KR100793145B1 - Apparatus and method of transmitting and receiving for human body communication - Google Patents

Abstract

A transmit-receive apparatus for human body communication and a method thereof are provided to reduce power density and minimize interference on an adjacent wireless device by widening the bandwidth of a signal to transmit, without using a carrier. A transmitting unit in a transmit-receive apparatus for human body communication comprises a source encoder(110), a bit repeater(121), a pseudo random code AND gate(131), a Manchester encoder(141), and a transmitting electrode(160). The source encoder(110) converts the original signal, which is analog, into a digital signal. The bit repeater(121) repeats the bits of the digital signal, outputted from the source encoder(110), "n" times. The pseudo random code AND gate(131) executes logical conjunction for the digital signal, outputted from the bit repeater(121), with a pseudo random code. The Manchester encoder(141) performs Manchester coding for the digital signal outputted from the pseudo random code AND gate(131). The transmitting electrode(160) sends the Manchester code, outputted from the Manchester encoder(141), to the human body.

Description

Apparatus and method of transmitting and receiving for human body communication

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view for explaining a conventional apparatus for transmitting a human body communication using a binary phase shift keying (BPSK) narrowband modulation scheme;

2 is a diagram for explaining a transmission apparatus for human body communication according to the present invention using a wideband modulation method without a carrier wave;

3 is a graph for explaining the power density of a signal modulated by the direct sequence spread spectrum technique;

4 is a diagram for explaining a Manchester coding technique;

5 is a graph for explaining the power density of a Manchester coded signal;

6 is a view for explaining a receiver for human body communication according to the present invention.

<Description of reference numbers for the main parts of the drawings>

10, 110: source encoder 20: channel encoder

30, 220: low pass filter 40: frequency mixer

50, 150, 220: amplifier 60, 160: transmitting electrode

70, 170: human body 121: beat repeater

131, 270: pseudorandom code logic multiplier

135: Pseudorandom code 141: Manchester encoder

210: receiving electrode 230: Manchester template multiplier

250: comparator 280: bit integrator

290: source decoder

The present invention relates to a transmission and reception apparatus and method for a human body communication, and more particularly, to a transmission and reception apparatus and method for a human body communication using a broadband modulation method without using a carrier wave.

The data transmission method using the human body has many advantages in terms of cost and power consumption compared to the human area transmission method based on RF technology such as Brutus and Zigbee. Accordingly, in recent years, studies on the characteristics of the human body as a signal transmission medium have been actively conducted, and a human body communication transceiver has been developed based on the results.

According to the research results, the human body is a band pass filter having a pass band of 5 MHz to 30 MHz, and the signal transmission characteristic is maximized around 10 MHz. In order to minimize attenuation of a signal by a human body and maximize communication performance, a conventional human communication transceiver adopts a narrowband modulation method that carries a digital signal to be sent on a 10 MHz carrier.

1 is a diagram illustrating a conventional apparatus for transmitting human body communication using a binary phase shift keying (BPSK) narrowband modulation scheme. Referring to FIG. 1, an original signal to be sent such as an audio or a video is converted into a digital signal through a source encoder 10, and the converted digital signal is insensitive to external noise via a channel encoder 20 and is detected by an error. The signal is converted back into a correctable signal.

The processed signal in the digital domain through the channel encoder 20 becomes a baseband analog signal through the low frequency pass filter 30, and the baseband analog signal is loaded on the 10 MHz carrier 45 in the frequency mixer 40 and the frequency. The band is moved to the pass band of the human body 70. The analog signal transferred to the pass frequency band of the human body 70 is transmitted to the human body 70 through the output amplifier 50 and the transmission electrode 60. The signal transmitted to the human body 70 arrives at the receiver (not shown) via the human body 70 and the signal reached to the receiver is restored to the original signal using a conventional demodulation method.

As described above, the conventional apparatus for transmitting human body communication uses a narrowband modulation scheme to move a baseband signal to a frequency near 10 MHz, which is an optimal passband of the human body. However, this narrowband transmission method has a disadvantage that the filter 30, which is difficult to integrate, should be used as an external device, and the data rate is also limited because the frequency of the carrier 45 is fixed at 10 MHz.

In addition, since the human body 70 not only acts as a signal transmission medium but also serves as an antenna for transmitting a signal to the outside of the human body, the human body 70 may provide an interference signal to wireless equipment operating in the 10 MHz band. In particular, the narrowband signal transmission method has a high power density, so the size of the interference signal increases rapidly, which is likely to malfunction the neighboring wireless equipment.

Accordingly, an object of the present invention is to provide a transmission and reception apparatus and method for human communication that can solve the above-mentioned problems by moving a baseband signal to a human passing band using only a coding technique without using a carrier wave. .

According to an aspect of the present invention, there is provided a transceiver for human body communication, comprising: a source encoder for converting an analog original signal into a digital signal; A bit repeater for repeating N times the bits of the digital signal output from the source encoder; A pseudo random code logical multiplier for logically multiplying a pseudo random code with the digital signal output from the bit repeater; A Manchester encoder for Manchester coding the digital signal output from the pseudorandom code logic multiplier; And a transmitting electrode configured to transmit a Manchester code outputted from the Manchester encoder to a human body. Equipped with
The receiving device may include: a receiving electrode receiving a Manchester code transmitted from the transmitting electrode and passing through a human body; A Manchester template multiplier multiplying the Manchester code input from the receiving electrode with a Manchester code template in which 1 and -1 are periodically repeated; A comparator for outputting bit 1 if the Manchester code output from the Manchester template multiplier is greater than 0 and outputting bit 0 if less than 0; A pseudorandom code logical multiplier for logically multiplying a bit signal output from the comparator with a pseudo random code multiplied by a pseudo random code logical multiplier of the transmitter; A bit integrator for integrating the bit signal output from the pseudorandom code logic multiplier by 1 / N times the inverse of the repetition multiple N by the bit repeater of the transmitter; And a low frequency pass filter installed between the Manchester mold multiplier and the comparator.

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In the transmission and reception method for human body communication according to the present invention for achieving the above technical problem: The transmission method, the step of converting an analog signal into a digital signal; Modulating the digital signal with direct sequence spread spectrum technology; Manchester coding the digital signal modulated by the direct sequence spread spectrum technique into a Manchester code; And transmitting the Manchester code to a human body.
The receiving method includes amplifying the Manchester code input through the human body; And reconstructing the Manchester code into the digital signal using the direct sequence spread spectrum technique to find information.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. The following examples are only presented to understand the content of the present invention, and those skilled in the art will be capable of many modifications within the technical spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited to these examples.

[Transmitter]

2 is a view for explaining a transmission apparatus for a human body according to the present invention using a wideband modulation method without a carrier wave.

The original signal to be sent, such as audio or video, is converted into a digital signal 110a via the source encoder 110. The bit repeater 121 receives one bit signal and outputs it as N bit signals. For example, after the digital signal 110a having 1, 0, 1, 1 passes through the bit repeater 121 where N = 3, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1 Is converted into a digital signal 121a of 1, 1, and 1, and 12 bits are output. At this time, since the time when one bit is input to the bit repeater 121 and the time when three bits are output from the bit repeater 121 must be the same, the transmission speed of the data must be increased three times.

The digital signal 121a after passing through the bit repeater 121 is logically multiplied with a pseudo random code 135 by an pseudorandom code logical multiplier 131 to generate an irregular bit pattern 131a. do. The pseudorandom code 135 used at this time is shared only between the communicating groups and has a function of encryption.

3 compares the power density of the irregular bit pattern 131a through the pseudorandom code logical multiplier 131 and the original digital signal 110a through the source encoder 110. Referring to FIG. 3, it can be seen that the signal band of the irregular bit pattern 131a is wider by A times and the power density is reduced by 1 / A times than the original digital signal 110a. However, it can also be seen that the low frequency band still contains a significant amount of the power component of the signal.

When the original digital signal 110a is modulated by the Direct Sequence Spread Spectrum (DSSS) technique using the bit repeater 121 and the pseudorandom code logic multiplier 131, the signal band becomes wider. However, the low frequency band has a disadvantage that the power component is significantly included. Since the components of the low frequency band are attenuated severely when passing through the human body, in order to avoid this, Manchester coded the irregular bit pattern 131a output from the pseudorandom code logic multiplier 131 using the Manchester encoder 141. This results in a Manchester code like 141a.

4 is a diagram for explaining a Manchester coding technique. As shown in Fig. 4, the Manchester coding technique changes the polarity of the bit middle from 1 to -1 when representing bit 1, and the polarity of the bit middle from -1 to 1 when representing bit 0. Let's do it. Therefore, in the case of bits 0 and 1, the intervals of 1 and -1 are the same during the signal period, so that the DC components are removed and only the AC components remain.

5 compares the power density of the irregular bit pattern 131a after the modulation by the direct sequence spread spectrum (DSSS) technique and the Manchester code 141a which has passed through the Manchester encoder 141. After Manchester coding, the power density of the signal is reduced and distributed efficiently in the range of 5MHz to 30MHz, which is the passband of the human body.

The Manchester code 141a having passed through the Manchester encoder 141 is amplified by the output amplifier 150 and then transmitted to the human body 170 through the transmission electrode 160.

[Receiving device]

6 is a view for explaining a receiver for human body communication according to the present invention. Referring to FIG. 6, the Manchester code 141a transmitted from the transmitting electrode 160 and received through the human body 170 is input to the receiving electrode 210 and then amplified through the amplifier 220. The amplified Manchester code 220a is multiplied by the Manchester code template 235 where 1 and -1 are periodically repeated in the Manchester template multiplier 230. If bit 1 is received by the Manchester template multiplier 230, the multiplied value has a positive value. If bit 0 is received, the multiplied value is negative.

The comparator 250 outputs bit 1 when the Manchester code 230a output from the Manchester template multiplier 230 is greater than 0, and outputs bit 0 when less than 0. A low frequency pass filter 220 is installed between the Manchester mold multiplier 230 and the comparator 250. When no signal comes from the outside, the Manchester code is multiplied by the input noise to remove high frequency components. It is for.

The pseudorandom code logical multiplier 270 is a pseudo random code 135 that is the same as the pseudo random code 135 multiplied by the pseudo random code logical multiplier 131 of the transmitter to the bit signal 250a from the comparator 250. Logical multiplication

Due to the nature of logical multiplication, if the same value is multiplied twice by the input, the same value as the original signal is output. When multiplying the same pseudorandom code as in the transmitter, the digital signal immediately after passing through the bit repeater 121 of the transmitter is 121a is restored as it is. In this process, the frequency band of the widely distributed signal is gathered again into a narrow area, so that the power density is increased and the noise from the wide band is averaged and the effect is reduced.

The digital signal 121a, which has passed through the pseudorandom code logic multiplier 270, is again multiplied by a bit integrator 280, which is an inverse of the repetition multiple N = 3 by the bit repeater 121 of the transmitter. Integrated and restored to the original digital signal 110a. The digital signal 110a thus restored is provided to the receiver as a voice or a video through the source decoder 190.

Direct Sequence Spread Spectrum (DSSS) represents one bit of data to be sent as a set of bits, and increases the transmission speed to maintain a constant data transmission time, thereby widening the signal band in the frequency domain. Increasing the signal band while keeping the total power of the sending signal constant, the power density (W / Hz) eventually decreases in proportion to the increase of the band, so even if the transmitted signal is transmitted to the outside using the human body as an antenna, The impact is lessened. On the contrary, even when an external radio signal enters the receiver through the human body, a receiver using a wide band can be stabilized with respect to the in-band interference signal. In addition, the encryption code (pseudo random code) can be applied in the process of representing one bit into multiple bits.

However, if the signal is transmitted to the human body with only the direct sequence spread spectrum (DSSS) applied, the transmitted signal contains a lot of low-frequency components, resulting in a lot of power loss through the human body having a bandpass filter characteristic. Therefore, Manchester coding is used to remove low frequency components of the signal and to collect power in the pass band of the human body. By applying the Manchester coding method, it is possible to obtain a signal having low power density as a whole, taking up a wide signal band without having power density in the low frequency band. Therefore, by applying the Manchester coding scheme, the low power density gained through the direct sequence spread spectrum (DSSS) can be further enhanced.

As described above, according to the present invention, since a band of a signal to be transmitted can be widened without using a carrier wave, power density can be reduced, thereby minimizing interference to a neighboring wireless device. In addition, the present invention can easily obtain a data transfer rate of up to 20 Mbps by setting the variable N of the bit repeater to 1 as compared to the conventional narrowband modulation scheme, which has a limitation in increasing the data transfer rate.

Claims (4)

In the human body communication transmitting and receiving device for transmitting and receiving a signal as a medium, The transmitting device, A source encoder for converting an analog original signal into a digital signal; A bit repeater for repeating N times the bits of the digital signal output from the source encoder; A pseudo random code logical multiplier for logically multiplying a pseudo random code with the digital signal output from the bit repeater; A Manchester encoder for Manchester coding the digital signal output from the pseudorandom code logic multiplier; And A transmission electrode for transmitting a Manchester code outputted from the Manchester encoder to a human body; Equipped with The receiving device, A receiving electrode receiving the Manchester code transmitted from the transmitting electrode and passing through the human body; A Manchester template multiplier multiplying the Manchester code input from the receiving electrode with a Manchester code template in which 1 and -1 are periodically repeated; A comparator for outputting bit 1 if the Manchester code output from the Manchester template multiplier is greater than 0 and outputting bit 0 if less than 0; A pseudo random code logical multiplier for logically multiplying a bit signal output from the comparator with a pseudo random code multiplied by a pseudo random code logical multiplier of the transmitter; A bit integrator for integrating the bit signal output from the pseudorandom code logic multiplier by 1 / N times the inverse of the repetition multiple N by the bit repeater of the transmitter; And And a low frequency pass filter installed between the Manchester mold multiplier and a comparator. delete delete In the transmission method for human body communication, which transmits and receives a signal using a human body as a medium, The transmission method, Converting an analog signal into a digital signal; Modulating the digital signal with direct sequence spread spectrum technology; Manchester coding the digital signal modulated by the direct sequence spread spectrum technique into a Manchester code; And And transmitting the Manchester code to a human body. The receiving method, Amplifying the Manchester code input through the human body; And And recovering the Manchester code into the digital signal using the direct sequence spread spectrum technique to find information.

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