JP3993578B2 - Electric field communication system - Google Patents

Description

  The present invention relates to an electric field communication system that performs electric field communication using a plurality of transceivers.

In a vehicle body such as an airplane or a train where it is difficult to install a large number of cables, it is difficult to construct a network using a large number of terminals. Therefore, an electric field communication system that facilitates installation of a large number of terminals by arranging a transceiver that induces an electric field without using a cable for communication connection between terminals and performing electric field communication has been studied (Patent Literature). 1).
JP 2003-324395 A

  However, even if an electric field is induced using a transceiver in a vehicle body that can be said to be a large electric field transmission medium such as an airplane or a train, the attenuation of the electric field is large and the range in which communication can be performed is limited. There is a problem that it is difficult to construct a network.

  The present invention has been made in view of the above, and an object thereof is to provide an electric field communication system capable of constructing a large-scale electric field communication network in an electric field transmission medium.

  An electric field communication system according to a first aspect of the present invention is an electric field communication system in which a plurality of first repeaters and second repeaters that relay electric field communication by a plurality of transceivers are alternately arranged. And detecting means for detecting only a signal having a frequency to be transmitted, and transmitting means for transmitting a signal at a frequency that can be detected only by the first repeater. The first repeater has a frequency at which the transceiver and the second repeater transmit. Detection means for detecting a signal, conversion means for converting the frequency of the detected signal into a frequency detectable by both the transceiver and the second repeater, and transmission means for transmitting the converted signal, Two repeaters are detection means for detecting only the signal of the frequency transmitted by the first repeater, and only the first repeater can detect the frequency of the detected signal. Conversion means for converting the a frequency, and a sending means for transmitting the converted signal.

  In the present invention, the transceiver, the first repeater, and the second repeater respectively transmit or detect the frequency of the signal transmitted or detected so that the transceiver communicates only with the first repeater and the second repeater communicates only with the first repeater. By setting and alternately arranging the first repeater and the second repeater, each transceiver can communicate over a wide range through the first repeater and the second repeater.

  The electric field communication system according to the second aspect of the present invention is characterized in that the first repeaters are arranged vertically and horizontally, and the second repeaters are arranged between the first repeaters.

  The electric field communication system according to a third aspect of the present invention is characterized in that the signal delay times of the second repeaters are alternately different in units of columns in either the vertical direction or the horizontal direction.

  In the present invention, the first repeater and the second repeater are arranged in the vertical and horizontal directions by alternately changing the signal delay time of each second repeater in units of columns in either the vertical direction or the horizontal direction. In the minimum unit area formed by the above, the transmission time is different in the two types of signal transmission paths from the first repeater that transmitted the signal to another first repeater that is located on the opposite side. A single repeater prevents signals having the same frequency from being detected simultaneously.

  The electric field communication system according to a fourth aspect of the present invention is characterized in that the second repeater does not transmit when detecting signals of two or more types of frequencies before starting transmission.

  In the present invention, when the second repeater detects a signal of two or more types of frequencies before the start of transmission, the second repeater performs a process of not performing transmission, so that the second repeater is located on the diagonal from the first repeater. When a signal is transmitted through one of the two types of transmission paths to the first repeater of the second repeater, the second repeater that has received the signal transmitted by the other first repeater can also be transmitted from another path. Since the signal is received, the transmission of the signal is not started, the signal is not transmitted from the second repeater to the other first repeater, and the signal of the same frequency is received by the other first repeater. Interference is prevented from interfering with communication.

  In the electric field communication system according to the fifth aspect of the present invention, the first repeater and the second repeater select a signal with the frequency detected first as an output target, and select to block a signal with the frequency detected later It has the means, respectively.

  In the present invention, the first repeater and the second repeater both select the signal of the frequency detected first, convert the frequency and output it, while blocking the signal of the frequency detected later. Thus, even if a signal of another frequency is received during transmission of the earliest signal at each repeater, the transmission signal is not affected.

  In the electric field communication system according to the sixth aspect of the present invention, a region where 3 × 2 first repeaters are arranged is set as a minimum unit region, and each of the detection means detects signals of three types of frequencies, The converting means converts the frequency of the detected signal into a different frequency.

  In the present invention, a region surrounded by 3 × 2 first repeaters is used as a minimum unit, and signals of three kinds of frequencies are detected by each of the transceiver, the first repeater, and the second repeater, and the first In the repeater and the second repeater, the frequency of the detected signal is converted into a different frequency, and a total of six types of frequencies are used so that the transceiver is placed between the two first repeaters on the diagonal. Even so, the transceiver transmits signals of different frequencies from the two first repeaters.

  As described above, according to the electric field communication system according to the present invention, a large-scale electric field communication network can be constructed within the electric field transmission medium.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
In this embodiment, an electric field communication system that uses four types of carrier frequencies f1, f2, f3, and f4 as an example and performs communication by half-duplex carrier band transmission will be described.

  FIG. 1 is a functional block diagram showing a configuration of a transceiver 1 used in the electric field communication system of the present embodiment. The transceiver 1 in FIG. 1 includes a transmission / reception electrode 11, an electric field detection optical unit 12, a signal processing unit 13, a frequency selection unit 14, a demodulation circuit 15, a waveform shaping unit 16, a switch 17, a modulation circuit 18, an oscillator 19, and an I / O circuit. 4.

  During transmission, the transceiver 1 modulates the signal transmitted from the terminal 5 through the I / O circuit 4 by the modulation circuit 18 using the carrier frequency of the frequency f1 output from the oscillator 19, and transmits the modulated signal to the transmission / reception electrodes. 11, an electric field is induced by the transmission / reception electrode 11 and transmitted to the outside. A switch 17 is connected between the modulation circuit 18 and the transmission / reception electrode 11. During transmission, the switch 17 is turned on and a signal is output from the modulation circuit 18 to the transmission / reception electrode 11. The switch 17 may be replaced with a notch filter that has a high impedance for the frequencies f2 and f4 and a low impedance for the frequency f1. When the notch filter is used, the received signals with the frequencies f2 and f4 are blocked by the notch filter and input to the electric field detection optical unit 12 without being attenuated, and the transmitted signal with the frequency f1 passes and is output to the transmission / reception electrode 11. Is done.

  During reception, the transceiver 1 receives an electric field from the outside by the transmission / reception electrode 11, converts the electric field received by the electric field detection optical unit 12 into an electric signal, and a signal processing unit 13 amplifies the electric signal, removes noise, and performs carrier Signal processing such as filtering for allowing only the signals of the frequencies f2 and f4 to pass is performed. The frequency selection unit 14 selects and outputs the signal received first among the signals having carrier frequencies f2 and f4, and blocks the other frequency signal so that it is not output. The demodulation circuit 15 demodulates the signal selected by the frequency selection unit 14, and the waveform shaping unit 16 performs waveform shaping for improving waveform distortion and preventing 0 and 1 determination errors. The reception signal processed in this way is transmitted to the terminal 5 via the I / O circuit 4. At the time of reception, the switch 17 is turned off so that the signal received by the transmission / reception electrode 11 is not propagated to the circuit on the transmission side.

  FIG. 2 is a functional block diagram showing the configuration of the first repeater 2 used in the electric field communication system of the present embodiment. The first repeater 2 shown in FIG. 1 includes a transmission / reception electrode 21, an electric field detection optical unit 22, a signal processing unit 23, a frequency conversion unit 24, and a notch filter 25.

  The first repeater 2 receives an electric field from the outside by the transmission / reception electrode 21, converts the electric field received by the electric field detection optical unit 22 into an electric signal, and the signal processing unit 23 amplifies the electric signal, removes noise, and performs carrier frequency. Signal processing such as filtering for passing only the signals of f1 and f3 is performed. The frequency conversion unit 24 converts the carrier frequency to f2 when the carrier frequency of the detected signal is f1, and converts the carrier frequency to f4 when the carrier frequency of the detected signal is f3. In addition, the frequency conversion unit 24 performs signal conversion on the previously received signal out of the signals with carrier frequencies f1 and f3 and outputs the signal, and blocks the other frequency signal so that it is not output. Also do.

  A notch filter 25 having a high impedance for the carrier frequencies f1 and f3 and a low impedance for the carrier frequencies f2 and f4 is connected between the frequency converter 24 and the transmission / reception electrode 21. The signals of the carrier frequencies f1 and f3 received by the electrode 21 are blocked by the notch filter 25 and input to the electric field detection optical unit 22 without being attenuated.

  FIG. 3 is a functional block diagram showing the configuration of the second repeater 3 used in the electric field communication system of the present embodiment. The second repeater 3 in the figure has a configuration including a transmission / reception electrode 31, an electric field detection optical unit 32, a signal processing unit 33, a frequency conversion / delay unit 34, and a notch filter 35.

  The second repeater 3 receives an external electric field by the transmission / reception electrode 31, converts the electric field received by the electric field detection optical unit 32 into an electric signal, and the signal processing unit 33 amplifies the electric signal, removes noise, and performs carrier frequency. Signal processing such as filtering for passing only the signals of f2 and f4 is performed. The frequency conversion / delay unit 34 converts the carrier frequency to f3 when the carrier frequency of the detected signal is f2, and converts the carrier frequency to f1 when the carrier frequency of the detected signal is f4. The frequency-converted signal is delayed by a predetermined time and transmitted to the transmission / reception electrode 31. Two types of delay time a and b can be set.

  The frequency converting / delaying unit 34 outputs the signal received earlier among the signals having the carrier frequencies f2 and f4, and blocks the other frequency signal so that it is not output. Further, the output signal is fed back to the frequency conversion / delay unit 34, and when a signal of two types of frequencies is received before the signal is transmitted by the transmission / reception electrode 31, transmission of the signal is immediately stopped. Process.

  A notch filter 35 is connected between the frequency conversion / delay unit 34 and the transmission / reception electrode 31. The notch filter 35 has high impedance for the carrier frequencies f2 and f4 and low impedance for the carrier frequencies f1 and f3. The signals of the carrier frequencies f2 and f4 received by the transmission / reception electrode 31 are blocked by the notch filter 35 and input to the electric field detection optical unit 32 without being attenuated.

  With the configuration as described above, the transceiver 1 can transmit and receive only with the first repeater 2, and the second repeater 3 can transmit and receive only with the first repeater 2. In addition, the first repeater 2 and the second repeater 3 convert the frequency of the input signal to another frequency, thereby preventing waveform distortion of the output signal caused by the feedback received by the repeater itself. Is also possible.

  FIG. 4 is a diagram showing a configuration of the electric field communication system in the present embodiment in which the transceiver 1, the first repeater 2, and the second repeater 3 are arranged. In the figure, a white square indicates the transceiver 1, a hatched circle indicates the first repeater 2, and a white circle indicates the second repeater 3. The letter TRx above the white square indicates the transceiver number, and the letter R above the circle indicates the repeater number. The characters in the white circles indicate the delay time (a or b) of the second repeater.

  As shown in the figure, the first repeater and the second repeater are alternately arranged. Specifically, the first repeaters 2 are arranged in a grid pattern at regular intervals in the vertical and horizontal directions, and the second repeaters 3 are arranged in the middle of the first repeaters 2. As for the arrangement of the second repeaters 3, those having the delay times a and b are alternately arranged in the horizontal row of the figure, and those having the same delay time are arranged in the vertical column.

  Each first repeater 2 is adjusted in intensity of transmission output so that the first repeaters do not communicate with each other. Each second repeater 3 also adjusts the strength of the transmission output so that the second repeaters do not communicate with each other.

  In the electric field communication system, the transceiver 1, the first repeater 2, and the second repeater 3 transmit and receive signals so that the transceiver 1 transmits and receives only with the first repeater 2 and the second repeater 3 transmits and receives only with the first repeater 2. The first repeater is arranged vertically and horizontally and the second repeater is arranged between the first repeaters, so that each transceiver can communicate over a wide range through the first repeater and the second repeater.

  Next, the operation of this electric field communication system will be described with reference to FIG. This figure shows the flow of signal transmission when the transceiver TRx7 transmits a signal. In the figure, a region formed by 2 × 2 first transceivers is defined as a minimum unit region.

  When the transceiver TRx7 transmits a signal at the frequency f1, the first repeater R12 receives it, converts the frequency to f2, and transmits it to the peripheral second repeaters R8, R11, R13, and R17. The transmission path until this signal reaches the first repeater R5 that is diagonally located in the minimum unit region with respect to the first repeater R12 is the path 1 of R12 → R8 → R3 → R4 → R5, and R12 → R13. There are two routes 2 of R14 → R9 → R5. When the lengths of these paths are the same, assuming that the delay times of the signals at the second repeater are all the same, the signal of the frequency f1 transmitted by the second repeater R4 is sent to the first repeater R5. Then, the signal of the frequency f1 transmitted from the second repeater R9 is input, causing interference such as cancellation of signals of the same frequency, and signal transmission cannot be performed accurately.

  Therefore, in the present embodiment, the signal delay time of each second repeater in each horizontal column shown in FIG. Here, the delay time is set to a <b. With this configuration, in the transmission time from the first repeater R12 to the first repeater R5, the route 1 is made faster than the route 2 so that signals of the same frequency are not simultaneously input to the first repeater R5. .

  The first repeater R5 receives the signal of the frequency f1 from the second repeater R4, converts it to the frequency f2, and transmits it to the peripheral transceiver TRx3 and the second repeaters R6 and R9.

  Since the second repeater R9 receives signals of two types of frequency, that is, the signal from the first repeater R5 and the signal from the first repeater R14 before signal transmission, the frequency conversion / delay unit 34 Processing to stop transmission is performed, and transmission of the signal to the first repeater R5 is blocked.

  Further, another repeater in these paths, for example, the second repeater R13, receives the signal of the frequency f2 from the first repeater R12, converts it to the frequency f3, and transmits it to the first repeater R14. Even if the frequency f4 signal transmitted by the first repeater R14 is received, the frequency converter 24 uses the signal processing for cutting off the frequency f4 signal to cause the repeater to mix the signal of the frequency f4 signal with the frequency f2 signal. I do not output.

  In each transceiver, when the electric field detection optical unit 12 detects a signal having a carrier frequency of f2 or f4, a process of selecting and outputting the previously detected signal and blocking signals of other frequencies is performed. This is performed by the frequency selector 14. As a result of this processing, as shown in FIG. 5, for example, even when the transceiver TRx5 is located between the first repeater R12 and the first repeater R14, the transceiver TRx5 only uses the terminal 5 for the previously detected signal. To prevent the output of a signal obtained by interfering with a signal received earlier and a signal received later.

  Therefore, according to the present embodiment, the transceiver 1, the first repeater 2, and the second repeater 3 are configured such that the transceiver 1 transmits and receives only to the first repeater 2, and the second repeater 3 transmits and receives only to the first repeater 2. Since each transceiver 1 can communicate over a wide range through the first repeater 2 and the second repeater 3 by setting the frequency of the signal to be transmitted and received and alternately arranging the first repeater and the second repeater, A large-scale electric field communication system can be constructed.

  According to the present embodiment, the first repeaters 2 are arranged vertically and horizontally, the second repeaters 3 are arranged between the first repeaters 2, and the signal delay times of the second repeaters 3 are alternately arranged in units of columns in the horizontal direction. Since the first repeater 2 and the second repeater 3 are arranged in the vertical and horizontal directions in the minimum unit area, the second repeater 2 that is opposite to the first repeater 2 that has transmitted the signal is provided. Since the transmission times are different in one signal transmission path, it is possible to prevent signals having the same frequency from being simultaneously detected by the other first repeater 2, thereby preventing the occurrence of collision. Note that the signal delay times of the second repeaters may be alternately changed in units of columns in the vertical direction.

  According to the present embodiment, when the second repeater 3 disposed between the first repeaters detects a signal having two or more types of frequencies before starting transmission, the second repeater 3 performs a process of not transmitting a signal. When a signal is transmitted from one first repeater 2 to another first repeater 2 on the opposite side through one of the two transmission paths, the signal transmitted by the other first repeater 2 is transmitted. Since the second repeater 3 that has received the signal receives a signal from another route and stops the transmission of the signal, interference caused by the reception of the same frequency signal by the other first repeater 2 is performed. Can be prevented.

  According to the present embodiment, the first repeater 2 and the second repeater 3 both select the signal of the frequency detected first, and convert and transmit this frequency, while the frequency of the frequency detected later By blocking the signal and not performing frequency conversion and output, signal feedback is prevented, and even if a signal with a different frequency is received during transmission of the earliest signal, effects such as interference with the transmitted signal are prevented. be able to.

[Second Embodiment]
In the first embodiment, for example, when the transceiver TRx5 is arranged between the first repeater R12 and the first repeater R5, the transceiver TRx5 has the same carrier frequency f2 from the first repeaters R12 and R5. Signals will be received and these signals will cause interference. In the electric field communication system in the present embodiment, in order to prevent such interference, signal transmission is performed using six types of carrier frequencies.

  FIG. 6 is a functional block diagram showing the configuration of the transceiver 41 used in the electric field communication system of the present embodiment. In the transceiver 41 shown in the figure, the electric field detection optical unit 42 and the signal processing unit 13 detect signals having carrier frequencies f2, f4, and f6. The frequency selection unit 44 selects and outputs the signal having the earliest received frequency among the signals having carrier frequencies f2, f4, and f6, and blocks the signals having other frequencies. In addition, the same thing as FIG. 1 shall be attached | subjected the same code | symbol, and the overlapping description is abbreviate | omitted here.

  FIG. 7 is a functional block diagram showing the configuration of the first repeater 51 used in the electric field communication system of the present embodiment. In the first repeater 51 in the figure, the electric field detection optical unit 52 and the signal processing unit 23 detect signals having carrier frequencies f1, f3, and f5. The frequency converter 54 converts the carrier frequency to f2 when the carrier frequency of the detected signal is f1, and converts the carrier frequency to f4 when the carrier frequency of the detected signal is f3. When the carrier frequency of the received signal is f5, the carrier frequency is converted to f6. Further, the frequency conversion unit 54 converts the frequency of the signal received first among the signals having carrier frequencies f1, f3, and f5 and outputs the signal, and blocks signals of other frequencies.

  The notch filter 55 connected between the frequency converter 54 and the transmission / reception electrode 21 has a high impedance for the carrier frequencies f1, f3, and f5 and a low impedance for the carrier frequencies f2, f4, and f6. It shall be of a characteristic. In addition, the same code | symbol shall be attached | subjected to the same thing as FIG. 2, and the overlapping description is abbreviate | omitted here.

  FIG. 8 is a functional block diagram showing a configuration of the second repeater 61 used in the electric field communication system of the present embodiment. In the second repeater 61 in the figure, the electric field detection optical unit 62 and the signal processing unit 33 detect signals having carrier frequencies f2, f4, and f6. The frequency conversion / delay unit 64 converts the carrier frequency to f3 when the carrier frequency of the detected signal is f2, and converts the carrier frequency to f5 when the carrier frequency of the detected signal is f4. When the carrier frequency of the detected signal is f6, the carrier frequency is converted to f1, and then the frequency-converted signal is delayed by a predetermined time and transmitted to the transmission / reception electrode 31. Two types of delay time a and b (a <b) can be set.

  The frequency conversion / delay unit 64 outputs the signal received first among the signals having carrier frequencies f2, f4, and f6, and blocks signals of other frequencies. Further, the output signal is fed back to the frequency conversion / delay unit 64, and the input signal is compared with the output signal. When a signal is received, signal output is immediately stopped.

  The notch filter 65 connected between the frequency conversion / delay unit 64 and the transmission / reception electrode 31 has a high impedance for the carrier frequencies f2, f4, and f6, and a low impedance for the carrier frequencies f1, f3, and f5. It shall be of the characteristic that becomes. In addition, the same code | symbol shall be attached | subjected to the same thing as FIG. 3, and the overlapping description is abbreviate | omitted here.

  FIG. 9 is a diagram showing a configuration of the electric field communication system in the present embodiment in which the transceiver 41, the first repeater 51, and the second repeater 61 are arranged. In the electric field communication system shown in the figure, a rectangular region in which three first repeaters 51 are arranged in the vertical direction and two in the horizontal direction is set as a minimum unit region, and the second repeater 61 is arranged on the outer periphery of this region. It arrange | positions between 1st repeaters. The meaning of each symbol in the figure is the same as in FIG. 5, and the frequency transmitted and received by each transceiver and each repeater is as shown in the figure.

  The figure shows the state of signal transmission when the transceiver TRx6 generates a signal. The signal of the frequency f1 generated by the transceiver TRx6 is received by the first repeater R18, converted to the frequency f2, and transmitted. This signal is received by another first repeater R12 located diagonally to the first repeater R18 via the paths R19, R20, and R15. The first repeater R12 transmits a signal having a frequency f6 as shown in FIG.

  The transceiver TRx3 is located between the first repeater R18 and the first repeater R12, but the frequency of the signal generated by each of the first repeaters R18 and R12 is different, and is detected first by the frequency selector 44. Since signals having different frequencies are selected, the occurrence of interference due to signals having the same frequency can be prevented.

  The transceiver TRx3 is located between the first repeater R11 and the first repeater R20, and these first repeaters R11 and R20 transmit signals at the same frequency, but the transceiver TRx3. After the signal selected by the first repeater R18 is first selected by the frequency selector 44, the signals transmitted by the first repeaters R11 and R20 are output from the transceiver TRx3. There will be no interference.

  Therefore, according to the present embodiment, a region surrounded by 3 × 2 first repeaters is set as a minimum unit, and signals of three kinds of frequencies are respectively transmitted from the transceiver 41, the first repeater 51, and the second repeater 61. In addition to the detection, the first repeater 51 and the second repeater 61 use a total of six types of frequencies so that the frequency of the detected signal is converted to another frequency, so that the position of the minimum unit region is located diagonally. Even if the transceiver is placed between the two first repeaters, signals having different frequencies are transmitted to the transceiver from the two first repeaters on the diagonal, so that interference due to these signals is prevented. be able to.

  In the present embodiment, the transceiver TRx3 has been described as an example, but it is needless to say that interference can be similarly prevented in other transceivers.

It is a functional block diagram which shows the structure of the transceiver used for the electric field communication system in 1st Embodiment. It is a functional block diagram which shows the structure of the 1st repeater used for the electric field communication system in 1st Embodiment. It is a functional block diagram which shows the structure of the 2nd repeater used for the electric field communication system in 1st Embodiment. It is a figure which shows the structure of the electric field communication system in 1st Embodiment. It is a figure which shows the mode of the signal transmission in the electric field communication system of FIG. It is a functional block diagram which shows the structure of the transceiver used for the electric field communication system in 2nd Embodiment. It is a functional block diagram which shows the structure of the 1st repeater used for the electric field communication system in 2nd Embodiment. It is a functional block diagram which shows the structure of the 2nd repeater used for the electric field communication system in 2nd Embodiment. It is a figure which shows the mode of the structure of the electric field communication system and signal transmission in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,41 ... Transceiver 2,51 ... 1st repeater 3,61 ... 2nd repeater 4 ... I / O circuit, 5 ... Terminal 11,21,31 ... Transmission / reception electrode 12,22,32 ... Electric field detection optical part 13,23 , 33 ... Signal processing unit 14, 44 ... Frequency selection unit 15 ... Demodulation circuit 16 ... Waveform shaping unit 17 ... Switch 18 ... Modulation circuit 19 ... Oscillator 24, 54 ... Frequency conversion unit 25, 35, 55, 65 ... Notch filter 34 , 64 ... Frequency conversion / delay unit 42, 52, 62 ... Electric field detection optical unit

Claims (6)

An electric field communication system in which a plurality of first repeaters and second repeaters that relay electric field communication by a plurality of transceivers are alternately arranged,
The transceiver has detection means for detecting only a signal of a frequency transmitted by the first repeater, and transmission means for transmitting a signal at a frequency detectable only by the first repeater,
The first repeater detects a signal having a frequency transmitted by the transceiver and the second repeater, and converts a frequency of the detected signal into a frequency detectable by both the transceiver and the second repeater; Transmitting means for transmitting the converted signal;
The second repeater includes a detecting unit that detects only a signal having a frequency transmitted by the first repeater, a converting unit that converts the frequency of the detected signal into a frequency that can be detected only by the first repeater, and a converted signal. An electric field communication system comprising: a transmission means for transmitting   2. The electric field communication system according to claim 1, wherein the first repeaters are arranged vertically and horizontally, and the second repeaters are arranged between the first repeaters.   3. The electric field communication system according to claim 2, wherein the signal delay times of the second repeaters are alternately different in units of columns in either the vertical direction or the horizontal direction.   The electric field communication system according to any one of claims 1 to 3, wherein the second repeater does not perform transmission when signals of two or more types of frequencies are detected before transmission is started.   The first repeater and the second repeater each include a selection unit that selects a signal having a frequency detected first as an output target and then blocks a signal having a frequency detected thereafter. 5. The electric field communication system according to any one of 1 to 4. The area where the 3 × 2 first repeaters are arranged is the minimum unit area,
Each of the detecting means detects signals of three types of frequencies,
6. The electric field communication system according to claim 1, wherein each of the conversion units converts the frequency of the detected signal into a different frequency.

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