A transmitting and receiving method of a water acoustic transducer based on an optical coupling isolator

Abstract

This invention provides a transceiver method for an underwater acoustic transceiver based on an optocoupler isolator, relating to the field of signal processing circuit technology, and applied to a transceiver circuit with integrated transmission and reception. The method identifies the transceiver's current transmitting or receiving state by detecting control command signals, and uses the optocoupler isolator to drive the controlled switch to open or close, achieving connection or isolation between the power amplifier and the transceiver. In transmitting state, the excitation signal drives the transceiver to emit sound through a closed path; in receiving state, the transceiver receives the echo signal and outputs an analog signal, which is then limited and amplified in two stages before being output to the signal acquisition unit. This invention offers advantages such as fast response, stable signal switching, good electrical isolation, and adaptability to high-voltage drives, making it suitable for low-noise, high-precision underwater acoustic signal transceiver applications.

Description

Technical Field

[0001] This invention relates to the field of signal processing circuit technology, and in particular to a transceiver method for an underwater acoustic transducer based on an optocoupler isolator. Background Technology

[0002] Underwater acoustic transducers are important technological tools for humans to utilize sound waves in marine research and marine resource development. Underwater acoustic transducers are generally divided into two categories: transmitting transducers that are used only for transmitting signals and transceiver transducers that simultaneously transmit and receive signals. Transceiver transducers, in particular, because they simultaneously transmit and receive external acoustic signals, usually require specially designed external circuitry to assist in reliably switching between signal transmission, reception, and transmit / receive states.

[0003] In existing technologies, the external circuitry of a transceiver generally includes at least three main functional modules: a transmitting circuit module for applying a high-voltage power signal to the transceiver to drive its transmission; a receiving circuit module for effectively amplifying the weak acoustic signal received by the transceiver and transmitting it to subsequent acquisition equipment; and a transceiver conversion module for fast and reliable switching between the two different operating states of transmission and reception. Currently, the most common transceiver conversion module solutions are the RF switch solution and the PIN diode solution. While the RF switch solution offers faster switching speeds, its power handling capability is limited, making it only suitable for low-power, low-voltage signal applications. The PIN diode solution, on the other hand, is typically used in conjunction with a current-limiting resistor, utilizing the diode's voltage drop characteristics to clamp the high-voltage signal during transmission to a lower level, thereby protecting the subsequent amplification circuitry.

[0004] However, the aforementioned existing technical solutions have significant shortcomings when practically applied to high-power, high-voltage applications driving underwater acoustic transducers. RF switches are unable to withstand high voltage signals and are easily damaged; while PIN diodes can achieve a certain degree of high-voltage clamping, their voltage drop is typically only a few volts. High-voltage signals exceeding this voltage drop cannot be effectively isolated, easily generating severe electrical noise interference, affecting the normal operation of subsequent circuits at the transducer receiver, leading to reduced reliability of measurement results or even equipment damage. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the technical problem to be solved by this invention is to propose a transceiver method for an underwater acoustic transducer based on an optocoupler isolator, employing the following technical solution:

[0006] A transceiver method for an underwater acoustic transducer based on an optocoupler isolator is applied to a transceiver circuit of an underwater acoustic transducer. The circuit includes a power amplifier, an isolation module, an underwater acoustic transducer, a limiting protection module, and an amplification module connected in sequence. The isolation module includes an optocoupler isolator and a controlled switch. The optocoupler isolator receives a control signal and generates an electrical signal for driving the controlled switch to open and close.

[0007] The above sending and receiving methods include the following steps:

[0008] S10: Receive command signal and determine whether the above underwater acoustic transducer is in transmitting or receiving state;

[0009] S20: When the above-mentioned underwater acoustic transducer is in the transmitting state, perform the following steps:

[0010] S21: Issue the above control signal to drive the above optocoupler isolator to turn on, and the above optocoupler isolator drives the above controlled switch to turn on, so that the above power amplifier outputs an excitation signal to the above underwater acoustic transducer.

[0011] S22: The above-mentioned underwater acoustic transducer converts the above-mentioned excitation signal into an acoustic wave signal and emits it;

[0012] S30: When the above-mentioned underwater acoustic transducer is in the receiving state, perform the following steps:

[0013] S31: Issue the above control signal to drive the above optocoupler isolator to disconnect, so that the above power amplifier is electrically isolated from the underwater acoustic transducer;

[0014] S32: The above-mentioned underwater acoustic transducer receives external echo signals and converts them into analog signals;

[0015] S33: The analog signal is input to the amplification module via the amplitude limiting protection module. The amplification module amplifies the analog signal and outputs it to the signal acquisition unit.

[0016] As a further improvement, the controlled switch is an electromagnetic relay; in step S21, when the control signal is high, the optocoupler drives the electromagnetic relay to close, connecting the power amplifier to the transmission path; in step S31, when the control signal is low, the optocoupler disconnects.

[0017] Further improvements include a switching module connected between the isolation module and the underwater acoustic transducer. The switching module includes two sets of switching diodes respectively disposed on the positive and negative signal branches. Each switching diode set includes two diode branches connected in parallel with opposite polarities. In step S21, the voltage of the excitation signal is higher than the conduction threshold of the switching module, and the transmission signal is transmitted to the transducer. In step S32, the voltage of the analog signal is lower than the conduction threshold, and the switching diode sets are turned off.

[0018] As a further improvement, the aforementioned switching diode group is composed of 1N5408 type diodes.

[0019] As a further improvement, the above-mentioned limiting protection module includes a limiting diode group, which includes two diode branches with opposite polarities connected in parallel on the positive and negative branches of the signal, for limiting the voltage input to the above-mentioned amplification module within a preset voltage.

[0020] As a further improvement, the above-mentioned limiting protection module also includes a current-limiting resistor, which is connected between the underwater acoustic transducer and the limiting diode group.

[0021] As a further improvement, an indicator diode is connected in series at the input terminal of the aforementioned optocoupler isolator. When the optocoupler is turned on, the indicator diode lights up to indicate that it is in the emission state.

[0022] As a further improvement, the amplification module includes a first-stage amplification unit and a second-stage amplification unit. The first-stage amplification unit is connected to the output terminal of the limiting diode group and is used for impedance conversion from high impedance to low impedance. The second-stage amplification unit is disposed at the output terminal of the first-stage amplification unit and is used for signal amplification and signal noise reduction.

[0023] As a further improvement, the first-stage amplification unit includes an instrumentation amplifier of model AD8421 and its peripheral circuitry, with a gain of 10 and a common-mode rejection ratio of ≥100dB, used to convert high-impedance differential signals into low-impedance single-ended signals; the second-stage amplification unit includes an operational amplifier of model OP27 and its peripheral circuitry, with a gain of 10 and an input noise voltage peak-to-peak value of ≤80nV, used for signal amplification and reduction.

[0024] As a further improvement, the gain resistor of the first-stage amplifier unit is 1.1kΩ, and the feedback resistors of the second-stage amplifier unit are 10kΩ and 90kΩ, respectively.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] Firstly, this invention achieves dual isolation control between the power amplifier and the underwater acoustic transducer through the synergistic effect of the optocoupler isolator and the controlled switch in the isolation module. The optocoupler isolator uses optical signals for drive control, and the external control signal is completely electrically isolated from the high-voltage circuit, preventing electromagnetic interference from seeping into the low-voltage circuit. The controlled switch closes to conduct the high-voltage signal in the transmitting state and is physically disconnected in the receiving state, completely isolating the power amplifier and the receiving circuit, eliminating the risk of high-voltage leakage, and significantly improving the system's safety and anti-interference capability, making it particularly suitable for high-voltage drive scenarios for underwater acoustic transducers.

[0027] Secondly, the amplitude limiting protection module in this invention employs two sets of series diodes connected in reverse parallel to limit the voltage of the input amplification module within a safe range. This reverse parallel structure can simultaneously suppress both positive and negative transient overvoltages, preventing high-voltage surges from damaging the high-sensitivity amplification module. Furthermore, limiting the signal amplitude reduces nonlinear distortion and parasitic noise, significantly improving the signal-to-noise ratio of signal acquisition. During the transition between transmit and receive states, it rapidly absorbs residual high-voltage energy, ensuring the safety of the back-end circuitry and the reliability of subsequent signal processing.

[0028] Thirdly, in this invention, the amplification module achieves high-precision signal processing through the collaborative design of two-stage amplification units. Specifically, the first-stage instrumentation amplifier completes the impedance conversion from high-impedance to low-impedance signals, suppresses common-mode noise, and extracts weak acoustic signals; the second-stage precision operational amplifier further amplifies the signal. The switching module utilizes the conduction threshold characteristics of the diode group to conduct high-voltage signals in the transmitting state and cut off noise isolation in the receiving state, achieving seamless connection of the transmitting and receiving paths, realizing high-fidelity signal conversion, meeting the dual requirements of underwater acoustic transducers for weak signal detection and high-voltage drive, while also taking into account fast response and system stability. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a flowchart of the method of the present invention;

[0031] Figure 2 This is a schematic diagram of the overall structure of the application circuit of the present invention;

[0032] Figure 3 This is a schematic diagram of the circuit structure of the isolation module in this invention;

[0033] Figure 4This is a schematic diagram of the circuit structure of the switching module and the limiting protection module in this invention;

[0034] Figure 5 This is a schematic diagram of the circuit structure of the amplification module in this invention;

[0035] Figure 6 This is an experimental graph showing the input signal range and amplification factor according to an embodiment of the present invention;

[0036] Figure 7 This is an experimental chart showing the average amplification factor when the input signal is 50-150 kHz, according to an embodiment of the present invention.

[0037] Figure label:

[0038] 1-Power amplifier; 2-Isolation module; 3-Underwater acoustic transducer; 4-Limiting protection module; 5-Amplification module; 6-Switch module;

[0039] 41-Limiting diode group;

[0040] 51 - First stage amplification unit; 52 - Second stage amplification unit. Detailed Implementation

[0041] To facilitate understanding by those skilled in the art, the structure of the present invention will now be described in further detail with reference to the accompanying drawings:

[0042] In the description of this invention, the terms “part,” “side,” “end,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] like Figures 1-5 As shown, this application provides a transceiver method for an underwater acoustic transducer based on an optocoupler isolator, applied to a transceiver circuit of an underwater acoustic transducer. The circuit includes a power amplifier 1, an isolation module 2, an underwater acoustic transducer 3, a limiting protection module 4, and an amplification module 5 connected in sequence. Figure 2 As shown, power amplifier 1 converts the low-voltage input signal into an excitation signal. Its output is connected to underwater acoustic transducer 3 through positive and negative signal branches. Underwater acoustic transducer 3 is used to transmit and receive external acoustic signals. An isolation module 2 is provided between power amplifier 1 and underwater acoustic transducer 3. Underwater acoustic transducer 3 is connected to amplification module 5 through a limiting protection module 4 to amplify the signal and transmit it to subsequent signal acquisition equipment.

[0044] The sending and receiving method provided in this technical solution specifically includes the following steps:

[0045] S10: Receive command signal and determine whether the underwater acoustic transducer 3 is in the transmitting or receiving state;

[0046] S20: When the underwater acoustic transducer 3 is in the transmitting state, perform the following steps:

[0047] S21: Send a control signal to drive the optocoupler to turn on, and the optocoupler to drive the controlled switch to turn on, so that the power amplifier 1 outputs an excitation signal to the underwater acoustic transducer 3.

[0048] S22: The underwater acoustic transducer 3 converts the excitation signal into an acoustic wave signal and emits it;

[0049] S30: When the underwater acoustic transducer 3 is in the receiving state, perform the following steps:

[0050] S31: Send a control signal to drive the optocoupler isolator to disconnect, so that the power amplifier 1 is electrically isolated from the underwater acoustic transducer 3;

[0051] S32: The underwater acoustic transducer 3 receives external echo signals and converts them into analog signals;

[0052] S33: The analog signal is input to the amplification module 5 via the amplitude limiting protection module 4. The amplification module 5 amplifies the analog signal and outputs it to the signal acquisition unit.

[0053] like Figure 2 and Figure 3 As shown, the isolation module 2 includes an optocoupler isolator and a controlled switch. The optocoupler receives external control signals and generates electrical signals to drive the controlled switch to open and close. In the transmitting state, it is turned on, connecting the output signal of the power amplifier 1 to the underwater acoustic transducer 3; in the receiving state, it is turned off, achieving electrical isolation between the power amplifier 1 and the underwater acoustic transducer 3. Specifically, in step S21, when the control signal is high, the optocoupler drives the electromagnetic relay to close, connecting the power amplifier 1 to the transmitting path; in step S31, when the control signal is low, the optocoupler is turned off.

[0054] In one specific embodiment, the optocoupler isolator selected is the TLP521-1GB, which has a high current transfer ratio and high isolation withstand voltage performance, such as... Figure 3The optocouplers T1 and T2 shown have an input LED and an output phototransistor. When a high-level signal is applied to the control terminal, the LED conducts and emits a light signal. The phototransistor receives this light signal and then conducts, generating a drive current on the output side to trigger the controlled switch. The TLP521-1GB has a minimum input-to-output isolation voltage of 5300VRMS and a current transfer ratio range of 50% to 200%, ensuring stable and sufficient drive current even under low LED drive current conditions. Its rise and fall times are approximately 4μs and 3μs, respectively, adapting to higher voltage fluctuations in underwater acoustic transducer systems, ensuring safe isolation between the low-voltage control terminal and the high-voltage drive terminal, and meeting the requirements for rapid switching between transmit and receive states in underwater acoustic transducers.

[0055] Furthermore, such as Figure 3 As shown, an indicator diode is connected in series at the input terminal of the optocoupler isolator. When the optocoupler is in the conducting state, the indicator diode emits light to indicate the working status of the corresponding path, which is convenient for actual debugging and monitoring.

[0056] like Figure 3 In the above embodiment, the controlled switches K1 and K2 are electromagnetic relays of model HF32F / 005-HS. Specifically, they are single-pole single-throw structures with a rated voltage of 250VAC or 30VDC, a rated current of 10A, a pull-in time of 8ms, and a release time of 5ms, ensuring stable operation under high-power signal drive conditions and meeting the electrical connection requirements of the underwater acoustic transducer 3 in the transmitting state. When the phototransistor at the output of the optocoupler is turned on, sufficient drive current is provided to the electromagnetic relay coil, the relay contacts close, and conduction is achieved between the power amplifier 1 and the underwater acoustic transducer 3. When the control signal is canceled or at a low level, the optocoupler is disconnected, the electromagnetic relay loses its drive current and releases, the contacts open, and the power amplifier 1 and the underwater acoustic transducer 3 are completely isolated, ensuring that high voltage does not leak to the subsequent receiving circuit, improving system safety and anti-interference level.

[0057] In the above embodiments, the isolation module 2 combines an optocoupler with a controlled switch to achieve electrical isolation between low and high voltage using optical signals, while simultaneously utilizing the high load capacity of an electromagnetic relay for physical switching, thus forming a high-speed, stable, and dual-isolated switch control loop. For high-power transmission scenarios of underwater acoustic transducers, this module can effectively prevent high-voltage signals from interfering with weak receivers, improving system safety and overall performance.

[0058] like Figure 2 and Figure 4As shown, the limiting protection module 4 is connected between the underwater acoustic transducer 3 and the amplification module 5, and is used to limit the acoustic signal to protect the amplification module 5. The limiting diode group 41 includes two diode branches with opposite polarities connected in parallel on the positive and negative branches of the signal, and is used to limit the voltage of the input amplification module 5 within a preset voltage.

[0059] In one specific embodiment, a current-limiting resistor is connected between the underwater acoustic transducer 3 and the limiting diode group 41 to limit the current in the receiving path. Because the underwater acoustic transducer 3 has a low internal resistance, high-voltage transients may cause excessive current, and the current-limiting resistor can effectively reduce the current amplitude flowing through subsequent circuits, ensuring the safety of the entire circuit. Preferably, as... Figure 4 As shown, the current-limiting resistors are resistors R1 and R2, with a resistance of 10KΩ. The resistance of the current-limiting resistors must be much larger than the internal resistance of the transducer so that most of the current is limited in the receiving state, allowing small signals to pass through without overload. At the same time, the resistance must match the operating bandwidth of the system and the high-voltage transmission requirements, balancing current limiting protection and signal attenuation.

[0060] Furthermore, such as Figure 4 As shown, diodes D9-D16 form the limiting diode group 41, where the diode branch consisting of D9-D12 connected in series is connected in parallel with the diode branch consisting of D13-D16 connected in series, and their polarities are opposite. The diodes in the limiting protection module 4 are model 1N4148, with a maximum reverse withstand voltage of 100V, a forward voltage drop of approximately 0.6V, and an average rectified current of 150mA. They have moderate reverse withstand voltage and low forward voltage drop, allowing for rapid response and interruption of large voltages. The limiting voltage of diode group B is approximately 2.4V. When the input signal amplitude exceeds the total conduction voltage of the diodes, the diodes quickly conduct and clamp the voltage, ensuring that the amplification module 5 at the output terminal is always within the preset voltage. In the above embodiment, the preset voltage is 1V.

[0061] like Figure 4 As shown, it also includes a switching module 6, connected between the isolation module 2 and the underwater acoustic transducer 3. The switching module 6 includes two sets of switching diodes respectively disposed on the positive and negative signal branches. Each switching diode set includes two parallel diode branches with opposite polarities, such as... Figure 4As shown, diodes D1 and D2 connected in series form a diode branch connected in parallel with diodes D3 and D4 connected in series. In step S21, the voltage of the excitation signal is higher than the conduction threshold of the switching module 6, transmitting the transmission signal to the transducer. In step S32, the voltage of the analog signal is lower than the conduction threshold, and the switching diode group is turned off. The diode group is on in the transmission state and off in the receiving state. Preferably, the diodes in the switching module 6 are 1N5408, with a maximum reverse withstand voltage of up to 1000V, enabling stable operation under high voltage conditions and ensuring that the circuit is not damaged when the power amplifier outputs the transmission signal; the forward voltage drop is 1V, resulting in low circuit power consumption; and the average rectified current is 3A, allowing it to withstand large current surges.

[0062] like Figure 2 and Figure 5 As shown, the amplification module 5 is located at the rear end of the underwater acoustic transducer 3, and is used to amplify the acoustic signal received from the underwater acoustic transducer 3 and output it to the subsequent signal acquisition equipment. The amplification module 5 includes a first-stage amplification unit 51 and a second-stage amplification unit 52. The first-stage amplification unit 51 is connected to the output terminal of the limiting diode group 41 and is used for impedance conversion from high impedance to low impedance. The second-stage amplification unit 52 is located at the output terminal of the first-stage amplification unit 51 and is used for signal amplification and signal noise reduction.

[0063] In one specific embodiment, the first-stage amplification unit 51 includes an instrumentation amplifier of model AD8421 and its peripheral circuits. The instrumentation amplifier AD8421 has high common-mode rejection performance, with a common-mode rejection ratio ≥100dB. It is suitable for extracting weak differential signals with high impedance in the receiving end of the underwater acoustic transducer 3, and can significantly suppress common-mode interference voltage and improve the differential signal extraction accuracy. The second-stage amplification unit 52 includes an operational amplifier of model OP27 and its peripheral circuits, with a gain of 10 times and an input noise voltage peak-to-peak value ≤80nV.

[0064] In the above embodiment, the instrumentation amplifier AD8421 is used to convert high-impedance signals into low-impedance signals to reduce the influence of external interference on the signal. Figure 5 In the embodiment shown, the gain resistor R4 = 1.1kΩ, and when the gain is set to 10 times, the common-mode rejection ratio reaches 104dB, which effectively suppresses common-mode noise in the signal and improves signal quality. The power supply rejection ratio is greater than 110dB, which effectively reduces the interference of power supply noise on the signal.

[0065] In the above embodiment, after the output from the instrumentation amplifier AD8421, the operational amplifier OP27 is used to further amplify the signal. The OP27 series operational amplifiers have low noise, high accuracy, a maximum offset voltage of 10μV, an input noise voltage peak-to-peak value of no more than 80nV, and good load driving capability. Preferably, the gain of the operational amplifier OP27 is set to 10 times. Figure 5 As shown, by setting two feedback resistors R9=10kΩ and R10=90kΩ, the signal is further amplified and the input requirements of the subsequent acquisition card are met.

[0066] The technical effects of this solution are illustrated below with practical applications and application data:

[0067] To reduce external noise interference such as power supply noise and electromagnetic interference at the input, the circuit input is short-circuited. The impact of internal noise on the output is measured. Therefore, zero-input equivalent noise is used to measure the circuit's noise level. The calculation formula is as follows:

[0068] ;

[0069] Among them, V N With zero input equivalent noise, V E The output noise is the effective value, and Gain is the circuit gain. The circuit gain is fixed, and A is the circuit amplification factor. The ideal amplification factor is 100 times, which means the gain is 40dB.

[0070] In a test of this technical solution, when there was no input signal, the effective value V of the circuit output signal was... E The equivalent noise V at zero input is 1.2mV. N The voltage is 0.03mV, which meets the low noise requirements of the circuit design and achieves the expected design goal.

[0071] Using a sine wave as the input signal, the output signal corresponding to the input signal of 30~110mV and the output signal corresponding to the minimum input signal of 20mV without waveform distortion were measured at 20mV intervals. The frequency range of the measurement was 50~150kHz, with an interval of 20kHz.

[0072] like Figure 6 As shown, when the input signal frequency is 50~110kHz, the output waveform is normal when the peak-to-peak value of the input signal is within 20~90mV, and the amplification factor ranges from 95.11 to 104. When the peak-to-peak value of the input signal exceeds 90mV, the output waveform is distorted into a triangular wave and clipping occurs, with the amplification factor dropping sharply to 78. For input signals with frequencies between 110~150kHz, when the peak-to-peak value is between 20~70mV, the amplification factor ranges from 90~102. When the peak-to-peak value of the input signal exceeds 70mV, the amplification factor decreases as the peak-to-peak value of the input signal increases, gradually falling below 90.

[0073] For input signals with a frequency range of 50~110kHz and a peak-to-peak value range of 20~90mV; and a frequency range of 110~150kHz and a peak-to-peak value range of 20~70mV, calculate the average signal amplification factor at each frequency. Figure 7As shown, the average amplification factor ranges from 97.85 to 101.5, with an error within 2.12, and the output waveforms show no distortion, meeting the design requirements for amplification factor.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A transceiver method for an underwater acoustic transducer based on an optocoupler isolator, characterized in that, A transceiver circuit for use in underwater acoustic transducers includes a power amplifier, an isolation module, an underwater acoustic transducer, a limiting protection module, and an amplification module connected in sequence. The isolation module includes an optocoupler isolator and a controlled switch. The optocoupler isolator receives a control signal and generates an electrical signal to drive the controlled switch to open and close. The sending and receiving method includes the following steps: S10: Receive command signal and determine whether the underwater acoustic transducer is in transmitting or receiving state; S20: When the underwater acoustic transducer is in the transmitting state, the following steps are performed: S21: The control signal is issued to drive the optocoupler to turn on, and the optocoupler drives the controlled switch to turn on, so that the power amplifier outputs an excitation signal to the underwater acoustic transducer; S22: The underwater acoustic transducer converts the excitation signal into an acoustic wave signal and emits it; S30: When the underwater acoustic transducer is in the receiving state, the following steps are performed: S31: Issue the control signal to drive the optocoupler to disconnect, so that the power amplifier is electrically isolated from the underwater acoustic transducer; S32: The underwater acoustic transducer receives external echo signals and converts them into analog signals; S33: The analog signal is input to the amplification module via the amplitude limiting protection module, and the amplification module amplifies the analog signal and outputs it to the signal acquisition unit; The limiting protection module includes a limiting diode group, which includes two diode branches with opposite polarities connected in parallel on the positive and negative branches of the signal, used to limit the voltage input to the amplification module within a preset voltage. The amplification module includes a first-stage amplification unit and a second-stage amplification unit. The first-stage amplification unit is connected to the output terminal of the limiting diode group and is used for impedance conversion from high impedance to low impedance. The second-stage amplification unit is disposed at the output terminal of the first-stage amplification unit and is used for signal amplification and signal noise reduction.

2. The method of claim 1, wherein the method further comprises: The controlled switch is an electromagnetic relay; in step S21, the control signal is high level, the optocoupler drives the electromagnetic relay to close, and connects the power amplifier to the transmission path; in step S31, the control signal is low level, and the optocoupler is disconnected.

3. The method of claim 2, wherein the method further comprises: It also includes a switching module connected between the isolation module and the underwater acoustic transducer. The switching module includes two sets of switching diodes respectively disposed on the positive and negative signal branches. The switching diodes include two diode branches connected in parallel with opposite polarities. In step S21, the voltage of the excitation signal is higher than the conduction threshold of the switching module, and the transmission signal is transmitted to the transducer. In step S32, the voltage of the analog signal is lower than the conduction threshold, and the switching diodes are turned off.

4. The method of claim 3, wherein the method further comprises: The switching diode group consists of 1N5408 type diodes.

5. The method of claim 1, wherein the method further comprises: transmitting a signal from the transducer to the receiver through the optical coupling isolator. The amplitude limiting protection module also includes a current limiting resistor, which is connected between the underwater acoustic transducer and the amplitude limiting diode group. ​ 6. The method of claim 1, wherein the method further comprises: An indicator diode is connected in series at the input terminal of the optocoupler isolator. When the optocoupler is turned on, the indicator diode lights up to indicate that it is in the emission state.

7. The method of claim 1, wherein the method further comprises: transmitting a signal from the transducer to the receiver through the optical coupling isolator. The first-stage amplification unit includes an AD8421 instrumentation amplifier and its peripheral circuitry, with a gain of 10 and a common-mode rejection ratio of ≥100dB, used to convert high-impedance differential signals into low-impedance single-ended signals; the second-stage amplification unit includes an OP27 operational amplifier and its peripheral circuitry, with a gain of 10 and an input noise voltage peak-to-peak value of ≤80nV, used for signal amplification and noise reduction. ​ 8. The method of claim 7, wherein the method further comprises: The gain resistor of the first-stage amplifier unit is 1.1kΩ, and the feedback resistors of the second-stage amplifier unit are 10kΩ and 90kΩ, respectively.

Images