JP4805367B2 - Electrode adjustment system - Google Patents

Description

  The present invention relates to a technique for transmitting and receiving information by detecting an electric field based on information to be transmitted that is transmitted through an electric field transmission medium.

  There has been proposed an electric field communication device that induces an electric field in an electric field transmission medium such as a human body and performs data communication using the induced electric field (see Patent Document 1).

  FIG. 11 is a diagram showing a configuration of electrodes of a conventional electric field communication device, and shows electrodes 101 and 102 for electric field communication and a differential amplifier circuit 103. By using the differential amplifier circuit 103, the difference between the signal components can be amplified and the noise component can be canceled.

JP 2001-352290 A

  However, if the signal strength or noise level changes due to changes in the installation conditions or location, and the noise (noise component) is amplified without being canceled out, the electrode size and configuration change, the reception sensitivity of the electric field communication device There is a problem that it is necessary to cope with this by adjusting the cost and time and cost.

  The present invention has been made in view of the above, and an object thereof is to easily cope with changes in signal strength and noise level in an electric field communication device.

  An electrode adjustment system according to the present invention is an electrode adjustment system disposed in an electric field communication device that performs electric field communication by inducing an electric field in an electric field transmission medium, the first and second electrodes for electric field communication, Determining a noise level based on a differential amplifier circuit that amplifies a difference between signals input from the first and second electrodes and an output of the differential amplifier circuit when no signal is input to the first electrode; Determining means for determining a signal level based on an output of the differential amplifier circuit when a signal is input to the first electrode; and when the noise level and the signal level do not satisfy predetermined criteria, the first and second And changing means for changing the capacitance between the electrodes.

  The electrode adjustment system includes a plurality of electrodes configured in multiple layers, and the changing unit selects the first and second electrodes from the plurality of electrodes, respectively.

  In the electrode adjustment system, the first and second electrodes are divided into a plurality of parts, and the changing unit selects a part to be used as the first and second electrodes from the plurality of parts. It is characterized by that.

  In the electrode adjustment system, a variable capacitor is provided between the first and second electrodes, and the changing unit adjusts the variable capacitor.

  In the electrode adjustment system, the changing means moves at least one of the first and second electrodes.

  In the above electrode adjustment system, a third electrode disposed in the vicinity of one of the first and second electrodes, an application means for applying a predetermined potential to the third electrode, and a differential amplifier circuit And adjusting means for adjusting a predetermined potential based on the output of.

  In the electrode adjustment system, a shield to which a predetermined potential is applied is provided in a transmission line connecting the first and second electrodes and the differential amplifier circuit.

  In the present invention, the first and second electrodes for electric field communication are connected to the differential amplifier circuit, and the noise level and signal level are determined based on the output of the differential amplifier circuit. By changing the capacitance between the first and second electrodes when the signal does not meet a predetermined standard, an appropriate noise level and signal level can be obtained without changing the electrodes or adjusting the reception sensitivity. A possible electrode adjustment system can be provided.

  As a means for changing the capacitance between the first and second electrodes, an electrode to be used as the first and second electrodes is selected from a plurality of electrodes configured in multiple layers, and is used from an electrode divided into a plurality of portions. There are means such as selecting a portion, providing a variable capacitor between the first and second electrodes, and physically moving the first and second electrodes.

  Thus, according to the present invention, it is possible to easily cope with changes in signal intensity and noise level in the electric field communication device.

It is a block diagram which shows the structure of the electrode adjustment system in 1st Embodiment. FIG. 6A is a graph for explaining a situation when noise is not detected at the threshold value Vth, and FIG. 6B is a graph for explaining a situation when a signal is detected at the threshold value Vth. It is a block diagram which shows the structure of the electrode adjustment system in 2nd Embodiment. It is a block diagram which shows the structure of the electrode adjustment system in 3rd Embodiment. It is a block diagram which shows the structure of the electrode adjustment system in 4th Embodiment. FIG. 6 is a side view of the electrode of FIG. 5. It is a block diagram which shows the structure of the electrode adjustment system in 5th Embodiment. It is a block diagram which shows the structure of another electrode adjustment system in 5th Embodiment. It is a schematic diagram which shows the example of the shape of an electrode. It is a schematic diagram which shows another example of the shape of an electrode. It is a schematic diagram which shows the structure of the electrode of the conventional electric field communication apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an electrode adjustment system in the first embodiment. The electrode adjustment system shown in the figure includes a plurality of electrodes 11A, 11B, 12A, 12B configured in multiple layers, a selection circuit 13, a differential amplifier circuit 14, a determination circuit 15, and an MPU (microprocessing unit) 16. The electrode adjustment system is disposed in an electric field communication device that receives data by detecting an electric field induced in an electric field transmission medium adjacent to the electrodes 11A, 11B, 12A, and 12B.

  The selection circuit 13 selects the first and second electrodes from the electrodes 11A, 11B, 12A, and 12B, respectively. The electric field induced in the electric field transmission medium is detected by the selected first and second electrodes, and the signal is balanced and transmitted to the differential amplifier circuit 14. The output of the differential amplifier circuit 14 is input to a receiving unit of an electric field communication device (not shown).

  The determination circuit 15 determines whether or not the output of the differential amplifier circuit 14 satisfies desired signal strength and noise level. Based on the determination result of the determination circuit 15, the MPU 16 controls the selection circuit 13, and the electrodes 11A, 11B, 12A used as the first and second electrodes so as to satisfy the desired signal intensity and noise level. 12B is determined. When the selection circuit 13 changes the combination of the electrodes 11A, 11B, 12A, and 12B, the distance between the electrodes to be used is changed and the capacitance between the electrodes is changed. Accordingly, the signal intensity and the noise level are changed accordingly.

  Next, an operation in which the determination circuit determines the signal strength and the noise level will be described.

  First, the determination circuit 15 determines the noise level when there is no signal. The determination of the noise level is performed by comparing the output of the differential amplifier circuit 14 when there is no signal with a comparator and checking whether noise is detected at the threshold value Vth. FIG. 2A is a diagram illustrating a state where no noise is detected at the threshold value Vth. As shown in the figure, when the noise amplitude is smaller than the threshold value Vth, it is determined that the noise level with respect to the threshold value Vth is satisfied. When the noise amplitude is equal to or greater than the threshold value Vth, the noise level criterion is not satisfied. Therefore, feedback to the selection circuit 13 is performed to select another electrode combination, and the noise level is determined again.

  If no noise is detected at the threshold Vth, the signal strength is determined. The signal strength is determined by comparing the output of the differential amplifier circuit 14 when the standard signal is input with a comparator and checking whether the standard signal can be detected at the threshold Vth. The standard signal is, for example, several pulses, and the pulses are input to the electric field transmission medium close to the selected electrode. If the standard signal cannot be detected, another electrode combination is selected and the process returns to the noise level determination again. As shown in FIG. 2B, when a standard signal can be detected at the threshold value Vth, the combination of electrodes at that time is employed.

  Therefore, according to the present embodiment, a plurality of electrodes 11A, 11B, 12A, and 12B configured in multiple layers are provided, the signal strength and noise level are determined by the determination circuit 15, and the determination results are selected by the selection circuit 13. Therefore, the selection circuit 13 can select an electrode that can obtain an appropriate signal strength and noise level, and there is no need to replace the electrode or adjust the reception sensitivity.

[Second Embodiment]
FIG. 3 is a block diagram showing the configuration of the electrode adjustment system according to the second embodiment. The electrode adjustment system in the second embodiment differs from the electrode adjustment system in the first embodiment in the configuration of the electrodes. The electrode adjustment system shown in the figure includes first electrodes 31A, 31B, 31C, and 31D and second electrodes 32A, 32B, 32C, and 32D obtained by dividing opposing electrodes into a plurality of portions.

  In the electrode adjustment system in the second embodiment, as in the first embodiment, the determination circuit 35 determines the signal intensity and the noise level based on the output of the differential amplifier circuit 34, and the determination result is sent to the MPU 36. The selection circuit 33 selects the first electrodes 31A, 31B, 31C, and 31D and the second electrodes 32A, 32B, 32C, and 32D so that the signal intensity and the noise level satisfy predetermined criteria by feedback. The electrode to be selected is not limited to one part from the first and second electrodes, and a plurality of parts may be selected.

  Depending on the combination of the electrodes selected by the selection circuit 33, the areas of the first electrode and the second electrode are changed, and the capacitance between the electrodes is changed. Accordingly, the signal intensity and the noise level are changed accordingly.

  Whether or not the selected electrode satisfies the criteria of signal intensity and noise level is determined by comparing the threshold value Vth with the signal intensity and noise level by the determination circuit 35 as in the first embodiment.

  Therefore, according to the present embodiment, the first electrodes 31A, 31B, 31C, 31D and the second electrodes 32A, 32B, 32C, 32D obtained by dividing the opposed electrodes into a plurality of portions are provided. The determination circuit 35 determines the signal intensity and the noise level, and feeds back the determination result to the selection circuit 33, so that the selection circuit 33 can select an electrode that can obtain an appropriate signal intensity and noise level.

[Third Embodiment]
The electrode adjustment system in the third embodiment is different from the first and second embodiments in that an electrode to be used is not selected. Instead of selecting the electrodes and changing the capacitance between the electrodes, a variable capacitance is connected between the electrodes to adjust the capacitance between the electrodes.

  FIG. 4 is a block diagram illustrating a configuration of an electrode adjustment system according to the third embodiment. The electrode adjustment system shown in the figure includes a first electrode 41 and a second electrode 42 arranged to face each other, and a variable capacitor 47 is connected between the first electrode 41 and the second electrode 42. To do. The first electrode 41 and the second electrode 42 are connected to the differential amplifier circuit 44. The determination circuit 45 determines signal strength and noise level based on the output of the differential amplifier circuit 44. The determination result of the determination circuit 45 is fed back to the MPU 46, and the MPU 46 changes the variable capacitor 47 by controlling the adjustment circuit 43 so that the signal intensity and the noise level satisfy predetermined criteria based on the determination result. By changing the variable capacitor 47, the signal intensity and the noise level change.

  Whether or not the signal strength and noise level criteria are satisfied is determined by the determination circuit 45 comparing the threshold value Vth with the signal strength and noise level as in the first embodiment.

  Therefore, according to the present embodiment, the variable capacitor 47 is provided between the first and second electrodes 41 and 42, the signal strength and the noise level are determined by the determination circuit 45, and the determination result is sent to the adjustment circuit 43. By feeding back, the adjustment circuit 43 can set a variable capacitor that can obtain appropriate signal strength and noise level.

[Fourth Embodiment]
The electrode adjustment system in the fourth embodiment adjusts the capacitance between the electrodes by physically moving the electrodes.

  FIG. 5 is a block diagram illustrating a configuration of an electrode adjustment system according to the fourth embodiment. The electrode adjustment system shown in the figure includes a first electrode 51 and a second electrode 52 arranged to face each other, and has a control circuit 53 that moves the position of the first electrode 51 left and right in the drawing. . The first electrode 51 and the second electrode 52 are connected to the differential amplifier circuit 54. The determination circuit 55 determines signal strength and noise level based on the output of the differential amplifier circuit 54. The determination result of the determination circuit 55 is fed back to the MPU 56, and the MPU 56 controls the control circuit 53 to change the position of the first electrode 51.

  FIG. 6 is a side view of the first and second electrodes 51 and 52. The control circuit 53 moves the first electrode 51 in the horizontal direction to adjust the area overlapping with the second electrode 52. By moving the first electrode 51, the overlapping area of the first and second electrodes 51 and 52 is changed, and the capacitance between the electrodes is changed. Accordingly, the signal intensity and the noise level are changed accordingly.

  Whether or not the signal strength and noise level criteria are satisfied is determined by the determination circuit 55 comparing the threshold value Vth with the signal strength and noise level as in the first embodiment.

  Note that the area where the first and second electrodes 51 and 52 overlap may be adjusted by winding the first electrode 51 like a roll screen. Alternatively, the capacitance between the electrodes may be changed by moving the first electrode 51 in the vertical direction and adjusting the distance between the first and second electrodes 51 and 52. Of course, the second electrode 52 may be moved, or both the first and second electrodes 51 and 52 may be moved.

  Therefore, according to the present embodiment, the control circuit 53 that slides the first electrode 51 is provided, the signal strength and the noise level are determined by the determination circuit 55, and the determination results are fed back to the control circuit 53. The control circuit 53 can adjust the overlapping state of the first and second electrodes 51 and 52 that can obtain appropriate signal strength and noise level.

[Fifth Embodiment]
FIG. 7 is a block diagram illustrating a configuration of an electrode adjustment system according to the fifth embodiment. The electrode adjustment system shown in the figure includes a third electrode 78 on the lower surface of the second electrode 72 of the electrode adjustment system according to the third embodiment. The third electrode 78 includes an adjustment circuit. A fixed potential is applied by 73. Here, in the third embodiment, the electrode 78 for applying a fixed potential is arranged on the lower surface of the electrode, but it is of course possible to apply the same to the electrode adjustment system in the other embodiments.

  When signals are balanced and transmitted to the differential amplifier circuit 74 by the first and second electrodes 71 and 72, the signal input to the differential amplifier circuit 74 may greatly fluctuate depending on the installation environment and exceed the allowable range. . Therefore, in the present embodiment, by applying a fixed potential to the third electrode 78, the fluctuation of the potential of the first and second electrodes 71 and 72 is suppressed, and the signal input to the differential amplifier circuit 74 is reduced. Reduce fluctuations. The adjustment circuit 73 refers to the determination result of the determination circuit 75 and applies a fixed potential to the third electrode 78 so that the unnecessary signal intensity coupled to the first and second electrodes 71 and 72 is minimized.

  In addition, as shown in FIG. 8, a shield 79 may be attached to a cable connecting the electrodes 71 and 72 and the differential amplifier circuit 74, and a fixed potential may be applied by the adjustment circuit 73 as described above.

  The first to fifth embodiments have been described above using planar electrodes. However, as shown in FIG. 9, a grid-like electrode may be used, or, as shown in FIG. These electrodes may be used. In addition, an electrode having a different shape may be selected to adjust the signal intensity and the noise level.

11A, 11B, 12A, 12B, 31A, 31B, 32A, 32B, 41, 42, 51, 52, 71, 72, 78 ... Electrode 13, 33 ... Selection circuit 43, 73 ... Adjustment circuit 47 ... Variable capacitance 53 ... Control Circuits 14, 34, 44, 54, 74 ... Differential amplifier circuits 15, 35, 45, 55, 75 ... Determination circuits 16, 36, 46, 56 ... MPU
79 ... Shield 101, 102 ... Electrode 103 ... Differential amplifier circuit

Claims (7)

An electrode adjustment system disposed in an electric field communication device that performs electric field communication by inducing an electric field in an electric field transmission medium,
First and second electrodes for electric field communication;
A differential amplifier circuit for amplifying a difference between signals input from the first and second electrodes;
A noise level is determined based on an output of the differential amplifier circuit when no signal is input to the first electrode, and an output of the differential amplifier circuit when a signal is input to the first electrode. A determination means for determining a signal level based on;
Changing means for changing a capacitance between the first and second electrodes when the noise level and the signal level do not satisfy a predetermined standard;
An electrode adjustment system comprising: Having a plurality of electrodes configured in multiple layers;
The electrode adjustment system according to claim 1, wherein the changing unit selects the first and second electrodes from the plurality of electrodes. The first and second electrodes are divided into a plurality of parts,
2. The electrode adjustment system according to claim 1, wherein the changing unit selects a part to be used as the first and second electrodes from the plurality of parts. A variable capacitor is provided between the first and second electrodes,
The electrode adjustment system according to claim 1, wherein the changing unit adjusts the variable capacitance.   2. The electrode adjustment system according to claim 1, wherein the changing means moves at least one of the first and second electrodes. A third electrode disposed in the vicinity of one of the first and second electrodes;
Applying means for applying a predetermined potential to the third electrode;
Adjusting means for adjusting the predetermined potential based on the output of the differential amplifier circuit;
The electrode adjustment system according to claim 1, comprising:   The electrode adjustment system according to claim 6, further comprising: a shield to which the predetermined potential is applied to a transmission path connecting the first and second electrodes and the differential amplifier circuit.

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