KR102449611B1 - Human body communication receiver and operating method thereof - Google Patents

Abstract

The present invention relates to a human body communication receiver, and more particularly, to a human body communication receiver capable of effectively removing low-frequency noise and an operating method thereof. A human body communication receiver according to an embodiment of the present invention includes a receiving electrode; virtual electrode; a filter circuit connected between the receiving electrode and the virtual electrode, the filter circuit generating a high-frequency signal by removing low-frequency noise of a signal received through the receiving electrode; a low frequency reconstruction circuit connected to the rear end of the filter circuit and configured to rectify the high frequency signal and reconstruct the low frequency baseband signal; and an amplifier circuit connected to the rear end of the low-frequency reconstruction circuit and amplifying the low-frequency baseband signal.

Description

HUMAN BODY COMMUNICATION RECEIVER AND OPERATING METHOD THEREOF

The present invention relates to a human body communication receiver, and more particularly, to a human body communication receiver capable of effectively removing low-frequency noise and an operating method thereof.

Human body communication is a communication method that transmits signals and information from a transmitter to a receiver using the human body as a medium. It is a communication method having a simple structure and low power consumption because it can transmit and receive digital signals directly to the human body without the need for modulation and demodulation.

A bandpass filter is provided to filter unnecessary signal bands other than the band of the signal transmitted from the transmitter among the signals flowing into the human body communication receiver. Implementing an optimal filter structure to effectively complete the bandpass is essential for signal integrity. very important.

It is an object of the present invention to provide a human body communication receiver including a low-frequency reconstruction circuit for reconstructing a high-frequency signal obtained by removing low-frequency noise from a received signal into an original low-frequency baseband signal, and an operating method thereof.

A human body communication receiver according to an embodiment of the present invention includes a receiving electrode; virtual electrode; a filter circuit connected between the receiving electrode and the virtual electrode, the filter circuit generating a high-frequency signal by removing low-frequency noise of a signal received through the receiving electrode; a low frequency reconstruction circuit connected to the rear end of the filter circuit and configured to rectify the high frequency signal and reconstruct the low frequency baseband signal; and an amplifier circuit connected to the rear end of the low-frequency reconstruction circuit and amplifying the low-frequency baseband signal.

A method of operating a human body communication receiver according to an embodiment of the present invention includes: removing, by a filter circuit connected between a receiving electrode and a virtual electrode, low-frequency noise from a signal received through the receiving electrode; rectifying, by a low frequency reconstruction circuit connected to the rear end of the filter circuit, the high frequency signal and reconstructing it into a low frequency baseband signal; and an amplifying circuit connected to the rear end of the low-frequency reconstruction circuit amplifying the low-frequency baseband signal.

According to an embodiment of the present invention, unnecessary noise may be removed from information included in a received signal of human body communication.

Furthermore, according to an embodiment of the present invention, the low-frequency noise can be effectively avoided by reconstructing the high-frequency signal from which the noise signal has been removed into the original low-frequency baseband signal.

1 is a circuit diagram illustrating an exemplary configuration of a human body communication receiver according to an embodiment of the present invention.
2A shows a waveform of a typical low-frequency baseband signal.
2B shows a waveform of a transmission signal according to an embodiment of the present invention.
FIG. 3 shows a waveform of a first reception signal input to the reception electrode of FIG. 1 and a waveform of a second reception signal input to the virtual electrode of FIG. 1 .
4A shows the waveform of the positive input signal of FIG. 1 and the waveform of the signal at the first node.
Figure 4b shows the waveforms of the signals at the second node and the third node of Figure 1;
Fig. 4c shows the waveform of the signal at the fourth node of Fig. 1;
5 is an exemplary flowchart illustrating a method of operating a human body communication receiver according to an embodiment of the present invention.
6 shows an apparatus for human body communication according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described clearly and in detail to the extent that those skilled in the art can easily practice the present invention.

Components described with reference to terms such as units or units, modules, blocks, and groups (~or, ~er) used in the detailed description and functional blocks shown in the drawings are It may be implemented in the form of software, hardware, or a combination thereof. Illustratively, the software may be machine code, firmware, embedded code, and application software. For example, hardware may include an electrical circuit, an electronic circuit, a processor, a computer, an integrated circuit, integrated circuit cores, a pressure sensor, an inertial sensor, a microelectromechanical system (MEMS), a passive element, or a combination thereof. .

1 is a circuit diagram showing an exemplary configuration of a human body communication receiver 100 according to an embodiment of the present invention. When receiving a signal (hereinafter referred to as a transmission signal) transmitted from a human body communication transmitter (not shown) using the human body as a medium, the human body communication receiver 100 can remove low-frequency noise included in the received signal. In addition, a signal from which low-frequency noise has been removed can be reconstructed into a low-frequency baseband signal and then amplified. The human body communication receiver 100 may include a receiving electrode 110 , a virtual electrode 120 , a filter circuit 130 , a low frequency reconstruction circuit 140 , and an amplifier circuit 150 .

The reception electrode 110 may receive the first reception signal IN_1 as an input. The first reception signal IN_1 may include a transmission signal and low-frequency noise introduced from a noise source (eg, a fluorescent lamp) around the human body. For example, the transmission signal may include a high-frequency pulse. For example, the receiving electrode 110 may be directly attached to the epidermis of the human body. For example, the receiving electrode 110 may be connected to a positive input of the differential amplifier 151 .

The virtual electrode 120 may receive the second reception signal IN_2 for differential amplification of the low frequency baseband signal by the amplification circuit 150 . The second reception signal IN_2 may include low-frequency noise introduced from a noise source, but unlike the first reception signal IN_1 , it may not include a transmission signal. For example, the virtual electrode 120 may be located opposite to the position where the receiving electrode is attached, and may protrude outside the human body communication receiver 100 or located inside the human body communication receiver 100 . . For example, the virtual electrode 120 may not contact the epidermis of the human body. For example, the virtual electrode 120 may be connected to a negative input of the differential amplifier 151 .

The filter circuit 130 may remove low-frequency noise included in the first reception signal IN_1 . The filter circuit 130 may be connected between the receiving electrode 110 and the virtual electrode 120 , and the amplifying circuit 150 . The filter circuit 130 may include at least one inductor 131 , but the present invention is not limited thereto.

The impedance of the inductor 131 may be lowered in a low frequency band. Accordingly, the inductor 131 may cause the reception electrode 110 and the virtual electrode 120 to be short-circuited with respect to the low-frequency noise included in the first reception signal IN_1 input to the reception electrode 110 , and reduce the low-frequency noise. can be removed The filter circuit 130 may output a high-frequency signal from which low-frequency noise is removed by the inductor 131 to the low-frequency reconstruction circuit 140 .

As described above, the second reception signal IN_2 input to the virtual electrode 120 may not include a transmission signal, and in this case, may not include a signal of a high frequency band. Accordingly, when the signal of the low frequency band is removed from the second reception signal IN_2 by the inductor 131 , the magnitude of the signal may be close to zero. The filter circuit 130 may output the negative input signal IN_N whose magnitude is close to zero.

The low-frequency reconstruction circuit 140 may reconstruct a high-frequency signal from which low-frequency noise is removed into a low-frequency baseband signal. The low frequency reconstruction circuit 140 may be connected between the receiving electrode 110 and the virtual electrode 120 , and the amplification circuit 150 , and may be connected to a rear end of the filter circuit 130 . The low frequency reconstruction circuit 140 includes a capacitor 141 connected in series with the receiving electrode 110 , a diode 142 connected in series with the capacitor 141 , and a capacitor connected in parallel between the diode 142 and the virtual electrode 120 . 143 and a load resistor 144, but the present invention is not limited thereto. For example, the low frequency reconstruction circuit 140 may include resistors connected between the power supply voltage VDD and the ground GND at the rear end of the capacitor 141 , but the present invention is not limited thereto.

The low-frequency reconstruction circuit 140 may receive a signal from which the low-frequency noise output from the filter circuit 130 is removed. A signal from which low frequency noise is removed may pass through the capacitor 141 , and the positive input signal IN_P passing through the capacitor 141 may be input to the anode of the diode 142 . Resistors connected between the power voltage VDD and the ground GND may apply a bias voltage to the anode of the diode 142 so that the positive input signal IN_P may exceed a threshold voltage of the diode 142 .

The diode 142 may output a rectified signal obtained by rectifying the positive input signal IN_P as a cathode. The capacitor 143 may store a rectified signal, and the rectified signal stored in the capacitor 143 may be discharged by the load resistor 144 . Accordingly, the capacitor 143 and the load resistor 144 can adjust the time for which the rectified signal output to the cathode of the diode 142 is maintained, and reconstruct the rectified signal into a low-frequency baseband signal. The signal output to the first node ND_1 may be a reconstructed low-frequency baseband signal.

The amplification circuit 150 may amplify and output the reconstructed low-frequency baseband signal. The amplification circuit 150 may include at least one differential amplifier 151 . For example, at least one capacitor may be connected in series to each of the positive input terminal and the negative input terminal of the differential amplifier 151 , but the present invention is not limited thereto. For example, resistors connected between the power supply voltage VDD and the ground GND may be connected in parallel between the rear end of each capacitor of the amplifier circuit 150 and each input terminal, but the present invention is not limited thereto.

The reconstructed low-frequency baseband signal output to the first node ND_1 may be output to the second node ND_2 through a capacitor connected to the positive input terminal of the differential amplifier 151 . The positive input terminal of the differential amplifier 151 may receive a signal output to the second node ND_2 .

The negative input signal IN_N through which the second reception signal IN_2 input to the virtual electrode 120 has passed through the inductor 131 may be directly transmitted to the third node ND_3 . Accordingly, a bias voltage applied by resistors between the voltage VDD connected to the negative input terminal and the ground GND may appear at the third node ND_3 . The negative input terminal of the differential amplifier 151 may receive a signal output to the third node ND_3 . The signal output to the third node ND_3 may be a voltage that is a reference for differential amplification.

The differential amplifier 151 may differentially amplify the signal of the second node ND_2 input to the positive input terminal and the signal of the third node ND_3 input to the negative input terminal, and amplify the amplified signal to the fourth node ( ND_4) can be output.

2A shows a waveform of a typical low-frequency baseband signal. The section T1 represents a section in which the signal value corresponds to a digital high, and the section T2 represents a section in which the signal value corresponds to a digital low. For example, each of the sections T1 and T2 may have a length of 10 μs.

As a transmission signal for human body communication, the low-frequency baseband digital signal shown in FIG. 2A may be used as it is. However, when the frequency band of the transmission signal and the frequency band of the noise are similar, the transmission signal and the noise may overlap, the original transmission signal may be removed in the process of removing the noise, and the transmission signal may not be recoverable. have.

2B shows a waveform of a transmission signal according to an embodiment of the present invention. In the case of section T1, a human body signal transmitter (not shown) may map a high-frequency pulse corresponding to the low-frequency baseband signal shown in FIG. 2A . For example, when the length of the section T1 is 10 μs, a high-frequency pulse having a frequency fCLK of 10 MHz may be mapped to the signal of the section T1. In this case, the width (1/fCLK) of the mapped pulse may be 100 ns. In the case of the period T2, the value of the signal may be maintained as a digital low for the same length of time as the period T1 as in FIG. 2A .

When a signal obtained by mapping a high-frequency pulse to a low-frequency baseband signal as shown in FIG. 2B is used as a transmission signal for human body communication, the transmission signal and low-frequency noise may not overlap, and the filter circuit 130 of FIG. Even in the process of removing, the original transmission signal may not be removed.

FIG. 3 illustrates a waveform of a first reception signal IN_1 input to the reception electrode 110 of FIG. 1 and a waveform of a second reception signal IN_2 input to the virtual electrode 120 of FIG. 1 . The first reception signal IN_1 and the second reception signal IN_2 may include noise introduced from a noise source around the human body. For example, the noise source around the human body may be a fluorescent lamp, and the frequency of the noise may be 60 kHz.

The first reception signal IN_1 may be a signal in which a transmission signal and noise introduced from a noise source around the human body are superimposed. For example, as described with reference to FIG. 2B , the transmission signal may be a signal including a high frequency pulse, and the frequency of the high frequency pulse may be 10 MHz.

The second reception signal IN_2 may be a signal in which an arbitrary reference voltage and noise introduced from a noise source around the human body are superimposed. Unlike the first reception signal IN_1 , the second reception signal IN_2 may not include a transmission signal, and thus may be a low frequency signal that does not include a high frequency pulse.

FIG. 4A shows the waveform of the positive input signal IN_P and the waveform of the signal at the first node ND_1 of FIG. 1 . FIG. 4B shows waveforms of signals at the second node ND_2 and the third node ND_3 of FIG. 1 . FIG. 4C shows a waveform of a signal at the fourth node ND_4 of FIG. 1 . Hereinafter, it will be described with reference to FIG. 1 together with FIGS. 4A to 4C.

Referring to FIG. 4A , the positive input signal IN_P is a signal passing through the capacitor 141 after the low frequency noise included in the first reception signal IN_1 is removed by the inductor 131 , and the positive input signal IN_P ) may have a form in which only a high-frequency band signal remains in the waveform of the first reception signal IN_1 shown in FIG. 3 .

The signal of the first node ND_1 is a reconstructed low-frequency baseband signal including a rectified signal in which the positive input signal IN_P is rectified by the diode 142 , and the waveform of the signal at the first node ND_1 is a rectified signal may be in the form of being maintained and then discharged. The time for which the rectified signal included in the signal of the first node ND_1 is maintained may be adjusted by the values of the capacitor 143 and the load resistor 144 .

Referring to FIG. 4B , the signal of the second node ND_2 may be a signal of the signal of the first node ND_1 passing through a capacitor connected to the front end of the positive input of the differential amplifier 151 . The signal of the third node ND_3 may be a signal through which the negative input signal IN_N has passed through a capacitor connected to the front end of the negative input of the differential amplifier 151 .

Since the negative input signal IN_N is a signal whose magnitude is close to 0 by the inductor 131 of the second reception signal IN_2 , the signal of the third node ND_3 is transmitted to the front end of the negative input of the differential amplifier 151 . It may appear as a bias voltage applied by resistors connected between the power supply voltage VDD and the ground GND connected in parallel. That is, as shown in FIG. 4B , the waveforms of the signals at the second node ND_2 and the third node ND_3 may appear based on the bias voltage. A signal of the second node ND_2 may be input as a positive input of the differential amplifier 151 , and a signal of the third node ND_3 may be input as a negative input of the differential amplifier 151 . The signal of the second node ND_2 may be amplified based on the magnitude of the signal of the third node ND_3 .

Referring to FIG. 4C , the signal of the fourth node ND_4 may be a signal output by differentially amplifying the signal of the second node ND_2 and the signal of the third node ND_3 input to the differential amplifier. The waveform of the final signal at the fourth node ND_4 may appear as the waveform of the low-frequency baseband signal before the high-frequency pulse is mapped, as shown in FIG. 2A .

5 is an exemplary flowchart illustrating a method of operating the human body communication receiver 100 according to an embodiment of the present invention. Hereinafter, it will be described with reference to FIG. 1 together with FIG. 5 .

In operation S110 , the filter circuit 130 may remove low-frequency noise included in the first reception signal IN_1 . In operation S120, the low-frequency reconstruction circuit 140 may reconstruct the high-frequency signal from which the low-frequency noise is removed into a low-frequency baseband signal. In step S130 , the amplification circuit 150 may amplify the low-frequency baseband signal reconstructed in the low-frequency reconstruction circuit 140 .

6 conceptually illustrates an apparatus 1000 for human body communication according to an embodiment of the present invention. The apparatus 1000 for human body communication may include a human body communication transmitter 1100 and a human body communication receiver 1200 .

The human body communication transmitter 1100 may include a transmission digital modem 1110 , a transmission electrode driving circuit 1120 , and a transmission electrode 1130 . The human body communication transmitter 1100 may transmit the transmission signal Tx to the human body based on the electric field formed between the ground of the human body communication transmitter 1100 and the ground ground and the electric field formed between the human body and the transmission electrode 1130 .

For example, when a voltage varying with time is applied to the transmission electrode 1130 , an electric field that varies with time may be formed between the human body and the transmission electrode 1130 , and electric charges that change with time may be generated in the human body as well. have. Accordingly, the human body communication transmitter 1100 may transmit the transmission signal Tx to the human body. For example, the strength of each of the above-described electric fields may vary based on the capacitance C1 between the ground of the human body communication transmitter 1100 and the ground ground and the capacitance C2 between the human body and the transmission electrode 1130 .

The transmission digital modem 1110 may generate transmission data based on a clock signal generated by a clock generator (not shown). The transmission electrode driving circuit 1120 may receive transmission data generated by the transmission digital modem 1110 and output it to the transmission electrode 1130 . The transmission electrode 1130 may transmit the transmission signal Tx to the human body. For example, the transmission electrode 1130 may be directly attached to the epidermis of the human body. For example, the transmission signal Tx may be the same as the transmission signal shown in FIG. 2B .

The human body communication receiver 1200 may include a reception electrode 1210 , a virtual electrode 1220 , an analog circuit unit 1230 , a clock data recovery circuit 1240 , and a reception digital modem 1250 . The human body communication receiver 1200 may receive the reception signal Rx based on the electric field formed between the ground of the human body communication receiver 1200 and the ground and the electric field formed between the human body and the receiving electrode 1210 .

For example, a time-varying electric charge generated in the human body may form an electric field varying with time between the human body and the receiving electrode 1210 . Accordingly, a voltage varying with time may be applied to the reception electrode 1210 , and the reception signal Rx may be transmitted from the human body to the human body communication receiver 1200 . For example, the strength of each of the above-described electric fields may vary based on the capacitance C3 between the human body and the receiving electrode 1210 and the capacitance C4 between the ground of the human body communication receiver 1200 and the earth ground.

The reception electrode 1210 may receive the reception signal Rx. For example, the receiving electrode 1210 may be directly attached to the epidermis of the human body. For example, the received signal Rx may include noise introduced from a noise source around the human body. The virtual electrode 1220 may provide a voltage required to amplify the received signal Rx. For example, the virtual electrode 1220 may not contact the epidermis of the human body.

The analog circuit unit 1230 may remove noise from the received signal Rx, amplify it to an appropriate size, and output it. For example, the analog circuit unit 1230 may include the filter circuit 130 , the low frequency reconstruction circuit 140 , and the amplifier circuit 150 of FIG. 1 . The clock data recovery circuit 1240 may generate a reconstructed signal by extracting a clock from the signal output from the analog circuit unit 1230 . The reception digital modem 1250 may receive the reconstructed signal and recover the transmission data generated by the transmission digital modem 1110 .

The above are specific embodiments for carrying out the present invention. The present invention will include not only the above-described embodiments, but also simple design changes or easily changeable embodiments. In addition, the present invention will include techniques that can be easily modified and implemented using the embodiments. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be defined by the claims described below as well as the claims and equivalents of the present invention.

100: human body communication receiver 110: receiving electrode
120: virtual electrode 130: filter circuit
140: low frequency reconstruction circuit 150: amplification circuit

Claims (14)

receiving electrode;
virtual electrode;
a filter circuit connected between the receiving electrode and the virtual electrode, the filter circuit generating a high-frequency signal by removing low-frequency noise of a signal received through the receiving electrode;
a low frequency reconstruction circuit connected to the rear end of the filter circuit and configured to rectify the high frequency signal and reconstruct the low frequency baseband signal; and
and an amplifier circuit connected to a rear end of the low frequency reconstruction circuit and amplifying the low frequency baseband signal. The method of claim 1,
wherein the filter circuit includes at least one inductor. The method of claim 1,
The low-frequency reconstruction circuit comprises:
diode;
a first capacitor connected between the anode of the diode and the receiving electrode;
a second capacitor connected between the cathode of the diode and the virtual electrode;
a load resistor connected between the cathode of the diode and the virtual electrode; and
and a first plurality of resistors coupled between the first capacitor and an anode of the diode. 4. The method of claim 3,
The first plurality of resistors are connected between a power supply voltage and a ground, and provide a first bias voltage to the anode of the diode. The method of claim 1,
The amplification circuit is:
differential amplifier;
a third capacitor connected between the rear end of the low frequency reconstruction circuit and a first input terminal of the differential amplifier;
a fourth capacitor connected between the rear end of the low frequency reconstruction circuit and a second input terminal of the differential amplifier;
a second plurality of resistors coupled to the first input terminal; and
and a third plurality of resistors connected to the second input terminal. 6. The method of claim 5,
The plurality of second resistors and the plurality of third resistors are connected between a power supply voltage and a ground,
the second plurality of resistors provide a second bias voltage to the first input terminal of the differential amplifier; and
wherein the third plurality of resistors provide a third bias voltage to the second input terminal of the differential amplifier. 6. The method of claim 5,
The first input terminal of the differential amplifier receives a first signal passing through the third capacitor connected to the first input terminal,
The second input terminal of the differential amplifier receives a second signal passing through the fourth capacitor connected to the second input terminal,
wherein the differential amplifier differentially amplifies the first signal and the second signal. A method of operating a human body communication receiver, comprising:
generating, by a filter circuit connected between the receiving electrode and the virtual electrode, low-frequency noise from the signal received through the receiving electrode to generate a high-frequency signal;
rectifying, by a low frequency reconstruction circuit connected to the rear end of the filter circuit, the high frequency signal and reconstructing it into a low frequency baseband signal; and
and an amplifying circuit connected to a rear end of the low-frequency reconstruction circuit amplifying the low-frequency baseband signal. 9. The method of claim 8,
The low-frequency reconstruction circuit comprises:
diode;
a first capacitor connected between the anode of the diode and the receiving electrode;
a second capacitor connected between the cathode of the diode and the virtual electrode;
a load resistor connected between the cathode of the diode and the virtual electrode; and
and a first plurality of resistors coupled between the first capacitor and the anode of the diode. 10. The method of claim 9,
The step of reconstructing the low-frequency baseband signal includes:
generating a rectified signal by rectifying the high frequency signal by the diode;
storing the rectified signal in the second capacitor; and
and discharging the stored rectified signal by the load resistor. 11. The method of claim 10,
The first plurality of resistors are connected between the power supply voltage and the ground,
The step of reconstructing the low-frequency baseband signal includes:
and prior to generating the rectified signal, providing a first bias voltage to the anode of the diode by the first plurality of resistors. 9. The method of claim 8,
The amplification circuit is:
differential amplifier;
a third capacitor connected between the rear end of the low frequency reconstruction circuit and a first input terminal of the differential amplifier;
a fourth capacitor connected between the rear end of the low frequency reconstruction circuit and a second input terminal of the differential amplifier;
a second plurality of resistors coupled to the first input terminal; and
and a third plurality of resistors coupled to the second input terminal. 13. The method of claim 12,
The plurality of second resistors and the plurality of third resistors are connected between a power supply voltage and a ground,
The step of amplifying the low frequency baseband signal comprises:
providing, by the second plurality of resistors, a second bias voltage to the first input terminal of the differential amplifier;
and the third plurality of resistors providing a third bias voltage to the second input terminal of the differential amplifier. 13. The method of claim 12,
The step of amplifying the low frequency baseband signal comprises:
receiving, by the first input terminal of the differential amplifier, a first signal passing through the third capacitor connected to the first input terminal;
receiving, by the second input terminal of the differential amplifier, a second signal passing through the fourth capacitor connected to the second input terminal; and
and differentially amplifying, by the differential amplifier, the first signal and the second signal.

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