Double-frequency signal parallel capturing method and system based on Beidou satellite signal

Abstract

The invention discloses a double-frequency signal parallel capturing method and system based on Beidou satellite signals, and relates to the technical field of signal processing, and the method comprises the steps: receiving Beidou B1I and B1C double-frequency-band signals through an antenna, and carrying out the preprocessing of the Beidou B1I and B1C double-frequency-band signals; signal quality is optimized through high-order cumulant processing, and frequencies and code phases of B1I and B1C signals are corrected through Doppler frequency shift information and navigation messages provided by an LEO satellite; and synchronously locking the frequency and the phase of the dual-frequency signal, and carrying out carrier tracking and code phase tracking on the dual-frequency signal. According to the method, the high-order cumulant is introduced to optimize the signal quality, the accuracy of signal main peak identification can be enhanced, the interference of noise and secondary peaks can be effectively suppressed, Doppler frequency shift information and navigation messages of the LEO satellite are introduced in the signal capturing stage, the accuracy of frequency offset correction is further improved, and the accuracy of signal processing is improved. The multi-frequency signal capturing precision and the anti-interference capability can be more effectively improved, and the robustness of dual-frequency signal capturing is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of signal processing, and in particular to a method and system for parallel capture of dual-frequency signals based on Beidou satellite signals. Background Art

[0002] In the field of global satellite navigation system (GNSS), Beidou Navigation Satellite System (BDS) has become one of the world's important satellite positioning systems since it was put into use. Compared with other GNSS systems, BDS has the advantage of supporting multi-band signals, especially the parallel use of dual-band B1I and B1C signals, which greatly improves anti-interference and positioning accuracy. The parallel capture and tracking of dual-frequency signals enables the receiver to better resist ionospheric delay, enhance multipath suppression, and meet the needs of precise positioning in complex environments. However, in the current dual-frequency signal capture process, many traditional methods are still limited by high signal capture delay and low anti-multipath interference ability. Especially in complex environments, such as urban high-rise building areas or complex terrain mountains, signals are easily affected by multipath effects and noise interference during reception, resulting in a decrease in signal capture efficiency and accuracy. In addition, most traditional capture technologies rely on data and positioning corrections from single-orbit satellites, lack multi-orbit data support, and are particularly limited in terms of capture speed and accuracy. In complex signal environments, existing technologies cannot ensure the synchronization and capture stability of dual-frequency signals. Summary of the invention

[0003] In view of the problems existing in the above-mentioned existing dual-frequency signal parallel acquisition method and system based on Beidou satellite signals, the present invention is proposed.

[0004] Therefore, the problem to be solved by the present invention is that in a complex signal environment, the prior art cannot ensure the synchronization and capture stability of the dual-frequency signals.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: a dual-frequency signal parallel capture method based on Beidou satellite signals, which includes receiving Beidou B1I and B1C dual-frequency band signals through an antenna and performing preprocessing; optimizing signal quality through high-order cumulant processing, and correcting the frequency and code phase of B1I and B1C signals through Doppler frequency shift information and navigation messages provided by LEO satellites; synchronously locking the frequency and phase of the dual-frequency signal and performing carrier tracking and code phase tracking on the dual-frequency signal, performing pseudo code stripping on the dual-frequency signal, extracting and storing the navigation message signals of the two frequency bands.

[0006] As a preferred solution of the dual-frequency signal parallel capture method based on Beidou satellite signals described in the present invention, wherein: the receiving of Beidou B1I and B1C dual-band signals through an antenna and preprocessing refers to using a GNSS antenna to receive Beidou B1I and B1C signals, and filtering the received B1I and B1C signals, and after low-noise amplification of the filtered B1I and B1C signals, using an analog-to-digital converter to convert the amplified analog B1I and B1C signals into digital signals.

[0007] As a preferred solution of the dual-frequency signal parallel acquisition method based on Beidou satellite signal of the present invention, wherein: the signal quality optimization by high-order cumulant processing refers to determining the pseudo code period T according to the pseudo code characteristics of the Beidou system. c , divide the received signal data into multiple time blocks, the length of each time block is an integer multiple of the pseudo code period, and extract the amplitude and phase characteristics of the signal from the divided signal data;

[0008] The delay parameter for cumulative calculation is set to τ according to the pseudo code period of the signal. 1 , τ 2 and τ 3 ;

[0009] Use the amplitude and phase of the signal to perform a fourth-order cumulant C 4 (τ 1 ,τ 2 ,τ 3 ) calculation to identify the main peak of the signal:

[0010]

[0011] Where A(t) is the amplitude of the signal, φ(t) is the phase of the signal, and A * (t+τ 1 ) is the signal at time delay τ 1 The complex conjugate amplitude at the moment, is the conjugate operation of the phase at the corresponding moment, j is the imaginary unit, A(t+τ 2 ) means that the signal is at t+τ 2 The amplitude of the moment, A * (t+τ 3 ) is the signal at t+τ 3 The complex conjugate amplitude at time, φ(t+τ 1 ),φ(t+τ 2 ) and φ(t+τ 3 ) are t+τ 1 , t+τ 2 and t+τ 3 The phase of the moment;

[0012] The expected value of the cumulative quantity using multiple signal data blocks E[C4 ]calculate:

[0013]

[0014] Where N is the number of signal blocks, is the i-th signal block at the time delay τ 1 , τ 2 and τ 3 The fourth-order cumulant results under ;

[0015] Generate a cumulant matrix based on the calculated cumulant expected value. Each element in the matrix represents the cumulant result of the signal under different delay parameters. Find the maximum value position in the cumulant matrix as the main peak position. Set the threshold Q. If the cumulant value is greater than or equal to the threshold Q, it is the main peak area, otherwise it is the secondary peak area.

[0016] Analyze the delay difference between the main peak and the secondary peak. If the secondary peak lags behind the main peak, increase the value of the delay parameter. If the secondary peak is ahead of the main peak, decrease the value of the delay parameter.

[0017] Recalculate the matrix value for the updated delay parameters and observe the change in the main peak position. If the main peak value increases and the secondary peak decreases, output the cumulant matrix after multipath interference suppression processing, mark the main peak position in the matrix, and use it as the frequency and code phase correction reference for the cumulant matrix.

[0018] As a preferred solution of the dual-frequency signal parallel acquisition method based on Beidou satellite signals of the present invention, wherein: the frequency and code phase of the B1I and B1C signals are corrected by the Doppler frequency shift information and navigation message provided by the LEO satellite, which refers to extracting the frequency offset and code phase corresponding to the main peak of the cumulant at the main peak position a corresponding to the frequency index of the cumulant matrix and the main peak position b corresponding to the code phase index, and storing the main peak frequency offset and code phase as the corrected initial input value;

[0019] The antenna receives the signal from the LEO satellite and extracts the navigation message through the BPSK / QPSK demodulation technology.

[0020] The navigation message includes the speed, position and time information of the LEO satellite;

[0021] Calculate the relative speed v between the receiver and the LEO satellite using the known position of the receiver and the three-dimensional coordinates of the LEO satellite;

[0022] The frequency offset is corrected according to the Doppler effect using the relative speed and the carrier frequency of the B1I and B1C signals:

[0023]

[0024] Where F is the corrected frequency offset, F 1 is the initial frequency offset, v is the relative speed between the receiver and the LEO satellite, c is the speed of light, q is the carrier frequency, θ is the relative angle between the receiver and the satellite, L is the path loss, and ∈ is the noise correction term;

[0025] The frequency offset corrected by Doppler frequency shift is updated to the main peak position of the cumulant matrix, replacing the previous initial frequency offset value;

[0026] After the frequency correction, the satellite clock offset in the time information is extracted, and the code phase in the cumulant matrix is ​​corrected based on the clock offset data;

[0027] The corrected code phase is updated to the main peak position of the cumulant matrix, the frequency and code phase corrected by Doppler frequency shift and clock offset are integrated into the cumulant matrix, the signal strength is measured by the signal-to-noise ratio to obtain the signal strength score, the frequency offset score and code phase score are obtained by measuring the accuracy of the frequency-locked loop and the phase-locked loop, the obtained signal strength score, frequency offset score and code phase score are weighted and fused to obtain a comprehensive capture score, and the capture score threshold is set to P. If the comprehensive capture score is greater than or equal to the threshold P, the signal meets the capture condition and starts capturing the signal, otherwise, no capture is performed.

[0028] As a preferred solution of the dual-frequency signal parallel capture method based on Beidou satellite signals described in the present invention, wherein: the synchronous locking of the frequency and phase of the dual-frequency signal and the carrier tracking and code phase tracking of the dual-frequency signal refer to that after the frequency and code phase of the B1I and B1C signals are corrected, the corrected B1I and B1C signals are respectively input into two independent PLL loops for frequency and phase locking, after the PLL completes the preliminary locking of the frequency and phase, the carrier tracking is performed through the PLL, and while the carrier tracking is being performed, the pseudo code phase is tracked through the DLL.

[0029] As a preferred solution of the dual-frequency signal parallel capture method based on Beidou satellite signals described in the present invention, the pseudo-code stripping of the dual-frequency signal and the extraction of the navigation message signal of the two frequency bands refers to generating a PRN code sequence that is identical to the received B1I and B1C signal pseudo-codes, setting three state signals of advance, quasi-synchronization and lag, comparing the correlation between the received signal pseudo-code and the local pseudo-code through DLL, continuously adjusting the pseudo-code phase until the maximum correlation is reached, removing the pseudo-code signal, extracting the navigation message signal, and obtaining complete satellite navigation information after BPSK demodulation.

[0030] As a preferred solution of the dual-frequency signal parallel capture method based on Beidou satellite signals described in the present invention, the storage refers to storing the navigation message data of the B1I and B1C signals after the pseudocode is stripped and demodulated, and storing the navigation message data in a structured manner according to the satellite orbit information and time synchronization data, and backing up the data regularly.

[0031] Another object of the present invention is to provide a dual-frequency signal parallel acquisition system based on Beidou satellite signals, which comprises:

[0032] A signal receiving module is used to receive Beidou B1I and B1C dual-frequency signals using a GNSS antenna and pre-process the signals;

[0033] Signal optimization module, used to optimize signal quality through high-order cumulant processing;

[0034] Auxiliary correction module, used to correct the frequency and code phase using the Doppler frequency shift information and navigation message of the LEO satellite;

[0035] Synchronous locking module, used to synchronously lock the frequency and phase of the dual-frequency signal, and perform carrier tracking and code phase tracking;

[0036] An extraction module is used to strip the dual-frequency signal of pseudo code and extract the navigation message signal;

[0037] The data storage module is used to store and back up the demodulated navigation message data.

[0038] A computer device comprises: a memory and a processor; the memory stores a computer program, and the processor implements the steps of a dual-frequency signal parallel acquisition method based on Beidou satellite signals when executing the computer program.

[0039] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for parallel acquisition of dual-frequency signals based on Beidou satellite signals.

[0040] The beneficial effects of the present invention are as follows: the present invention optimizes signal quality by introducing high-order cumulants, thereby enhancing the accuracy of signal main peak identification, effectively suppressing the interference of noise and secondary peaks, and introducing the Doppler frequency shift information and navigation messages of the LEO satellite in the signal capture stage, thereby further improving the accuracy of frequency offset correction, and more effectively improving the multi-frequency signal capture accuracy and anti-interference capability, thereby improving the robustness of dual-frequency signal capture. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0042] Figure 1 The figure is a flow chart of a dual-frequency signal parallel acquisition method based on Beidou satellite signals.

[0043] Figure 2 This is a structural diagram of the dual-frequency signal parallel acquisition system based on Beidou satellite signals. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0045] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0046] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0047] Example 1, reference Figure 1 , which is the first embodiment of the present invention, and which provides a dual-frequency signal parallel acquisition method based on Beidou satellite signals. The dual-frequency signal parallel acquisition method based on Beidou satellite signals includes:

[0048] S1, receive Beidou B1I and B1C dual-band signals through the antenna and perform pre-processing;

[0049] Specifically, receiving Beidou B1I and B1C dual-band signals through an antenna and performing preprocessing means using a GNSS antenna to receive Beidou B1I and B1C signals, filtering the received B1I and B1C signals, performing low-noise amplification on the filtered B1I and B1C signals, and using an analog-to-digital converter to convert the amplified analog B1I and B1C signals into digital signals.

[0050] The GNSS antenna is designed for the B1I and B1C dual-bands, enabling it to effectively capture and stably receive signals from these two bands. In the process of efficiently receiving dual-band signals, the GNSS antenna can significantly reduce the interference introduced by environmental factors, such as multipath effects and signal attenuation, which plays an important role in improving the accuracy of signal capture. The application of filters removes signal interference from other frequency bands except the B1I and B1C bands, making the spectrum of the received signal more concentrated and pure. In response to the signal attenuation problem caused by the long-distance propagation of satellite signals, the low-noise amplifier effectively improves the signal strength while maintaining signal integrity, providing good input signal conditions for subsequent analog-to-digital conversion. The high-precision sampling of the analog-to-digital converter can ensure that the signal spectrum characteristics are not distorted during the conversion process, providing accurate signal input for subsequent decoding and frequency phase adjustment processes.

[0051] S2, optimizes signal quality through high-order cumulant processing, and corrects the frequency and code phase of B1I and B1C signals through Doppler frequency shift information and navigation messages provided by LEO satellites;

[0052] Specifically, optimizing the signal quality through high-order cumulant processing refers to determining the pseudo code period T according to the pseudo code characteristics of the Beidou system. c : Where f is the chip rate. The received signal data is divided into multiple time blocks. The length of each time block is an integer multiple of the pseudo code period. The amplitude and phase characteristics of the signal are extracted from the divided signal data.

[0053] The delay parameter for cumulative calculation is set to τ according to the pseudo code period of the signal. 1 , τ 2 and τ 3 :

[0054]

[0055] Use the amplitude and phase of the signal to perform a fourth-order cumulant C 4 (τ 1 ,τ 2 ,τ 3 ) calculation to identify the main peak of the signal:

[0056]

[0057] In the formula, A(t) is the amplitude of the signal, φ(t) is the phase of the signal, which means the phase angle of the signal at time t. * (t+τ 1 ) is the signal at time delay τ 1 The complex conjugate amplitude at the moment, is the conjugate operation of the phase at the corresponding moment, j is the imaginary unit, A(t+τ 2) means that the signal is at t+τ 2 The amplitude of the moment, A * (t+τ 3 ) is the signal at t+τ 3 The complex conjugate amplitude at time, φ(t+τ 1 ),φ(t+τ 2 ) and φ(t+τ 3 ) are t+τ 1 , t+τ 2 and t+τ 3 The phase of the moment;

[0058] Compared with the existing technology, this formula improves the main peak recognition ability of the signal and suppresses the secondary peaks caused by noise and multipath effects through improvements such as amplitude and phase separation, complex conjugate operation and delay parameter optimization. The role of this formula in the cumulative amount calculation step is to enhance the main peak of the signal, suppress interference and maintain phase consistency, providing a reliable signal input for subsequent signal capture and synchronization. In the whole scheme, these improvements make the capture process more robust, ensure the synchronization performance of the dual-frequency signal, and significantly improve the accuracy and stability of signal capture;

[0059] The expected value of the cumulative quantity using multiple signal data blocks E[C 4 ]calculate:

[0060]

[0061] Where N is the number of signal blocks, which indicates the number of signal samples used to calculate the expected value. Generally, the larger N is, the more stable the expected value calculated is and the smaller the noise influence is. i 4 (τ 1 ,τ 2 ,τ 3 ) is the delay of the ith signal block at τ 1 , τ 2 and τ 3 The fourth-order cumulant results under ;

[0062] Generate a cumulant matrix according to the calculated cumulant expected value. Each element in the matrix represents the cumulant result of the signal under different delay parameters. Find the maximum value position in the cumulant matrix as the main peak position. Set the threshold Q based on the statistical characteristics of the cumulant matrix. If the cumulant value is greater than or equal to the threshold Q, it is the main peak area, otherwise it is the secondary peak area.

[0063] Analyze the delay difference between the main peak and the secondary peak. If the secondary peak lags behind the main peak, increase the value of the delay parameter. If the secondary peak is ahead of the main peak, decrease the value of the delay parameter.

[0064] Recalculate the matrix value for the updated delay parameters and observe the change of the main peak position. If the main peak value increases and the secondary peak decreases, output the cumulant matrix after multipath interference suppression processing, mark the main peak position in the matrix, and use it as the frequency and code phase correction reference of the cumulant matrix to establish the frequency index and code phase index in the cumulant matrix.

[0065] By accurately setting the pseudo code period, the periodicity of the signal can be ensured to be complete, making it easier for the receiver to lock the signal characteristics. The time block division ensures the consistency of the delay within the pseudo code period, effectively reduces the impact of signal fluctuations, and enhances the reliability of subsequent cumulative amount processing. The innovation of the fourth-order cumulative amount calculation method in signal processing lies in its high suppression of noise and multipath interference. Through the cumulative amount formula, using the signal amplitude and phase separation processing, the receiver can accurately extract the main peak in a high noise environment and effectively ignore the interference peaks from other paths. This processing makes the main peak position more prominent, allowing the receiver to capture the signal more reliably. By analyzing the delay difference between the main peak and the secondary peak and dynamically adjusting the delay parameters, the cumulative amount matrix can accurately locate the main peak. This method can suppress the secondary peak interference caused by the multipath effect in real time, significantly improving the accuracy and consistency of signal capture. By generating the cumulative amount matrix and setting the main peak identification threshold Q, the receiver can effectively distinguish the main peak and the secondary peak of the signal, avoiding false capture caused by low-intensity secondary peak interference. The cumulant results of the cumulant matrix under different delay parameters provide the receiver with multi-dimensional signal quality information, making the capture process more robust. The frequency and code phase indexes of the cumulant matrix are based on the identification of the main peak, which enables accurate positioning of the signal. Through the index of the cumulant matrix, the receiver can quickly locate the position of the main peak of the signal to further correct the frequency and code phase. This precise correction makes the capture process more stable and avoids the frequency drift problem in traditional frequency estimation. The final marking and scoring calculation of the main peak position in the cumulant matrix significantly improves the robustness of the capture. In the signal capture scoring process, the cumulant matrix results are comprehensively evaluated through the weighted fusion of signal-to-noise ratio measurement, frequency offset scoring and code phase scoring, which can effectively judge the quality of the captured signal.

[0066] Further, the frequency and code phase of the B1I and B1C signals are corrected by using the Doppler frequency shift information and navigation message provided by the LEO satellite, which means extracting the frequency offset and code phase corresponding to the main peak of the cumulant at the main peak position a corresponding to the frequency index of the cumulant matrix and at the main peak position b corresponding to the code phase index, and storing the main peak frequency offset and code phase as the initial input value of the correction;

[0067] The antenna receives the signal from the LEO satellite and extracts the navigation message through the BPSK / QPSK demodulation technology.

[0068] The navigation message includes the speed, position and time information of the LEO satellite;

[0069] Using the known position of the receiver and the three-dimensional coordinates of the LEO satellite, calculate the relative velocity v between the receiver and the LEO satellite:

[0070]

[0071] In the formula, x L ,y L and z L is the three-dimensional spatial position of the LEO satellite, x r ,y r and z r is the position of the receiver, Δt 1 is the time difference measured by the LEO satellite at two different locations;

[0072] The frequency offset is corrected according to the Doppler effect using the relative speed and the carrier frequency of the B1I and B1C signals:

[0073] The existing formula corrects the carrier frequency of the signal through a simple proportional relationship of frequency offset:

[0074]

[0075] This formula is applicable to an ideal environment, mainly considering the relative speed and the speed of light c, while ignoring other interference factors in various practical situations, such as multipath propagation, noise, path loss, etc. This will reduce the accuracy of frequency correction in a complex environment. Therefore, a correction term for the path and angle is introduced:

[0076]

[0077] Path loss varies with distance and obstacles. In complex environments, signal strength attenuation affects frequency stability. Therefore, adding a path loss term allows frequency correction to be adjusted based on the specific path of signal transmission. The relative angle between the receiver and the satellite affects the quality of signal reception. θ is introduced as a correction factor, and the angle change is nonlinearly adjusted through the sin function to reflect the dynamic impact of the receiving angle on the signal. By combining the angle and path loss information, frequency correction is more suitable for real-world scenarios, especially for complex signal propagation conditions.

[0078] Since the impact of path loss is not linear and grows logarithmically with the signal distance, to enhance the stability of the model, we introduce the natural logarithm into the path loss correction term and adjust the loss expression to:

[0079]

[0080] For changes in path loss, using the natural logarithm can limit its impact range to a more stable range, avoid excessive adjustments to the correction factor, and make the path loss correction smoother and more adaptable to actual environmental changes, thereby improving the robustness of the formula in complex environments;

[0081] In practical applications, satellite signals may be interfered by environmental noise, especially in cities or areas with complex terrain. In order to further improve the accuracy of frequency correction, an environmental noise correction term ∈ is added to compensate for possible noise effects:

[0082]

[0083] Where F is the corrected frequency offset, F 1 is the initial frequency offset, v is the relative speed between the receiver and the LEO satellite, c is the speed of light, q is the carrier frequency, θ is the relative angle between the receiver and the satellite, which is calculated by the relative position vector of the receiver and the satellite, L is the path loss, ∈ is the noise correction term, which represents the frequency offset caused by environmental noise, and is usually calculated by the environmental noise level;

[0084]

[0085] Where d is the current distance, d 0 is the reference distance,

[0086] The noise correction term can provide compensation for the noise level in different environments, making the frequency correction more stable. The noise term is divided by 1+F 1 , which can smooth the effect of noise on frequency and avoid excessive noise correction;

[0087] The frequency offset corrected by Doppler frequency shift is updated to the main peak position of the cumulant matrix, replacing the previous initial frequency offset value;

[0088] After the frequency correction, the satellite clock offset in the time information is extracted, and the code phase in the cumulant matrix is ​​corrected based on the clock offset data:

[0089] Δτ=Δh×c,

[0090] Where Δτ is the code phase correction, Δh is the satellite clock offset, and c is the speed of light;

[0091] The corrected code phase is updated to the main peak position of the cumulant matrix, the frequency and code phase corrected by Doppler frequency shift and clock offset are integrated into the cumulant matrix, the signal strength is measured by the signal-to-noise ratio to obtain the signal strength score, the frequency offset score and the code phase score are obtained by measuring the accuracy of the frequency-locked loop and the phase-locked loop, the obtained signal strength score, frequency offset score and code phase score are weighted and fused to obtain a comprehensive capture score, and the capture score threshold is set to P according to the Bayesian decision theory. If the comprehensive capture score is greater than or equal to the threshold P, the signal meets the capture condition and the signal is captured, otherwise the capture is not performed.

[0092] The frequency offset and code phase of the B1I and B1C signals are corrected through the Doppler frequency shift information and navigation messages provided by the LEO satellite. Compared with traditional medium and high orbit satellites, LEO satellites can provide more accurate relative speed information due to their lower orbits and faster moving speeds, thereby enhancing the correction accuracy of the frequency offset. Compared with the existing technology that relies on MEO satellites for Doppler frequency shift correction, it can effectively reduce the error range of the frequency offset, and is particularly suitable for environments with large dynamic changes. This design not only optimizes the frequency offset correction in complex environments, but also significantly improves the accuracy of signal capture in weak signal environments. By updating the frequency offset corrected by the Doppler frequency shift and the code phase corrected by the clock offset to the main peak position of the accumulator matrix, the accuracy and consistency of the capture process are significantly improved. The accumulator matrix combines the dynamic correction of the main peak position frequency and code phase to make the capture of dual-frequency signals more accurate and reduce the problems of false capture rate and frequency offset instability. In addition, the update of the cumulant matrix also provides a dynamically adjustable signal capture benchmark, which can achieve higher capture accuracy in areas with obvious multipath interference. The signal strength score, frequency offset score and code phase score are weighted and fused to form a comprehensive capture score, and the signal capture status is judged by the score threshold P. This scoring mechanism effectively reduces the misjudgment rate in the signal capture process and improves the accuracy of signal capture. Compared with the traditional method of making capture judgments based on a single score, the capture score after weighted fusion can more objectively reflect the signal quality, especially in complex environments with low signal-to-noise ratio. The scoring threshold can avoid false capture caused by signal fluctuations.

[0093] S3, synchronously lock the frequency and phase of the dual-frequency signal, perform carrier tracking and code phase tracking on the dual-frequency signal, perform pseudo code stripping on the dual-frequency signal, extract the navigation message signals of the two frequency bands and store them;

[0094] The receiver captures the satellite signal and obtains rough observation values ​​(Doppler frequency shift, code phase), but the accuracy of its observation value is far from meeting the requirements of positioning accuracy and navigation message demodulation. At the same time, due to the relative motion between the satellite and the receiver, if the satellite signal is not tracked continuously, the captured signal will quickly lose lock. Therefore, a tracking loop is required to track and process the signal, maintain the signal lock and achieve high-precision observation output and demodulation of the navigation message;

[0095] Specifically, synchronously locking the frequency and phase of the dual-frequency signal and performing carrier tracking and code phase tracking on the dual-frequency signal means that after the frequency and code phase of the B1I and B1C signals are corrected, the corrected B1I and B1C signals are respectively input into two independent PLL loops for frequency and phase locking, and after the PLL completes the preliminary locking of the frequency and phase, the carrier is tracked through the PLL, and while the carrier is being tracked, the pseudo code phase is tracked through the DLL.

[0096] The design of independent PLL not only avoids mutual interference between signals in different frequency bands, but also makes the signal locking of each frequency band more accurate. During the dual-frequency capture process, the frequency and phase offsets of the B1I and B1C signals may be inconsistent. The independent PLL can ensure that the two signals adapt to their own frequencies and phases, thereby reducing error accumulation during the locking stage. In addition, the PLL loop has a good noise suppression effect, which can significantly improve the phase stability of the signal and ensure the accuracy of subsequent signal processing. Carrier tracking enhances the receiver's adaptability to dual-frequency signals, especially in high-speed dynamic scenarios. Carrier tracking can compensate for frequency drift in real time, making the signal capture process more stable. This mechanism is of great value for high-precision navigation and positioning in complex environments, and effectively improves the frequency stability and demodulation accuracy of the system. The DLL refines the pseudo-code phase of the received signal through a feedback mechanism, which can ensure that the pseudo-code is strictly aligned with the signal, thereby achieving continuous tracking of the signal. Compared with traditional pseudo-code tracking, DLL is more sensitive to delay changes, so it can improve the robustness of pseudo-code locking in the case of weak signals or strong noise.

[0097] Furthermore, the dual-frequency signal is stripped of pseudocode, and the navigation message signals of the two frequency bands are extracted, which means generating a PRN code sequence that is identical to the received B1I and B1C signal pseudocodes, setting three state signals of advance, quasi-synchronization and lag, and comparing the correlation between the received signal pseudocode and the local pseudocode through DLL. The pseudocode phase is continuously adjusted until the maximum correlation is reached, the pseudocode signal is removed, the navigation message signal is extracted, and the complete satellite navigation information is obtained after BPSK demodulation.

[0098] The dual-frequency signal pseudo-code stripping has significant advantages in suppressing multipath and ionospheric interference by processing B1I and B1C signals simultaneously. Compared with the traditional single-frequency pseudo-code stripping method, dual-frequency stripping can restore the navigation message signal more accurately. This multi-frequency stripping design enhances the captured signal accuracy, so that the receiver can still stably extract reliable navigation information under high interference environment or obvious ionospheric effect conditions. In the pseudo-code stripping process, the higher the matching of the PRN code, the higher the receiver captures the received signal. The PRN code can distinguish the signals of different satellites, which helps to improve the anti-interference ability of the receiver and ensure the stability of pseudo-code synchronization. The three-state adjustment mechanism of advance, quasi-synchronous and lagging states can improve the accuracy of pseudo-code phase alignment, effectively reduce the phase difference between the received signal pseudo-code and the local pseudo-code, and thus optimize the phase synchronization process. This design ensures the dynamic adaptive ability of pseudo-code stripping, so that even when the received signal is subject to strong interference, the pseudo-code stripping still has a high accuracy. The DLL continuously adjusts the phase of the received code and the local code during the synchronization process, so that the pseudo-code stripping process achieves the best phase alignment. BPSK demodulation technology is efficient and stable in extracting complete navigation information. BPSK demodulation can accurately distinguish binary information in satellite signals and avoid bit reversal errors during the demodulation process.

[0099] Furthermore, storing means storing the navigation message data of the B1I and B1C signals after stripping the pseudo code and demodulating them, storing the navigation message data in a structured manner according to the satellite orbit information and time synchronization data, and backing up the data regularly.

[0100] The navigation message data after pseudo code stripping and demodulation has higher signal purity, which can ensure the accuracy of the stored satellite orbit information and time synchronization data. The structured storage method allows the navigation message data to be clearly organized by time and orbit information, which is conducive to efficient data management. Regular data backup can effectively prevent the loss of navigation message data caused by storage device failure or external force majeure factors, thereby ensuring the long-term security of data.

[0101] Example 2, reference Figure 2 , which is the second embodiment of the present invention, and which is different from the previous embodiment, provides a dual-frequency signal parallel acquisition system based on Beidou satellite signals, which includes:

[0102] A signal receiving module is used to receive Beidou B1I and B1C dual-frequency signals using a GNSS antenna and pre-process the signals;

[0103] Signal optimization module, used to optimize signal quality through high-order cumulant processing;

[0104] Auxiliary correction module, used to correct the frequency and code phase using the Doppler frequency shift information and navigation message of the LEO satellite;

[0105] Synchronous locking module, used to synchronously lock the frequency and phase of the dual-frequency signal, and perform carrier tracking and code phase tracking;

[0106] An extraction module is used to strip the dual-frequency signal of pseudo code and extract the navigation message signal;

[0107] The data storage module is used to store and back up the demodulated navigation message data.

[0108] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0109] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0110] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0111] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

Claims

1. A dual-frequency signal parallel acquisition method based on Beidou satellite signals, characterized in that: include, Receive Beidou B1I and B1C dual-band signals through the antenna and perform pre-processing; Optimize signal quality through high-order cumulant processing, and correct the frequency and code phase of B1I and B1C signals through Doppler frequency shift information and navigation messages provided by LEO satellites; The frequency and phase of the dual-frequency signal are synchronously locked, and the carrier and code phase of the dual-frequency signal are tracked. The pseudo code of the dual-frequency signal is stripped, and the navigation message signals of the two frequency bands are extracted and stored.

2. The method for parallel acquisition of dual-frequency signals based on Beidou satellite signals as claimed in claim 1, characterized in that: The receiving of Beidou B1I and B1C dual-band signals through an antenna and preprocessing thereof refers to using a GNSS antenna to receive Beidou B1I and B1C signals, filtering the received B1I and B1C signals, performing low-noise amplification on the filtered B1I and B1C signals, and then using an analog-to-digital converter to convert the amplified analog B1I and B1C signals into digital signals.

3. The method for parallel acquisition of dual-frequency signals based on Beidou satellite signals as claimed in claim 2, characterized in that: The optimizing of signal quality by high-order cumulant processing refers to determining the pseudo code period T according to the pseudo code characteristics of the Beidou system. c , divide the received signal data into multiple time blocks, the length of each time block is an integer multiple of the pseudo code period, and extract the amplitude and phase characteristics of the signal from the divided signal data; The delay parameters for cumulative amount calculation are set to τ1, τ2 and τ3 according to the pseudo code period of the signal; The fourth-order cumulant C4(τ1, τ2, τ3) is calculated using the amplitude and phase of the signal to identify the main peak of the signal: Where A(t) is the amplitude of the signal, φ(t) is the phase of the signal, and A * (t+τ1) is the complex conjugate amplitude of the signal at the time delay τ1, is the conjugate operation of the phase at the corresponding moment, j is the imaginary unit, A(t+τ2) is the amplitude of the signal at the moment t+τ2, A * (t+τ3) is the complex conjugate amplitude of the signal at time t+τ3, φ(t+τ1), φ(t+τ2) and φ(t+τ3) are the phases at time t+τ1, t+τ2 and t+τ3 respectively; Calculate the expected value E[C4] of the cumulative amount using multiple signal data blocks: Where N is the number of signal blocks, is the fourth-order cumulant result of the i-th signal block under time delays τ1, τ2 and τ3; Generate a cumulant matrix based on the calculated cumulant expected value. Each element in the matrix represents the cumulant result of the signal under different delay parameters. Find the maximum value position in the cumulant matrix as the main peak position. Set the threshold Q. If the cumulant value is greater than or equal to the threshold Q, it is the main peak area, otherwise it is the secondary peak area. Analyze the delay difference between the main peak and the secondary peak. If the secondary peak lags behind the main peak, increase the value of the delay parameter. If the secondary peak is ahead of the main peak, decrease the value of the delay parameter. Recalculate the matrix value for the updated delay parameters and observe the change in the main peak position. If the main peak value increases and the secondary peak decreases, output the cumulant matrix after multipath interference suppression processing, mark the main peak position in the matrix, and use it as the frequency and code phase correction reference for the cumulant matrix.

4. The method for parallel acquisition of dual-frequency signals based on Beidou satellite signals as claimed in claim 3, characterized in that: The method of correcting the frequency and code phase of the B1I and B1C signals by using the Doppler frequency shift information and navigation message provided by the LEO satellite refers to extracting the frequency offset and code phase corresponding to the main peak of the cumulant at the main peak position a corresponding to the frequency index of the cumulant matrix and the main peak position b corresponding to the code phase index, and storing the main peak frequency offset and code phase as the initial input value of the correction; The antenna receives the signal from the LEO satellite and extracts the navigation message through the BPSK / QPSK demodulation technology. The navigation message includes the speed, position and time information of the LEO satellite; Calculate the relative speed v between the receiver and the LEO satellite using the known position of the receiver and the three-dimensional coordinates of the LEO satellite; The frequency offset is corrected according to the Doppler effect using the relative speed and the carrier frequency of the B1I and B1C signals: Where F is the corrected frequency offset, F1 is the initial frequency offset, v is the relative speed between the receiver and the LEO satellite, c is the speed of light, q is the carrier frequency, θ is the relative angle between the receiver and the satellite, L is the path loss, and ∈ is the noise correction term; The frequency offset corrected by Doppler frequency shift is updated to the main peak position of the cumulant matrix, replacing the previous initial frequency offset value; After the frequency correction, the satellite clock offset in the time information is extracted, and the code phase in the cumulant matrix is ​​corrected based on the clock offset data; The corrected code phase is updated to the main peak position of the cumulant matrix, the frequency and code phase corrected by Doppler frequency shift and clock offset are integrated into the cumulant matrix, the signal strength is measured by the signal-to-noise ratio to obtain the signal strength score, the frequency offset score and code phase score are obtained by measuring the accuracy of the frequency-locked loop and the phase-locked loop, the obtained signal strength score, frequency offset score and code phase score are weighted and fused to obtain a comprehensive capture score, and the capture score threshold is set to P. If the comprehensive capture score is greater than or equal to the threshold P, the signal meets the capture condition and starts capturing the signal, otherwise, no capture is performed.

5. The method for parallel acquisition of dual-frequency signals based on Beidou satellite signals as claimed in claim 4, characterized in that: The synchronous locking of the frequency and phase of the dual-frequency signal and the carrier tracking and code phase tracking of the dual-frequency signal refer to that after the frequency and code phase of the B1I and B1C signals are corrected, the corrected B1I and B1C signals are respectively input into two independent PLL loops for frequency and phase locking, after the PLL completes the preliminary locking of the frequency and phase, the carrier tracking is performed through the PLL, and while the carrier tracking is being performed, the pseudo code phase is tracked through the DLL.

6. The method for parallel acquisition of dual-frequency signals based on Beidou satellite signals as claimed in claim 5, characterized in that: The pseudo code stripping of the dual-frequency signal and extracting the navigation message signal of the two frequency bands refers to generating a PRN code sequence identical to the received B1I and B1C signal pseudo codes, setting three state signals of advance, quasi-synchronization and lag, comparing the correlation between the received signal pseudo code and the local pseudo code through DLL, continuously adjusting the pseudo code phase until the maximum correlation is reached, removing the pseudo code signal, extracting the navigation message signal, and obtaining complete satellite navigation information after BPSK demodulation.

7. The method for parallel acquisition of dual-frequency signals based on Beidou satellite signals as claimed in claim 6, characterized in that: The storing refers to storing the B1I and B1C signal navigation message data after the pseudo code is stripped and demodulated, storing the navigation message data in a structured manner according to the satellite orbit information and time synchronization data, and backing up the data regularly.

8. A dual-frequency signal parallel acquisition system based on Beidou satellite signals based on the dual-frequency signal parallel acquisition method based on Beidou satellite signals according to any one of claims 1 to 7, characterized in that: include, A signal receiving module is used to receive Beidou B1I and B1C dual-frequency signals using a GNSS antenna and pre-process the signals; Signal optimization module, used to optimize signal quality through high-order cumulant processing; Auxiliary correction module, used to correct the frequency and code phase using the Doppler frequency shift information and navigation message of the LEO satellite; Synchronous locking module, used to synchronously lock the frequency and phase of the dual-frequency signal, and perform carrier tracking and code phase tracking; An extraction module is used to strip the dual-frequency signal of pseudo code and extract the navigation message signal; The data storage module is used to store and back up the demodulated navigation message data.

9. A computer device comprising: Memory and processor; The memory stores a computer program, characterized in that: when the processor executes the computer program, the steps of the dual-frequency signal parallel acquisition method based on Beidou satellite signals described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the dual-frequency signal parallel acquisition method based on Beidou satellite signals described in any one of claims 1 to 7 are implemented.

Images