A densely populated MIMO sonar transmitting system and transmitting method

Abstract

The application designs a densely arranged MIMO sonar transmitting system and transmitting method, which can realize synchronous transmission of orthogonal waveform signals of maximum 5 channels; the application adopts a high-low voltage power supply unified management scheme, reduces useless power consumption, and increases power supply reliability of a wet end of the transmitting system; the application adopts a modular design of an isolation structure, physically isolates a signal source module, a driving module and a power amplifier module, reduces influence between front and rear modules while ensuring high-power transmission, reduces interference between channels, and increases system maintainability.

Description

Technical Field

[0001] This invention belongs to the field of underwater detection technology, and specifically relates to a densely distributed MIMO sonar transmission system and transmission method. Background Technology

[0002] Because MIMO technology can effectively suppress multipath fading and increase system physical capacity without increasing bandwidth and transmit power, it has been widely used in the fields of communication and radar since the 1990s. Generally speaking, MIMO systems can be divided into two main categories: one is distributed MIMO systems, where the transmitting and receiving units are distributed, and the distance between each unit is comparable to its distance from the target. The transmitted and received signals are uncorrelated, and the diversity of the system is used to improve the target detection performance. The other is dense MIMO systems, where the transmitting and receiving units are closer together, and the distance between them is comparable to the signal wavelength. Each unit transmits a different signal waveform, thereby obtaining waveform diversity, and the characteristics of the target are analyzed by focusing on the characteristics of different waveforms.

[0003] With the development of MIMO systems, sonar researchers have also begun studying MIMO sonar. Because distributed MIMO sonar is similar to multistatic sonar, it is more flexible in form and more complex, thus still has a long development process before practical application. In comparison, densely distributed MIMO sonar has a compact arrangement of transceiver units, higher system integration, and is easier to implement. It also allows for in-depth research by fully utilizing existing sonar system transmission beam pattern design, matched filtering, and other processing methods.

[0004] Dense MIMO sonar is essentially a type of active sonar. Because each transmitting unit emits an independent signal, it cannot form a coherent beam at the transmitting end, resulting in a loss of transmit array gain. Compared to traditional active sonar, the latter can achieve higher coherent processing gain, thus obtaining a higher detection probability. However, the former can compensate for this deficiency by accumulating long pulses, achieving the same detection performance. As a type of active sonar, its detection range is also affected by the source level. A high source level means high power output. Therefore, an excellent dense MIMO sonar transmitting system must first have the ability to transmit long pulses and high-power signals, which places higher demands on the stability and reliability of the transmitting system. Meanwhile, densely distributed MIMO sonar transmission systems require that the transmitted waveforms of each transmitting unit have good orthogonality. Generally, the transmission bandwidth of each transmitting unit is different, and the transmitting transducers of each transmitting unit are also different, with different resonant frequencies. Therefore, each transmitting transducer needs to be matched separately. At present, most transmission systems mainly use Class A or Class AB power amplifier circuits as the core, and achieve optimal driving of the transmitting transducers through matching networks. Its advantages are low waveform distortion, but it has a large size and low power density. If a densely distributed MIMO sonar transmission system is built on this basis, the system size will be too large and the power utilization efficiency will be too low.

[0005] In summary, the transmission system of densely distributed MIMO sonar needs to have the ability to transmit long pulses, high power, small size, and multi-channel synchronous orthogonal waveforms, which existing traditional sonar systems cannot meet. Summary of the Invention

[0006] The technical problem solved by this invention is that existing sonar systems cannot meet the requirements of high-power, multi-channel, synchronous orthogonal waveform transmission in actual MIMO sonar detection. This invention specifically designs a MIMO sonar transmission system with a smaller volume. This invention can realize synchronous transmission of multi-channel orthogonal waveforms of MIMO sonar. At the same time, in order to meet the requirements of long pulse high-power signal transmission, a modular design with an isolation structure is adopted to improve the reliability and maintainability of the entire MIMO sonar transmission system, enabling it to work stably underwater for a long time.

[0007] The technical solution of the present invention is: a dense MIMO sonar transmission system, including a dry end component and a wet end component, wherein the dry end component is located above the sea level and the wet end component is located below the sea level, and the dry end component and the wet end component are connected by a cable;

[0008] The dry-end component includes a power management module and a display control module, wherein the power management module is used for the overall power supply of the dense MIMO sonar transmission system, and the display control module is used for the human-computer interaction of the dense MIMO sonar transmission system.

[0009] The wet-end assembly is used for synchronous pulse transmission of high-power, multi-channel orthogonal waveform signals. The wet-end assembly includes a transmission system monitoring module, a signal source module, a signal drive module, a power amplifier module, an impedance matching module, and a transmitting transducer. The signals between the signal source module, the signal drive module, and the power amplifier module are transmitted in isolation, and channel-to-channel signal isolation is achieved in the signal drive module and the power amplifier module. The power supply of each sub-module of the wet-end assembly is uniformly allocated through the transmission system monitoring module to achieve power isolation between modules.

[0010] A further technical solution of the present invention is: the wet end assembly further includes a wet end housing and a watertight connector. The wet end housing is arranged from top to bottom as follows: a cable watertight connector, a transmission system monitoring module, a signal source module, a signal driving module, a power amplifier module, an impedance matching module, and a high-voltage watertight connector for the transmitter transducer; wherein the cable watertight connector is used to connect with the cable, and the high-voltage watertight connector for the transmitter transducer is used to connect with the transmitter transducer.

[0011] A further technical solution of the present invention is: the transmission system monitoring module includes a temperature sensor, a Hall sensor, a photoelectric sensor and a DC relay. The temperature sensor and the Hall sensor collect temperature data and current data of the transmission channel, and the photoelectric sensor and the DC relay realize power control of the transmission channel.

[0012] A further technical solution of the present invention is: aluminum plates are respectively assembled below the power amplifier module, and high-power devices are assembled on the aluminum plates by means of alumina ceramic sheets.

[0013] A further technical solution of the present invention is as follows: the signal driving module includes a two-stage isolation amplification structure, wherein the first-stage isolation amplification structure uses an isolation operational amplifier to amplify the signal, thereby achieving signal isolation between the signal source module and the signal driving module; the second-stage isolation amplification structure uses an isolation transformer to amplify the signal, thereby achieving signal isolation between the signal driving module and the power amplifier module, and the output signal of the transformer is used to drive the power amplifier module, while the transformer is used to achieve drive signal isolation between channels.

[0014] A further technical solution of the present invention is: the power amplifier module adopts a Class D power amplifier scheme, and uses a single-ended push-pull full-bridge power amplifier circuit composed of high-power MOSFETs to realize the power amplification of the signal, with each bridge arm using two MOSFETs connected in parallel.

[0015] A further technical solution of the present invention is as follows: the impedance matching module adopts a series resonant circuit, and nanocrystals are selected as the core material of the transformer; an integrated packaging scheme for the transformer and inductor is adopted, in which the transformer and inductor are encapsulated in an epoxy resin package, and the inductor and the secondary coil of the transformer are formed by a single enameled wire wound without interruption inside the package; the turns ratio of the transformer, the inductance value of the resonant inductor, and the magnitude of the resonant inductor in the impedance matching module are determined according to the resonant frequency of the transmitting transducer and the output power of the power amplifier.

[0016] A further technical solution of the present invention is: the transmitting transducer is a plurality of bending transducers, which are formed into a circle, wherein a bending transducer is provided at the center of the circle, and the other bending transducers are evenly arranged on a circular array frame with a radius of R. The transmitting transducers are flexibly connected to the array frame using springs to form a transmitting array. The size of the transmitting array is adjusted by adjusting the radius R.

[0017] A further technical solution of the present invention is: a method for transmitting a sonar system, characterized by comprising the following steps:

[0018] Step 1: Power the dense MIMO sonar transmitting system using marine batteries / storage batteries. The power management module performs step-down isolation conversion. The industrial control computer is powered on, and the display and control module program runs. It detects the voltage and power of the power supply. When the voltage is normal, the relay closes and performs step-up isolation conversion to power the wet-end components through the cable. When undervoltage or overvoltage occurs, the display and control module alarms and the relay opens.

[0019] Step 2: After the wet end component is powered on, the transmission system monitoring module starts working, the signal source module and the signal drive module are powered on first, and the temperature sensor and the current sensor start working.

[0020] Step 3: Select the transmission channel of the transmission system in the human-computer interaction software, set the signal frequency, signal pulse width, signal period and transmission power of each channel, and send the command to the wet end component through the RS485 bus;

[0021] Step 4: After receiving the command, the signal source module parses the transmission channel number, signal frequency, signal pulse width, signal period, and transmission power according to the protocol. The relay of the corresponding channel closes, the power amplifier module is powered on, and the signal source module generates the corresponding synchronous quadrature waveform signal. After isolation driving, the power is amplified in the power amplifier module of the corresponding channel. Then, through the corresponding impedance matching network, the signal is loaded onto the corresponding transmitting transducer. Finally, the transmitting transducer radiates the signal into the water.

[0022] Step 5: Obtain the temperature and current status of the transmitter through temperature and current sensors, and upload the status information through RS485 bus. Display the information in the human-machine interface software. When a channel experiences an abnormal status, the protection mechanism is activated, the signal source module stops the signal output of that channel, the power amplifier module of the corresponding channel is powered off, and an alarm is triggered in the human-machine interface software.

[0023] Step 6: Once the transmission system is operational, use the human-machine interface software to power off all channel power amplifier modules, disconnect the dry-end relays, and power off the wet-end. If necessary, logs containing transmission location information, transmission time information, transmission signal parameters, and transmitter status can be sent to other users via the network connector. Finally, shut down the industrial control unit and disconnect the power supply to the dense MIMO sonar transmission system.

[0024] A further technical solution of the present invention is: when the human-computer interaction software is working, it records the current launch information, including launch location information, launch time information, launch signal parameters, and transmitter status, and generates a test log file. The software generates a test log file each time it runs. Historical launch information can be viewed through the test log, and the test log can be sent and shared with other users through a network connector.

[0025] Invention Effects

[0026] The technical advantages of this invention are as follows: This invention designs a densely distributed MIMO sonar transmission system and transmission method, which can realize the synchronous transmission of orthogonal waveform signals from up to 5 channels, with a maximum pulse output power of not less than 800W and a maximum sound source level of not less than 190dB per channel; This invention adopts a unified high and low voltage power supply management scheme to reduce useless power consumption and increase the reliability of the wet-end power supply of the transmission system; This invention adopts a modular design with an isolated structure to physically isolate the signal source module, signal drive module, and power amplifier module, which reduces the influence between the front and rear modules and the interference between channels while ensuring high-power transmission, and at the same time increases the maintainability of the system. Attached Figure Description

[0027] Figure 1 Design a block diagram for the system

[0028] Figure 2 Design a block diagram for the dry-end system

[0029] Figure 3 Schematic diagram of wet end structure

[0030] Figure 4 Design block diagram for wet-end system

[0031] Figure 5 Schematic diagram of the transmitter transducer array

[0032] Figure 6 For launch system information feedback interface

[0033] Figure 7 Transmitter parameter setting interface

[0034] Figure 8 Transmitter status display interface

[0035] Figure 9 For the launch system test log interface

[0036] Figure 10 Schematic diagram of the test plan

[0037] Figures 11-15 The figures show the signal waveforms at both ends of the five transmitting transducers when they are operating within their respective frequency bands. Figure 11 (a) is the signal transmitted by transducer 1. Figure 11 (b) The signal transmitted by transducer 1 is displayed; Figure 12 (a) is the signal transmitted by transducer 2. Figure 12 (b) The signal transmitted by transducer 2 is displayed; Figure 13 (a) is the signal transmitted by transducer 3. Figure 13 (b) The signal transmission of the transmitting transducer 3 is unfolded; Figure 14 (a) is the signal transmitted by transducer 4. Figure 14 (b) The signal transmission of transducer 4 is deployed; Figure 15 (a) is the signal transmitted by transducer 5. Figure 15 (b) Deploying the signal transmitted by transducer 5

[0038] Figures 16-20 The waveforms of the signals received by a standard hydrophone are shown for each of the five transmitting transducers operating within their respective frequency bands. Figure 16 (a) is the standard hydrophone receiving signal 1. Figure 16 (b) The standard hydrophone receives signal 1; Figure 17 (a) is the standard hydrophone receiving signal 2. Figure 17 (b) The standard hydrophone receives signal 2; Figure 18 (a) is the standard hydrophone receiving signal 3. Figure 18 (b) The standard hydrophone receives signal 3; Figure 19 (a) is the standard hydrophone receiving signal 4. Figure 19 (b) The standard hydrophone receives signal 4; Figure 20 (a) is the standard hydrophone receiving signal 5. Figure 20 (b) Expanding the standard hydrophone reception signal 5

[0039] Explanation of reference numerals in the attached diagram: 1-Wet end housing; 2-Watertight cable connector; 3-Transmitting system monitoring module; 4-Signal source module; 5-Signal drive module; 6-Amplifier module; 7-Impedance matching module; 8-Transmitting transducer high-voltage watertight connector Detailed Implementation

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not 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.

[0041] See Figures 1-20 This invention designs a densely distributed MIMO sonar transmission system capable of synchronous transmission of up to five channels of orthogonal waveforms, with a maximum pulse output power of no less than 800W per channel. The system mainly consists of two parts: a dry end and a wet end, connected by cables. The dry end includes a power management module and a display control module, responsible for the overall power supply of the densely distributed MIMO sonar transmission system and the system's human-machine interface. The wet end includes a transmission system monitoring module, a signal source module, a signal drive module, a power amplifier module, an impedance matching module, and a transmitting transducer, responsible for the synchronous pulse transmission of high-power, multi-channel orthogonal waveforms. The system design block diagram is shown below. Figure 1 As shown.

[0042] The specific functions of each module in the dry section are as follows:

[0043] Power management module: responsible for filtering the input power supply, isolating and converting the high and low voltage power supply, the low voltage power supply supplies power to the display control module, and the high voltage power supply supplies power to the wet end through the cable;

[0044] Display control module: responsible for controlling the power-on startup of the wet end, setting the transmission parameters of each channel of the transmission system, and displaying the transmission status of each transmission channel of the wet end;

[0045] The wet-end section adopts a modular design with an isolated structure, ensuring isolated signal transmission between the signal source module, signal driver module, and power amplifier module. Simultaneously, the power supply to each module in the wet-end section is uniformly allocated through the transmitting system monitoring module, achieving isolated power supply between modules. The advantages of this design are that each channel and module is independent, reducing interference between channels and between upstream and downstream stages of the system during high-power operation. Maintenance allows for independent inspection and replacement. The specific functions of each module are as follows:

[0046] The launch system monitoring module is responsible for monitoring the temperature and current status of each launch channel, as well as controlling and distributing power to each module at the wet end.

[0047] Signal source module: According to the transmission signal parameters of each channel sent by the display and control system, it generates corresponding multi-channel, synchronous orthogonal waveform signals. At the same time, it judges whether there is any abnormality in the transmission status of each channel. If an abnormality occurs, it triggers the protection mechanism to prevent the power amplifier module from being damaged due to overcurrent or overheating when transmitting high-power, long-pulse signals. It also sends the status data of each transmission channel at the wet end back to the display and control system.

[0048] Signal drive module: responsible for isolating and amplifying the orthogonal waveform signals generated by the front-end signal source module, so that it can drive the back-end power amplifier module;

[0049] Power amplifier module: It consists of 5 independent Class D power amplifier modules, which are responsible for amplifying the orthogonal waveform signals of each channel. Each power amplifier module is powered independently, and the input signals are isolated from each other and can be controlled individually.

[0050] Impedance matching module: Composed of 5 sets of inductors and transformers, responsible for high voltage conversion of signals. The parameters of each inductor and transformer are designed to match the parameters and transmission power of the corresponding transmitting transducer to ensure that they resonate in their respective frequency ranges and obtain the best transmission waveform.

[0051] Transmitting transducer: It consists of 5 bending transducers with different operating bandwidths and resonant frequencies, which convert electrical signals into acoustic signals and radiate them in various directions underwater.

[0052] To better understand this invention, the following examples further illustrate the invention and provide a detailed description of the technical solutions.

[0053] This invention comprises an upper dry end (above water portion) and a lower wet end (underwater portion), connected by a cable. The dry end consists of a power management module and a display control module, as shown in the system design block diagram. Figure 2 As shown.

[0054] The power management module is responsible for the power distribution of the entire system. Since the power supply of the dense MIMO sonar transmitting system mainly comes from the ship's power supply or batteries, in order to reduce interference and voltage fluctuations at the input end, the input power supply needs to be isolated and regulated twice. On the one hand, it performs step-down isolation conversion, providing +24VDC1 (20W power) to power the industrial control computer, +24VDC2 (40W power) to power the Beidou positioning system, +12VDC1 (1W power) to power the voltage and power acquisition module, +12VDC2 (20W) to power the relay module, and +5VDC (3W) to power the network connector. On the other hand, it performs step-up isolation conversion. In order to reduce cable losses, high-voltage DC transmission is used to increase the input DC power supply voltage to 350VDC. The cable impedance is about 0.03 ohms / m. The maximum total output power of the transmitting system is about 4kW. The overall efficiency of the transmitting system is calculated as 80% (the actual efficiency is not less than 80%). The minimum input voltage at the wet end is 200VDC, so the maximum supported cable length is about 100m. The design of isolating high and low voltage power supplies can effectively reduce the impact of surge current and peak voltage on the low voltage power supply at the dry end during high-power transmission, thereby increasing the power supply reliability of the system.

[0055] The core of the display control module is an industrial computer, characterized by its small size, low power consumption, robust shock resistance, and resistance to high and low temperatures, making it more suitable for industrial applications. The main functions of the display control module include: 1) Monitoring the power supply voltage of the densely distributed MIMO sonar transmitting system via a voltage sensor; 2) Displaying the input voltage and power status, and judging whether there are abnormal conditions such as undervoltage or overvoltage at the power supply end based on the monitored values. In case of abnormality, it promptly disconnects the relay to cut off the power supply to the wet-end, preventing damage caused by the wet-end failing to start normally; 3) Setting transmission signal parameters, including signal frequency, signal pulse width, signal period, transmission power, and transmission channels, according to changes in the usage scenario; 4) Displaying the temperature and current status of each channel based on feedback information from the wet-end; 5) Displaying the current time and location information, and transmitting data with multiple systems via a network connector.

[0056] The display control module adopts LabWindows / CVI design to realize human-computer interaction functions, thereby achieving integrated display and control of the densely distributed MIMO sonar transmission system. The implementation steps of its display control module are as follows:

[0057] Step 1: The module starts running and obtains the voltage and power of the power supply terminal from the voltage and power acquisition module via the RS232 bus. The voltage value is displayed on the interface. When the voltage V meets the condition of 42V < V < 56V, the relay is allowed to close and the wet terminal is powered on. When V ≤ 42V or V ≥ 56V, the system prompts that the power supply terminal is undervoltage or overvoltage, disconnects the relay, cuts off the power supply to the wet terminal, and prohibits the user from closing the relay to prevent the user from forcibly powering on the wet terminal and causing damage to the system.

[0058] Step 2: The software obtains the launch location information (latitude and longitude information) and launch time information from the BeiDou positioning system via the RS232 bus, and displays the launch system information feedback interface. Figure 6 As shown.

[0059] Step 3: After the wet end is powered on normally, the user can set the transmission channel, signal frequency, signal pulse width, signal period, and transmission power of the transmission system through the parameter setting interface. The parameter setting interface is as follows: Figure 7 As shown, the parameters set include transmission period, pulse form, pulse width selection, channel selection, and power selection. In this embodiment, the transmission period parameter selection includes 30s and 60s, ...; In CW mode, the transmission signal form of the 5 transmission channels is CW signal, and the signal frequency of each channel is 1550Hz, 1650Hz, 1750Hz, 1850Hz, and 1950Hz, respectively; In LFM mode, the transmission signal form of the 5 transmission channels is LFM signal, and the signal bandwidth of each channel is 1500-1600Hz, 1600-1700Hz, 1700-1800Hz, 1800-1900Hz, and 1900-2000Hz, respectively. The command is sent to the wet end via the RS485 bus. Based on the command reply from the wet end, it is determined whether the transmission parameters are set successfully. If the parameters are set successfully, the parameter setting indicator light is green; if the parameters are set unsuccessfully, the parameter setting indicator light is red.

[0060] Step 4: After the transmission system parameters are successfully set, the software can receive the transmitter status information uploaded by the wet end via the RS485 bus during each transmission cycle. The transmitter status display interface is as follows: Figure 8 As shown, the left side displays the current status of each channel of the transmitter. When the current status is normal, the current status indicator light of the corresponding channel is green. When the current status of a channel is abnormal, the current status indicator light of the corresponding channel is red. The right side displays the temperature status of each channel of the transmitter. The software uses a color bar + numerical value method for display, which is more intuitive. The temperature value changes color according to the level corresponding to the value range it falls into. The color bar changes from green to red as the temperature value increases. When the temperature is greater than 50 degrees, the software will issue an over-temperature warning.

[0061] Step 5: While the launch system is operating, the software records the current launch information, including launch location information, launch time information, launch signal parameters, and transmitter status, generating a test log file. The software generates one test log file each time it runs. The launch system test log interface is shown below. Figure 9 As shown, historical launch information can be viewed through the test logs, and the test logs can be shared with other users through the network connector.

[0062] The key to a densely packed MIMO sonar transmission system lies in the wet end, and a schematic diagram of the wet end structure of this invention is shown below. Figure 3 As shown: 1 is the housing of the wet end, which is a cylindrical pressure-resistant housing with an inner diameter D of approximately 300mm. Due to prolonged operation in seawater, to reduce the weight of the wet end, decrease the load on the cable, and increase the corrosion resistance of the housing, this invention uses titanium alloy as the housing material. The internal structure from top to bottom is as follows: 2-cable watertight connection device, 3-transmission system monitoring module, 4-signal source module, 5-signal drive module, 6-5 power amplifier modules, 7-5 impedance matching modules, and 8-5 high-voltage watertight connectors for the transmitter transducer. Among them, 6 and 7 are connected by 5 sets of M8 hexagonal stainless steel studs, 6 studs per set, and 3, 4, and 5 are connected by 4 sets of M4 hexagonal stainless steel studs, 4 studs per set. The height H of the entire wet end is approximately: h1 + h2 + h3 = 500mm, and the total weight (excluding the titanium alloy pressure-resistant housing) is approximately 25.3kg. To improve the heat dissipation of the power amplifier, each amplifier module is fitted with a 5mm thick aluminum plate at the bottom for heat dissipation. High-power components are mounted on the aluminum plate using alumina ceramic sheets. The alumina ceramic sheets have a thermal conductivity of 29.3W / mk and an insulation coefficient of 22.5kV / mm, ensuring insulation while enabling better heat dissipation for the power amplifier module. Five bending transducers are connected to the densely distributed MIMO sonar transmission system via a connector (8). Due to the high-voltage transmission, the connector in connector (8) has an insulation withstand voltage of no less than 5000VAC.

[0063] In the transmission system monitoring module, power control is primarily implemented through multiple isolated voltage conversion chips. These chips convert high voltage into the voltages required by each module, providing +5.0VCC and +3.3VCC to the signal source module and its own monitoring module, +5.0VDC and ±12VDC to the signal drive module, and five ±48VDD channels to power the five power amplifier modules. The +5.0VCC, +3.3VCC, +5VDC, ±12VDC, and ±48VDD power systems are mutually isolated and do not supply ground to each other. The system monitoring function primarily uses five temperature sensors and five Hall effect sensors to collect temperature and current data from the five transmission channels. Then, five photoelectric sensors and DC relays are used to control the five transmission channels. The wet-end system design block diagram is shown below. Figure 4 As shown.

[0064] The signal source module adopts an ARM+CPLD architecture, with its core consisting of an STMicroelectronics STM32F103 chip and an Altera EMP1270 CPLD chip. This architecture allows for powerful functionality with relatively low power consumption. The STM32F103 chip performs the following functions: 1) Receives and transmits signal parameters via an RS485 bus;

[0065] 2) Generate the MIMO sonar transmission timing based on the transmission signal parameters; 3) Obtain temperature and current data for the five transmission channels from the transmission monitoring module, and calculate the temperature and current status of each transmission channel; 4) Upload the status information to the display control system at the dry end via RS485 bus. The CPLD has a large number of I / O ports, flexible configuration, and lower power consumption compared to FPGA chips, while possessing the parallel processing advantages similar to FPGAs. It has excellent real-time processing capabilities and can effectively replace FPGAs in low-power, low-integration scenarios. In the signal source module, its functions are: 1) Control five DDS chips to generate five channels of orthogonal waveform signals, ensuring the synchronization of the five transmission channels by controlling the logic timing of each DDS chip; 2) Control the signal amplification factor in the signal drive module, providing three levels of controllable gain, thereby achieving three levels of power output from the power amplifier module; 3) Provide over-temperature and over-current protection for the power amplifier module in a timely manner when the temperature is too high or the current is abnormal.

[0066] The signal drive module employs a two-stage isolation amplification structure. First, an isolation operational amplifier performs first-stage isolation amplification on the synchronous quadrature waveform signal generated by the signal source module, isolating the signal source module and the signal drive module. Then, an isolation transformer performs second-stage isolation amplification, with the transformer's output signal driving the power amplifier module, isolating the signal drive module and the power amplifier module. Simultaneously, the transformer achieves isolation between the five channels of quadrature waveform signals. Since high-power signals are more prone to interference, the signals are isolated from each other at the drive end before power amplification. Combined with an isolated power supply design, independent transmission of the five channels of quadrature waveform signals can be achieved. The advantages of this design are reduced interference between modules and between different transmission channels. When one module or channel fails, the modules before and after it, as well as other channels, are unaffected, making troubleshooting and component replacement easier and significantly improving system reliability and maintainability.

[0067] The power amplifier module adopts a Class D power amplifier design, fully utilizing its high efficiency and small size. High-power MOSFETs are used to construct a single-ended push-pull full-bridge power amplifier circuit. Considering the significant heat generation of a single MOSFET, two MOSFETs are connected in parallel in each bridge arm. The advantages of this design are increased power capacity, reduced heat generation per MOSFET, and a pulse output power of over 800W for each power amplifier module. Each power amplifier module is equipped with a temperature sensor and a Hall effect sensor. When the temperature of a power amplifier module in a certain channel is too high or the current is abnormal, the monitoring system will promptly disconnect the power supply to that channel's power amplifier module and shut down the signal source for that channel, preventing damage to the power amplifier module.

[0068] The design of the impedance matching module requires consideration of the impedance characteristics of the transmitting transducer and the output power of the power amplifier, selecting appropriate matching network type and parameters. The load characteristics of the underwater acoustic transducer are not traditional resistive loads, but rather resistive + capacitive load characteristics, with a relatively high impedance, typically ranging from several hundred ohms to 1k ohms. In this invention, a series resonant circuit is selected to obtain a sufficiently high transmission voltage across the transmitting transducer. Since the five transmitting transducers are different and have varying resonant frequencies, impedance matching design is required for each transducer separately, necessitating five sets of impedance matching modules with different parameters. To reduce the size of the impedance matching module, this invention uses nanocrystalline material as the transformer core material. Compared to other materials, nanocrystalline material exhibits lower losses below 50kHz, allowing the transformer to achieve higher power density and a smaller size. Furthermore, as the output current increases, the inductance value of the inductor will drift, leading to waveform distortion after resonance. Therefore, this invention uses an inductor with an added energy design as the resonant inductor to increase the inductor's energy storage capacity and reduce inductance value drift during high-power transmission. Because the signal's peak-to-peak value exceeds 1000V after being stepped up by the transformer, and its amplitude is further increased after resonance by the resonant inductor, high-voltage signals are more prone to radiated interference. This invention, based on the existing transformer + inductor structure, adopts an integrated transformer and inductor packaging scheme. The inductor and the transformer's secondary coil are formed by a single, uninterrupted winding of enameled wire within the package, significantly shortening the length of the connecting wire between the transformer and the resonant inductor in the impedance matching module, reducing redundant connections, and further reducing high-voltage signal interference between channels. The turns ratio of the transformer and the inductance value of the resonant inductor in the impedance matching module are determined according to the resonant frequency of the transmitting transducer, while the inductance value is determined according to the output power of the power amplifier.

[0069] The transmitting transducer directly determines the performance parameters of the transmitting system, such as directivity, operating frequency, operating bandwidth, and sound source level. This invention uses a bent-tension transducer with a horizontal beamwidth of 360 degrees and a transmitting bandwidth of approximately 150Hz. Its resonant frequency and operating frequency range are shown in Table 1.

[0070] Table 1 Resonant Frequency and Operating Bandwidth of Transmitter Transducer

[0071]

[0072] Each transmitting channel has three output power levels: approximately 190 dB at 500 W, approximately 187 dB at 250 W, and approximately 182 dB at 75 W. A schematic diagram of the array of five transmitting transducers is shown below. Figure 5 As shown.

[0073] In this invention, the transmitting transducer at the center of the circle is fixed in position, and the other four transmitting transducers are evenly arranged on a circular array with a radius of R. The transmitting transducers are flexibly connected to the array with springs to form a transmitting array. In order to adapt to different usage scenarios, this invention designs a variety of transmitting array radii to facilitate adjustment of the transmitting array size.

[0074] To better illustrate the effects of the present invention, actual experiments are conducted to further explain and illustrate the technical solution of the present invention.

[0075] The schematic diagram of the waveform test and sound source level test scheme of the transmitting system is shown in Figure 10. The entire test was carried out in an anechoic water tank. The transmitting transducer and the standard receiving hydrophone were placed at the same depth of 5m, with a horizontal distance of 1.6m between them.

[0076] from Figures 11-15 It can be seen that after passing through the series resonant matching network, the peak-to-peak value of the transmit voltage across the transmitter transducer is above 3000V. Figure 11 The transmitting signal of the transmitting transducer 1 is a 1500Hz CW signal. The envelope of the transmitting signal is a regular rectangular envelope. After the waveform is expanded, it can be seen that the distortion is low and the waveform shape is good. Figures 12-15 The transmitting signals corresponding to transmitting transducers 2 to 5 are LFM signals of 1600-1700Hz, 1700-1800Hz, 1800-1900Hz, and 1900-2000Hz, respectively. Since the transmitting transducers exhibit resistive and capacitive load characteristics, after passing through the series resonant matching network, the envelope of their transmitting signals fluctuates slightly within the operating frequency band. After the signals are expanded, it can be seen that the waveform shapes are all well-formed and meet the design requirements.

[0077] In the sound source level test, the standard receiving hydrophone used was the Danish B&K 8104 standard hydrophone, and the formula for calculating the sound source level SL is shown in equation (5.1):

[0078]

[0079] Among them, e oc denoted as peak-to-peak value of the signal received by the standard hydrophone, d is the distance between the transmitting transducer and the standard receiving hydrophone, and 206.5dB is the receiving sensitivity of the standard receiving hydrophone in the range of 1500 to 2000 Hz. Figures 16-20 The waveforms of the signals received by the standard receiving hydrophone are shown when the five transmitting transducers are in their respective operating frequency bands.

[0080] Figure 16 The transmitting signal of the transmitting transducer 1 is a 1500Hz CW signal, and the corresponding received signal envelope is a regular rectangular envelope. After the waveform is expanded, it can be seen that the received signal waveform has a good shape. Figures 17-20 The received signals correspond to transmitting transducers 2-5, with corresponding transmitting signals being LFM signals at 1600-1700Hz, 1700-1800Hz, 1800-1900Hz, and 1900-2000Hz, respectively. Since the transmitting voltage response level of the transmitting transducers within the operating frequency band is not completely flat but slightly fluctuates, the envelope of the received signal also fluctuates. After unfolding the received signal, it can be seen that the waveform performance is good. Table 2 lists the maximum peak-to-peak value of the received signal from the standard hydrophone within the operating frequency band of the transmitting transducers, as well as the maximum sound source level of each transmitting transducer calculated according to Equation 5.1. As can be seen from Table 2, the maximum sound source level of each channel reaches over 190dB, meeting the design requirements.

[0081] Table 2 Sound Source Level of Transmitter Transducer

[0082]

Claims

1. A transmission method for a densely distributed MIMO sonar transmission system, characterized in that, The dense MIMO sonar transmission system includes a dry-end component and a wet-end component, wherein the dry-end component is located above the sea level and the wet-end component is located below the sea level, and the dry-end component and the wet-end component are connected by a cable. The dry-end component includes a power management module and a display control module, wherein the power management module is used for the overall power supply of the dense MIMO sonar transmission system, and the display control module is used for the human-computer interaction of the dense MIMO sonar transmission system. The wet-end assembly is used for synchronous pulse transmission of high-power, multi-channel orthogonal waveform signals. The wet-end assembly includes a transmission system monitoring module, a signal source module, a signal driver module, a power amplifier module, an impedance matching module, and a transmitting transducer. Signals between the signal source module, signal driver module, and power amplifier module are transmitted in isolation, and channel-to-channel signal isolation is achieved within the signal driver module and power amplifier module. The transmission system monitoring module uniformly allocates the power supply to each sub-module of the wet-end assembly, achieving power isolation between modules. The signal driving module includes a two-stage isolation amplification structure, wherein the first-stage isolation amplification structure uses an isolation operational amplifier to amplify the synchronous orthogonal waveform signal generated by the signal source module, thereby achieving signal isolation between the signal source module and the signal driving module. The second-stage isolation amplification structure uses an isolation transformer to amplify the signal, achieving signal isolation between the signal drive module and the power amplifier module. The output signal of the transformer is used to drive the power amplifier module, and the transformer is also used to achieve drive signal isolation between channels. In the transmission system monitoring module, the power control uses multiple isolated voltage conversion chips to convert high voltage into the voltage required by each module, and the power systems of each module are isolated from each other; the two-stage isolation amplification structure isolates the signals from each other at the driver end, and combined with the isolated power supply design, it is used to realize the independent transmission of orthogonal waveform signals of 5 channels, reducing interference between modules and between different transmission channels; The launch method includes the following steps: Step 1: Power the dense MIMO sonar transmitting system using marine batteries / storage batteries. The power management module performs step-down isolation conversion. The industrial control computer is powered on, and the display and control module program runs. It detects the voltage and power of the power supply. When the voltage is normal, the relay closes and performs step-up isolation conversion to power the wet-end components through the cable. When undervoltage or overvoltage occurs, the display and control module alarms and the relay opens. Step 2: After the wet end component is powered on, the transmission system monitoring module starts working, the signal source module and the signal drive module are powered on first, and the temperature sensor and the current sensor start working. Step 3: Select the transmission channel of the transmission system in the human-computer interaction software, set the signal frequency, signal pulse width, signal period and transmission power of each channel, and send the command to the wet end component through the RS485 bus; Step 4: After receiving the command, the signal source module parses the transmission channel number, signal frequency, signal pulse width, signal period, and transmission power according to the protocol. The relay of the corresponding channel closes, the power amplifier module is powered on, and the signal source module generates the corresponding synchronous quadrature waveform signal. After isolation driving, the power is amplified in the power amplifier module of the corresponding channel. Then, through the corresponding impedance matching network, the signal is loaded onto the corresponding transmitting transducer. Finally, the transmitting transducer radiates the signal into the water. Step 5: Obtain the temperature and current status of the transmitter through temperature and current sensors, and upload the status information through RS485 bus. Display the information in the human-machine interface software. When a channel experiences an abnormal status, the protection mechanism is activated, the signal source module stops the signal output of that channel, the power amplifier module of the corresponding channel is powered off, and an alarm is triggered in the human-machine interface software. Step 6: Once the transmission system is operational, use the human-machine interface software to power off the power amplifier modules of all channels, disconnect the dry-end relays, and power off the wet-end relays. If necessary, send the log containing transmission location information, transmission time information, transmission signal parameters, and transmitter status to other users via the network connector. Finally, shut down the industrial control system and disconnect the power supply to the dense MIMO sonar transmission system.

2. The transmission method of a densely distributed MIMO sonar transmission system as described in claim 1, characterized in that, The wet end assembly also includes a wet end housing and a watertight connector. The wet end housing contains, from top to bottom, a cable watertight connector, a transmission system monitoring module, a signal source module, a signal drive module, a power amplifier module, an impedance matching module, and a high-voltage watertight connector for the transmitter transducer. The cable watertight connector is used to connect to the cable, and the high-voltage watertight connector for the transmitter transducer is used to connect to the transmitter transducer.

3. The transmission method of a densely distributed MIMO sonar transmission system as described in claim 2, characterized in that, The launch system monitoring module includes a temperature sensor, a Hall sensor, a photoelectric sensor, and a DC relay. The temperature sensor and Hall sensor collect temperature and current data of the launch channel, and the photoelectric sensor and DC relay control the power supply of the launch channel.

4. The transmission method of a densely distributed MIMO sonar transmission system as described in claim 2, characterized in that, Aluminum plates are mounted below the power amplifier modules, and high-power devices are mounted on the aluminum plates via alumina ceramic sheets.

5. The transmission method of a densely distributed MIMO sonar transmission system as described in claim 2, characterized in that, The power amplifier module adopts a Class D power amplifier scheme and uses a single-ended push-pull full-bridge power amplifier circuit composed of high-power MOSFETs to amplify the signal power. Each bridge arm uses two MOSFETs connected in parallel.

6. The transmission method of a densely distributed MIMO sonar transmission system as described in claim 2, characterized in that, The impedance matching module adopts a series resonant circuit and uses nanocrystalline material as the core material of the transformer. It adopts an integrated packaging scheme for the transformer and inductor, encapsulating the transformer and inductor in one package with epoxy resin. The secondary coil of the inductor and the transformer are continuously wound together by a single enameled wire inside the package. The turns ratio of the transformer, the inductance value of the resonant inductor, and the magnitude of the resonant inductor in the impedance matching module are determined according to the resonant frequency of the transmitting transducer and the output power of the power amplifier.

7. The transmission method of a densely distributed MIMO sonar transmission system as described in claim 2, characterized in that, The transmitting transducer consists of several bent-tension transducers forming a circle, with one bent-tension transducer at the center and the other bent-tension transducers evenly arranged on a circular array frame with a radius of R. The transmitting transducers are flexibly connected to the array frame using springs to form a transmitting array. The size of the transmitting array can be adjusted by adjusting the radius R.

8. The transmission method of a densely distributed MIMO sonar transmission system as described in claim 1, characterized in that, When the launch system is working, the human-computer interaction software records the current launch information, including launch location information, launch time information, launch signal parameters, and transmitter status, and generates a test log file. The software generates a test log file every time it runs. Historical launch information can be viewed through the test log, and the test log can be sent and shared with other users through the network connector.

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