Target DOA estimation method and system for constructing differential array based on MIMO radar sparse array

Abstract

The invention relates to a target DOA estimation method and system for constructing a differential array based on an MIMO radar sparse array. The method comprises the following steps: subtracting any two array element intervals in an original MIMO sparse array to obtain an array element interval array; forming a differential array; for a non-newly-added first array element interval, if the first array element interval is the same as a certain array element interval in the original MIMO sparse array layout, putting a complex signal corresponding to the array element interval to the position of an array element corresponding to the first array element interval to serve as a first complex signal of a differential array; for the newly added second array element spacing, if only one group exists, obtaining a second complex signal based on two array element spacings in the spacing difference value corresponding to the group; if multiple groups of second complex signals exist, averaging the respective module values and phases of the multiple groups of corresponding second complex signals to obtain third complex signals; a complex signal of the differential array is obtained; and performing DOA estimation to obtain a target angle. According to the invention, the DOA angle measurement precision and accuracy are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of intelligent driving and the field of array signal processing, in particular to a target DOA (Direction of Arrival) estimation method and system based on a MIMO (Multiple Input Multiple Output) radar sparse array constructing a differential array. BACKGROUND

[0002] As one of the core sensors in intelligent driving systems, millimeter wave radars have excellent ranging, speed and angle measurement capabilities, and can better meet the requirements of environmental perception accuracy in complex vehicle application scenarios. In order to further improve the angle resolution, a sparse array design based on a MIMO (Multiple Input Multiple Output) architecture is often used to effectively expand the equivalent antenna aperture. However, the sparse array structure is prone to introduce higher grating sidelobes, leading to an increase in false alarm probability, which in turn affects normal path planning and decision-making in intelligent driving mode, and may even cause traffic safety accidents.

[0003] At present, the methods for realizing target angle estimation based on MIMO radar sparse arrays mainly fall into two categories: More is to directly use digital beam forming DBF (Digital Beam Forming) or interpolation zero padding FFT (Fast Fourier Transform) to calculate the target angle. However, such methods cannot suppress grating lobes and are prone to false alarms; A few use deterministic maximum likelihood DML (Deterministic Maximum Likelihood) or multiple signal classification MUSIC (Multiple Signal Classification) super-resolution algorithms to calculate the target angle. However, the computational complexity is much higher than that of traditional algorithms (generally more than 10 times that of DBF), making it difficult to achieve full real-time calculation in limited algorithmic vehicle radar processors. Therefore, in practical applications, super-resolution algorithms are often used only for angle accurate estimation of part of the key point cloud targets screened, in order to improve the overall perception performance while meeting real-time requirements. SUMMARY

[0004] To this end, the application provides a target DOA estimation method and system for constructing a differential array based on a MIMO radar sparse array, which can effectively suppress grating lobes, greatly reduce the probability of false alarm generation, improve the DOA angle measurement accuracy and accuracy, improve the accuracy of target detection and identification, and is beneficial to ensuring the driving safety of vehicles.

[0005] To solve the above technical problems, the application provides a target DOA estimation method for constructing a differential array based on a MIMO radar sparse array, comprising: The difference between the distance of any two elements in the original MIMO sparse array is obtained to obtain a non-negative distance difference value, and the distance column is obtained based on all the distance difference values; and the complex signal of the original MIMO array is obtained based on the original MIMO sparse array; After removing the repeated values of the element distance array, a differential array is formed; The differential array and the original MIMO sparse array are compared, for the first element distance in the differential array that is not newly added relative to the original MIMO sparse array, if the first element distance is the same as a certain element distance in the layout of the original MIMO sparse array, the complex signal corresponding to the element distance is placed in the position of the corresponding element of the first element distance as the first complex signal of the differential array; For the second element distance newly added, if there is only one group, the second complex signal is obtained based on the product of the complex signal corresponding to the two element distances in the group and the conjugate complex signal thereof; if there are multiple groups, the third complex signal is obtained after the modulus and phase of the respective second complex signals corresponding to the multiple groups are averaged; The complex signal of the differential array is obtained based on the first complex signal, the second complex signal and the third complex signal; The DOA of the target angle is obtained by performing DOA estimation on the complex signal of the original sparse array and the complex signal of the differential array respectively.

[0006] In an embodiment of the application, the distribution rule of the original MIMO sparse array is: , Wherein, The element distance of the original MIMO sparse array is an integer multiple of the half wavelength of the incident signal, and n is the number of elements of the original MIMO sparse array.

[0007] In an embodiment of the application, the element distance array is represented as: ; Wherein, , are the i-th and j-th element spacing in the array of element spacing, respectively, and n is the number of elements.

[0008] In one embodiment of the present application, the complex signal representation of the original MIMO array is: , where n is the number of elements, is the modulus of the complex signal of the n-th element, is the phase of the complex signal of the n-th element.

[0009] In one embodiment of the present application, the differential array is represented as: , where, is the element spacing of the differential array, which is an integer multiple of the half wavelength of the incident signal, and m is the number of elements of the differential array.

[0010] In one embodiment of the present application, the second complex signal is obtained based on the product of the complex signal corresponding to two element spacings in the set of corresponding spacing differences and its conjugate complex signal, comprising: The second complex signal is calculated based on the following formula: , where the second element spacing is , is obtained from a certain group , , are the i-th and j-th element spacing in the array of element spacing, respectively, , is the complex signal of , is the conjugate complex of .

[0011] In one embodiment of the present application, the third complex signal is obtained by taking the average of the modulus and phase of each of the second complex signals corresponding to multiple groups of corresponding second complex signals, respectively, comprising: The third complex signal is calculated based on the following formula: , where, is the average of the modulus of each second complex signal, is the average of the phase of each second complex signal, and j is the imaginary unit.

[0012] In one embodiment of the present application, the complex signal of the differential array is obtained based on the first complex signal, the second complex signal and the third complex signal, comprising: According to the order of the differential array, a complex signal corresponding to an array element is obtained; , wherein m is the number of array elements of the differential array, is a modulus value of the mth array element complex signal, is a phase of the mth array element complex signal, and j is an imaginary unit.

[0013] In an embodiment of the present application, DOA estimation is performed on the complex signals of the original sparse array and the complex signals of the differential array respectively to obtain target angles, including: DOA estimation is performed on the complex signals of the original sparse array and the complex signals of the differential array respectively by an angle measurement algorithm including DBF; After DOA detection of the complex signals of the original sparse array, a first angle set is obtained, and after DOA detection of the complex signals of the differential array, a second angle set is obtained; angle values in the first angle set and angle values in the second set are matched two by two, and a matching degree is calculated: , wherein, is a coefficient factor; If the matching degree is higher than a set matching degree threshold, it is considered that the target angle matching is successful, and the angle values in the second angle set matched successfully in the target angle matching are output as the target angle.

[0014] The present application also provides a target DOA estimation system based on a MIMO radar sparse array and a differential array, including: An array spacing array acquisition module is configured to subtract the spacing between any two array elements in an original MIMO sparse array to obtain corresponding non-negative spacing difference values, and based on all the spacing difference values, an array spacing array is obtained; and based on the original MIMO sparse array, complex signals of the original MIMO array are obtained; A differential array acquisition module is configured to form a differential array after removing repeated values from the array spacing array; The differential array complex signal acquisition module is configured to compare the differential array and the original MIMO sparse array, for a first array element spacing which is not newly added in the differential array relative to the original MIMO sparse array, if the first array element spacing is the same as a certain array element spacing in the layout of the original MIMO sparse array, the complex signal corresponding to the array element spacing is placed in the position of the array element corresponding to the first array element spacing as the first complex signal of the differential array; for a second array element spacing which is newly added, if there is only one group, the second complex signal is obtained based on the product of the complex signal corresponding to two array element spacings in the spacing difference value corresponding to the group and the conjugate complex signal thereof; if there are multiple groups, the third complex signal is obtained after the modulus and the phase of the second complex signals corresponding to the multiple groups are respectively averaged; and the complex signal of the differential array is obtained based on the first complex signal, the second complex signal and the third complex signal. The target angle acquisition module is configured to respectively perform DOA estimation on the complex signal of the original sparse array and the complex signal of the differential array to obtain a target angle.

[0015] The above technical scheme of the present application has the following advantages compared with the prior art: The target DOA estimation method and system for constructing a differential array based on a MIMO radar sparse array can effectively suppress the grating lobe phenomenon, significantly reduce the probability of false alarm, improve the accuracy and accuracy of DOA angle measurement, and improve the reliability of target detection and identification. The method is suitable for 3D radar and 4D radar systems, wherein for multiple groups of azimuth dimension arrays with the same pitch dimension in the 4D radar, the azimuth angle can be estimated and then comprehensively judged to obtain the angle of the target, so as to ensure the accuracy of the azimuth angle, reduce the generation of false alarms, and have good universality and engineering adaptability. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the drawings.

[0017] Figure 1 It is a flowchart of the target DOA estimation method for constructing a differential array based on a MIMO radar sparse array.

[0018] Figure 2 It is a 3D radar beam diagram (horizontal coordinate: angle; vertical coordinate: energy normalization).

[0019] Figure 3 It is a beam diagram of multiple groups of azimuth dimension arrays of a 4D radar (horizontal coordinate: angle; vertical coordinate: energy normalization). DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand and implement the present application, but the embodiments are not intended to limit the present application.

[0021] In the present application, if the directions (up, down, left, right, front and back) are described, it is only for the convenience of describing the technical solutions of the present application, and is not intended to indicate or imply that the indicated technical features must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application.

[0022] In the present application, the meaning of "several" is one or more, and the meaning of "multiple" is two or more. "Greater than", "less than", "more than" and the like are understood as not including the number; "above", "below", "within" and the like are understood as including the number. In the description of the present application, if "first" and "second" are described, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0023] In the present application, unless otherwise explicitly limited, the words "set", "install", "connect" and the like should be broadly understood, for example, they can be directly connected, or indirectly connected through an intermediate medium; can be fixedly connected, or can be detachably connected, or can be integrally formed; can be mechanically connected, or can be electrically connected or capable of communicating with each other; can be the internal communication or interaction relationship of two elements. The skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solutions.

[0024] Example 1 Referring to Figure 1 The present embodiment provides a target DOA estimation method based on MIMO sparse array to construct a differential array, which comprises: S1, the difference between the distance of any two elements in the original MIMO sparse array is obtained, and the corresponding non-negative distance difference value is obtained. Based on all the distance difference values, the element distance array is obtained. Based on the original MIMO sparse array, the complex signal of the original MIMO array is obtained.

[0025] Specifically, the distribution rule of the original MIMO sparse array is: , Wherein, is the element distance of the original MIMO sparse array, which is an integer multiple of the half wavelength of the incident signal, and n is the number of elements of the original MIMO sparse array. The layout of the original MIMO sparse array (MIMO_Array) is {0, 5, 7, 8, 12, 19}.

[0026] The array of element spacings is represented as: ; Wherein, , are the i-th and j-th element spacings in the array of element spacings, and n is the number of elements.

[0027] The complex signal of the original MIMO array (MIMO_Complex_Signal) is represented as: , Wherein, n is the number of elements, is the modulus of the complex signal of the n-th element, is the phase of the complex signal of the n-th element.

[0028] S2, after removing the repeated values from the array of element spacings, a difference array is formed.

[0029] Specifically, the difference array is represented as: , Wherein, is the element spacing of the difference array, which is an integer multiple of the half wavelength of the incident signal, and m is the number of elements of the difference array. The original difference array layout (MIMO_Array_Diff) is {0, 1, 2, 3, 4, 5, 7, 8, 10, 11, 12, 14, 15, 19}.

[0030] S3, comparing the difference array and the original MIMO sparse array, for the first element spacing in the difference array that is not newly added relative to the original MIMO sparse array , if the first element spacing is the same as a certain element spacing in the original MIMO sparse array layout, the complex signal corresponding to the element spacing is placed in the position of the corresponding element of the first element spacing , as the first complex signal of the difference array, that is .

[0031] S4, for the second element spacing that is newly added , is obtained from one or more groups ; if there is only one group, the second complex signal is obtained based on the product of the complex signal corresponding to the two element spacings in the interval difference value corresponding to the group and its conjugate complex signal; the second complex signal is calculated based on the following formula: , Wherein, the second element spacing is , is obtained by a certain group , , are the i-th and j-th element spacing in the array respectively, , is a complex signal of , is a conjugate complex of .

[0032] If there are multiple groups, the second complex signals corresponding to the multiple groups are After the modulus and phase of each are respectively averaged, a third complex signal is obtained.

[0033] The third complex signal is calculated based on the following formula: , wherein, is the average of the modulus of each second complex signal, is the average of the phase of each second complex signal, and j is an imaginary unit.

[0034] S5, based on the first complex signal, the second complex signal and the third complex signal, a complex signal of the differential array (MIMO_Array_Diff_Complex_Signal) is obtained.

[0035] Specifically, the complex signal of the corresponding element is obtained in the order of the differential array; , wherein m is the number of elements of the differential array, is the modulus of the m-th element complex signal, is the phase of the m-th element complex signal, and j is an imaginary unit.

[0036] S6, the complex signal of the original sparse array and the complex signal of the differential array are respectively subjected to DOA estimation, and a target angle is obtained.

[0037] Specifically, taking the DBF angle measurement algorithm as an example, the complex signal of the original sparse array and the complex signal of the differential array are respectively subjected to DOA estimation, which includes: S61 the results after the DOA detection of the complex signal of the original sparse array form a first angle set A, and the results after the DOA detection of the complex signal of the differential array form a second angle set B; S62 the angle values in the first angle set A and the angle values in the second set B are matched two by two, and a matching degree is calculated: , is a coefficient factor.

[0038] S63 filters out the angle value in the second angle set B where the matching degree is higher than the set matching degree threshold value, and the angle value in the second angle set B where the matching degree is higher than the set matching degree threshold value is regarded as a target angle matching success.

[0039] After the DOA estimation, the obtained 3D radar beam diagram is as shown in Figure 2 .

[0040] Further, the above method is also applicable to a 4D radar. The 3D radar is an array with only one set of azimuth dimensions, and the 4D radar has multiple sets of azimuth dimensions at different elevation positions. The method is applicable to both the 3D radar and the 4D radar.

[0041] After the DOA estimation of the multiple sets of azimuth dimension arrays of the 4D radar, the azimuth angle of the target is obtained through comprehensive decision, which can ensure the accuracy of the azimuth angle and reduce the generation of false alarms. The following will take the original sparse array of a specific 4D radar array layout as an example for description.

[0042] The difference array is constructed for the multiple sets of azimuth dimension arrays of the 4D radar. The DOA estimation is performed on the multiple sets of difference arrays.

[0043] The matching decision and statistical analysis are performed on the multiple sets of DOA results, and finally the angle of the target is obtained.

[0044] The beam diagram of the multiple sets of azimuth dimension arrays of the 4D radar is as shown in Figure 3 .

[0045] By constructing the difference array through the sparse array and then performing the DOA estimation, the grating lobes can be effectively suppressed, the probability of false alarm can be greatly reduced, the DOA angle measurement precision and accuracy can be improved, the accuracy of target detection and identification can be improved, and the driving safety of the vehicle can be ensured.

[0046] Embodiment 2 Based on the same inventive concept, the embodiment provides a target DOA estimation system based on the MIMO radar sparse array constructing difference array, which has a similar problem solving principle to the target DOA estimation method based on the MIMO radar sparse array constructing difference array, and the repeated parts will not be described herein.

[0047] The embodiment provides a target DOA estimation system based on the MIMO radar sparse array constructing difference array, which comprises: ​An element spacing array acquisition module is configured to subtract any two element spacings in the original MIMO sparse array to obtain a corresponding non-negative spacing difference value, and obtain an element spacing array based on all the spacing difference values; and obtain a complex signal of the original MIMO array based on the original MIMO sparse array; A difference array acquisition module is configured to form a difference array after removing repeated values from the element spacing array; A difference array complex signal acquisition module is configured to compare the difference array and the original MIMO sparse array, for a first element spacing in the difference array that is not newly added relative to the original MIMO sparse array, if the first element spacing is the same as a certain element spacing in the layout of the original MIMO sparse array, put a complex signal corresponding to the element spacing into a position of an element corresponding to the first element spacing as a first complex signal of the difference array; for a second element spacing that is newly added, if there is only one group, obtain a second complex signal based on a product of a complex signal corresponding to two element spacings in the group and a conjugate complex signal thereof; if there are multiple groups, obtain a third complex signal by taking an average of a modulus and a phase of the second complex signals corresponding to the multiple groups respectively; and obtain a complex signal of the difference array based on the first complex signal, the second complex signal and the third complex signal. A target angle acquisition module is configured to respectively perform DOA estimation on the complex signal of the original sparse array and the complex signal of the difference array to obtain a target angle.

[0048] Those skilled in the art will understand that embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0049] The present application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in a flow or multiple flows and / or blocks Figure 1 The functions specified in a flow or multiple flows and / or blocks

[0050] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flow Figure 1 one or more flow or block Figure 1 one or more blocks or steps of the flow.

[0051] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that are executed on the computer or other programmable apparatus provide steps for implementing the flow Figure 1 one or more flow or block Figure 1 one or more blocks or steps of the flow.

[0052] Finally, it should be noted that the detailed description of the specific embodiments is merely intended to teach one skilled in the art the way to make and use the technical solutions of the present application and is not intended to limit the technical solutions of the present application. Although the present application has been described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A target DOA estimation method based on MIMO radar sparse array constructing differential array, characterized in that, The method comprises the following steps: Subtracting any two element spacings in the original MIMO sparse array to obtain corresponding non-negative spacing difference values, and obtaining an element spacing column based on all the spacing difference values; Based on the original MIMO sparse array, obtaining the complex signal of the original MIMO array; After removing repeated values from the element spacing array, a difference array is formed; Comparing the difference array and the original MIMO sparse array, for a first element spacing in the difference array that is not newly added relative to the original MIMO sparse array, if the first element spacing is the same as a certain element spacing in the layout of the original MIMO sparse array, the complex signal corresponding to the element spacing is placed in the position of the corresponding element of the first element spacing as the first complex signal of the difference array; For a second element spacing that is newly added, if there is only one group, a second complex signal is obtained based on the product of the complex signal corresponding to the two element spacings in the group and the conjugate complex signal thereof; If there are multiple groups, a third complex signal is obtained after the modulus and phase of the corresponding second complex signals of the multiple groups are averaged respectively; Based on the first complex signal, the second complex signal and the third complex signal, the complex signal of the difference array is obtained; 2. The method of claim 1, wherein the method is implemented by a MIMO radar sparse array. Respectively performing DOA estimation on the complex signal of the original sparse array and the complex signal of the difference array to obtain the target angle. ， wherein, is the element spacing of the original MIMO sparse array, which is an integer multiple of the half wavelength of the incident signal, and n is the number of elements of the original MIMO sparse array.

3. The method of claim 2, wherein the method is implemented by a MIMO radar sparse array. The distribution rule of the original MIMO sparse array is: ； wherein , are the i-th and j-th element spacing in the array of element spacings, respectively, and n is the number of elements.

4. The method of claim 1, wherein the method is implemented by a MIMO radar sparse array. The element spacing array is represented as: ， where n is the number of array elements, is the magnitude of the complex signal of the nth array element, is the phase of the complex signal of the nth array element.

5. The method of claim 3, wherein the method is characterized by, The complex signal of the original MIMO array is represented as: ， wherein is the element spacing of the differential array, which is an integer multiple of the half wavelength of the incident signal, and m is the number of elements of the differential array.

6. The method of claim 5, wherein the method is based on a MIMO radar sparse array to build a differential array for target DOA estimation. The difference array is represented as: The second complex signal is obtained based on the product of the complex signal corresponding to the two element spacings in the group and the conjugate complex signal thereof, comprising: ， wherein the second array element spacing is , is obtained from a set of , , are the i-th and j-th array element spacing of the array of array element spacings, respectively, , is a complex signal of , is a conjugate complex of .

7. The method of claim 1, wherein the method is implemented by a MIMO radar sparse array. The second complex signal is calculated based on the following formula: The third complex signal is obtained after the modulus and phase of the corresponding second complex signals of the multiple groups are averaged respectively, comprising: ， wherein is a mean value of the modulus of each second complex signal, is a mean value of the phase of each second complex signal, j is the imaginary unit.

8. The method of claim 1, wherein the method is implemented by a MIMO radar sparse array. The third complex signal is calculated based on the following formula: The complex signal of the difference array is obtained based on the first complex signal, the second complex signal and the third complex signal, comprising: ， Wherein, m is the number of elements of the differential array, is the modulus of the complex signal of the mth element, is the phase of the complex signal of the mth element, and j is the imaginary unit.

9. The method of claim 1, wherein the method is implemented by a MIMO radar sparse array. The complex signal of the corresponding element is obtained by arranging in the order of the difference array; Respectively performing DOA estimation on the complex signal of the original sparse array and the complex signal of the difference array to obtain the target angle, comprising: Respectively performing DOA estimation on the complex signal of the original sparse array and the complex signal of the difference array through an angle measurement algorithm including DBF; angle values in the first set of angles and angle values in the second set are matched two by two and a degree of matching is calculated : ， wherein is a coefficient factor; After the DOA detection of the complex signal of the original sparse array, a first angle set is obtained, and after the DOA detection of the complex signal of the difference array, a second angle set is obtained; 10. A target DOA estimation system based on MIMO radar sparse array constructing differential array, characterized in that, If the matching degree is higher than a set matching degree threshold, it is considered that the target angle matching is successful, and the angle value in the second angle set that matches the target angle successfully is output as the target angle. The method comprises the following steps: An element spacing array acquisition module is configured to subtract any two element spacings in the original MIMO sparse array to obtain corresponding non-negative spacing difference values, and obtain an element spacing array based on all the spacing difference values; Based on the original MIMO sparse array, the complex signal of the original MIMO array is obtained. a differential array acquisition module, configured to form a differential array after removing repeated values from the array interval array; a differential array complex signal acquisition module, configured to compare the differential array and the original MIMO sparse array, for a first array interval in the differential array that is not newly added relative to the original MIMO sparse array, if the first array interval is the same as a certain array interval in the layout of the original MIMO sparse array, a complex signal corresponding to the array interval is placed in a position of an array element corresponding to the first array interval, as a first complex signal of the differential array; for a second array interval that is newly added, if there is only one group, a second complex signal is obtained based on a product of a complex signal corresponding to two array intervals in the group and a conjugate complex signal thereof; if there are multiple groups, a third complex signal is obtained after taking an average of a modulus and a phase of each of the second complex signals corresponding to the multiple groups respectively; and the complex signal of the differential array is obtained based on the first complex signal, the second complex signal and the third complex signal; a target angle acquisition module, configured to perform DOA estimation on the complex signal of the original sparse array and the complex signal of the differential array respectively, to obtain a target angle. ​

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