CN114665982A - A circuit and method based on human body channel communication - Google Patents

Abstract

The present invention provides a circuit and method based on human body channel communication. The circuit includes a frequency generator, a transmitter, and a receiver. The frequency generator adopts a phase-locked loop structure and includes a transmission mode and a reception mode. In the transmission mode The square wave generated by the crystal oscillator is input into the phase-locked loop frequency multiplication to obtain a clock signal and then input to the transmitter, and in the receiving mode, the square wave generated by the crystal oscillator is frequency multiplied as a demodulated local oscillator signal and input to the receiver; the transmitter includes Frequency divider, data selector, human body driver, the clock signal obtained by multiplying the frequency is divided by the frequency divider, and then the FSK frequency modulation signal is generated by the data selector, and then the signal is transmitted to the human body through the human body driver to drive the electrodes; The receiver amplifies and down-converts the signal transmitted through the human body received by the electrode to a low intermediate frequency, and then performs intermediate frequency amplification after filtering out high-frequency interference, and finally restores the data. The invention has the characteristics of good privacy, high energy efficiency and low power consumption.

Description

A circuit and method based on human body channel communication

technical field

The invention belongs to the field of wireless communication chips, and relates to a circuit and method based on human body channel communication.

Background technique

Today, with the increasing popularity of smart devices such as smartphones and smart watches, the need for energy-efficient wireless communication is growing, enabling stable transmission of high-bit-rate data between devices at lower cost and power consumption. In particular, these needs have received increasing attention in body area communication (BAN). Communication targets in the human body area are usually within a range of less than 2 meters from the human body, covering applications of implantable, wearable devices. Human body channel communication BCC transmits low-frequency signals to confine the signal within the human body, making it difficult for nearby eavesdroppers to intercept key private data, forming a private communication channel. It takes advantage of both wired and wireless transmission. Compared with air, BCC has lower channel attenuation because the human body with better conductivity is used as the medium. Human body channel communication also has the advantage of small size in system design, because it does not require antennas, but uses electrodes for communication. Studies have shown that, compared with traditional wireless transmission methods such as Bluetooth and WIFI, BCC transmission has the highest energy efficiency and the lowest power consumption.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned technical problems existing in the prior art and realize the above-mentioned technology, the present invention proposes a circuit and method based on human body channel communication, and its specific technical scheme is as follows:

A circuit based on human body channel communication, comprising a frequency generator, a transmitter and a receiver, the frequency generator adopts a phase-locked loop structure, includes a transmitting mode and a receiving mode, and inputs a square wave generated by a crystal oscillator in the transmitting mode The phase-locked loop frequency multiplication obtains the clock signal and then inputs it to the transmitter. In the receiving mode, the square wave frequency multiplication generated by the crystal oscillator is used as the demodulated local oscillator signal and input to the receiver; the transmitter includes a frequency divider and a data selector. MUX, human body driver, the clock signal obtained by multiplying the frequency is divided by the frequency divider, and then the FSK frequency modulation signal is generated by the data selector MUX, and then the signal is transmitted to the human body by driving the electrode through the human body driver; The received signal transmitted through the human body is amplified and down-converted to a low intermediate frequency, and the intermediate frequency is amplified after filtering out high-frequency interference, and finally the data is recovered.

Further, the frequency divider includes an N frequency divider and an M frequency divider, the square wave signal generated by the crystal oscillator is multiplied by the phase-locked loop operating in the transmit mode to obtain the clock of the transmitter, and the clock is divided by N by the N frequency divider. Two square waves of different frequencies are obtained after dividing the frequency by the M frequency divider.

Further, the receiver includes: a front-end amplifier fused with a mixer, a low-pass filter, an intermediate frequency amplifier, and a data recovery module, and the front-end amplifier fused with the mixer performs nonlinear nonlinearity on the signals received from the human body and the electrodes. and use the square wave signal generated by the frequency generator in the receiving mode to down-convert the received FSK frequency modulation signal to obtain a low-IF signal after down-conversion; the output of the front-end amplifier fused with the mixer is connected to Low-pass filter, the low-pass filter can low-pass filter the down-converted low-IF signal, filter out high-frequency noise and harmonics, and obtain a sine wave signal and a DC signal; the output of the low-pass filter Connected to the intermediate frequency amplifier, the intermediate frequency amplifier can amplify the low-pass filtered signal again, that is, amplify the sine wave signal and the signal close to DC; the output of the intermediate frequency amplifier is connected to the data recovery module, and the data recovery module adopts half The wave shaping method distinguishes the amplified sine wave signal from the DC signal, and restores the original data through a hysteresis comparator.

Further, the frequency generator includes: a mode switch, a crystal oscillator, a frequency and phase detector, a charge pump, a loop filter, a voltage-controlled oscillator and a frequency divider group, and the frequency divider group includes a first frequency divider and the second frequency divider, the mode switch switches the working mode of the frequency generator, the phase-locked loop in the transmitting mode outputs a X MHz square wave, and the phase-locked loop in the receiving mode outputs a Y MHz square wave; the crystal oscillator generation frequency is The reference signal source of Z MHz is used as the reference frequency of the phase-locked loop. The frequency and phase difference between the signal and the reference frequency signal; the charge pump can amplify the output signal of the frequency and phase detector and charge and discharge the capacitor of the low-pass filter; the loop low-pass filter can make the charge pump The noise and interference components of the output error voltage are filtered out to form the control voltage of the voltage-controlled oscillator; the voltage-controlled oscillator adjusts the output frequency according to the control voltage, and the frequency divider group divides the output frequency and then connects to the frequency and phase discrimination. The device compares with the reference signal source, extracts the phase and frequency information, and forms negative feedback, so that the phase-locked loop gradually locks at the desired X MHz and Y MHz output frequencies.

A method based on human body channel communication, specifically: the transmitter modulates the square wave obtained by frequency doubling in the transmitting mode by N frequency division and M frequency division, and then modulates it through a data selector MUX to obtain an FSK frequency modulation signal, which is driven Then it is transmitted to the human body through the electrodes; the receiver uses the square wave signal obtained by frequency doubling in the receiving mode as a baseband signal, and amplifies, down-converts, low-pass filter, IF amplifies the FSK FM signal received through the human body and the electrode, After the data recovery operation, the original data is recovered.

Beneficial effects:

Compared with the traditional bluetooth, WIFI and other solutions, the present invention utilizes the conductivity of the human body to communicate without requiring an antenna, and has the advantages of low power consumption, miniaturization, good privacy and high energy efficiency.

Description of drawings

Fig. 1 is the circuit schematic diagram of the present invention;

Fig. 2 is the embodiment circuit schematic diagram of the transmitter under the transmitting mode of the present invention;

FIG. 3 is a schematic circuit diagram of an embodiment of a receiver in a receiving mode of the present invention.

Detailed ways

In order to make the objectives, technical solutions and technical effects of the present invention clearer, the present invention will be described in further detail below with reference to the accompanying drawings.

A circuit based on human body channel communication includes a frequency generator, a transmitter and a receiver. The frequency generator is used to generate square wave signals of two frequencies required by the system; the transmitter is used to generate FSK frequency modulation signals and increase the driving capability of the transmitter, so that the transmitter can drive the electrodes and the larger impedance of the human body, The receiver is used for amplifying and down-converting the signal transmitted from the human body received by the electrode to a low intermediate frequency, filtering out high frequency interference through a filter and then performing intermediate frequency amplification, and recovering the data through a data recovery module to realize the demodulation function.

The frequency generator adopts the structure of a phase-locked loop, and includes two modes: a transmitting mode and a receiving mode. The generated square wave is frequency-multiplied as the demodulated local oscillator signal.

Specifically, the frequency generator includes: a mode switch, a crystal oscillator, a frequency and phase detector, a charge pump, a loop filter, a voltage-controlled oscillator, and a frequency divider group, and the frequency divider group includes a first frequency divider and the second frequency divider, the mode switch can switch the working mode of the frequency generator, in the transmission mode, the first frequency divider with a frequency division ratio of 24 is connected to the loop of the phase-locked loop, and the crystal oscillator is generated. The frequency of the 2MHz square wave is multiplied by 24 times, and the 48MHz square wave is output. In the receiving mode, the second frequency divider with a frequency division ratio of 13 is connected to the loop of the phase-locked loop, and the 2MHz square wave generated by the crystal oscillator is frequency multiplied by 13 times, output a 26MHz square wave; the crystal oscillator generates a reference signal source with a frequency of 2MHz, as the reference frequency of the phase-locked loop; the frequency discriminator will divide the output frequency signal and the reference frequency by the frequency divider The signal is processed by frequency and phase discrimination to extract the frequency and phase difference between the output frequency signal and the reference frequency signal; the charge pump can amplify the output signal of the frequency and phase discriminator and charge and discharge the capacitor of the low-pass filter; The loop low-pass filter can filter out the noise and interference components of the error voltage output by the charge pump to form the control voltage of the voltage-controlled oscillator. The voltage-controlled oscillator can adjust the output frequency according to the control voltage, and the frequency divider group divides the output frequency and then connects to the frequency and phase discriminator, compares it with the reference signal source, extracts the phase and frequency information, and forms a negative feedback, so that the The phase locked loop gradually locks to the desired 48MHz or 26MHz output frequency.

As shown in Figure 1, the transmitter circuit of the transmitting mode of the present invention includes: a crystal oscillator, a phase-locked loop, a frequency divider, a data selector MUX, a human body driver, and the frequency divider includes an N frequency divider and an M frequency divider; The generated square wave signal is multiplied by the phase-locked loop working in the transmit mode to obtain the clock of the transmitter, and the transmitter clock is divided by the N frequency divider N and the M frequency divider M to obtain two square waves of different frequencies. , and then select one of the two data selectors MUX to generate a FSK frequency modulation signal, and then drive the electrodes through the human body driver to transmit the signal to the human body.

Specifically, a square wave signal generated by the crystal oscillator is input to a phase-locked loop, and the clock signal is obtained by frequency multiplication; the outputs of the phase-locked loop are respectively connected to the input ends of the N frequency divider and the M frequency divider, and the N frequency divider and the M frequency divider are respectively connected. After frequency division, two square waves of different frequencies are obtained; the outputs of the N frequency divider and the M frequency divider are respectively connected to the input end of the data selector MUX, and a certain channel of signal is controlled by the data signal to pass through, and the output FSK frequency modulation The output of the data selector MUX is connected to the input terminal of the human body driver to drive the electrodes and the larger capacitance of the human body; the output of the human body driver is connected to the medical electrode to transmit the signal to the human body.

The receiver circuit of the receiving mode of the present invention includes: a crystal oscillator, a phase-locked loop, a front-end amplifier fused with a mixer, a low-pass filter, an intermediate frequency amplifier, and a data recovery module, and the front-end amplifier fused with the mixer can The signals received by the human body and the electrodes are amplified nonlinearly, and a square wave signal is generated by a frequency generator in the receiving mode to down-convert the received FSK frequency modulation signal to obtain a down-converted low-IF signal. The low-pass filter can perform low-pass filtering on the down-converted low-IF signal, filter out high-frequency noise and harmonics, and obtain a sine wave signal and a signal close to DC. The intermediate frequency amplifier can amplify the low-pass filtered signal again, that is, amplify the sine wave signal and the signal close to DC, for subsequent operation. The data recovery module adopts the half-wave shaping method to distinguish the amplified sine wave signal from the near-DC signal, and restores the original data through the hysteresis comparator.

Specifically, a square wave signal generated by the crystal oscillator is input to a phase-locked loop, and frequency multiplied to obtain a baseband signal; the output of the phase-locked loop is connected to a front-end amplifier fused with a mixer, and the front-end amplifier fused with the mixer connects the human body and the The FSK frequency modulation signal received by the electrode is subjected to a frequency mixing operation; the output of the front-end amplifier fused with the mixer is connected to a low-pass filter to filter out high-frequency noise interference signals and harmonics; the low-pass filter The output of the IF is connected to the IF amplifier to amplify the IF signal again, which is convenient for subsequent operations. The output of the intermediate frequency amplifier is connected to a data recovery module to recover data and clock signals.

Example:

As shown in Figure 2, the transmitter circuit in the transmit mode includes: a crystal oscillator, a phase-locked loop, a two-frequency divider, a three-frequency divider, a data selector MUX, and a human body driver.

The 2MHz square wave signal generated by the crystal oscillator is input to the phase-locked loop, and the 48MHz square wave signal is obtained by multiplying the frequency by 24 times in the transmitting mode.

The outputs of the phase-locked loop are respectively connected to the input ends of the two-frequency divider and the three-frequency divider, and 16MHz and 24MHz square waves are obtained after the two-frequency and three-frequency division.

The outputs of the two-frequency divider and the three-frequency divider are respectively connected to the input end of the data selector MUX, and a certain channel of signal is controlled by the data signal to pass through, and the FSK frequency modulation signal of 24MHz and 16MHz is output.

The data selector MUX selects the 24MHz and 16MHz square wave signals from the external input data signal to form the FSK frequency modulation signal, that is, when the data signal is 1, the 24MHz square wave signal is selected, and when the data signal is 0, the 16MHz square wave is selected. Signal.

The output of the data selector MUX is connected to the input of the human body driver to drive the electrodes and the larger capacitance of the human body.

The output of the human body driver is connected to the medical electrodes to transmit signals into the human body.

As shown in Figure 3, the receiver circuit in the receiving mode includes: a crystal oscillator, a phase-locked loop, a front-end amplifier integrated with a mixer, a low-pass filter, an intermediate frequency amplifier, and a data recovery module.

The 2MHz square wave signal generated by the crystal oscillator is input into the phase-locked loop, and the 26MHz square wave signal is obtained by multiplying the frequency by 13 times as the baseband signal.

The output of the phase-locked loop is connected to the front-end amplifier fused with the mixer, and the FSK signal received by the human body and the electrode is mixed. The signal received by the electrode is amplified nonlinearly, and the received FSK FM signal is down-converted with the 26MHz square wave signal generated by the frequency generator in the receiving mode to obtain 2MHz and 10MHz square wave signals.

The output of the front-end amplifier fused with the mixer is connected to a low-pass filter to filter out high-frequency interference signals and noise, specifically: the cut-off frequency of the low-pass filter is set to 3MHz, which can The signal is low-pass filtered to filter out high-frequency noise and harmonics to obtain a 2MHz sine wave and a signal close to DC.

The output of the low-pass filter is connected to the intermediate frequency amplifier to amplify the intermediate frequency signal again, that is, the intermediate frequency amplifier can amplify the low-pass filtered signal again, which is convenient for subsequent operations.

The output of the intermediate frequency amplifier is connected to a data recovery module to recover data and clock signals, specifically, the data recovery module adopts a half-wave shaping method to distinguish a 2MHz sine wave from a signal close to DC, and compare the hysteresis restore the original data.

A human body channel communication method, the transmitter doubles the frequency in the transmission mode to obtain a 48MHz square wave by two and three, and then the data signal controls the data selector MUX to select one of two to modulate to obtain an FSK frequency modulation signal, and after driving. It is introduced into the human body through the electrodes; the receiver uses the 26MHz square wave signal obtained by frequency multiplication in the receiving mode as the baseband signal, and amplifies, down-converts, and low-pass filters the 16MHz and 24MHz FSK FM signals received through the human body and the electrodes. , After the IF amplification and data recovery operations, the original data is recovered.

The above descriptions are only preferred implementation examples of the present invention, and do not limit the present invention in any form. Although the implementation process of the present invention has been described in detail above, those skilled in the art can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features. All modifications, equivalent replacements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (5)

1. a circuit based on human body channel communication, comprises frequency generator, transmitter, receiver, it is characterized in that, described frequency generator adopts the structure of phase-locked loop, comprises transmission pattern and receiving pattern, under transmission pattern, will be The square wave generated by the crystal oscillator is input to the phase-locked loop frequency multiplication to obtain a clock signal and then input to the transmitter, and in the receiving mode, the square wave generated by the crystal oscillator is frequency multiplied as a demodulated local oscillator signal and input to the receiver; the transmitter includes a splitter. Frequency converter, data selector MUX, human body driver, the clock signal obtained by multiplying the frequency is divided by the frequency divider, and then the FSK frequency modulation signal is generated by the data selector MUX, and then the signal is transmitted to the human body through the human body driver to drive the electrodes; The receiver amplifies and down-converts the signal received by the electrode and transmitted from the human body to a low-IF frequency, and performs intermediate-frequency amplification after filtering out high-frequency interference, and finally restores the data. 2. a kind of circuit based on human body channel communication as claimed in claim 1, is characterized in that, described frequency divider comprises N frequency divider and M frequency divider, the square wave signal that crystal oscillator produces passes through working in transmission mode The clock of the transmitter is obtained by frequency multiplication of the phase-locked loop, and the clock is divided by N frequency divider N and M frequency divider M to obtain two square waves of different frequencies. 3. a kind of circuit based on human body channel communication as claimed in claim 1, is characterized in that, described receiver comprises: front-end amplifier, low-pass filter, intermediate frequency amplifier, data recovery module merged with mixer, and The front-end amplifier fused by the mixer performs nonlinear amplification on the signals received from the human body and the electrodes, and down-converts the received FSK frequency modulation signal with the square wave signal generated by the frequency generator in the receive mode, and obtains the result after the down-conversion. low-IF signal; the output of the front-end amplifier fused with the mixer is connected to a low-pass filter, and the low-pass filter can perform low-pass filtering on the down-converted low-IF signal, and filter high-frequency noise and harmonics. The output of the low-pass filter is connected to the intermediate frequency amplifier, and the intermediate frequency amplifier can amplify the low-pass filtered signal again, that is, amplify the sine wave signal and the signal close to the direct current; The output of the intermediate frequency amplifier is connected to a data recovery module, and the data recovery module adopts a half-wave shaping method to distinguish the amplified sine wave signal from the DC signal, and recover the original data through a hysteresis comparator. 4. a kind of circuit based on human body channel communication as claimed in claim 3 is characterized in that, described frequency generator comprises: mode switch, crystal oscillator, frequency discriminator and phase discriminator, charge pump, loop filter, voltage A controlled oscillator and a frequency divider group, the frequency divider group includes a first frequency divider and a second frequency divider, the mode switch switches the working mode of the frequency generator, and the phase-locked loop outputs an X MHz square wave in the transmit mode , the phase-locked loop in the receiving mode outputs a Y MHz square wave; the crystal oscillator generates a reference signal source with a frequency of ZMHz, as the reference frequency of the phase-locked loop; The output frequency signal and the reference frequency signal are processed by frequency and phase discrimination, and the frequency and phase difference between the output frequency signal and the reference frequency signal are extracted; The low-pass filter of the loop can filter out the noise and interference components of the error voltage output by the charge pump to form the control voltage of the voltage-controlled oscillator; the voltage-controlled oscillator is adjusted according to the control voltage Output frequency, the frequency divider group divides the output frequency and then connects to the frequency and phase detector, compares it with the reference signal source, extracts the phase and frequency information, and forms negative feedback, so that the phase-locked loop is gradually locked at the desired X MHz and Y MHz output frequency. 5. a kind of communication method that adopts the circuit based on human body channel communication as claimed in claim 1-4, it is characterized in that, be specifically: the square wave N frequency division and M frequency division that the transmitter obtains by frequency multiplication under the transmission mode Then, it is modulated by the data selector MUX to obtain the FSK frequency modulation signal. After driving, it is transmitted to the human body through the electrodes. After the received FSK FM signal is amplified, down-converted, low-pass filtered, IF amplified, and recovered, the original data is recovered.

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