WO2012144252A1 - Electrode structure for electric field communication - Google Patents

Abstract

The purpose of the present invention is to provide an electrode structure for electric field communication having good communication characteristics and capable of preventing both an increase in the number of components and an increase in the size of the electrode structure itself. The electrode structure (13) for electric field communication has a first electrode (131) connected to a fixed potential and a second electrode (132) arranged so as to face the first electrode (131) and having a power supply point (a) disposed therein. The second electrode (132) becomes the electrode adjacent to a transmission medium. The electrode structure (13) for electric field communication is characterized by the second electrode (132) being connected to the first electrode (131) at a site (b) separated by at least a prescribed distance from the power supply point (a) such that the electrical resistance along the length of the current path is at least a prescribed value.

Description

Electrode structure for electric field communication

The present invention relates to an electrode structure for electric field communication applicable to electric field communication for transmitting and receiving information through a transmission medium such as a human body.

In recent years, an electric field communication system for transmitting and receiving information via a medium such as a human body has been proposed. This electric field communication system includes a transmission medium such as a human body, a transmitter that generates an electric field corresponding to an information signal, and a receiver that detects a potential variation of the transmission medium and demodulates the information signal. The transmitter electrode and the transmission medium, and the receiver electrode and the transmission medium are capacitively coupled, and communication is performed between the transmitter and the receiver by this capacitive coupling.

A parallel plate structure has been proposed as an electrode (electrode structure for electric field communication) of a transceiver used for electric field communication (see, for example, Patent Document 1). This electrode structure for electric field communication has two flat conductors arranged substantially in parallel and an insulator arranged between them, and a ground potential is applied to one flat conductor and a signal potential is applied to the other flat conductor. Is to be given. When a transmission medium such as a human body comes close to a flat conductor to which a signal potential is applied, a potential fluctuation corresponding to the signal potential occurs in the transmission medium, and communication becomes possible.

JP 2007-174570 A

By the way, in the parallel plate electrode described above, the electric field between the flat conductors is very large, so even if a human body is close to the other flat conductor, almost no electric field is generated on the transmission medium side, and the potential fluctuation of the transmission medium occurs. Becomes extremely small. When the potential fluctuation of the transmission medium is reduced, the signal intensity received by the receiving electrode is also reduced, and communication errors frequently occur. Although a communication error can be reduced by providing a matching circuit on the transmission side, in this case, the matching circuit increases the number of parts of the transmission side device and increases the manufacturing cost. Further, if the distance between the flat conductors is increased, it is expected that there is an effect that the loss to the COLD electrode side to which the ground potential is applied can be suppressed, but there is a problem that the electrode structure becomes large.

The present invention has been made in view of the above points, and an object of the present invention is to provide an electrode structure for electric field communication having good communication characteristics, which can prevent an increase in the number of parts and an increase in size of the electrode structure itself.

The electrode structure for electric field communication according to the present invention includes a first electrode connected to a fixed potential, and a second electrode arranged to face the first electrode and provided with a feeding point, and the second electrode In the electrode structure for electric field communication in which is an electrode adjacent to the transmission medium, the second electrode has the first electrode at a location away from the feeding point by a predetermined distance or more so that the electric resistance of the current path length is a predetermined value or more. It is connected to an electrode.

According to this configuration, since the second electrode is connected to the first electrode at a location that is a predetermined distance or more away from the feeding point so that the electric resistance of the current path length is a predetermined value or more, the number of parts is increased. In addition to preventing the increase in size of the electrode structure itself, an electrode structure for electric field communication with good communication characteristics can be realized.

In the electrode structure for electric field communication according to the present invention, the first and second electrodes have a rectangular shape with the same outer region, and the feeding point of the second electrode is provided at the end of the first side of the square. The first electrode may be connected to any part of the second side facing the first side or the entire second side.

In the electrode structure for electric field communication according to the present invention, each of the first and second electrodes has a structure in which one rectangular electrode is bent at an intermediate position in the longitudinal direction, and the first electrode and the first electrode are bent at a bent portion. Two electrodes may be connected.

In the electrode structure for electric field communication according to the present invention, the first electrode is constituted by a flat plate conductor extending in a region facing the second electrode, and the second electrode is constituted by a meander shape or other fine line pattern. May be.

According to the present invention, it is possible to prevent an increase in the number of parts and prevent an increase in the size of the electrode structure itself, thereby providing an electrode structure for electric field communication with good communication characteristics.

It is a schematic diagram which shows the structural example of the electric field communication system in which the electrode structure for electric field communication which concerns on Embodiment 1 is used. 1 is a perspective view showing a configuration of an electrode structure for electric field communication according to Embodiment 1. FIG. 1 is a plan view showing a configuration of an electric field communication electrode structure according to Embodiment 1. FIG. It is a schematic diagram which shows a simulation model. It is a perspective view which shows the electrode structure (model B) for electric field communication of a parallel plate structure. It is a perspective view which shows the electrode structure (model C) for electric field communication of a parallel plate structure. It is a table | surface which shows a simulation result.

Hereinafter, the configuration of the electrode structure for electric field communication according to the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic diagram showing a configuration example of an electric field communication system in which the electric field communication electrode structure according to the present embodiment is used. The electric field communication system shown in FIG. 1 includes a transmitter 1 that modulates an information signal to generate an electric field corresponding to the information signal, and a transmission medium 2 such as a human body that transmits the information signal by the electric field generated by the transmitter 1. And a receiver 3 that demodulates an information signal by detecting a potential fluctuation that becomes an electric field propagating through the transmission medium 2. The transmitter 1 may be a transceiver having a reception function, and the receiver 3 may be a transceiver having a transmission function. Here, in order to simplify the description, only one-way communication will be described, but the present invention can be easily applied to two-way communication.

The transmitter 1 is a control unit 11 such as a computer that performs signal transmission control, a transmission unit 12 that modulates an information signal from the control unit 11 to generate an RF signal, and an RF signal from the transmission unit 12 And an electric field communication electrode structure 13 for generating an electric field. The transmitter 12 and the electric field communication electrode structure 13 are connected via a coaxial cable L. The control unit 11 is configured to supply the information signal in the intermediate frequency band to the transmission unit 12 and to supply the power supply potential Vdd and the ground GND that is a fixed potential. The transmission unit 12 includes a modulation circuit (not shown) and the like, and is configured to be able to generate an RF signal by modulating an information signal (IF) from the control unit 11. The transmitter 12 generates an RF signal and supplies the RF signal to the electric field communication electrode structure 13 through the coaxial cable L. The electrode structure 13 for electric field communication includes a first electrode 131 to which a ground potential (GND) as a fixed potential is applied, a second electrode 132 to which an RF signal (signal potential) from the control unit 11 is fed, and a first electrode 131 and an insulator 133 interposed between the second electrode 132 and an electric field corresponding to the RF signal from the transmitter 12 can be generated.

The transmission medium 2 is a medium having predetermined conductivity such as a human body. When the transmission medium 2 approaches (or comes into contact with) the second electrode 132 of the electrode structure 13 for electric field communication, an electrostatic capacity is generated between the second electrode 132 and the transmission medium 2, and the second electrode 132 and the transmission medium 2 Are capacitively coupled. For this reason, when an RF signal is supplied to the second electrode 132, the potential of the transmission medium 2 varies according to the signal potential of the RF signal.

The receiver 3 includes a first electrode 31 for forming a capacitance with the transmission medium 2 and a second electrode 32 disposed so as to oppose the first electrode 31. When the first electrode 31 approaches (or comes into contact with) the transmission medium 2, an electrostatic capacitance is generated between the transmission medium 2 and the first electrode 31, and the transmission medium 2 and the first electrode 31 are capacitively coupled. When the potential of the transmission medium 2 fluctuates in accordance with the signal potential of the RF signal, the potential of the first electrode 31 that is capacitively coupled also fluctuates in the same manner. Therefore, the potential fluctuation of the first electrode 31 is detected and a demodulation circuit (not shown) is used. By demodulating, an information signal can be received.

FIG. 2 is a perspective view showing the configuration of the electrode structure 13 for electric field communication according to the present embodiment. FIG. 3 is a plan view showing the configuration of the electric field communication electrode structure 13 according to the present embodiment. 3A mainly shows a configuration of the first electrode 131, FIG. 3B mainly shows a configuration of the second electrode 132, and FIG. 3C shows a cross section taken along the arrow AA in FIGS. As shown in FIGS. 1 to 3, the electric field communication electrode structure 13 includes a first electrode 131 formed of a flat conductor, a second electrode 132 disposed so as to face the first electrode 131, and a first electrode 131. The insulator 133 is disposed between the first electrode 131 and the second electrode 132.

The first electrode 131 is a flat electrode having a substantially rectangular planar shape, and is configured to be supplied with a ground potential (GND). The potential applied to the first electrode 131 is not limited to the ground potential (GND) as long as it is a fixed potential. The planar shape of the first electrode 131 is not limited to a substantially rectangular shape, and may be various shapes such as a substantially circular shape and a substantially polygonal shape. The first electrode 131 is not limited to a so-called solid electrode, and may be formed in a desired pattern.

The second electrode 132 is formed in a current path length (in this example, a meander shape) with an electrical resistance value equal to or greater than a predetermined value, and the RF from the transmitter 12 is fed to a feeding point a provided at one end of the current path length. The signal is fed. More specifically, the second electrode 132 is an outer region that is disposed away from the first electrode 131 in a direction (vertical direction) perpendicular to the main surface of the first electrode 131 so as to face the first electrode 131. Is formed of a conductor having a rectangular meander pattern substantially the same as that of the first electrode 131.

The meander pattern of the second electrode 132 is composed of a plurality of straight portions that are substantially parallel to the side e1 that forms the rectangle of the outer region, and a plurality of folded portions that connect adjacent straight portions to each other. The first straight portion extending from the feeding point a is connected to the first folded portion at the end opposite to the feeding point a (side e2 side), and the first folded portion is connected to the first straight portion. It is connected to the adjacent second straight line portion. Further, the second straight line portion is connected to the second folded portion at the end on the feeding point a side (side e3 side), and the second folded portion is connected to the third straight line portion. The meander pattern is configured by providing such a repeating pattern of straight and folded portions up to the vicinity of the side e4.

As in the meander pattern described above, the electric resistance of the second electrode 132 can be made higher than that of the flat conductor by making the second electrode 132 a thin line pattern having a predetermined current path length. The thin line pattern is not limited to the meander pattern, and other patterns such as a spiral pattern may be used. The length of the thin line pattern serving as the current path length can be appropriately set according to a desired electric resistance value or the like.

The second electrode 132 is connected to the first electrode 131 at a predetermined distance (point or straight line) from the feeding point a. More specifically, the second electrode 132 is connected to the first electrode 131 in a region b near the end point on the opposite side to the feeding point a of the meander pattern. In other words, the second electrode 132 is connected to the first electrode 131 in the region b near the side e4 facing the side e1 on the feeding point a side. However, the first electrode 131 and the second electrode 132 may be connected at least at one point, and may not be connected in a region having a range such as the region b. Further, if the position of the connection point with the first electrode 131 is far from the power supply point a so that the electrical resistance value from the power supply point a to the connection point is not less than a predetermined value, the end point on the side opposite to the power supply point a It is not limited to the vicinity. However, when the connection point is close to the feeding point a, the electrical resistance of the current path is reduced and the transmission loss is increased. For this reason, the position of the connection point and the value of the electric resistance of the current path are set so that the transmission loss is within an allowable range. In this way, the second electrode 132 is configured by a thin line pattern having a predetermined current path length, and is connected to the first electrode 131 in the region b at a predetermined distance from the feeding point a. The electrode structure 13 can be realized.

The first electrode 131 and the second electrode 132 are a substantially rectangular single electrode having a flat plate area constituting the first electrode 131 and a fine line pattern area constituting the second electrode 132. It is configured to be bent at an intermediate position in the longitudinal direction that becomes a boundary with the region. By bending the single electrode in this manner, an electrode structure in which the first electrode 131 and the second electrode 132 are connected in the region b can be realized. However, the separate first electrode 131 and second electrode 132 may be connected.

The insulator 133 is configured to insulate the first electrode 131 and the second electrode 132 and to keep the distance between the first electrode 131 and the second electrode 132 substantially constant. For example, when the thickness of the insulator 133 is 3 mm, the distance between the first electrode 131 and the second electrode 132 can be maintained at about 3 mm. Note that the insulator 133 may be omitted as long as the first electrode 131 and the second electrode 132 can be separated and insulated. For example, a spacer may be disposed under the second electrode 132 and insulation may be realized by air.

FIG. 4 is a schematic diagram showing a simulation model for confirming the communication characteristics of the electrode structure 13 for electric field communication. Transmission medium 2 corresponding to a human body using electric field communication electrode structure 13 as an electrode (floor electrode) of transmitter 1, having an electric conductivity of 0.62 S / m, a relative dielectric constant of 162.5, and a height of 1.4 m. A simulation was performed assuming that As shown in FIG. 4, the electrode structure of the receiver 3 is a parallel plate structure including a first electrode 31 made of a flat plate conductor and a second electrode 32 made of a flat plate conductor. Further, the distance between the first electrode 131 and the second electrode 132 of the electrode structure 13 for electric field communication was set to 3 mm (model A).

As a comparative example, a similar simulation was performed using an electric field communication electrode structure (floor electrode) having a structure different from that of the electric field communication electrode structure 13. FIG. 5 is a perspective view showing a configuration of an electric field communication electrode structure 14a as a comparative example. The electrode structure for electric field communication 14a is a parallel plate structure including a first electrode 141a made of a flat plate conductor and a second electrode 142a made of a flat plate conductor. The distance between the first electrode 141a and the second electrode 142a was 3 mm (model B). In addition, when the first electrode 141a and the second electrode 142a are connected in the electric field communication electrode structure 14a having a parallel plate structure, the first electrode 141a and the second electrode 142a are not connected because communication is impossible.

FIG. 6 is a perspective view showing a configuration of an electrode structure for electric field communication 14b as a comparative example. The electrode structure for electric field communication 14b is a parallel plate structure including a first electrode 141b made of a flat plate conductor and a second electrode 142b made of a flat plate conductor. The distance between the first electrode 141b and the second electrode 142b was 100 mm (model C). Similarly, in the electric field communication electrode structure 14b, the first electrode 141b and the second electrode 142b are not connected.

Further, the same simulation was performed using the electric field communication electrode structure in which the first electrode 131 and the second electrode 132 of the electric field communication electrode structure 13 are not connected. Except for the point that the first electrode 131 and the second electrode 132 are not connected, the configuration was the same as the electrode structure for electric field communication 13 (model D).

FIG. 7 is a table showing simulation results. In FIG. 7, the larger the value in the column of transmission loss (S parameter S21), the smaller the transmission loss. As shown in FIG. 7, in the model A corresponding to the electric field communication electrode structure 13 of the present embodiment, the impedance value is 15Ω or more, and the transmission loss is the smallest among the models A to D. The transmission loss is minimized in the model A because the first electrode 131 and the second electrode 132 are connected so that the electric resistance of the current path length is equal to or greater than a predetermined value.

On the other hand, model B with a parallel plate structure has a small impedance value of 0.37Ω and a large transmission loss. In the model C of the parallel plate structure, the impedance value is as high as 13.7Ω, and the transmission loss is suppressed to some extent. However, the electrical resistance component occupying the impedance value is sufficiently small. Further, the distance between the first electrode 141b and the second electrode 142b is as extremely large as 100 mm. In model D in which the first electrode and the second electrode are not connected, the impedance value is as high as 12.0, but the transmission loss is large.

Comparing model A corresponding to the case of using the electric field communication electrode structure 13 and model B corresponding to the case of using the general electric field communication electrode structure 14a, the transmission loss of the model A is improved by about 8 dB. . This means that the received electric field intensity received by the first electrode 31 of the receiver 3 in the model A is about 2.5 times that in the model B. Thus, good communication characteristics can be realized by greatly increasing the received electric field strength.

Model C corresponding to the case where the electrode structure for electric field communication 14b is used can achieve a certain degree of communication characteristics. However, since the distance between the first electrode 141b and the second electrode 142b is large (100 mm), the electrode structure for electric field communication is The problem that it will enlarge will arise. Also, the communication characteristics do not reach that of model A. In other words, the model A using the electric field communication electrode structure 13 can achieve better communication characteristics than the model C, and the electric field communication electrode structure can be made thinner and smaller than the model C. .

The communication characteristics of model D are worse than model A. From comparison between model A and model D, it can be seen that a short circuit between the first electrode 131 and the second electrode 132 is necessary to improve the communication characteristics. However, in a parallel plate structure such as the electric field communication electrode structure 14a and the electric field communication electrode structure 14b, electric field communication cannot be performed even if the first electrode and the second electrode made of a flat plate conductor are connected. This is because the electric resistance of the flat conductor itself constituting the second electrode is extremely low, and when the first electrode and the second electrode are connected, the second electrode is strongly influenced by the first electrode and the electric field due to the RF signal is generated. This is thought to be due to almost no generation. That is, it is important to increase the electric resistance of the current path by configuring the second electrode with a fine line pattern or the like.

Note that, when a material with low conductivity is used for the second electrode, the electrical resistance of the current path is increased, but in this case, the transmission loss is not improved. For example, two flat electrodes are formed using a material such as a silver paste (conductive paste in which silver particles and resin are mixed) having a lower conductivity than copper used in ordinary printed circuit boards. Even if a parallel plate structure in which the two electrodes are short-circuited is used, the transmission loss is not improved. From this, by using a material with high conductivity (for example, a material having a conductivity of 10 ⁵ (S / m) or more: copper, aluminum, silver, gold, and alloys thereof, etc.) and devising an electrode pattern, etc. It can be said that increasing the electrical resistance is important.

From the above results, the electrode structure for electric field communication in which the second electrode 132 is connected to the first electrode 131 at a location b that is a predetermined distance or more away from the feeding point a so that the electric resistance of the current path length is a predetermined value or more. 13 (model A) shows that good communication characteristics can be realized even if the thickness is thin.

As described above, in the electrode structure for electric field communication according to the present invention, the first electrode and the second electrode are connected at a location away from the feeding point by a predetermined distance or more so that the electric resistance of the current path becomes a predetermined value or more. As a result, an electrode structure for electric field communication with good communication characteristics was realized.

In addition, this invention is not limited to description of the said embodiment, It can change suitably in the aspect in which the effect is exhibited, and can be implemented. For example, in the above-described embodiment, the electrical resistance is expressed as an electrical parameter of the current path, but it can also be expressed by an impedance including the electrical resistance. In addition, the structures, methods, and the like described in the above embodiments can be combined as appropriate. In addition, the present invention can be implemented with appropriate modifications without departing from the scope of the present invention.

The electrode structure for electric field communication of the present invention is useful as an electrode for a transmitter used in an electric field communication system, for example.

This application is based on Japanese Patent Application No. 2011-093050 filed on Apr. 19, 2011. All this content is included here.

Claims (4)

An electric field having a first electrode connected to a fixed potential and a second electrode disposed opposite to the first electrode and provided with a feeding point, the second electrode being an electrode adjacent to the transmission medium In the communication electrode structure,
The electrode structure for electric field communication, wherein the second electrode is connected to the first electrode at a position separated from the feeding point by a predetermined distance or more so that an electric resistance of a current path length becomes a predetermined value or more. The first and second electrodes have a rectangular shape with the same outer region, and a feeding point of the second electrode is provided at an end of the first side of the square, and a second facing the first side. 2. The electrode structure for electric field communication according to claim 1, wherein the electrode structure is connected to the first electrode at any location on the side or the entire second side. The first and second electrodes have a structure in which one rectangular electrode is bent at an intermediate position in the longitudinal direction, and the first electrode and the second electrode are connected at a bent portion. 3. The electrode structure for electric field communication according to claim 1, wherein the electrode structure is for electric field communication. The first electrode is composed of a flat plate conductor extending in a region facing the second electrode,
4. The electrode structure for electric field communication according to claim 1, wherein the second electrode is formed in a meander shape or other fine line pattern. 5.

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