Navigation signal anti-interference method, system and equipment based on four beams

Abstract

The invention belongs to the field of satellite navigation signal anti-interference, and particularly relates to a navigation signal anti-interference method, system and equipment based on four beams. The objective of the invention is to solve the problems of difficulty in cooperative suppression of composite interference, performance deterioration of interference in a beam pointing range and the like in a traditional anti-interference mode. The method comprises the following steps: selecting four satellites and calculating signal steering vectors; processing array signals in four channels; after characteristic decomposition is carried out on a covariance matrix of each channel, detecting main lobe interference based on characteristic vector correlation; eliminating the main lobe interference by adopting oblique projection preprocessing; and dynamic anti-interference is realized. According to the method, a narrow beam mode, a main beam gain desired signal and adaptive zero setting are adopted to suppress high-power suppressing interference, a side lobe is adopted to suppress multi-source low-power deception interference, eigenvalue oblique projection preprocessing is utilized to cope with the situation of interference in a beam pointing range, composite interference can be cooperatively suppressed, and the method adapts to a complex dynamic environment.

Description

Background Art

[0002] Due to characteristics such as weak signal strength and transparent system, satellite navigation signals are extremely vulnerable to various interferences. The current main interference types include jamming interference and spoofing interference.

[0003] Extensive research has been carried out on anti-jamming methods for jamming, forming a multi-domain fusion technology system such as time domain, frequency domain, space domain, space-time joint processing, and space-frequency joint processing. Among them, the adaptive nulling antenna, as an effective space domain anti-jamming method, has been widely used in military fields such as unmanned aerial vehicles. This method uses an array antenna and generates a beam direction that covers the entire airspace but forms a null in the interference direction through power inversion or its improved algorithm to achieve adaptive suppression of high-power jamming interference. Since it uses a wide beam pattern, the gain in the signal direction is limited.

[0004] Compared with jamming interference, spoofing interference realizes active misleading through information forgery, and the interference power is relatively low. Traditional space domain anti-jamming technologies of the power inversion type cannot effectively suppress it. Currently, spoofing suppression technologies can also use the space domain null control method, but it is necessary to know the direction of arrival of the spoofing interference signal. For a dynamically changing interference environment, it is necessary to re-estimate the interference and adjust the null, which has low applicability to receivers that need to perform spoofing suppression in real time.

[0005] At the same time, it should be noted that when the direction of arrival of the interference signal is close to the satellite direction, that is, when the interference source is within the beam pointing range, there is main lobe interference. Traditional adaptive beamforming algorithms will generate a null within the main lobe, resulting in beam pointing deviation, gain reduction, and even loss of the target signal. At the same time, the sidelobe level increases significantly. At this time, the output signal-to-interference-plus-noise ratio deteriorates, seriously affecting the receiving ability of the receiver and even causing problems such as positioning failure.

[0006] In the modern battlefield electromagnetic environment, jamming and spoofing interferences often act in a composite manner. Traditional space domain anti-jamming technologies have insufficient performance in suppressing low-power spoofing interference, while the spoofing interference space domain processing method is prone to performance degradation in the presence of strong jamming interference. This interference cooperation mechanism poses a severe test to the battlefield applicability of existing single-mode countermeasure technologies. At the same time, due to the existence of main lobe interference, traditional adaptive beamforming technologies will cause the main beam to deform and even weaken the signal reception of the target satellite, further deteriorating the positioning performance. This composite interference mechanism seriously affects the positioning accuracy of existing countermeasure technologies. Therefore, there is an urgent need to develop new composite interference suppression technologies.

[0007] Based on this, the present invention proposes a navigation signal anti-jamming method, system, and device based on four beams. Summary of the Invention

[0008] To solve the above problems in the prior art, namely that traditional airspace anti-jamming technologies are difficult to jointly suppress combined jamming of suppression and deception, and at the same time, the performance deteriorates when encountering interference within the beam pointing range, seriously affecting the receiver's receiving ability and causing problems such as positioning failure, the present invention provides a navigation signal anti-jamming method, system and device based on four beams.

[0009] In the first aspect of the present invention, a navigation signal anti-jamming method based on four beams is proposed. The method includes: Step S1, select four target satellites and perform beamforming, calculate the satellite directions of the four target satellites, and calculate the signal steering vectors of the four target satellites respectively; Step S2, divide the signals received by the N array elements of the array antenna into four independent channels, perform eigenvalue decomposition on the covariance matrix of the signals in each independent channel, and extract the interference signal eigenvectors; Step S3, calculate the correlation between the interference signal eigenvectors and the signal steering vectors, and judge whether there is main lobe interference in each channel based on the correlation. If there is, jump to step S4; otherwise, jump to step S5; Step S4, construct an eigenvalue oblique projection preprocessing matrix to filter out the main lobe interference, solve the covariance matrix of the preprocessed signals and perform diagonal loading processing to eliminate matrix mismatch, calculate the weighted vectors of each independent channel in combination with the signal steering vectors in step S1, and jump to step S6; Step S5, calculate the weighted vectors of each independent channel based on the signal steering vectors in step S1 and the covariance matrix in step S2, and jump to step S6; Step S6, perform weighted processing on the signals of the four independent channels based on the weighted vectors to form four independent narrow beams, respectively align with the four target satellites, obtain the signals output by the four independent channels, and perform acquisition and tracking processing on them respectively; Step S7, judge whether to switch satellites. If so, jump to step S1 and repeat steps S1 to S6 to achieve real-time anti-jamming.

[0010] Further, the satellite direction is calculated as follows: Select four visible satellites with elevation angles higher than a preset angle and evenly distributed azimuth angles as target satellites according to the receiver position information; Calculate the satellite directions of the four target satellites according to the unjammed ephemeris.

[0011] Further, the signal steering vector is calculated based on the spacing between adjacent array elements, the wavelength of the received signal, and the phase difference between the incident signal arriving at each array element and the first array element.

[0012] Further, perform eigenvalue decomposition on the covariance matrix of the signals of each independent channel, extract the eigenvalues and the eigenvectors corresponding to the eigenvalues, sort the eigenvalues from largest to smallest, and based on the characteristic that the interference power is greater than the noise power, select the eigenvectors corresponding to the top Q eigenvalues from the sorted eigenvalues as the eigenvectors of the interference signal, and calculate the correlation based on the Q eigenvectors and the signal steering vector.

[0013] Further, based on the correlation, determine whether there is main lobe interference in each channel. The specific method is as follows: Judge whether the correlation exceeds a set threshold. If it exceeds, output that there is main lobe interference. If it does not exceed, output that there is no main lobe interference and only sidelobe interference exists.

[0014] Further, construct an eigenvalue oblique projection preprocessing matrix to filter out the main lobe interference, and perform covariance matrix solution and diagonal loading processing on the preprocessed signal to eliminate matrix mismatch. The specific method is as follows: Step S41: Based on the channels determined to have main lobe interference in step S3, extract the subspace spanned by the main lobe interference eigenvectors. Step S42: Combine the orthogonal complement space of the subspace spanned by the main lobe interference eigenvectors and the subspace spanned by the sidelobe interference eigenvectors and the target signal steering vector to generate an oblique projection matrix. Step S43: Multiply the oblique projection matrix by the received signal to filter out the main lobe interference component. Step S44: Solve the covariance matrix of the signal after filtering out the main lobe interference component, and perform diagonal loading processing to eliminate the covariance matrix mismatch.

[0015] Further, in step S6, after aligning the main lobes of the narrow beams with four satellites respectively, it further includes: strongly suppressing the existing high-power jamming through adaptive nulling, and suppressing the low-power spoofing jamming through sidelobes.

[0016] Further, the method for judging whether to switch satellites is as follows: Calculate the real-time position and future trajectory of the satellite according to the satellite ephemeris information and the receiver's own position. When it is predicted that the elevation angle of any target satellite is lower than the preset threshold, it is determined that a satellite needs to be switched, and the beam pointing is adjusted to select a new visible satellite.

[0017] In the second aspect of the present invention, a navigation signal anti-jamming system based on four beams is proposed. The system includes: A signal steering vector calculation module, configured to select four target satellites and perform beamforming, calculate the satellite directions of the four target satellites, and calculate the signal steering vectors of the four target satellites respectively. The shunt and feature extraction module is configured to shunt the signals received by N array antenna elements into four independent channels, perform eigenvalue decomposition on the covariance matrix of the signals in each independent channel, and extract the interference signal eigenvectors; The main lobe interference judgment module is configured to calculate the correlation between the interference signal eigenvector and the signal steering vector, and judge whether there is main lobe interference in each channel based on the correlation. If so, it jumps to the interference filtering and weight vector calculation module; otherwise, it jumps to the weight vector calculation module; The interference filtering and weight vector calculation module is configured to construct an eigenvalue oblique projection preprocessing matrix to filter out main lobe interference, perform covariance matrix solution and diagonal loading processing on the preprocessed signals to eliminate matrix mismatch, calculate the weight vector of each independent channel in combination with the signal steering vector in the signal steering vector calculation module, and jump to the weighting and tracking module; The weight vector calculation module is configured to calculate the weight vector of each independent channel based on the signal steering vector in the signal steering vector calculation module and the covariance matrix in the shunt and feature extraction module, and jump to the weighting and tracking module; The weighting and tracking module is configured to perform weighting processing on the signals of the four independent channels based on the weight vector, form four independent narrow beams, respectively align with four target satellites, obtain the signals output by the four independent channels, and perform acquisition and tracking processing on them respectively; The real-time monitoring module is configured to judge whether to switch satellites. If so, it jumps to the signal steering vector calculation module, and repeatedly executes the signal steering vector calculation module to the weighting and tracking module to achieve real-time anti-interference.

[0018] In a third aspect of the present invention, an electronic device is proposed, including: At least one processor; and A memory communicatively connected to at least one of the processors; wherein, The memory stores instructions executable by the processor, and the instructions are used to be executed by the processor to implement the above-mentioned anti-interference method for navigation signals based on four beams.

[0019] Advantages of the present invention: 1. The traditional power inversion type adaptive nulling antenna is mainly used for high-power suppression interference and is not suitable for low-power and highly concealed deception interference. And due to the use of a wide beam mode, the signal direction gain is limited. The present invention uses a narrow beam mode, with the beam concentrated and having a high gain in the desired direction.

[0020] 2. For the spatial null control method adopted for deceptive jamming, the direction of the interfering signal needs to be known. For a dynamically changing interference environment, the interference direction needs to be re-estimated and the null adjusted. In the present invention, the existence of sidelobes can cope with multiple deceptive jammings in all non-desired directions without considering the direction of the desired interference.

[0021] 3. In a complex electromagnetic environment where deceptive jamming and suppression jamming coexist, traditional interference suppression methods cannot suppress both simultaneously. In the present invention, through the combination of four-beam diversity processing and the eigenvalue oblique projection preprocessing matrix, for the interference within the beam pointing range, the main lobe interference is suppressed through eigenvalue oblique projection preprocessing, and the interference within the beam pointing range is accurately suppressed without affecting the reception of the desired signal. For the interference outside the beam pointing range, the present invention strongly suppresses the existing high-power suppression jamming through adaptive nulling, and at the same time, the low-power deceptive jamming can also be well suppressed through the sidelobes, thereby effectively suppressing various types of interference in non-desired directions, solving the performance limitations of traditional single anti-jamming technologies in complex jamming scenarios, significantly improving the overall suppression efficiency of coordinated jamming, and being more practical in actual scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objectives, and advantages of the present application will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings: Figure 1 is a flowchart of a navigation signal anti-jamming method based on four beams according to the present invention; Figure 2 is a schematic diagram of the formation principle of four beams of a navigation signal anti-jamming method based on four beams according to the present invention; Figure 3 is the beam pattern of the anti-jamming antenna of the power inversion type in the present invention; Figure 4 is the beam pattern of the anti-jamming antenna of the adaptive beam forming type in the present invention; Figure 5 is the beam pattern formed by a channel aligning with one of the satellites in a navigation signal anti-jamming method based on four beams according to the present invention when interference exists. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention and are not intended to limit the invention. Additionally, it should be noted that for the sake of description, only the parts related to the relevant invention are shown in the drawings.

[0024] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] In the first embodiment of the present invention, a navigation signal anti-interference method based on four beams is provided, and the method includes: Step S1, select four target satellites and perform beamforming, calculate the satellite directions of the four target satellites, and calculate the signal steering vectors of the four target satellites respectively; Step S2, divide the signals received by the N array elements of the array antenna into four independent channels, perform eigenvalue decomposition on the covariance matrix of the signals in each independent channel, and extract the interference signal eigenvectors; Step S3, calculate the correlation between the interference signal eigenvectors and the signal steering vectors, and judge whether there is main lobe interference in each channel based on the correlation. If so, jump to step S4, otherwise jump to step S5; Step S4, construct an eigenvalue oblique projection preprocessing matrix to filter out the main lobe interference, solve the covariance matrix of the preprocessed signals and perform diagonal loading processing to eliminate matrix mismatch, calculate the weighting vectors of each independent channel in combination with the signal steering vectors in step S1, and jump to step S6; Step S5, calculate the weighting vectors of each independent channel based on the signal steering vectors in step S1 and the covariance matrix in step S2, and jump to step S6; Step S6, perform weighting processing on the signals in the four independent channels based on the weighting vectors to form four independent narrow beams, respectively align them with the four target satellites, obtain the signals output from the four independent channels, and perform acquisition and tracking processing on them respectively; Step S7, judge whether to switch satellites. If so, jump to step S1, and repeat steps S1 to S6 to achieve real-time anti-interference.

[0026] Based on an antenna array and beamforming algorithms, through precise beam control technology, the present invention enables four narrow-beam main lobes to be respectively aligned with four different satellites, which is equivalent to establishing four relatively independent receiving links. Since the formed beams are very narrow, a natural filtering mechanism is formed in space. For the narrow beams aligned with the satellites, there is a high gain in the desired satellite communication direction. When the interference source is outside the beam pointing range, high-power suppression interference is strongly suppressed through adaptive nulling. At the same time, low-power spoofing interference can also be well suppressed through the side lobes, thus effectively suppressing various types of interference in the non-desired directions. When the direction of the interference signal approaches the satellite direction, at this time, the interference source is within the beam pointing range and there is main lobe interference. The main lobe interference is filtered out by constructing an eigenvalue oblique projection preprocessing matrix, thus effectively suppressing the main lobe interference and the impact on the target satellite signal.

[0027] The four-beam design of the present invention is already the minimum requirement for the navigation system to accurately locate. If the main lobe directions of multiple satellites are all interfered, the receiver may not be able to obtain enough effective satellites, resulting in positioning interruption. To ensure the effective performance of the receiver, it is therefore very necessary for the present invention to study anti-main lobe interference.

[0028] To more clearly illustrate a navigation signal anti-interference method based on four beams of the present invention, the following will combine Figures 1-5 to detail each step in the embodiments of the present invention.

[0029] A navigation signal anti-interference method based on four beams in the first embodiment of the present invention includes steps S1 - S6, and each step is described in detail as follows: Step S1, select four target satellites and perform beamforming, calculate the satellite directions of the four target satellites, and respectively calculate the signal steering vectors of the four target satellites; In this embodiment, four visible satellites with an elevation angle higher than a preset angle and evenly distributed azimuth angles are selected as target satellites according to the receiver position information; Calculate the satellite directions of the four target satellites according to the uneffected ephemeris , , represents the number of satellites. The four-beam design is directly related to the minimum positioning requirement of the navigation system. Selecting four visible satellites not only ensures that the receiver can still maintain the basic positioning ability in an interference environment, but also reduces the risk of multipath interference and signal conflict. At the same time, it simplifies the complexity of beam management and avoids the waste of hardware resources and the sharp increase in algorithm calculation amount caused by too many beams.

[0030] In this embodiment, the real-time azimuth and elevation of the satellite are calculated using a satellite orbit model (such as the Kepler equation) based on the orbital parameters in the ephemeris (such as the satellite orbit inclination, the right ascension of the ascending node, the average angular velocity, etc.) and the geographic location and timestamp of the receiver.

[0031] The satellite's direction vector in space is determined using a coordinate transformation (e.g., geocentric to receiver local coordinates).

[0032] In this embodiment, the signal steering vector is calculated based on the spacing between adjacent array elements, the wavelength of the received signal, and the phase difference between the incident signal reaching each array element and the first array element. Specifically: Calculate the satellite signal steering vector based on the satellite direction For an antenna array with a certain array element distribution, the position of reference array element 1 is taken as the origin, and the position coordinates of the nth array element are , , when the antenna array receives the incoming When the satellite signal is received, the steering vector of the formed beam aimed at the target satellite is: ; in, is the path difference between the nth array element and the reference array element receiving signal, and its analytical expression is: ; Where c is the speed of light, is the signal center frequency.

[0033] See also Figure 2 , step S2, dividing the signals received by the N array elements of the array antenna into four independent channels, performing eigendecomposition on the covariance matrix of the signal of each independent channel, and extracting the interference signal eigenvector; In this embodiment, the signal after branching is expressed as: ,in To receive a signal in the Mth channel, The signal received by the nth array element in each channel is expressed as: . Wherein, the nth array element receives the signal in the Mth channel.

[0034] Step S2, dividing the signals received by the N array elements of the array antenna into four independent channels, performing eigendecomposition on the covariance matrix of the signal of each independent channel, and extracting the interference signal eigenvector; Solve the sampling covariance matrix of the four received signals when the number of snapshots is K respectively . Then perform eigendecomposition on the covariance matrix of the four received signals: .in, and respectively represent the th eigenvalue and eigenvector of the received signal sampling covariance matrix in each channel, are N eigenvalues arranged in descending order, are the eigenvectors corresponding to the eigenvalues.

[0035] In this embodiment, for the covariance matrix of the signal of each independent channel, eigenvalue decomposition is performed to extract the eigenvalues and the eigenvectors corresponding to the eigenvalues. The eigenvalues are sorted from large to small. Based on the characteristic that the interference power is greater than the noise power, the eigenvectors corresponding to the first Q eigenvalues are selected from the sorted eigenvalues as the eigenvectors of the interference signal, and the correlation is calculated based on the Q eigenvectors and the signal steering vector. Specifically: Since the interference power is greater than the noise power, the diagonal matrix composed of Q large eigenvalues represents the eigenvalue matrix of the interference signal, and the corresponding is the subspace spanned by the interference signal. The remaining eigenvalues form the eigenvalue matrix of the noise, and the corresponding noise subspace is:

[0036] wherein, Q in this embodiment is estimated based on the AIC criterion. Specifically: Construct the AIC curve: , where is the parameter vector containing the interference characteristic information, is the possible number of interferences. The first term in the formula represents the deviation between the established model and the true distribution, and the second term is the penalty function added to prevent overestimation. The smaller the AIC value, the higher the fitting degree of the model. Therefore, in the formula is range for optimization. The value when the formula value is the smallest is the estimate of the number of large eigenvalues: .

[0037] Step S3, calculate the correlation between the eigenvector of the interference signal and the signal steering vector, and based on the correlation, determine whether there is main lobe interference in each channel. If there is, jump to step S4; otherwise, jump to step S5; In this embodiment, based on the correlation, determine whether there is main lobe interference in each channel. The method is specifically as follows: Judge whether the correlation exceeds the set threshold. If it exceeds, output that there is main lobe interference. If it does not exceed, output that there is no main lobe interference and only sidelobe interference exists.

[0038] The correlation , and its calculation method is: . Since the main lobe interference is closest to the direction of the target satellite , the correlation between the eigenvector of the main lobe interference and the steering vector of the target satellite is extremely strong. In the formula represents the second norm of the correlation vector.

[0039] Judgment is performed on each channel respectively. The correlation operation is carried out between the eigenvectors corresponding to the Q largest eigenvalues obtained in step S2 and the steering vector of the target satellite obtained in step S1. If the correlation value between them is higher than the set threshold (the threshold is set at 0.9), it indicates that there is main lobe interference in this channel, and the eigenvector at this time is the eigenvector of the main lobe interference , if it is lower than the set threshold, it indicates that there is only sidelobe interference in this channel.

[0040] Step S4, construct an eigenvalue oblique projection preprocessing matrix to filter out the main lobe interference, solve the covariance matrix for the preprocessed signal and perform diagonal loading processing to eliminate matrix mismatch, calculate the weighted vector of each independent channel in combination with the signal steering vector in step S1, and jump to step S6; In this embodiment, an eigenvalue oblique projection preprocessing matrix is constructed to filter out the main lobe interference, and the covariance matrix is solved for the preprocessed signal and diagonal loading processing is performed to eliminate matrix mismatch. The specific method is as follows: Step S41, based on the channels determined to have main lobe interference in step S3, extract the subspace spanned by the main lobe interference eigenvectors , where , P represents the number of main lobe interferences.

[0041] Step S42, generate an oblique projection matrix by combining the orthogonal complement space of the subspace spanned by the main lobe interference eigenvectors and the subspace jointly spanned by the sidelobe interference eigenvectors and the target signal steering vector; The subspace jointly spanned by the sidelobe interference eigenvectors and the target signal steering vector is ; Among them, represents the subspace spanned by the sidelobe interference, and the oblique projection matrix is generated; Among them, the orthogonal complement space of the main lobe interference subspace can be expressed as: , H is the conjugate transpose.

[0042] The oblique projection matrix .

[0043] Since the calculation process of constructing the above-mentioned eigenvalue oblique projection preprocessing matrix depends on operations such as matrix inversion, the computational complexity is relatively high. Therefore, an iterative algorithm is used to gradually approximate the exact solution, which can reduce the computational complexity of the oblique projection operator, improve the running speed of the algorithm, and make it more suitable for systems with high real-time requirements.

[0044] Among them, the exact value of the inverse matrix to be sought can also be gradually approximated through the introduction of over-relaxation iteration, so as to calculate the oblique projection matrix more efficiently. Specifically: The over-relaxation iteration method is used to solve the linear equations , and its iteration formula is . Among them, , D is a diagonal matrix composed of the diagonal elements of A; L is the matrix obtained by taking the negative of the strictly lower triangular part of A; U is the matrix obtained by taking the negative of the strictly upper triangular part of A; is the relaxation factor.

[0045] Suppose , , and regard it as the coefficient matrix in the over-relaxation iteration method , , for , , perform decomposition, that is , , solving the inverse matrix is equivalent to solving the linear equations , then The iterative calculation of can be expressed as: , where is The approximate value of the k -th iteration, I is the identity matrix. The iterative calculation of is obtained in the same way.

[0046] Step S43, multiply the oblique projection matrix by the received signal to filter out the main lobe interference component: , where is the signal after filtering out the main lobe interference component.

[0047] Step S44, solve the covariance matrix of the signal after filtering out the main lobe interference component, and perform diagonal loading processing to eliminate the covariance matrix mismatch: Solve the sampling covariance matrix of the signal after oblique projection preprocessing in the channels with main lobe interference again: , and then perform diagonal loading processing on the preprocessed covariance matrix to eliminate the covariance matrix mismatch: , is the loading amount of the diagonal loading processing, is the identity matrix.

[0048] Design the weighted vectors for each beamforming path as: , and design four different weighted vectors for the four channels respectively .

[0049] Step S5, calculate the weighted vector of each independent channel based on the signal steering vector in step S1 and the covariance matrix in step S2, and jump to step S6; Using the steering vector obtained in step S1, design the weighted vectors for each beamforming path: ; where represents the correlation matrix 's inverse matrix. Design four different weights for the four channels respectively . The weight coefficient set for the nth array element in each channel is expressed as: . Where is the weight coefficient set for the nth array element in the Mth channel.

[0050] See Figure 2 , step S6, perform weighted processing on the signals of the four independent channels based on the weighted vectors to form four independent narrow beams, respectively align them with the four target satellites, obtain the signals output by the four independent channels, and perform acquisition and tracking processing on them respectively; after aligning the main lobes of the narrow beams with the four satellites respectively, it further includes: strongly suppressing the existing high-power jammer through adaptive nulling, and suppressing the low-power deception jammer through sidelobe suppression.

[0051] Perform weighted processing on the received signals after splitting in step S2 respectively, and the processed signals of each path are expressed as: .

[0052] For the narrow beam mentioned in the present invention, it is in contrast to the wide beam generated by the traditional power inversion type adaptive nulling antenna. This beam usually does not have a clear main lobe, and the energy may be scattered in multiple directions, showing the characteristics of a wide beam as a whole. Therefore, compared with the wide beam formed in this way, the beam generated by the present invention can be regarded as a narrow beam. Taking a uniform linear array as an example, the number of array elements is N, the array element spacing is d, and the desired signal direction is , the half-power main beam width is expressed as: , and the maximum sidelobe gain of the uniform linear array is lower than -13 dB. At this time, the half-power main beam width of the beam is less than or equal to , and when the maximum sidelobe gain of the uniform linear array is not higher than -13 dB, it can be defined as a narrow beam.

[0053] Step S7: Determine whether to switch satellites. If so, jump to step S1 and repeat steps S1 to S6 to achieve real-time anti-interference.

[0054] In this embodiment, the method for determining whether to switch satellites is as follows: Calculate the real-time position and future trajectory of the satellite based on the satellite ephemeris information and the receiver's own position; When it is predicted that the elevation angle of any target satellite is lower than the preset threshold, it is determined that a satellite switch is required, and the beam pointing is adjusted to select a new visible satellite.

[0055] Since the satellite direction is constantly changing, based on the satellite ephemeris information and the receiver's own position, calculate the real-time position and future trajectory of the satellite, predict when the elevation angle of the satellite will be lower than the preset threshold, and thus determine whether the satellite is passing by. If so, a satellite switch is required and the beam pointing is adjusted.

[0056] As Figures 3-5 shown, Figure 3 Realize the adaptive suppression of high-power jamming. Since it uses a wide-beam pattern, the gain for the signal direction is limited. Figure 4 When there is main-lobe interference, the traditional adaptive beamforming algorithm will generate nulls in the main lobe, resulting in beam pointing deviation, gain reduction, and even loss of the target signal. At the same time, the sidelobe level increases significantly, and the output signal-to-interference-plus-noise ratio deteriorates, seriously affecting the receiver's receiving ability and even causing problems such as positioning failure.

[0057] Compared with Figure 3 and Figure 4 compared, Figure 5 is the beam pattern formed by a channel aligning with one satellite in an anti-jamming method for navigation signals based on four beams of the present invention. It can be seen from Figure 5 that this method can generate deep nulls in the interference direction while keeping the main lobe aligned with the desired signal direction. Compared with the traditional adaptive beamforming algorithm in Figure 4 , it avoids the problems of main beam deviation, gain reduction, and sidelobe level increase caused by the existence of main-lobe interference, and the deterioration of the output signal-to-interference-plus-noise ratio, ensuring the efficient reception of the target signal. The four-beam design realizes high-gain directional reception through multi-beam joint optimization, has a wider spatial coverage range, can dynamically adapt to complex electromagnetic environments, and is especially suitable for the collaborative suppression of multiple interference sources in multi-satellite navigation scenarios.

[0058] In the above embodiments, although the various steps are described in the above order, those skilled in the art can understand that in order to achieve the effects of this embodiment, different steps do not have to be executed in such an order. They can be executed simultaneously (in parallel) or in reverse order, and these simple changes are all within the protection scope of the present invention.

[0059] In the second embodiment of the present invention, a navigation signal anti-interference system based on four beams is proposed, based on a navigation signal anti-interference method based on four beams. The system includes: A signal steering vector calculation module configured to select four target satellites and perform beamforming, calculate the satellite directions of the four target satellites, and calculate the signal steering vectors of the four target satellites respectively; A splitting and feature extraction module configured to split the signals received by the N array elements of the array antenna into four independent channels, perform eigenvalue decomposition on the covariance matrix of the signals of each independent channel, and extract the interference signal eigenvectors; A main lobe interference judgment module configured to calculate the correlation between the interference signal eigenvectors and the signal steering vectors, and judge whether there is main lobe interference in each channel based on the correlation. If there is, it jumps to the interference filtering and weight vector calculation module; otherwise, it jumps to the weight vector calculation module; An interference filtering and weight vector calculation module configured to construct an eigenvalue oblique projection preprocessing matrix to filter out main lobe interference, perform covariance matrix solution and diagonal loading processing on the preprocessed signals to eliminate matrix mismatch, calculate the weight vectors of each independent channel in combination with the signal steering vectors in the signal steering vector calculation module, and jump to the weighting and tracking module; A weight vector calculation module configured to calculate the weight vectors of each independent channel based on the signal steering vectors in the signal steering vector calculation module and the covariance matrix in the splitting and feature extraction module, and jump to the weighting and tracking module; A weighting and tracking module configured to perform weighting processing on the signals of the four independent channels based on the weight vectors, form four independent narrow beams, respectively align with the four target satellites, obtain the signals output by the four independent channels, and perform acquisition and tracking processing on them respectively; A real-time monitoring module configured to judge whether to switch satellites. If so, it jumps to the signal steering vector calculation module, and repeatedly executes the signal steering vector calculation module to the weighting and tracking module to achieve real-time anti-interference.

[0060] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working process and related descriptions of the above-described system can refer to the corresponding process in the foregoing method embodiment, and will not be repeated here.

[0061] It should be noted that the anti-jamming system for navigation signals based on four beams provided in the above embodiments is only illustrated by dividing the above-mentioned functional modules. In practical applications, the above functions can be assigned to different functional modules according to needs, that is, the modules or steps in the embodiments of the present invention can be further decomposed or combined. For example, the modules in the above embodiments can be combined into one module, or further split into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only used to distinguish each module or step, and are not regarded as an improper limitation of the present invention.

[0062] An electronic device according to a third embodiment of the present invention includes: At least one processor; and A memory communicatively connected to at least one of the processors; wherein, The memory stores instructions executable by the processor, and the instructions are used to be executed by the processor to implement the above-mentioned anti-jamming method for navigation signals based on four beams.

[0063] A computer-readable storage medium according to a fourth embodiment of the present invention stores computer instructions, and the computer instructions are used to be executed by the computer to implement the above-mentioned anti-jamming method for navigation signals based on four beams.

[0064] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes and related descriptions of the above-mentioned storage device and processing device can refer to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0065] Those skilled in the art should be able to realize that the modules and method steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. The programs corresponding to the software modules and method steps can be placed in a random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. To clearly illustrate the interchangeability of electronic hardware and software, the components and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in the form of electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0066] The terms "first", "second", etc. are used to distinguish similar objects and are not intended to describe or indicate a particular order or sequence.

[0067] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to those process, method, article, or apparatus / device.

[0068] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A navigation signal anti-interference method based on four beams, characterized in that The method includes: Step S1, select four target satellites and perform beamforming, calculate the satellite directions of the four target satellites, and calculate the signal steering vectors of the four target satellites respectively; Step S2, split the signals received by the N array elements of the array antenna into four independent channels, perform eigenvalue decomposition on the covariance matrix of the signals in each independent channel, and extract the interference signal eigenvectors; Step S3, calculate the correlation between the interference signal eigenvectors and the signal steering vectors, and based on the correlation, determine whether there is main lobe interference in each channel. If there is, jump to Step S4, otherwise jump to Step S5; Step S4, construct an eigenvalue oblique projection preprocessing matrix to filter out the main lobe interference, solve the covariance matrix for the preprocessed signals and perform diagonal loading processing to eliminate matrix mismatch, calculate the weighted vectors for each independent channel in combination with the signal steering vectors in Step S1, and jump to Step S6; Step S5, calculate the weighted vectors for each independent channel based on the signal steering vectors in Step S1 and the covariance matrix in Step S2, and jump to Step S6; Step S6, perform weighted processing on the signals in the four independent channels based on the weighted vectors to form four independent narrow beams, respectively align them with the four target satellites, obtain the signals output from the four independent channels, and perform acquisition and tracking processing on them respectively; Step S7, determine whether to switch satellites. If so, jump to Step S1, and repeat Steps S1 to S6 to achieve real-time anti-interference.

2. The anti-jamming method for navigation signals based on four beams according to claim 1, characterized in that, The satellite direction, its calculation method is: Select four visible satellites with elevation angles higher than a preset angle and evenly distributed azimuth angles as target satellites according to the receiver position information; Calculate the satellite directions of the four target satellites according to the unperturbed ephemeris.

3. A navigation signal anti-interference method based on four beams according to claim 1, characterized in that The signal steering vector is calculated based on the spacing between adjacent array elements, the wavelength of the received signal, and the phase difference between the incident signal arriving at each array element and the first array element.

4. A navigation signal anti-interference method based on four beams according to claim 1, characterized in that, Perform eigenvalue decomposition on the covariance matrix of the signals in each independent channel, extract the eigenvalues and the eigenvectors corresponding to the eigenvalues, sort the eigenvalues from largest to smallest, and based on the characteristic that the interference power is greater than the noise power, select the eigenvectors corresponding to the first Q eigenvalues from the sorted eigenvalues as the interference signal eigenvectors, and calculate the correlation based on the Q eigenvectors and the signal steering vectors.

5. A navigation signal anti-interference method based on four beams according to claim 4, characterized in that Based on the correlation, determine whether there is main lobe interference in each channel. The specific method is: Judge whether the correlation exceeds a set threshold. If it exceeds, output that there is main lobe interference. If it does not exceed, output that there is no main lobe interference and only sidelobe interference exists.

6. A navigation signal anti-interference method based on four beams according to claim 1, characterized in that, Construct an eigenvalue oblique projection preprocessing matrix to filter out the main lobe interference, and perform covariance matrix solution and diagonal loading processing on the preprocessed signals to eliminate matrix mismatch. The specific method is: Step S41, based on the channel determined to have main lobe interference in Step S3, extract the subspace spanned by the main lobe interference eigenvectors; Step S42, combine the orthogonal complement space of the subspace spanned by the main lobe interference eigenvectors and the subspace spanned by the sidelobe interference eigenvectors and the target signal steering vector to generate an oblique projection matrix; Step S43: Multiply the oblique projection matrix with the received signal to filter out the main lobe interference component; Step S44: Solve the covariance matrix of the signal after filtering out the main lobe interference component, and perform diagonal loading processing to eliminate the covariance matrix mismatch.

7. A navigation signal anti-interference method based on four beams according to claim 1, characterized in that, In step S6, after aligning the main lobes of the narrow beams with four satellites respectively, it further includes: strongly suppressing the existing high-power jamming by adaptive nulling, and suppressing the low-power spoofing jamming through sidelobe suppression.

8. A navigation signal anti-interference method based on four beams according to claim 1, characterized in that, Judge whether to switch satellites, and the method is as follows: Calculate the real-time position and future trajectory of the satellite according to the satellite ephemeris information and the position of the receiver itself; When it is predicted that the elevation angle of any target satellite is lower than the preset threshold, it is determined that the satellite needs to be switched, and the beam pointing is adjusted to select a new visible satellite.

9. A navigation signal anti-jamming system based on four beams, based on the navigation signal anti-jamming method based on four beams according to any one of claims 1-8, characterized in that, The system includes: A signal steering vector calculation module, configured to select four target satellites and perform beamforming, calculate the satellite directions of the four target satellites, and calculate the signal steering vectors of the four target satellites respectively; A splitting and feature extraction module, configured to split the signals received by the N array elements of the array antenna into four independent channels, perform eigenvalue decomposition on the covariance matrix of the signals of each independent channel, and extract the interference signal eigenvectors; A main lobe interference judgment module, configured to calculate the correlation between the interference signal eigenvectors and the signal steering vectors, and judge whether there is main lobe interference in each channel based on the correlation. If there is, jump to the interference filtering and weighted vector calculation module, otherwise jump to the weighted vector calculation module; An interference filtering and weighted vector calculation module, configured to construct an eigenvalue oblique projection preprocessing matrix to filter out the main lobe interference, solve the covariance matrix of the preprocessed signal and perform diagonal loading processing to eliminate the matrix mismatch, calculate the weighted vectors of each independent channel in combination with the signal steering vectors in the signal steering vector calculation module, and jump to the weighting and tracking module; A weighted vector calculation module, configured to calculate the weighted vectors of each independent channel based on the signal steering vectors in the signal steering vector calculation module and the covariance matrix in the splitting and feature extraction module, and jump to the weighting and tracking module; A weighting and tracking module, configured to perform weighting processing on the signals of the four independent channels based on the weighted vectors to form four independent narrow beams, respectively align them with the four target satellites, obtain the signals output by the four independent channels, and perform acquisition and tracking processing on them respectively; A real-time monitoring module, configured to judge whether to switch satellites. If so, jump to the signal steering vector calculation module, and repeat the execution of the signal steering vector calculation module to the weighting and tracking module to achieve real-time anti-jamming.

10. An electronic device, characterized in that, It includes: At least one processor; And A memory communicatively connected to at least one of the processors; wherein, The memory stores instructions executable by the processor, and the instructions are used to be executed by the processor to implement a navigation signal anti-jamming method according to any one of claims 1-8.

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