JP5216705B2 - Receiving machine - Google Patents

Description

  The present invention relates to a receiver of a communication system that performs communication via a living body.

  As a communication system that performs communication via a living body, an electric field is induced around a human body by applying a potential signal obtained by modulating communication data, which is information transmitted to and received from a receiver, to the human body by capacitive coupling. In addition, a communication system is known in which a receiver detects an electric field induced around a human body and demodulates communication data from the detected electric field (for example, Patent Documents 1-4).

JP 2001-298425 A JP 2001-352298 A JP 2004-282733 A JP 2004-222596 A

When a communication system that performs communication via a living body is used for security purposes such as authentication of a transmitter holder, communication data is transmitted and received between the transmitter and the receiver only through the living body. It will be necessary.
However, in a communication system that performs communication through a living body, a signal that propagates through the space without passing through the living body and reaches the receiver directly cannot be completely suppressed. It is important that the receiver does not receive communication data from signals that arrive after propagation.

  Therefore, according to the present invention, in a communication system that performs communication via a living body, the receiver receives communication data from a signal that propagates through the space without passing through the living body and reaches the receiver directly. It is an object to suppress this.

  In order to achieve the object, a transmitter applies a modulated signal obtained by modulating communication data to a living body, whereby a receiver that receives the communication data via an electric field induced around the living body receives the communication data during communication. A receiving electrode placed under an electric field around the living body, a receiving section that converts the electric field applied to the receiving electrode from the living body into the modulation signal, and demodulates the converted modulation signal into the communication data; and And an interference signal generator for applying an interference signal for disturbing the modulation signal.

  According to such a receiver, the modulation signal that has directly propagated through the space from the transmitter and reached the reception electrode is disturbed by the interference signal, and its demodulation is prevented. On the other hand, when the receiving electrode and the living body are coupled to each other during communication and an electric field around the living body is applied to the receiving electrode, an interference signal flows out to the living body coupled to the receiving electrode and attenuates. Therefore, if the characteristics such as the generation level of the interference signal are appropriately set, the demodulation of the modulation signal that propagates through the space and directly reaches the reception electrode is prevented by the interference signal, and the surroundings of the living body connected to the reception electrode are prevented. The demodulation of the modulated signal converted from the electric field can be prevented from being disturbed by the interference signal.

Here, the modulated signal may be a signal obtained by ASK modulating the communication data, and in this case, the interference signal may be a signal having a predetermined frequency.
Such a receiver can be used to configure a communication system together with a transmitter that applies a modulated signal obtained by modulating communication data to a living body and induces an electric field around the living body.

  As described above, according to the present invention, in a communication system that performs communication through a living body, the receiver transmits communication data from a signal that propagates through the space without passing through the living body and reaches the receiver directly. It can suppress receiving.

It is a figure which shows the example of application of the communication system which concerns on embodiment of this invention. It is a figure which shows the structure of the communication system which concerns on embodiment of this invention. It is a figure which shows the frequency characteristic of the electric field sensor of the receiver which concerns on embodiment of this invention. It is a figure showing the comparison by the presence or absence of the output interference signal with respect to the spatial propagation signal of the demodulator of the receiver which concerns on embodiment of this invention. It is a figure showing the comparison by the presence or absence of the output interference signal with respect to the spatial propagation signal of the amplifier of the receiver which concerns on embodiment of this invention. It is a figure showing the comparison by the frequency of the interference signal of an output with respect to the spatial propagation signal of the demodulator of the receiver which concerns on embodiment of this invention. It is a figure showing the comparison by the presence or absence of the disturbance signal of an output with respect to the human body propagation signal of the demodulator of the receiver which concerns on embodiment of invention. It is a figure showing the comparison by the presence or absence of a user's hand contact of the output of the amplifier of the receiver which concerns on embodiment of this invention.

Hereinafter, an embodiment of a communication system according to the present invention will be described taking application to human body communication as an example.
First, the first embodiment will be described.
FIG. 1 a shows a configuration of a communication system according to the present embodiment.
As shown in the figure, the communication system is carried by the user in a form close to the user's human body 3, for example, the card-type transmitter 1 and reception in which the user's human body 3 (hand or the like) is approached when performing communication. The receiver 2 includes the electrode 21.
In such a configuration, when communication is performed, a transmission signal is applied from the transmitter 1 to the human body 3 of the user, and an electric field that varies according to the transmission signal obtained by modulating communication data is induced around the human body.
On the other hand, when the human body 3 approaches the receiving electrode 21, the receiver 2 detects the fluctuation of the electric field around the human body 3, generates a reception signal indicating the fluctuation of the electric field, and demodulates the communication data from the reception signal. Then, processing corresponding to the communication data (for example, in the case of FIG. 1, release of the door lock) is performed.
Next, FIG. 2 shows the configuration of the transmitter 1 and the receiver 2.
As shown in the figure, a transmitter 1 is a transmission-side data processing unit 11 that generates communication data to be transmitted to a receiver 2, a modulator 12 that modulates communication data and outputs it as a transmission signal, and a human body 3 that is capacitively coupled to the transmission signal. Is applied to the human body 3 to induce an electric field around the human body.
In addition, the receiver 2 includes a reception electrode 21 that is placed under an electric field induced around a human body during communication, a disturbance signal generation unit 22 that generates a disturbance signal and applies it to the reception electrode 21, and a reception unit 23. Yes. The receiving unit 23 detects the electric field strength applied from the human body 3 to the receiving electrode 21 and outputs a detection signal corresponding to the detected electric field strength, and amplifies the detection signal output from the electric field sensor 231. It comprises an amplifier 232 that outputs as a received signal, a demodulator 233 that demodulates communication data from the received signal, and a reception-side data processing unit 234 that processes the demodulated communication data.

The transmitter electrode 13 of the transmitter 1 and the receiver electrode 21 of the receiver 2 are provided in a form covered with a non-conductive cover so that the human body 3 does not need to be touched directly.
Now, in this embodiment, the transmission rate of the communication data output from the transmission side data processing unit 11 of the transmitter 1 is 1200 bps, the modulation in the modulator 12 is 100% ASK with a carrier wave of 1.9 MHz, and the transmission electrode 13 The applied voltage is 5 Vpp.
In accordance with this, as shown in FIG. 3, the frequency characteristic of the reception sensitivity of the electric field sensor 231 of the receiver 2 has a peak-shaped characteristic of 1.9 MHz and attenuates on both sides thereof.
In such a communication system configuration, as shown in FIG. 1 a, when the user carrying the transmitter 1 touches the cover of the reception electrode 21 of the receiver 2, the arrow 101 indicates. In addition, an electric field corresponding to the transmission signal is transmitted from the transmission electrode 13 of the transmitter 1 to the reception electrode 21 via the human body 3 and detected as a reception signal by the receiver 2, and communication data is demodulated and received from this. become.

  On the other hand, as shown in FIG. 1 b, the user carrying the transmitter 1 just approaches the receiving electrode 21 of the receiver 2 without touching the hand on the cover of the receiving electrode 21 of the receiver 2. A signal radiated from the transmitter 1 may propagate directly in space and be coupled to the reception electrode 21 as indicated by an arrow 102.

Then, if communication data is demodulated and received by the receiver 2 from such a signal directly propagated in space, a malfunction of the reception side data processing unit 234 of the receiver 2 is induced.
Therefore, in the present embodiment, by applying a disturbance signal of 1.4 MHz and 500 mVpp from the interference signal generation unit 22 to the reception electrode 21, the signal emitted from the transmitter 1 as shown in FIG. The receiving unit 23 is prevented from receiving communication data.
Hereinafter, it is shown that the reception unit 23 of the receiver 2 can be prevented from receiving communication data from the signal radiated from the transmitter 1 by applying the interference signal from the interference signal generation unit 22 to the reception electrode 21. .
Now, as shown in FIG. 4 a, the user's hand carrying the transmitter 1 is not brought into contact with the cover of the reception electrode 21 of the receiver 2, so that it is between the reception electrode 21 and the transmission electrode 13 of the transmitter 1. Measurement result of the output of the demodulator 233 of the receiver 23 of the receiver 2 when the transmitter 1 is arranged so that the distance is 10 cm and the character code “a” is serially transmitted from the transmitter 1 as communication data. Is shown in FIGS. 4b and 4c.

FIG. 4 b shows the output of the demodulator 233 when no interference signal is applied to the reception electrode 21 from the interference signal generation unit 22, and FIG. 4 c applies the interference signal from the interference signal generation unit 22 to the reception electrode 21. In this case, the output of the demodulator 233 is shown.
As shown in FIGS. 4B and 4C, when the interference signal is not applied to the reception electrode 21, the communication data is demodulated by the demodulator 233 by the signal radiated from the transmitter 1 and propagated through the space. When the interference signal is applied to the reception electrode 21, the demodulator 233 does not demodulate the communication data from the signal radiated from the transmitter 1 and propagated through the space.

  Here, as shown in FIG. 5 a, the transmitter 1 is transmitted between the receiving electrode 21 and the transmitter 1 without bringing the user's hand carrying the transmitter 1 into contact with the cover of the receiving electrode 21 of the receiver 2. Measuring the output of the amplifier 232 of the receiver 23 of the receiver 2 when the distance between the electrode 13 and the electrode 13 is 10 cm, and “aaaaa ...” is serially transmitted from the transmitter 1 as communication data. The results are shown in FIGS.

  In this case, FIG. 5b shows the output of the amplifier 232 of the receiver 23 of the receiver 2 when no interference signal is applied to the reception electrode 21 from the interference signal generator 22, and FIG. As shown in the output of the amplifier 232 of the reception unit 23 of the receiver 2 when a signal is applied to the reception electrode 21, the interference signal generation unit 22 applies a disturbance signal to the reception electrode 21, thereby radiating from the transmitter 1. The signal propagated through the space to the receiving electrode 21 is disturbed.

  As a result of such disturbance, when a disturbing signal is applied to the receiving electrode 21, as shown in FIG. 5c, the signal radiated from the transmitter 1 in the demodulator 233 and propagated through the space cannot be demodulated. The reception of communication data by a signal propagated through space is suppressed.

  Here, as a comparative example regarding the frequency of the interference signal, as shown in FIG. 6A, the user's hand carrying the transmitter 1 does not come into contact with the cover of the reception electrode 21 of the receiver 2 and the transmission with the reception electrode 21 is performed. The receiver 1 of the receiver 2 when the transmitter 1 is arranged so that the distance from the transmitter electrode 13 of the transmitter 1 is 10 cm and the character code “a” is serially transmitted from the transmitter 1 as communication data. The measurement results of the outputs of the 23 demodulator 233 are shown in FIGS.

  6B shows the output of the demodulator 233 when a 1.2 MHz interference signal is applied to the reception electrode 21 from the interference signal generation unit 22, and FIG. 6C shows the 1.3 MHz interference signal from the interference signal generation unit 22. FIG. 6d shows the output of the demodulator 233 when a 2.0 MHz interference signal is applied from the interference signal generator 22 to the reception electrode 21 when applied to the reception electrode 21. FIG. Yes.

  From this comparative example, a 1.2 MHz or 1.3 MHz interference signal cannot sufficiently disturb the signal radiated from the transmitter 1 and propagated through the space to prevent demodulation in the demodulator 233, but a 2.0 MHz interference signal If it exists, it turns out that the demodulation in the demodulator 233 can be blocked | prevented similarly to the interference signal of 1.4 MHz.

  Next, as shown in FIG. 7a, the user's hand carrying the transmitter 1 is brought into contact with the cover of the receiving electrode 21 of the receiver 2, and the character code "a" is serially transmitted from the transmitter 1 as communication data. The measurement results of the output of the demodulator 233 of the receiver 23 of the receiver 2 when transmitted are shown in FIGS.

FIG. 7 b shows the output of the demodulator 233 when no interference signal is applied to the receiving electrode 21 from the interference signal generator 22, and FIG. 7 c shows a 1.4 MHz, 500 mVpp interference signal from the interference signal generator 22. Represents the output of the demodulator 233 when is applied to the receiving electrode 21.
As shown in the figure, when the interference signal is applied to the reception electrode 21 as compared with the case where the interference signal is not applied to the reception electrode 21, the reception sensitivity of the demodulator 233 is somewhat reduced. It can be seen that the signal transmitted to the receiving electrode 21 via the human body 3 can be correctly demodulated.

  Here, in FIG. 7d, as a comparative example regarding the frequency of the interference signal, the user's hand carrying the transmitter 1 is brought into contact with the cover of the reception electrode 21 of the receiver 2 as shown in FIG. This represents the output of the demodulator 233 when a disturbance signal of 2.0 MHz and 500 mVpp is applied from the interference signal generator 22 to the reception electrode 21 when the character code “a” is serially transmitted as communication data from the machine 1.

As shown in the figure, when a disturbance signal of 2.0 MHz and 500 mVpp is applied to the reception electrode 21, the demodulator 233 can demodulate the signal transmitted from the transmitter 1 to the reception electrode 21 via the human body 3. Disappear.
Now, in summary, when a disturbing signal of 1.2 MHz, 1.3 MHz, or 500 mVpp is applied from the disturbing signal generator 22 to the receiving electrode 21, the demodulator 233 based on the signal radiated from the transmitter 1 and propagated through the space. It is impossible to prevent demodulation in
When a disturbing signal of 1.4 MHz and 500 mVpp is applied to the receiving electrode 21 from the disturbing signal generator 22, it is possible to prevent demodulation in the demodulator 233 by a signal radiated from the transmitter 1 and propagated through the space, and The demodulator 233 can correctly demodulate the signal transmitted from the transmitter 1 to the receiving electrode 21 via the human body 3.

  When a disturbance signal of 2.0 MHz and 500 mVpp is applied to the reception electrode 21, demodulation in the demodulator 233 by a signal radiated from the transmitter 1 and propagated in space can be prevented. It also becomes impossible to correctly demodulate the signal transmitted from the transmitter 1 to the receiving electrode 21 via the human body 3.

  Therefore, by appropriately selecting the frequency and magnitude of the interference signal, the demodulator 233 ensures that the signal transmitted from the transmitter 1 to the receiving electrode 21 via the human body 3 is correctly demodulated, while the transmitter It can be seen that the demodulation in the demodulator 233 by the signal radiated from 1 and propagated through the space can be prevented.

  Here, as shown in FIG. 8a, in a state where a disturbance signal of 1.4 MHz and 500 mVpp is applied to the receiving electrode 21, neither the transmitter 1 nor the user exists near the receiving electrode 21 of the receiver 2. The output of the amplifier 232 of the receiving unit 23 is shown in FIG. 8c, when a user who does not carry the transmitter 1 is in contact with the cover of the receiving electrode 21 of the receiver 2 while a disturbance signal of 1.4 MHz and 500 mVpp is applied to the receiving electrode 21, as shown in FIG. FIG. 8d shows the output of the amplifier 232 of the receiver 23 of the receiver 2 of FIG.

8B and 8D, when the human body 3 contacts the cover of the reception electrode 21, it can be seen that the interference signal component input to the electric field sensor 231 becomes small. Here, it is considered that this is because part of the interference signal applied to the reception electrode 21 is directed to the human body 3 due to capacitive coupling between the reception electrode 21 and the human body 3.
Thus, when a disturbance signal of 1.4 MHz and 500 mVpp is applied to the reception electrode 21, the signal is transmitted from the transmitter 1 to the reception electrode 21 via the human body 3 in the demodulator 233 regardless of the interference signal. The reason why the received signal can be correctly demodulated is that the human body 3 comes into contact with the cover of the receiving electrode 21, and as a result, the receiving electrode 21 and the human body 3 are capacitively coupled. The component of the disturbance signal input to the electric field sensor 231 becomes smaller and the frequency characteristic of the reception sensitivity of the electric field sensor 231 shown in FIG. 3 indicates that the component of the disturbance signal of 1.4 MHz is higher than the peak value of 1.9 MHz. This is considered to be due to attenuation of about 85%.

  In addition, unlike a disturbance signal of 1.4 MHz and 500 mVpp, when a disturbance signal of 2.0 MHz and 500 mVpp is applied to the reception electrode 21, the reception signal is transmitted from the transmitter 1 through the human body 3 in the demodulator 233 by the interference signal. The reason why the signal transmitted to 21 cannot be demodulated correctly is considered to be that the attenuation width of the interference signal according to the frequency characteristic of the reception sensitivity of the electric field sensor 231 shown in FIG.

  The embodiment of the present invention has been described above.

  DESCRIPTION OF SYMBOLS 1 ... Transmitter, 2 ... Receiver, 3 ... Human body, 11 ... Transmission side data processing part, 12 ... Modulator, 13 ... Transmission electrode, 21 ... Reception electrode, 22 ... Interference signal generation part, 23 ... Reception part, 231 ... electric field sensor, 232 ... amplifier, 233 ... demodulator, 234 ... reception side data processing unit.

Claims (3)

A transmitter that receives the communication data via an electric field induced around the living body by applying a modulation signal obtained by modulating the communication data to the living body;
A receiving electrode placed under an electric field around the living body during communication;
A receiving unit that converts an electric field applied to the receiving electrode from the living body into the modulated signal, and demodulates the converted modulated signal into the communication data;
A receiver having an interference signal generation unit for applying an interference signal for disturbing the modulation signal to the reception electrode. The receiver according to claim 1, wherein
The modulated signal is a signal obtained by ASK modulating the communication data,
The receiver according to claim 1, wherein the interference signal is a signal having a predetermined frequency.   3. A communication system comprising: the receiver according to claim 1; and a transmitter that applies a modulated signal obtained by modulating communication data to a living body to induce an electric field around the living body.