A High-Resolution Spatial Spectrum Direction Finding Method and System Based on Dynamic Aperture Adjustment

Abstract

The present invention provides a high-resolution spatial spectrum direction finding method and system based on dynamic aperture adjustment, belonging to the field of communication technologies. The present invention dynamically adjusts the aperture, calculates the direction finding result under this aperture, and judges whether this direction finding result is valid according to certain criteria. If the direction finding result is valid, it stops adjusting the aperture and returns the direction finding result. If the direction finding result is invalid, it continues to adjust the aperture until the upper limit of aperture adjustment is reached. If there is no valid direction finding result even when the upper limit is reached, it returns the direction finding result of the initial aperture. The present invention solves the technical problem of insufficient direction finding resolution caused by a small array aperture corresponding to the signal frequency.

Description

Technical Field

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

[0002] The core of spatial signal source localization is the DOA (direction-of-arrival) estimation technology, which is an important research topic in array signal processing. Among many DOA estimation methods, the MUSIC algorithm constructs a spatial spectrum function by using the orthogonality between the signal subspace and the noise subspace, and estimates the DOA of the signal through spectral peak search. Under the premise of an accurate signal model, the MUSIC algorithm can theoretically achieve arbitrarily high resolution. However, in practical applications, when the spatial intervals of signal sources are close, the estimation performance of the MUSIC algorithm gradually deteriorates and even completely fails. 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. However, it is unrealistic to significantly increase the physical size of the array in a real environment. Due to the weight limitation of the airborne platform and the need to perform direction finding over a wide frequency band range, but not being able to have too many antenna layers, the frequency does not match the array aperture, resulting in the inability to resolve signals with close intervals.

[0003] Traditional methods based on virtual array expansion or translation can increase the virtual aperture of the array, and thus can improve 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 for direction finding. Multiple covariance matrix solutions and spectral peak searches will increase the computational complexity and reduce the real-time performance of the system. Summary of the Invention

[0004] Aiming at the above 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] To achieve the above object, the technical solution adopted by the present invention is as follows: A high-resolution spatial spectrum direction finding method based on dynamic aperture adjustment, comprising the following steps:

[0006] S1. Perform direction finding using the MUSIC algorithm according to the actual aperture of the antenna array to obtain the initial angle;

[0007] S2. Calculate the optimal circular array aperture corresponding to the frequency information;

[0008] S3. Set the adjustment range of the dynamic aperture and traverse from the actual aperture of the antenna array to the optimal circular array aperture;

[0009] S4. Traverse the dynamic aperture, perform direction finding using the MUSIC algorithm within a preset range at the initial angle position, and calculate the width of each angle spectrum peak;

[0010] 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.

[0011] 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 a relatively close spatial interval when the frequency does not match the array aperture. Therefore, the applicable frequency band range of the array with an unchanged aperture is increased, and the computational complexity of the present invention is small and it is easy to implement.

[0012] Further, the specific content of S1 is as follows:

[0013] Based on the received data of the antenna true aperture array, calculate the covariance matrix ;

[0014] Perform eigenvalue decomposition on the covariance matrix to determine the noise subspace ;

[0015] Based on the determined noise subspace , perform spectrum peak search in combination with the information parameter range;

[0016] Based on the spectrum peak search result, find the angle corresponding to the maximum value point, and this angle is the initial angle obtained by direction finding.

[0017] Still further, the maximum likelihood expression of the covariance matrix is as follows:

[0018]

[0019]

[0020] where represents the data collected by each antenna element, , represents the th antenna element, represents the number of antenna elements, represents conjugate transpose, represents the number of sampling snapshots, represents a matrix.

[0021] Still further, the expression for performing spectrum peak search is as follows:

[0022]

[0023]

[0024] Among them, represents the calculated spectral peak result, represents the steering vector of the antenna array, represents the conjugate transpose of represents the noise subspace, represents the conjugate transpose of represents the angle of traversal search, represents the optimal incident angle, and argmin represents a mathematical minimum optimization solution.

[0025] Furthermore, the expression of the optimal circular array aperture is as follows:

[0026]

[0027] Among them, represents the optimal circular array aperture, represents the signal wavelength, represents the number of array elements of the uniform circular array.

[0028] The present invention provides a high-resolution spatial spectrum direction-finding system based on dynamic aperture adjustment. The high-resolution spatial spectrum direction-finding system is used to execute a high-resolution spatial spectrum direction-finding method, including:

[0029] A first processing module, configured to perform direction finding using the MUSIC algorithm according to the actual aperture of the antenna array to obtain an initial angle;

[0030] A second processing module, configured to calculate the optimal circular array aperture corresponding to the frequency information;

[0031] A third processing module, configured to set the adjustment range of the dynamic aperture and traverse from the actual aperture of the antenna array to the optimal circular array aperture;

[0032] A fourth processing module, configured to traverse the dynamic aperture, perform direction finding using the MUSIC algorithm within a preset range at the position of the initial angle, and calculate the width of each angle spectral peak;

[0033] A fifth processing module, configured to determine whether the width of the spectral 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 execute the third processing module.

[0034] 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 a relatively close spatial interval when the frequency does not match the array aperture. Therefore, the applicable frequency band range of the array with a constant aperture is increased, and the computational complexity of the present invention is small and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flowchart of the method of the present invention.

[0036] Figure 2 It is a schematic diagram of the result without dynamic aperture adjustment.

[0037] Figure 3 It is a schematic diagram of the result with dynamic aperture adjustment.

[0038] Figure 4 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] The following describes the specific implementation manners of the present invention to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation manners. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions created using the concept of the present invention are within the scope of protection.

[0040] Example 1

[0041] Before explaining the present invention, the following terms are first explained:

[0042] The MUSIC algorithm is a method based on matrix eigen - space decomposition.

[0043] As Figure 1 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:

[0044] S1. According to the actual aperture of the antenna array, use the MUSIC algorithm for direction - finding to obtain the initial angle, and its implementation method is as follows:

[0045] Based on the received data of the antenna real - aperture array, calculate the covariance matrix ;

[0046] Perform eigenvalue decomposition on the covariance matrix to determine the noise subspace ;

[0047] Based on the determined noise subspace , perform spectral peak search in combination with the information parameter range;

[0048] Based on the spectral peak search results, find the angle corresponding to the maximum value point, and this angle is the initial angle obtained by direction finding.

[0049] In this embodiment, the covariance matrix of the received data is obtained as follows:

[0050] (1)

[0051] Among them, represents the covariance matrix, represents a mathematical operation of taking the expectation, , represents a matrix, Each element in the matrix is , represents the data collected by each antenna element, , represents the th antenna element, represents the number of antenna elements, represents the conjugate transpose of, represents the steering vector matrix, represents the matrix A Each element in (each element is at an angle ), represents the steering vector, represents the number of true signals, represents the conjugate transpose of, , represents a matrix, represents the matrix The rd signal in, and each element in the matrix is the data of the signal, and there are signals in total; represents the noise, represents the conjugate transpose of, represents the power of, represents the identity matrix, represents the covariance matrix of the signal.

[0052] Then, perform eigenvalue decomposition on the covariance matrix R :

[0053] (2)

[0054] Among them, represents the subspace spanned by the eigenvectors corresponding to the large eigenvalues, that is, the signal subspace, Denote the signal eigenvalue, Denote the subspace spanned by the eigenvectors corresponding to the small eigenvalues, i.e., the noise subspace, Denote the noise eigenvalue, Denote The conjugate transpose of, Denote The conjugate transpose of.

[0055] 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:

[0056] (3)

[0057] Wherein, Denote the steering vector of the antenna array, Denote The conjugate transpose of, Denote the noise subspace, Denote the angle of the traversal search.

[0058] The classical MUSIC algorithm is proposed based on the above property. However, considering that the actual received data matrix is of finite length, that is, the maximum likelihood estimate of the covariance matrix Is:

[0059] (4)

[0060] Wherein, , Denote the data collected by each antenna element, , Denote the th antenna element, Denote the number of antenna elements, Denote Conjugate transpose, Denote the number of sampling snapshots, Denote the matrix, and each element inside is , Denote the data collected by each antenna element.

[0061] Performing eigenvalue decomposition on the covariance matrix Can calculate and obtain the noise subspace . Due to the existence of noise, And the noise subspace Cannot be completely orthogonal, that is, equation (3) does not hold. Therefore, in fact, finding the DOA (direction of angle) is achieved by minimum optimization search, that is:

[0062] (5)

[0063] Therefore, the spectral estimation formula of the MUSIC algorithm is as follows:

[0064] (6)

[0065] Wherein, represents the calculated spectral peak result, represents the steering vector of the antenna array, represents the conjugate transpose of represents the noise subspace, represents the conjugate transpose of represents the angle of traversal search, represents the optimal incident angle, and argmin represents a mathematical minimum optimization solution.

[0066] S2. Calculate the optimal circular array aperture corresponding to the frequency information;

[0067] In this embodiment, to calculate the optimal circular array aperture corresponding to the frequency signal, it is calculated with the element spacing being half a wavelength:

[0068] (7)

[0069] Wherein, represents the optimal circular array aperture, represents the signal wavelength, represents the number of elements of the uniform circular array.

[0070] S3. Set the adjustment range of the dynamic aperture and traverse from the actual aperture of the array to the optimal circular array aperture;

[0071] In this embodiment, set the adjustment range of the dynamic aperture, and traverse from the actual aperture to the optimal aperture with a certain step.

[0072] S4. Traverse the dynamic aperture, use the MUSIC algorithm to perform direction finding within the preset range at the initial angle position, and calculate the width of each angle spectral peak;

[0073] S5. Determine whether the width of the spectral peak is less than the preset threshold. If so, end the traversal and output the final high-resolution spatial spectral direction finding result; otherwise, return to S3.

[0074] In this embodiment, the dynamic aperture is traversed, and direction finding is performed within a certain range on the left and right at the initial angular position using the MUSIC algorithm of S1, instead of performing a full-angle scan to reduce the computational load and avoid the influence of the virtual peak position; the width of each angular spectral peak is calculated. If two adjacent signals that cannot be resolved are together, the width of this spectral peak will be larger, while if it is an independent signal, the spectral peak width will be relatively small; therefore, according to the set threshold, it is determined whether the spectral peak width at this angle is an independent signal. If the spectral peak widths are all less than the set threshold, the traversal ends and the final direction finding result is returned; if the spectral peak width exceeds the threshold, continue to iterate until all apertures are traversed.

[0075] In this embodiment, two data sources are provided as an example for illustration. The two data sources include 2 signal sources, and the true angles are 20° and 40° respectively. As Figure 2 shown, for the result without dynamic aperture adjustment, the red line is the direction finding result, and the green line is the true angular position. It can be seen that when the method of the present invention is not adopted, these two signals cannot be resolved. As Figure 3 shown, Figure 3 for the result of dynamic aperture adjustment, the red line is the direction finding result, and the green line is the true angular position. It can be seen that after adopting the method of the present invention, these two signal sources with adjacent spatial orientations can be resolved. Among them, Figure 2 and Figure 3 the abscissa represents the angle, the unit is °, the range is 0~360°, and the ordinate represents the magnitude of the spectral peak value, which is normalized by the maximum value and is dimensionless.

[0076] It should be noted that since a uniform circular array is used in the airborne platform, the above methods are all calculated in the uniform circular array.

[0077] In summary, through the above design, the present invention can improve the resolution of signals with a close spatial interval when the frequency does not match the array aperture. Therefore, the applicable frequency band range of the array with a constant aperture is increased, and the computational load of the present invention is small and it is easy to implement.

[0078] Embodiment 2

[0079] As Figure 4 shown, the present invention provides a high-resolution spatial spectrum direction finding system based on dynamic aperture adjustment. The high-resolution spatial spectrum direction finding system is used to execute the high-resolution spatial spectrum direction finding method described in Embodiment 1, and includes:

[0080] A first processing module, configured to perform direction finding using the MUSIC algorithm according to the true aperture of the antenna array to obtain an initial angle;

[0081] A second processing module, configured to calculate the optimal circular array aperture corresponding to the frequency information;

[0082] A third processing module, configured to set an adjustment range of a dynamic aperture and traverse from the actual aperture of the antenna array to the optimal circular array aperture;

[0083] A fourth processing module, configured to traverse the dynamic aperture, perform direction finding within a preset range at the position of the initial angle by using the MUSIC algorithm, and calculate the width of each angle spectrum peak;

[0084] A fifth processing module, configured to 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 execute the third processing module.

[0085] Such as Figure 4 The high-resolution spatial spectrum direction finding system provided by the embodiment shown can execute the technical solution shown in the high-resolution spatial spectrum direction finding method of the above method embodiment. The implementation principle and beneficial effects are similar, and will not be elaborated here.

[0086] In this embodiment, the present application can divide 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 integrated unit can be implemented in the form of hardware or in the form of a software functional unit. It should be noted that the division of units in the present invention is illustrative, only a logical division, and there can be other division methods in actual implementation.

[0087] In this embodiment, in order to implement the principle and beneficial effects of the high-resolution spatial spectrum direction finding method, the high-resolution spatial spectrum direction finding system includes corresponding hardware structures and / or software modules for executing each function. 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 certain function is executed in the way of hardware or computer software driving 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 the present 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; 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 of the uniform circular array; 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. 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 4, 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 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 of the uniform circular array; 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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