposed  
      (Boundary-Layout Type)  
      In the boundary-layout type, adjacent conductive layer sections are coupled together by one communication element to transmit a signal.  
       FIG. 3  is an explanatory diagram illustrating how the individual conductive layer sections are coupled together by the communication elements.  FIG. 3 ( a ) is a top view  FIG. 3 ( b ) is a cross-sectional view, and  FIG. 3 ( c ) is an equivalent circuit diagram. An explanation will be hereinafter given with reference to this figure.  
      Each conductive layer section  103  is provided with communication element sections  301  on the individual sides, respectively, for connection to the adjacent conductive layer sections.  
      As the electric potential at a conductive layer section  103  is changed by one communication element section  301 , other one communication elements  301  which are coupled to the same conductive layer section  103  can detect the change in electric potential. This is the minimum unit of signal transmission, which makes it possible to transmit a signal within an area corresponding to the shape of a square.  
      The communication element which has detected the change in electric potential and received the signal further transmits the signal to the adjacent conductive layer section  103  coupled by that communication element, if necessary. That is, the signal is transmitted farther by changing the electric potentials of the adjacent conductive layer sections  103 .  
      To facilitate understanding, the connection between the communication element section  301  and the ground layer section  101  is omitted in this figure. Because the communication element sections  301  have only to change the electric potentials of the conductive layer sections  103  and detect the electric potential changes, as mentioned above, the most general mode is that the communication elements change the electric potentials by, for example, letting a current to flow between the communication element sections  301  and the ground layer section  101 , as per the central-layout type.  
      Two embodiments of the invention can be thought from the basic structure as described above. Those structures will be hereinafter explained in more detail.  
     FIRST EMBODIMENT  
      This embodiment corresponds to the central-layout type, and is a communication unit according to a structure which couples the conductive layer sections  103  together by the coupling resistor section  107  and makes use of the attenuation of propagation of an electric potential change in accordance with the distance, to transmit information to the neighborhood.  
       FIG. 4  is an explanatory diagram illustrating how a part of the central-layout type communication unit is.  FIG. 4 ( a ) is a cross-sectional view of that unit according to an embodiment of a three-layer-contact type, and  FIG. 4 ( b ) is a cross-sectional view of that unit according to an embodiment of a two-layer-contact type. Their explanations will be hereinafter given in order.  
      (Three-Layer-Contact Type)  
      In the embodiment of the three-layer-contact-type, a communication element  401  includes the ground layer section  101 , the power-source layer section  102 , the conductive layer section  103 , and contacts, and is so laid out as to penetrate the center of each conductive layer section  103 .  
       FIG. 5  is an exemplarily diagram illustrating the schematic structure of such a three-layer-contact type communication element  401 . An explanation will be hereinafter given with reference to this figure.  
      The communication element  401  includes a communication circuit  501 , a contact  502  to the ground layer section  101 , a contact  503  to the power-source layer section  102 , and a contact  504  to the conductive layer section  103 . The communication circuit  501  has a reception circuit  511 , a transmission circuit  512 , and a control circuit  513 .  
      The reception circuit  511 , the transmission circuit  512 , and the control circuit  513  are operated with a potential difference between the ground layer section  101  and the power-source layer section  102  as power.  
      Various information processing apparatuses such as a more general logical circuit, and a further advanced small computer can be considered as the control circuit  513 . The control circuit  513  controls the reception circuit  511  and the transmission circuit  512  to communicate with the adjacent communication element  401 , and constitutes a network. Regarding the control method for such communication, the technology disclosed in the above-described “Patent Literature 1” can be applied.  
       FIG. 6  is an explanatory diagram illustrating typical circuit structures of the reception circuit  511  and the transmission circuit  512 .  
      The reception circuit  511  classifies electric potentials into two levels of an H level and an L level by means of a comparator, according to which an electric potential change is detected. The threshold of the electric potential is set by the ratio of potential division by resistors r 1  and r 2  of the reception circuit. As mentioned above, the threshold is so set as to enable detection of a change in electric potential when the adjacent communication elements  401  change the electric potential, and as not to permit the change to exceed the threshold when a communication element  401  located farther than the adjacent ones.  
      The combined resistance of the resistors r 1  and r 2 , and the input impedances of the comparator are so set as to be sufficiently larger than the impedance R 2  of the pull resistor section  104 , and as not to cause the presence of the reception circuit to affect a signal voltage.  
      In contrast an output OUT of the reception circuit  512  can be three states of an H level, an L level, and a high impedance. The transmission circuit  512  receives a control signal from the control circuit  513  at terminals S 1  and S 2 . In this reception circuit  512 , as S 1  and S 2  are simultaneously set to H, an L-level signal is output from OUT, and as S 1  and S 2  are simultaneously set to L, an H-level signal is output from OUT. As S 1  is set at H and S 2  is set to L, it becomes a high impedance.  
      The communication element  401  outputs an L level or an H level from OUT when transmitting a signal by itself In other cases, the transmission circuit  512  is set to a high impedance state, so that the reception circuit  511  receives a signal.  
      In the transmission circuit  512 , diodes put between an nMOS and a pMOS are for adjusting the amplitude of an output voltage. If all diodes are removed and the pMOS and the nMOS are short-circuited, the H level of OUT becomes the electric potential (predetermined reference electric potential) of the power-source layer section  102 , and the L level of OUT becomes the electric potential of the ground layer section  101 . Insertion of the diodes increases the electric potential of the L level by the forward voltage drop of the diodes.  
      In the three-layer-contact type, the pull resistor section  104  may be mounted in the communication element section  301 .  
      In the communication element section  301 , the conductive layer sections  103  may be connected to both the power-source layer section  102  and the ground layer section  101  by resistors, and the conductive layer sections  102  may be held at a voltage dividing point by those resistors at a normal time when no signal is generated.  
      (Two-Layer-Contact Type)  
      A two-layer-contact type communication element  701  is so laid out as to have the ground layer section  101 , the conductive layer section  103 , and contacts. Although the communication element  401  of the three-layer-contact type uses the potential difference between the ground layer section  101  and the power-source layer section  102  as a supply voltage, the communication element  701  of the two-layer-contact type uses a potential difference between the ground layer section  101  and the conductive layer section  103  as a supply voltage.  
       FIG. 7  is an exemplarily diagram illustrating the schematic structure of the two-layer-contact type communication element. An explanation will be hereinafter given of this figure.  
      The communication element  701  comprises a contact  702  to the ground layer section  101 , a contact  703  to the conductive layer section  103 , a diode  704 , a resistor  705 , a capacitor  706 , a reception circuit  712 , a transmission circuit  712 , and a control circuit  713 .  
      A voltage for operating the reception circuit  711 , the transmission circuit  712 , and the control circuit  713  is a potential difference between the contact  702  to the ground layer section  101  and the contact  703  to the conductive layer section  103 .  
      A charge is stored in the capacitor  706  from the contact  703  through the diode  704  and the resistor  705 , and becomes the power source for operating the reception circuit  711 , the transmission circuit  712 , and the control circuit  713 . Hereinafter, let the resistance of the resistor  705  be Re, the capacitance of the capacitor be Ce, and the forward voltage drop of the diode  704  be Vd.  
      A packet transfer frequency is adjusted in such a way that the sum TL of the time during which the communication element  701  is transmitting a signal electric potential of L level becomes less than 1/n times the total communication time T 0 , that is, TL&lt;T 0 /n, and the average current consumption of the circuit at this time is expressed as I. The time constant CeRe is so set as to be sufficiently large, and Re is so set as to be sufficiently larger than a load impedance (in this embodiment, R 2  in the equivalent circuit) at the time of transmitting a signal to the conductive layer section  103 . Under such settings, a voltage V between both ends of the capacitor  706  becomes V=Ve−Vd−IR, with respect to the reference electric potential Ve. Accordingly, the reception circuit  711 , the transmission circuit  712 , and the control circuit  713  have only to be so structured as to be operated with the voltage V.  
      Various information processing apparatuses such as a more general logical circuit, and a further advanced small computer can be considered as the control circuit  713 . The control circuit  713  controls the reception circuit  711  and the transmission circuit  712  to communicate with the adjacent communication elements  701 , and constitutes a network. Regarding the control method for such communication, the technology disclosed in the above-described “Patent Literature 1” can be applied.  
       FIG. 8  is an explanatory diagram illustrating typical circuit structures of the reception circuit  711  and the transmission circuit  712 . An explanation will be hereinafter given with reference to this figure.  
      An input S of the transmission circuit  712  is connected to the control circuit  713 , and an output OUT is connected to the contact  703  with the conductive layer section  103 . The difference from the transmission circuit  512  is that the pMOS is removed for the source voltage supplied to the transmission circuit may become lower than the electric potential of the conductive layer section  103 .  
      Because it is structured by using the nMOS instead of using pMOS in this manner, no current is supplied from the transmission circuit  712  to the conductive layer section  103  at the rise of a signal. Therefore, the condition under which the conductive layer section  103  is correctly pulled is that the resistor R 2  of the equivalent circuit is so set as to be smaller than the impedance of its parallel capacitor.  
      In the reception circuit  711 , a circuit (surrounded by the dotted line in the figure) which compensates the voltage difference between V and Ve is inserted in the preceding stage. If the time constant of CH and r 1 +r 2  in a signal-H-level-hold circuit is secured sufficiently larger than the continuous time of the L level of a signal, an H-level signal can be held at the terminal of CH. Moreover, if the resistors in the figures are so set as to have a relationship like r 0 =r 1 +r 2 , a terminal voltage of r 0  and a terminal voltage of CH can become equal to each other when the signal is at the H level.  
      Because the threshold can be set by the proportion of r 1  and r 2 , a slight voltage drop (change in electric potential) at the conductive layer section  103  is stably detectable.  
      (Modification of the Signal Layer Section or the Like)  
      In the above-described embodiment, individual conductive layer sections  103  are independent conductive materials, and are coupled by the coupling resistor section  107 , and there is a space in the signal layer section. This space may be filled by an appropriate electric insulator, or may be left as it is.  
      Herewith, the signal layer section is also a sheet-like material, according to a further advancement of which the coupling resistor section  107  may be filled between the conductive layer sections  103  in a sheet-like manner.  FIG. 9  is an explanatory diagram illustrating how a signal layer section has the coupling resistor section  107  filling between the conductive layer sections  103  in a sheet-like manner.  
      As illustrated in  FIG. 9 ( a ), a signal layer section  801  comprises a plurality of conductive layer sections  103  and one coupling resistor section  107  which has the same thickness as those of the conductive layer sections, and is structured by making holes in the sheet-like coupling resistor section  107 , and embedding the conductive layer sections  103  in those holes. Even with such a structure employed, the propagation of an electric potential charge is rapidly attenuated at a distant place, so that a signal can be transmitted as per the above-described embodiment.  
      As illustrated in  FIG. 9 ( b ), a piece of sheet-like member whose resistivity differs locally, and continuously or discontinuously changes may be used as the signal layer section  801 . In this case, if the average resistivity of an area corresponding to the conductive layer section  103  is set extremely low, and the average resistivity of an area corresponding to the coupling resistor section  107  is set high, it is possible to achieve the same function as the signal layer section  801  illustrated in  FIG. 9 ( a ).  
     SECOND EMBODIMENT  
      This embodiment corresponds to a boundary-layout type.  FIG. 10  and  FIG. 11  are explanatory diagrams illustrating how apart of such a communication unit is.  FIG. 10 ( a ) is a cross-sectional view according to an embodiment of the three-layer-contact type, and  FIG. 10 ( b ) is a cross-sectional view according to an embodiment of the two-layer-contact type.  FIG. 11  is an explanatory diagram of the structure of a communication unit according to the embodiment of the three-layer-contact type.  FIG. 12  is an explanatory diagram of the structure of a communication unit according to the embodiment of the two-layer-contact type.  
      In the boundary-layout type, a communication element  901  is so arranged as to lie over the adjacent sides of the two conductive layer sections  103 . In the central-layout type, the connection between the communication element  401  and the conductive layer section  103  is made by one common terminal, whereas in the boundary-layout type, the connection between the communication element  901  and the conductive layer section  103  is made by two terminals.  
      In  FIG. 11  and  FIG. 12 , to facilitate understanding, the outputs OUT  1  and OUT  2  of two transmission circuits are collectively illustrated as one output from one transmission circuit, and the inputs IN  1  and IN  2  of two reception circuits are collectively illustrated as one input to one reception circuit. They may be structured by just parallel connections. In this case, the same communication element as that of the central-layout type can be used for the boundary-layout type.  
      An embodiment such that a pair of a transmission circuit and a reception circuit are prepared on the OUT  1 /IN  1  side, and another pair of a transmission circuit and a reception circuit are prepared on the OUT  2 /IN  2  side may be adapted. In this case, a control device controls the two transmission circuits and the two reception circuits.  
      In each communication unit  901 , when the reception circuit have detected the transmission of a signal from a change in the electric potential of one of the conductive layer section  103 , the control circuit determines whether or not it is necessary to transmit the signal to the other one of the conductive layer sections  103 , and, when transmission is necessary, the transmission circuit changes the electric potential of the other one of the conductive layer sections  103  to transmit the signal.  
      In the case of the two-layer-contact type, and the individual circuits are driven upon reception of an electric charge supplied from only either one of the two conductive layer sections  103 . Accordingly, provided that communication elements laid out at two sides of four sides of the square in each conductive layer section  103  are supplied with electric charges, it is desirable that the loads of the electric-charge supplies of the individual conductive layer sections  103  should be averaged.  
      In the case of the two-layer-contact type, there is space between the conductive layer sections  103 , and in the case of the tre-layer-contact type, there is space in the other portion of the space between the conductive layer sections  103  than the portion where the communication element  901  penetrates. The space may be filled by an electric insulator, and the conductive layer sections  103  and the remaining portions may be constituted by a sheet-like member whose resistivity changes locally as illustrated in  FIG. 9 ( a ), ( b ).  
     THIRD EMBODIMENT  
      In both of the above-described examples, while the ground layer section  101  and the power-source layer section  102  are assumed to be a homogeneous sheet-like type, they may be one patterned to a certain degree (for example, conductors patterned like meshes).  
      For example, the good conductors of the ground layer section  101  and power-source layer section  102  may be laid out in such areas where they do not overlap the individual conductive layer sections  103 . In this case, the good conductors of the ground layer section  101  and power-source layer section  102  are in a meshe-like pattern, and the conductive layer sections  103  are located so as to overlap the spaces of the meshes.  FIG. 13  is an explanatory diagram illustrating how such a pattern is. Regarding the ground layer section  101  and the power-source layer section  102  in the figure, the hatched portions are the portions where good conductors are present.  
      This figure illustrates a case of the boundary-layout type, but the central-layout type can employ a similar pattern  
     FOURTH EMBODIMENT  
      This embodiment proposes a scheme of another structure of the signal layer section  801 .  FIG. 14  is an explanatory diagram explaining another embodiment of the signal layer section.  FIG. 14 ( a ) is atop view of the signal layer section  801 , and  FIG. 14 ( b ), ( c ) and ( d ) are cross-sectional views of three embodiments of the signal layer section  801 .  
      As illustrated in this figure, in the sheet-like signal layer section  801 , a plurality of conductive layer sections  103  are in close contact with a single sheet-like resistor  951 , and a good conductor  952  is so arranged as to lay over the conductive layer sections  103  with the resistor  951  in between.  
      This can allow the sheet-like resistor  951  to function as the pull resistor section  104 , and the good conductor  952  decreases the coupling resistance of the adjacent conductive layer sections  103 .  
      In ( c ) and ( d ) of the same figure, the good conductors  952  and the conductive layer sections  103  are so laid out as to be caved in the resistor  951 , and the entire shape of the signal layer section  801  is patterned like a single flat sheet. This structure facilitates handling, and makes the construction easier by using a technique like etching.  
     FIFTH EMBODIMENT  
      In the above embodiment, the conductive layer section  103  is sandwiched between the ground layer section  101  and the power-source layer section  102 , but this order may be changed. That is, this is an embodiment where the power-source layer section  102  is sandwiched between the ground layer section  101  and the conductive layer section  103 .  FIG. 15  and FG  16  are explanatory diagrams of such an embodiment.  
      When the order of the power-source layer section  102  and the conductive layer section  103  is changed, the capacitances of capacitors in an equivalent circuit change, but there are no substantive changes in the other structures and the operation principles. Accordingly, a structure similar to those of the above-described embodiments can be employed.  
      In addition, although the above-described embodiments are structure in such a way that the conductive layer sections  103  (signal layer sections) is sandwiched between the ground layer section  101  and the power-source layer section  102 , an embodiment where the power-source layer section  102  is sandwiched between the conductive layer sections  103  and the ground layer section  101 , or an embodiment where the ground layer section  101  is sandwiched between the conductive layer sections  103  and the power-source layer section  102  may be employed.  
     SIXTH EMBODIMENT  
      This embodiment uses a coupling body which has a pure resistor and a capacitor connected in parallel, or a coupling body which uses a capacitor in place of the coupling resistor section  107 .  FIG. 17  illustrates how it is.  
      As illustrated in  FIG. 17 , the conductive layer sections  103  are coupled together by good conductors  952  and coupling bodies  971 .  
      In a case where an insulator is used as the coupling body  971 , the “coupling body which uses only a capacitor” couples the conductive layer sections  103 . In a case where one having a certain resistance is used as the coupling body  971 , the “coupling body which has a capacitor and a resistor connected in parallel” couples the conductive layer sections  103 .  
      Particularly, in the latter case, if “the time constant C′R′ of the capacitance C′ of the capacitor and a resistance R′” is so set as to be equal to “the time constant (C 1 +C 2 )R 2  of the combined capacitance (C 1 +C 2 ) of the capacitance C 1  (C in  FIG. 2 ) of the ground layer section  101  and the conductive layer sections  103 , the capacitances C 2  (C in  FIG. 2 ) of the conductive layer sections  103  and the power-source layer section  102 , and the resistor R 2 ” in a case referring to  FIG. 2 , the entire communication unit  100  becomes a network where impedances which keep the same frequency character are coupled. Accordingly, the frequency dependency is eliminated, which brings about an advantage such that the disruption of a waveform to be transmitted to the adjoining conductive layer sections  103  can be eliminated.  
     SEVENTH EMBODIMENT  
      In the above-described embodiments, it is assumed that the power source is a positive power source, the electric potential of the power-source layer section  102  to the ground layer section  101  is positive, and the pull resistor section  104  pulls up electric potential, but the relationship between positive and negative may be inverted. That is, the power source is a negative power source, and the pull resistor section  104  pulls down electric potentials.  
      In the above-described embodiments, the communication element lets a current to flow between the ground layer section  101  and the conductive layer sections  103  to change the electric potentials of the conductive layer sections  103 , but the current may be allowed to flow between the power-source layer section  102  and the conductive layer sections  103  to change the electric potentials of the conductive layer sections  103 .  
      In addition, instead of filling a member with a predetermined resistivity as the pull resistor section  104 , the pull resistor may be prepared in the communication element, and appropriately couple the individual layers.  
      Further, a sheet-like member whose resistivity changes locally may also be used as the pull resistor section  104 . In this case, the average resistivity of an area corresponding to the pull resistor section  104  is a predetermined resistivity, and the average resistivity of the other areas are set extremely high (almost close to that of an insulator).  
     INDUSTRIAL APPLICABILITY  
      As explained above, the invention can provide a sheet-like communication unit that has a plurality of communication elements which are embedded in the communication unit, and transmits information as the communication elements communicate with neighboring communication elements to for a network.  
      This application claims priorities based on the following eleven Japanese Patent Applications, all of the disclosures of those eleven basic applications and the disclosure of the “Patent Literature 1” shall be incorporated in this application. 
      (1) Japanese Patent Application No. 2003-174076     (2) Japanese Patent Application No. 2003-189133     (3) Japanese Patent Application No. 2003-189117     (4) Japanese Patent Application No. 2003-284562     (5) Japanese Patent Application No. 2003-284582     (6) Japanese Patent Application No. 2003-284563     (7) Japanese Patent Application No. 2003-284541     (8) Japanese Patent Application No. 2003-284584     (9) Japanese Patent Application No. 2003-323300     (10) Japanese Patent Application No. 2004-107875     (11) Japanese Patent Application No. 2004-107876