Near-field and far-field data transformation method and device based on transfer matrix

Abstract

The present invention relates to a near-field and far-field data transformation method and device based on a transfer matrix. The method comprises the following steps: calculating the minimum synthetic aperture angle Φ required for near-field and far-field data transformation; performing grid processing on the target area; constructing a near-field observation matrix A N ; Construct far-field reconstruction matrix A F ; Based on the near-field observation matrix A N and the far-field reconstruction matrix A F Construct a transfer matrix A; realize the mapping of the target's near-field scattering characteristic data to the far-field scattering characteristic data through the transfer matrix A. The method of the present invention directly establishes the mapping relationship between the target's near-field and far-field scattering characteristics with the help of the transfer matrix concept, and can quickly and accurately transform the target's near-field scattering characteristic data to the far field.

Description

Technical Field

[0001] The present invention relates to the technical field of RCS testing and data processing, and in particular to a data conversion method and device for extrapolating electromagnetic scattering test data under near-field conditions to far-field conditions. Background Art

[0002] The definition of target RCS (radar cross-section) is a far-field concept, which requires that the incident wave illuminating the target and the scattered wave reaching the receiving antenna are both plane waves. However, a truly ideal plane wave does not exist; in engineering, outdoor field RCS testing generally adopts a far-field approach, that is, the distance between the target and the measurement system is far enough that the incident wave and the scattered wave are approximately plane waves; indoors, parabolic reflectors and other equipment are used to convert the spherical waves radiated by the feed source into plane waves within a certain area. When the test conditions are limited and it is impossible to achieve an approximate plane wave, the researchers use the near-far field transformation measurement method to extract the target's far-field scattering information from the near-field scattered echo, and then obtain the RCS.

[0003] The existing near-field and far-field transformation methods mainly include: the near-field and far-field transformation method based on the antenna coupling formula (the chain transfer relationship between near-field scattering and far-field RCS), the plane wave synthesis method, the method based on the invariant target scattering distribution function, and the near-field and far-field transformation method based on synthetic aperture. Among them, the near-field and far-field transformation method based on the antenna coupling formula requires complete dual-station information of the target, which is difficult to implement in engineering; the plane wave synthesis method uses an antenna unit or a group of units to perform weighted transmission at each unit position successively or simultaneously, and the field at a certain point in space is also superimposed successively or simultaneously. The method of weighted summation of spherical waves within a certain area forms an approximate plane wave. This method is currently mainly used for antenna testing, and the efficiency of testing the scattering characteristics of large targets is low; the method based on the invariant target scattering distribution function uses the basic principle of ISAR imaging to invert the target scattering distribution function from the near-field test value. The disadvantage of this method is that it is necessary to image the target first and then extract the scattering center for reconstruction. The process is relatively complicated, and it cannot process point frequency data.

[0004] The near-far field transformation method CNFFFT (Circular Near-Field to Far-Field Transformation) based on synthetic aperture is an improvement on the invariant method based on the scattering distribution function. This method does not require imaging and uses the Hankel function to correct the phase term to achieve the transformation from the target near-field scattering characteristics to the far-field RCS. It is currently a method widely used in near-field test engineering. The problem with the CNFFT method is that the method uses the superposition theorem of Bessel functions and the bulk Hankel function approximation when deriving the cylindrical wave integral and expansion. Therefore, it is mainly used for near-far field transformation under the circular uniform sampling mode. However, the actual near-field test mostly uses the linear scanning mode, so the CNFFT method is difficult to apply directly.

[0005] In view of the above shortcomings, it is necessary to provide an improved target near-field / far-field data conversion method which is simple in form, easy to implement and has strong versatility, so as to solve the problem of transforming the target near-field scattering characteristics to the far-field RCS in actual engineering tests. Summary of the invention

[0006] The technical problem to be solved by the present invention is that the near-field to far-field transformation method is complex in form and has poor versatility. In view of the defects in the prior art, based on the principle of invariance of scattering distribution function, an improved target near-field / far-field data conversion method is provided which is simple in form, easy to implement and has strong versatility, so as to solve the problem of transforming the target near-field scattering characteristics to far-field RCS in actual engineering tests.

[0007] In order to solve the above technical problems, the present invention provides a near-field and far-field data transformation method based on a transfer matrix, comprising the following steps: calculating the minimum synthetic aperture angle Φ required for near-field and far-field data transformation; performing grid processing on the target area; constructing a near-field observation matrix A N , near-field observation matrix A N Realize the mapping of near-field scattering characteristic data to the target scattering center; construct the far-field reconstruction matrix A F , the far-field reconstruction matrix A F Realize the mapping of target scattering center to far-field scattering characteristic data; based on the near-field observation matrix A N and the far-field reconstruction matrix A F Construct a transfer matrix A; and realize the mapping of the near-field scattering characteristic data of the target to the far-field scattering characteristic data through the transfer matrix A.

[0008] Preferably, the minimum synthetic aperture angle Φ means that, for a specific azimuth angle Φ0, the minimum value of the azimuth angle area of ​​the near-field test should be less than or equal to Φ0-Φ / 2, and the maximum value of the azimuth angle area of ​​the near-field test should be greater than or equal to Φ0+Φ / 2.

[0009] Preferably, in the step of calculating the minimum synthetic aperture angle Φ required for near-field and far-field data transformation, the minimum synthetic aperture angle Φ is expressed as:

[0010]

[0011] Where R is the test distance and D is the maximum horizontal size of the target.

[0012] Preferably, in the step of gridding the target area, the gridding area is centered on the center of the target area, and an area with a horizontal length and a vertical length of D is constructed, wherein the number of horizontal gridding points Nx and the number of vertical gridding points Ny should satisfy:

[0013]

[0014] Among them, Θ is the aperture angle of the near-field scattering characteristic data relative to the target, f is the highest frequency of the test data, B is the bandwidth corresponding to the test data, and c0 represents the speed of light in vacuum.

[0015] Preferably, construct the near-field measurement matrix A N In the step, the near-field observation matrix A N It is expressed as:

[0016]

[0017] in, Represents the near-field observation matrix A N The (m,n)th element of R m,n Indicates the distance from the mth point in the target area to the test antenna in the nth test state, with the test antenna position as the origin of the coordinate system; x m,n With y m,n represents the coordinates of the mth point; f n is the frequency corresponding to the nth test state.

[0018] Preferably, the far-field reconstruction matrix A is constructed F In the step, the far-field reconstruction matrix A F It is expressed as:

[0019]

[0020] in, Denotes the far-field reconstruction matrix A F The (k,j)th element of R k,,j It represents the distance from the jth point in the target area to the origin of the coordinate system under the kth test state, with the center of the target area as the origin of the coordinate system. j With y j represents the coordinates of the jth point; f k With θ kare the frequency and angle corresponding to the kth test state.

[0021] Preferably, based on the near-field observation matrix A N and the far-field reconstruction matrix A F In the step of constructing the transfer matrix A, the transfer matrix A is expressed as:

[0022] A=A F ·A N .

[0023] Preferably, in the step of realizing the mapping of the near-field scattering characteristic data of the target to the far-field scattering characteristic data by transferring the matrix A, S F =A·S N ; Among them, S N is the near-field scattering characteristic data of the target, S F It is the far-field scattering characteristic data of the target.

[0024] The present invention also provides a near-field and far-field data conversion device based on a transfer matrix, comprising: a first calculation module, the first calculation module is used to calculate the minimum synthetic aperture angle Φ required for near-field and far-field data conversion; a grid processing module, the grid processing module is used to perform grid processing on the target area; a near-field observation matrix construction module, the near-field observation matrix construction module is used to construct a near-field observation matrix A N , near-field observation matrix A N Realize the mapping of near-field scattering characteristic data to the target scattering center; far-field reconstruction matrix construction module, the far-field reconstruction matrix construction module is used to construct the far-field reconstruction matrix A F , the far-field reconstruction matrix A F Realize the mapping of target scattering center to far-field scattering characteristic data; transfer matrix construction module, the transfer matrix construction module is used to N and the far-field reconstruction matrix A F Constructing a transfer matrix A; a second calculation module, the second calculation module is used to realize the mapping of the near-field scattering characteristic data of the target to the far-field scattering characteristic data through the transfer matrix A.

[0025] Preferably, the near-field measurement matrix construction module constructs the near-field measurement matrix A N During the process, the near-field observation matrix A N It is expressed as:

[0026]

[0027] in, Represents the near-field observation matrix A N The (m,n)th element of R m,n Indicates the distance from the mth point in the target area to the test antenna in the nth test state, with the test antenna position as the origin of the coordinate system; xm,n With y m,n represents the coordinates of the mth point; f n is the frequency corresponding to the nth test state;

[0028] The far-field reconstruction matrix construction module constructs the far-field reconstruction matrix A F In the step, the far-field reconstruction matrix A F It is expressed as:

[0029]

[0030] in, Denotes the far-field reconstruction matrix A F The (k,j)th element of R k,,j It represents the distance from the jth point in the target area to the origin of the coordinate system under the kth test state, with the center of the target area as the origin of the coordinate system. j With y j represents the coordinates of the jth point; f k With θ k are the frequency and angle corresponding to the kth test state.

[0031] The implementation of the near-field and far-field data transformation method and device based on the transfer matrix of the present invention has the following beneficial effects: with the help of the transfer matrix concept, a mapping relationship between the near-field and far-field scattering characteristics of the target is directly established, and the target near-field scattering characteristic data can be quickly and accurately transformed to the far field. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of a near-field and far-field data transformation method based on a transfer matrix according to an embodiment of the present invention;

[0033] Figure 2 This is a comparison chart of the Pershing warhead near-field scattering calculation data, far-field theoretical data and far-field transformation calculation data. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Figure 1 is a flow chart of a near-field and far-field data transformation method based on a transfer matrix according to an embodiment of the present invention; Figure 1As shown, the near-field and far-field data transformation method based on the transfer matrix provided in the embodiment of the present invention comprises the following steps: Step S01: calculating the minimum synthetic aperture angle Φ required for the near-field and far-field data transformation; Step S02: performing grid processing on the target area; Step S03: constructing the near-field observation matrix A N , near-field observation matrix A N Realize the mapping of near-field scattering characteristic data to the target scattering center; Step S04: Construct the far-field reconstruction matrix A F , the far-field reconstruction matrix A F Realize the mapping of the target scattering center to the far-field scattering characteristic data; Step S05: Based on the near-field observation matrix A N and the far-field reconstruction matrix A F Constructing a transfer matrix A; Step S06: Mapping the near-field scattering characteristic data of the target to the far-field scattering characteristic data through the transfer matrix A.

[0036] In the near-field and far-field data transformation method based on the transfer matrix provided in the embodiment of the present invention, the minimum synthetic aperture angle Φ means that for a specific azimuth angle Φ0, the azimuth angle range of the near-field test is [Φ0-Φ, Φ0+Φ]. In the step of calculating the minimum synthetic aperture angle Φ required for the near-field and far-field data transformation, the minimum synthetic aperture angle Φ is expressed as:

[0037]

[0038] Wherein, R is the test distance, i.e. the distance between the antenna and the target; D is the maximum horizontal size of the target, i.e. the maximum linear size of the target.

[0039] The present invention relates to the field of RCS test and data processing technology, in particular to a data transformation method for extrapolating electromagnetic scattering test data under near-field conditions to far-field conditions. The method is based on the premise that the distribution of target scattering centers remains unchanged under near-field and far-field conditions. According to the maximum linear dimension of the target and the distance between the antenna and the target, the minimum synthetic aperture angle Φ required for extrapolating far-field data is calculated; according to the test scene parameters, the radar system parameters and Φ, an observation matrix A under near-field test conditions is constructed. N , to achieve the mapping from the target frequency domain near-field scattering characteristics to the scattering center; construct and A N The corresponding far-field reconstruction matrix A F , to achieve the mapping from the target scattering center to the frequency domain far-field scattering characteristics (RCS); using A N With A FConstruct a transfer matrix A to achieve the mapping from the target frequency domain near-field scattering characteristics to RCS; perform convolution operation on A and the target near-field characteristic data to obtain the target RCS under far-field conditions. With the help of the transfer matrix concept, the present invention directly establishes the mapping relationship between the target near-field and far-field scattering characteristics. With the help of the scattering center concept, the target near-field scattering characteristic data can be quickly and accurately transformed to the far field without the need for imaging processing during the processing; the function of mutual conversion between the target RCS and the near-field scattering characteristic data at any distance can be achieved by changing the form of the observation matrix and the reconstruction matrix.

[0040] Figure 2 It is a comparison chart of the near-field scattering calculation data, far-field theoretical data and far-field transformation calculation data of the Pershing warhead. It can be seen that the near-field and far-field data transformation method based on the transfer matrix of the present invention has a higher near-field and far-field transformation accuracy.

[0041] In the near-field and far-field data transformation method based on the transfer matrix provided in the embodiment of the present invention, in the step of gridding the target area, the gridding area is centered on the center of the target area, and a region with a horizontal length and a vertical length of D is constructed, wherein the horizontal gridding point number Nx and the vertical gridding point number Ny should satisfy:

[0042]

[0043] Among them, Θ is the aperture angle of the near-field scattering characteristic data relative to the target, f is the highest frequency of the test data, B is the bandwidth corresponding to the test data, and c0 represents the speed of light in vacuum.

[0044] The near-field and far-field data transformation method based on the transfer matrix provided in the embodiment of the present invention constructs the near-field measurement matrix A N In the step, the near-field observation matrix A N It is expressed as:

[0045]

[0046] in, Represents the near-field observation matrix A N The (m,n)th element of R m,n Indicates the distance from the mth point in the target area to the test antenna in the nth test state, with the test antenna position as the origin of the coordinate system; x m,n With y m,n represents the coordinates of the mth point; f n is the frequency corresponding to the nth test state.

[0047] The near-field and far-field data transformation method based on the transfer matrix provided in the embodiment of the present invention constructs the far-field reconstruction matrix A F In the step, the far-field reconstruction matrix A F It is expressed as:

[0048]

[0049] in, Denotes the far-field reconstruction matrix A F The (k,j)th element of R k,,j It represents the distance from the jth point in the target area to the origin of the coordinate system under the kth test state, with the center of the target area as the origin of the coordinate system. j With y j represents the coordinates of the jth point; f k With θ k are the frequency and angle corresponding to the kth test state.

[0050] The near-field and far-field data conversion method based on the transfer matrix provided in the embodiment of the present invention is based on the near-field observation matrix A N and the far-field reconstruction matrix A F In the step of constructing the transfer matrix A, the transfer matrix A is expressed as:

[0051] A=A F ·A N .

[0052] In the near-field and far-field data conversion method based on the transfer matrix provided in the embodiment of the present invention, in the step of realizing the mapping of the near-field scattering characteristic data of the target to the far-field scattering characteristic data through the transfer matrix A, S F =A·S N ; Among them, S N is the near-field scattering characteristic data of the target, S F It is the far-field scattering characteristic data of the target.

[0053] The embodiment of the present invention also provides a near-field and far-field data conversion device based on a transfer matrix, the device comprising: a first calculation module, the first calculation module is used to calculate the minimum synthetic aperture angle Φ required for the near-field and far-field data conversion; a grid processing module, the grid processing module is used to perform grid processing on the target area; a near-field observation matrix construction module, the near-field observation matrix construction module is used to construct a near-field observation matrix A N , near-field observation matrix A N Realize the mapping of near-field scattering characteristic data to the target scattering center; far-field reconstruction matrix construction module, the far-field reconstruction matrix construction module is used to construct the far-field reconstruction matrix A F , the far-field reconstruction matrix A F Realize the mapping of target scattering center to far-field scattering characteristic data; transfer matrix construction module, the transfer matrix construction module is used to N and the far-field reconstruction matrix A FConstructing a transfer matrix A; a second calculation module, the second calculation module is used to realize the mapping of the near-field scattering characteristic data of the target to the far-field scattering characteristic data through the transfer matrix A.

[0054] In the near-field and far-field data conversion device based on the transfer matrix provided by the embodiment of the present invention, in the process in which the first calculation module calculates the minimum synthetic aperture angle Φ required for the near-field and far-field data conversion, the meaning of the minimum synthetic aperture angle Φ is that for a specific azimuth angle Φ0, the minimum value of the azimuth angle area of ​​the near-field test should be less than or equal to Φ0-Φ / 2, and the maximum value of the azimuth angle area of ​​the near-field test should be greater than or equal to Φ0+Φ / 2. In the step of calculating the minimum synthetic aperture angle Φ required for the near-field and far-field data conversion, the minimum synthetic aperture angle Φ is expressed as:

[0055]

[0056] Where R is the test distance and D is the maximum horizontal size of the target.

[0057] In the near-field and far-field data conversion device based on the transfer matrix provided by the embodiment of the present invention, during the process of the grid processing module performing grid processing on the target area, the grid area is centered on the center of the target area, and a region with a horizontal length and a vertical length of D is constructed, wherein the horizontal grid point number Nx and the vertical grid point number Ny should satisfy:

[0058]

[0059] Among them, Θ is the aperture angle of the near-field scattering characteristic data relative to the target, f is the highest frequency of the test data, B is the bandwidth corresponding to the test data, and c0 represents the speed of light in vacuum.

[0060] The near-field and far-field data conversion device based on the transfer matrix provided in the embodiment of the present invention, the near-field measurement matrix construction module constructs the near-field measurement matrix A N During the process, the near-field observation matrix A N It is expressed as:

[0061]

[0062] in, Represents the near-field observation matrix A N The (m,n)th element of R m,n Indicates the distance from the mth point in the target area to the test antenna in the nth test state, with the test antenna position as the origin of the coordinate system; x m,n With y m,n represents the coordinates of the mth point; f n is the frequency corresponding to the nth test state.

[0063] The near-field and far-field data conversion device based on the transfer matrix provided in the embodiment of the present invention, the far-field reconstruction matrix construction module constructs the far-field reconstruction matrix A F In the process, the far-field reconstruction matrix A F It is expressed as:

[0064]

[0065] in, Denotes the far-field reconstruction matrix A F The (k,j)th element of R k,,j It represents the distance from the jth point in the target area to the origin of the coordinate system under the kth test state, with the center of the target area as the origin of the coordinate system. j With y j represents the coordinates of the jth point; f k With θ k are the frequency and angle corresponding to the kth test state.

[0066] The near-field and far-field data conversion device based on the transfer matrix provided in the embodiment of the present invention, the transfer matrix construction module is based on the near-field observation matrix A N and the far-field reconstruction matrix A F In the process of constructing the transfer matrix A, the transfer matrix A is expressed as: A = A F ·A N .

[0067] In the near-field and far-field data conversion device based on the transfer matrix provided in the embodiment of the present invention, the second calculation module realizes the mapping process of the near-field scattering characteristic data of the target to the far-field scattering characteristic data through the transfer matrix A. F =A·S N ; Among them, S N is the near-field scattering characteristic data of the target, S F It is the far-field scattering characteristic data of the target.

[0068] In summary, the implementation of the near-field and far-field data conversion device based on the transfer matrix of the present invention has the following beneficial effects: based on the principle of invariance of the scattering distribution function, an improved target near-field / far-field data conversion method with a simple form, easy implementation and strong versatility is provided to solve the problem of converting the target near-field scattering characteristics to the far-field RCS in actual engineering tests.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A near-field and far-field data transformation method based on transfer matrix, characterized in that: The steps include: Calculate the minimum synthetic aperture angle Φ required for near-field and far-field data transformation; Gridding the target area; Construct the near-field measurement matrix A N , the near-field observation matrix A N Realize the mapping of near-field scattering characteristic data to target scattering center; Construct the far-field reconstruction matrix A F , the far-field reconstruction matrix A F Realize the mapping of target scattering center to far-field scattering characteristic data; Based on the near-field measurement matrix A N With the far-field reconstruction matrix A F Construct transfer matrix A; The transfer matrix A is used to map the near-field scattering characteristic data of the target to the far-field scattering characteristic data.

2. The near-field and far-field data transformation method based on transfer matrix according to claim 1, characterized in that: The meaning of the minimum synthetic aperture angle Φ is that, for a specific azimuth angle Φ0, the minimum value of the azimuth angle area of ​​the near-field test should be less than or equal to Φ0-Φ / 2, and the maximum value of the azimuth angle area of ​​the near-field test should be greater than or equal to Φ0+Φ / 2.

3. The near-field and far-field data transformation method based on transfer matrix according to claim 2, characterized in that: In the step of calculating the minimum synthetic aperture angle Φ required for near-field and far-field data transformation, the minimum synthetic aperture angle Φ is expressed as: Where R is the test distance and D is the maximum horizontal size of the target.

4. The near-field and far-field data transformation method based on transfer matrix according to claim 1, characterized in that: In the step of gridding the target area, the gridding area is centered on the center of the target area, and a region with a horizontal length and a vertical length of D is constructed, wherein the number of horizontal grid points Nx and the number of vertical grid points Ny should satisfy: Among them, Θ is the aperture angle of the near-field scattering characteristic data relative to the target, f is the highest frequency of the test data, B is the bandwidth corresponding to the test data, and c0 represents the speed of light in vacuum.

5. The near-field and far-field data transformation method based on transfer matrix according to claim 1, characterized in that: The near-field measurement matrix A is constructed N In the step, the near-field measurement matrix A N It is expressed as: in, Denotes the near-field measurement matrix A N The (m,n)th element of R m,n Indicates the distance from the mth point in the target area to the test antenna in the nth test state, with the test antenna position as the origin of the coordinate system; x m,n With y m,n represents the coordinates of the mth point; f n is the frequency corresponding to the nth test state.

6. The near-field and far-field data transformation method based on transfer matrix according to claim 1, characterized in that: The far-field reconstruction matrix A is constructed F In the step, the far-field reconstruction matrix A F It is expressed as: in, Denotes the far-field reconstruction matrix A F The (k,j)th element of R k,j It represents the distance from the jth point in the target area to the origin of the coordinate system under the kth test state, with the center of the target area as the origin of the coordinate system. j With y j represents the coordinates of the jth point; f k With θ k are the frequency and angle corresponding to the kth test state.

7. The near-field and far-field data transformation method based on transfer matrix according to claim 1, characterized in that: The near-field measurement matrix A N With the far-field reconstruction matrix A F In the step of constructing a transfer matrix A, the transfer matrix A is expressed as: A=A F ·A N 。 8. The near-field and far-field data transformation method based on transfer matrix according to any one of claims 1 to 7, characterized in that: In the step of realizing the mapping of the near-field scattering characteristic data of the target to the far-field scattering characteristic data through the transfer matrix A, S F =A·S N ; Among them, S N is the near-field scattering characteristic data of the target, S F It is the far-field scattering characteristic data of the target.

9. A near-field and far-field data conversion device based on a transfer matrix, characterized in that: include: A first calculation module, the first calculation module is used to calculate the minimum synthetic aperture angle Φ required for near-field and far-field data transformation; A grid processing module, wherein the grid processing module is used to perform grid processing on the target area; A near-field measurement matrix construction module, wherein the near-field measurement matrix construction module is used to construct a near-field measurement matrix A N , the near-field observation matrix A N Realize the mapping of near-field scattering characteristic data to target scattering center; A far-field reconstruction matrix construction module, wherein the far-field reconstruction matrix construction module is used to construct a far-field reconstruction matrix A F , the far-field reconstruction matrix A F Realize the mapping of target scattering center to far-field scattering characteristic data; A transfer matrix construction module, wherein the transfer matrix construction module is used to construct a matrix based on the near-field observation matrix A. N With the far-field reconstruction matrix A F Construct transfer matrix A; A second calculation module, wherein the second calculation module is used to realize the mapping of the near-field scattering characteristic data of the target to the far-field scattering characteristic data through the transfer matrix A.

10. The near-field and far-field data conversion device based on transfer matrix according to claim 9, characterized in that: The near-field measurement matrix construction module constructs the near-field measurement matrix A N During the process, the near-field observation matrix A N It is expressed as: in, Denotes the near-field measurement matrix A N The (m,n)th element of R m,n Indicates the distance from the mth point in the target area to the test antenna in the nth test state, with the test antenna position as the origin of the coordinate system; x m,n With y m,n represents the coordinates of the mth point; f n is the frequency corresponding to the nth test state; The far-field reconstruction matrix construction module constructs the far-field reconstruction matrix A F In the step, the far-field reconstruction matrix A F It is expressed as: in, Denotes the far-field reconstruction matrix A F The (k,j)th element of R k,j It represents the distance from the jth point in the target area to the origin of the coordinate system under the kth test state, with the center of the target area as the origin of the coordinate system. j With y j represents the coordinates of the jth point; f k With θ k are the frequency and angle corresponding to the kth test state.

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