Parallel code phase and orthogonal basis matching joint navigation satellite signal capturing method

Abstract

The invention relates to a parallel code phase and orthogonal basis matching joint navigation satellite signal capturing method, and belongs to the technical field of satellite navigation. Aiming at the problems of limited frequency offset estimation precision and insufficient anti-noise capability of the existing method, the invention provides a two-stage acquisition architecture which comprises the following steps: S1, generating a local pseudo code of a target satellite and receiving a signal; s2, a parallel code phase search algorithm is combined with oversampling and double-peak detection to realize coarse capture, and initial frequency offset and a code phase are output; s3, iteratively screening frequency components and updating weights through an orthogonal basis matching method based on the roughly captured frequency offset range; and S4, extracting three frequencies with the maximum weight and adjacent to the three frequencies, and solving an extreme point as a final frequency offset through quadratic function fitting. The method effectively inhibits noise interference, breaks through the limitation of spectrum resolution, achieves sub-sampling level frequency offset estimation, gives consideration to real-time performance and high precision, and is suitable for a high-dynamic satellite navigation scene.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite navigation and relates to a joint navigation satellite signal capture method for matching parallel code phase with orthogonal basis. Background Art

[0002] Satellite communication technology is widely used in navigation and positioning due to its advantages, including long communication distances, wide coverage, minimal signal transmission interference, and strong adaptability to geographical environments. Global satellite navigation systems, a key application, provide real-time three-dimensional coordinate, velocity, and timing services, playing a key role in supporting civilian life and military development. However, the relative motion between satellites and ground receivers causes significant Doppler frequency shifts in the signals. This requires receivers to possess high-dynamic signal acquisition and tracking capabilities, especially in high-speed mobile scenarios.

[0003] Signal capture is the first step in satellite receiver intermediate frequency signal processing, and its accuracy directly affects the synchronous tracking performance of the carrier and pseudo-code phase. Traditional capture methods mainly use serial search, parallel frequency search, or parallel code phase search algorithms. Among them, parallel code phase search uses Fourier transform to perform frequency domain correlation operations, significantly improving capture efficiency, but it still has two inherent drawbacks:

[0004] (1) Limited frequency offset estimation accuracy: Due to the spectral resolution of the discrete Fourier transform, the Doppler frequency offset estimation error is usually positively correlated with the frequency search step size, making it difficult to meet the requirements of high-precision positioning.

[0005] (2) Insufficient anti-interference ability: In a low signal-to-noise ratio environment, a single correlation peak is easily interfered by noise, resulting in false capture, while the existing methods lack an effective verification mechanism.

[0006] Although some improvements attempt to improve accuracy by increasing the search step size or performing multiple averaging, this significantly increases computational complexity, making it difficult to apply under real-time requirements. Therefore, a satellite signal acquisition method that combines high-precision frequency offset estimation with strong noise immunity while ensuring real-time performance is urgently needed. Summary of the Invention

[0007] In view of this, an object of the present invention is to provide a joint navigation satellite signal acquisition method with parallel code phase and orthogonal basis matching.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A method for acquiring a joint navigation satellite signal by matching a parallel code phase with an orthogonal basis comprises the following steps:

[0010] S1: Set the pseudo-random noise sequence number of the target satellite and the corresponding initial code phase offset value, generate a local pseudo-code based on the Gold code generation algorithm, and receive the navigation satellite signal;

[0011] S2: A parallel code phase search algorithm is used to coarsely capture the received signal. Oversampling is used to improve the chip resolution. A dual-peak detection mechanism is used to verify the capture results and obtain preliminary code phase and Doppler frequency offset estimates.

[0012] S3: Determine a fine frequency search range based on the preliminary Doppler frequency offset estimate, and iteratively screen the main frequency component using an orthogonal basis matching method, including:

[0013] generating a plurality of local reference signals within the fine frequency range;

[0014] Calculate the correlation between the signal residual and the local reference signal;

[0015] Select the maximum correlation signal for orthogonalization and update the weight;

[0016] The iteration termination condition is determined by the change of mean square error;

[0017] S4: Extract the frequency with the largest weight and its adjacent frequencies, and obtain the extreme value point as the final Doppler frequency deviation through quadratic function fitting.

[0018] Furthermore, in S2, the parallel code phase search algorithm includes:

[0019] Mix the received signal x(m) with the local carrier and perform Fourier transform to obtain X(k);

[0020] Perform Fourier transform on the local pseudo code c(m+n) and take the conjugate to get C * (k);

[0021] Through frequency domain multiplication operation Z(k)=X(k)·C * (k) Implement time domain correlation operations:

[0022]

[0023] Where N is the number of sampling points, n is the delay, and k is the frequency index.

[0024] Furthermore, in S2, the double peak detection mechanism includes:

[0025] Two independent correlation peak detection operations are performed, and the capture is determined to be valid when the difference in the peak positions of the two detections is less than a preset threshold.

[0026] Furthermore, in S3, the orthogonal basis matching method includes the following iterative process:

[0027] a) k-th residual signal calculation:

[0028]

[0029] Where x is the received signal, w i is the weight coefficient, is the local reference signal;

[0030] b) Orthogonalization processing:

[0031]

[0032] c) Weight update:

[0033]

[0034] Furthermore, the iteration termination condition satisfies any one of the following:

[0035] Mean square error The rate of change of is less than the threshold δ;

[0036] The number of iterations reaches the preset upper limit K max ;

[0037] Where N is the total number of samples and r[k] is the residual of the kth sample.

[0038] Furthermore, the quadratic function fitting in S4 is expressed as:

[0039] y=af 2 +bf+c

[0040] Where f is the frequency variable, a, b, c are fitting coefficients, and the extreme point frequency calculation formula is:

[0041]

[0042] A capture system for performing the method, comprising:

[0043] a signal acquisition module configured to generate a local pseudo-random noise sequence of a target satellite and receive a satellite signal;

[0044] a coarse capture module, whose input end is connected to the output end of the signal acquisition module, configured to execute a parallel code phase search algorithm, and comprising an oversampling unit and a double peak value verification unit;

[0045] a fine capture module, whose input end is connected to the output end of the coarse capture module, configured to implement an orthogonal basis matching algorithm, and comprising an iterative control unit and a weight analysis unit;

[0046] The interpolation module has an input end connected to the output end of the fine capture module and is configured to perform quadratic curve fitting and output a final frequency deviation value.

[0047] Furthermore, the oversampling unit of the coarse capture module is configured to increase the chip resolution of the local pseudo code to 1 / M times the original sampling interval, where M is an integer greater than 1.

[0048] Furthermore, the sperm capture module comprises:

[0049] A basis function memory, used for storing the local reference signal after orthogonalization processing;

[0050] The residual updater is configured according to the formula Update the residual signal.

[0051] A computer storage medium stores a computer program, which implements the method steps when the program is executed by a processor.

[0052] The beneficial effects of the present invention are:

[0053] (1) In the coarse capture stage, oversampling technology is used to improve the chip resolution. The capture results are double-verified in combination with the dual-peak detection mechanism, which effectively identifies the pseudo-correlation peaks caused by noise, significantly enhances the anti-interference capability in low signal-to-noise ratio environments, and provides reliable initial parameters for fine capture.

[0054] (2) In the precision capture stage, the orthogonal basis matching method is innovatively introduced. By iteratively decomposing the signal energy and extracting the main frequency components, the discrete frequency points are optimized at the sub-sampling level by combining quadratic function interpolation. This fundamentally overcomes the defect of traditional methods being limited by spectral resolution and achieves high-precision estimation of Doppler frequency deviation.

[0055] (3) Under the premise of keeping the hardware complexity unchanged, a two-level capture architecture is used to divide the work and cooperate: coarse capture quickly narrows the frequency deviation search range, and fine capture focuses on local fine search, which not only avoids the computational burden of global fine search but also ensures the final output accuracy, achieving the unity of real-time and high precision.

[0056] (4) The method is applicable to various pseudo-random noise sequence signals of the global navigation satellite system. It can still stably output accurate code phase and frequency offset estimation in high dynamic scenarios, providing reliable technical support for civilian high-precision positioning and military anti-interference communications.

[0057] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0059] Figure 1 The flowchart of the joint navigation satellite signal acquisition method based on parallel code phase and orthogonal basis matching is as follows;

[0060] Figure 2 Schematic diagram of the parallel code phase search algorithm used in the coarse acquisition stage; Figure 2 (a) is the schematic diagram of the system in the coarse capture stage; Figure 2 (b) is the coarse capture result diagram at different signal-to-noise ratios;

[0061] Figure 3 Flowchart of the orthogonal basis matching algorithm used in the fine capture stage;

[0062] Figure 4 Schematic diagram of frequency quadratic interpolation analysis based on orthogonal basis matching method;

[0063] Figure 5 The error comparison between the traditional algorithm and the improved algorithm under different signal-to-noise ratios; Figure 5 (a) and Figure 5 (b) Comparison of the capture error performance of different algorithms under two segments of satellite navigation signals. DETAILED DESCRIPTION

[0064] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0065] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0066] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0067] See also Figures 1 to 5 , which is a joint navigation satellite signal acquisition method, system and storage medium with parallel code phase and orthogonal basis matching.

[0068] A method, system and storage medium for capturing joint navigation satellite signals with parallel code phase and orthogonal basis matching, such as Figure 1 As shown, the method includes the following steps:

[0069] Step 1: Generate local pseudo-code signals according to the set satellite parameters and receive GNSS signals sent by the satellite;

[0070] Step 2: In the coarse acquisition phase, a parallel code phase search algorithm is used in combination with oversampling and dual-peak detection to obtain the captured code phase and Doppler frequency offset.

[0071] Step 3: In the fine capture phase, the signal is first analyzed using the orthogonal basis matching method based on the Doppler frequency offset estimate obtained in the coarse capture phase. The three adjacent main frequency components with the largest energy share and their corresponding normalized weight coefficients are extracted.

[0072] Step 4: Based on the three sets of main frequency components and their normalized weights extracted by the orthogonal basis matching method used in the fine acquisition stage, a quadratic function is used to perform curve fitting on the discrete estimation points, and the extreme point of the fitting function is obtained as the final accurate Doppler frequency offset estimate;

[0073] In step 1 of this embodiment, it specifically includes the following process:

[0074] Step 11: Set the pseudo-random noise sequence number of the target satellite and the corresponding initial code phase offset value;

[0075] Step 12: Generate the satellite's local pseudo code according to the set satellite parameters. The core of the algorithm is based on the Gold code generation algorithm and generates a pseudo random noise (PRN) sequence through the product of the shift register.

[0076] In step 2 of this embodiment, the specific process includes:

[0077] Step 21: During the coarse acquisition phase, a parallel code phase search algorithm is used to multiply the received satellite signal with the signal generated by the local carrier oscillator, and then Fourier transform the result. The transformed result is multiplied by the local PRN code after Fourier transform and complex conjugation. The result is then inverse Fourier transformed and modulo squared, and the acquisition result is output. The Fourier transform converts the time domain correlation into a frequency domain multiplication:

[0078]

[0079] Where x(m) represents the received satellite signal, c(m+n) represents the locally generated pseudo code, z(n) represents the correlation result at different delays n, and the peak value corresponds to the capture time. This process can be replaced by frequency domain multiplication:

[0080] Z(k)=X(k)·C * (k)

[0081] Where Z(k), X(k), C * (k) corresponds to the Fourier transform of z(n), the Fourier transform of x(m), and the conjugate result of the Fourier transform of c(m+n).

[0082] Step 22: Oversampling the local pseudo code can improve the chip resolution and enhance the capture accuracy of the code phase.

[0083] Step 23: During the coarse capture process, dual-peak detection is used to verify the accuracy of the coarse capture results through two independent correlation operations. This can avoid the problem of a single correlation peak being accidentally formed by noise interference. This operation can significantly improve signal capture reliability and anti-interference capabilities without increasing hardware complexity.

[0084] In this embodiment, Figure 2 This is a schematic diagram of the parallel code phase search algorithm used in the coarse capture stage. Figure 2 (a) is the schematic diagram of the system in the coarse capture stage. Figure 2 (b) is the coarse capture result diagram at different signal-to-noise ratios.

[0085] In step 3 of this embodiment, the specific process includes:

[0086] Step 31: Based on the results of the rough capture Multiple frequencies are selected for fine search within the range and local reference signals are generated based on these frequencies. d is the coarse capture frequency result, and Δf is the coarse capture frequency resolution.

[0087] Step 32: Calculate the correlation between the current residual and the generated local reference signal. The initial residual here represents the original received satellite signal. The k-th residual is expressed as follows:

[0088]

[0089] where r k represents the kth residual result, x represents the original received satellite signal, ω i represents the weight coefficient of the local reference signal, represents the local reference signal at a specific frequency offset, where the k-th residual represents the remaining signal after removing the first k strongest signal components.

[0090] Step 33: Select the local reference signal with the highest correlation and perform orthogonalization and normalization on the selected signal to eliminate redundancy between the selected signals, and store the orthogonal basis. The orthogonalization process here can be expressed as:

[0091]

[0092] in, represents the orthogonalized local reference signal.

[0093] Step 34: Update the residual and weight values ​​until the signal is fully decomposed, that is, the mean square error no longer decreases or is less than the set threshold. At the same time, the process will be terminated if the number of iterations is exceeded. The update of the residual and weight values ​​can be expressed as:

[0094]

[0095] The mean square error can be expressed as:

[0096]

[0097] Where N represents the total number of samples and r[k] represents the residual of the kth sample.

[0098] In this embodiment, Figure 3 Flowchart of the orthogonal basis matching algorithm used in the fine capture stage;

[0099] In step 4 of this embodiment, the specific process includes:

[0100] Step 41: Filter out the basis function most relevant to the satellite signal and its two adjacent basis functions corresponding to three candidate frequencies from the orthogonal basis, and extract the weight values ​​corresponding to the three basis functions.

[0101] Step 42: Fit a quadratic curve using these three sets of frequencies and weight values:

[0102] y=af 2 +bf+c

[0103] Step 43: Calculate the vertex position of the quadratic curve as the frequency offset estimate:

[0104]

[0105] In this embodiment, Figure 4 Schematic diagram of frequency quadratic interpolation analysis based on orthogonal basis matching method; Figure 5 To compare the errors of the traditional algorithm and the improved algorithm under different signal-to-noise ratios, Figure 5 (a) and Figure 5 (b) Comparison of the capture error performance of different algorithms under two segments of satellite navigation signals.

[0106] This embodiment further proposes a joint navigation satellite signal acquisition system for performing the aforementioned parallel code phase and orthogonal basis matching. The system includes a signal acquisition module, a coarse acquisition module, a fine acquisition module, and an interpolation module, wherein:

[0107] The signal acquisition module first generates a local C / A pseudo-code signal based on the target satellite's PRN number and the Gold code generation algorithm. At the same time, the modulated signal transmitted by the satellite is converted into a digital intermediate frequency signal after down-conversion and ADC sampling, providing input for the subsequent coarse acquisition module.

[0108] The coarse acquisition module uses a parallel code phase search algorithm to perform a cyclic correlation operation between the local pseudo code and the received signal. To improve the accuracy of code phase measurement, the local pseudo code is oversampled to increase the chip resolution, thereby obtaining a more accurate code phase estimate. For frequency offset estimation, an improved dual-peak detection algorithm is used, and the correctness of the coarse acquisition result is verified through two independent correlation operations.

[0109] The fine capture module iteratively screens multiple frequency groups within the fine interval based on the frequency offset range initially determined by the coarse capture. It selects the optimal frequency component by maximizing the complex correlation coefficient between the signal and the basis function, and gradually strips away the captured signal components, ultimately achieving high-precision frequency offset estimation with the goal of minimizing the mean square error.

[0110] The interpolation module uses the three frequencies with the largest weight and the adjacent frequencies and the weights to perform fitting using a quadratic curve, selects the extreme point of the curve as the precisely captured Doppler frequency deviation value, and outputs it.

[0111] In general, in this embodiment, first, a parallel code phase search algorithm is adopted in the coarse capture stage, and the code chip resolution is improved by oversampling the local pseudo-code, thereby improving the code phase estimation accuracy. At the same time, a dual-peak detection mechanism is used to perform secondary verification of the coarsely captured code phase and Doppler frequency offset to eliminate the influence of noise; secondly, in the fine capture stage, based on the coarsely captured frequency offset estimation result, an orthogonal basis matching method is used to perform an iterative search in a finer frequency domain range: the optimal basis function is selected by calculating the signal residual correlation, and the signal is decomposed by the minimum mean square error criterion, and finally the maximum weight and three adjacent frequency components and the corresponding weights are screened out; finally, quadratic function interpolation fitting is performed on the selected three main frequency components, and a high-precision final estimation value of the Doppler frequency offset is obtained by solving the extreme points of the fitting curve.

[0112] The satellite signal is captured by combining two capture stages. Compared with traditional algorithms, the chip resolution and Doppler frequency offset capture accuracy are improved. At the same time, the combination of orthogonal basis matching and quadratic function interpolation effectively overcomes the inherent defect of frequency offset estimation being limited by spectrum resolution.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for acquiring joint navigation satellite signals using parallel code phase and orthogonal basis matching, characterized by: The following steps are involved: S1: Set the pseudo-random noise sequence number of the target satellite and the corresponding initial code phase offset value, generate a local pseudo-code based on the Gold code generation algorithm, and receive the navigation satellite signal; S2: A parallel code phase search algorithm is used to coarsely capture the received signal. Oversampling is used to improve the chip resolution. A dual-peak detection mechanism is used to verify the capture results and obtain preliminary code phase and Doppler frequency offset estimates. S3: Determine a fine frequency search range based on the preliminary Doppler frequency offset estimate, and iteratively screen the main frequency component using an orthogonal basis matching method, including: generating a plurality of local reference signals within the fine frequency range; Calculate the correlation between the signal residual and the local reference signal; Select the maximum correlation signal for orthogonalization and update the weight; The iteration termination condition is determined by the change of mean square error; S4: Extract the frequency with the largest weight and its adjacent frequencies, and obtain the extreme value point as the final Doppler frequency deviation through quadratic function fitting.

2. The method for acquiring joint navigation satellite signals by matching parallel code phase with orthogonal basis according to claim 1, characterized in that: In S2, the parallel code phase search algorithm includes: Mix the received signal x(m) with the local carrier and perform Fourier transform to obtain X(k); Perform Fourier transform on the local pseudo code c(m+n) and take the conjugate to get C * (k); Through frequency domain multiplication operation Z(k)=X(k)·C * (k) Implement time domain correlation operations: Where N is the number of sampling points, n is the delay, and k is the frequency index.

3. The method for acquiring joint navigation satellite signals by matching parallel code phase with orthogonal basis according to claim 1, characterized in that: In S2, the double peak detection mechanism includes: Two independent correlation peak detection operations are performed, and the capture is determined to be valid when the difference in the peak positions of the two detections is less than a preset threshold.

4. The method for acquiring joint navigation satellite signals by matching parallel code phase with orthogonal basis according to claim 1, characterized in that: In S3, the orthogonal basis matching method includes the following iterative process: a) k-th residual signal calculation: Where x is the received signal, w i is the weight coefficient, is the local reference signal; b) Orthogonalization processing: c) Weight update:

5. The method for acquiring joint navigation satellite signals by matching parallel code phase with orthogonal basis according to claim 4, characterized in that: The iteration termination condition satisfies any of the following: Mean square error The rate of change of is less than the threshold δ; The number of iterations reaches the preset upper limit K max ; Where N is the total number of samples and r[k] is the residual of the kth sample.

6. The method for acquiring joint navigation satellite signals by matching parallel code phase with orthogonal basis according to claim 1, characterized in that: The quadratic function fitting in S4 is expressed as: y=of 2 +bf+c Where f is the frequency variable, a, b, c are fitting coefficients, and the extreme point frequency calculation formula is:

7. A capture system for performing the method according to any one of claims 1 to 6, characterized in that: include: a signal acquisition module configured to generate a local pseudo-random noise sequence of a target satellite and receive a satellite signal; a coarse capture module, whose input end is connected to the output end of the signal acquisition module, configured to execute a parallel code phase search algorithm, and comprising an oversampling unit and a double peak value verification unit; a fine capture module, whose input end is connected to the output end of the coarse capture module, configured to implement an orthogonal basis matching algorithm, and comprising an iterative control unit and a weight analysis unit; The interpolation module has an input end connected to the output end of the fine capture module and is configured to perform quadratic curve fitting and output a final frequency deviation value.

8. The capture system according to claim 7, characterized in that: The oversampling unit of the coarse capture module is configured as follows: The chip resolution of the local pseudo code is increased to 1 / M times of the original sampling interval, where M is an integer greater than 1.

9. The capture system according to claim 7, characterized in that: The fine capture module comprises: A basis function memory, used for storing the local reference signal after orthogonalization processing; The residual updater is configured according to the formula Update the residual signal.

10. A computer storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method steps according to any one of claims 1 to 6 are implemented.

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