High-resolution spatial spectrum direction finding method and system based on aperture dynamic adjustment

Abstract

The invention provides a high-resolution spatial spectrum direction finding method and system based on aperture dynamic adjustment, and belongs to the technical field of communication. According to the method, the aperture is dynamically adjusted, the direction finding result under the aperture is calculated, whether the direction finding result is valid or not is judged according to a certain criterion, if the direction finding result is valid, aperture adjustment is stopped, the direction finding result is returned, and if the direction finding result is invalid, aperture adjustment is continued until the upper limit of aperture adjustment is reached. And if no effective direction finding result exists when the upper limit is reached, returning the direction finding result of the initial aperture. According to the invention, the technical problem of insufficient direction finding resolution caused by small array aperture corresponding to the signal frequency is solved.

Description

Technical Field

[0001] The invention belongs to the field of communications, and in particular relates to a high-resolution spatial spectrum direction finding method and system based on dynamic aperture adjustment. Background Art

[0002] The core of spatial source positioning is DOA (direction-of-arrival) estimation technology, which is an important research topic in array signal processing. Among the many DOA estimation methods, the MUSIC algorithm uses the orthogonality of the signal subspace and the noise subspace to construct a spatial spectrum function and estimates the DOA of the signal by searching for the spectrum peak. The MUSIC algorithm can theoretically achieve arbitrarily high resolution under the premise of an accurate signal model. However, in practical applications, when the signal sources are closely spaced, the estimation performance of the MUSIC algorithm gradually deteriorates or even fails completely. Existing research results show that the resolution of signal DOA estimation depends on the aperture size of the array. Therefore, increasing the array aperture is one of the methods to improve the estimation resolution, but it is impractical to significantly increase the physical size of the array in a real environment. Due to the weight limit of the launch platform and the need to perform direction finding over a wide frequency band, it is impossible to make too many layers of antennas, which makes the frequency mismatch with the array aperture, resulting in the inability to distinguish closely spaced signals.

[0003] Traditional methods based on virtual array expansion or translation can increase the virtual aperture of the array, thereby improving the direction-finding resolution of the array; however, this series of methods requires reconstructing the data of the newly added array elements, then solving the covariance matrix and then using the MUSIC algorithm to find the direction. Multiple covariance solutions and spectrum peak searches will increase the amount of calculation and reduce the real-time performance of the system. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a high-resolution spatial spectrum direction finding method and system based on dynamic aperture adjustment, which solves the technical problem of insufficient direction finding resolution caused by a small array aperture corresponding to the signal frequency, and effectively and quickly improves the direction finding resolution when the frequency and aperture do not match.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is: a high-resolution spatial spectrum direction finding method based on dynamic aperture adjustment, comprising the following steps: S1. According to the actual aperture of the antenna array, use the MUSIC algorithm to perform direction finding and obtain the initial angle; S2, calculating the optimal circular array aperture corresponding to the frequency information; S3, setting the adjustment range of the dynamic aperture, traversing from the actual aperture of the antenna array to the optimal circular array aperture; S4, traversing the dynamic aperture, using the MUSIC algorithm to perform direction finding within a preset range at the initial angle position, and calculating the width of each angle spectrum peak; S5. Determine whether the width of the spectrum peak is less than a preset threshold. If so, end the traversal and output the final high-resolution spatial spectrum direction finding result. Otherwise, return to S3.

[0006] The beneficial effects of the present invention are as follows: by setting a dynamic aperture, the present invention can improve the resolution of signals with close spatial intervals when the frequency does not match the array aperture, thereby increasing the applicable range of the frequency band under the aperture-invariant array, and the present invention has a small amount of calculation and is easy to implement.

[0007] Furthermore, the S1 is specifically: Based on the received data of the antenna real aperture array, the covariance matrix is ​​calculated ; Covariance matrix Perform eigenvalue decomposition to determine the noise subspace ; Based on the determined noise subspace , combine the information parameter range to perform spectrum peak search; Based on the spectrum peak search results, find out the angle corresponding to the maximum point, which is the initial angle obtained by direction finding.

[0008] Furthermore, the covariance matrix The maximum likelihood expression of is as follows:

[0009]

[0010] in, Represents the data collected by each antenna array element, , Indicates Antenna array elements, represents the number of antenna array elements, express Conjugate transpose, Indicates the number of sampling snapshots, Represents a matrix.

[0011] Furthermore, the expression for performing the spectrum peak search is as follows:

[0012]

[0013] in, represents the calculated spectrum peak result, represents the steering vector of the antenna array, express The conjugate transpose of represents the noise subspace, express The conjugate transpose of Indicates the angle of traversal search, represents the optimal incident angle, and argmin represents a mathematical minimum optimization solution.

[0014] Furthermore, the expression of the optimal circular array aperture is as follows:

[0015] in, represents the optimal circular array aperture, represents the signal wavelength, Represents the number of elements in the uniform circular array.

[0016] The present invention provides a high-resolution spatial spectrum direction finding system based on dynamic aperture adjustment, wherein the high-resolution spatial spectrum direction finding system is used to perform a high-resolution spatial spectrum direction finding method, including: The first processing module is used to perform direction finding using a MUSIC algorithm according to the actual aperture of the antenna array to obtain an initial angle; The second processing module is used to calculate the optimal circular array aperture corresponding to the frequency information; The third processing module is used to set the adjustment range of the dynamic aperture, traversing from the actual aperture of the antenna array to the optimal circular array aperture; The fourth processing module is used to traverse the dynamic aperture, use the MUSIC algorithm to perform direction finding within a preset range at the position of the initial angle, and calculate the width of each angle spectrum peak; The fifth processing module is used to determine whether the width of the spectrum peak is less than a preset threshold. If so, the traversal is terminated and the final high-resolution spatial spectrum direction finding result is output; otherwise, the third processing module is returned to be executed.

[0017] The beneficial effects of the present invention are as follows: by setting a dynamic aperture, the present invention can improve the resolution of signals with close spatial intervals when the frequency does not match the array aperture, thereby increasing the applicable range of the frequency band under the aperture-invariant array, and the present invention has a small amount of calculation and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a flow chart of the method.

[0019] Figure 2 This is a schematic diagram of the result without dynamic aperture adjustment.

[0020] Figure 3Schematic diagram of the results of dynamic aperture adjustment.

[0021] Figure 4 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0022] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0023] Example 1 Before describing the present invention, the following terms are explained: The MUSIC algorithm is a method based on matrix eigenspace decomposition.

[0024] like Figure 1 As shown, the present invention provides a high-resolution spatial spectrum direction finding method based on dynamic aperture adjustment, and its implementation method is as follows: S1. According to the actual aperture of the antenna array, use the MUSIC algorithm to find the direction and obtain the initial angle. The implementation method is as follows: Based on the received data of the antenna real aperture array, the covariance matrix is ​​calculated ; Covariance matrix Perform eigenvalue decomposition to determine the noise subspace ; Based on the determined noise subspace , combine the information parameter range to perform spectrum peak search; Based on the spectrum peak search results, find out the angle corresponding to the maximum point, which is the initial angle obtained by direction finding.

[0025] In this embodiment, the covariance matrix of the received data is calculated: (1) in, represents the covariance matrix, represents a mathematical operation to find expectation. , represents the matrix, Each element in the matrix is , Represents the data collected by each antenna array element, , Indicates Antenna array elements, represents the number of antenna array elements, express The conjugate transpose of represents the steering vector matrix, Representation Matrix A Each element in (each element is a ), represents the steering vector, represents the number of real signals, express The conjugate transpose of , represents the matrix, Representation Matrix Middle Signal, matrix Each element in it is the data of the signal, and there are a total of A signal; represents noise, express The conjugate transpose of express The power, represents the identity matrix, represents the covariance matrix of the signal.

[0026] Then the covariance matrix R Perform eigenvalue decomposition: (2) in, It represents the subspace formed by the eigenvectors corresponding to the large eigenvalues, that is, the signal subspace. represents the signal characteristic value, represents the subspace spanned by the eigenvectors corresponding to small eigenvalues, i.e., the noise subspace. represents the noise characteristic value, express The conjugate transpose of express The conjugate transpose of .

[0027] Under ideal conditions, the signal subspace and the noise subspace in the data space are orthogonal to each other, that is, the steering vector in the signal subspace is also orthogonal to the noise subspace: (3) in, represents the steering vector of the antenna array, express The conjugate transpose of represents the noise subspace, Indicates the angle of the traversal search.

[0028] The classic MUSIC algorithm is proposed based on the above property, but considering that the actual received data matrix is ​​finite in length, that is, the covariance matrix The maximum likelihood estimate of is: (4) in, , Represents the data collected by each antenna array element, , Indicates Antenna array elements, represents the number of antenna array elements, express Conjugate transpose, Indicates the number of sampling snapshots, Represents a matrix, where each element is , Represents the data collected by each antenna array element.

[0029] Covariance matrix The noise subspace can be calculated by eigendecomposition Due to the presence of noise, With the noise subspace They are not completely orthogonal, that is, equation (3) does not hold. Therefore, in practice, the DOA (direction of angle) is achieved by minimum optimization search, that is: (5) Therefore, the spectrum estimation formula of the MUSIC algorithm is: (6) in, represents the calculated spectrum peak result, represents the steering vector of the antenna array, express The conjugate transpose of represents the noise subspace, express The conjugate transpose of Indicates the angle of traversal search, represents the optimal incident angle, and argmin represents a mathematical minimum optimization solution.

[0030] S2, calculating the optimal circular array aperture corresponding to the frequency information; In this embodiment, the optimal circular array aperture corresponding to the frequency signal is calculated by taking the array element spacing as half a wavelength: (7) in, represents the optimal circular array aperture, represents the signal wavelength, Represents the number of elements in the uniform circular array.

[0031] S3, setting the adjustment range of the dynamic aperture, traversing from the array's real aperture to the optimal circular array aperture; In this embodiment, the adjustment range of the dynamic aperture is set, and the range is traversed from the real aperture to the optimal aperture in a certain step.

[0032] S4, traversing the dynamic aperture, using the MUSIC algorithm to perform direction finding within a preset range at the initial angle position, and calculating the width of each angle spectrum peak; S5. Determine whether the width of the spectrum peak is less than a preset threshold. If so, end the traversal and output the final high-resolution spatial spectrum direction finding result. Otherwise, return to S3.

[0033] In this embodiment, the dynamic aperture is traversed, and the MUSIC algorithm of S1 is used to perform direction finding within a certain range around the initial angle position, without performing a full-angle scan to reduce the amount of calculation and avoid the influence of the virtual peak position; the width of the spectrum peak at each angle is calculated, and if two adjacent signals that cannot be distinguished are together, the width of the spectrum peak will be larger, and if it is an independent signal, the spectrum peak width will be smaller; therefore, according to the set threshold, it is judged whether the spectrum peak width of the angle is an independent signal, and if the spectrum peak width is less than the set threshold, the traversal is terminated and the final direction finding result is returned; if the spectrum peak width exceeds the threshold, the iteration is continued until all apertures are traversed.

[0034] In this embodiment, two data sources are provided as an example for illustration. The two data sources include two signal sources, and the real angles are 20° and 40° respectively. Figure 2 As shown in FIG. 1 , the result without dynamic aperture adjustment is shown in FIG. 1 . The red line is the direction finding result and the green line is the true angle position. It can be seen that when the method of the present invention is not used, the two signals cannot be distinguished. Figure 3 As shown, Figure 3 The red line is the direction finding result, and the green line is the real angle position. It can be seen that after adopting the method of the present invention, the two signal sources close to each other in spatial orientation can be distinguished. Figure 2 and Figure 3 In the figure, the horizontal axis represents the angle in degrees, ranging from 0 to 360 degrees, and the vertical axis represents the size of the spectrum peak, which is normalized by the maximum value and dimensionless.

[0035] It should be noted that, since a uniform circular array is used in the launch platform, the above methods are all calculations in the uniform circular array.

[0036] In summary, through the above design, the present invention can improve the resolution of signals with close spatial intervals when the frequency does not match the array aperture, thereby increasing the applicable range of the frequency band under the aperture-invariant array, and the computational complexity of the present invention is small and easy to implement.

[0037] Example 2 like Figure 4 As shown, the present invention provides a high-resolution spatial spectrum direction finding system based on dynamic aperture adjustment, wherein the high-resolution spatial spectrum direction finding system is used to execute the high-resolution spatial spectrum direction finding method described in Example 1, including: The first processing module is used to perform direction finding using a MUSIC algorithm according to the actual aperture of the antenna array to obtain an initial angle; The second processing module is used to calculate the optimal circular array aperture corresponding to the frequency information; The third processing module is used to set the adjustment range of the dynamic aperture, traversing from the actual aperture of the antenna array to the optimal circular array aperture; The fourth processing module is used to traverse the dynamic aperture, use the MUSIC algorithm to perform direction finding within a preset range at the position of the initial angle, and calculate the width of each angle spectrum peak; The fifth processing module is used to determine whether the width of the spectrum peak is less than a preset threshold. If so, the traversal is terminated and the final high-resolution spatial spectrum direction finding result is output; otherwise, the third processing module is returned to be executed.

[0038] like Figure 4 The high-resolution spatial spectrum direction finding system provided in the illustrated embodiment can implement the technical solution shown in the high-resolution spatial spectrum direction finding method in the above method embodiment, and its implementation principle and beneficial effects are similar and will not be described in detail here.

[0039] In this embodiment, the present application can divide the functional units according to the high-resolution spatial spectrum direction finding method. For example, each function can be divided into each functional unit, or two or more functions can be integrated into one processing unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. It should be noted that the division of units in the present invention is schematic and is only a logical division. There may be other division methods in actual implementation.

[0040] In this embodiment, in order to realize the principles and beneficial effects of the high-resolution spatial spectrum direction finding method, the high-resolution spatial spectrum direction finding system includes hardware structures and / or software modules corresponding to the execution of various functions. Those skilled in the art should easily realize that, in combination with the schematic units and algorithm steps described in the embodiments disclosed in the present invention, the present invention can be implemented in the form of hardware and / or a combination of hardware and computer software. Whether a function is executed in a hardware or computer software driven manner depends on the specific application and design constraints of the technical solution. Different methods can be used for each specific application to implement the described function, but such implementation should not be considered to exceed the scope of this application.

Claims

1. A high-resolution spatial spectrum direction finding method based on dynamic aperture adjustment, characterized in that: The following steps are involved: S1. According to the actual aperture of the antenna array, use the MUSIC algorithm to perform direction finding and obtain the initial angle; S2, calculating the optimal circular array aperture corresponding to the frequency information; S3, setting the adjustment range of the dynamic aperture, traversing from the actual aperture of the antenna array to the optimal circular array aperture; S4, traversing the dynamic aperture, using the MUSIC algorithm to perform direction finding within a preset range at the initial angle position, and calculating the width of each angle spectrum peak; S5. Determine whether the width of the spectrum peak is less than a preset threshold. If so, end the traversal and output the final high-resolution spatial spectrum direction finding result. Otherwise, return to S3.

2. The high-resolution spatial spectrum direction finding method based on dynamic aperture adjustment according to claim 1, characterized in that: The S1 is specifically: Based on the received data of the antenna real aperture array, the covariance matrix is ​​calculated ; Covariance matrix Perform eigenvalue decomposition to determine the noise subspace ; Based on the determined noise subspace , combine the information parameter range to perform spectrum peak search; Based on the spectrum peak search results, find out the angle corresponding to the maximum point, which is the initial angle obtained by direction finding.

3. The high-resolution spatial spectrum direction finding method based on dynamic aperture adjustment according to claim 2, characterized in that: The covariance matrix The maximum likelihood expression of is as follows: in, Represents the data collected by each antenna array element, , Indicates Antenna array elements, represents the number of antenna array elements, express Conjugate transpose, Indicates the number of sampling snapshots, Represents a matrix.

4. The high-resolution spatial spectrum direction finding method based on dynamic aperture adjustment according to claim 2, characterized in that: The expression for performing the peak search is as follows: in, represents the calculated spectrum peak result, represents the steering vector of the antenna array, express The conjugate transpose of represents the noise subspace, express The conjugate transpose of Indicates the angle of traversal search, represents the optimal incident angle, and argmin represents a mathematical minimum optimization solution.

5. The high-resolution spatial spectrum direction finding method based on dynamic aperture adjustment according to claim 1, characterized in that: The expression of the optimal circular array aperture is as follows: in, represents the optimal circular array aperture, represents the signal wavelength, Represents the number of elements in the uniform circular array.

6. A high-resolution spatial spectrum direction finding system based on dynamic aperture adjustment, characterized in that: The high-resolution spatial spectrum direction finding system is used to execute the high-resolution spatial spectrum direction finding method according to any one of claims 1 to 5, comprising: The first processing module is used to perform direction finding using a MUSIC algorithm according to the actual aperture of the antenna array to obtain an initial angle; The second processing module is used to calculate the optimal circular array aperture corresponding to the frequency information; The third processing module is used to set the adjustment range of the dynamic aperture, traversing from the actual aperture of the antenna array to the optimal circular array aperture; The fourth processing module is used to traverse the dynamic aperture, use the MUSIC algorithm to perform direction finding within a preset range at the position of the initial angle, and calculate the width of each angle spectrum peak; The fifth processing module is used to determine whether the width of the spectrum peak is less than a preset threshold. If so, the traversal is terminated and the final high-resolution spatial spectrum direction finding result is output; otherwise, the third processing module is returned to be executed.

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