JP2007174054A - Field transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a high frequency component of frequency bands unnecessary to field transmission, and to reduce effect on surrounding electronics. <P>SOLUTION: The field transmission system comprises a variable capacity diode 1; inductors 2 and 3; resistors 4, 5, and 6; capacitors 7, 8, and 9; a buffer 10; a circuit ground 14; AC signal terminals 11 and 13 for inputting and outputting of a signal to a variable reactance; and a control signal input 12. The inductor 3 and the capacitor 9 are provided to eliminate unwanted high frequency component. Impedance of the inductor 3 is established to a level higher than the capacitor 9, in a frequency domain higher than the frequency bands used for transmission. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric field communication system applied to communication in which an electric field is induced in an electric field transmission medium, and the induced electric field is detected to transmit / receive information.

  Due to the miniaturization and high performance of portable terminals, wearable computers that can be attached to living bodies have been attracting attention. Conventionally, as information communication between such wearable computers, an electric field communication transceiver is connected and attached to a computer, and an electric field induced by the electric field communication transceiver is transmitted through a living body which is an electric field transmission medium, thereby Have been proposed (see Patent Documents 1 and 2).

  Also, in the configuration diagram of the conventional electric field communication transceiver shown in FIG. 4, only the configuration of the transmission portion is shown in the transmission and reception configurations. This transmission part is composed of a transmitter 36, and the transmitter 36 performs transmission in contact with a living body 35 serving as an electric field transmission medium. The transmitter 36 is an insulator 37 for contacting the living body 35, a transmission electrode 34 that performs electric field communication (transmission) to the living body 35 via the insulator 37, a variable reactance 30, a transmission circuit 31, and a circuit ground 32. And.

In such a configuration, in order to strengthen the electric field induced in the electric field communication, the variable reactance 30 is inserted into the output of the transmitter 36, and the stray capacitance C _g 33 generated between the living body 35 and the earth ground 39 is And the stray capacitance C _b 38 generated between the transmitter circuit ground 32 and the ground ground 39 is caused to resonate.

  FIG. 5 shows a configuration diagram of the variable reactance 30 shown in FIG. FIG. 5 shows a variable capacitance diode 40, an inductor 41, resistors 42 and 43, capacitors 44 and 45, AC signal terminals 46 and 47, a control signal input 48, and a buffer 49. Yes.

In the variable reactance 30 including the inductor 41 and the variable capacitance diode 40 having such a configuration, the reactance value is changed by changing the bias voltage (control signal) applied to the variable capacitance diode 40. The inductance value 41 and the capacitance value of the variable capacitance diode 40 are set so that the stray capacitances C _g and C _b resonate in the vicinity of the frequency of the carrier wave.

With such a configuration, when electric field communication is performed that efficiently induces an electric field of sufficient strength in the human body, which is a communication medium, and detects the induced electric field, communication is sent to the human body touching the information source. be able to.
JP 2004-153708 A United States Patent Application Publication, Pub. No. : US2004 / 0092296A1 Pub. Date: May 13, 2004

  However, in the conventional technology as described above, the variable reactance behaves as a capacitor in the high frequency region and is output from the transmitter because it is larger than the load (series of stray capacitances Cg and Cb) between the transmission electrode and the circuit ground. The high frequency component of the signal is not applied to the variable reactance but applied between the transmission electrode and the circuit ground. For this reason, there is a possibility that a signal outside the frequency band used for electric field communication is radiated to the space and affects surrounding electronic devices.

  The present invention has been made in view of the above, and an object of the present invention is to remove a high-frequency component in a frequency band unnecessary for electric field communication, and to reduce the influence on surrounding electronic devices.

  To achieve the above object, the present invention according to claim 1 is an electric field communication system in which an electric field based on information to be transmitted is induced in an electric field transmission medium and information is transmitted using the induced electric field. Transmitting means for modulating the information to be transmitted with an AC signal having a predetermined frequency to generate and output a transmission signal; an electrode for transmitting the transmission signal to the electric field transmission medium; and resonance with the transmission signal A first inductor for performing the operation, a variable capacitance diode whose capacitance changes according to an applied voltage, and a direct current obtained by rectifying the input transmission signal with the variable capacitance diode. A first resistor for applying the generated potential difference between an anode and a cathode of the variable capacitance diode, and a variable reactance capable of changing a reactance value, The second inductor inserted in series at the input terminal of the variable reactance to which the transmission signal is input, and inserted between the output terminal of the variable reactance from which the transmission signal is output and the circuit ground of the resonance circuit First capacity.

  According to a second aspect of the present invention, there is provided the second resistor according to the first aspect, wherein the second resistor is connected in parallel to the second inductor.

  According to a third aspect of the present invention, in the first or second aspect, the second inductor has a capacitance of 1/10 or less as compared with the first inductor.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, at least two of the variable capacitance diodes are connected in series via the second capacitance.

  Further, the present invention according to claim 5 is provided with two sets of configurations in which at least two of the variable capacitance diodes are connected in series via the second capacitor in any one of claims 1 to 3, The anodes of the respective variable capacitance diodes in the configuration are connected in series without passing through the capacitance, and thus both configurations are connected to each other.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the reception means for receiving an electric field based on information to be received induced in the electric field transmission medium via the electrode. Prepare.

  ADVANTAGE OF THE INVENTION According to this invention, the high frequency component of a frequency band unnecessary for electric field communication can be removed, and the influence on the surrounding electronic device can be reduced.

<First Embodiment>
FIG. 1 shows a configuration diagram for explaining a first embodiment of an electric field communication system. The electric field communication system includes a variable reactance for efficiently transmitting a sufficient level of transmission signal to the electric field transmission medium during transmission in the communication. As shown in FIG. 1, this variable reactance is composed of a variable capacitance diode 1, inductors 2 and 3, resistors 4, 5 and 6, capacitors 7, 8 and 9, a buffer 10, and a circuit ground 14. Has been. Note that AC signal terminals 11 and 13 and a control signal input 12 are provided for inputting and outputting signals to and from the variable reactance.

  In the electric field communication system having such a configuration, a circuit that resonates with the stray capacitances Cg33 and Cb38 shown in FIG. The resistors 4 and 5 serve to prevent the carrier wave from leaking to the circuit ground 14 and the buffer circuit 10. The capacitors 7 and 8 prevent the bias voltage (control signal) applied to the variable capacitance diode 1 from leaking to the output circuit of the transmission circuit connected to the AC signal terminal 11 or being short-circuited by the inductor 2. Have a role.

  An inductor 3 and a capacitor 9 are provided for removing unnecessary high frequency components. By providing the inductor 3 and the capacitor 9, the signal is cut off by setting the impedance of the inductor 3 higher than that of the capacitor 9 in a frequency region higher than the frequency band used for communication, and the transmission electrode 34 shown in FIG. And the circuit ground 14 are not applied. As a result, signals outside the frequency band used for communication can be prevented from being radiated into the space.

  The resistor 6 is used for damping a series resonance that occurs in the inductor 3 and the capacitor 9. By connecting the inductor 3 and the resistor 6 in parallel, damping by the resistor 6 can be prevented with respect to the series resonance with the stray capacitances Cg33 and Cb38 shown in FIG. 4 in the band used for communication. Furthermore, if the inductor 3 is made a size of 1/10 or less than the inductor 2, there is almost no influence on the series resonance with the stray capacitances Cb33 and Cg38 in the band used for communication.

<Second Embodiment>
In the configuration of FIG. 1, only one variable capacitance diode 1 is used, but in order to increase the equivalent breakdown voltage, two variable capacitance diodes 1 and 15 are connected in series as shown in FIG. The structure to do may be sufficient.

  With such a configuration, in the AC signal in the band used for communication, each capacitor can be regarded as a short circuit, and the variable capacitance diode 1 and the variable capacitance diode 15 are connected in series, and the voltage of the AC signal is set to each variable capacitance diode. 1 and the variable capacitance diode 15 are divided and applied.

  Therefore, even if the voltage of the AC signal increases in the resonance state, the voltage applied to each variable capacitance diode is halved, and resonance occurs due to the limitation of the voltage applied to the variable capacitance diode as compared with a single variable capacitance diode. Is less likely to occur.

  In this embodiment, a total of two variable capacitance diodes, variable capacitance diode 1 and variable capacitance diode 15, are used, but two or more may be used. On the other hand, in the control signal having a low frequency, each capacitor can be regarded as open, and the variable capacitance diodes 1 and 15 are connected in parallel as viewed from the buffer amplifier 10. Therefore, the voltage of the control signal applied to the control signal input 12 is applied as it is without being divided. In this embodiment, the circuit configuration prevents the suppression of resonance due to the applied voltage becoming higher than the withstand voltage of the variable capacitance diode and does not reduce the variable range of the capacitance.

<Third Embodiment>
Further, in order to suppress distortion due to nonlinearity of the variable capacitance diode, the anode and the cathode may be reversed and connected as shown in FIG. In general, since the current-voltage characteristics of the variable capacitance diode are asymmetric, when the anode potential is high, a short circuit occurs when the anode potential is higher than a predetermined value determined by the semiconductor characteristics, and the amplitude of the AC signal is suppressed.

  In order to prevent this, the variable capacitance diode 1, the variable capacitance diode 15, the variable capacitance diode 20, and the variable capacitance diode 21 are connected in series and in the reverse direction to a high-frequency AC signal. With this configuration, even if one of the variable capacitance diodes is short-circuited, the reverse-direction variable capacitance diode is not short-circuited, so that the amplitude of the AC signal is not suppressed. 1 and 2, resistors 4, 5, 16, and 17 are provided, and resistors 23, 24, and 25 are also provided.

  According to the embodiment described above, it is possible to remove high frequency components in a frequency band unnecessary for electric field communication, and to reduce the influence on surrounding electronic devices.

The block diagram of 1st Embodiment of an electric field communication system is shown. The block diagram of 2nd Embodiment of an electric field communication system is shown. The block diagram of 3rd Embodiment of an electric field communication system is shown. The block diagram of the electric field communication system by a prior art is shown. The block diagram of the electric field communication system by a prior art is shown.

Explanation of symbols

1 Variable capacitance diode 2, 3 Inductor 4, 5, 6 Resistance 7, 8, 9 Capacity 10 Buffer

Claims (6)

In an electric field communication system in which an electric field based on information to be transmitted is induced in an electric field transmission medium and information is transmitted using the induced electric field.
Transmitting means for modulating the information to be transmitted with an AC signal having a predetermined frequency to generate and output a transmission signal;
An electrode for transmitting the transmission signal to the electric field transmission medium;
A first inductor for resonating with the transmission signal, a variable capacitance diode whose capacitance changes in accordance with an applied voltage, and obtained by rectifying the input transmission signal with the variable capacitance diode A first resistor for applying a potential difference generated according to a direct current between an anode and a cathode of the variable capacitance diode, and a variable reactance capable of changing a reactance value.
A second inductor inserted in series at the input end of the variable reactance to which the transmission signal is input;
A first capacitor inserted between the output terminal of the variable reactance from which the transmission signal is output and the circuit ground of the resonance circuit;
An electric field communication system comprising:   The electric field communication system according to claim 1, further comprising a second resistor connected in parallel to the second inductor.   3. The electric field communication system according to claim 1, wherein the second inductor has a capacitance of 1/10 or less of that of the first inductor. 4.   The electric field communication system according to any one of claims 1 to 3, wherein at least two of the variable capacitance diodes are connected in series via a second capacitance. Two sets of configurations in which at least two of the variable capacitance diodes are connected in series via the second capacitance,
The electric field according to any one of claims 1 to 3, wherein the anodes of each one of the variable capacitance diodes in this configuration are connected in series without passing through a capacitance, and thus both configurations are connected to each other. Communications system. 6. The electric field communication system according to claim 1, further comprising receiving means for receiving an electric field based on information to be received induced in the electric field transmission medium via the electrodes.

Images