A method and device for timing synchronization of shipborne dual-antenna PCMA system signals

Abstract

The present invention discloses a method and device for timing synchronization of signals in a shipborne dual-antenna PCMA system. The method comprises: obtaining a first signal quality value representing the initial channel quality during a signal search phase; estimating a second signal quality value representing the dynamic channel characteristics during a synchronization tracking phase, and detecting the timing error between the mixed signal and the local signal; performing feedforward initialization setting on the filter parameters of the synchronization loop based on the first signal quality value, and performing real-time, incremental feedback adjustment on the aforementioned parameters based on the second signal quality value. By combining feedforward initialization with real-time feedback optimization, the present invention achieves intelligent and coordinated control of the multi-dimensional parameters of the loop, and can lock or relock synchronization in the fastest manner under complex and changing channel conditions, thereby improving the continuity and reliability of the communication system.

Description

Technical Field

[0001] The present invention belongs to the field of signal detection, and in particular to a timing synchronization method and device for shipborne dual-antenna PCMA system signals. Background Art

[0002] Paired Carrier Multiple Access (PCMA), as an efficient spectrum reuse technology, plays a crucial role in modern satellite communications. Its application value is particularly prominent in onboard communications scenarios, where bandwidth resources are extremely scarce. Applying PCMA technology to mobile maritime platforms, such as ocean-going ships, is crucial for ensuring long-distance communications and achieving a seamless global data link. To mitigate the potential obstruction of satellite signals by ship structures (such as masts and cabins) during maneuvers, shipboard platforms typically deploy dual antenna systems, using intelligent switching mechanisms to ensure that at least one antenna maintains unobstructed satellite communication. However, while ensuring communication continuity, this dual-antenna architecture also introduces unique and significant technical challenges. The moment antenna switching occurs, the signal transmission path, Doppler shift, propagation delay, and even signal amplitude can undergo sudden changes, which can easily cause the timing synchronization loop of the backend demodulator to lose lock. Therefore, studying a method that can achieve fast, stable and reliable timing synchronization recapture and locking in the shipborne dual-antenna PCMA system in the face of frequent and unpredictable signal interruptions and mutations is of vital theoretical and engineering significance for improving the overall performance of the maritime mobile satellite communication system, ensuring the continuity of key missions and optimizing user experience.

[0003] Timing synchronization technology has reached considerable maturity in digital communication receiver design. Existing timing synchronization loops generally employ a classic closed-loop feedback control structure, whose core consists of a timing error detector (TED), a loop filter (LF), a numerically controlled oscillator (NCO), and an interpolator. In the timing error detection phase, algorithms such as the Early-Late Gate (EDG), Gardner, and Mueller and Muller are widely used. These algorithms estimate the deviation between the current sampling instant and the optimal sampling instant through specific sampling point decision logic. In the loop filtering phase, the Proportional-Integral (PI) controller is the most popular choice. Key parameters such as loop bandwidth and damping coefficient are typically set to a fixed compromise value based on the expected channel statistics during the design phase, balancing loop acquisition speed and tracking accuracy. To accommodate different operating phases, some relatively advanced systems have introduced dual-mode operation. These systems use a wider loop bandwidth during the initial signal acquisition phase to accelerate lock speed. Once stable tracking is achieved, they switch to a narrower bandwidth to suppress noise and improve synchronization accuracy. This mode switch is typically triggered by a simple phase-locked loop lock indicator (LockDetector). During the initial signal acquisition phase, existing technologies often employ time-domain sliding correlation based on a locally known sequence, or frequency-domain fast correlation using a fast Fourier transform (FFT), performing brute-force or segmented scanning within a preset, large time uncertainty window.

[0004] Although existing timing synchronization technology performs well in static or slowly varying channels, it cannot effectively resolve the inherent contradiction between fast recapture and stable tracking in a changing channel in the extremely dynamic environment of shipborne dual-antenna PCMA, resulting in large fluctuations in detection results and channel desynchronization. Summary of the Invention

[0005] The purpose of the invention is to provide a method and device for timing synchronization of shipborne dual-antenna PCMA system signals, in order to solve at least one technical problem existing in the prior art.

[0006] Technical solution: A timing synchronization method for shipborne dual-antenna PCMA system signals, including:

[0007] Performing a search operation on the received PCMA mixed signal to obtain a first signal quality value representing an initial channel quality;

[0008] Processing the PCMA mixed signal and the local signal to generate a timing error reflecting the timing difference between the two, and estimating a second signal quality value representing the dynamic channel characteristics;

[0009] Determining loop filter parameters based on the first and second signal quality values, and using the parameters to process the timing error to output a corrected timing error;

[0010] Based on the corrected timing error, the local signal is interpolated and corrected to generate a synchronized signal that is synchronized with the PCMA mixed signal.

[0011] A timing synchronization device for a shipborne dual-antenna PCMA system signal, using the timing synchronization method, comprises:

[0012] A search module, configured to perform a search operation on the received PCMA mixed signal to obtain a first signal quality value representing an initial channel quality;

[0013] a signal analysis module, configured to process the PCMA mixed signal and the local signal, generate a timing error reflecting the timing difference between the two, and estimate a second signal quality value representing dynamic channel characteristics;

[0014] a loop filter module, configured to determine loop filter parameters based on the first signal quality value and the second signal quality value, and use the parameters to process the timing error and output a corrected timing error;

[0015] The interpolation correction module is used to perform interpolation correction on the local signal based on the corrected timing error to generate a synchronized signal that is synchronized with the PCMA mixed signal.

[0016] Beneficial effect: The present invention not only fundamentally solves the problem of slow recapture or channel desynchronization caused by the mismatch between initial parameters and channels, but also maintains a high response speed and tracking accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flowchart of the steps of a timing synchronization method for a shipborne dual-antenna PCMA system signal provided in an embodiment of the present application.

[0018] Figure 2 A flowchart of the steps for obtaining the first signal quality value provided in an embodiment of the present application.

[0019] Figure 3 A flowchart of the steps for estimating the second quality value of a signal provided in an embodiment of the present application.

[0020] Figure 4 A schematic diagram of PCMA signal transmission provided in an embodiment of the present application.

[0021] Figure 5 This is an installation diagram of the shipborne PCMA satellite equipment provided in an embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0024] Research has revealed that in the extremely dynamic environment of shipborne dual-antenna PCMA, the performance bottlenecks and deep-seated technical flaws of existing timing synchronization technologies are fully exposed. These flaws do not stem from the shortcomings of a single algorithm, but rather from the rigidity and lack of intelligence in the control logic, which prevents them from effectively resolving the inherent contradiction between fast reacquisition and stable tracking in fluctuating channels. This contradiction manifests itself in two core technical issues: First, the static configuration of loop parameters cannot adapt to the randomness of channel quality at the time of reacquisition. Traditional fixed-parameter or simple dual-mode loops are designed with a one-size-fits-all approach. For example, after losing lock due to antenna switching, the signal may reappear in the next second, but the signal-to-noise ratio at this point may be strong or weak, which is random. However, traditional loops still use a fixed bandwidth for acquisition. When the reacquisition signal quality is poor, excessive noise is introduced, causing the loop to fluctuate violently near the lock point, or even lose lock. When the reacquisition signal quality is excellent, the loop is overly conservative, failing to take advantage of favorable channel conditions to achieve the fastest lock. This inability to tailor parameter initialization based on initial signal quality is one of the fundamental reasons for poor reacquisition performance. Secondly, the single loop control dimension cannot cope with the complex changes in channel characteristics during tracking. Existing loop adjustments often involve crude switching of a single dimension: loop bandwidth. However, the stable tracking capability of a high-performance synchronous loop depends on two mutually reinforcing dimensions: the response characteristics of the loop filter itself (i.e., bandwidth) and the cleanliness of the timing error estimate input to the filter, which in turn depends on the correlation integration length of the phase detector. During dynamic tracking, when signal quality degrades, the ideal strategy is to simultaneously narrow the loop bandwidth to enhance smoothing and increase the correlation length to suppress noise, or vice versa. Traditional methods lack this multi-dimensional, coordinated, and refined control capability. Their simple mode switching cannot achieve optimal parameter matching. Consequently, in complex scenarios with dynamically changing signal-to-noise ratios and power imbalances, either tracking accuracy or response speed is compromised, making it difficult to achieve both.

[0025] like Figure 1 As shown, a timing synchronization method for a shipborne dual-antenna PCMA system signal is proposed, comprising the following steps:

[0026] Performing a search operation on the received PCMA mixed signal to obtain a first signal quality value representing an initial channel quality;

[0027] Processing the PCMA mixed signal and the local signal to generate a timing error reflecting the timing difference between the two, and estimating a second signal quality value representing the dynamic channel characteristics;

[0028] Determining loop filter parameters based on the first and second signal quality values, and processing the timing error using the loop filter parameters to output a corrected timing error;

[0029] Based on the corrected timing error, the local signal is interpolated and corrected to generate a synchronized signal that is synchronized with the PCMA mixed signal.

[0030] like Figure 2 As shown, according to one aspect of the present application, obtaining a first signal quality value includes:

[0031] Perform fast Fourier transform on the PCMA mixed signal and the local signal respectively to obtain the mixed signal frequency domain representation and the local signal frequency domain representation;

[0032] Performing complex multiplication on the frequency domain representation of the mixed signal and the conjugate of the frequency domain representation of the local signal, and performing inverse fast Fourier transform on the complex multiplication result to generate a time domain correlation result;

[0033] The time domain correlation results are analyzed, and the ratio of the correlation peak value to the mean value is determined as the first signal quality value.

[0034] like Figure 3 As shown, according to one aspect of the present application, estimating the second signal quality value includes:

[0035] Calculate the correlation between the PCMA mixed signal and the conjugate of the local signal to obtain the mixed correlation value;

[0036] Calculate the local signal's own energy to obtain the local energy value;

[0037] The ratio of the amplitude of the mixed correlation value to the local energy value is calculated as the second signal quality value.

[0038] According to one aspect of the present application, outputting a corrected timing error includes:

[0039] Setting initial loop filter parameters based on the first signal quality value;

[0040] In response to the second signal quality value, dynamically adjusting the initial loop filter parameters or the subsequently modified parameters thereof to obtain currently used loop filter parameters;

[0041] The timing error is processed using the currently used loop filter parameters and the corrected timing error is output.

[0042] According to one aspect of the present application, setting initial loop filter parameters includes:

[0043] Comparing the first signal quality value with a preset quality threshold value including at least two different values ​​to determine a quality interval to which the first signal quality value belongs;

[0044] According to the determined quality interval, a corresponding specific parameter combination is selected from a preset parameter library as an initial loop filter parameter.

[0045] According to one aspect of the present application, obtaining the currently used loop filter parameters includes:

[0046] comparing the second signal quality value with preset upper and lower adjustment thresholds;

[0047] If the second signal quality value is higher than the upper adjustment threshold, a preset increment is added to the loop filter parameter to be adjusted to obtain the currently used loop filter parameter;

[0048] If the second signal quality value is lower than the lower adjustment threshold, subtracting a preset increment from the loop filter parameter to be adjusted to obtain the currently used loop filter parameter;

[0049] If the second signal quality value is between the upper and lower adjustment thresholds, the loop filter parameters to be adjusted are kept unchanged and used as the loop filter parameters currently used.

[0050] According to one aspect of the present application, the step of setting a set of initial loop filter parameters based on the first signal quality value further includes:

[0051] According to the determined quality interval, a corresponding initial correlation sequence length is set for a phase detector used to generate a timing error.

[0052] According to one aspect of the present application, the method of dynamically adjusting the signal in response to the second signal quality value further includes:

[0053] If the second signal quality value is higher than the upper adjustment threshold, shortening the length of the correlation sequence of the phase detector used to generate the timing error;

[0054] If the second signal quality value is lower than the lower adjustment threshold, increasing the correlation sequence length of the phase detector;

[0055] If the second signal quality value is between the upper adjustment threshold and the lower adjustment threshold, the length of the correlation sequence of the phase detector is maintained unchanged.

[0056] In one embodiment of the present application, assume a ship is sailing with a dual-antenna PCMA communication system operating normally. The signal symbol rate is 10 Msps, and the receiver sampling rate is 40 Msps. At a certain moment, due to the ship's turning, the active main antenna A is blocked by the mast, and the system automatically switches to the backup antenna B. This switching process causes a brief signal interruption of approximately 50ms before recovery, leaving the demodulator in a lost-lock state, requiring re-search and synchronization. Upon detecting the lost-lock state, the system immediately activates the search module to perform a search operation on the PCMA mixed signal r(t) received by antenna B. The frequency-domain fast correlation method is used to process data within a time uncertainty window. Specifically, the PCMA mixed signal r(t) and the local signal s(t) within this window are each subjected to a fast Fourier transform (FFT). The transform results are then conjugate-multiplied and inverse-FFTed to generate a time-domain correlation result. By analyzing this time-domain correlation result, the system not only determines the approximate time of signal arrival but also calculates the ratio of its peak value to its mean value, which serves as the first signal quality value Q1. Assuming that the signal quality after recapture is good, the calculated logarithm of Q1 is 30.1 dB. The loop filter module receives the Q1 value (30.1 dB) and performs parameter initialization. The system presets two levels of quality thresholds, Th Q1，high =27 dB, Th Q1，low =21 dB. Since Q1=30.1 dB>Th Q1，high The system determines that the current initial channel quality is excellent, requiring more aggressive parameters to achieve the fastest possible lock. Based on the determined excellent quality range, the corresponding initial loop filter parameters Cinit are selected from a preset parameter library, for example, to a set of values ​​with a faster response speed. Furthermore, based on this excellent quality range, the system also sets the corresponding initial correlation sequence length Linit for the phase detector. For example, a shorter length, such as Linit = 8192 samples, is selected. This step tailors the core parameters of the entire synchronization loop before it begins operation, laying the foundation for subsequent fast lock. The loop begins operation with the initial loop filter parameters and initial correlation sequence length as initial parameters. In the first processing cycle, the system processes the PCMA mixed signal r(t) and the local signal s(t). The phase detector uses a correlation sequence of length Linit to calculate the initial timing error ek. The amplitude detection module calculates the second signal quality value Q2. Assuming that the link is transiently attenuated after the handover, the logarithm of the second signal quality value Q2 is -1.9 dB. The timing error ek and Q2 value will be sent to the loop filter module for further processing.

[0057] The loop filter module receives the timing error ek and the second signal quality value Q2. According to the value of Q2, the current loop parameters are adjusted in real time. The upper and lower adjustment thresholds are preset as ThQ2，upper =+3 dB, Th Q2，lower =-3 dB. In the current cycle, Q2=-1.9 dB, which is between the upper and lower adjustment thresholds. Therefore, the loop filter module determines that the current channel is stable and no adjustment is required. At this time, the currently used loop filter parameter Ccurr is maintained at Cinit. At the same time, the phase detector correlation sequence length Lcurr is also maintained at Linit. In the next few processing cycles, it is assumed that the link gradually stabilizes and the signal amplitude returns to normal. In the mth processing cycle, the calculated logarithm of the second signal quality value Q2 becomes +4.5 dB. At this time, Q2>Th Q2，upper The loop filter module performs an increment operation, adding a preset increment Δc to the current loop filter parameter Ccurr to obtain a new loop filter parameter Ccurr. Simultaneously, as signal quality improves, the system concurrently shortens the correlation sequence length by subtracting a preset increment ΔL from the current correlation sequence length Lcurr to obtain a new correlation sequence length Lcurr. In each cycle, the loop filter module uses the determined loop filter parameter Ccurr to process the input timing error ek and output a corrected timing error uk. The interpolation correction module then performs fine phase adjustment on the local signal s(t) based on the corrected timing error uk to generate a synchronized signal. Through the above steps, this embodiment can achieve rapid lock by setting aggressive loop parameters based on the initial signal quality (30.1 dB) after loss of lock due to antenna switching. During tracking, the loop is smoothly adjusted to a more stable and responsive state based on dynamic changes in channel quality (improvement from -1.9 dB to +4.5 dB). Test data shows that the system can complete stable relock within approximately 2000 symbol periods. Compared with traditional methods that use fixed parameters or simple dual-mode switching (which usually require more than 5000 symbol periods), this improves the synchronization recovery speed and ensures communication continuity.

[0058] In one embodiment of the present application, the estimation of the second quality value Q2 of the signal is completed by the amplitude detection module. This process can evaluate the dynamic changes of the channel characteristics after the tracking loop is locked in real time, especially the fluctuation of the signal amplitude. Specifically, the amplitude detection module receives the baseband digital sampling sequence of the PCMA mixed signal, denoted as r[n], and the baseband digital sampling sequence of the local signal corrected by the synchronization module, denoted as s[n]. The estimation process is based on a processing block with a length of K sampling points. The correlation between the conjugate of the PCMA mixed signal and the local signal is calculated to obtain a mixed correlation value. Specifically, the cross-correlation value of the complex conjugate s*[n] of the r[n] sequence and the s[n] sequence in the processing block is calculated, denoted as the mixed correlation value C, C=∑ n=0 K-1r[n]·s*[n]; The amplitude and phase of the complex value C comprehensively reflect the strength and phase relationship of the components in the received signal that are related to the local signal. Calculate the local signal's own energy to obtain the local energy value. To normalize the above correlation value, it is necessary to calculate the total energy of the local signal within the processing block, denoted as the local energy value E. This calculation is obtained by accumulating the squares of the amplitudes of the local signal sequence s[n]: E=∑ n=0 K-1 ∣s[n]∣ 2 The energy value E represents the strength of the local reference signal. The ratio of the amplitude of the hybrid correlation value to the local energy value is calculated as the second signal quality value. Dividing the modulus (amplitude) of the hybrid correlation value C by the local energy value E yields the second signal quality value Q2: Q2 = |C| / E = |∑ n=0 K-1 r[n]·s*[n]| / ∑ n=0 K-1 ∣s[n]∣ 2 This Q2 value physically estimates the amplitude of the channel impulse response and accurately reflects real-time signal amplitude variations caused by factors such as multipath fading and power imbalance. The Q2 value is then fed into the loop filter module for real-time, incremental feedback adjustments to the loop filter parameters and the phase detector correlation length, enabling the synchronization loop to adapt to dynamically changing channel conditions.

[0059] In the specific scenario of switching shipboard antennas, the quality of the reacquisition signal is completely random. Traditional methods, using fixed, one-size-fits-all broadband acquisition parameters, cannot account for this randomness. In this embodiment, the first signal quality value provides the system with first-hand intelligence for decision-making; the hierarchical threshold comparison and parameter library selection form the intelligent decision-making brain and arsenal. When the intelligence indicates an excellent channel, the brain instructs the arsenal to use an aggressive, narrow integration length parameter set, sacrificing initial stability for extreme lock speed. When the intelligence indicates a poor channel, a conservative, long integration length parameter set is used, sacrificing speed for a successful, reliable lock. This avoids lock failures or slow locks caused by parameter mismatches with the channel, ensuring that the loop always starts in the mode most optimal for the current channel and restores communications with minimal time after a loss of lock. The three-stage incremental adjustment logic (increase / subtract / hold) provides a stable core for the loop, preventing overreaction to minor noise and ensuring tracking stability. When significant channel fluctuations occur (above or below a threshold), this mechanism responds simultaneously in two ways: by adjusting loop filter parameters to alter the loop's response (making it faster or more stable); and by adjusting the correlation length to change the quality of the loop's input information (making it clearer or smoother). These two actions work together, much like controlling the accelerator and steering wheel simultaneously in complex road conditions, enabling the loop to consistently find the optimal balance between response speed and noise suppression. This mechanism maintains low jitter and high-precision tracking even in the face of continuously changing channel conditions such as ocean multipath and atmospheric attenuation.

[0060] According to one aspect of the present application, generating a timing error reflecting a timing difference between the two includes:

[0061] Generate auxiliary data sequence based on PCMA mixed signal and local signal;

[0062] The auxiliary data sequence is shifted ahead and behind by half a symbol period respectively, and the autocorrelations of the shifted sequences are calculated to obtain leading and lagging autocorrelation functions respectively.

[0063] The timing error is obtained by cross-calculating the leading and lagging autocorrelation functions.

[0064] In one embodiment of the present application, after the synchronization loop enters a stable tracking state, in the current processing cycle, a precise timing error ek is calculated based on the input PCMA mixed signal r(t) and the corrected local signal s(t) for use by the loop filter. Assume that the number of sampling points corresponding to the symbol period is 4 (Ts=4). This generates an intermediate signal sensitive to timing error. Specifically, the current input PCMA mixed signal r(t) (here, already the baseband signal) is complex multiplied point by point by the conjugate of the local signal s(t) after interpolation correction in the previous cycle. The resulting product sequence is the auxiliary data sequence. The phase information of this sequence primarily reflects the residual carrier frequency offset and phase noise, while the zero-crossing position of its symbol energy is closely related to the actual symbol timing deviation. After obtaining the auxiliary data sequence, it is subjected to parallel early and late processing, where half a symbol period corresponds to Ts / 2 = 2 sampling points. Specifically, the auxiliary data sequence is shifted forward by 2 sampling points on the time axis as a whole to obtain an advanced sequence, and the autocorrelation function of the advanced sequence is calculated to obtain the advanced autocorrelation function, which is recorded as Rearly(τ); the original auxiliary data sequence is shifted backward by 2 sampling points on the time axis as a whole to obtain a delayed sequence, and the autocorrelation function of the delayed sequence is calculated to obtain the delayed autocorrelation function, which is recorded as Rlate(τ). After obtaining the advanced and delayed autocorrelation functions, the timing error information is extracted through a cross operation. The cross operation specifically subtracts the values ​​of the two autocorrelation functions at zero delay (τ=0) and multiplies them by the normalized gain coefficient K. TED :ek=K TED [Rearly(0)-Rlate(0)]. If the current sampling timing is accurate, the energy of the leading and lagging sequences (i.e., the value of the autocorrelation function at zero) should be roughly equal, with a difference of zero. If the sampling time is too early, the lagging sequence energy is stronger, and the difference is negative. If the sampling time is too late, the leading sequence energy is stronger, and the difference is positive. The sign and magnitude of this difference accurately reflect the direction and magnitude of the timing error. The output timing error ek has a high signal-to-noise ratio and stability. It is used as the input of the loop filter to calculate the corrected timing error uk, thereby driving the closed-loop operation of the entire synchronization loop. This ensures stable and reliable timing synchronization even in the presence of residual frequency offset.

[0065] This embodiment achieves highly robust timing error estimation that is insensitive to carrier frequency offset. In PCMA systems, the received signal often exhibits residual carrier frequency offset due to the Doppler effect and local oscillator frequency deviation. This frequency offset severely impacts the performance of traditional timing error detection algorithms (such as those that operate directly on baseband signals), generating self-noise and reducing estimation accuracy. This embodiment transfers most of the carrier information to the sequence's phase by generating an auxiliary data sequence. The autocorrelation result primarily depends on the shape of the sequence's energy envelope and is insensitive to linear phase rotation (i.e., carrier frequency offset) of the sequence. This embodiment mechanically decouples the mutual influence between carrier synchronization and timing synchronization, ensuring that the timing error detection phase of the entire synchronization loop can provide a clean and reliable error input even during the transition phase when the carrier loop is not yet fully locked. This is a critical prerequisite and guarantee for the stable and efficient operation of the entire adaptive loop.

[0066] According to one aspect of the present application, before performing a search operation on the received PCMA mixed signal, the process further includes determining a search time window, specifically:

[0067] Based on the collected sample data, a probability model is established to describe the probability of the search signal appearing in different time windows;

[0068] From the probability model, the time window with the highest probability of occurrence is selected as the priority search time window;

[0069] Furthermore, the step of performing a search operation on the received PCMA mixed signal is performed within a priority search time window.

[0070] According to one aspect of the present application, before performing fast Fourier transform on the PCMA mixed signal, the method further includes:

[0071] Determine the relationship between the number of sampling points of the PCMA mixed signal within a preset time window and a preset first threshold and a second threshold;

[0072] If the number of sampling points is less than the first threshold, data padding is performed on the PCMA mixed signal to obtain a padded signal, wherein a fast Fourier transform is performed on the padded signal;

[0073] If the number of sampling points is greater than the second threshold, data extraction is performed on the PCMA mixed signal to obtain a extracted signal, wherein the fast Fourier transform is performed on the extracted signal.

[0074] In one embodiment of the present application, a newly installed shipboard dual-antenna PCMA terminal is powered on for the first time. Without valid GPS position information input, the theoretical estimate of satellite-to-ground delay has a large uncertainty window of approximately 36ms. The system sampling rate is 40 Msps, and the FFT processor's reference length is 4096 points. Given this wide uncertainty window of 36ms (corresponding to 1,440,000 sampling points), a full-range brute-force scan would be extremely time-consuming. A built-in general probability model, developed based on global satellite coverage characteristics and statistical data from common flight routes, assesses the probability of a signal occurring within different delay windows. Specifically, the model indicates that for the ship's current approximate latitude, the signal delay has a probability of over 70% falling within the 2ms range of 248ms to 250ms. Therefore, this 2ms time window is selected as the priority search window, while other areas are considered secondary search targets. A significantly narrowed, high-probability priority search window is output. After determining a 2ms priority search window, data within this window is collected, totaling 2ms x 40 Msps = 80,000 samples. This data volume far exceeds the baseline length of the backend FFT processor. This triggers the data adaptive preprocessing step. The system's preset first threshold is 4096 points, and the second threshold is 32,768 points. Since the current number of samples, 80,000, exceeds the second threshold of 32,768, it is determined that data decimation is necessary. Specifically, a variable rate decimator is used to process these 80,000 samples at a decimation rate of 4, producing a decimated signal of 20,000 points. Frequency domain correlation operations are performed on this 20,000-point decimated signal. Since the length is still greater than 4096, segmented processing is possible, though a single segment is used here. This decimated signal is then processed together with the local signal s(t), which has also been decimated by 4, undergoing FFT, conjugate complex multiplication, and inverse fast Fourier transform (IFFT). Because this search is based on extracted data, its timing accuracy is coarse. Assuming a correlation peak is successfully detected during this process, record the approximate time position corresponding to that peak. For example, determine that the signal appears around 249.1ms. Simultaneously, calculate the signal's first quality value, Q1, at this time. Because the extraction process smooths some noise, the resulting logarithm of the signal's first quality value, Q1, may be slightly high, for example, by 31.5 dB. Optionally, after completing coarse capture, perform a higher-precision, non-decimated fine search around the 249.1ms position to obtain more accurate timing information and Q1 values.

[0075] Another implementation of the probabilistic model involves dividing the global ocean into several geographic grids. Using satellite orbit simulation software, a statistical histogram of round-trip signal delay within each grid is calculated. This histogram is normalized and stored as a probabilistic model in the device's non-volatile memory. Once the device has a rough idea of ​​its grid location (e.g., through base station information or manual input), it can load the corresponding probabilistic model.

[0076] The above steps solved the problem of rapid acquisition under large uncertainties. Probabilistic model optimization narrowed the search calculation range. Adaptive data preprocessing reduced the data volume and computational complexity of a single FFT. Compared to traditional full-range scanning methods, acquisition time was reduced from minutes to seconds, significantly improving acquisition efficiency.

[0077] This embodiment achieves ultra-fast signal acquisition under extreme time uncertainty, making it particularly suitable for terminal cold start or extended lock-loss scenarios. Traditional signal search is essentially a blind process with zero information content, requiring a blanket scan of the entire uncertainty window, resulting in significant computational and time overhead. The probabilistic model introduced in this embodiment essentially incorporates prior information (whether based on historical statistics or a general physical model). This transforms fuzzy, unstructured prior information into a structured, quantifiable probability distribution, which is then used to guide the precise allocation of computing resources. In scenarios where a shipborne terminal cold starts and GPS information is unavailable, resulting in latency uncertainty as high as tens of milliseconds, the search range can be narrowed from tens of milliseconds to the most probable few milliseconds, reducing computational effort by orders of magnitude. Transforming the traversal problem into an optimization problem fundamentally changes the nature of the search, thereby ensuring acquisition probability while shortening the initial network access wait time.

[0078] According to one aspect of the present application, a timing synchronization device for a shipborne dual-antenna PCMA system signal includes:

[0079] A search module, configured to perform a search operation on the received PCMA mixed signal to obtain a first signal quality value representing an initial channel quality;

[0080] a signal analysis module, configured to process the PCMA mixed signal and the local signal, generate a timing error reflecting the timing difference between the two, and estimate a second signal quality value representing dynamic channel characteristics;

[0081] a loop filter module, configured to determine loop filter parameters based on the first signal quality value and the second signal quality value, and use the parameters to process the timing error and output a corrected timing error;

[0082] The interpolation correction module is used to perform interpolation correction on the local signal based on the corrected timing error to generate a synchronized signal that is synchronized with the PCMA mixed signal.

[0083] like Figure 4 As shown in the figure, during satellite communication, station type 1 and station type 2 transmit signals y1(t) and y2(t), respectively, while the received signal is y1(t) + y2(t). Since y1(t) and y2(t) are transmitted in the same space, time, and frequency, conventional demodulation at the receiver would prevent communication. Since the local station's transmit sequence is known, PCMA multiplexing technology can solve the communication problem under these conditions. In engineering applications, products often utilize PCMA multiplexing, asymmetric cooperative communication. During communication, the transmit sequence is known, while the delay, attenuation, and noise of the entire satellite link are unknown. During engineering design, PCMA satellite equipment must offset the local signal component from the satellite's received signal. In PCMA satellite communication systems, parameter estimation and signal synchronization often occur under low signal-to-noise ratios. For example, in a noise-free and power-symmetrical PCMA satellite communication system, the PCMA demodulator operates at 0dB. In actual communications, due to noise and power asymmetry at the end stations, the signal-to-noise ratio can drop as low as -12dB. Furthermore, the two antenna units are independent, and the demodulator will inevitably lose synchronization during antenna switching. This excessive noise leads to significant fluctuations in detection results. Furthermore, user experience demands an extremely short recovery time, requiring the demodulator to possess fast reacquisition and loop lock capabilities.

[0084] The antenna installation position of the ship is as follows Figure 5 As shown, the middle position of the ship is blocked by the mast and the cabin. When the satellite is located on the right side of the ship, the left antenna cannot be aligned with the satellite normally; and vice versa. When the ship is turning while sailing on the sea, the antenna automatically switches according to the satellite strength value. Since the two sets of antennas are independently fed with clocks and power, when the antennas are switched, the parameters of the baseband signal will change significantly, resulting in abnormal demodulation of the PCMA communication terminal and even communication failure. In addition, due to the extremely low error rate of other operations and signal detection, the demodulator must have self-repair capabilities. In another embodiment of the present application, a timing synchronization method for shipborne dual-antenna PCMA system signals includes:

[0085] S1. Start the search module of the PCMA demodulator to search for signals.

[0086] When searching for signals, the focus is on the delay estimation module in the signal demodulation of the PCMA satellite communication system. Estimating the delay τ is the first step in signal processing at the receiver, determining whether subsequent demodulation will function properly. However, due to the uncertainty of satellite link conditions, τ estimation requires a wide search range, high computational complexity, and long processing time, significantly impacting the user experience. Estimating the delay τ often requires approximating the delay using satellite parameters and the latitude and longitude of the satellite's location. Signal processing methods are then used to accurately determine the satellite-to-ground delay. While the more precise the external parameters, the simpler the signal processing method. However, in practice, due to external constraints, the estimated values ​​often have significant errors, making the estimation of signal delay τ complex.

[0087] S11. Start the search module and initialize the search module parameters based on the device input parameters. When the external device is connected to the GPS signal, the device is initialized to the fast synchronization mode; if it is configured through the interface parameters, the device is initialized to the standard synchronization mode; if there is no external parameter assistance or external information cannot be synchronized, the device is initialized to the fuzzy synchronization mode.

[0088] S12. Predetermine a time window. Divide the time window into a predetermined number of time slots. Select the median of the predetermined number of time slots as the signal interval, collect data within the signal interval, and obtain sampling points. The predetermined parameters for the time window are: Fast Synchronization Mode: 6µs; Standard Synchronization Mode: 2ms; Fuzzy Synchronization Mode: 36ms. In Fast Synchronization Mode, high-precision GPS positioning has an error of only a few meters, while standard positioning has an error of no more than a few hundred meters. Therefore, a 6µs time window is sufficient. In Standard Synchronization Mode, manually entered longitude and latitude may have a larger error, but typically no more than 100km to 200km. Therefore, a 2ms time window is sufficient. In Fuzzy Synchronization Mode, since the demodulator cannot obtain any position information, it searches from the median of 45° North Latitude (45° South Latitude) toward the poles and equator. The delay difference from the poles to the equator is no more than 36ms. The median of the search window can be calculated using the satellite-to-ground delay formula. The final delay estimate must have an error of no more than 0.5Ts from the true value, where Ts is the symbol period and Ts = 1 / Rb. Digital signal processing is based on the sampling rate and is related to the symbol rate Rb, which can be obtained at the demodulator through communication parameters. When the symbol rate Rb is 40Msps, the ChinaSat 6D satellite is used as the transponder and the geographical location is Nanjing. When fast synchronization is used, the sampling rate is 4*Rb, the median value of the time window is 246.3ms, the time window is 246.297ms-246.303ms, and the number of sampling points in the corresponding window is 960; when standard synchronization is used, the sampling rate is 4*Rb, the median value of the time window is 246.3ms, the time window is 245.3ms-247.3ms, and the number of sampling points in the corresponding window is 320k; when fuzzy synchronization is used, the sampling rate is 4*Rb, the median value of the time window is 256ms, the time window is 238ms-274ms, and the number of sampling points in the corresponding window is 5760k; when the Rb parameter can be obtained, the number of points corresponding to the three modes is 6us*4*Rb, 2ms*4*Rb, and 36ms*4*Rb. When Rb is unknown, Rb=40Msps.

[0089] The specific steps of pre-setting a time window are as follows: determining a time window based on preset conditions, calculating the number of sample points within the window area, and collecting sample data of the signal to be searched; selecting different search methods based on the number of sample points; building a probability model based on the sample data to describe the probability distribution of the signal to be searched within different time windows; and selecting the time window with the highest probability of occurrence as the priority search target based on the probability model. The pre-setting number of time slots is N time slots, where N ≤ 8.

[0090] S13. Determine whether the number of sampling points within the time window is greater than 4096. If the number of sampling points within the time window is less than 4096, pad the number of sampling points to 4096. If the number of sampling points within the time window is greater than 4096 but less than 4096*8, perform a segmented search on the signal, padding the portion of the sampling points that is less than 4096 to 4096. If the number of sampling points within the time window is greater than 4096*8, extract the signal using a variable rate decimator to reduce the number of points within the time window to less than 4096*8. Perform a fast Fourier transform on the data within the signal interval that has transitioned through the sampling points to convert it into a frequency domain representation. After the fuzzy synchronization mode determines the first search, the number of sample points will be significantly reduced. In the second search, the time window must fall within the time window of fast synchronization or standard synchronization. Therefore, after optimizing the search range, the fuzzy synchronization mode is no longer entered.

[0091] S14. Take 512 local signal sequences, perform 4-fold interpolation on the local signals to obtain 2048 points, pad the tail of the local signals with zeros to 4096 points, and perform fast Fourier transform on the zero-padded local signals.

[0092] S15. Take the fast Fourier transform result, perform inverse fast Fourier transform by conjugate complex multiplication, and convert it into time domain representation.

[0093] S16. Search for a peak value in the time domain representation and determine whether the peak value is greater than a set threshold. If the peak value is greater than the set threshold, the search is successful and the process goes to step S17. If the peak value is less than the set threshold, the process goes to step S18.

[0094] S17. Record the signal interval when the search is successful, and determine whether the search has been extracted. If the signal is an unextracted signal, determine the arrival time of the signal, take a section of the signal at the arrival time, perform correlation and FFT on it, and define the ratio of the peak spectrum energy to the frequency deviation average energy in the frequency domain as the signal quality Q1. For the convenience of subsequent calculation and expression, take the logarithmic domain value of Q1 as SNRQ1; otherwise, go to step S12.

[0095] S18. Determine whether the signal interval is the last interval. If it is the last interval, go to step S11. If it is not the last interval, reselect a signal interval near the signal interval, collect data in the reselected signal interval, and go to step S13.

[0096] S2. Start the Farrow interpolation filter to interpolate the input local signal. The initial value of the interpolation coefficient is uk = 0. The initial state is the timing error position. Assume that the timing error uk = 0. Calculate the interpolation filter coefficients {c0, c1, c2, c3} based on uk, where c0 = u 3 / 6-u / 3; c1 = -u3 / 2+u 2 / 2+u;c2 = u 3 / 2-u 2 -u+1; c3 = -u 3 / 6+u 2 / 2-u / 3. Interpolate the input signal: S*(t) = c0×S(t-2) + c1×S(t-1) + c2×S(t) + c3×S(t+1); where S*(t) is the interpolated value at time t, S(t-2), S(t-1), S(t), and S(t+1) are the values ​​of the input signal two points ahead of, one point behind, the current time point, and one point behind at time t, respectively; u is used to adjust the time error between input signal sampling points.

[0097] S3. Start the phase detector module to detect the timing error ek between the local signal and the PCMA mixed signal. According to the signal quality Q1, select the appropriate phase detector correlation sequence length Ld; when the feedback loop is in the capture state and not locked, Ld is initialized to, where Ld=Lb×B: when SNRQ1>27db, Lb=2048, B=4; when 21db≤SNRQ1≤27db, Lb=2048, B=16; when SNRQ1<21db, Lb=2048, B=64; select two groups of digital signals with a length of Lb, the local signal and the PCMA mixed signal, perform correlation operation, and store the correlation operation results in RAM; then select another group of digital signals with a length of Lb for correlation operation, and add them point by point with the first group of data in RAM. In the actual FPGA programming process, the same RAM is read and written one by one to complete the update of RAM; and so on, complete the correlation operation of group B digital signals and the update of RAM data; after completing all Ld signal calculations, calculate the timing error ek.

[0098] S4. Start the loop filter module, set the loop filter parameters c0 and c1 based on the actual channel conditions, and output the corrected timing error uk. Select appropriate loop filter parameters based on signal quality Q1. When the feedback loop is in the acquisition state and unlocked, initialize c0 and c1 as follows. Due to the influence of the fixed-point bit width and sampling rate of the signal, c0 and c1 are set in a normalized manner: when SNRQ1>27dB, c0=0.08, c1=0.001; when 21dB≤SNRQ1≤27dB, c0=0.04, c1=0.001; when SNRQ1<21dB, c0=0.02, c1=0.001. Calculate the corrected timing error uk: uk = c0×ek(t) + c1×ek(t-1), where ek(t) represents the timing error of the current group (Ld versus signal), and ek(t-1) represents the timing error of the previous group (Ld versus signal).

[0099] S5. Start the interpolation coefficient calculation module, calculate the actual interpolation coefficients {c0, c1, c2, c3}, regenerate the interpolation filter according to step S2, and interpolate the next set of Ld pair data;

[0100] S6. Start the amplitude detection module, obtain the local signal and PCMA mixed signal in the synchronization module, analyze the local signal and PCMA mixed signal, and obtain the second signal quality value Q2. Start the amplitude detection module, where the amplitude estimation can be expressed as follows: h2=1 / K|∑ k=0 K-1 (Z k a* 2,k / ∣a 2,k ∣ 2 )|, where Z k is the mixed signal after frequency deviation removal, a 2,k is a known self-interference transmission sequence, a* 2,k represents the complex conjugate of the known self-interference transmission sequence, K is the correlation symbol length, h2 is the amplitude ratio of the mixed signal to the local signal, and usually 0≤h2≤10.

[0101] S7. Analyze the second signal quality value Q2. Determine the operating signal-to-noise ratio range of the loop filter. Take the logarithmic domain of h2 as SNRQ2. Adjust Lb, c0, and c1 based on SNRQ2. When adjusting Ld, follow the following rules, where Lb = 2048 remains unchanged: When SNRQ2 > 3dB, B = B-1. When B = 4, B remains unchanged. When -3dB ≤ SNRQ2 ≤ 3dB, B remains unchanged. When SNRQ2 < -3dB, B = B+1. When B = 16, B remains unchanged. When adjusting the sizes of c0 and c1, adjust according to the following rules, where c1 remains unchanged: when SNRQ2>3db, c0=c0+0.005, when c0>0.08, c0 no longer changes; when -3db≤SNRQ1≤3db, c0 remains unchanged; when SNRQ1<-3db, c0=c0-0.005, when c0<0.02, c0 no longer changes.

[0102] S8: The loop filter selects appropriate loop filter parameters based on the feedback information to enable the loop to lock as quickly as possible. Based on the updated Ld value, the phase detector reselects an appropriate correlation sequence length, repeats the operations in step S3, and re-outputs the phase detection error ek. Based on the updated c0 and c1 values, the interpolation coefficient module recalculates the interpolation coefficient uk, repeats the operations in step S5, and re-outputs the interpolation coefficient uk. This process repeats until the loop is fully locked and remains locked.

[0103] A timing synchronization device for a shipborne dual-antenna PCMA system signal, specifically comprising the following modules:

[0104] A search module, configured to search for a signal, output a capture delay and a signal interval, and calculate a first signal quality value;

[0105] The synchronization module receives the signal from the search module, performs synchronization processing on the searched signal, and outputs the synchronized signal and delay adjustment;

[0106] The cancellation module receives the signal from the synchronization module, is used to cancel the synchronized signal, eliminate the interference of the local signal on the target signal, and output the canceled signal;

[0107] an amplitude estimation module, receiving the signal from the synchronization module, and used to estimate the amplitude of the signal, and output the gain-adjusted signal and the second signal quality value;

[0108] The loop filter module receives the signal quality values ​​Q1 and Q2 from the synchronization module and is used to modify the parameters of the loop filter in real time, speed up the locking of the timing synchronization loop or the relocking speed after loss, and output a stable timing error offset.

[0109] In a further embodiment, the search module searches for the signal through inter-partition FFT to confirm the specific arrival time of the signal. When searching between partitions, considering the symbol rate and sampling rate of the local transmitted signal and the received signal, the digital signal received by AD needs to be extracted by different multiples. When calculating the signal quality Q1, the symbol rate of the local transmitted signal is 8Msps and the symbol rate of the received signal is 10Msps. For convenience, the local signal AD sampling rate and the PCMA mixed signal sampling rate are both set to 32MHz. Considering the convenience of signal search, the signal is retrieved after being extracted 128 times. Define Q1=FFT(max) / FFT(mean) to measure the signal quality of the signal captured by the PCMA demodulator, where max is the strongest frequency component of the signal and mean is the average amplitude of all frequency components; SNRQ1=20×log(Q1). When the local signal is 10dB larger than the peer signal and the local signal SNR is 5dB, SNRQ1 is 30.5dB. When the local signal is 10dB smaller than the peer signal and the local signal SNR is 5dB, SNRQ1 is 29.0dB. SNRQ1 is used to initialize the phase detector Ld parameter and the loop filter parameters c0 and c1.

[0110] In another example of calculating signal quality Q1, the local transmitted signal symbol rate is 100 ksps, and the received signal symbol rate is 120 ksps. The local signal AD sampling rate and the PCMA mixed signal sampling rate are both set to 480 kHz. To facilitate signal search, the signal is decimate-by-2 before searching. When the local signal is 10 dB greater than the peer signal and the local signal SNR is 5 dB, SNRQ1 = 24.2 dB. When the local signal is 10 dB less than the peer signal and the local signal SNR is 5 dB, SNRQ1 = 23 dB.

[0111] In the embodiment for calculating signal quality Q2, the symbol rate of the local transmitted signal is 8 Msps, and the symbol rate of the received signal is 8 Msps. The sampling rate of the local AD signal and the PCMA mixed signal is set to 32 MHz. In a PCMA communication system, the signal-to-noise ratio (SNR) must meet the demodulation thresholds for both the local signal and the peer signal. If either signal fails to meet the SNR threshold, the communication system will not function. When the local signal is 10dB larger than the peer signal and the local signal SNR = 10dB, the logarithmic domain value of the amplitude estimation parameter h2 is SNRQ2 = 20 × log(h2), and SNRQ2 = 7.12dB. When the local signal is 10dB smaller than the peer signal and the local signal SNR = 0dB, SNRQ2 = -10.5dB. When the local signal power is equal to the peer signal and the local signal SNR = 0dB, SNRQ2 = -2.5dB. SNRQ2 is used to adjust the phase detector Ld parameter and the loop filter parameters c0 and c1 during loop relocking and tracking.

[0112] When a signal is successfully recaptured after losing lock due to events such as antenna switching, this application does not immediately initiate a fixed, broadband acquisition loop. Instead, it rapidly assesses the quality of the newly acquired signal through frequency-domain correlation and peak-to-average ratio calculations, generating a quantifiable first signal quality value. This quality value is compared with preset multi-level thresholds to determine whether the initial state of the current channel is excellent, good, or poor. Based on this judgment, a set of optimally matching initial parameters (including filter coefficients and correlation sequence length) is collaboratively selected for the loop filter and phase detector from a preset parameter library. This process is completed before the loop is officially closed. As an intelligent, data-driven feedforward setting, it replaces the blind startup of traditional methods and ensures that the synchronization loop always begins operating in a manner that best suits the current channel conditions, thus resolving the problem of slow or failed recapture caused by initial parameter mismatch with the channel. After the loop enters a stable tracking state, a second signal quality value is continuously calculated, reflecting real-time power imbalance and signal-to-noise ratio changes. Two independent adjustment loops are driven in parallel and finely: the loop filter parameters are incrementally adjusted in three stages according to the quality value to control the dynamic response characteristics and tracking bandwidth of the loop; at the same time, the length of the related sequence of the phase detector is adjusted in three stages in parallel according to the quality value to control the integration time and noise suppression capability of the timing error estimation. The response characteristics of the loop filter and the input quality of the phase detector are decoupled and optimized in a coordinated manner, which is not available in traditional single-dimensional control methods. This enables the synchronization loop of the present application to always maintain the optimal balance between response speed and tracking accuracy when facing continuously changing channels such as sea surface multipath and signal fading, thereby solving the problem that the existing technology cannot perform multi-dimensional fine tracking.

[0113] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. A method for timing synchronization of shipborne dual-antenna PCMA system signals, characterized in that: include: Performing a search operation on the received PCMA mixed signal to obtain a first signal quality value representing an initial channel quality; Processing the PCMA mixed signal and the local signal to generate a timing error reflecting the timing difference between the two, and estimating a second signal quality value representing the dynamic channel characteristics; Determining loop filter parameters based on the first and second signal quality values, and using the parameters to process the timing error to output a corrected timing error; Based on the corrected timing error, the local signal is interpolated and corrected to generate a synchronized signal that is synchronized with the PCMA mixed signal; Output corrected timing errors, including: Setting initial loop filter parameters based on the first signal quality value; In response to the second signal quality value, dynamically adjusting the initial loop filter parameters or the subsequently modified parameters thereof to obtain currently used loop filter parameters; Processing the timing error using the currently used loop filter parameters and outputting the corrected timing error; Set the initial loop filter parameters, including: Comparing the first signal quality value with a preset quality threshold value including at least two different values ​​to determine a quality interval to which the first signal quality value belongs; According to the determined quality interval, a corresponding specific parameter combination is selected from a preset parameter library as an initial loop filter parameter; Get the currently used loop filter parameters, including: comparing the second signal quality value with preset upper and lower adjustment thresholds; If the second signal quality value is higher than the upper adjustment threshold, a preset increment is added to the loop filter parameter to be adjusted to obtain the currently used loop filter parameter; If the second signal quality value is lower than the lower adjustment threshold, subtracting a preset increment from the loop filter parameter to be adjusted to obtain the currently used loop filter parameter; If the second signal quality value is between the upper and lower adjustment thresholds, the loop filter parameters to be adjusted are kept unchanged and used as the loop filter parameters currently used.

2. The method according to claim 1, characterized in that Obtaining a first signal quality value, including: Perform fast Fourier transform on the PCMA mixed signal and local signal respectively to obtain the frequency domain representation of the mixed and local signals; Performing complex multiplication on the mixture and the conjugate of the frequency domain representation of the local signal, and performing inverse fast Fourier transform on the complex multiplication result to generate a time domain correlation result; The time domain correlation results are analyzed, and the ratio of the correlation peak value to the mean value is determined as the first signal quality value.

3. The method according to claim 1, characterized in that Estimating a second signal quality value, comprising: Calculate the correlation between the PCMA mixed signal and the conjugate of the local signal to obtain the mixed correlation value; Calculate the local signal's own energy to obtain the local energy value; The ratio of the amplitude of the mixed correlation value to the local energy value is calculated as the second signal quality value.

4. The method according to claim 1, wherein Generates timing errors that reflect the timing differences between the two, including: Generate auxiliary data sequence based on PCMA mixed signal and local signal; The auxiliary data sequence is shifted ahead and behind by half a symbol period respectively, and the autocorrelations of the shifted sequences are calculated to obtain leading and lagging autocorrelation functions respectively. The timing error is obtained by cross-calculating the leading and lagging autocorrelation functions.

5. The method according to claim 1, wherein Before performing a search operation on the received PCMA mixed signal, a search time window is determined, specifically: Based on the collected sample data, a probability model is established to describe the probability of the search signal appearing in different time windows; From the probability model, the time window with the highest probability of occurrence is selected as the priority search time window; Furthermore, the step of performing a search operation on the received PCMA mixed signal is performed within a priority search time window.

6. The method according to claim 2, characterized in that Before performing fast Fourier transform on the PCMA mixed signal, it also includes: Determine the relationship between the number of sampling points of the PCMA mixed signal within a preset time window and a preset first threshold and a second threshold; If the number of sampling points is less than the first threshold, data padding is performed on the PCMA mixed signal to obtain a padded signal, wherein a fast Fourier transform is performed on the padded signal; If the number of sampling points is greater than the second threshold, data extraction is performed on the PCMA mixed signal to obtain a extracted signal, wherein the fast Fourier transform is performed on the extracted signal.

7. A timing synchronization device for shipborne dual-antenna PCMA system signals, characterized in that: The timing synchronization method according to any one of claims 1 to 6 comprises: A search module, configured to perform a search operation on the received PCMA mixed signal to obtain a first signal quality value representing an initial channel quality; a signal analysis module, configured to process the PCMA mixed signal and the local signal, generate a timing error reflecting the timing difference between the two, and estimate a second signal quality value representing dynamic channel characteristics; a loop filter module, configured to determine loop filter parameters based on the first signal quality value and the second signal quality value, and use the parameters to process the timing error and output a corrected timing error; The interpolation correction module is used to perform interpolation correction on the local signal based on the corrected timing error to generate a synchronized signal that is synchronized with the PCMA mixed signal.

Images