JP4717157B2 - Communications system - Google Patents

Description

  The present invention relates to a communication system that performs transmission and reception via a transmission medium such as a human body.

With recent technological development, a communication method using an electric field induced in a transmission medium such as a human body has been proposed as a completely new communication method (Patent Document 1). In such a communication system, there is a configuration disclosed in Patent Document 2 in particular as a configuration of a resonance circuit. In this communication system, a receiver has a receiving electrode that receives a signal generated from a signal source, and a resonance circuit that extracts a signal having a predetermined frequency. This resonance circuit is composed of an air-core coil and a chip capacitor, and one end of the air-core coil is connected to a receiving electrode facing the human body.
Japanese National Patent Publication No. 11-509380 JP 2005-94466 A

  However, when the communication system disclosed in Patent Document 2 is mounted on a portable device typified by a cellular phone, communication cannot be performed because the human body and the reception electrode of the receiver are slightly separated from each other, or the communication carrier frequency There is a problem that communication is interrupted by noise close to (for example, noise generated by a mobile device).

  The present invention has been made in view of the above points, and provides a communication system that is free from malfunction due to noise and that can perform stable communication even when the distance between the transmission medium and the reception electrode is long. Objective.

The communication system of the present invention includes a transmitter that converts an information signal into an electric field and gives it to a transmission medium, and a receiver that detects the electric field and receives the information signal through the transmission medium. The receiver includes a receiving electrode facing the transmission medium, a primary coil connected to the receiving electrode, a secondary coil arranged so that a magnetic flux intersecting the primary coil is magnetically coupled, and A receiving circuit connected to a secondary coil , wherein the primary coil and the secondary coil are each configured in a spiral shape, and a capacitance between the primary coil and the secondary coil is a coil. It is characterized by capacitive coupling at two or more locations.

  According to this configuration, the effect of stabilizing the resonance frequency due to distributed-capacitance coupling and the effect of improving sensitivity due to magnetic coupling are exhibited, and very stable communication is possible. In other words, since the receiving electrode and the receiving circuit are two or more stages of distributed constant capacitive coupling, stable communication can be realized even if the distance between the transmission medium and the receiving electrode varies. In the method of directly connecting the receiving electrode disclosed in Patent Document 2 to the resonance circuit, there is a problem that communication is not possible because the transmission medium and the receiving electrode are slightly separated from each other. Therefore, even if the distance between the transmission medium and the receiving electrode varies, the resonance frequency is difficult to shift, and stable communication is possible. In more detail, the applicant of the present application described in Japanese Patent Application No. 2007-69265 compared the case where the receiving electrode is directly connected to the resonance circuit and the case where the inductor is capacitively coupled to the inductor in a distributed constant manner. All this content is included here. Also, with this configuration, compared to the case where the resonance frequency is broadened as a countermeasure against the resonance frequency shift, it is possible to perform communication with higher reliability without being affected by noise.

In the communication system of the present invention, it is preferable that the spiral primary coil and the spiral secondary coil are stacked. Further, in the communication system of the present invention, it is preferable that between the lines of one of the coils of the primary coil and the secondary coil in the same plane and the other coil is disposed.

  According to these configurations, since the coupling capacitance between the primary coil and the secondary coil is uniformly distributed in the coil, the effect of stabilizing the resonance frequency is very large, and more stable communication can be realized. it can.

  In the communication system of the present invention, it is preferable that the magnetic paths of the primary coil and the secondary coil are closed. According to this configuration, since the magnetic path is closed, it is not easily affected by electromagnetic noise coming from the surroundings, and has little influence on the peripheral circuits. As a result, even if it is very close to the peripheral circuit components, there is little influence of noise and the like, and a reduction in size and thickness can be realized without sacrificing communication performance.

The communication system of the present invention includes a transmitter that converts an information signal into an electric field and gives it to a transmission medium, and a receiver that detects the electric field and receives the information signal through the transmission medium. The receiver includes a receiving electrode facing the transmission medium, a primary coil connected to the receiving electrode, a secondary coil arranged so that a magnetic flux intersecting the primary coil is magnetically coupled, and A receiving circuit connected to a secondary coil , wherein the primary coil and the secondary coil are each configured in a spiral shape, and a capacitance between the primary coil and the secondary coil is a coil. Since the capacitive coupling is performed at two or more locations, no malfunction due to noise occurs, and stable communication can be performed even if the distance between the transmission medium and the reception electrode is increased.

(A), (b) is a schematic block diagram which shows the communication system which concerns on embodiment of this invention. (A)-(c) shows the specific structural example which implement | achieves the equivalent circuit in the receiver shown in FIG. (A)-(c) shows the specific structural example which implement | achieves the equivalent circuit in the receiver shown in FIG. (A)-(c) shows the specific structural example which implement | achieves the equivalent circuit in the receiver shown in FIG.

  In order to solve the problem of the technology disclosed in Patent Document 2, the inventor cannot communicate when the distance between the transmission medium and the reception electrode is increased, and malfunctions due to noise. Resonance of the receiver due to a change in capacitance between the transmission medium and the receiving electrode of the receiver facing the transmission medium is caused by the fact that communication is not possible when the distance between the transmission medium and the receiving electrode is increased. It was found that this is a shift of the resonant frequency in the circuit. In addition, the present inventor simply affects the noise close to the frequency of the carrier wave of the information signal if the resonance characteristic of the resonance circuit is broadened to reduce the Q value so that the gain does not change greatly even if the resonance frequency is shifted. It has also been found that malfunctions occur. In particular, when this communication system is applied to a portable device that is reduced in size and thickness, various components are mounted very close to each other, so that the influence of noise generated by each component becomes more remarkable. Therefore, the present inventor has considered such a viewpoint, and in the receiver, arranges the secondary coil so that the magnetic flux crossing the primary coil connected to the receiving electrode is magnetically coupled, By the capacitive coupling between the primary coil and the secondary coil at two or more locations in the coil, the resonance frequency is stabilized by the distributed constant capacitive coupling, and in addition, the magnetic coupling The inventors have found that the effect of improving the sensitivity can be exhibited and have come to the present invention.

  That is, the essence of the present invention includes a transmitter that converts and applies an information signal electric field to a transmission medium, and a receiver that receives the information signal by detecting the electric field via the transmission medium. The receiver includes a receiving electrode facing the transmission medium, a primary coil connected to the receiving electrode, a secondary coil arranged so that a magnetic flux intersecting the primary coil is magnetically coupled, and A receiving circuit connected to the secondary coil, and the capacitance between the primary coil and the secondary coil is capacitively coupled at two or more locations in the coil, thereby preventing malfunction due to noise, An object of the present invention is to realize a communication system capable of performing stable communication even when a distance between a transmission medium and a reception electrode is increased.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1A and 1B are schematic configuration diagrams showing a communication system according to an embodiment of the present invention. 1A and 1B, a part of the receiver is shown as an equivalent circuit. FIG. 1A is a diagram showing a case where the coupling capacitor C _c is divided into two stages, and FIG. 1B is a diagram showing a case where the coupling capacitor C _c is divided into five stages.

  In the communication system shown in FIGS. 1A and 1B, a transmission medium 2 such as a human body that transmits an information signal through an electric field, and an information signal modulated with respect to the transmission medium 2 is converted into an electric field and applied And a receiver 3 that detects an electric field via a transmission medium 2 and demodulates the electric field into an information signal.

  In this communication system, the transmitter 1 and the transmission medium 2 and the receiver 3 and the transmission medium 2 are electrically capacitively coupled, and information is generated by an electric field corresponding to the modulated information signal. A signal is transmitted. In this case, a displacement current flows through the transmission medium 2 but a steady current does not flow, and therefore there is no need for electrical conduction. Therefore, for example, even when the transmitter 1 is kept in the pocket, the transmitter 1 and the transmission medium 2 are capacitively coupled via a thin cloth, so that an information signal can be transmitted.

  The transmitter 1 applies the modulated information signal to the transmission medium 2 as an electric field. For this reason, it has a modulation circuit that modulates a carrier wave with an information signal, and a conversion circuit that amplifies the modulation signal and converts it into a voltage change. As a modulation method, AM, FM, ASK, FSK, PSK and other modulation methods can be used.

The receiver 3 detects and demodulates the electric field via the transmission medium 2 to obtain an information signal. The receiver 3 faces the transmission medium 2. The receiving electrode 31 that receives the electric field from the transmission medium 2, the primary coil L ₁ connected to the receiving electrode 31, and the magnetic flux that intersects the primary coil L ₁ are magnetically coupled. and arranged secondary coil L ₂ as a receiving circuit 32 connected to the secondary coil L _2, a coupling capacitor C _c to capacitive coupling between the primary coil L ₁ and the secondary coil L _2, Have The reception circuit 32 includes a detection circuit that amplifies and detects an electric field, and a demodulation circuit that demodulates an information signal modulated using the detected physical quantity.

In this configuration, the primary coil L ₁ and the secondary coil L ₂ are magnetically coupled, and the primary coil L ₁ and the secondary coil L ₂ are connected to two or more locations in the coil by the coupling capacitor C _c . Distributed and capacitively coupled.

The coupling capacitor C _c can suppress a shift in the resonance frequency in the resonance circuit due to a change in capacitance between the transmission medium 2 and the reception electrode 31 facing the transmission medium 2. In addition, the coupling capacitor C _c is preferably equal to or less than the capacitance value between the receiver 3 and the transmission medium 2 when the receiver 3 is separated from the transmission medium to the maximum distance at which the receiver 3 can communicate. Thereby, the coupling capacity between the receiver 3 and the transmission medium 2 can be reduced, and the distance between the communicable transmission medium 2 and the reception electrode 31 can be increased. Further, the coupling capacitor C _c is preferably a variable capacitor. Thereby, it becomes possible to control the distance between the transmission medium 2 and the receiving electrode 31, and it is possible to set the distance between the transmitting medium 2 and the receiving electrode 31 that can communicate with the intention of the user.

By introducing a coupling capacitor between the reception electrode 31 and the reception circuit 32, the communication performance is less likely to vary even if the distance between the reception electrode 31 and the transmission medium 2 varies, and this coupling capacitor C It is described in Japanese Patent Application No. 2007-69265, which is the prior application of the present applicant, that _c is further stabilized by dividing the _c into a plurality of stages. All this content is included here. In the present invention, in addition to the coupling capacitor C _c , the primary coil L ₁ (the reception electrode 31 side) and the coupling coil C _c are arranged so that magnetic fluxes intersecting each other are magnetically coupled between the reception electrode 31 and the reception circuit 32. A secondary coil L ₂ (receiving circuit 32 side) is introduced. Thereby, in addition to the capacitive coupling by the coupling capacitors C _c1 and C _c2 , magnetic coupling of the primary coil L ₁ and the secondary coil L ₂ is provided between the reception electrode 31 and the reception circuit 32. For this reason, two coupling effects of capacitive coupling and magnetic coupling work, and reception sensitivity is improved. Moreover, the communication performance is further stabilized by increasing the number of stages and distributing the coupling capacity.

When communication is performed using the communication system having the above-described configuration, the transmitter 1 modulates a transmission medium 2, for example, a carrier wave having a frequency (several tens of kHz to several tens of MHz) at which the human body exhibits conductivity with an information signal. This modulated information signal is amplified and converted into a voltage change. By applying this voltage change to the electrode of the transmitter, an electric field corresponding to the modulated information signal is generated around this electrode. This electric field is applied to the human body. The electric field applied to the human body is received by the receiving electrode 31 of the receiver 3. When an electric field is applied to the reception electrode 31, the modulated information signal is detected by the reception circuit 32 via the resonance circuit (the primary coil L ₁ , the coupling capacitor C _c and the secondary coil L ₂ ). The original information signal is acquired by demodulating using the used carrier wave. In this way, information signals can be transmitted and received using the human body as the transmission medium 2.

2 to 4 show specific configuration examples for realizing an equivalent circuit in the receiver shown in FIG. FIGS. 2A to 2C show that a core 41 made of a magnetic material such as ferrite is partially overlapped with a solenoid type primary coil L ₁ (broken line in the figure) and a secondary coil L ₂ (solid line in the figure). It is a figure which shows the structure wound. The configurations shown in FIGS. 2A and 2C are wound so that the primary coil L ₁ that is the coil with the smaller number of turns is sandwiched between the secondary coil L ₂ that is the coil with the larger number of turns. It is the composition which is.

3A to 3C, a toroidal primary coil L ₁ (broken line in the figure) and a secondary coil L ₂ (solid line in the figure) are partially overlapped with an annular core 41 made of a magnetic material such as ferrite. It is a figure which shows the structure wound by doing. The configurations shown in FIGS. 3A to 3C are wound so that the primary coil L ₁ that is the coil with the smaller number of turns is sandwiched between the secondary coil L ₂ that is the coil with the larger number of turns. It is the composition which is.

  In the case of the toroidal type coils shown in FIGS. 3A to 3C, the magnetic path is closed as compared with the solenoid type, so that it is less susceptible to external noise and less likely to affect the surroundings. . Therefore, a toroidal coil having a feature that hardly interferes with other components is effective in applications in which the components are mounted in close proximity to achieve miniaturization and thinning. Further, since this coil can be manufactured by a thin film process, it is effective for making the coil thinner. In particular, when a coil is formed on an IC by a thin film process, a toroidal type that does not affect the IC is preferable.

2 and 3, when the number of turns of the primary coil L ₁ and the secondary coil L ₂ is the same, both coils may be wound alternately. Further, the effect of the present invention can be obtained even if the air-core coil without the core 41 is used.

FIG. 4A shows a configuration in which a primary coil L ₁ and a secondary coil L ₂ configured by spiral coils are stacked. Further, FIG. 4 (b), (c), the primary coil L ₁ and the secondary coil L ₂ composed of a spiral coil, the one coil of the primary coil L ₁ and the secondary coil L ₂ in the same plane The structure by which the other coil is arrange | positioned between wires is shown.

In the configuration shown in FIG. 4A, a gap may be formed between the primary coil L ₁ and the secondary coil L ₂ without interposing anything, but a dielectric may be positively interposed. Since the dielectric exists between the primary coil L ₁ and the secondary coil L ₂ , the coupling capacitance can be increased. In order to moderately suppress the coupling capacity while maintaining the mechanical strength, a porous material having pores may be used as a dielectric.

In the configuration shown in FIGS. 4B and 4C, the other coil is disposed between the wires of one of the primary coil L ₁ and the secondary coil L _{2 in} the same plane. In the configuration shown in FIG. 4A, the coupling capacitance C _c is formed in the coil stacking direction. In the configurations shown in FIGS. 4B and 4C, the line spacing between the coils in the same plane is set. Capacitance at is the main coupling capacity. In the configuration shown in FIG. 4C, the magnetic path is closed by covering the primary coil L ₁ and the secondary coil L ₂ with a magnetic body 42 such as ferrite. In FIG. 4C, the primary coil L ₁ and the secondary coil L ₂ are sandwiched between the magnetic bodies 42. However, if the coil is thin, the magnetic path is almost closed even in this structure. Further, the surface of the primary coil L ₁ and the secondary coil L ₂ may be covered with a magnetic material using a magnetic material that can be formed by plating such as permalloy. In this case, the magnetic path can be closed strongly.

  In any of the configurations shown in FIGS. 4A to 4C, since the coupling capacitance is distributed almost uniformly in the coil, very stable communication can be obtained. In applications where there is a strong demand for thinning, the configuration shown in FIG. 4B is suitable. In this case, in order to increase the coupling capacitance, it is preferable to use a material having a large dielectric constant as the substrate or to cover the upper surface with a dielectric material.

  As described above, in the configurations shown in FIGS. 2 to 4, since the two coils are magnetically coupled and a part thereof is overlapped, the effects of both magnetic coupling and capacitive coupling are obtained. Communication sensitivity is improved. In addition, since the capacitance is capacitively coupled at two or more locations in the coil, the effect of two-stage distributed constant coupling is obtained, and in addition to the effect of improving sensitivity, the effect of stabilizing the resonance frequency is also achieved. It can be demonstrated.

  The present invention can also be applied to an unmodulated transmission system such as baseband transmission. The present invention is not limited to the above-described embodiment, and can be implemented with various modifications. For example, the configuration of the modulation circuit and conversion circuit in the transmitter and the detection circuit and demodulation circuit in the receiver can be changed as appropriate. Further, the materials, numerical values, and the like in the above embodiment are not particularly limited and can be changed within the scope of the present invention. Other modifications can be made without departing from the scope of the present invention.

Claims (4)

A transmitter for converting an information signal into an electric field and applying it to a transmission medium; and a receiver for detecting the electric field through the transmission medium and receiving the information signal, the receiver comprising: A receiving electrode facing the transmission medium, a primary coil connected to the receiving electrode, a secondary coil arranged so that magnetic flux intersecting the primary coil is magnetically coupled, and connected to the secondary coil The primary coil and the secondary coil are each configured in a spiral shape, and the capacitance between the primary coil and the secondary coil is a capacitance at two or more locations in the coil. A communication system characterized by being coupled. Communication system according to claim 1, wherein the pre kiss Pairaru shaped primary coil and the spiral secondary coil is characterized in that it is laminated. Communication system according to claim 1, characterized in that the other coil is disposed between one of the coils of wire of the primary coil and the secondary coil in the same plane. The communication system according to any one of claims 1 to 3 , wherein magnetic paths of the primary coil and the secondary coil are closed.

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