A dual-frequency signal parallel acquisition method and system based on Beidou satellite signals

Abstract

The application discloses a kind of based on Beidou satellite signal dual-frequency signal parallel acquisition method and system, it is related to signal processing technical field, including through antenna receiving Beidou B1I and B1C dual-band signal and carrying out pre-processing;Through high-order cumulant processing optimization signal quality, and through the Doppler frequency shift information and navigation message provided by LEO satellite are corrected to B1I and B1C signal frequency and code phase;Synchronous locking dual-frequency signal frequency and phase and carrying out carrier tracking and code phase tracking to dual-frequency signal.The application can enhance the accuracy of signal main peak identification by introducing high-order cumulant optimization signal quality, effectively suppress the interference of noise and sub-peak, introduce the Doppler frequency shift information and navigation message of LEO satellite in signal acquisition stage, further improve the accuracy of frequency offset correction, can more effectively improve multi-frequency signal acquisition precision and anti-interference ability, improve the robustness of dual-frequency signal acquisition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of signal processing, in particular to a double-frequency signal parallel acquisition method and system based on Beidou satellite signals. BACKGROUND

[0002] In the field of global satellite navigation system (GNSS), since the Beidou satellite navigation system (BDS) has been put into use, it has become one of the important satellite positioning systems in the world. Compared with other GNSS systems, the BDS has the advantage of supporting multi-band signals, especially the parallel use of double-band B1I and B1C signals, which greatly improves the anti-interference and positioning accuracy. The parallel acquisition and tracking of double-frequency signals enable the receiver to better resist ionospheric delay and enhance multipath suppression, meeting the demand for accurate positioning in complex environments. However, in the current double-frequency signal acquisition process, many traditional methods are still limited by high signal acquisition delay and low anti-multipath interference capability. Especially in complex environments, such as urban high-rise building areas or complex terrain mountainous areas, the signal is easily affected by multipath effect and noise interference during reception, resulting in a decline in signal acquisition efficiency and accuracy. In addition, traditional acquisition techniques mostly rely on single-orbit satellite data and positioning correction, lack of multi-orbit data support, and are limited in acquisition speed and accuracy, especially in complex signal environments, the existing technology cannot ensure the synchronization and acquisition stability of double-frequency signals. SUMMARY

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

[0004] Therefore, the problem to be solved by the present application is that in complex signal environments, the existing technology cannot ensure the synchronization and acquisition stability of double-frequency signals.

[0005] To solve the above technical problems, the present application provides the following technical scheme: a double-frequency signal parallel acquisition method based on Beidou satellite signals, which comprises receiving and preprocessing Beidou B1I and B1C double-band signals through an antenna; 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 double-frequency signals and performing carrier tracking and code phase tracking on double-frequency signals, stripping the pseudo code of double-frequency signals, extracting and storing the navigation message signals of the two frequency bands.

[0006] As a preferred scheme of the parallel acquisition method of the dual-frequency signal based on the Beidou satellite signal according to the application, the step of receiving the Beidou B1I and B1C dual-frequency signals through an antenna and preprocessing the signals comprises the following steps: receiving the Beidou B1I and B1C signals through a GNSS antenna, filtering the received B1I and B1C signals, amplifying the filtered B1I and B1C signals through a low-noise amplifier, and converting the amplified analog B1I and B1C signals into digital signals through an analog-to-digital converter.

[0007] As a preferred scheme of the parallel acquisition method of the dual-frequency signal based on the Beidou satellite signal according to the application, the step of optimizing the signal quality through high-order cumulant processing comprises the following steps: determining the pseudo-code period T according to the pseudo-code characteristics of the Beidou system, c dividing the received signal data into a plurality of time blocks, each time block having a length of an integer multiple of the pseudo-code period, and extracting the amplitude and phase characteristics of the signals from the divided signal data;

[0008] The time delay parameters of the cumulant calculation are τ1, τ2 and τ3 according to the pseudo-code period of the signals;

[0009] The fourth-order cumulant C4(τ1, τ2, τ3) is calculated using the amplitude and phase of the signals, and the main peak of the signals is identified;

[0010]

[0011] In the formula, A(t) is the amplitude of the signals, φ(t) is the phase of the signals, A * (t+τ1) is the complex conjugate amplitude of the signals at time t+τ1, is the conjugate operation of the phase at the corresponding time, j is an imaginary unit, A * (t+τ3) is the complex conjugate amplitude of the signals at time t+τ3, φ(t+τ1), φ(t+τ2) and φ(t+τ3) are the phases at times t+τ1, t+τ2 and t+τ3, respectively;

[0012] The expected value E[C4] of the cumulant is calculated using a plurality of signal data blocks:

[0013]

[0014] In the formula, N is the number of signal blocks, is the fourth-order cumulant result of the i-th signal block at time delays τ1, τ2 and τ3;

[0015] According to the calculated cumulative value expectation, a cumulative value matrix is generated, each element in the matrix representing the cumulative value result of the signal under different time delay parameters, the maximum value position in the cumulative value matrix is found as the main peak position, a threshold Q is set, if the cumulative value is greater than or equal to the threshold Q, it is the main peak region, otherwise it is the sub-peak region;

[0016] The time delay difference between the main peak and the sub-peak is analyzed, if the sub-peak lags behind the main peak, the value of the time delay parameter is increased, if the sub-peak is ahead of the main peak, the value of the time delay parameter is reduced;

[0017] The matrix value is recalculated for the updated time delay parameter, the change of the main peak position is observed, if the main peak value increases and the sub-peak decreases, the cumulative value matrix after the multipath interference suppression processing is output, the main peak position in the matrix is marked, and is used as the frequency and code phase correction reference of the cumulative value matrix.

[0018] As a preferred scheme of the parallel acquisition method of the dual-frequency signal based on the Beidou satellite signal, wherein: the Doppler frequency shift information and the navigation message provided by the LEO satellite are used to correct the frequency and code phase of the B1I and B1C signals, the frequency offset and the code phase corresponding to the main peak are extracted at the main peak position a corresponding to the frequency index and the main peak position b corresponding to the code phase index of the cumulative value matrix, and the main peak frequency offset and the code phase are stored as the corrected initial input value;

[0019] The signal of the LEO satellite is received through an antenna, and the navigation message is extracted through BPSK / QPSK demodulation technology,

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

[0021] The relative speed v between the receiver and the LEO satellite is calculated through 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 through the relative speed and the carrier frequency of the B1I and B1C signals:

[0023]

[0024] In the formula, 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;

[0025] The frequency offset corrected through the Doppler frequency shift is updated to the main peak position of the cumulative value 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 accumulated matrix is corrected based on the clock offset data;

[0027] The corrected code phase is updated to the main peak position of the accumulated matrix, the frequency and code phase corrected by the Doppler frequency shift and clock offset are integrated into the accumulated matrix, the signal strength score is obtained by measuring the signal strength through the signal-to-noise ratio, the frequency offset score and the code phase score are obtained by measuring the accuracy through 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 acquisition score, and the acquisition score threshold is set as P. If the comprehensive acquisition score is greater than or equal to the threshold P, the signal meets the acquisition condition, and the signal is acquired, otherwise, the acquisition is not performed.

[0028] As a preferred scheme of the parallel acquisition method of the dual-frequency signal based on the Beidou satellite signal, wherein: the frequency and phase of the dual-frequency signal are locked and carrier tracking and code phase tracking are performed on the dual-frequency signal. After the B1I and B1C signals are corrected in frequency and code phase, the corrected B1I and B1C signals are input into two independent PLL loops for frequency and phase locking. After the PLL completes the preliminary locking of the frequency and phase, carrier tracking is performed through the PLL, and at the same time, the pseudo-code phase is tracked through the DLL.

[0029] As a preferred scheme of the parallel acquisition method of the dual-frequency signal based on the Beidou satellite signal, wherein: the pseudo-code of the dual-frequency signal is stripped, and the navigation message signals of the two frequency bands are extracted. A PRN code sequence same as the received B1I and B1C signal pseudo-code is generated, three state signals of advance, quasi-synchronization and lag are set, the correlation of the received signal pseudo-code and the local pseudo-code is compared through the DLL, the pseudo-code phase is continuously adjusted until the maximum correlation is reached, the pseudo-code signal is removed, and the navigation message signal is extracted. After BPSK demodulation, complete satellite navigation information is obtained.

[0030] As a preferred scheme of the parallel acquisition method of the dual-frequency signal based on the Beidou satellite signal, wherein: the storage is performed. The B1I and B1C signal navigation message data after the pseudo-code stripping and demodulation is stored, and the navigation message data is stored according to the satellite orbit information and time synchronization data structure, and data backup is performed regularly.

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

[0032] The signal receiving module is used for receiving the Beidou B1I and B1C dual-frequency signals using the GNSS antenna and pre-processing the signals.

[0033] A signal optimization module is configured to optimize signal quality through high-order cumulant processing.

[0034] An auxiliary correction module is configured to correct frequency and code phase by using Doppler frequency shift information and navigation message of the LEO satellite.

[0035] A synchronization locking module is configured to synchronize frequency and phase of the dual-frequency signal and perform carrier tracking and code phase tracking.

[0036] An extraction module is configured to perform pseudo-code stripping on the dual-frequency signal and extract the navigation message signal.

[0037] A data storage module is configured to store and backup 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 steps of a parallel acquisition method of dual-frequency signals based on Beidou satellite signals when executing the computer program.

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

[0040] The present application has the following beneficial effects: the present application can enhance the accuracy of signal main peak identification, effectively suppress the interference of noise and side peaks, and further improve the accuracy of frequency offset correction by introducing high-order cumulant to optimize signal quality, LEO satellite Doppler frequency shift information and navigation message in the signal acquisition stage, which can more effectively improve the multi-frequency signal acquisition accuracy and anti-interference ability, and improve the robustness of dual-frequency signal acquisition. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0042] Figure 1 It is a flowchart of the parallel acquisition method of dual-frequency signals based on Beidou satellite signals.

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

[0044] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0045] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application, however, can be practiced in a variety of ways beyond the specific embodiments described herein without departing from the scope of the present application, and it is understood that variations can be made in view of what is described herein, by a worker of ordinary skill in the art, without departing from the spirit and scope of the present application.

[0046] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor does it mean an embodiment that is separate or selectively excluded from other embodiments.

[0047] Embodiment 1, with reference to Figure 1 For the first embodiment of the present application, the embodiment 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 comprises,

[0048] S1, receiving Beidou B1I and B1C dual-band signals through an antenna and pre-processing;

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

[0050] The design of the GNSS antenna for B1I and B1C dual-band enables it to effectively capture and stably receive signals of the two frequency 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 effect and signal attenuation, which plays an important role in improving the accuracy of signal acquisition. The application of the filter removes the interference of signals of other frequency bands except B1I and B1C frequency bands, making the frequency spectrum of the received signals more concentrated and pure. For the problem of signal attenuation caused by long-distance propagation of satellite signals, the low-noise amplifier effectively improves the signal strength while maintaining the integrity of the signal, 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 and phase adjustment processes.

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

[0052] Specifically, optimizing signal quality through high-order cumulant processing refers to determining the pseudo-code period T of the Beidou system according to the pseudo-code characteristics of the Beidou system c : In the formula, f is the chip rate, the received signal data is divided into multiple time blocks, and 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 signal data after the division.

[0053] According to the pseudo-code period of the signal, the time delay parameters for cumulant calculation are τ1, τ2 and τ3:

[0054]

[0055] The amplitude and phase of the signal are used to calculate the fourth-order cumulant C4(τ1, τ2, τ3), and the main peak of the signal is identified:

[0056]

[0057] In the formula, A(t) is the amplitude of the signal, φ(t) is the phase of the signal, φ(t) represents the phase angle of the signal at time t, A * (t+τ1) is the complex conjugate amplitude of the signal at time t+τ1, is the conjugate operation of the phase at the corresponding time, j is the imaginary unit, A(t+τ2) is the amplitude of the signal at time 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 t+τ1, t+τ2 and t+τ3, respectively.

[0058] Compared with the prior art, the formula improves the main peak identification ability of the signal, suppresses the side peaks caused by noise and multipath effects, and enhances the signal main peak, suppresses interference and maintains phase consistency in the cumulant calculation step. This formula provides reliable signal input for subsequent signal acquisition and synchronization. In the entire scheme, these improvements make the acquisition process more robust, ensure the synchronization performance of the dual-frequency signal, and significantly improve the precision and stability of signal acquisition;

[0059] The expectation value E[C4] of the cumulant is calculated using multiple signal data blocks:

[0060]

[0061] where N is the number of signal blocks, indicates the number of signal samples used in calculating the expectation value, generally, the larger N is, the more stable the calculated expectation value is, and the less the noise influence is, C i 4(τ1,τ2,τ3) is the fourth-order cumulant result of the i-th signal block at time delays τ1, τ2 and τ3;

[0062] A cumulant matrix is generated according to the calculated cumulant expectation value, each element in the matrix represents the cumulant result of the signal at different time delay parameters, the maximum value position in the cumulant matrix is found as the main peak position, a threshold Q is set 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 region, otherwise it is the secondary peak region;

[0063] The time delay difference between the main peak and the secondary peak is analyzed, if the secondary peak lags behind the main peak, the value of the time delay parameter is increased, if the secondary peak is ahead of the main peak, the value of the time delay parameter is decreased;

[0064] The matrix value is recalculated for the updated time delay parameter, the change of the main peak position is observed, if the main peak value increases and the secondary peak decreases, the cumulant matrix after multipath interference suppression processing is output, the main peak position in the matrix is marked, and is used as the frequency and code phase correction reference of the cumulant matrix, the frequency index and the code phase index in the cumulant matrix are established.

[0065] By accurately setting the pseudo-code period, the periodicity of the signal can be ensured, and the receiver can lock the signal characteristics. Time block division ensures the consistency of time delay within the pseudo-code period, effectively reduces the influence of signal fluctuations, and enhances the reliability of subsequent cumulative processing. The innovation of the fourth-order cumulative calculation method in signal processing lies in its high suppression of noise and multipath interference. Through the cumulative formula and using 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, enabling the receiver to more reliably capture the signal. By analyzing the time delay difference between the main peak and the secondary peak and dynamically adjusting the time delay parameter, the cumulative matrix can accurately locate the main peak. This method can real-time suppress the secondary peak interference caused by multipath effect, significantly improving the accuracy and consistency of signal acquisition. By generating a cumulative matrix and setting a main peak recognition 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 cumulative results of the cumulative matrix under different time delay parameters provide the receiver with multi-dimensional signal quality information, making the acquisition process more robust. The frequency and code phase indexes of the cumulative matrix are based on the recognition of the main peak, achieving accurate positioning of the signal. Through the index of the cumulative matrix, the receiver can quickly locate the position of the main peak of the signal for further correction of the frequency and code phase. This accurate correction makes the acquisition process more stable, avoiding the problem of frequency drift in traditional frequency estimation. The final labeling and score calculation of the main peak position in the cumulative matrix significantly improve the robustness of the acquisition. In the signal acquisition score process, the cumulative matrix results are comprehensively evaluated by measuring the signal-to-noise ratio, weighting the frequency offset score and the code phase score, and effectively judging the quality of the acquired signal.

[0066] Further, the Doppler shift information provided by the LEO satellite and the navigation message are used to correct the frequency and code phase of the B1I and B1C signals. At the main peak position a corresponding to the frequency index of the cumulative matrix and the main peak position b corresponding to the code phase index, the frequency offset and code phase corresponding to the main peak of the cumulative matrix are extracted, and the main peak frequency offset and code phase are stored as the corrected initial input values.

[0067] The signal of the LEO satellite is received by the antenna, and the navigation message is extracted by BPSK / QPSK demodulation technology,

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

[0069] The relative speed v between the receiver and the LEO satellite is calculated based on the known position of the receiver and the three-dimensional coordinates of the LEO satellite.

[0070]

[0071] where x L , y L and z L are the three-dimensional spatial positions of the LEO satellite, x r , y r and z r are the positions of the receiver, and Δt1 is the measured time difference of the LEO satellite at two different positions.

[0072] The frequency offset is corrected according to the Doppler effect through the relative velocity 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 the frequency offset:

[0074]

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

[0076]

[0077] The path loss will change with the distance and obstacles, and the signal strength attenuation in a complex environment will affect the frequency stability. Therefore, by adding the path loss term, the frequency correction can be adjusted according to the specific path of signal transmission. The relative angle between the receiver and the satellite will affect the reception quality of the signal. The angle θ is introduced as a correction factor to adjust the change of the angle through the sin function in a non-linear manner to reflect the dynamic influence of the receiving angle on the signal. By combining the angle and path loss information, the frequency correction is more suitable for real scenarios, especially in complex signal propagation conditions.

[0078] Since the influence of path loss is not linear and increases logarithmically with the signal distance, we introduce the natural logarithm in the path loss correction term and adjust the loss expression as follows:

[0079]

[0080] For the change of path loss, using the natural logarithm can limit its influence range to a more stable interval, avoiding excessive adjustment of the correction factor, and can make the path loss correction more smooth and more adaptive to actual environmental changes, thereby improving the robustness of the formula in complex environments.

[0081] In practical applications, satellite signals will be disturbed by environmental noise, especially in urban or complex terrain areas, in order to further improve the accuracy of frequency correction, an environmental noise correction term ∈ is added to compensate for the possible noise influence:

[0082]

[0083] In the formula, 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, which is calculated by the relative position vectors 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] In the formula, d is the current distance, d0 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. By dividing the noise term by 1+F1, the influence of noise on frequency can be smoothed, and over-correction of noise can be avoided.

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

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

[0089] Δτ=Δh×c,

[0090] In the formula, 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 accumulation matrix, and the frequency and code phase corrected by the Doppler frequency shift and clock offset are integrated into the accumulation matrix. The signal strength score is obtained by measuring the signal strength through the signal-to-noise ratio, and the frequency offset score and code phase score are obtained by measuring the accuracy of the frequency lock loop and the phase lock loop. The signal strength score, frequency offset score and code phase score are weighted and fused to obtain a comprehensive acquisition score. According to the Bayesian decision theory, the acquisition score threshold P is set. If the comprehensive acquisition score is greater than or equal to the threshold P, the signal meets the acquisition condition, and the signal is acquired. Otherwise, no acquisition is performed.

[0092] The Doppler shift information provided by the LEO satellite and the navigation message correct the frequency offset and code phase of the B1I and B1C signals. Compared with traditional medium-high orbit satellites, LEO satellites can provide more accurate relative velocity information due to their lower orbit and faster movement, thereby enhancing the correction accuracy of frequency offset. Compared with the existing technology that relies on the Doppler shift correction of MEO satellites, the error range of the frequency offset can be effectively reduced, which 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 acquisition in weak signal environments. By updating the frequency offset after Doppler shift correction and the code phase after clock offset correction to the main peak position of the accumulation matrix, the accuracy and consistency of the acquisition process are significantly improved. The dynamic correction of the main peak position frequency and code phase in the accumulation matrix makes the acquisition of dual-frequency signals more accurate, reducing the false capture rate and frequency offset instability. In addition, the update of the accumulation matrix also provides a dynamically adjustable signal acquisition reference, which can achieve higher acquisition accuracy in areas with significant multipath interference. The signal strength score, frequency offset score, and code phase score are weighted and fused to form a comprehensive acquisition score, and the signal acquisition state is judged by the score threshold P. This scoring mechanism effectively reduces the false positive rate in the signal acquisition process and improves the accuracy of signal acquisition. Compared with the traditional method of determining acquisition only based on a single score, the weighted and fused acquisition score can more objectively reflect the signal quality, especially in complex environments with low signal-to-noise ratio. The score threshold can avoid false acquisition caused by signal fluctuations.

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

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

[0095] Specifically, the frequency and phase of the synchronous locked dual-frequency signal are locked, and the dual-frequency signal is subjected to carrier tracking and code phase tracking. 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 at the same time of the carrier tracking, the pseudo-code phase is tracked through the DLL.

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

[0097] Further, the pseudo-code of the dual-frequency signal is stripped, and the navigation message signals of the two frequency bands are extracted. The PRN code sequence same as the received B1I and B1C signal pseudo-code is generated, three state signals of advance, quasi-synchronous and lag are set, the correlation of the received signal pseudo-code and the local pseudo-code is compared through the DLL, the pseudo-code phase is continuously adjusted until the maximum correlation is reached, the pseudo-code signal is removed, and the navigation message signal is extracted. After BPSK demodulation, complete satellite navigation information is obtained.

[0098] The code stripping of the dual-frequency signal has significant advantages in the suppression of multipath and ionospheric interference by processing the B1I and B1C signals simultaneously. Compared with the traditional single-frequency code stripping method, the dual-frequency stripping can restore the navigation message signal more accurately. This multi-frequency stripping design enhances the accuracy of the captured signal, enabling the receiver to still extract reliable navigation information in a high-interference environment or under conditions where the ionospheric effect is significant. In the code stripping process, the higher the matching of the PRN code, the higher the capture accuracy of the receiver to the received signal. The use of 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 the code synchronization. The three-state adjustment mechanism of advance, quasi-synchronization and lag can improve the accuracy of the code phase alignment, effectively reducing the phase difference between the received signal code and the local code, thereby optimizing the phase synchronization process. This design ensures the dynamic adaptive ability of the code stripping, so that even in the case of strong interference of the received signal, the code stripping still has high accuracy. The DLL continuously adjusts the phase of the received code and the local code during the synchronization process, so that the code stripping process achieves the best phase alignment. The BPSK demodulation technology has high efficiency and stability in extracting complete navigation information. BPSK demodulation can accurately distinguish the binary information in the satellite signal and avoid bit inversion errors in the demodulation process.

[0099] Further, the navigation message data of the B1I and B1C signals stripped of the code and demodulated are stored, and the navigation message data are stored according to the structure of the satellite orbit information and the time synchronization data and backed up regularly.

[0100] The navigation message data stripped of the code and demodulated have higher signal purity, which can ensure the accuracy of the stored satellite orbit information and time synchronization data. The structured storage makes the navigation message data clearly organized according to time and orbit information, which is helpful for efficient data management. Regular data backup can effectively prevent the loss of navigation message data caused by storage device failure or external irresistible factors, thereby ensuring the long-term security of the data.

[0101] Embodiment 2, refer to Figure 2 As a second embodiment of the present application, this embodiment is different from the previous embodiment, and provides a dual-frequency signal parallel acquisition system based on Beidou satellite signals, which comprises,

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

[0103] A signal optimization module is used to optimize the signal quality by high-order cumulant processing.

[0104] An auxiliary correction module is configured to correct the frequency and code phase by using the Doppler shift information of the LEO satellite and the navigation message;

[0105] A synchronization locking module is configured to synchronize the frequency and phase of the dual-frequency signal and perform carrier tracking and code phase tracking;

[0106] An extraction module is configured to perform pseudo-code stripping on the dual-frequency signal and extract the navigation message signal;

[0107] A data storage module is configured to store and backup the demodulated navigation message data.

[0108] If the functions are realized in the form of software function units and sold or used as independent products, the functions can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application or the parts of the present application that essentially contribute to the prior art or the parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various program code storage media.

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

[0110] More specific examples (a non-exhaustive list) of the computer-readable medium include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, for example, via an optical scanner, then compiled, interpreted, or otherwise processed, and stored in a computer memory in a form that is then employable by a computer. Examples of computer-readable media include but are not limited to portable computer disks, hard disks, RAM, ROM, EEPROM, and optical

[0111] It should be understood that aspects of the application can be implemented in hardware, software, firmware or combinations thereof. In the embodiments described above, various steps or methods can be implemented, for example, in software or firmware that is stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any of the following technologies, or combinations thereof, can be used: a discrete logic circuit having logic gates for implementing logic functions upon data signals, an application specific integrated circuit having appropriate combinational logic gates, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

Claims

1. A method for parallel acquisition of dual-frequency signals based on BeiDou satellite signals, characterized in that: The application relates to a method for acquiring a signal of a Beidou satellite. B1I and B1C dual-band signals of the Beidou satellite are received through an antenna and pretreated; Signal quality is optimized through high-order cumulant processing, and the frequency and code phase of the B1I and B1C signals are corrected through Doppler frequency shift information and navigation messages provided by a LEO satellite; The frequency and phase of the dual-band signals are locked and the dual-band signals are subjected to carrier tracking and code phase tracking, the dual-band signals are subjected to pseudo code stripping, navigation message signals of the two frequency bands are extracted and stored; The frequency and code phase of the B1I and B1C signals are corrected through Doppler frequency shift information and navigation messages provided by a LEO satellite, frequency offset and code phase corresponding to the main peak of the cumulant are extracted 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 the main peak frequency offset and code phase are stored as corrected initial input values; The signals of the LEO satellite are received through the antenna, and navigation messages are extracted through BPSK / QPSK demodulation technology, The navigation messages include velocity, position and time information of the LEO satellite; The relative velocity v between the receiver and the LEO satellite is calculated through 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 through the relative velocity and the carrier frequency of the B1I and B1C signals: ， where F is the corrected frequency offset, is the initial frequency offset, v is the relative velocity between the receiver and the LEO satellite, c is the speed of light, q is the carrier frequency, is the relative angle between the receiver and the satellite, and L is the path loss, is the noise correction term; The frequency offset corrected through the 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, and the frequency and code phase corrected through the Doppler frequency shift and the clock offset are integrated into the cumulant matrix, the signal strength score is obtained through the signal-to-noise ratio measurement signal strength, the frequency offset score and the code phase score are obtained through the frequency lock loop and the phase lock loop precision measurement, the obtained signal strength score, frequency offset score and code phase score are weighted and fused to obtain a comprehensive acquisition score, the acquisition score threshold P is set, if the comprehensive acquisition score is greater than or equal to the threshold P, the signal meets the acquisition condition, and the signal is acquired, otherwise, the acquisition is not performed.

2. The method according to claim 1, wherein the method is characterized by: The B1I and B1C dual-band signals of the Beidou satellite are received through an antenna and pretreated, the B1I and B1C signals are received through a GNSS antenna, the received B1I and B1C signals are filtered, the filtered B1I and B1C signals are subjected to low-noise amplification, and then the amplified analog B1I and B1C signals are converted into digital signals through an analog-to-digital converter.

3. The method for parallel acquisition of dual-frequency signals based on BeiDou satellite signals as described in claim 2, characterized in that: The signal quality is optimized by high-order cumulant processing The received signal data is divided into multiple time blocks, each time block has a length of an integer multiple of the pseudo code period, and the amplitude and phase characteristics of the signal are extracted from the divided signal data. The time delay parameter calculated according to the pseudo code period of the signal is set as , and ; Fourth order cumulants using amplitude and phase of signals computing, identifying a main peak of the signal: ， where A(t) is the amplitude of the signal, is the phase of the signal, is the complex conjugate amplitude of the signal at time delay , is the conjugate operation of the phase at the corresponding time instant, j is the imaginary unit, is the amplitude of the signal at time delay , is the complex conjugate amplitude of the signal at time delay , , and are the phases at time delay , and respectively. Using multiple signal data blocks for cumulants' expected values Calculation: ， where N is the number of signal blocks, is the fourth order cumulant result of the ith signal block at time delay , and ​ A cumulant matrix is generated according to the calculated cumulant expected value, each element in the matrix represents the cumulant result of the signal under different time delay parameters, the maximum value position is found as the main peak position in the cumulant matrix, a threshold Q is set, if the cumulant value is greater than or equal to the threshold Q, the position is a main peak region, otherwise, the position is a sub-peak region; The time delay difference between the main peak and the sub-peak is analyzed. If the sub-peak lags behind the main peak, the value of the time delay parameter is increased; if the sub-peak leads the main peak, the value of the time delay parameter is decreased. The matrix value is recalculated according to the updated time delay parameter, and the change of the main peak position is observed. If the main peak value increases and the sub-peak decreases, the cumulant matrix after the multipath interference suppression processing is output, the main peak position in the matrix is marked, and the frequency and code phase correction reference of the cumulant matrix is taken.

4. The method according to claim 3, wherein the method comprises the following steps: The frequency and phase of the synchronous locked double frequency signal are locked, and the double frequency signal is subjected to carrier tracking and code phase tracking. After the frequency and code phase of the B1I and B1C signals are corrected, the corrected B1I and B1C signals are 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. At the same time of the carrier tracking, the pseudo code phase is tracked through the DLL.

5. The method according to claim 4, wherein the method comprises the following steps: The pseudo code of the double frequency signal is stripped, and the navigation message signals of the two frequency bands are extracted. The PRN code sequence same as the pseudo code of the received B1I and B1C signals is generated. The three state signals of advance, quasi-synchronization and lag are set. The correlation between the received signal pseudo code and the local pseudo code is compared through the DLL. The pseudo code phase is continuously adjusted until the maximum correlation is reached. The pseudo code signal is removed, and the navigation message signal is extracted. After the BPSK demodulation, the complete satellite navigation information is obtained.

6. The method according to claim 5, wherein the method further comprises: determining the number of the satellites in the constellation of the BDS based on the number of the satellites in the constellation of the GPS. The B1I and B1C signal navigation message data after the pseudo code stripping and demodulation are stored. The navigation message data is stored according to the structure of the satellite orbit information and the time synchronization data, and the data backup is performed regularly.

7. A Beidou satellite signal based dual-frequency signal parallel acquisition system based on the Beidou satellite signal based dual-frequency signal parallel acquisition method of any one of claims 1-6, characterized in that: The method comprises the following steps: The signal receiving module is used for receiving the Beidou B1I and B1C double frequency signals using the GNSS antenna and pre-processing the signals; The signal optimization module is used for optimizing the signal quality through high-order cumulant processing; The auxiliary correction module is used for correcting the frequency and code phase using the Doppler frequency shift information and the navigation message of the LEO satellite; The synchronous locking module is used for synchronously locking the frequency and phase of the double frequency signal, and performing carrier tracking and code phase tracking; The extraction module is used for stripping the pseudo code of the double frequency signal, and extracting the navigation message signal; The data storage module is used for storing and backing up the demodulated navigation message data.

8. A computer device comprising: A memory and a processor; The memory stores a computer program. When the processor executes the computer program, the steps of the parallel acquisition method of the double frequency signal based on the Beidou satellite signal are implemented.

9. A computer readable storage medium having stored thereon a computer program, characterized in that: The computer program is executed by the processor to implement the steps of the parallel acquisition method of the double frequency signal based on the Beidou satellite signal.

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