JP5026367B2 - Human body communication device - Google Patents

Description

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

  With recent technological development, a communication method using an electric field induced in a human body or the like has been proposed as a completely new communication method. In such a communication method, an electric field corresponding to a modulation signal obtained by modulating an information signal is applied from a transmitter to a human body as a transmission medium, and the electric field transmitted through the human body is detected by a receiver. The information signal corresponding to the electric field is demodulated.

2. Description of the Related Art Conventionally, as a communication device using the above communication method, a device that extracts a frequency component for communication from an information signal received via a human body is known (for example, see Patent Document 1). The communication device described in Patent Document 1 includes a reception electrode that is connected to or capacitively coupled to a human body, and a resonance circuit that is provided at a subsequent stage of the reception electrode. From the information signal received from the reception electrode via the human body, The resonance frequency of the resonance circuit is set so as to extract a frequency component for communication.
JP 2005-94466 A

However, in the communication device described in Patent Document 1, the resonance frequency of the resonance circuit becomes unstable due to a change in the capacitance between the human body and the receiving electrode according to the distance between the human body and the receiving electrode. There was a problem that the communication quality was not stable.
In addition, when the application field spreads and the equipment on which the communication device is mounted is increased in size, the receiving electrode and the resonance circuit are separated from each other, and when the wiring is drawn long, the wiring and the metal housing (ground) of the equipment As a result, the parasitic capacitance between the two and the information signal is attenuated, the external signal is easily mixed, and the establishment of a communication error is remarkably increased. In this case, the use of the coaxial cable as the wiring can reduce the mixing of external noise, but there is a problem that the parasitic capacitance is further increased between the core wire and the shield and the information signal is greatly attenuated.

The present invention has been made in view of the above points, and can stabilize the resonance frequency in the resonance circuit, suppress the attenuation of the information signal even if the wiring is drawn long, and improve the communication quality. It is an object of the present invention to provide a human body communication device that can perform communication.

Human body communication apparatus of the present invention is a communication apparatus that performs communication via a human body, a receiving electrode connected or capacitively coupled with a portion of the human body, and a cable portion having one end connected to the receiving electrode, said cable A receiving circuit section that is connected to the other end of the section and that resonates in a communication signal band and extracts a necessary frequency component; a first coupling capacitor provided between the cable section and the receiving circuit section; and the cable connected in parallel to the parasitic capacitance formed between the reference potentials of parts and the receiving circuit, and a inductor cable portion constituting the cable portion resonance circuit resonates with the parasitic capacitance, the cable portion resonance The resonance frequency of the circuit is the same as or close to the resonance frequency of the receiving circuit unit .

According to this configuration, the first coupling capacitor is provided between the cable unit and the receiving circuit unit, and the cable unit resonance circuit and the receiving circuit unit respectively resonate. The influence of the fluctuation in capacitance with the receiving electrode is reduced, and the resonance operation in the receiving circuit unit is stabilized.
Further, since the cable part resonance circuit is provided and the cable part inductor is caused to resonate together with the parasitic capacitance formed between the cable part and the ground, attenuation of the signal due to the parasitic capacitance is suppressed. In particular, when a coaxial cable is used as the cable portion, signal attenuation due to parasitic capacitance can be suppressed and mixing of external noise can be prevented.
Therefore, communication quality can be improved in a communication apparatus that communicates via a transmission medium such as a human body.

In the human body communication device according to the present invention, a second coupling capacitor is provided between the reception electrode and the cable unit resonance circuit.

  According to this configuration, since the second coupling capacitor is further provided between the reception electrode and the cable part resonance circuit, the capacitance variation between the transmission medium such as a human body and the reception electrode in the cable part resonance circuit is reduced. The influence is reduced, the resonance operation of the cable part resonance circuit is stabilized, and the communication quality can be further improved.

In the human body communication device according to the present invention, the reception electrode is plural, the cable unit connects the plurality of reception electrodes and the reception circuit unit, and the cable unit resonance circuit is connected to the plurality of reception electrodes. Correspondingly, a plurality of reception electrodes are provided, and among the plurality of reception electrodes, a reception electrode switching unit for connecting an appropriate reception electrode to the reception circuit unit is provided.

  According to this configuration, a plurality of reception electrodes can be switched and used. Even if the length of the cable portion from each receiving electrode to the receiving circuit portion is different and the size of the parasitic capacitance is different, the cable portion resonance circuit provided corresponding to each receiving electrode is connected to each parasitic capacitance. By designing in consideration of the size of the signal, even if the input electrode for the receiving circuit unit is switched to any of the plurality of receiving electrodes, the signal attenuation due to the parasitic capacitance can be suppressed.

In the human body communication device according to the present invention, the reception electrode switching unit switches to a reception electrode that is most strongly connected or capacitively coupled to a part of the human body among the plurality of reception electrodes.

  According to this configuration, even when a plurality of reception electrodes are provided, a signal is received by switching to a reception electrode that is most strongly connected or capacitively coupled to a part of the transmission medium among the plurality of reception electrodes. Even if a transmission medium such as the above is capacitively coupled to any receiving electrode, communication is possible.

According to the present invention, in the human body communication device, the cable portion is a coaxial cable.

  According to this configuration, it is possible to suppress signal attenuation due to parasitic capacitance and to prevent external noise from being mixed.

  According to the present invention, it is possible to stabilize the resonance frequency in the receiving circuit unit, and it is possible to suppress the attenuation of the information signal even when the wiring is routed for a long time, thereby improving the communication quality.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a first embodiment of a communication apparatus according to the present invention, and is a schematic configuration diagram of a communication system.

  A communication system 1 shown in FIG. 1 transmits and receives an information signal via a transmission medium such as a human body 2, and a communication device on a transmission side (not shown) that applies an electric field obtained by modulating the information signal to the human body 2, It comprises a communication device 3 that detects an electric field via a human body 2 that transmits an information signal via the electric field and demodulates the electric field into an information signal.

In this communication system 1, a capacitive coupling is established between the communication device on the transmission side and the human body 2 and between the communication device 3 and the human body 2 (capacitance between the communication device 3 and the human body 2. _Cx ), and the information signal is transmitted by an electric field obtained by modulating the information signal. In this case, the displacement current flows through the human body 2 but the steady current does not flow, so that it is not necessary to be electrically connected. Therefore, for example, even if the transmission-side communication device is kept in the pocket, the transmission-side communication device and the human body 2 are capacitively coupled via a thin cloth, so that an information signal can be transmitted.

  The communication device on the transmission side 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, and an electric field formed by modulating the information signal with respect to the human body 2 Is granted.

As shown in FIG. 1, the communication device 3 includes a receiving electrode 5, a cable unit 6 connected to the receiving electrode 5, a receiving circuit unit 8 connected to the cable unit 6 via a coupling capacitor 7, a cable The cable portion inductor 9 is provided so as to resonate with the parasitic capacitance C _s between the portion 6 and the ground. Incidentally, the coupling capacitor 7 and the capacitance C _c, cable unit inductor 9 is the inductance L _s.

  The receiving electrode 5 is formed of a flat plate electrode, and is connected to or capacitively coupled to a part of the human body 2 by receiving an electric field from the human body 2. Further, the capacitance of the receiving electrode 5 varies according to the distance from the human body 2 facing the receiving electrode 5.

  The cable part 6 is comprised by the coaxial cable, and covers the circumference | surroundings of a core wire with a shield via an insulator, and also covers the circumference | surroundings with an insulating film. The shield electrically separates the core wire from the external environment, and prevents external noise from entering the core wire. In the present embodiment, the cable portion 6 is configured by a coaxial cable, but is not limited to this configuration, and may be configured by a copper wire cable having no shield.

The reception circuit unit 8 includes a resonance circuit 11 as a filter, and an amplifier and a control circuit (not shown) are connected to the subsequent stage of the resonance circuit 11. The resonance circuit 11 includes a resonance inductor 13 and a resonance capacitor 14 connected in parallel between the coupling capacitor 7 and the ground, and a resonance frequency corresponding to a frequency component for communication is set. Yes. The reception circuit unit 8 extracts a frequency component corresponding to the resonance frequency of the resonance circuit 11 from the information signal received by the reception electrode 5 and amplifies it by an amplifier before performing reception signal processing. The resonance inductor 13 is the inductance _{L 0,} the resonance capacitor 14 is the capacitance _{C 0.}

  The coupling capacitor 7 capacitively couples the cable unit 6 and the reception circuit unit 8, and the resonance frequency of the resonance circuit 11 due to the capacitance variation between the reception electrode 5 and the human body 2 facing the reception electrode 5. The shift is suppressed. Here, resonance frequency shift suppression will be briefly described. Here, for convenience of explanation, it is assumed that the circuit configuration is obtained by removing the cable portion inductor 9 from the schematic configuration diagram of FIG. 1, and the resonance frequency in the resonance circuit 11 is set to 10 MHz.

Figure 2 is an explanatory view of a shift in the resonance frequency, capacitance C _x between the body 2 and the receiving electrode 5 indicates a case where the decrease (if gaps than the standard state is large). Here, the waveform S1 represents a waveform in the above-described circuit configuration for convenience provided with a coupling capacitor, and the waveform S2 represents a waveform in a comparison configuration obtained by removing the coupling capacitor from the above-described circuit configuration for convenience. As can be seen from FIG. 2, when the waveform S1 and the waveform S2 are compared, the shift amount of the resonance frequency shown in the waveform S1 is the resonance frequency shown in the waveform S2 with the resonance frequency 10 MHz set in the resonance circuit 11 as a reference. It is kept small compared to the shift amount. Therefore, it has been found that providing the coupling capacitor 7 between the cable unit 6 and the receiving circuit unit 8 suppresses the shift amount of the resonance frequency. Although explanation is omitted, it has been found that the resonance frequency shift is similarly suppressed when the capacitance _Cx increases (when the gap is smaller than the standard state).

Returning to Figure 1, a cable unit inductor 9 is connected in parallel with the parasitic capacitance C _s that occurred between the cable portion 6 and the ground, to constitute a cable unit resonant circuit 15 together with the parasitic capacitance C _s ing. Further, the cable portion inductor 9 is designed to have the same value or a close value as the resonance frequency in the resonance circuit 11 of the reception circuit portion 8, and suppresses attenuation of frequency components for communication. That is, when resonance of the cable portion inductor 9 and the parasitic capacitance C _s, the resistance of the cable portion resonance circuit 15 becomes infinite, the cable 6 is not electrically connected to the ground through the parasitic capacitance C _s, the frequency for communication The attenuation of the component is suppressed.

  When communication is performed in the communication system 1 having the above configuration, the information signal is modulated to a frequency (several hundred kHz to several tens of MHz) indicating the conductivity of the human body 2 in the communication device on the transmission side, and a modulated signal is generated. The This modulated signal is amplified and converted into a voltage change. When this voltage change is applied to the electrode of the transmitting communication device, an electric field signal corresponding to the modulation signal is generated around the electrode. The electric field signal is applied to the human body 2 and received by the receiving electrode 5 of the communication device 3.

  When an electric field is applied to the reception electrode 5, a modulation signal is detected by a detection circuit (not shown) subsequent to the reception circuit unit 8. Then, in a demodulation circuit located at a subsequent stage of the detection circuit, an information signal is acquired by demodulating using the carrier wave used in the communication device on the transmission side. In this way, information signals are transmitted and received using the human body 2 as a communication medium.

  Next, the information signal attenuation suppression effect in the communication apparatus according to the present invention will be described. In the present embodiment, simulation was performed using the three circuit models shown in FIG. 3A is a circuit model (first comparative example) in which the coupling capacitor and the cable section inductor are removed from the communication system of FIG. 1, and FIG. 3B is the cable model of the communication system of FIG. FIG. 3C shows a circuit model (the present invention) of the communication system shown in FIG. 1. FIG. 3C shows a circuit model excluding the inductor (second comparative example).

In the circuit model of the first comparative example, the inductance L ₀ of the resonance inductor 13 is 22.0 μH and the capacitance C ₀ of the resonance capacitor 14 is 10 so that the resonance frequency of the resonance circuit 11 is 10 MHz. The resonant circuit 11 was configured with 0.0 pF. Further, the capacitance _{C h} of the human body 2 and the ground 100.0PF, the capacitance _{C x} of the human body 2 and the receiving electrode 5 and 1.0 pF, the 10.0pF between the cable portion 6 and the ground the case where the parasitic capacitance C _s formed was assumed. Then, the simulation was performed by setting the frequency of the AC power supply 16 to 10 MHz and the amplitude to 1.0 Vpp, and providing the voltmeter 17 at the subsequent stage of the resonance circuit 11 to measure the output voltage.

In the circuit model of the second comparative example is provided with a coupling capacitor 7 having a capacitance C _c of 1.0pF between the cable portion 6 and the resonant circuit 11 of the circuit model of the first comparative example And simulated. In the circuit model of the present invention, the cable section inductor 9 having an inductance L _s of 22.0 μH in parallel with the parasitic capacitance C _s so as to resonate with the parasitic capacitance C _s of the circuit model of the second comparative example. A simulation was performed.

  FIG. 4 shows a simulation result by the circuit model shown in FIGS. 3 (a), (b), and (c). In the simulation results of FIG. 3, the vertical axis is the output, the horizontal axis is the elapsed time, the broken line W1 is the simulation result of the first comparative example, the alternate long and short dash line W2 is the simulation result of the second comparative example, and the solid line W3 is the simulation of the present invention. Each result is shown.

Comparing the first comparative example and the second comparative example, the dashed line W1 has an amplitude of about 0.5 μV, whereas the alternate long and short dash line W2 has an amplitude of about 10.0 μV. Therefore, it has been found that providing the coupling capacitor 7 between the cable portion 6 and the receiving circuit portion 8 improves the reception characteristics. Further, when comparing the second comparative example with the present invention, the alternate long and short dash line W2 has an amplitude of about 10.0 μV, whereas the solid line W3 of the present invention has an amplitude of about 58.0 μV. Thus, provided with a coupling capacitor 7 between the cable portion 6 and the receiving circuit portion 8, parallel with the parasitic capacitance C _s to resonate with the parasitic capacitance C _s that occur between the cable portion 6 and the ground It has been found that the reception characteristics can be further improved by providing the cable portion inductor 9 in the cable.

As described above, according to the communication device 3 according to the present embodiment, the coupling capacitor 7 is provided between the cable unit 6 and the reception circuit unit 8, and the resonance circuit of the cable unit resonance circuit 15 and the reception circuit unit 8. Therefore, the influence of the capacitance variation between the human body and the reception electrode 5 in the reception circuit unit 8 is reduced, and the resonance operation in the resonance circuit 11 of the reception circuit unit 8 is stabilized. Further, the cable portion resonant circuit 15 is provided, due to so as to resonate the cable portion inductor 9, the attenuation of the information signal due to the parasitic capacitance can be suppressed with the formed parasitic capacitance C _s between the cable portion 6 and the ground . Therefore, communication quality can be improved in the communication device 3 that communicates via the human body 2.

As shown in FIG. 5, a coupling capacitor 23 having a capacitance C _c1 is provided between the cable unit 6 and the reception circuit unit 8 of the communication system 21, and the connection between the reception electrode 5 and the cable unit resonance circuit 15. A coupling capacitor 24 having a capacitance C _c2 may be provided between them. With this configuration, coupling capacitor 24, the capacitance C _x varies by cable section shifting the resonant frequency of the resonant circuit 15 between the body 2 facing the receiving electrode 5 to the receiving electrode 5 can be suppressed. Therefore, the resonance operation of the cable part resonance circuit 15 is stabilized, and the communication quality of the communication device 22 can be improved.

  Next, a second embodiment of the present invention will be described. The communication apparatus according to the second embodiment of the present invention is different from the above-described communication apparatus according to the first embodiment in that it can selectively communicate with a plurality of reception electrodes. Therefore, only the differences will be particularly described.

FIG. 6 is a diagram showing a second embodiment of the communication apparatus according to the present invention, and is a schematic configuration diagram of the communication system. As shown in FIG. 6, the communication device 32 in the communication system 31 includes a plurality of receiving electrodes 5, one end branched into a plurality and connected to the plurality of receiving electrodes 5, and the other end connected to the coupling capacitor 7. And a receiving circuit unit 8 connected to the cable unit 33 via the coupling capacitor 7. In addition, each branch cable 34 branched from the cable section 33 includes a cable section inductor 9 that resonates with a parasitic capacitance C _s between each branch cable 34 and the ground, each reception electrode 5, and the reception circuit section 8. A switch unit 35 that is electrically separated is provided.

  Each switch unit 35 is controlled by a control unit (not shown). The control unit scans the plurality of reception electrodes 5 to investigate the reception electrode 5 receiving the strongest electric field, and applies the strongest electric field. The switch unit 35 is switched so as to connect the receiving electrode 5 and the receiving circuit unit 8 that are received. With this configuration, an information signal is received by switching to a reception electrode 5 that is connected or capacitively coupled to a part of the human body 2 among the plurality of reception electrodes 5, so that no matter which reception electrode 5 the human body 2 is capacitively coupled to. Communication is possible. Note that the receiving electrode switching unit described in the claims includes a plurality of switch units 35 and a control unit in the present embodiment.

As described above, according to the communication apparatus 3 according to this embodiment, there in case where a different length size of the parasitic capacitance C _s of the branch cable 34 from the receiving electrode 5 to the receiving circuit section 8 is different even, by the cable portion resonance circuit 15 provided corresponding to each of the receiving electrode 5 is designed in consideration of the size of each parasitic capacitance C _s, the input electrode with respect to the receiver circuit 8 is plural receiving electrode 5 be switched to any of the receiving electrode 5 of, it is possible to suppress the attenuation of the information signal due to the parasitic capacitance C _s.

  The embodiment disclosed this time is illustrative in all respects and is not limited to this embodiment. The scope of the present invention is shown not by the above description of the embodiments but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  As described above, the present invention can stabilize the resonance frequency in the receiving circuit unit, and can suppress the attenuation of the information signal even if the wiring is routed for a long time, thereby improving the communication quality. And is particularly useful for a communication apparatus that performs communication via a transmission medium such as a human body.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows 1st Embodiment which concerns on this invention, and is a schematic block diagram of a communication system. It is a figure which shows 1st Embodiment which concerns on this invention, and is explanatory drawing of the shift amount of a resonant frequency. It is a figure which shows 1st Embodiment based on this invention, (a) is a circuit model except the coupling capacitor and the inductor for cable parts in the communication system of FIG. 1, (b) is in the communication system of FIG. A circuit model excluding the inductor for the cable portion, (c) is a circuit model of the communication system of FIG. It is a figure which shows 1st Embodiment which concerns on this invention, and is a simulation result by the circuit model shown by Fig.3 (a), (b), (c). It is a figure which shows the modification of 1st Embodiment which concerns on this invention. It is a figure which shows 2nd Embodiment which concerns on this invention, and is a schematic block diagram of a communication system.

Explanation of symbols

1, 21, 31 Communication system 2 Human body (transmission medium)
3, 22, 32 Communication device 5 Reception electrode 6, 33 Cable part 7, 23 Coupling capacitor (first coupling capacitance)
DESCRIPTION OF SYMBOLS 8 Receiver circuit part 9 Inductor for cable parts 11 Resonant circuit 13 Inductor for resonance 14 Resonance capacitor 16 AC power supply 17 Voltmeter 24 Coupling capacitor (second coupling capacitance)
34 Branch cable 35 Switch part

Claims (5)

In a communication device that performs communication via a human body ,
A receiving electrode connected or capacitively coupled to a part of the human body ;
A cable portion having one end connected to the receiving electrode;
A receiving circuit unit connected to the other end of the cable unit and resonating in a communication signal band to extract a necessary frequency component;
A first coupling capacitor provided between the cable portion and the receiving circuit portion;
A cable unit inductor connected in parallel to a parasitic capacitance formed between the cable unit and a reference potential of the receiving circuit, and resonating with the parasitic capacitance to form a cable unit resonance circuit ;
A human body communication device characterized in that the resonance frequency of the cable part resonance circuit is the same as or close to the resonance frequency of the reception circuit part . The human body communication device according to claim 1, further comprising a second coupling capacitor between the reception electrode and the cable part resonance circuit. A plurality of the receiving electrodes, the cable portion connects the plurality of receiving electrodes and the receiving circuit portion, and a plurality of the cable portion resonance circuits are provided corresponding to the plurality of receiving electrodes,
The human body communication device according to claim 1, wherein a reception electrode switching unit that connects an appropriate reception electrode to the reception circuit unit among the plurality of reception electrodes is provided. The human body communication device according to claim 3, wherein the reception electrode switching unit switches to a reception electrode that is most strongly connected or capacitively coupled to a part of the human body among the plurality of reception electrodes. The human body communication device according to claim 1, wherein the cable portion is a coaxial cable.

Images