Underground direct current carrier communication system and communication method based on TTL serial port modulation

Abstract

The invention discloses an underground direct current carrier communication system and communication method based on TTL serial port modulation, the system comprises a ground part and an underground part, and the ground part and the underground part are connected through a cable; the ground part comprises a TTL universal serial port I, a high-speed change-over switch module, a direct-current stabilized power supply I and a direct-current stabilized power supply II; the underground part comprises a decoding circuit and a TTL universal serial port II; the high-speed change-over switch module is used for switching the direct-current voltage-stabilized power supply I and the direct-current voltage-stabilized power supply II according to the level of the TTL serial port signal, modulating a steady-state TTL carrier signal and transmitting the steady-state TTL carrier signal to the decoding circuit through a cable; the decoding circuit comprises a high-pass filter, an amplifier, a voltage follower and a hysteresis comparator. According to the system and the method disclosed by the invention, the stability and the reliability of a communication system are improved, the system design is simplified, the requirements of external modules and circuits are reduced, and the design complexity and the cost are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of communication systems, and in particular to an underground direct current carrier communication system and a communication method based on TTL serial port modulation. Background Art

[0002] Oil well communication is an indispensable part of the oil industry and is of great significance to ensure the safety and efficient production of oil wells. With the continuous development of the oil industry, the research on downhole and surface communication technology has become an increasingly important content in the fields of oil production, logging, drilling, etc. Oil well communication is not only related to the real-time collection and monitoring of production data, but also directly affects the production efficiency and safety of oil wells.

[0003] The wired communication method in the existing oil well communication system, especially the communication using a single-core cable, has become the most commonly used method in the current oil well communication system due to its long transmission distance, shared power supply communication line, and few interface connection points. The existing oil well communication system selects pulse period modulation as the signal modulation method. The modulated signal is transmitted to the receiving end through a single-core steel pipe cable. The receiving end demodulates the transmitted signal to restore the original digital signal, thereby realizing DC carrier communication. However, the existing single-core cable carrier communication system modulates the carrier signal method mostly by using a transient high-frequency signal to modulate a high-frequency carrier signal by superimposing it on a DC regulated power supply through coupling technology. This method has some technical disadvantages:

[0004] 1. Load causes transient carrier signal attenuation: The electrical characteristics of the cable will cause high-frequency transient signals to attenuate during long-distance transmission. Especially when the cable length increases, the amplitude of the signal will gradually decay, resulting in demodulation difficulties or data loss.

[0005] 2. Voltage fluctuation of transient signals: The main function of a DC regulated power supply is to provide a stable voltage output. However, superimposed transient signals may cause fluctuations in the power supply output voltage, affecting the stability of the power supply.

[0006] 3. The demodulation process is complex and not universal: The existing technology generally uses hardware circuit filtering and shaping and then connects to the external interrupt port of the microcontroller. The signal characteristics of different modulation carrier technologies are generally different, and specific decoding programs need to be written according to the signal characteristics. Once the hardware design is completed, changes to the decoding logic or protocol require reprogramming and debugging, which increases maintenance costs. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides an underground DC carrier communication system and communication method based on TTL serial port modulation, which not only solves the problem of large signal attenuation of high-frequency transient carrier signals due to load changes in the existing single-core cable carrier communication downlink technology, but also solves the problem of poor signal stability caused by the fluctuation of superimposed transient signals on the DC regulated power supply. It is then demodulated into a TTL serial port universal signal through a decoding circuit, which is convenient for the single-chip microcomputer to directly configure the UART port to receive the signal.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] A downhole DC carrier communication system based on TTL serial port modulation, comprising a surface part and a downhole part, wherein the surface part and the downhole part are connected by a cable;

[0010] The surface part includes a TTL universal serial port 1, a high-speed switching switch module, a DC regulated power supply 1 and a DC regulated power supply 2; the underground part includes a decoding circuit and a TTL universal serial port 2;

[0011] The high-speed switching switch module is connected to the TTL universal serial port 1, and the TTL universal serial port 1 is used to send a TTL serial port signal as a control signal of the high-speed switching switch module. The high-speed switching switch module is used to switch the DC regulated power supply 1 and the DC regulated power supply 2 according to the level of the TTL serial port signal, and modulate a steady-state TTL carrier signal to input the cable, and transmit it to the decoding circuit through the cable;

[0012] The decoding circuit includes a high-pass filter, an amplifier, a voltage follower and a hysteresis comparator. The high-pass filter is used to filter out the DC signal and convert it into a high-level enhanced TTL signal; the amplifier is used to amplify the signal three times to shorten the rising and falling edge time; the voltage follower is used to increase the input impedance and provide isolation to prevent the previous stage circuit from being affected by the subsequent load; the hysteresis comparator is used to shape the signal so that its output amplitude meets the standard TTL signal requirements and effectively filters out high-frequency interference.

[0013] In the above scheme, the TTL universal serial port 1 sends a TTL serial port signal with a baud rate of 600 as the control signal of the high-speed switch switching module. The voltages of the DC regulated power supply 1 and the DC regulated power supply 2 are 60V and 70V respectively. The high-speed switch switching module switches according to the high and low levels of the control signal. When the control signal is a low level of 0V, a steady-state voltage of 60V is output; when the control signal is a high level of 5V, a steady-state voltage of 70V is output.

[0014] In the above scheme, the high-pass filter includes a capacitor C1, a resistor R1, a diode D1 and a resistor R2; a steady-state TTL carrier signal is input from a cable and connected to one end of the capacitor C1, the other end of the capacitor C1 is connected to the positive electrode of the diode D1, and the negative electrode of the diode D1 is grounded, the resistor R1 is connected in parallel with the diode D1, and is connected to the ground to form a high-pass filter, and the input signal is limited and the subsequent circuit is protected; one end of the resistor R2 is connected to the output end of C1, and the other end is connected to the next stage.

[0015] In the above scheme, the amplifier includes an operational amplifier U1.1, a capacitor C2, a capacitor C3, a resistor R3 and a resistor R4; pin 3 of the operational amplifier U1.1 receives a signal from a high-pass filter from resistor R2; capacitor C2 and resistor R4 are connected in parallel and both ends are connected to pin 1 and pin 2 of the operational amplifier U1.1; one end of resistor R3 is connected to pin 2 of the operational amplifier U1.1, and the other end is grounded; pin 8 of the operational amplifier U1.1 is connected to a 5V power supply voltage and one end of capacitor C3, and the other end of capacitor C3 is grounded; output pin 1 of the operational amplifier U1.1 is connected to the next level.

[0016] In the above scheme, the voltage follower includes an operational amplifier U1.2 and a resistor R5, the output pin 1 of the operational amplifier U1.1 is connected to the non-inverting input pin 5 of the operational amplifier U1.2, the inverting input pin 6 of the operational amplifier U1.2 is directly connected to its output pin 7, one end of the resistor R5 is connected to pin 7 of the operational amplifier U1.2, and the other end is connected to the next stage.

[0017] In the above scheme, the hysteresis comparator includes tantalum capacitor C4, capacitor C5, capacitor C6, resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, resistor R10 and operational amplifier U2.1; the inverting input pin 2 of the operational amplifier U2.1 receives a signal from the output of the voltage follower; the 5V power supply is grounded after passing through resistors R7 and R6, and the negative electrode of the tantalum capacitor C4 is grounded and connected in parallel with the resistor R6 to form a trigger hysteresis network; one end of the resistor R8 is connected to the positive electrode of the tantalum capacitor C4, and the other end is connected to pin 3 of the operational amplifier U2.1; the resistor R9 is connected in parallel to pins 1 and 3 of the operational amplifier U2.1; the capacitor C5 is connected in parallel to both ends of the resistor R9; one end of the capacitor C6 is grounded, and the other end is connected to pin 8 of the operational amplifier U2.1, and the output pin 1 outputs a TTL universal serial port 2 compatible signal through the resistor R10.

[0018] An underground DC carrier communication method based on TTL serial port modulation, using an underground DC carrier communication system based on TTL serial port modulation as described above, includes the following process:

[0019] (1) The TTL universal serial port 1 sends a TTL serial port signal as a control signal of the high-speed switching switch module. The high-speed switching switch module switches the DC regulated power supply 1 and the DC regulated power supply 2 according to the level of the TTL serial port signal, modulates a steady-state TTL carrier signal and inputs it into the cable, which is then transmitted to the decoding circuit via the cable;

[0020] (2) The steady-state TTL carrier signal is output as a high-level enhanced TTL signal through a high-pass filter. The signal is then amplified by an amplifier, and then the voltage follower is used to increase the input impedance and provide isolation. Finally, the signal is shaped by a hysteresis comparator and output as a standard TTL level signal, which is then input into the TTL universal serial port 2 of the downhole microcontroller system.

[0021] Through the above technical solution, the underground DC carrier communication system and communication method based on TTL serial port modulation provided by the present invention have the following beneficial effects:

[0022] 1. The present invention is based on the design of TTL serial port modulating DC carrier signal, and uses two DC regulated power supplies to directly modulate low-frequency steady-state TTL carrier signal. The low-frequency signal improves the reliability of communication by sacrificing the communication rate. The steady-state signal provides a stable baseline voltage with strong anti-interference ability, solves the voltage fluctuation problem caused by transient signal coupling, and improves the stability of the communication system.

[0023] 2. The present invention is based on a downhole decoding circuit for a TTL carrier signal. The simplified circuit adopts a fixed gain and modulates a high-level enhanced TTL signal. There is no need to adjust the gain, which avoids wasting a lot of time on adjusting the amplification factor for different well conditions, improves efficiency, and improves the reliability of the communication system by reducing the carrier signal frequency.

[0024] 3. The present invention is based on the TTL carrier signal downhole decoding circuit. The generated standard TTL signal has strict level control and complies with the TTL standard level specification. It can be directly compatible with the existing single-chip microcomputer TTL universal serial port, reducing additional signal conversion steps, simplifying system design, reducing the demand for external modules and circuits, and reducing design complexity and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0026] Figure 1 A schematic diagram of an underground DC carrier communication system based on TTL serial port modulation disclosed in an embodiment of the present invention.

[0027] Figure 2 This is a connection diagram for the high-speed switching module.

[0028] Figure 3 Input and output waveform diagram of the present invention, (a) is the input signal, (b) is the output signal.

[0029] Figure 4 This is the TTL serial port modulation waveform diagram of the present invention.

[0030] Figure 5 Schematic diagram of a decoding circuit of the present invention.

[0031] Figure 6 It is a schematic diagram of the decoding circuit signal of the present invention. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0033] The present invention provides an underground DC carrier communication system based on TTL serial port modulation, such as Figure 1 As shown, it includes a ground part and an underground part, which are connected by cables. This system adopts single-core steel pipe cable DC carrier communication technology. The single-core cable not only provides power for the terminal equipment, but also provides an information transmission channel, solving the problem of human, material and financial resource losses caused by the addition of cables.

[0034] The ground part includes TTL universal serial port 1, high-speed switching switch module, DC regulated power supply 1 and DC regulated power supply 2; the underground part includes decoding circuit and TTL universal serial port 2.

[0035] The high-speed switch module is connected to the TTL universal serial port 1. The TTL universal serial port 1 is used to send TTL serial port signals as control signals for the high-speed switch module. The high-speed switch module connection diagram is as follows: Figure 2 As shown, the high-speed switching switch module is used to switch the DC regulated power supply 1 and the DC regulated power supply 2 according to the level of the TTL serial port signal, modulate a steady-state TTL carrier signal input cable, and transmit it to the decoding circuit through the cable.

[0036] In this embodiment, the TTL universal serial port 1 sends a TTL serial port signal with a baud rate of 600 as the control signal of the high-speed switch switching module. The voltages of the DC regulated power supply 1 and the DC regulated power supply 2 are 60V and 70V respectively. The high-speed switch switching module switches according to the high and low levels of the control signal. When the control signal is a low level of 0V, it outputs a steady-state voltage of 60V; when the control signal is a high level of 5V, it outputs a steady-state voltage of 70V.

[0037] The TTL serial port signal is used as a control signal to modulate a steady-state TTL carrier signal through a high-speed switch module. The input and output waveforms are shown in the figure below. Figure 3As shown in (a) and (b), compared with the initial control signal, the voltage difference is increased to 10V while maintaining the same timing. The same timing ensures high accuracy of data transmission. Increasing the voltage difference can effectively overcome signal attenuation and is suitable for long-distance transmission and underground scenarios with higher anti-interference requirements. The two DC regulated power supplies provide a stable baseline voltage with strong anti-interference ability, solve the voltage fluctuation problem caused by transient signal coupling, and improve the reliability of signal transmission.

[0038] This system uses TTL serial port modulation DC carrier signal method, using level and time to transmit information, such as Figure 4 As shown in the figure, when there is no data transmission, it is in idle state, and the serial port output maintains a high level. When data is transmitted, a start bit must be sent before transmitting data. The start bit must adopt a low level mode. The high level of the idle state is broken by the low level of the start bit, so that the signal generates a falling edge. The receiving device detects this falling edge and starts to receive this frame of data. The 1.67ms±0.05ms low level represents the start bit, the 1.67ms±0.05ms high level represents the data "1", and the 1.67ms±0.05ms low level represents the data "0". Under the premise that the real-time requirements of communication are not high, the reliability of communication is improved by sacrificing the data transmission rate.

[0039] The downhole decoding circuit needs to adjust the signal voltage value to the recognizable range of the downhole microcontroller while retaining the control command information. The modulated low-frequency steady-state TTL carrier signal is transmitted to the downhole decoding circuit through the cable. The downhole decoding circuit design of the communication system is as follows: Figure 5 shown.

[0040] The decoding circuit includes a high-pass filter, an amplifier, a voltage follower and a hysteresis comparator. The high-pass filter is used to filter out the DC signal and convert it into a high-level enhanced TTL signal; the amplifier is used to amplify the signal three times to shorten the rise and fall time; the voltage follower is used to increase the input impedance and provide isolation to prevent the previous circuit from being affected by the subsequent load; the hysteresis comparator is used to shape the signal so that its output amplitude meets the standard TTL signal requirements and effectively filters out high-frequency interference.

[0041] The high-pass filter includes capacitor C1 (47uF), resistor R1 (10kΩ), diode D1 (MURS120) and resistor R2 (100Ω). The steady-state TTL carrier signal is input from the cable and connected to one end of capacitor C1. The other end of capacitor C1 is connected to the positive electrode of diode D1 and the negative electrode of diode D1 is grounded. Resistor R1 is connected in parallel with diode D1 and connected to the ground to form a high-pass filter, which limits the input signal and protects the subsequent circuits. One end of resistor R2 is connected to the output end of C1 and the other end is connected to the next stage.

[0042] The amplifier includes an operational amplifier U1.1 (TLV2372QDRQ1), a capacitor C2 (22pF), a capacitor C3 (0.1uF), a resistor R3 (1kΩ), and a resistor R4 (3kΩ). Pin 3 of the operational amplifier U1.1 receives a signal from the high-pass filter from the resistor R2; the capacitor C2 and the resistor R4 are connected in parallel, and the two ends are connected to the pins 1 and 2 of the operational amplifier U1.1; one end of the resistor R3 is connected to the pin 2 of the operational amplifier U1.1, and the other end is grounded; the pin 8 of the operational amplifier U1.1 is connected to the 5V power supply voltage and one end of the capacitor C3, and the other end of the capacitor C3 is grounded; the output pin 1 of the operational amplifier U1.1 is connected to the next stage.

[0043] The voltage follower includes an operational amplifier U1.2 (TLV2372QDRQ1) and a resistor R5 (10kΩ). The output pin 1 of the operational amplifier U1.1 is connected to the non-inverting input pin 5 of the operational amplifier U1.2, the inverting input pin 6 of the operational amplifier U1.2 is directly connected to its output pin 7, and one end of the resistor R5 is connected to pin 7 of the operational amplifier U1.2, and the other end is connected to the next stage.

[0044] The hysteresis comparator includes tantalum capacitor C4 (10uF), capacitor C5 (5.6pF), capacitor C6 (0.1uF), resistor R5 (10kΩ), resistor R6 (100kΩ), resistor R7 (130kΩ), resistor R8 (10kΩ), resistor R9 (56kΩ), resistor R10 (1kΩ) and operational amplifier U2.1 (TLV2372QDRQ1). The inverting input pin 2 of the operational amplifier U2.1 receives a signal from the output of the voltage follower; the 5V power supply is grounded after passing through resistors R7 and R6, and the negative electrode of the tantalum capacitor C4 is grounded and connected in parallel with the resistor R6 to form a trigger hysteresis network; one end of the resistor R8 is connected to the positive electrode of the tantalum capacitor C4, and the other end is connected to pin 3 of the operational amplifier U2.1; the resistor R9 is connected in parallel to pins 1 and 3 of the operational amplifier U2.1; the capacitor C5 is connected in parallel across the resistor R9; one end of the capacitor C6 is grounded, and the other end is connected to pin 8 of the operational amplifier U2.1, and the output pin 1 passes through the resistor R10 to output a TTL universal serial port 2 compatible signal.

[0045] An underground DC carrier communication method based on TTL serial port modulation adopts the above-mentioned underground DC carrier communication system based on TTL serial port modulation, including the following process:

[0046] (1) The TTL universal serial port 1 sends a TTL serial port signal as a control signal for the high-speed switching module. The high-speed switching module switches the DC regulated power supply 1 and the DC regulated power supply 2 according to the level of the TTL serial port signal, modulates a steady-state TTL carrier signal and inputs it into the cable, which is then transmitted to the decoding circuit via the cable.

[0047] Based on the frequency response analysis of the single-core steel pipe cable model, the carrier signal frequency should be lower than 3.1kHz in theory. The existing capacitive coupling technology generally modulates high-frequency signals. For modulating low-frequency signals, it is not suitable for modulating low-frequency signals due to the limitations of the existing modulation technology. Therefore, the present invention proposes a method for modulating a steady-state TTL carrier signal based on a TTL serial port, using a universal TTL serial port to send a TTL serial port signal with a baud rate of 600 as the control signal of the high-speed switch switching module, and inputting two 60V and 70V DC regulated power supplies as power supply and steady-state input signals for modulating a steady-state TTL carrier signal.

[0048] (2) The steady-state TTL carrier signal is output as a high-level enhanced TTL signal through a high-pass filter, which retains the timing characteristic amplitude of the standard TTL signal and increases from the standard TTL 0-5V to 0-10V. The high-level characteristic of the high-level enhanced TTL signal can effectively overcome the attenuation of the amplitude, avoid wasting a lot of time repeatedly adjusting the signal amplitude underground, and improve efficiency.

[0049] The signal is then amplified three times through a fixed-gain amplifier to shorten the rise and fall time.

[0050] A voltage follower is then input to increase the input impedance, provide isolation, and prevent the previous stage circuit from being affected by the subsequent load.

[0051] Finally, the hysteresis comparator outputs the voltage above 2.4V as a high level 5V, and the voltage below 0.67V as a low level 0V. After signal shaping, the standard TTL level signal is output and input into the TTL universal serial port 2 of the underground single-chip microcomputer system.

[0052] The final modulated standard signal is consistent with the control signal timing and amplitude, and the microcontroller can directly configure the input port to read the standard TTL level signal. Figure 6 As shown, the steady-state TTL carrier signal on the cable is input into the downhole decoding circuit, and a high-level enhanced TTL signal is output through a high-pass filter. The subsequent amplifier, voltage follower, and hysteresis comparator shape the signal and output a standard TTL level signal, which is adjusted to within the recognizable range of the downhole single-chip microcomputer and can be directly input into the TTL universal serial port of the downhole single-chip microcomputer system.

[0053] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An underground DC carrier communication system based on TTL serial port modulation, characterized in that: It includes a surface part and a downhole part, and the surface part and the downhole part are connected by a cable; The surface part includes a TTL universal serial port 1, a high-speed switching switch module, a DC regulated power supply 1 and a DC regulated power supply 2; the underground part includes a decoding circuit and a TTL universal serial port 2; The high-speed switching switch module is connected to the TTL universal serial port 1, and the TTL universal serial port 1 is used to send a TTL serial port signal as a control signal of the high-speed switching switch module. The high-speed switching switch module is used to switch the DC regulated power supply 1 and the DC regulated power supply 2 according to the level of the TTL serial port signal, and modulate a steady-state TTL carrier signal to input the cable, and transmit it to the decoding circuit through the cable; The decoding circuit includes a high-pass filter, an amplifier, a voltage follower and a hysteresis comparator. The high-pass filter is used to filter out the DC signal and convert it into a high-level enhanced TTL signal; the amplifier is used to amplify the signal three times to shorten the rising and falling edge time; the voltage follower is used to increase the input impedance and provide isolation to prevent the previous stage circuit from being affected by the subsequent load; the hysteresis comparator is used to shape the signal so that its output amplitude meets the standard TTL signal requirements and effectively filters out high-frequency interference.

2. According to the underground DC carrier communication system based on TTL serial modulation according to claim 1, it is characterized in that: The TTL universal serial port 1 sends a TTL serial port signal with a baud rate of 600 as a control signal of the high-speed switch switching module. The voltages of the DC regulated power supply 1 and the DC regulated power supply 2 are 60V and 70V respectively. The high-speed switch switching module switches according to the high and low levels of the control signal. When the control signal is a low level of 0V, it outputs a steady-state voltage of 60V; when the control signal is a high level of 5V, it outputs a steady-state voltage of 70V.

3. According to the underground DC carrier communication system based on TTL serial modulation according to claim 1, it is characterized in that: The high-pass filter comprises a capacitor C1, a resistor R1, a diode D1 and a resistor R2; a steady-state TTL carrier signal is input from a cable and connected to one end of the capacitor C1, the other end of the capacitor C1 is connected to the positive electrode of the diode D1, and the negative electrode of the diode D1 is grounded, the resistor R1 is connected in parallel with the diode D1, and is connected to the ground to form a high-pass filter, and the input signal is limited and the subsequent circuit is protected; one end of the resistor R2 is connected to the output end of C1, and the other end is connected to the next stage.

4. The underground DC carrier communication system based on TTL serial modulation according to claim 3 is characterized in that: The amplifier includes an operational amplifier U1.1, a capacitor C2, a capacitor C3, a resistor R3 and a resistor R4; pin 3 of the operational amplifier U1.1 receives a signal from a high-pass filter from resistor R2; capacitor C2 and resistor R4 are connected in parallel, and both ends are connected to pin 1 and pin 2 of the operational amplifier U1.1; one end of resistor R3 is connected to pin 2 of the operational amplifier U1.1, and the other end is grounded; pin 8 of the operational amplifier U1.1 is connected to a 5V power supply voltage and one end of capacitor C3, and the other end of capacitor C3 is grounded; output pin 1 of the operational amplifier U1.1 is connected to the next stage.

5. The underground DC carrier communication system based on TTL serial modulation according to claim 4 is characterized in that: The voltage follower includes an operational amplifier U1.2 and a resistor R5, wherein the output pin 1 of the operational amplifier U1.1 is connected to the non-inverting input pin 5 of the operational amplifier U1.2, the inverting input pin 6 of the operational amplifier U1.2 is directly connected to its output pin 7, and one end of the resistor R5 is connected to pin 7 of the operational amplifier U1.2, and the other end is connected to the next stage.

6. The underground DC carrier communication system based on TTL serial modulation according to claim 5 is characterized in that: The hysteresis comparator includes a tantalum capacitor C4, a capacitor C5, a capacitor C6, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10 and an operational amplifier U2.1; the inverting input pin 2 of the operational amplifier U2.1 receives a signal from the output of the voltage follower; the 5V power supply is grounded after passing through resistors R7 and R6, the negative electrode of the tantalum capacitor C4 is grounded and connected in parallel with the resistor R6 to form a trigger hysteresis network; one end of the resistor R8 is connected to the positive electrode of the tantalum capacitor C4, and the other end is connected to the pin 3 of the operational amplifier U2.1; the resistor R9 is connected in parallel to the pins 1 and 3 of the operational amplifier U2.1; the capacitor C5 is connected in parallel to both ends of the resistor R9; one end of the capacitor C6 is grounded, and the other end is connected to the pin 8 of the operational amplifier U2.1, and the output pin 1 outputs a TTL universal serial port 2 compatible signal through the resistor R10.

7. A method for underground DC carrier communication based on TTL serial port modulation, using an underground DC carrier communication system based on TTL serial port modulation as claimed in any one of claims 1 to 6, characterized in that: The process includes the following: (1) The TTL universal serial port 1 sends a TTL serial port signal as a control signal of the high-speed switching switch module. The high-speed switching switch module switches the DC regulated power supply 1 and the DC regulated power supply 2 according to the level of the TTL serial port signal, modulates a steady-state TTL carrier signal and inputs it into the cable, which is then transmitted to the decoding circuit via the cable; (2) The steady-state TTL carrier signal is output as a high-level enhanced TTL signal through a high-pass filter. The signal is then amplified by an amplifier, and then the voltage follower is used to increase the input impedance and provide isolation. Finally, the signal is shaped by a hysteresis comparator and output as a standard TTL level signal, which is then input into the TTL universal serial port 2 of the downhole microcontroller system.

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