Adaptive filtering data transmission system and method

Abstract

This invention provides an adaptive filtering data transmission system and method, applicable to the field of communication technology. The data transmission system includes a demodulation circuit positioned below sea level, comprising: an adaptive filtering module providing a first modulation signal to a phase-locked loop (PLL) sub-circuit under the control of a first control signal; adjusting the filtering parameters according to the error between a target carrier signal and a first filtered signal obtained by filtering the first modulation signal based on filtering parameters, under the control of a second control signal, to obtain target filtering parameters; performing weighted moving average filtering on a second modulation signal based on the target filtering parameters to obtain a second filtered signal; the PLL sub-circuit adjusting the phase of an initial carrier signal using the first modulation signal to obtain a target carrier signal; performing coherent demodulation on the second filtered signal using the target carrier signal to obtain a first in-phase component; and a code stream recovery sub-circuit decoding the first in-phase component according to a predetermined decoding rule to obtain a first decoded code stream.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and more specifically, to an adaptive filtering data transmission system and method. Background Technology

[0002] Moored buoys, as surface observation platforms, are an important component of the ocean's three-dimensional observation network. Based on the structural characteristics of moored buoys, a data transmission method based on the principle of magnetic coupling has been proposed for use with moored buoys. This magnetic coupling data transmission technology utilizes the characteristics of the buoy platform to fix underwater sensors at predetermined positions within the mooring system, and uses a single-core, common cable to transmit data to the surface platform in real time.

[0003] The data signals transmitted by the magnetically coupled data transmission system used in the related technology are greatly affected by the marine environment, resulting in a high bit error rate and thus reducing the reliability of communication and the efficiency of data transmission. Summary of the Invention

[0004] In view of this, the present invention provides an adaptive filtering data transmission system and method.

[0005] According to one aspect of the present invention, an adaptive filtering data transmission system is provided, comprising: a demodulation circuit disposed below sea level, including:

[0006] An adaptive filtering module is configured to provide a first modulation signal to a phase-locked loop circuit under the control of a first control signal; and, under the control of a second control signal, adjust the filtering parameters in the adaptive filtering module according to the error between a target carrier signal and a first filtered signal obtained by filtering the first modulation signal based on the filtering parameters in the adaptive filtering module, to obtain target filtering parameters; and perform weighted moving average filtering on the second modulation signal based on the target filtering parameters to obtain a second filtered signal, wherein the first modulation signal is obtained by demodulating an analog transmission signal corresponding to a first bit value, and the second modulation signal is obtained by demodulating an analog transmission signal corresponding to a first bit value and a second bit value.

[0007] The aforementioned phase-locked loop circuit is used to adjust the phase of the initial carrier signal using the aforementioned first modulation signal to obtain the aforementioned target carrier signal, wherein the phase difference between the aforementioned target carrier signal and the aforementioned first modulation signal is less than a predetermined phase threshold; and to coherently demodulate the aforementioned second filtered signal using the aforementioned target carrier signal to obtain a first in-phase component;

[0008] The bitstream recovery sub-circuit is used to decode the first in-phase component according to a predetermined decoding rule to obtain the first decoded bitstream.

[0009] According to an embodiment of the present invention, the above-described data transmission system further includes: a first coupler, a second coupler, a plastic-coated cable, and two electrode plates respectively connected to both ends of the plastic-coated cable, wherein the first coupler and the second coupler each have a central hole, the two ends of the plastic-coated cable pass through the central holes of the first coupler and the second coupler respectively, and the transmission circuit formed by the plastic-coated cable, the two electrode plates at both ends of the plastic-coated cable, and seawater is electromagnetically coupled to the first coupler, and the transmission circuit is electromagnetically coupled to the second coupler.

[0010] The first coupler is used to receive the analog transmission signal from the modulation circuit and transmit the analog transmission signal to the second coupler via the transmission loop; the second coupler is used to transmit the analog transmission signal to the demodulation circuit.

[0011] According to an embodiment of the present invention, the phase-locked loop circuit is further configured to: output a first level signal when the phase difference between the initial carrier signal and the first modulation signal is greater than or equal to a predetermined phase threshold; output a second level signal when the phase difference between the target carrier signal and the first modulation signal is less than the predetermined phase threshold; and perform coherent demodulation on the first modulation signal using the target carrier signal to obtain a second in-phase component, wherein the amplitude of the second level signal is greater than the amplitude of the first level signal.

[0012] The bitstream recovery sub-circuit is also used to: decode the second in-phase component according to a predetermined decoding rule to obtain a second decoded bitstream; output a third level signal when the number of consecutive first bit values ​​included in the second decoded bitstream is less than or equal to a predetermined number; and output a fourth level signal when the number of consecutive first bit values ​​included in the second decoded bitstream is greater than the predetermined number, wherein the amplitude of the fourth level signal is greater than the amplitude of the third level signal.

[0013] The adaptive filtering module is further configured to: provide the first modulation signal to the phase-locked loop circuit upon receiving the first level signal and / or the third level signal; and confirm receipt of the second control signal upon receiving the second level signal and the fourth level signal, and perform an operation on the modulation signal input to the adaptive filtering module under the control of the second control signal; wherein the second control signal includes the second level signal and the fourth level signal.

[0014] According to an embodiment of the present invention, the phase-locked loop (PLL) sub-circuit includes: a numerically controlled oscillator for generating the initial carrier signal and adjusting the phase of the initial carrier signal according to a time-varying signal to obtain an adjusted carrier signal, wherein the adjusted carrier signal includes the target carrier signal; an I-channel multiplier for multiplying the adjusted carrier signal with an input signal to obtain an initial in-phase component, wherein the input signal is the second filtered signal or the first modulated signal; a first low-pass filter for low-pass filtering the initial in-phase component to obtain an in-phase component, wherein the in-phase component is the first in-phase component or the second in-phase component; a Q-channel multiplier for multiplying the input signal with an adjusted carrier signal that has undergone a predetermined phase shift to obtain an initial quadrature component; a second low-pass filter for low-pass filtering the initial quadrature component to obtain a quadrature component; a loop multiplier for multiplying the in-phase component with the quadrature component to obtain an initial time-varying signal; and a loop filter for loop filtering the initial time-varying signal to obtain the time-varying signal.

[0015] According to an embodiment of the present invention, the first low-pass filter, the second low-pass filter, and the loop filter are all filters capable of implementing weighted moving average filtering; the adaptive filtering module includes a filter capable of implementing weighted moving average filtering.

[0016] According to an embodiment of the present invention, the above-described phase-locked loop circuit is further configured to: adjust the phase of the current target carrier signal using the current second filter signal to obtain an adjusted target carrier signal, and then use the adjusted target carrier signal to coherently demodulate the next second filter signal.

[0017] According to an embodiment of the present invention, the demodulation circuit further includes: a bandpass filter, configured to perform bandpass filtering on the analog transmission signal corresponding to the first bit value when receiving the analog transmission signal corresponding to the first bit value to obtain a first analog filtered signal; and to perform bandpass filtering on the analog transmission signal corresponding to the first bit value and the second bit value when receiving the analog transmission signal corresponding to the first bit value and the second bit value to obtain a second analog filtered signal; a signal amplifier, configured to amplify the first analog filtered signal when receiving the first analog filtered signal to obtain a first amplified signal; and to amplify the second analog filtered signal when receiving the second analog filtered signal to obtain a second amplified signal; and an analog-to-digital converter, configured to perform analog-to-digital conversion on the first amplified signal when receiving the first amplified signal to obtain the first modulated signal; and to perform analog-to-digital conversion on the second amplified signal when receiving the second amplified signal to obtain the second modulated signal.

[0018] According to an embodiment of the present invention, the above-described data transmission system further includes: a modulation circuit disposed on the sea surface, configured to, upon receiving an input code stream corresponding to a first bit value, perform differential phase shift keying modulation on the input code stream corresponding to the first bit value to obtain an analog transmission signal corresponding to the first bit value; and, upon receiving an input code stream corresponding to a first bit value and a second bit value, perform differential phase shift keying modulation on the input code stream corresponding to the first bit value and the second bit value to obtain an analog transmission signal corresponding to the first bit value and the second bit value.

[0019] According to an embodiment of the present invention, under the control of a second control signal, the adaptive filtering module adjusts the filtering parameters in the adaptive filtering module based on the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal based on the filtering parameters in the adaptive filtering module, thereby obtaining the target filtering parameters including:

[0020] Repeat the following operation until the error is less than the predetermined error:

[0021] Based on the filtering parameters of the i-th round in the above adaptive filtering module, the first modulation signal of the i-th round is filtered to obtain the reference signal of the i-th round, where i is a positive integer;

[0022] Calculate the error between the target carrier signal and the reference signal in the i-th round to obtain the error in the i-th round;

[0023] If the error in the i-th round is greater than or equal to the predetermined error, the filtering parameters in the i-th round of the adaptive filtering module are adjusted according to the error in the i-th round. The adjusted filtering parameters are used as the filtering parameters for the next round. The process is incremented by i, and the operation of filtering the first modulation signal in the i-th round based on the filtering parameters in the i-th round of the adaptive filtering module is returned.

[0024] According to another aspect of the present invention, an adaptive filtering data transmission method is provided, applied to the aforementioned adaptive filtering data transmission system, the data transmission method comprising:

[0025] Under the control of the first control signal, the adaptive filtering module provides the first modulation signal to the phase-locked loop (PLL) circuit. The first modulation signal is obtained by demodulating the analog transmission signal corresponding to the first bit value. The PLL circuit uses the first modulation signal to adjust the phase of the initial carrier signal to obtain the target carrier signal. The phase difference between the target carrier signal and the first modulation signal is less than a predetermined phase threshold.

[0026] Under the control of the second control signal, the adaptive filtering module adjusts the filtering parameters in the adaptive filtering module according to the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal based on the filtering parameters in the adaptive filtering module, thereby obtaining target filtering parameters. Based on the target filtering parameters, the second modulated signal is subjected to weighted moving average filtering to obtain a second filtered signal, wherein the second modulated signal is obtained by demodulating the analog transmission signal corresponding to the first bit value and the second bit value. The phase-locked loop sub-circuit uses the target carrier signal to coherently demodulate the second filtered signal to obtain a first in-phase component. The code stream recovery sub-circuit decodes the first in-phase component according to a predetermined decoding rule to obtain a first decoded code stream.

[0027] According to an embodiment of the present invention, by adjusting the phase of the initial carrier signal using the first modulation signal through the phase-locked loop sub-circuit in the demodulation circuit, a target carrier signal with a phase difference less than a predetermined phase threshold and the same frequency as the first modulation signal can be obtained, and the target carrier signal does not include noise signals introduced by the marine environment, wherein the first modulation signal includes noise signals introduced by the marine environment. By using an adaptive filtering module to adjust the filtering parameters in the adaptive filtering module according to the error between the target carrier signal and the first filtered signal obtained by filtering the first modulation signal based on the filtering parameters in the adaptive filtering module, the target filtering parameters can be obtained. The target carrier signal can be used as the desired signal, and the filtering parameters can be adjusted according to the first modulation signal and the desired signal, thereby realizing dynamic adjustment of the filtering parameters based on the LMS algorithm. Subsequently, when the second modulation signal is subjected to weighted moving average filtering based on the adjusted target filtering parameters, marine environmental noise can be effectively suppressed, and a more accurate second filtered signal can be obtained. After the phase-locked loop sub-circuit and the code stream recovery sub-circuit sequentially perform coherent demodulation and decoding on the second filtered signal, a more accurate decoded code stream can be obtained, significantly reducing the bit error rate and improving the reliability and data transmission efficiency of underwater communication. Attached Figure Description

[0028] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0029] Figure 1 A schematic diagram of an adaptive filtering data transmission system according to an embodiment of the present invention is shown.

[0030] Figure 2 A schematic diagram of an adaptive filtering data transmission system according to another embodiment of the present invention is shown.

[0031] Figure 3A schematic diagram showing the result of the demodulation circuit processing the modulated signal in an adaptive filtering data transmission system according to an embodiment of the present invention is illustrated.

[0032] Figure 4 A flowchart of an adaptive filtering data transmission method according to an embodiment of the present invention is shown. Detailed Implementation

[0033] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0035] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0036] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0037] Moored buoys, as a type of surface observation platform, are an important component of the three-dimensional ocean observation network. A typical moored buoy may include sensors for measuring surface wind speed and direction, underwater water temperature and salinity, a data logger for receiving sensor data, a communication module for transmitting data to satellites, and a mooring cable for anchoring and communication.

[0038] Based on the structural characteristics of moored buoys, this research proposes a data transmission method for moored buoys that differs from traditional wired and wireless communication and is based on the principle of magnetic coupling. This magnetic coupling data transmission technology utilizes the characteristics of the buoy platform to fix underwater sensors at predetermined positions within the mooring system. Data is transmitted in real-time to the surface platform using a single-core, common cable. This eliminates the need for multi-core watertight cables, reducing system complexity and cost, while also minimizing the attenuation of electromagnetic waves by seawater.

[0039] However, due to the complex and variable marine environment, the signals of underwater magnetically coupled data transmission systems are easily affected by various types of noise during transmission. These interference noises affect the signal transmission quality, leading to a higher bit error rate in the magnetically coupled data transmission system, which in turn reduces the reliability of communication and the efficiency of data transmission.

[0040] In view of this, the present invention provides an adaptive filtering data transmission system and method that can be applied to the field of communication technology.

[0041] Figure 1 A schematic diagram of an adaptive filtering data transmission system according to an embodiment of the present invention is shown.

[0042] like Figure 1 As shown, the adaptive filtering data transmission system may include a demodulation circuit positioned below sea level.

[0043] In embodiments of the present invention, "located below sea level" indicates that it is located in seawater, and "located above sea level" indicates that it is not located in seawater and is separated from seawater.

[0044] The demodulation circuit may include an adaptive filtering module, a phase-locked loop (PLL) sub-circuit, and a bitstream recovery sub-circuit.

[0045] The adaptive filtering module can receive control signals, modulation signals, and a target carrier signal from the phase-locked loop (PLL) circuit. The control signals may include a first control signal and a second control signal. The modulation signals may include a first modulation signal and a second modulation signal. The first modulation signal is obtained by demodulating the analog transmission signal corresponding to a first bit value, and the second modulation signal is obtained by demodulating the analog transmission signal corresponding to the first bit value and the second bit value.

[0046] For example, the first bit value can be 0, and the second bit value can be 1. The analog transmission signal corresponding to the first bit value is obtained by modulating the input code stream composed of multiple first bit values ​​using a modulation circuit. The analog transmission signal corresponding to the first bit value and the second bit value is obtained by modulating the input code stream composed of multiple first bit values ​​and multiple second bit values ​​using a modulation circuit.

[0047] The adaptive filtering module can be used to provide the first modulation signal to the phase-locked loop circuit under the control of the first control signal.

[0048] According to an embodiment of the present invention, after the adaptive filtering data transmission system is started, the modulation circuit first modulates the input code stream composed of multiple first bit values ​​to obtain an analog transmission signal corresponding to the first bit value, and transmits the analog transmission signal corresponding to the first bit value to the demodulation circuit. After receiving the analog transmission signal corresponding to the first bit value, the demodulation circuit demodulates it to obtain a first modulated signal. The first modulated signal does not pass through the adaptive filtering module, but is directly input to the subsequent phase-locked loop circuit. At this time, the original bit stream data... The input code stream (i.e., composed of multiple first bit values) is always equal to 0, indicating that the adaptive filtering module does not need to be started, that is, the adaptive filtering module does not need to be used to filter the first modulation signal.

[0049] The phase-locked loop (PLL) circuit can generate an initial carrier signal with a predetermined frequency and phase. The frequency of the initial carrier signal can be equal to the frequencies of the first and second modulating signals.

[0050] A phase-locked loop (PLL) circuit can be used to adjust the phase of an initial carrier signal using a first modulation signal to obtain a target carrier signal. The phase difference between the target carrier signal and the first modulation signal is less than a predetermined phase threshold. The frequency of the target carrier signal can be the same as that of the first modulation signal.

[0051] According to an embodiment of the present invention, when the phase difference between the target carrier signal and the first modulation signal is less than a predetermined phase threshold, it is considered that the target carrier signal is substantially equal to the carrier signal used when modulating the input code stream composed of multiple first bit values ​​using the modulation circuit.

[0052] According to an embodiment of the present invention, since the analog transmission signal corresponding to the first bit value is interfered with by noise in the complex marine environment during transmission, the analog transmission signal corresponding to the first bit value received by the demodulation circuit also includes noise signals introduced by the marine environment, so that the first modulation signal obtained by the demodulation circuit also includes noise signals introduced by the marine environment.

[0053] According to an embodiment of the present invention, the phase-locked loop (PLL) sub-circuit can realize the function of a phase-locked loop. During the process of adjusting the phase of the initial carrier signal using the first modulation signal, the PLL sub-circuit can filter out noise signals introduced by the marine environment included in the first modulation signal, while simultaneously locking the phases of the first modulation signal and the initial carrier signal.

[0054] The adaptive filtering module can be used, under the control of the second control signal, to adjust the filtering parameters in the adaptive filtering module according to the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal based on the filtering parameters in the adaptive filtering module, to obtain the target filtering parameters; and to perform weighted moving average filtering on the second modulated signal based on the target filtering parameters to obtain the second filtered signal.

[0055] For example, the adaptive filtering module can be used, under the control of the second control signal and when the third flag bit lms_locked in the adaptive filtering module is 0, to determine the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal based on the filtering parameters in the adaptive filtering module, and adjust the filtering parameters in the adaptive filtering module to obtain the target filtering parameters. After obtaining the target filtering parameters, the adaptive filtering module also sets the third flag bit lms_locked to 1. Alternatively, under the control of the second control signal and when the third flag bit lms_locked in the adaptive filtering module is 1, the adaptive filtering module can determine that the filtering parameters training in the adaptive filtering module is complete. At this point, the target filtering parameters in the adaptive filtering module can be used to perform weighted moving average filtering on the second modulated signal received by the adaptive filtering module to effectively suppress marine environmental noise and obtain a more accurate second filtered signal.

[0056] For example, the filtering parameters in the adaptive filtering module can be the same as those of the FIR (Finite Impulse Response) filter.

[0057] According to an embodiment of the present invention, by utilizing an adaptive filtering module under the control of a second control signal, the filtering parameters in the adaptive filtering module are adjusted based on the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal using the filtering parameters in the adaptive filtering module. This yields target filtering parameters, allowing the target carrier signal to be used as the desired signal. By adjusting the filtering parameters in the adaptive filtering module based on the first modulated signal and the desired signal, the filtering parameters in the adaptive filtering module are dynamically adjusted using the LMS (Least Mean Square) algorithm. Subsequently, when the second modulated signal is subjected to weighted moving average filtering based on the adjusted target filtering parameters, marine environmental noise can be effectively suppressed, resulting in a more accurate second filtered signal.

[0058] The phase-locked loop circuit can be used to coherently demodulate the second filtered signal using the target carrier signal to obtain the first in-phase component.

[0059] The bitstream recovery sub-circuit can receive the first in-phase component and output a demodulated signal. The demodulated signal may include the signal corresponding to the first decoded bitstream.

[0060] The bitstream recovery sub-circuit can be used to decode the first in-phase component according to a predetermined decoding rule to obtain the first decoded bitstream.

[0061] For example, the predetermined decoding rule can be a decoding rule corresponding to the DPSK (Differential Phase-Shift Keying) principle. When modulating the input bitstream using a modulation circuit, the input bitstream can also be modulated based on the DPSK principle.

[0062] According to an embodiment of the present invention, by adjusting the phase of the initial carrier signal using the first modulation signal through the phase-locked loop sub-circuit in the demodulation circuit, a target carrier signal with a phase difference less than a predetermined phase threshold and the same frequency as the first modulation signal can be obtained, and the target carrier signal does not include noise signals introduced by the marine environment, wherein the first modulation signal includes noise signals introduced by the marine environment. By using an adaptive filtering module to adjust the filtering parameters in the adaptive filtering module according to the error between the target carrier signal and the first filtered signal obtained by filtering the first modulation signal based on the filtering parameters in the adaptive filtering module, the target filtering parameters can be obtained. The target carrier signal can be used as the desired signal, and the filtering parameters can be adjusted according to the first modulation signal and the desired signal, thereby realizing dynamic adjustment of the filtering parameters based on the LMS algorithm. Subsequently, when the second modulation signal is subjected to weighted moving average filtering based on the adjusted target filtering parameters, marine environmental noise can be effectively suppressed, and a more accurate second filtered signal can be obtained. After the phase-locked loop sub-circuit and the code stream recovery sub-circuit sequentially perform coherent demodulation and decoding on the second filtered signal, a more accurate decoded code stream can be obtained, significantly reducing the bit error rate and improving the reliability and data transmission efficiency of underwater communication.

[0063] According to an embodiment of the present invention, the phase-locked loop circuit is further configured to: adjust the phase of the current target carrier signal using the current second filter signal to obtain an adjusted target carrier signal, and then use the adjusted target carrier signal to coherently demodulate the next second filter signal.

[0064] According to an embodiment of the present invention, the phase-locked loop (PLL) sub-circuit adjusts the phase of the current target carrier signal using the current second filter signal to obtain the adjusted target carrier signal. This ensures that the target carrier signal output by the PLL sub-circuit is substantially equal to the carrier signal used when the input code stream is modulated by the modulation circuit in real time, so as to use the adjusted target carrier signal to perform more accurate coherent demodulation of the next second filter signal.

[0065] The phase-locked loop (PLL) circuit can also be used to: output a first-level signal when the phase difference between the initial carrier signal and the first modulation signal is greater than or equal to a predetermined phase threshold; and output a second-level signal when the phase difference between the target carrier signal and the first modulation signal is less than the predetermined phase threshold, thereby coherently demodulating the first modulation signal using the target carrier signal to obtain a second in-phase component. The amplitude of the second-level signal is greater than the amplitude of the first-level signal.

[0066] The bitstream recovery sub-circuit can also be used to: decode the second in-phase component according to a predetermined decoding rule to obtain a second decoded bitstream; output a third level signal when the number of consecutive first bit values ​​included in the second decoded bitstream is less than or equal to a predetermined number; and output a fourth level signal when the number of consecutive first bit values ​​included in the second decoded bitstream is greater than a predetermined number. The amplitude of the fourth level signal is greater than the amplitude of the third level signal.

[0067] The adaptive filtering module can also be used to provide a first modulation signal to the phase-locked loop circuit upon receiving a first level signal and / or a third level signal.

[0068] When the adaptive filtering module receives the first level signal, or the third level signal, or both the first and third level signals, it confirms that the first control signal has been received. The adaptive filtering module does not start and provides the first modulation signal to the phase-locked loop circuit.

[0069] The adaptive filtering module can also be used to: confirm the receipt of a second control signal upon receiving a second level signal and a fourth level signal, and to perform operations on the modulation signal input to the adaptive filtering module under the control of the second control signal. The second control signal includes the second level signal and the fourth level signal.

[0070] According to an embodiment of the present invention, the adaptive filtering module can, upon receiving a first level signal and / or a third level signal, confirm the receipt of a first control signal, and thereby determine that the carrier signal output by the phase-locked loop circuit is not equal to the carrier signal used when modulating the input code stream using the modulation circuit, or that the number of consecutive first bit values ​​included in the second decoded code stream is less than or equal to a predetermined number. In this case, the agreed-upon conditions for starting training the filtering parameters in the adaptive filtering module have not been met, and the filtering parameters in the adaptive filtering module are not adjusted. Furthermore, upon receiving a second level signal and a fourth level signal, it confirms the receipt of a second control signal, thus meeting the agreed-upon conditions for starting training the filtering parameters in the adaptive filtering module. The filtering parameters in the adaptive filtering module are then adjusted, and a weighted moving average filter is performed on the second modulated signal based on the obtained target filtering parameters to obtain a more accurate second filtered signal.

[0071] According to an embodiment of the present invention, under the control of a second control signal, the adaptive filtering module adjusts the filtering parameters in the adaptive filtering module based on the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal based on the filtering parameters in the adaptive filtering module. Obtaining the target filtering parameters may include cyclically performing the following operations until the error is less than a predetermined error: filtering the first modulated signal of the i-th round based on the filtering parameters of the i-th round in the adaptive filtering module to obtain the reference signal of the i-th round, where i is a positive integer; calculating the error between the target carrier signal and the reference signal of the i-th round to obtain the error of the i-th round; if the error of the i-th round is greater than or equal to the predetermined error, adjusting the filtering parameters of the i-th round in the adaptive filtering module based on the error of the i-th round, using the adjusted filtering parameters as the filtering parameters for the next round, incrementing i, and returning to the operation of filtering the first modulated signal of the i-th round based on the filtering parameters of the i-th round in the adaptive filtering module.

[0072] According to an embodiment of the present invention, the following operations are performed cyclically until the error is less than a predetermined error: filtering the first modulation signal of the i-th round based on the filtering parameters of the i-th round in the adaptive filtering module to obtain the reference signal of the i-th round; calculating the error between the target carrier signal and the reference signal of the i-th round to obtain the error of the i-th round; if the error of the i-th round is greater than or equal to the predetermined error, adjusting the filtering parameters of the i-th round in the adaptive filtering module according to the error of the i-th round, using the adjusted filtering parameters as the filtering parameters for the next round, incrementing by i, and returning to the operation of filtering the first modulation signal of the i-th round based on the filtering parameters of the i-th round in the adaptive filtering module. This technical means enables the target carrier signal to be used as the desired signal, and the filtering parameters to be adjusted according to the first modulation signal and the desired signal in each round, thereby realizing dynamic adjustment of the filtering parameters based on the LMS algorithm. Subsequently, when performing weighted moving average filtering on the second modulation signal based on the adjusted target filtering parameters, marine environmental noise can be effectively suppressed, and a more accurate second filtered signal can be obtained.

[0073] Figure 2 A schematic diagram of an adaptive filtering data transmission system according to another embodiment of the present invention is shown.

[0074] like Figure 2 As shown, the adaptive filtering data transmission system may include a modulation circuit set on the sea surface, a demodulation circuit set below the sea surface, a first coupler, a second coupler, a plastic-coated cable, and two electrode plates respectively connected to the two ends of the plastic-coated cable.

[0075] The function of the modulation circuit is to modulate the input code stream according to the DPSK principle, converting the 0 / 1 bit stream data (i.e., the input code stream) into changes in the relative phase of the carrier wave, thereby generating a modulated signal.

[0076] The modulation circuit can be used to perform differential phase shift keying modulation (i.e., DPSK modulation) on the input code stream corresponding to the first bit value when it receives the input code stream corresponding to the first bit value, to obtain an analog transmission signal corresponding to the first bit value; and to perform differential phase shift keying modulation on the input code stream corresponding to the first bit value and the second bit value when it receives the input code stream corresponding to the first bit value and the second bit value, to obtain an analog transmission signal corresponding to the first bit value and the second bit value.

[0077] The input bitstream corresponding to the first bit value is an input bitstream composed of multiple first bit values. The input bitstream corresponding to the first bit value and the second bit value is an input bitstream composed of multiple first bit values ​​and multiple second bit values.

[0078] The modulation circuit may include a digital frequency synthesizer, a symbol conversion module, a multiplier, a digital-to-analog converter (DAC), a bandpass filter, and a signal amplifier.

[0079] The digital frequency synthesizer can generate a carrier signal with a predetermined frequency and phase according to software settings. The symbol conversion module can convert the original 0 / 1 bit stream data (i.e., the input code stream) into relative codes and generate a baseband signal based on the relative codes and the baseband frequency set in the software. The relative codes are data streams with values ​​of "-1" and "+1". When the original bit stream data is "0", the value of the relative code remains unchanged; when the original bit stream data is "1", the value of the relative code is inverted.

[0080] A multiplier multiplies the carrier signal generated by the digital frequency synthesizer and the baseband signal generated by the symbol conversion module to obtain a modulated signal. The modulated signal output by the multiplier is a digital modulated signal.

[0081] A digital-to-analog converter, a bandpass filter, and a signal amplifier sequentially perform digital-to-analog conversion, bandpass filtering, and signal amplification on the modulated signal output from the multiplier to obtain an analog transmission signal. The analog transmission signal may include an analog transmission signal corresponding to the first bit value and analog transmission signals corresponding to the first bit value and the second bit value.

[0082] The specific steps of signal modulation by the modulation circuit are as follows: The digital frequency synthesizer of the modulation circuit has a phase accumulator and a sine lookup table. The phase accumulator accumulates a phase step value according to the carrier frequency set in the software at the rising edge of each FPGA (Field Programmable Gate Array) clock. The sine lookup table uses the phase output of the phase accumulator as the lookup address, searches for the sine value corresponding to that address, and generates a carrier signal of the corresponding frequency based on the sine value that changes over time. The symbol conversion module converts the original 0 / 1 bit stream data (i.e., the input code stream) into relative codes and generates a baseband signal according to the relative codes and the baseband frequency set in the software. The carrier signal and the baseband signal are multiplied by the input multiplier to generate a digital modulation signal. The digital-to-analog converter, bandpass filter, and signal amplifier can sequentially perform digital-to-analog conversion, bandpass filtering, and signal amplification on the digital modulation signal output from the multiplier to obtain an analog transmission signal.

[0083] The original bitstream data can be converted using the symbol transformation module according to formula (1). Convert to relative code .

[0084] (1);

[0085] in, , Represents the raw bitstream data. , , and Both represent relative codes, where n is the sampling number, and n is an integer greater than or equal to 1. When n equals 1, It is assigned an initial value of 1 or -1.

[0086] Subsequently, the symbol transformation module can be used to obtain the relative code based on the baseband frequency and formula (1). Generate the baseband signal. According to formula (2), the carrier signal and the baseband signal are multiplied by a multiplier to generate a digital modulation signal. .

[0087] (2);

[0088] in, Indicates carrier signal, Indicates baseband signal, Indicates the amplitude of the digitally modulated signal. Indicates the carrier frequency. Indicates the initial phase of the carrier signal. Indicates the baseband frequency. Let t represent a rectangular pulse function, and t represent time.

[0089] According to formulas (1) and (2), when When the phase of the digitally modulated signal remains unchanged; when At this time, the phase of the digital modulation signal flips.

[0090] like Figure 2 As shown, all couplers, electrode plates, and plastic-coated cables are submerged in seawater. Both the first and second couplers have a central hole (…). Figure 2 (Not shown).

[0091] The two ends of the plastic-coated cable pass through the central holes of the first coupler and the second coupler, respectively. The transmission circuit, which consists of the plastic-coated cable, the two electrode plates at both ends of the plastic-coated cable, and seawater, is electromagnetically coupled to the first coupler, and electromagnetically coupled to the second coupler.

[0092] According to an embodiment of the present invention, a plastic-coated cable with electrode plates at both ends passes through the middle of each coupler.

[0093] The first coupler can be used to receive the analog transmission signal from the modulation circuit and transmit the analog transmission signal to the second coupler via the transmission loop. The second coupler can be used to transmit the analog transmission signal to the demodulation circuit.

[0094] According to an embodiment of the present invention, both the first coupler and the second coupler are magnetic rings made of manganese-zinc ferrite material, with several turns of enameled copper wire wound on the magnetic rings. The two ends of the copper wire wound on the magnetic ring of the first coupler are connected to the signal amplifier in the modulation circuit, and the two ends of the copper wire wound on the magnetic ring of the second coupler are connected to the bandpass filter in the demodulation circuit.

[0095] According to an embodiment of the present invention, the plastic-coated cable is a cable capable of conducting electricity, transmitting electrical signals, and bearing mechanical loads. The plastic-coated cable may include plastic-coated steel cable. The length of the plastic-coated cable is greater than 0 and less than or equal to 100m. Both electrode plates are conductive metal plates.

[0096] According to an embodiment of the present invention, for a transmission circuit consisting of a plastic-coated cable, two electrode plates at both ends of the plastic-coated cable, and seawater, the current in the transmission circuit is relatively small, less than 100mA.

[0097] According to an embodiment of the present invention, the analog transmission signal from the transmitting end (i.e., from the modulation circuit) is input through a first coupler and coupled into the plastic-coated cable based on the principle of electromagnetic induction coupling. The plastic-coated cable, electrode plates, and seawater can constitute a signal transmission loop. The coupler at the receiving end (i.e., the second coupler) also receives the analog transmission signal based on the principle of electromagnetic induction coupling and is ultimately input to the analog signal processing circuit at the receiving end (i.e., in the demodulation circuit). The analog signal processing circuit at the receiving end may include an analog-to-digital converter, a bandpass filter, and a signal amplifier in the demodulation circuit.

[0098] According to an embodiment of the present invention, both the first coupler and the second coupler have a central hole, and the two ends of the plastic-coated cable pass through the central holes of the first coupler and the second coupler respectively. The transmission circuit, which is composed of the plastic-coated cable, two electrode plates at both ends of the plastic-coated cable, and seawater, is electromagnetically coupled to the first coupler. The transmission circuit is also electromagnetically coupled to the second coupler. The first coupler can receive analog transmission signals from the modulation circuit and transmit the analog transmission signals to the second coupler via the transmission circuit. The second coupler transmits the analog transmission signals to the demodulation circuit. This technique increases the distance that the transmission circuit can transmit signals, so that signals can be transmitted between the modulation circuit and the demodulation circuit, which are far apart, through the transmission circuit.

[0099] According to embodiments of the present invention, since the transmission of analog transmission signals is based on the principle of electromagnetic induction coupling and the marine environment can interfere with the analog transmission signals, the analog transmission signals will experience amplitude attenuation, phase shift, and channel noise during transmission. Therefore, in the digital signal processing circuit section of the demodulation circuit in this embodiment of the present invention, an adaptive filtering module is added to the phase-locked analog transmission signal to reduce the amplitude attenuation of the analog transmission signal during transmission and adaptively filter out noise signals. The digital signal processing circuit included in the demodulation circuit can be the adaptive filtering module, phase-locked loop sub-circuit, and code stream recovery sub-circuit included in the demodulation circuit.

[0100] The demodulation circuit functions by sequentially demodulating the analog transmission signal using a bandpass filter, signal amplifier, and analog-to-digital converter (ADC) to obtain a digital modulated signal. Then, using an adaptive filtering module, phase-locked loop (PLL) sub-circuit, and bitstream recovery sub-circuit, the digital modulated signal sampled and converted by the ADC module is restored to its original 0 / 1 bitstream data.

[0101] like Figure 2 As shown, Figure 2 The demodulation circuit shown can be used in Figure 1 The demodulation circuit shown includes: a bandpass filter, a signal amplifier, an analog-to-digital converter, an adaptive filtering module, a phase-locked loop (PLL) sub-circuit, and a code stream recovery sub-circuit.

[0102] A bandpass filter can be used to perform bandpass filtering on an analog transmission signal corresponding to a first bit value when the first bit value is received, to obtain a first analog filtered signal; and to perform bandpass filtering on analog transmission signals corresponding to a first bit value and a second bit value when the first bit value and a second bit value are received, to obtain a second analog filtered signal.

[0103] The signal amplifier can be used to amplify the first analog filtered signal to obtain a first amplified signal when a first analog filtered signal is received; and to amplify the second analog filtered signal to obtain a second amplified signal when a second analog filtered signal is received.

[0104] An analog-to-digital converter can be used to perform analog-to-digital conversion on a first amplified signal to obtain a first modulated signal when a first amplified signal is received; and to perform analog-to-digital conversion on a second amplified signal to obtain a second modulated signal when a second amplified signal is received.

[0105] The phase-locked loop (PLL) circuit may include a numerically controlled oscillator, an I-channel multiplier, a first low-pass filter, a Q-channel multiplier, a second low-pass filter, a loop multiplier, and a loop filter.

[0106] A numerically controlled oscillator can be used to generate an initial carrier signal and adjust its phase according to a time-varying signal to obtain an adjusted carrier signal, which includes a target carrier signal. The initial value of the time-varying signal can be 0. If the phase difference between the adjusted carrier signal and the first modulation signal is less than a predetermined phase threshold, the adjusted carrier signal is determined as the target carrier signal.

[0107] An I-channel multiplier can be used to multiply the regulated carrier signal by the input signal to obtain the initial in-phase component. The input signal is either the second filtered signal or the first modulated signal.

[0108] The first low-pass filter is used to perform low-pass filtering on the initial in-phase component to obtain the in-phase component, wherein the in-phase component is either the first in-phase component or the second in-phase component.

[0109] A Q-channel multiplier can be used to multiply an input signal with a carrier signal that has been adjusted by a predetermined phase shift to obtain an initial quadrature component.

[0110] For example, the predetermined angle can be 90°.

[0111] The phase-locked loop circuit may also include a 90° phase shift unit, which is used to shift the regulated carrier signal by 90° and provide the regulated carrier signal after 90° phase shift to the Q-channel multiplier.

[0112] The second low-pass filter can be used to perform low-pass filtering on the initial orthogonal components to obtain the orthogonal components.

[0113] A loop multiplier can be used to multiply in-phase components with quadrature components to obtain an initial time-varying signal.

[0114] Loop filters can be used to perform loop filtering on initial time-varying signals to obtain time-varying signals.

[0115] According to an embodiment of the present invention, a numerically controlled oscillator, a 90° phase shift unit, a first low-pass filter, an I-channel multiplier, a second low-pass filter, a Q-channel multiplier, a loop multiplier, and a loop filter together constitute a phase-locked loop circuit, which can lock the phase of the output carrier of the numerically controlled oscillator and the phase of the modulation signal.

[0116] The first low-pass filter, the second low-pass filter, and the loop filter are all filters capable of implementing weighted moving average filtering; the adaptive filtering module includes filters capable of implementing weighted moving average filtering.

[0117] For example, all filters in the demodulation circuit can be FIR filters.

[0118] According to embodiments of the present invention, DPSK demodulation has strict requirements for phase linearity, while FIR filters have strict linear phase characteristics. Therefore, all filters in the demodulation circuit are FIR filters, which effectively avoids the impact of phase distortion introduced by the filters on demodulation performance, thereby ensuring the accuracy and stability of the phase information of the signal during demodulation, reducing the bit error rate, and improving the communication reliability of the system.

[0119] According to an embodiment of the present invention, the adaptive filtering module can receive control signals to control its start and stop. For example, if the adaptive filtering module receives a first control signal, it will not start; if it receives a second control signal, it will start. The adaptive filtering module also has an adaptive FIR filter, capable of training FIR filter parameters according to the LMS algorithm. If the adaptive filtering module is not started, the first modulation signal sampled by the ADC is directly input to the subsequent stage. Otherwise, the modulation signal received by the adaptive filtering module is used as the input signal, and the carrier signal generated by the numerically controlled oscillator is used as the desired signal. The output of the adaptive filtering module is adjusted according to the input signal and the desired signal (i.e., the filtering parameters of the adaptive filtering module are adjusted, thereby adjusting the output of the adaptive filtering module), to achieve the purpose of adaptive filtering.

[0120] The code stream recovery sub-circuit may include a sampling decision unit and a code inversion transformation unit.

[0121] The sampling decision unit can sample and decide on the output of the first low-pass filter to obtain the relative code of the modulated signal; the code inversion transformation unit can restore the relative code output by the sampling decision unit to the original bit stream data, thereby obtaining the demodulated signal. The demodulated signal may include a first decoded bit stream and a second decoded bit stream.

[0122] According to an embodiment of the present invention, the specific steps for signal demodulation using a demodulation circuit are as follows:

[0123] Step 1: After the adaptive filtering data transmission system starts, the first flag bit nco_locked in the phase-locked loop (PLL) sub-circuit is initialized to 0. Based on the configuration of the first flag bit nco_locked to 0, the PLL sub-circuit continuously outputs a first-level signal to the adaptive filtering module. At this time, the phase difference between the carrier signal output by the PLL sub-circuit and the first modulation signal is greater than or equal to a predetermined phase threshold. The second flag bit sin_start in the bitstream recovery sub-circuit is initialized to 0. Based on the configuration of the second flag bit sin_start to 0, the bitstream recovery sub-circuit continuously outputs a third-level signal to the adaptive filtering module. At this time, the number of consecutive first bit values ​​included in the second decoded bitstream obtained by the bitstream recovery sub-circuit is less than or equal to a predetermined number.

[0124] The control bit lms_start of the adaptive filtering module is initialized to 0, and the third flag bit lms_locked in the adaptive filtering module is also initialized to 0. Under the control of the first and third level signals, the adaptive filtering module keeps the control bit lms_start at 0, preventing it from starting and keeping the third flag bit lms_locked at 0. Simultaneously, the first modulated signal, after passing through the signal transmission channel (i.e., transmission loop), the bandpass filter in the modulation circuit, the signal amplifier, and the ADC, bypasses the adaptive filtering module and is directly input to the subsequent phase-locked loop sub-circuit. Road multiplication instrument and The multiplier is used to process the original bitstream data. A value always equal to 0 indicates that the adaptive filtering module does not need to be activated.

[0125] In the raw bitstream data In this case, the first modulated signal obtained by ADC sampling As shown in formula (3).

[0126] (3);

[0127] in, This represents the amplitude of the first modulated signal obtained by the ADC sampling. This represents the noise signal after the modulated signal has passed through the signal transmission channel.

[0128] Step 2: The CNC oscillator outputs a carrier wave with the same frequency as the modulation signal. A 90° phase shift unit can output a carrier wave with a frequency orthogonal to the modulated signal. The numerically controlled oscillator outputs a carrier wave with the same frequency as the modulation signal in step 2. It can be the initial carrier signal.

[0129] The first modulating signal has a carrier frequency equal to that of the modulating signal. Multiplication produces Road multiplier output As shown in formula (4). Road multiplier output This is the initial in-phase component.

[0130] (4);

[0131] in, = , express The amplitude of the output signal of the multiplier. This refers to the phase of the carrier wave output by the numerically controlled oscillator.

[0132] The carrier wave whose frequency is orthogonal to the first modulating signal and the modulating signal. Multiplication produces Road multiplier output As shown in formula (5). Road multiplier output These are the initial orthogonal components.

[0133] (5);

[0134] in, , express The amplitude of the output signal of the multiplier.

[0135] Step 3: Road multiplier output and Road multiplier output Each component passes through a low-pass filter, which can have a passband cutoff frequency equal to the baseband frequency. The stopband start frequency is the carrier frequency. A low-pass FIR filter. The main purpose of a low-pass filter is to remove... Frequency components.

[0136] Road multiplier output The output is in-phase component after passing through the first low-pass filter. As shown in formula (6).

[0137] (6);

[0138] in, This represents the amplitude of the in-phase component. This represents the noise within the passband of the first low-pass filter and the noise outside the passband that has not been properly filtered out.

[0139] Road multiplier output The output quadrature components are obtained after passing through the second low-pass filter. As shown in formula (7).

[0140] (7);

[0141] in, Indicates the magnitude of the orthogonal component This represents the noise within the passband of the second low-pass filter and the noise outside the passband that has not been properly filtered out.

[0142] Step 4: Convert the in-phase component of the first low-pass filter output. Quadrature components of the second low-pass filter output The input is fed into a loop multiplier and then passes through a loop filter to obtain the loop filter output. Loop filter output The initial time-varying signal is used. The loop filter ensures that the output control quantity primarily retains the phase difference. The relevant low-frequency effective components provide a stable phase adjustment signal for the subsequent numerically controlled oscillator.

[0143] The in-phase component of the first low-pass filter output can be obtained using a loop multiplier according to formula (8). Quadrature components of the second low-pass filter output Multiply to obtain the initial time-varying signal .

[0144] (8).

[0145] The time-varying signal output by the loop filter is obtained according to formula (9). .

[0146] (9);

[0147] in, Indicates the amplitude of a time-varying signal. This represents the noise within the passband of the loop filter and the noise outside the passband that has not been completely filtered out. The value is relatively small and can be ignored.

[0148] Step 5: The numerically controlled oscillator outputs based on the loop filter output. Size adjustment and The phase. When phase and first modulation signal Once the phase difference between the two phases is less than the set value LOCK_ERR, the first flag bit nco_locked is set to 1, and the second level signal is continuously output to the adaptive filtering module; otherwise, steps 2-4 are repeated until... phase and first modulation signal The phase difference between the phases is less than the set value LOCK_ERR. The set value LOCK_ERR is a predetermined phase threshold.

[0149] In this circuit, the adaptive filtering module, under the control of the third-level signal, keeps the control bit lms_start at 0, thus preventing the adaptive filtering module from starting and maintaining the third flag bit lms_locked at 0. Simultaneously, the first modulated signal, after passing through the signal transmission channel (i.e., the transmission loop), the bandpass filter in the modulation circuit, the signal amplifier, and the ADC, bypasses the adaptive filtering module and is directly input to the subsequent phase-locked loop sub-circuit. Road multiplication instrument and The multiplier at this point contains the original bitstream data. A value always equal to 0 indicates that the adaptive filtering module does not need to be activated.

[0150] Step 6: The code inversion unit will obtain the demodulated signal. The counter in the code inversion unit will count... The number of consecutive zeros; when this number exceeds a predetermined number, it indicates the current first modulation signal. Since the phase remains unchanged, the adaptive filtering module can be activated. The code stream recovery sub-circuit sets sin_start to 1 and continuously outputs the fourth-level signal to the adaptive filtering module. The demodulated signal obtained by the code inversion conversion unit in step 6... This is the second decoded bitstream.

[0151] Step 7: When nco_locked and sin_start are both set to 1, the adaptive filtering module receives the second level signal and the fourth level signal. Under the control of the second level signal and the fourth level signal, the control bit lms_start of the adaptive filtering module is set to 1, so that the adaptive filtering module starts to be enabled. The third flag bit lms_locked is kept at 0. According to the LMS principle, the filtering parameters of the FIR filter in the adaptive filtering module are trained using formulas (10) to (14).

[0152] When training the filtering parameters of the FIR filter in the adaptive filtering module, the input modulation signal of the adaptive filtering module is... It is the first modulated signal obtained by ADC sampling. As shown in formula (10).

[0153] (10).

[0154] The desired signal used by the adaptive filtering module When phase and first modulation signal When the phase difference between them is less than the set value LOCK_ERR, the numerically controlled oscillator outputs... As shown in formula (11).

[0155] when phase and first modulation signal When the phase difference between them is less than the set value LOCK_ERR, the numerically controlled oscillator outputs... In With formulas (2) and (3) The difference is small, approximately equal, so that after the filtered signal (i.e., the second filtered signal) containing valid data is input into the phase-locked loop circuit, it can be determined according to... Demodulate the correct in-phase component (i.e., the first in-phase component), and simultaneously... After being used as the desired signal, the target filtering parameters of the adaptive filtering mode can be adjusted according to the desired signal to effectively filter out marine environmental noise. Therefore, in formula (11), the target filtering parameters of the adaptive filtering mode can be directly used to effectively filter out marine environmental noise. Alternative In .

[0156] (11).

[0157] Among them, the expected signal The phase of the signal has been basically modulated by the input signal of the adaptive filter module after steps 2-5. equal.

[0158] Output signal of adaptive filtering module It is the input modulation signal The output of the FIR filter in the adaptive filtering module is shown in formula (12).

[0159] (12);

[0160] Where N is the order of the FIR filter in the adaptive filtering module. These are the coefficients of the FIR filter in the adaptive filtering module. This is the update period for the coefficients of the FIR filter in the adaptive filtering module. p represents the coefficient number of the FIR filter.

[0161] Error calculated by the adaptive filtering module For: when phase and first modulation signal When the phase difference between them is less than the set value LOCK_ERR, the numerically controlled oscillator module outputs... The output of the FIR filter in the adaptive filtering module For the error between them, please refer to formula (13).

[0162] (13).

[0163] Under discrete sampling, the update expression of the coefficients of the FIR filter in the adaptive filtering module is shown in formula (14).

[0164] (14);

[0165] in, Indicates the current sampling time. Indicates the next sampling time. Indicates the step size for adjusting the filter coefficients. This represents the error calculated by the adaptive filtering module at the current sampling time.

[0166] Step 8: When the error When the value is less than the set value LMS_ERR (i.e., the predetermined error), the adaptive filtering module sets the third flag bit lms_locked to 1, indicating that the coefficient training of the FIR filter in the adaptive filtering module is complete. At this time, the modulation circuit can start sending valid data signals, i.e. The beginning indicates valid data.

[0167] Step 9: The modulated signal with valid data (i.e., the second modulated signal) is output after passing through the adaptive filtering module. The output of the adaptive filtering module With the output of the CNC oscillator Enter The multiplier performs multiplication, and the result is output after passing through the first low-pass filter. At this point, Road multiplier output As shown in formula (15). The adaptive filtering module outputs in step 9. This is the second filtered signal.

[0168] (15);

[0169] in This represents the ideal output of the second modulated signal after passing through the adaptive filtering module. This represents a small amount of residual noise signal at the output of the adaptive filtering module. The signal strength of this residual noise signal is so small that it can be ignored and is omitted. At this point, the first low-pass filter outputs... As shown in formula (16).

[0170] (16).

[0171] Step 10: In-phase component of the first low-pass filter output After sampling and decision-making, the relative code of the original bitstream data can be obtained. After performing the code inverse transformation, the original bit stream data can be obtained. The code inverse transformation process is shown in formula (17).

[0172] (17);

[0173] in, This is for decoding the bitstream.

[0174] Figure 3 A schematic diagram showing the result of the demodulation circuit processing the modulated signal in an adaptive filtering data transmission system according to an embodiment of the present invention is illustrated.

[0175] The demodulation circuit performs signal filtering and demodulation on the modulated signal as follows: Figure 3 As shown. Figure 3 In the diagram, `adc_data` is the digital modulation signal output by the ADC, with a data width of 8 bits; `nco_sin` is the carrier signal output by the numerically controlled oscillator, with a data width of 24 bits; `adc_filtered` is the output of the adaptive filtering module, with a data width of 24 bits; `lms_locked` is the value of the third flag bit used to determine whether the adaptive filtering is complete, with a data width of 1 bit. Setting the third flag to 1 indicates that the FIR filter in the adaptive filtering module has completed training and entered a stable working state; `mix_I` is the output of the I-channel multiplier, with a data width of 24 bits; `fir_I` is the output of the first low-pass filter, with a data width of 24 bits. The output of the I-channel multiplier also represents the relative code value of the demodulated original bitstream data and is used for subsequent decision processing.

[0176] based on Figure 3 The results show that the present invention can automatically determine the filtering parameters of the FIR filter in the adaptive filtering module, and then generate an FIR filter that adapts to the signal transmission channel, thereby solving the problems of low communication rate, high demodulation error rate and susceptibility to marine environmental noise in underwater data transmission systems in related technologies.

[0177] According to embodiments of the present invention, the specific division method of the adaptive filtering data transmission system provided in these embodiments can be selected according to actual conditions and is not limited herein. For example, it can also be classified according to function. Figure 2The adaptive filtering data transmission system shown is divided into three parts: analog signal processing circuit, signal transmission channel, and digital signal processing circuit. The digital signal processing circuit may include a digital frequency synthesizer, a symbol conversion module, a multiplier, an adaptive filtering module, a phase-locked loop (PLL) sub-circuit, and a code stream recovery sub-circuit. The signal transmission channel may include a first coupler, a second coupler, a plastic-coated cable, and two electrode plates connected to the two ends of the plastic-coated cable, respectively, and seawater, utilizing the principle of electromagnetic induction coupling to achieve data transmission. The analog signal processing circuit may include a digital-to-analog converter (DAC), a bandpass filter, a signal amplifier, and an analog-to-digital converter (ADC). The analog signal processing circuit may include analog signal processing circuits at the modulation signal transmitting end and analog signal receiving end. The analog signal processing circuit at the modulation signal transmitting end converts the digital modulation signal into an analog modulation signal and performs amplification and filtering. The analog signal processing circuit at the modulation signal receiving end filters and amplifies the analog transmission signal passing through the signal transmission channel, and samples it through the ADC to convert the analog transmission signal into a digital modulation signal, such as a first modulation signal and a second modulation signal.

[0178] The digital signal processing circuit of this invention implements modulation and demodulation of the original 0 / 1 bitstream data signal based on the DPSK principle, FPGA hardware, and LMS adaptive filtering algorithm. Specifically, the digital signal processing circuit employs the DPSK modulation and demodulation method.

[0179] According to embodiments of the present invention, the functions that the devices and modules included in the analog signal processing circuit, signal transmission channel, and digital signal processing circuit can achieve are described in [reference needed]. Figure 1 and Figure 2 For the sake of simplicity, the relevant descriptions will not be repeated here.

[0180] According to an embodiment of the present invention, the adaptive filtering module dynamically adjusts the FIR filter coefficients using the LMS algorithm, effectively suppressing marine environmental noise. Therefore, the present invention can adaptively compensate for signal attenuation, filter out channel interference, significantly reduce the bit error rate, and improve the reliability and data transmission efficiency of underwater communication.

[0181] Based on the aforementioned adaptive filtering data transmission system, embodiments of the present invention provide an adaptive filtering data transmission method.

[0182] Figure 4 A flowchart of an adaptive filtering data transmission method according to an embodiment of the present invention is shown.

[0183] Figure 4 The adaptive filtering data transmission method shown can be applied to the adaptive filtering data transmission system described above.

[0184] like Figure 4As shown, the data transmission method for adaptive filtering may include operations S410 to S450.

[0185] In operation S410, the adaptive filtering module, under the control of the first control signal, provides the first modulation signal to the phase-locked loop circuit. The first modulation signal is obtained by demodulating the analog transmission signal corresponding to the first bit value.

[0186] In operation S420, the phase-locked loop (PLL) sub-circuit adjusts the phase of the initial carrier signal using the first modulation signal to obtain the target carrier signal. The phase difference between the target carrier signal and the first modulation signal is less than a predetermined phase threshold.

[0187] In operation S430, under the control of the second control signal, the adaptive filtering module adjusts the filtering parameters in the adaptive filtering module according to the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal based on the filtering parameters in the adaptive filtering module, to obtain the target filtering parameters; based on the target filtering parameters, the second modulated signal is subjected to weighted moving average filtering to obtain the second filtered signal. The second modulated signal is obtained by demodulating the analog transmission signal corresponding to the first bit value and the second bit value.

[0188] In operation S440, the phase-locked loop circuit uses the target carrier signal to coherently demodulate the second filtered signal to obtain the first in-phase component.

[0189] During operation S450, the code stream recovery sub-circuit decodes the first in-phase component according to a predetermined decoding rule to obtain the first decoded code stream.

[0190] It should be noted that the data transmission method part of adaptive filtering in the embodiments of the present invention corresponds to the data transmission system part of adaptive filtering in the embodiments of the present invention. For a detailed description of the data transmission method part of adaptive filtering, please refer to the data transmission system part of adaptive filtering, which will not be repeated here.

[0191] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions. Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or pairings fall within the scope of this invention.

[0192] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of the invention is defined by the appended embodiments and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A data transmission system with adaptive filtering, characterized in that, include: The demodulation circuitry, located below sea level, includes: An adaptive filtering module is configured to provide a first modulation signal to a phase-locked loop (PLL) circuit under the control of a first control signal; and, under the control of a second control signal, adjust the filtering parameters in the adaptive filtering module according to the error between a target carrier signal and a first filtered signal obtained by filtering the first modulation signal based on the filtering parameters in the adaptive filtering module, to obtain target filtering parameters; and perform weighted moving average filtering on a second modulation signal based on the target filtering parameters to obtain a second filtered signal, wherein the first modulation signal is obtained by demodulating an analog transmission signal corresponding to a first bit value, and the second modulation signal is obtained by demodulating an analog transmission signal corresponding to a first bit value and a second bit value. The phase-locked loop sub-circuit is used to adjust the phase of the initial carrier signal using the first modulation signal to obtain the target carrier signal, wherein the phase difference between the target carrier signal and the first modulation signal is less than a predetermined phase threshold; and to coherently demodulate the second filtered signal using the target carrier signal to obtain a first in-phase component. The bitstream recovery sub-circuit is used to decode the first in-phase component according to a predetermined decoding rule to obtain the first decoded bitstream.

2. The data transmission system according to claim 1, characterized in that, Also includes: The system comprises a first coupler, a second coupler, a plastic-coated cable, and two electrode plates connected to both ends of the plastic-coated cable, all positioned below sea level. Both the first coupler and the second coupler have a central hole. The two ends of the plastic-coated cable pass through the central holes of the first coupler and the second coupler, respectively. The transmission circuit formed by the plastic-coated cable, the two electrode plates at both ends of the plastic-coated cable, and seawater is electromagnetically coupled to the first coupler. The transmission circuit is also electromagnetically coupled to the second coupler. The first coupler is used to receive an analog transmission signal from the modulation circuit and transmit the analog transmission signal to the second coupler via the transmission loop; The second coupler is used to transmit the analog transmission signal to the demodulation circuit.

3. The data transmission system according to claim 1 or 2, characterized in that, The phase-locked loop (PLL) circuit is further configured to: output a first level signal when the phase difference between the initial carrier signal and the first modulation signal is greater than or equal to a predetermined phase threshold; and output a second level signal when the phase difference between the target carrier signal and the first modulation signal is less than the predetermined phase threshold, thereby coherently demodulating the first modulation signal using the target carrier signal to obtain a second in-phase component, wherein the amplitude of the second level signal is greater than the amplitude of the first level signal. The code stream recovery sub-circuit is further configured to: decode the second in-phase component according to a predetermined decoding rule to obtain a second decoded code stream; output a third level signal when the number of consecutive first bit values ​​included in the second decoded code stream is less than or equal to a predetermined number; and output a fourth level signal when the number of consecutive first bit values ​​included in the second decoded code stream is greater than the predetermined number, wherein the amplitude of the fourth level signal is greater than the amplitude of the third level signal. The adaptive filtering module is further configured to: provide the first modulation signal to the phase-locked loop circuit when the first level signal and / or the third level signal are received; and confirm the receipt of the second control signal when the second level signal and the fourth level signal are received, and perform an operation on the modulation signal input to the adaptive filtering module under the control of the second control signal. The second control signal includes the second level signal and the fourth level signal.

4. The data transmission system according to claim 3, characterized in that, The phase-locked sub-circuit includes: A numerically controlled oscillator is used to generate the initial carrier signal and adjust the phase of the initial carrier signal according to a time-varying signal to obtain an adjusted carrier signal, wherein the adjusted carrier signal includes the target carrier signal; An I-channel multiplier is used to multiply the adjusted carrier signal with the input signal to obtain an initial in-phase component, wherein the input signal is the second filtered signal or the first modulated signal; A first low-pass filter is used to perform low-pass filtering on the initial in-phase component to obtain an in-phase component, wherein the in-phase component is either the first in-phase component or the second in-phase component. A Q-channel multiplier is used to multiply the input signal with a carrier signal adjusted by a predetermined phase shift to obtain an initial quadrature component; A second low-pass filter is used to perform low-pass filtering on the initial orthogonal components to obtain orthogonal components; A loop multiplier is used to multiply the in-phase component and the quadrature component to obtain the initial time-varying signal; A loop filter is used to perform loop filtering on the initial time-varying signal to obtain the time-varying signal.

5. The data transmission system according to claim 4, characterized in that, The first low-pass filter, the second low-pass filter, and the loop filter are all filters capable of implementing weighted moving average filtering; The adaptive filtering module includes a filter capable of implementing weighted moving average filtering.

6. The data transmission system according to claim 1 or 2, characterized in that, The phase-locked sub-circuit is also used for: The phase of the current target carrier signal is adjusted using the current second filter signal to obtain the adjusted target carrier signal, which is then used to coherently demodulate the next second filter signal.

7. The data transmission system according to claim 1 or 2, characterized in that, The demodulation circuit further includes: A bandpass filter is used to perform bandpass filtering on the analog transmission signal corresponding to the first bit value when the first bit value is received, to obtain a first analog filtered signal; and to perform bandpass filtering on the analog transmission signal corresponding to the first bit value and the second bit value when the first bit value and the second bit value are received, to obtain a second analog filtered signal. A signal amplifier is used to amplify the first analog filtered signal upon receiving the first analog filtered signal to obtain a first amplified signal; and to amplify the second analog filtered signal upon receiving the second analog filtered signal to obtain a second amplified signal. An analog-to-digital converter is used to perform analog-to-digital conversion on the first amplified signal when the first amplified signal is received, to obtain the first modulated signal; and to perform analog-to-digital conversion on the second amplified signal when the second amplified signal is received, to obtain the second modulated signal.

8. The data transmission system according to claim 1 or 2, characterized in that, Also includes: The modulation circuit, located on the sea surface, is used to perform differential phase shift keying modulation on the input code stream corresponding to the first bit value when it receives the input code stream corresponding to the first bit value, so as to obtain the analog transmission signal corresponding to the first bit value. Upon receiving an input code stream corresponding to the first bit value and the second bit value, differential phase shift keying modulation is performed on the input code stream corresponding to the first bit value and the second bit value to obtain an analog transmission signal corresponding to the first bit value and the second bit value.

9. The data transmission system according to claim 1 or 2, characterized in that, Under the control of the second control signal, the adaptive filtering module adjusts the filtering parameters of the adaptive filtering module according to the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal based on the filtering parameters in the adaptive filtering module, to obtain the target filtering parameters, including: Repeat the following operation until the error is less than the predetermined error: The first modulation signal of the i-th round is filtered based on the filtering parameters of the i-th round in the adaptive filtering module to obtain the reference signal of the i-th round, where i is a positive integer; Calculate the error between the target carrier signal and the reference signal in the i-th round to obtain the error in the i-th round; If the error in the i-th round is greater than or equal to the predetermined error, the filtering parameters in the i-th round of the adaptive filtering module are adjusted according to the error in the i-th round. The adjusted filtering parameters are used as the filtering parameters for the next round, incremented by i, and the operation of filtering the first modulation signal of the i-th round based on the filtering parameters in the i-th round of the adaptive filtering module is returned.

10. An adaptive filtering data transmission method, applied to the adaptive filtering data transmission system according to any one of claims 1 to 9, characterized in that, The data transmission method includes: Under the control of the first control signal, the adaptive filtering module provides the first modulation signal to the phase-locked loop circuit, wherein the first modulation signal is obtained by demodulating the analog transmission signal corresponding to the first bit value; The phase-locked loop circuit uses the first modulation signal to adjust the phase of the initial carrier signal to obtain the target carrier signal, wherein the phase difference between the target carrier signal and the first modulation signal is less than a predetermined phase threshold. Under the control of the second control signal, the adaptive filtering module adjusts the filtering parameters in the adaptive filtering module according to the error between the target carrier signal and the first filtered signal obtained by filtering the first modulated signal based on the filtering parameters in the adaptive filtering module, to obtain target filtering parameters; and performs weighted moving average filtering on the second modulated signal based on the target filtering parameters to obtain a second filtered signal, wherein the second modulated signal is obtained by demodulating the analog transmission signal corresponding to the first bit value and the second bit value. The phase-locked loop sub-circuit uses the target carrier signal to coherently demodulate the second filtered signal to obtain the first in-phase component; The bitstream recovery sub-circuit decodes the first in-phase component according to a predetermined decoding rule to obtain the first decoded bitstream.

Images