Shipborne underwater acoustic ranging and receiving system and method based on synchronous gain cooperative control

Abstract

This invention belongs to the field of underwater acoustic ranging, specifically relating to a shipborne underwater acoustic ranging receiving system and method based on synchronous gain cooperative control. The system includes: a signal acquisition and conversion module, a receiving, processing, and cooperative control module, and a host computer monitoring module. The signal acquisition and conversion module acquires the ranging acoustic signal and converts it into a digital sampled signal. The receiving, processing, and cooperative control module receives the digital sampled signal and generates I / Q baseband components, performs continuous phase compensation, constructs a signal quality index based on the compensated signal, and inputs the signal quality index to a decision unit. When a trigger is established, the gain control unit and the synchronous control unit perform coordinated control. During non-trigger periods, the current state is maintained, and ranging calculation begins. This invention enables the receiver to stably complete time-of-arrival extraction and distance calculation in complex environments, improving ranging accuracy and reducing system power consumption.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic ranging, specifically relating to a shipborne underwater acoustic ranging and receiving system and method based on synchronous gain cooperative control. Background Technology

[0002] Shipborne underwater acoustic ranging and receiving systems belong to the field of shipborne underwater acoustic measurement and ranging technology. They are primarily used to measure the distance between shipborne platforms and underwater platforms during maritime navigation or operations, such as the slant distance between a ship and an AUV, ROV, underwater transponder, acoustic beacon, or seabed operation equipment. This provides distance information for navigation assistance, target positioning, formation coordination, and operational safety. In engineering practice, the underwater platform typically transmits or responds to a ranging reference acoustic signal in a known format. The shipborne receiver, after acquiring the signal via hydrophones, sequentially performs controllable gain amplification, filtering, and analog-to-digital conversion. In the digital domain, it performs down-conversion to generate baseband components, carrier synchronization and phase compensation, and related processing to extract the propagation delay and output the distance result.

[0003] However, in shipboard scenarios, the Doppler effect and rapid phase disturbance caused by platform motion and attitude changes, coupled with deep fading and abrupt changes in signal amplitude due to sea state and multipath, cause dynamic range problems and coherence quality problems to appear coupled. Existing technologies mostly operate automatic gain control and synchronization loop independently, lacking a unified criterion and cooperative control mechanism that can simultaneously reflect "coherence reliability" and "dynamic range status". This can easily lead to correlation peak distortion caused by strong signal saturation, unusable weak signals, frequent synchronization updates or loss of lock, and ultimately cause jitter and poor repeatability in ranging output. Summary of the Invention

[0004] This invention overcomes the above-mentioned defects and provides a shipborne underwater acoustic ranging and receiving system and method based on synchronous gain cooperative control. It solves the problems of strong signal saturation correlation peak distortion, weak signal unavailability, and ranging output jitter and poor repeatability caused by frequent synchronization updates or loss of lock in the prior art, thereby improving the ranging accuracy of the system and reducing the power consumption of the system.

[0005] To achieve the above objectives, the shipborne underwater acoustic ranging and receiving method based on synchronous gain cooperative control of the present invention includes the following steps:

[0006] S1. Ranging signal acquisition, conversion, and dynamic range shaping, outputting digital sampled signal;

[0007] S2. Perform digital down-conversion and quadrature demodulation on the digital sampled signal to obtain I / Q baseband components, and set the synchronization status register to save the synchronization status parameters;

[0008] S3. Construct a continuous phase compensation link, perform continuous phase compensation on the I / Q baseband components based on the synchronization state parameters, and output the compensated baseband signal;

[0009] S4. Construct a signal quality index based on the compensated baseband signal, input the signal quality index into the decision unit, and have the decision unit complete the threshold decision and output a trigger signal;

[0010] S5. If the trigger signal is negative, maintain the current synchronization state and gain state, and directly enter the ranging calculation unit; if the trigger signal is positive, then the synchronization control unit and gain control unit are executed in conjunction.

[0011] S6. The distance measurement and calculation unit performs arrival time extraction and distance calculation to output distance measurement results. The data storage unit records the distance measurement results and key process data. The host computer monitoring module summarizes the status information and outputs monitoring parameters.

[0012] Furthermore, in step S1, the specific process of signal acquisition and conversion is as follows:

[0013] S101, the hydrophone receives the ranging reference signal and completes the sound-to-electric conversion, outputting an analog electrical signal. ;

[0014] S102, Let the gain control word be... Gain mapping is The amplified signal is:

[0015] ;

[0016] S103. The amplified signal is then bandpass filtered to suppress out-of-band noise and low-frequency interference:

[0017] ;

[0018] S104, Analog-to-Digital Conversion Module with Sampling Rate right sampling:

[0019] ;

[0020] S105. To achieve engineering protection and gain control input, the analog-to-digital conversion module displays the statistical window. Internal calculation of saturation count:

[0021] ,

[0022] in, For ADC warning threshold, window length The data points are set to 1024–4096, with corresponding durations of 20–100 ms. To avoid misjudgments due to occasional spikes, a proportional criterion is used. When this occurs, saturation protection is triggered, where, Take 0.05%–0.5%.

[0023] Further, in step S3, the continuous phase compensation formula is:

[0024] ,

[0025] Where m represents the discrete sampling point number. Let represent the compensation phase used for continuous phase compensation at the m-th sampling point. Indicates the phase correction amount. This represents the frequency offset estimator. This is the frequency offset drift rate. Baseband sampling rate;

[0026] The compensation output is:

[0027] ,

[0028] in, This represents the complex baseband signal after phase compensation. This represents the complex baseband signal before compensation.

[0029] Furthermore, in step S4, the specific process of constructing signal quality indicators and having the decision unit complete the decision output is as follows:

[0030] S41, Baseband signal After completing symbol sampling and hard decision, we obtain Based on this, the residual phase error is constructed as follows:

[0031] ,

[0032] in, The result of the judgment is symbolic;

[0033] S42. Calculate the sensitivity of second-order difference reinforcement to fast perturbations:

[0034] ;

[0035] S43. Accumulate trigger energy within the window length W:

[0036] ;

[0037] S44. The decision unit adopts a joint constraint of threshold and maximum interval. Output is triggered when the threshold is exceeded or the trigger interval reaches its upper limit. Adaptive form adopted:

[0038] ;

[0039] in k represents the threshold scaling factor, used to adjust the sensitivity of the trigger decision. A larger k results in a higher threshold and sparser triggering, while a smaller k results in a lower threshold and more sensitive triggering. Setting it to... .

[0040] Furthermore, in step S5, the operation of the synchronization control unit is as follows:

[0041] S501. After the trigger is established, the synchronization control unit enters the refresh phase, in the refresh window. Internal estimation of phase correction and frequency offset correction; the phase correction can be taken as the mean of the residual phase:

[0042] ,

[0043] The frequency offset correction is measured by the mean of the phase difference:

[0044] ,

[0045] The refresh window length is set to 128–1024 points, corresponding to a duration of 5–50 ms. This is to suppress abnormal updates caused by phase wrapping. exist Inner expansion processing;

[0046] S502, Synchronization status is updated in steps:

[0047] ,

[0048] ,

[0049] in, Take values ​​between 0.1 and 0.5. Take a value of 0.05–0.2;

[0050] S503, After the refresh is complete, reset the trigger timer and accumulate the trigger count:

[0051] ,

[0052] in, Indicates the cumulative number of times the event has been triggered;

[0053] S504. The locked state is determined jointly by residual phase stability and trigger frequency. Locking is considered complete when the residual phase variance is below a threshold and the trigger frequency does not exceed the upper limit. The phase variance threshold is set to 0.02. –0.10 The trigger frequency is capped at 10–60 times per minute;

[0054] The specific working process of the gain control unit is as follows:

[0055] S511, Root mean square of amplitude statistics:

[0056] ,

[0057] in, This is represented as the baseband sampling sequence within the statistical window Ω, i.e., the compensated complex baseband signal;

[0058] S512, Let the target amplitude range be... Set according to full-scale ratio:

[0059] ,

[0060] in, This represents the full-scale amplitude of the analog-to-digital converter (ADC). This is the lower limit scaling factor, used to set the lower limit of the target amplitude range. Set as , This is the upper limit scaling factor, used to set the upper limit of the target amplitude range. Set as ;

[0061] S513. The gain control strategy is divided into three modes with priorities: saturation protection takes precedence over collaborative fine-tuning, and collaborative fine-tuning takes precedence over weak signal recovery. The three modes are as follows:

[0062] (1) Saturation protection: If saturation counting or Then it enters the fast gain reduction module:

[0063] ,

[0064] in, This represents the gain control word, used to control the gain of the variable gain amplifier in the receive link. This indicates the fast gain reduction step size, used to quickly pull the amplitude back to the safe area when saturation is detected. It has the highest priority and is set to 6 dB.

[0065] (2) Weak signal recovery: If If there is no saturation, then proceed to the gradual increase gain module:

[0066] ,

[0067] in, This indicates the gain increment step size in weak signal recovery mode, set to 1 dB;

[0068] (3) Triggered Coordination Fine-tuning: When the triggering event is established and not saturated, in order to obtain a more stable dynamic range within the synchronous refresh window, the target median is adjusted. Make small, minor adjustments:

[0069] ,

[0070] in, This indicates the step size for triggering coordinated fine-tuning, used to perform small-step tracking corrections to the gain within the synchronous refresh window, and is set to 1 dB; the fine-tuning period is executed once for each trigger.

[0071] Furthermore, in step S6, the ranging calculation module calculates the baseband signal after compensation. Perform matched filtering to estimate arrival delay, and set the reference template as follows. ,but

[0072] ,

[0073] in, This represents the output of the matched filter between the compensated baseband signal and the reference template. Indicates delay Reference template sequence The complex conjugate;

[0074] Use the position with the largest correlation amplitude as the time delay estimate:

[0075] ,

[0076] One-way distance measurement is:

[0077] ,

[0078] Two-way distance measurement is:

[0079] ,

[0080] Where c represents the speed of sound.

[0081] To realize the above-mentioned shipborne acoustic ranging and receiving method based on synchronous gain cooperative control, this application also proposes the following shipborne acoustic ranging and receiving system based on synchronous gain cooperative control, including:

[0082] Signal acquisition and conversion module, receiving, processing and collaborative control module, host computer monitoring module;

[0083] The signal acquisition and conversion module is connected to the receiving, processing and collaborative control module, which converts the ranging reference acoustic signal into a digital sampling signal and sends the digital sampling signal into the receiving, processing and collaborative control module.

[0084] The receiving processing and cooperative control module includes an I / Q baseband generation unit, a continuous phase compensation unit, a signal quality triggering unit, a decision unit, a cooperative control branch, and a ranging calculation unit;

[0085] The I / Q baseband generation unit generates I / Q baseband components from the digital sampling signal and sets a synchronization status register to store synchronization status parameters.

[0086] The continuous phase compensation unit performs continuous phase compensation on the I / Q baseband components based on the synchronization state parameters, maintains the baseband phase continuity and coherent accumulation capability during non-triggered periods of the system, and provides a phase-controlled baseband signal.

[0087] The signal quality triggering unit extracts the decision guidance residual phase from the baseband signal and constructs a quality index.

[0088] The decision unit performs threshold judgment and decision output on the quality index. If the decision output is yes, it enters the collaborative control branch; if the decision output is no, it maintains the current synchronization state and gain state and directly enters the ranging calculation unit.

[0089] The collaborative control branch includes a gain control unit and a synchronization control unit. When the decision unit outputs "yes", the gain control unit performs a level adjustment on the controllable gain amplification unit in the signal acquisition and conversion module. At the same time, the synchronization control unit updates the synchronization status parameters so that the continuous compensation unit obtains the updated compensation basis.

[0090] The ranging calculation unit performs arrival time extraction and distance calculation on the compensated baseband signal and outputs the ranging result.

[0091] The host computer monitoring module receives the ranging results and outputs monitoring information for status assessment, maintenance decision-making, and fault location.

[0092] Furthermore, the signal acquisition and conversion module also includes a hydrophone, a bandpass filter unit, and an analog-to-digital converter unit; the hydrophone acquires the ranging reference acoustic signal and completes the acoustic-to-electric conversion; the controllable gain amplification unit is used for signal amplitude shaping to adapt to the dynamic range of the subsequent stage; the bandpass filter unit suppresses out-of-band interference; and the analog-to-digital converter unit is used for sampling, quantizing, and outputting digital sampling signals.

[0093] Furthermore, the host computer monitoring module includes a running monitoring unit and a monitoring output unit; the running monitoring unit collects the system running status and key process quantities; the monitoring output unit outputs monitoring information such as lock status, trigger count, gain level, and saturation count.

[0094] Compared with the prior art, the advantages of the present invention are as follows:

[0095] This invention addresses the problems of dynamic range mismatch, coherence degradation, clipping saturation, and loss-of-lock propagation caused by the coupling of large-range fluctuations in input amplitude and rapid phase disturbances in shipborne underwater acoustic ranging receivers. It proposes a gain-synchronization cooperative control mechanism based on residual phase quality criteria. This mechanism uses decision-oriented residual phase to construct signal quality triggers, enabling system control decisions to directly align with coherence reliability requirements. It can promptly identify critical mismatch states such as seemingly normal amplitudes but degraded phases, and phase lockability issues but link saturation. This avoids the misjudgments and ineffective adjustments of traditional independent AGC and fixed-period synchronous updates in complex sea conditions.

[0096] This invention constructs a hierarchical operation architecture for the continuous phase compensation unit under normal operation and synchronous state update under triggered conditions. During non-triggered periods, it relies on continuous phase compensation to maintain the continuity of baseband phase and coherent accumulation capability. When a triggered event occurs, this invention links synchronous refresh and front-end gain adjustment in the same closed loop, and combines continuous phase compensation to achieve a hierarchical control effect of low-overhead operation most of the time and rapid correction during degradation. Technically, it simultaneously suppresses correlation peak distortion and irreversible phase disturbance caused by strong signal clipping, as well as ranging unavailability caused by deep fading of weak signals, reducing the probability of loss of lock and the duration of abnormality, and improving the stability, consistency and availability of ranging output.

[0097] In summary, this invention improves ranging accuracy and reduces system power consumption. Furthermore, by combining the operation monitoring unit and the monitoring output unit to output key quantities such as lock status, trigger count, gain level, and saturation count, this invention enables the system to possess observable, diagnosable, and maintainable engineering attributes, making it suitable for long-term shipboard monitoring and embedded implementation. Attached Figure Description

[0098] Figure 1 This is a flowchart of the shipborne underwater acoustic ranging and receiving system of the present invention;

[0099] Figure 2 This is a flowchart of the synchronization control unit of the present invention;

[0100] Figure 3 This is a flowchart of the gain control unit of the present invention. Detailed Implementation

[0101] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0102] Example 1:

[0103] This invention addresses engineering scenarios involving underwater acoustic ranging of underwater targets or collaborative platforms from a shipborne platform. The ranging object is the distance between the shipborne platform and underwater vehicles, towed bodies, base stations, or other shipborne platforms. The ranging reference signal is a phase-coherent modulated signal, using a training sequence with a known frame structure to support matched filtering for time-of-arrival estimation and coherent phase tracking. For ease of engineering implementation and real-time processing, a frame is defined as a processing unit of the ranging reference signal, with a duration of [duration missing]. The number of baseband sampling points is ,in, A time of 20-100 ms is acceptable, with a baseband sampling rate. It is determined by the sampling rate and the extraction factor.

[0104] The shipborne underwater acoustic ranging and receiving method based on synchronous gain cooperative control provided by this invention is as follows:

[0105] 1. Acquire ranging reference signals and complete signal conversion.

[0106] The hydrophone receives the ranging reference signal and performs sound-to-electric conversion, outputting an analog electrical signal. The signal is amplified to dynamically shape its range. From an engineering perspective, this is used to avoid two extremes: first, the signal is too weak, which prevents the back-end decision and matched filtering from establishing a stable peak value; second, the signal is too strong, which causes the amplifier or analog-to-digital converter to saturate, resulting in clipping distortion and introducing irreversible harmonics and phase disturbances.

[0107] Let the gain control word be Gain mapping is The amplified signal is:

[0108] ,

[0109] The amplified signal is then bandpass filtered to suppress out-of-band noise and low-frequency interference, as shown in the following formula:

[0110] ,

[0111] With sampling rate right sampling:

[0112] ,

[0113] To achieve engineering protection and gain control input, the analog-to-digital converter module uses a statistical window. Internal calculation of saturation count:

[0114] ,

[0115] in, The ADC warning threshold can be set to 0.95–1.00 times the full-scale range; window length Points ranging from 1024 to 4096 are selected, corresponding to durations of 20 to 100 ms. To avoid misjudgment due to occasional spikes, a proportional criterion is used.

[0116] ,

[0117] Trigger saturation protection. Take 0.05%–0.5%.

[0118] With the above design, the system can reliably indicate whether it is close to saturation at the front end, which makes it easier for the subsequent gain control unit to quickly converge to the usable dynamic range and reduce phase distortion and ranging anomalies caused by saturation.

[0119] 2. The output sampled signal is digitally down-converted and quadrature demodulated to obtain the I / Q baseband signal, and the synchronization status parameters are saved in the synchronization status register.

[0120] The I / Q baseband generation unit performs mixing, low-passing, and decimation on the sampled signal to obtain a complex baseband signal, providing a unified input for continuous phase compensation and coherent ranging. This processing transfers the phase disturbances and Doppler effects under the high-frequency carrier to the controllable baseband domain, while reducing the computational load of subsequent stages through decimation, thus meeting the computing power and power consumption constraints of embedded real-time implementation.

[0121] Let the frequency of the numerically controlled oscillator be... Its output is:

[0122] ,

[0123] Frequency mixing yields:

[0124] ,

[0125] After low-pass filtering and decimation, the following was obtained:

[0126] ,

[0127] in, It is 4–16; Let be the baseband sampling rate. Then the I / Q components are:

[0128] ,

[0129] To support continuous compensation and triggered refresh, the system establishes a synchronization status register:

[0130] ,

[0131] in, Indicates the phase correction amount. This represents the frequency offset estimator. This is the frequency offset drift rate. To trigger the timer, This is a locked status flag. Initially set... , , , , .

[0132] The introduction of registers allows the synchronization control unit to operate by updating the state, rather than having to perform complex estimations for each sampling point, thus structurally reducing the frequency of synchronization updates and the complexity of implementation.

[0133] 3. The continuous phase compensation unit performs phase compensation on the I / Q baseband signals according to the synchronization state parameters.

[0134] The continuous phase compensation unit performs phase rotation compensation on the complex baseband signal based on the synchronization state register, enabling the system to maintain coherence and detectability most of the time without needing to refresh the synchronization state frequently. The core problem addressed by this mechanism is that the motion of the shipborne platform and the superposition of multipath paths cause the phase to drift continuously over time. If high-overhead synchronization updates are performed every frame, it will easily lead to increased computational burden and power consumption; if no updates are performed, it will lead to failure of coherent accumulation and unstable ranging peak values.

[0135] The compensation phase can be generated in the following form:

[0136] ,

[0137] Where m represents the discrete sampling point number. Let represent the compensation phase used for continuous phase compensation at the m-th sampling point. Indicates the phase correction amount. This represents the frequency offset estimator. This is the frequency offset drift rate. Baseband sampling rate;

[0138] The compensation output is:

[0139] ,

[0140] in, This represents the complex baseband signal after phase compensation. This represents the complex baseband signal before compensation.

[0141] When the platform speed change is not significant or the observation time is short, it can be made To reduce implementation complexity, a drift term is activated when there are significant velocity changes or long observation durations, with an update cycle of 10–50 frames. Through continuous compensation units, the system can maintain phase continuity even in non-triggered phases, avoiding peak broadening, sidelobe elevation, or peak drift caused by phase breaks, thereby improving ranging repeatability.

[0142] 4. The signal quality triggering unit constructs a signal quality index based on the compensated baseband signal, and the decision unit outputs a trigger signal.

[0143] Taking QPSK training sequences as an example, for Complete symbol sampling and hard decision to obtain Based on this, the residual phase error is constructed as follows:

[0144] ,

[0145] in, The symbol represents the judgment result.

[0146] To enhance sensitivity to rapid disturbances, the second-order difference is further calculated:

[0147] ,

[0148] Triggering energy accumulates within the window length W:

[0149] ,

[0150] The window length W ranges from 64 to 512. The decision unit employs a combined threshold and maximum interval constraint: when... Output is triggered when the threshold is exceeded or the trigger interval reaches its upper limit, thus balancing timely response to sudden disturbances with preventing missed updates during long-term drift. The maximum trigger interval is 2–10 frames. Threshold Adaptive form,

[0151] ,

[0152] in k represents the threshold scaling factor, used to adjust the sensitivity of the trigger decision. A larger k results in a higher threshold and sparser triggering, while a smaller k results in a lower threshold and more sensitive triggering. Setting it to... .

[0153] The goal of this part of the engineering is to establish a unified criterion that can simultaneously reflect coherent reliability and disturbance intensity, so that synchronization control and gain control no longer operate independently, avoiding the fragmented state in traditional architectures where the gain is appropriate but the phase is unstable, or the phase is usable but has been saturated and clipped. Through this unified criterion, the system can take control actions at an early stage of coherence quality degradation, reducing the spread of lock-out and the duration of ranging anomalies.

[0154] 5. When the decision unit output is triggered, the synchronization control unit and the gain control unit execute in conjunction under the same trigger event.

[0155] When the decision unit outputs "yes", the synchronization control unit and the gain control unit execute synchronously under the same triggering event, thus structurally realizing co-source closed-loop control of coherent state and dynamic range state, solving the contradictory adjustment problem caused by the independent operation of two control loops in the traditional scheme.

[0156] Among them, the synchronization control unit enters the refresh phase, in the refresh window. Internal estimation of phase correction and frequency offset correction. The phase correction can be taken as the mean of the residual phase:

[0157] ,

[0158] The frequency offset correction is measured by the mean of the phase difference:

[0159] ,

[0160] The refresh window length is set to 128–1024 points, corresponding to a duration of 5–50 ms. This is to suppress abnormal updates caused by phase wrapping. exist Internal expansion processing.

[0161] Synchronization status is updated in steps:

[0162] ,

[0163] ,

[0164] in, Take values ​​between 0.1 and 0.5. Take 0.05–0.2.

[0165] After the refresh is complete, the trigger timer is reset and the trigger count is accumulated.

[0166] ,

[0167] in, Indicates the cumulative number of times the event has been triggered;

[0168] The locking status is determined jointly by residual phase stability and trigger frequency. Locking is considered complete when the residual phase variance is below a threshold and the trigger frequency does not exceed an upper limit. The phase variance threshold is set to 0.02. –0.10 The trigger frequency is set to a maximum of 10–60 times per minute.

[0169] The engineering benefits of this sparse refresh method are: updating the synchronization state only when necessary, reducing the computational power consumption caused by invalid updates, and quickly pulling back to the synchronization state when a phase change occurs, thereby improving locking stability and ranging consistency.

[0170] Simultaneously, the gain control unit reads amplitude statistics and saturation counts, and executes them in conjunction with synchronous refresh when a trigger event occurs, avoiding inconsistent states such as phase refresh but amplitude still saturated or amplitude recovery but phase still drifting. Amplitude statistics can be taken as root mean square.

[0171] ,

[0172] in, This is represented as the baseband sampling sequence within the statistical window Ω, i.e., the compensated complex baseband signal;

[0173] Let the target amplitude range be Set according to full-scale ratio:

[0174] ,

[0175] in, This represents the full-scale amplitude of the analog-to-digital converter (ADC). This is the lower limit scaling factor, used to set the lower limit of the target amplitude range. Set as , This is the upper limit scaling factor, used to set the upper limit of the target amplitude range. Set as .

[0176] Gain control strategies can be divided into three modes with different priorities to ensure engineering safety and ranging stability: saturation protection takes precedence over collaborative fine-tuning, and collaborative fine-tuning takes precedence over weak signal recovery.

[0177] (1) Saturation protection: If or Then it enters the fast gain reduction module:

[0178] ,

[0179] in, This represents the gain control word, used to control the gain of the variable gain amplifier in the receive link. This indicates a rapid gain reduction step size, set to 6 dB. It is used to quickly pull the amplitude back to the safe zone when saturation is detected. It has the highest priority to avoid irreversible distortion caused by clipping, which could lead to distortion of the ranging peak or trigger misjudgment.

[0180] (2) Weak signal recovery: If If there is no saturation, then proceed to the gradual increase gain module:

[0181] ,

[0182] in, This indicates the gain step size in weak signal recovery mode. It is set to 1 dB to avoid excessive one-time gain causing repeated saturation and recovery oscillations.

[0183] (3) Triggering Coordination Fine-tuning: When the triggering event is established and not saturated, in order to obtain a more stable dynamic range within the synchronous refresh window, the target median can be adjusted. Make small, minor adjustments:

[0184] ,

[0185] in,, This indicates the step size for triggering coordinated fine-tuning, used to perform small-step tracking corrections to the gain within the synchronous refresh window, and is set to 1 dB; the fine-tuning period is executed once for each trigger.

[0186] Through the above strategy, gain adjustment is not only used to maintain the amplitude, but also to provide more stable amplitude conditions for coherent tracking and matched filtering at critical synchronous refresh moments, thereby improving the stability and repeatability of ranging output.

[0187] 6. The ranging calculation unit performs arrival time extraction and distance calculation on the compensated baseband signal and outputs the ranging result.

[0188] The ranging solution module calculates the baseband signal after compensation. Matched filtering is performed to estimate the arrival delay. Let the reference template be... If we take a complex baseband template from a known QPSK training sequence after it has undergone the same shaping filter, then:

[0189] ,

[0190] in, This represents the output of the matched filter between the compensated baseband signal and the reference template. Indicates delay Reference template sequence The complex conjugate;

[0191] Use the position with the largest correlation amplitude as the time delay estimate:

[0192] ,

[0193] One-way distance measurement is:

[0194] ,

[0195] Two-way distance measurement is:

[0196] ,

[0197] The speed of sound, c, is 1480–1520 m / s;

[0198] The host computer monitoring module outputs and stores operating parameters such as ranging results, lock-in status, trigger count, gain level, and saturation count through the monitoring unit and monitoring output unit. These parameters are used for status assessment, maintenance decisions, and fault location under long-term monitoring conditions. This design endows the system with observable and diagnosable engineering attributes, facilitating the rapid differentiation in marine environments from different causes, such as increased triggering due to channel degradation, frequent saturation due to improper dynamic range settings, and decreased lock-in due to synchronization drift. This improves system maintainability and mission reliability.

[0199] Example 2:

[0200] This invention provides a shipborne underwater acoustic ranging and receiving system based on synchronous gain cooperative control. For example... Figure 1 As shown, the system is mainly composed of a signal acquisition and conversion module, a receiving, processing and collaborative control module, and a host computer monitoring module.

[0201] The signal acquisition and conversion module consists of a hydrophone, a controllable gain amplifier unit, a bandpass filter unit, and an analog-to-digital converter unit.

[0202] Specifically, the hydrophone acquires the ranging reference acoustic signal and completes the acoustic-to-electric conversion; the analog electrical signal is amplitude shaped by the controllable gain amplification unit to adapt to the dynamic range of the subsequent stage, and after the bandpass filter unit suppresses out-of-band interference, the analog-to-digital conversion unit completes the sampling quantization and outputs the digital sampling signal, which is then sent to the receiving processing and collaborative control module.

[0203] II. The receiving, processing and coordinated control module consists of an I / Q baseband generation unit, a continuous phase compensation unit, a signal quality triggering unit, a decision unit, a gain control unit, a synchronization control unit, a ranging calculation unit, and a data storage unit.

[0204] Specifically, the I / Q baseband generation unit receives the digital sampling signal generated by the signal acquisition and conversion module, performs digital down-conversion and quadrature demodulation on the digital sampling signal to generate I / Q baseband components, and sets up a synchronization status register to store synchronization status quantities such as phase, frequency offset and drift, providing baseband input for coherent processing and ranging calculation;

[0205] The continuous phase compensation unit performs continuous phase compensation on the I / Q baseband components based on the synchronization status parameters in the synchronization status register, so that the system maintains phase continuity and coherent accumulation capability during normal operation, and provides phase-controlled baseband signals for subsequent quality judgment and ranging calculation.

[0206] The signal quality triggering unit extracts the decision guidance residual phase from the baseband signal after continuous phase compensation and constructs a signal quality index to characterize the phase disturbance intensity and coherence reliability changes. At the same time, the signal quality index is output to the decision unit.

[0207] The decision unit performs threshold judgment and decision output on the signal quality index. When the decision output is yes, it enters the cooperative control branch. The cooperative control branch consists of a gain control unit and a synchronization control unit. The synchronization control unit updates the synchronization status register so that the continuous phase compensation unit obtains new compensation basis, thereby reducing the risk of loss of lock and improving the reliability of coherent processing. At the same time, the gain control unit combines the quality index and saturation monitoring results to perform range adjustment on the controllable gain amplification unit in the signal acquisition and conversion module. When the decision output is no, it maintains the current synchronization state and gain state and directly enters the ranging solution unit.

[0208] The ranging calculation unit extracts the arrival time and calculates the distance for the compensated baseband signal, outputting the ranging result. The data storage unit records and stores the ranging result and process data to support playback analysis and engineering evidence collection. At the same time, the ranging output result is input into the host computer monitoring module.

[0209] III. The host computer monitoring module consists of an operation monitoring unit and a monitoring output unit.

[0210] Specifically, the operation monitoring unit collects the system's operating status and key process quantities, and outputs monitoring information such as lock status, trigger count, gain level and saturation count through the monitoring output unit, which is used for long-term shipboard operation status assessment, maintenance decision-making and fault location.

[0211] Example 3:

[0212] To verify the effectiveness of the gain synchronization and cooperative control mechanism described in this invention under conditions of large amplitude fluctuations and rapid phase disturbances, comparative verification was conducted at three levels: simulation experiments, water tank experiments, and field experiments. The comparison object was a conventional independent working architecture, i.e., automatic gain control based on amplitude closed-loop adjustment, synchronization loop updated according to a fixed refresh period, without introducing triggering criteria based on residual phase; this was denoted as the baseline scheme. The proposed scheme was denoted as the cooperative scheme. Key indicators such as ranging error, ranging availability, locking stability, saturation count, and synchronization refresh frequency were statistically analyzed at each level.

[0213] 1. Simulation Experiment

[0214] The simulation experiment used a QPSK ranging training sequence with a known frame structure as the reference signal to construct a time-varying channel including multipath superposition, random amplitude fading, and residual frequency offset. A three-path model was adopted for multipath, with the primary path having a delay of 0 ms, and the secondary paths having delays of 2 ms and 5 ms, with relative amplitudes of -6 dB and -10 dB, respectively. Amplitude fading resulted in fluctuations of 0-20 dB within each frame; the residual frequency offset was taken in the range of 0-5 Hz to characterize platform motion and Doppler effects. The baseline and cooperative schemes were run under different combinations of signal-to-noise ratios and disturbance intensities, and the performance was statistically analyzed over 1000 frames. The comparative results of the simulation experiment are shown in Table 1.

[0215] Table 1. Statistical comparison results of simulation experiments

[0216]

[0217] In the mean square error, availability, saturation rate, and refresh frequency, x / x represents the baseline scheme / cooperative scheme.

[0218] Table 1 shows that under the light disturbance condition (S1), both schemes can maintain near-full availability with small differences in mean square error. The main benefit of the collaborative scheme is that the refresh is changed from a fixed period to on-demand triggering, which significantly reduces the number of refreshes without sacrificing availability, avoiding frequent disturbances and invalid calculations to the loop. This phenomenon is consistent with engineering expectations: when the coherence margin is sufficient, fixed refresh does not necessarily lead to significant error degradation, and the collaborative mechanism is more about optimizing resources and stability.

[0219] As frequency offset and amplitude fluctuations increase and SNR decreases (S2-S5), the saturation rate and lockout risk of the baseline scheme rise simultaneously, leading to a significant increase in mean square error and a decrease in availability. The collaborative scheme initiates refresh early in the coherence degradation stage through residual phase quality triggering, and uses gain adjustment to suppress clipping and unavailability of weak signals, thereby maintaining higher availability and lower mean square error under strong disturbance conditions. Short-term fluctuations may occur in individual frames near the disturbance boundary due to trigger lag or threshold jitter, but statistics from 1000 frames show that the collaborative scheme still maintains a significant advantage in S4-S5, and reduces the refresh frequency to 6-15 times / min.

[0220] 2. Water tank experiment

[0221] The pool experiment was used to verify the effect of cooperative control on improving dynamic range utilization and ranging consistency under controllable and repeatable conditions. Three nominal distances of 10 m, 30 m, and 40 m were set. A 0-18 dB input amplitude variation was created through a programmable attenuator and transmit level adjustment, and a relative motion of 0-1.0 m / s was generated via a slide rail to simulate Doppler and phase disturbances. At least 300 frames were collected for each condition, recording ranging results, lock-on status, saturation count, and trigger count.

[0222] Table 2. Statistical comparison of water tank experiment results

[0223]

[0224] In the mean square error, standard deviation, availability, and saturation count, x / x represents the baseline scheme / cooperative scheme.

[0225] Table 2 shows that under conditions of 10 m, static state, and low amplitude variation, both schemes maintain high availability, with little difference in mean square error and standard deviation, indicating that the baseline scheme can also work stably when the coherence margin is sufficient. The improvement of the cooperative scheme is mainly reflected in slightly lower saturation count and slightly smaller dispersion, reflecting that its gain synchronization can make better use of the dynamic range, but the advantages usually do not show a difference of orders of magnitude under light disturbance scenarios.

[0226] As the distance increases and relative motion and larger amplitude changes are introduced (such as 30m, 40m), the standard deviation of the baseline scheme increases significantly and is accompanied by an increase in saturation count, indicating that clipping and synchronization instability will amplify ranging fluctuations. The cooperative scheme triggers refresh and cooperates with gain fine-tuning when coherence degrades, reducing peak distortion and loss-of-lock diffusion, reducing the standard deviation by about 35%-50% and increasing availability by 3-7 percentage points.

[0227] 3. Experiment in a certain sea area

[0228] Field experiments were conducted in the Jimiyai sea area near Qingdao to verify the engineering applicability under real sea conditions and the coupling of multipath and ship motion. Using an underwater transponder or acoustic beacon as the ranging reference source, the prototype receiver of this invention was mounted on a shipboard platform to record ship speed, heading, and sea state. Round-trip ranging was conducted at three slant ranges of 200 m, 500 m, and 1000 m, with two transmission power levels to create input amplitude differences. Data was continuously collected for at least 10 minutes at each distance, and the ranging availability, mean square error, saturation rate, and trigger refresh frequency were statistically analyzed.

[0229] Table 3. Statistical comparison results of the Jimiyai experiment

[0230]

[0231] Table 3 illustrates the realities under the superposition of multiple uncertainties in the field: Under conditions of 200 m, low sea state, and small input differences, both schemes maintain high availability. The collaborative scheme performs better in terms of mean square error and saturation rate, while significantly reducing the refresh frequency from a fixed period. This result indicates that in relatively stable field conditions, the collaborative mechanism can reduce unnecessary refreshes while ensuring locking, which is beneficial for reducing the long-term operational burden of embedded systems.

[0232] As the slant distance increases, the ship speed increases, and the multipath time variation intensifies (500 m, 1000 m), the baseline scheme exhibits higher saturation and synchronization instability, leading to a decrease in availability and an increase in mean square error. The cooperative scheme triggers sparse refresh and linked gain control when coherence quality degrades, increasing availability to 91.0% at the 1000 m level and reducing mean square error by approximately 27%, while controlling the refresh frequency at 9-15 times / min.

[0233] In summary, the residual phase-based quality triggering mechanism of this invention can accurately indicate coherent degradation and achieve a closed-loop linkage between synchronous refresh and gain adjustment under the same triggering event, thereby simultaneously suppressing clipping saturation and weak signal unavailability, reducing the risk of loss of lock, and improving the stability and consistency of ranging output.

[0234] The embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A ship-borne underwater acoustic ranging receiving method based on synchronous gain cooperative control, characterized in that, Includes the following steps: S1. Ranging signal acquisition, conversion, and dynamic range shaping, outputting digital sampled signal; S2. Perform digital down-conversion and quadrature demodulation on the digital sampled signal to obtain I / Q baseband components, and set the synchronization status register to save the synchronization status parameters; S3. Construct a continuous phase compensation link, perform continuous phase compensation on the I / Q baseband components based on the synchronization state parameters, and output the compensated baseband signal; The continuous phase compensation formula is as follows: ， Where m represents the discrete sampling point number. Let represent the compensation phase used for continuous phase compensation at the nth sampling point. Indicates the phase correction amount. This represents the frequency offset estimator. For frequency offset drift rate, This refers to the baseband sampling rate. The compensation output is: ， in, This represents the complex baseband signal after phase compensation. This represents the complex baseband signal before compensation; S4. Construct a signal quality index based on the compensated baseband signal, input the signal quality index into the decision unit, and have the decision unit complete the threshold decision and output a trigger signal, as follows: S41, Baseband signal After completing symbol sampling and hard decision, we obtain Based on this, the residual phase error is constructed as follows: ， in, The result of the judgment is symbolic; S42. Calculate the sensitivity of second-order difference reinforcement to fast perturbations: ； S43. Accumulate trigger energy within the window length W: ； S44. The decision unit adopts a joint constraint of threshold and maximum interval. Output is triggered when the threshold is exceeded or the trigger interval reaches its upper limit. Adaptive form adopted: ； in k represents the threshold scaling factor, set to... ; S5. If the trigger signal is negative, maintain the current synchronization state and gain state, and directly enter the ranging calculation unit; if the trigger signal is positive, then the synchronization control unit and gain control unit are executed in conjunction. S6. The distance measurement and calculation unit performs arrival time extraction and distance calculation to output distance measurement results. The data storage unit records the distance measurement results and key process data. The host computer monitoring module summarizes the status information and outputs monitoring parameters.

2. The shipborne underwater acoustic ranging and receiving method based on synchronous gain cooperative control according to claim 1, characterized in that, In step S1, the specific process of signal acquisition and conversion is as follows: S101, the hydrophone receives the ranging reference signal and completes the sound-to-electric conversion, outputting an analog electrical signal. ; S102, Let the gain control word be... Gain mapping is The amplified signal is: ， S103. The amplified signal is then bandpass filtered to suppress out-of-band noise and low-frequency interference: ， S104, Analog-to-Digital Conversion Module with Sampling Rate right sampling: ； S105. To achieve engineering protection and gain control input, the analog-to-digital conversion module displays the statistical window. Internal calculation of saturation count: ， in, For ADC warning threshold, window length The points are set to 1024–4096, with a corresponding duration of 20–100ms. To avoid misjudgment due to occasional spikes, a proportional criterion is used. When this occurs, saturation protection is triggered, where, Take 0.05%–0.5%.

3. The shipborne underwater acoustic ranging and receiving method based on synchronous gain cooperative control according to claim 1, characterized in that, In step S5, the operation of the synchronization control unit is as follows: S501. After the trigger is established, the synchronization control unit enters the refresh phase, in the refresh window. Internal estimation of phase correction and frequency offset correction; the phase correction can be taken as the mean of the residual phase: ， The frequency offset correction is measured by the mean of the phase difference: ， The refresh window length is set to 128–1024 points, corresponding to a duration of 5–50 ms, to suppress abnormal updates caused by phase wrapping. exist Inner expansion processing; S502, Synchronization status is updated in steps: ， ， in, Take values ​​between 0.1 and 0.

5. Take a value of 0.05–0.2; S503, After the refresh is complete, reset the trigger timer and accumulate the trigger count: ， in, Indicates the cumulative number of times the event has been triggered; S504. The locked state is determined by a combination of residual phase stability and trigger frequency. Locking is considered complete when the residual phase variance is below a threshold and the trigger frequency does not exceed an upper limit. The phase variance threshold is set to 0.

02. –0.10 The trigger frequency is capped at 10–60 times per minute; The specific working process of the gain control unit is as follows: S511, Root mean square of amplitude statistics: ， in, This is represented as the baseband sampling sequence within the statistical window Ω, i.e., the compensated complex baseband signal; S512, Let the target amplitude range be... Set according to full-scale ratio: ， in, This represents the full-scale amplitude of the analog-to-digital converter (ADC). This is the lower limit scaling factor, used to set the lower limit of the target amplitude range. Set as , This is the upper limit scaling factor, used to set the upper limit of the target amplitude range. Set as ; S513. The gain control strategy is divided into three modes with priorities: saturation protection takes precedence over collaborative fine-tuning, and collaborative fine-tuning takes precedence over weak signal recovery. The three modes are as follows: (1) Saturation protection: If saturation counting or Then it enters the fast gain reduction module: ， in, Indicates the gain control word. This indicates the rapid gain reduction step size, set to 6 dB; (2) Weak signal recovery: If If there is no saturation, then proceed to the gradual increase gain module: ， in, This indicates the gain increment step size in weak signal recovery mode, set to 1 dB; (3) Triggered Coordination Fine-tuning: When the triggering event is established and not saturated, in order to obtain a more stable dynamic range within the synchronous refresh window, the target median is adjusted. Make small, minor adjustments: ， in, This indicates the step size for triggering collaborative fine-tuning, set to 1 dB; the fine-tuning period is 1 time per trigger.

4. The shipborne underwater acoustic ranging and receiving method based on synchronous gain cooperative control according to claim 1, characterized in that, In step S6, the ranging solution module calculates the baseband signal after compensation. Perform matched filtering to estimate arrival delay, assuming the reference template is... ,but ， in, This represents the output of the matched filter between the compensated baseband signal and the reference template. Indicates delay Reference template sequence The complex conjugate; Use the position with the largest correlation amplitude as the time delay estimate: ， One-way distance measurement is: ， Two-way distance measurement is: ， Where c represents the speed of sound.

5. A shipborne underwater acoustic ranging and receiving system based on synchronous gain cooperative control, applicable to the shipborne underwater acoustic ranging and receiving method based on synchronous gain cooperative control as described in any one of claims 1-4, characterized in that, It includes a signal acquisition and conversion module, a receiving, processing and collaborative control module, and a host computer monitoring module; The signal acquisition and conversion module is connected to the receiving, processing and collaborative control module, which converts the ranging reference acoustic signal into a digital sampling signal and sends the digital sampling signal into the receiving, processing and collaborative control module. The receiving processing and cooperative control module includes an I / Q baseband generation unit, a continuous phase compensation unit, a signal quality triggering unit, a decision unit, a cooperative control branch, and a ranging calculation unit; The I / Q baseband generation unit generates I / Q baseband components from the digital sampling signal and sets a synchronization status register to store synchronization status parameters. The continuous phase compensation unit performs continuous phase compensation on the I / Q baseband components based on the synchronization state parameters, maintains the baseband phase continuity and coherent accumulation capability during non-triggered periods of the system, and provides a phase-controlled baseband signal. The signal quality triggering unit extracts the decision guidance residual phase from the baseband signal and constructs a quality index. The decision unit performs threshold judgment and decision output on the quality index. If the decision output is yes, it enters the collaborative control branch. If the decision output is negative, the current synchronization state and gain state are maintained, and the process directly enters the ranging calculation unit. The collaborative control branch includes a gain control unit and a synchronization control unit. When the decision unit outputs "yes", the gain control unit performs a level adjustment on the controllable gain amplification unit in the signal acquisition and conversion module. At the same time, the synchronization control unit updates the synchronization status parameters so that the continuous compensation unit obtains the updated compensation basis. The ranging calculation unit performs arrival time extraction and distance calculation on the compensated baseband signal and outputs the ranging result. The host computer monitoring module receives the ranging results and outputs monitoring information for status assessment, maintenance decision-making, and fault location.

6. The shipborne underwater acoustic ranging and receiving system based on synchronous gain cooperative control according to claim 5, characterized in that, The signal acquisition and conversion module also includes a hydrophone, a bandpass filter unit, and an analog-to-digital converter unit; the hydrophone acquires the ranging reference acoustic signal and completes the acoustic-to-electric conversion; the controllable gain amplification unit is used for signal amplitude shaping to adapt to the dynamic range of the subsequent stage; and the bandpass filter unit suppresses out-of-band interference. The analog-to-digital converter unit is used for sampling and quantizing to output digital sampled signals.

7. The shipborne underwater acoustic ranging and receiving system based on synchronous gain cooperative control according to claim 5, characterized in that, The host computer monitoring module includes a running monitoring unit and a monitoring output unit; the running monitoring unit collects the system running status and key process quantities; the monitoring output unit outputs monitoring information such as lock status, trigger count, gain level, and saturation count.

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