An electrical exploration signal sending device and method for suppressing electromagnetic coupling interference

Abstract

The present invention discloses an electrical exploration signal transmission device for suppressing electromagnetic coupling interference. The device comprises a rectangular wave signal source, an output circuit for supplying power to the ground, and multiple transmission channels. Each transmission channel includes an isolation drive circuit, a low-pass filter circuit, and a power amplifier circuit connected in series. The rectangular wave signal source generates a rectangular wave or a composite rectangular wave. The signal output of the rectangular wave signal source is connected to the input of the isolation drive circuit of each transmission channel. The output of the power amplifier circuits of all transmission channels is connected to the output circuit for supplying power to the ground. The present invention employs an RC low-pass filter circuit to directly reduce the edge change rate of the rectangular wave before performing high-fidelity power amplification and then supplying power to the ground. This significantly reduces electromagnetic coupling interference generated by the electrical exploration signal transmission circuit, improves the signal-to-noise ratio (SNR) of the received signal, and improves the quality of received data. In frequency-domain induced polarization (IP) applications, the present invention is particularly effective in suppressing the effects of electromagnetic coupling interference on IP signal measurements.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical prospecting, and in particular to an electrical prospecting signal sending device and method for suppressing electromagnetic coupling interference. Background Art

[0002] In the field of artificial source electrical exploration, the problem of electromagnetic coupling interference is common, especially in the application of frequency domain induced polarization.

[0003] Frequency-domain IP (FDI) interference, commonly used in the frequency range of 0.01Hz to 10Hz, is a common method for mineral resource surveying and exploration. It is widely used due to its lightweight design, strong anti-interference capabilities, simple operation, and the absence of terrain correction. Electromagnetic coupling interference is caused by both inductive and capacitive coupling between the transmitter output circuit and the receiver input circuit. The strength of electromagnetic coupling is primarily determined by inductive coupling, and the degree of interference increases with decreasing ground resistivity, increasing frequency, and increasing inter-electrode spacing. This interference directly affects the IP amplitude-frequency measurements and is a significant interference factor in FDI applications.

[0004] To correct for electromagnetic coupling interference, domestic and international researchers primarily use data processing methods to correct for its effects. This approach works well when electromagnetic coupling is weak, but generally becomes less effective when electromagnetic coupling interference increases, making it difficult to meet the needs of field exploration under complex geological conditions. Regarding direct hardware decoupling, the patent "A Precision Synchronous Chopper Decoupler for Frequency Domain Electrical Instruments GPS," ZL200710035797.9, invents a method for eliminating electromagnetic coupling interference by synchronous chopping of the received signal of the observation system. While effective, this method also suffers from measurement errors introduced by chopping and requires strict synchronization between the transmitter and receiver. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a simple-structured electrical prospecting signal sending device for suppressing electromagnetic coupling interference, and provides a method for sending electrical prospecting signals for suppressing electromagnetic coupling interference.

[0006] The technical solution of the present invention to solve the above-mentioned problem is: an electrical exploration signal transmitting device for suppressing electromagnetic coupling interference, including a rectangular wave signal source, an output circuit for supplying power to the earth, and multiple transmitting channels, each transmitting channel including an isolation drive circuit, a low-pass filter circuit, and a power amplifier circuit connected in series in sequence, the rectangular wave signal source generates a rectangular wave or a composite rectangular wave, the signal output end of the rectangular wave signal source is connected to the input end of the isolation drive circuit of each transmitting channel, and the output ends of the power amplifier circuits of all transmitting channels are connected to the output circuit for supplying power to the earth.

[0007] The above-mentioned electrical exploration signal sending device for suppressing electromagnetic coupling interference, the isolation drive circuit includes a first resistor, a second resistor, an optocoupler, a first field-effect transistor, and a second field-effect transistor. One end of the first resistor serves as the input end of the isolation drive circuit and is connected to the output end of the rectangular wave signal source. The other end of the first resistor is connected to the first pin of the optocoupler, the second pin of the optocoupler is grounded, the fourth pin of the optocoupler is respectively connected to one end of the second resistor, the gate of the first field-effect transistor, and the gate of the second field-effect transistor. The other end of the second resistor and the source of the first field-effect transistor are connected to the reference power supply VCC. The third pin of the optocoupler and the source of the second field-effect transistor are both connected to the reference negative power supply VEE of the channel. The drain of the first field-effect transistor is connected to the drain of the second field-effect transistor and serves as the output end of the isolation drive circuit.

[0008] In the above-mentioned electrical prospecting signal sending device for suppressing electromagnetic coupling interference, the first field effect transistor is a P-channel enhancement type field effect transistor, and the second field effect transistor is an N-channel enhancement type field effect transistor.

[0009] In the above-mentioned electrical exploration signal transmitting device for suppressing electromagnetic coupling interference, the low-pass filter circuit includes a capacitor and a first switch. One end of the first switch serves as the input end of the low-pass filter circuit and is connected to the output end of the isolation drive circuit. The other end of the first switch is connected to one end of the capacitor and serves as the output end of the low-pass filter circuit. The other end of the capacitor is grounded. Several branches are connected in parallel at both ends of the first switch, each branch including a resistor and a switch connected in series.

[0010] In the above-mentioned electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference, the time constant of the low-pass filter circuit of each transmitting channel is the same, and the time constant is set between 0 and 40 mS.

[0011] The above-mentioned electrical exploration signal sending device for suppressing electromagnetic coupling interference, the rectangular wave signal source adopts one of a single-chip microcomputer, a programmable logic device CPLD, a field programmable gate array device FPGA, a digital signal processor DSP, a direct digital frequency synthesizer DDS, and a sequential logic circuit.

[0012] In the above-mentioned electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference, the output ends of the power amplifier circuits of all transmitting channels are individually, or multiple power amplifier circuits are connected in series to output circuits to supply power to the earth.

[0013] A method for sending an electrical prospecting signal to suppress electromagnetic coupling interference comprises the following steps:

[0014] Step 1: The rectangular wave signal source generates a rectangular wave or a composite rectangular wave signal and sends it to each transmission channel;

[0015] Step 2: In each transmission channel, the isolation driving circuit electrically isolates the rectangular wave or composite rectangular wave signal generated by the rectangular wave signal source and then outputs it;

[0016] Step 3: The low-pass filter circuit filters the signal output by the isolation drive circuit and then outputs it;

[0017] Step 4: The power amplifier circuit amplifies the signal output by the low-pass filter circuit and outputs it;

[0018] Step 5: The signals output by the power amplifier circuits in each transmission channel pass through the output loop and are connected individually or in series to supply power to the ground.

[0019] In the above-mentioned method for sending electrical prospecting signals to suppress electromagnetic coupling interference, in step three, the number of connected branches is changed by changing the on-off state of the branch switches in the low-pass filter circuit, thereby changing the time constant of the low-pass filter circuit.

[0020] The beneficial effects of the present invention are:

[0021] 1. The electrical prospecting signal transmitting device of the present invention includes a low-pass filter circuit. By changing the on-off state of the branch switches in the low-pass filter circuit, the number of connected branches can be changed, thereby changing the time constant of the low-pass filter circuit, and further adjusting the edge change rate of the output waveform, suppressing the high-order components in the output waveform of the transmission circuit, significantly reducing the inductive coupling interference of the transmission circuit current on the receiver input circuit, and suppressing the impact of electromagnetic coupling interference on the receiver measurement data.

[0022] 2. The edge change rate of the transmitter output waveform of the present invention can be set according to the needs of field work by switching the time constant of the low-pass filter circuit. The transmitter output waveform is less affected by the grounding conditions and is easy to operate.

[0023] 3. When a higher output voltage is required for the electrical prospecting signal transmitting device of the present invention, the output ends of any multiple transmitting channels can be cascaded (connected in series) to provide a higher output voltage.

[0024] 4. The present invention uses an RC low-pass filter circuit to directly reduce the edge change rate of the rectangular wave and then performs high-fidelity power amplification, and then supplies power to the earth, thereby significantly reducing the electromagnetic coupling interference generated by the electrical exploration signal transmission circuit and improving the signal-to-noise ratio of the received signal and the quality of the received data; the present invention is suitable for use in electrical exploration signal transmission, and is particularly suitable for use in frequency domain induced polarization signal transmission schemes to suppress the influence of electromagnetic coupling interference on induced polarization signal measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a structural block diagram of the electrical prospecting signal sending device of the present invention.

[0026] Figure 2 for Figure 1 The schematic diagram of the isolated drive circuit.

[0027] Figure 3 for Figure 1 Circuit schematic diagram of low-pass filter circuit.

[0028] Figure 4 This is a simulation diagram of the rectangular wave rising edge waveform of the present invention.

[0029] Figure 5 This is a simulation diagram of the rectangular wave falling edge waveform of the present invention.

[0030] Figure 6 This is a schematic diagram of the output waveform of the present invention after the square wave passes through the isolation drive circuit and the low-pass filter circuit.

[0031] Figure 7 This is a schematic diagram of the output waveform of the combined rectangular wave after passing through the isolation drive circuit and the low-pass filter circuit when the present invention sends it. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and examples.

[0033] like Figure 1 As shown, an electrical exploration signal transmitting device for suppressing electromagnetic coupling interference includes a rectangular wave signal source, an output circuit for supplying power to the ground, and multiple transmission channels. Each transmission channel includes an isolation drive circuit, a low-pass filter circuit, and a power amplifier circuit connected in series. The first transmission channel includes an isolation drive circuit 1, a low-pass filter circuit 1, and a power amplifier circuit 1; the second transmission channel includes an isolation drive circuit 2, a low-pass filter circuit 2, and a power amplifier circuit 2; the third transmission channel includes an isolation drive circuit 3, a low-pass filter circuit 3, and a power amplifier circuit 3; ...; the nth transmission channel includes an isolation drive circuit n, a low-pass filter circuit n, and a power amplifier circuit n. The rectangular wave signal source generates a rectangular wave or a composite rectangular wave. The signal output end of the rectangular wave signal source is connected to the input end of the isolation drive circuit of each transmission channel. The output ends of the power amplifier circuits of all transmission channels can be connected individually or in cascade (series) to the output circuit to supply power to the ground.

[0034] The rectangular wave signal source usually uses a single-chip microcomputer to generate a rectangular wave or a composite rectangular wave signal, and can also use a complex programmable logic device CPLD, a field programmable gate array device FPGA, a digital signal processor DSP, a direct digital frequency synthesizer DDS, or build a sequential logic circuit to generate it.

[0035] The isolation drive circuit can be one of the following: optical coupler isolation, optical fiber isolation, isolation drive chip, isolation drive module to realize the isolation drive function. Figure 2As shown, the isolation drive circuit includes a first resistor R01, a second resistor R02, an optocoupler U1, a first field effect transistor Q1, and a second field effect transistor Q2. The first field effect transistor Q1 is a P-channel enhancement mode field effect transistor, and the second field effect transistor Q2 is an N-channel enhancement mode field effect transistor. One end of the first resistor R01 serves as the input terminal IN of the isolation drive circuit and is connected to the output terminal of the rectangular wave signal source. The other end of the first resistor R01 is connected to the first pin of the optocoupler U1. The second pin of the optocoupler U1 is grounded. The fourth pin of the optocoupler U1 is respectively connected to one end of the second resistor R02, the gate of the first field effect transistor Q1, and the gate of the second field effect transistor Q2. The other end of the second resistor R02 and the source of the first field effect transistor Q1 are connected to the reference power supply VCC. The third pin of the optocoupler U1 and the source of the second field effect transistor Q2 are both connected to the reference negative power supply VEE of the channel. The drain of the first field effect transistor Q1 is connected to the drain of the second field effect transistor Q2 and serves as the output terminal of the isolation drive circuit.

[0036] Figure 2 In the circuit, the rectangular wave or composite rectangular wave generated by the rectangular wave signal source is input to pin 1 and output to pin 4 of optocoupler U1. When the rectangular wave signal source outputs a high level, the LED inside optocoupler U1 illuminates, the phototransistor saturates, and conducts. Pin 4 of optocoupler U1 outputs a low level, turning Q1 on and Q2 off, and LPiin outputs a high level (VCC). When the rectangular wave signal source outputs a low level, the LED inside optocoupler U1 illuminates, the phototransistor turns off, and LPiin outputs a high level (VEE). The isolation driver circuit electrically isolates the rectangular wave signal source from the subsequent circuitry of optocoupler U1 and clamps the rectangular wave signal within the VEE to VCC range (high level VCC, low level VEE, where VCC and VEE are equal, high-precision positive and negative power supplies, respectively).

[0037] The low-pass filter circuit is an RC low-pass filter circuit with a fixed time constant or multiple selectable or adjustable time constants; Figure 3As shown, the low-pass filter circuit includes a capacitor C and a resistor that can be switched arbitrarily in series with the capacitor. The resistor and the capacitor form an RC low-pass filter circuit. The signal after low-pass filtering is output from the upper end of the capacitor C, i.e., the LPout end. The output end of the isolation drive circuit is connected to the LPiin end of the low-pass filter circuit. The LPiin end is connected to the left end of the switch S0, the left end of the resistor R1, the left end of the resistor R2, ..., and the left end of the resistor Rn. The right end of the resistor R1 is connected to the left end of the switch S1, the right end of the resistor R2 is connected to the left end of the switch S2, ..., and the right end of the resistor Rn is connected to the left end of the switch Sn. The upper end of the capacitor C is connected to the right end of the switch S0, the right end of the switch S1, the right end of the switch S2, ..., and the right end of the switch Sn, respectively. The lower end of the capacitor C is connected to the power ground. The signal after low-pass filtering is output from the upper end of the capacitor, i.e., the LPout end, to the input end of the power amplifier circuit.

[0038] In the application of frequency domain induced polarization, the frequency of the rectangular wave signal is usually between 0.01Hz and 10Hz, the time constant is set between 0 and 40mS, the time constant is adjustable or multiple time constants are switchable, and the time constant of the low-pass filter circuit of each transmission channel is the same.

[0039] The power amplifier circuit utilizes a high-fidelity digital power amplifier circuit, either an analog or digital power amplifier circuit, offering high power conversion efficiency, portability, and reliability. The amplifier gain is designed with multiple selectable levels or a fixed gain to ensure gain accuracy and output level stability. The output terminals of all transmit channels can independently supply current to the ground. Alternatively, the output terminals can be connected in cascade (series) to provide ground power for higher output voltages. Alternatively, in areas with very low ground resistance, the output terminals can be connected in parallel to provide even greater output current.

[0040] A method for sending an electrical prospecting signal to suppress electromagnetic coupling interference comprises the following steps:

[0041] Step 1: The rectangular wave signal source generates a rectangular wave or a composite rectangular wave signal and sends it to each transmission channel;

[0042] Step 2: In each transmission channel, the isolation driving circuit electrically isolates the rectangular wave or composite rectangular wave signal generated by the rectangular wave signal source and then outputs it;

[0043] Step 3: The low-pass filter circuit filters the signal output by the isolation drive circuit and then outputs it. By changing the on and off of the branch switch in the low-pass filter circuit, the number of connected branches is changed, thereby changing the time constant of the low-pass filter circuit;

[0044] Step 4: The power amplifier circuit amplifies the signal output by the low-pass filter circuit and outputs it;

[0045] Step 5: The signals output by the power amplifier circuits in each transmission channel pass through the output loop and are connected individually or in series to supply power to the ground.

[0046] After sampling, the transmitter output signal is sent to the receiver as a calibration signal for calibration. After the calibration, the receiver can perform actual measurements. After switching the low-pass filter time constant of the transmitter, the receiver needs to be calibrated online with the transmitter before actual measurements can be performed. The receiver can also be calibrated online one by one for each low-pass filter time constant of the transmitted waveform in advance. During construction, it is agreed that the low-pass filter time constant of the transmitter and its corresponding receiver calibration gear remain consistent, and actual measurements can be performed.

[0047] See also Figure 4 and Figure 5 The rectangular wave edge low-pass filtering simulation diagram of the present invention can change the rectangular wave edge change rate by switching the low-pass filtering time constant. After the power amplifier is output to supply power to the earth, the electromagnetic coupling interference caused by the sending end of the electrical exploration signal can be greatly reduced.

[0048] See also Figure 6-Figure 7 , Figure 6-Figure 7 This is a waveform diagram of some test points of the signal sending device when sending square waves or combined rectangular waves of the present invention. Figure 6 is the waveform when sending square wave, Figure 6 Medium waveform u 1 is a schematic diagram of the output waveform of the rectangular wave signal source after passing through the isolation drive circuit. u 2 is the waveform u 1 Output waveform after low-pass filtering, u The waveform of 2 is amplified by the power amplifier circuit with high efficiency and fidelity to supply power to the earth, or the output ends of the power amplifiers of multiple signal transmission channels are cascaded (connected in series) to output a higher voltage square wave signal to supply power to the earth; Figure 7 To send a combined rectangular wave waveform, the waveform u 3 is a schematic diagram of the output waveform of the rectangular wave signal source after passing through the isolation drive circuit. u 4 is the waveform u 3 Schematic diagram of the output waveform after low-pass filtering, u The waveform shown in 4 is amplified with high efficiency and fidelity by the subsequent power amplifier circuit to supply power to the ground, or the power amplifier output ends of multiple signal transmission channels are cascaded (connected in series) to output a higher voltage combined rectangular wave signal to supply power to the ground.

Claims

1. An electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference, characterized by: It includes a rectangular wave signal source, an output circuit for supplying power to the ground, and multiple transmission channels. Each transmission channel includes an isolation drive circuit, a low-pass filter circuit, and a power amplifier circuit connected in series. The rectangular wave signal source generates a rectangular wave or a composite rectangular wave. The signal output end of the rectangular wave signal source is connected to the input end of the isolation drive circuit of each transmission channel. The output end of the power amplifier circuit of all transmission channels is connected to the output circuit for supplying power to the ground. The low-pass filter circuit includes a capacitor and a first switch. One end of the first switch serves as the input end of the low-pass filter circuit and is connected to the output end of the isolation drive circuit. The other end of the first switch is connected to one end of the capacitor and serves as the output end of the low-pass filter circuit. The other end of the capacitor is grounded. Several branches are connected in parallel at both ends of the first switch, and each branch includes a resistor and a switch connected in series.

2. The electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference according to claim 1, characterized in that: The isolation drive circuit includes a first resistor, a second resistor, an optocoupler, a first field-effect transistor, and a second field-effect transistor. One end of the first resistor serves as the input end of the isolation drive circuit and is connected to the output end of the rectangular wave signal source. The other end of the first resistor is connected to the first pin of the optocoupler, the second pin of the optocoupler is grounded, the fourth pin of the optocoupler is respectively connected to one end of the second resistor, the gate of the first field-effect transistor, and the gate of the second field-effect transistor. The other end of the second resistor and the source of the first field-effect transistor are connected to the reference power supply VCC. The third pin of the optocoupler and the source of the second field-effect transistor are both connected to the reference negative power supply VEE of the channel. The drain of the first field-effect transistor is connected to the drain of the second field-effect transistor and serves as the output end of the isolation drive circuit.

3. The electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference according to claim 2, characterized in that: The first field effect transistor is a P-channel enhancement mode field effect transistor, and the second field effect transistor is an N-channel enhancement mode field effect transistor.

4. The electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference according to claim 1, characterized in that: The time constant of the low-pass filter circuit of each transmission channel is the same, and the time constant is set between 0 and 40mS.

5. The electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference according to claim 1, characterized in that: The rectangular wave signal source adopts one of a single chip microcomputer, a programmable logic device CPLD, a field programmable gate array device FPGA, a digital signal processor DSP, a direct digital frequency synthesizer DDS, and a sequential logic circuit.

6. The electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference according to claim 1, characterized in that: The output ends of the power amplifier circuits of all the transmission channels are individually, or a plurality of power amplifier circuits are connected in series to output a loop to supply power to the ground.

7. A method for transmitting an electrical prospecting signal using an electrical prospecting signal transmitting device for suppressing electromagnetic coupling interference according to any one of claims 1 to 6, comprising the following steps: Step 1: The rectangular wave signal source generates a rectangular wave or a composite rectangular wave signal and sends it to each transmission channel; Step 2: In each transmission channel, the isolation driving circuit electrically isolates the rectangular wave or composite rectangular wave signal generated by the rectangular wave signal source and then outputs it; Step 3: The low-pass filter circuit filters the signal output by the isolation drive circuit and then outputs it; Step 4: The power amplifier circuit amplifies the signal output by the low-pass filter circuit and outputs it; Step 5: The signals output by the power amplifier circuits in each transmission channel pass through the output loop and are connected individually or in series to supply power to the ground.

8. The method for transmitting electrical prospecting signals according to claim 7, wherein: In the step three, the number of connected branches is changed by changing the on-off state of the branch switches in the low-pass filter circuit, thereby changing the time constant of the low-pass filter circuit.

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