Method for reconstructing image by improving two-dimensional mirror image synthetic aperture through metamaterial and medium

Abstract

The invention relates to a method for reconstructing an image by improving a two-dimensional mirror image synthetic aperture through a metamaterial and a medium, and the method comprises the steps: configuring a two-dimensional mirror image synthetic aperture system which comprises a two-dimensional antenna array and two groups of reflection structures which are perpendicular to each other; two groups of mutually perpendicular reflection structures are replaced by magnetic conductor structures, and the magnetic conductor structures have in-phase reflection characteristics in a target frequency band; according to the position coordinates of the antennas in the two-dimensional antenna array and the in-phase reflection characteristic of the magnetic conductor structure, correlation values between the antenna pairs are calculated; constructing a transfer matrix according to the calculated correlation values; establishing a system of linear equations through the transfer matrix and the cosine visibility function, and solving the system of linear equations to obtain cosine visibility; and performing anti-cosine transform on the cosine visibility, and reconstructing a brightness temperature image of the target scene. According to the method, the negative interference of the transfer matrix is effectively eliminated through the electromagnetic regulation and control characteristics of the artificial magnetic conductor, and the optimization of the rank defect error is realized.

Description

Technical Field

[0001] The present invention relates to the field of microwave radiation imaging, and in particular to a method and medium for reconstructing an image by improving a two-dimensional mirror synthetic aperture using a metamaterial. Background Art

[0002] In the field of microwave radiation imaging, the two-dimensional mirror aperture synthesis technology achieves high-resolution imaging with a smaller number of antennas by constructing a many-to-one mapping relationship between antenna correlation values and cosine visibility, significantly reducing system complexity. This technology relies on the reflection of the incident signal by the metal reflector, and forms the interference information required for the synthetic aperture by receiving the direct signal and its reflected signal on the reflector. However, in the existing technology, the phase-inversion characteristics of the metal reflector lead to the presence of negative elements (such as "-1") in the transfer matrix, causing the matrix rank deficiency problem, which seriously restricts the quality of the reconstructed image. Although some studies have attempted to reduce the rank deficiency error through methods such as dual-polarization joint or reflector joint testing, these schemes not only increase the computational complexity, but also fail to completely eliminate the matrix rank deficiency, making it difficult to achieve the full rank state of the transfer matrix, thereby limiting further improvement of imaging accuracy. Summary of the Invention

[0003] The present invention provides a method and medium for reconstructing images using a metamaterial-improved two-dimensional mirror synthesis aperture. The purpose is to solve the rank deficiency problem caused by negative elements in the transfer matrix caused by the metal reflector in the traditional two-dimensional mirror synthesis aperture, which leads to large errors in solving underdetermined equations and low imaging quality.

[0004] To achieve the above objectives, the present invention provides a method for reconstructing an image using a metamaterial-improved two-dimensional mirror synthetic aperture, comprising the following steps: Configuring a two-dimensional mirror-image synthetic aperture system, wherein the two-dimensional mirror-image synthetic aperture system includes a two-dimensional antenna array and two sets of mutually perpendicular reflective structures; Replacing the two sets of mutually perpendicular reflection structures with a magnetic conductor structure, wherein the magnetic conductor structure has an in-phase reflection characteristic within a target frequency band; Calculating correlation values between antenna pairs based on the position coordinates of the antennas in the two-dimensional antenna array and the in-phase reflection characteristics of the magnetic conductor structure; Constructing a transfer matrix according to the calculated correlation values, wherein the non-zero elements of the transfer matrix are positive values; Establishing a linear equation system by using the transfer matrix and the cosine visibility function, and solving the linear equation system to obtain the cosine visibility; An inverse cosine transform is performed on the cosine visibility to reconstruct a brightness temperature image of the target scene.

[0005] Furthermore, the magnetic conductor structure includes a cross-shaped upper metal pattern, an intermediate dielectric layer and a bottom metal plate.

[0006] Furthermore, the material of the intermediate dielectric layer is FR4, with a dielectric constant of 4.3 and a loss tangent of 0.0025.

[0007] Furthermore, the in-phase reflection characteristic frequency bands of the magnetic conductor structure are: 5.47-8.25 GHz and 15.13-16.07 GHz; and the reflection phase is in the range of -90° to +90°.

[0008] Furthermore, calculating the correlation value between each antenna includes: For any two antennas and , the correlation value Determined by the sum of the following four cosine visibility terms: in, 、 and 、 Antenna and The coordinates of is the wavelength, Represents the two-dimensional cosine visibility function.

[0009] Furthermore, the construction of the transfer matrix includes: Represent each correlation value as a linear combination of multiple cosine visibilities; The matrix elements are formed by the coefficients of the linear combination, and the coefficients are all positive.

[0010] Furthermore, the method for establishing the linear equation system includes: Arranging the correlation values into a correlation value matrix in vector form according to antenna pairs; Determine each element of the transfer matrix according to the position coordinates of the antenna pair, wherein each element corresponds to a cosine visibility coefficient of a different spatial frequency combination, and the cosine visibility coefficients are all +1; Representing the cosine visibility function as a cosine visibility matrix in vector form; By multiplying the transfer matrix, the cosine visibility matrix, and the correlation value matrix, a linear equation system is constructed: in, represents the correlation value matrix, represents the transfer matrix, Represents the cosine visibility matrix.

[0011] Furthermore, the solution of the linear equations is achieved by least squares method or matrix inversion.

[0012] Furthermore, the brightness temperature reconstruction formula of the inverse cosine transform is: in, is the brightness temperature distribution of the target scene, which represents the brightness temperature of the reconstructed image. Hewei The minimum spacing of spatial frequencies corresponds to the antenna array in the horizontal direction and vertical direction The wavelength-normalized value of the minimum antenna spacing, and Represents the spatial frequency in the horizontal direction and vertical direction The total number of sampling points, is a two-dimensional cosine visibility function, which represents the spatial frequency point The visibility value obtained by measurement or calculation, is the weight coefficient, and is the direction cosine, and is the cosine basis function, which is used to convert the cosine visibility in the frequency domain back to the brightness temperature distribution in the spatial domain.

[0013] To achieve the above-mentioned objectives, the second aspect of the present invention provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for reconstructing an image by using a metamaterial-improved two-dimensional mirror synthetic aperture are executed.

[0014] Beneficial effects of the present invention: Compared with the existing technology, the present invention provides a method and medium for improving two-dimensional mirror synthetic aperture image reconstruction using metamaterials. To address the transfer matrix rank deficiency problem introduced by traditional metal reflectors, an artificial magnetic conductor (AMC) is designed to replace the metal reflector. Its in-phase reflection characteristics are used to eliminate the negative elements in the transfer matrix, thereby improving the matrix rank and reducing the root mean square error (RMSE) of the reconstructed image. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0016] Figure 1 This is a two-dimensional mirror synthetic aperture principle diagram disclosed in an embodiment of the present invention.

[0017] Figure 2 This is a flow chart of a method for reconstructing an image using a metamaterial-improved two-dimensional mirror synthetic aperture disclosed in an embodiment of the present invention.

[0018] Figure 3 This is a structural diagram of an artificial magnetic conductor for a two-dimensional mirror-image integrated aperture disclosed in an embodiment of the present invention, wherein (a) is a schematic diagram of an electromagnetic wave incident AMC disclosed in an embodiment of the present invention, and (b) is a structural diagram of an AMC unit disclosed in an embodiment of the present invention.

[0019] Figure 4 3 is a reflection phase curve diagram of an artificial magnetic conductor structure disclosed in an embodiment of the present invention, wherein (a) is a reflection phase variation curve diagram of a cross-type AMC structure in TE and TM polarization modes disclosed in an embodiment of the present invention, and (b) is a diagram of the influence of the incident angle on the reflection phase disclosed in an embodiment of the present invention.

[0020] Figure 5 : This is an antenna arrangement diagram disclosed in an embodiment of the present invention, wherein (a) is a single "L" array arrangement diagram disclosed in an embodiment of the present invention, (b) is a half-full array arrangement diagram disclosed in an embodiment of the present invention, and (c) is a full array arrangement diagram disclosed in an embodiment of the present invention.

[0021] Figure 6 It shows the traditional transfer matrix under different numbers of antennas P 1 With the improved matrix P 2 Rank and rank deficiency comparison chart of , where (a) is the matrix P 1 、 P 2 rank and rank deficiency comparison diagram, (b) is the original scene diagram.

[0022] Figure 7 This is a different antenna arrangement disclosed in an embodiment of the present invention. P 1 and P 2 The reconstructed image diagram, wherein (a) is a single "L" array disclosed in an embodiment of the present invention. P 1 Reconstructed image, (b) is a half-full array disclosed in an embodiment of the present invention P 1 Reconstructed image, (c) is a full array disclosed in an embodiment of the present invention P 1 Reconstructed image, (d) is a single "L" array disclosed in an embodiment of the present invention P 2 Reconstructed image, (e) is a half-full array disclosed in an embodiment of the present invention P 2 Reconstructed image, (f) is a full array disclosed in an embodiment of the present inventionP 2 Reconstruct the image. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions 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 embodiments described are only 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 making creative efforts should fall within the scope of protection of the present invention.

[0024] According to an embodiment of the present invention, it should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the following production method, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0025] like Figure 1 As shown in Figure 1, a traditional 2D mirror aperture synthesis system consists of a 2D antenna array and two mutually perpendicular reflectors. Each antenna in the array receives four types of signals from the radiation source: a direct incident signal, a single reflection from the reflector (XOY), a single reflection from the reflector (YOZ), and a double reflection from the dual reflectors.

[0026] Since brightness temperature and cosine visibility are cosine transform pairs, the brightness temperature image can be reconstructed by inverse cosine transform. The process of reconstructing the brightness temperature image using the mirror synthetic aperture is as follows: First, the antenna array receives the direct and reflected signals from the reflector. After a series of signal processing, the correlation value can be obtained. .

[0027] Represents the correlation output between any two antennas. Different antenna polarizations will lead to different correlation operation results.

[0028] When the antenna polarization is parallel to the YOZ, the antenna related value is: (1) When the antenna polarization is parallel to the XOZ, the antenna related value is: (2) in, 、 and 、 Antenna and The coordinates of is the wavelength, Represents the two-dimensional cosine visibility function.

[0029] Since each correlation value can be expressed as a linear operation of multiple cosine visibility, the linear equation system of cosine visibility and correlation value is obtained: (3) in, represents the correlation value matrix, represents the transfer matrix, Represent the cosine visibility matrix: (4) in, represents the two-dimensional cosine visibility function, and are direction cosines, respectively expressed as: ,in is the polar angle (the angle with the vertical), is the azimuth (rotation angle in the horizontal plane); is the original brightness temperature distribution of the scene, representing the brightness temperature of radiation sources in different directions (in Kelvin, K), is the wavelength-normalized spatial frequency, and is the cosine basis function, which is used to convert the cosine visibility in the frequency domain back to the brightness temperature distribution in the spatial domain. Represents the direction cosine The two-dimensional differential element of Represents the direction cosine Two-dimensional differential element.

[0030] Finally, the linear equations are solved to obtain the cosine visibility, and the brightness temperature image can be reconstructed through inverse cosine transform.

[0031] (5) in, is the brightness temperature distribution of the target scene, which represents the brightness temperature of the reconstructed image. Hewei The minimum spacing of spatial frequencies corresponds to the antenna array in the horizontal direction and vertical direction The wavelength-normalized value of the minimum antenna spacing, and Represents the spatial frequency in the horizontal direction and vertical direction The total number of sampling points, is a two-dimensional cosine visibility function, which represents the spatial frequency point The visibility value obtained by measurement or calculation, is the weight coefficient, and is the direction cosine, and is the cosine basis function, which is used to convert the cosine visibility in the frequency domain back to the brightness temperature distribution in the spatial domain.

[0032] for: (6) The following will be combined Figure 2 The present invention provides a method for improving a two-dimensional mirror image synthesis aperture reconstruction method using a metamaterial, which includes: Step S100: configuring a two-dimensional mirror-image synthetic aperture system, wherein the two-dimensional mirror-image synthetic aperture system includes a two-dimensional antenna array and two sets of mutually perpendicular reflective structures; Step S200: replacing the two groups of mutually perpendicular reflection structures with a magnetic conductor structure, wherein the magnetic conductor structure has an in-phase reflection characteristic within a target frequency band; Step S300: Calculating correlation values between antenna pairs based on the position coordinates of the antennas in the two-dimensional antenna array and the in-phase reflection characteristics of the magnetic conductor structure; Step S400: constructing a transfer matrix according to the calculated correlation values, wherein the non-zero elements of the transfer matrix are positive values; Step S500: establishing a linear equation system using the transfer matrix and the cosine visibility function, and solving the linear equation system to obtain cosine visibility; Step S600: Perform inverse cosine transform on the cosine visibility to reconstruct a brightness temperature image of the target scene.

[0033] As described in step S100 above, the configured two-dimensional mirror aperture synthesis system is composed of a two-dimensional antenna array and two sets of mutually perpendicular reflection structures (XOY and YOZ plane reflection plates). Figure 1 As shown, the antenna array is distributed in a specific arrangement (such as a single "L" array, a half-filled array, or a full array), and its minimum antenna spacing is normalized by wavelength and defined as and , which is used to cover the spatial frequency range of the target frequency band. Each set of reflection structures is perpendicular to the x and y directions of the antenna array, forming a mirror reflection surface. By receiving the direct signal from the radiation source and the single or secondary reflection signal from the reflector (a total of four signal paths), the interference effect between the antennas is used to generate correlation values, thereby establishing a mapping relationship with the cosine visibility. This configuration expands the equivalent aperture through physical reflection, significantly reducing the number of actual antennas while retaining high-resolution imaging capabilities. However, the geometric arrangement of the reflection structure directly affects the signal phase relationship. Traditional metal reflectors will introduce phase inversion, resulting in negative elements (such as "-1") in the transfer matrix.

[0034] As described in step S200 above, the metal reflector in the traditional two-dimensional mirror aperture synthesis system is replaced with an artificial magnetic conductor (AMC) structure to optimize the signal phase relationship by utilizing its in-phase reflection characteristics. Figure 3 (a) and Figure 3 As shown in (b), the designed AMC unit adopts a cross-shaped upper metal pattern, and the middle dielectric layer is made of FR4 material (dielectric constant =4.3, tangent loss is 0.0025), the bottom layer is a metal plate. Specific structural parameters include: cross arm length 、 , unit cycle , dielectric layer thickness The structure ensures consistent reflection phase characteristics in TE and TM polarization modes through symmetrical design, and achieves broadband in-phase reflection characteristics by adjusting the cross arm length and unit period.

[0035] To verify the electromagnetic performance of AMC, the Floquet port method in CST electromagnetic simulation software is used to perform frequency domain analysis. The reflection phase of the AMC structure is as follows: Figure 4 As shown in (a), the reflection phase variation curves of the TE and TM polarization modes overlap, indicating that the curves of the two modes are the same. The simulation results show that the reflection phase of the AMC structure is close to 0° in the 5.47-8.25 GHz (low frequency band) and 15.13-16.07 GHz (high frequency band), forming two stable in-phase reflection band gaps, and the reflection phase is strictly zero at the center frequencies of 6.87 GHz and 15.57 GHz. Compared with traditional metal reflectors (the reflection phase is always 180°), the in-phase reflection characteristics of the AMC avoid the phase reversal between the incident wave and the reflected wave, thereby eliminating the negative elements (such as "-1") in the transfer matrix. In addition, as Figure 4 As shown in (b), the structure can still maintain the stability of the same and opposite RF bands when the incident angle changes, indicating that it has good angle adaptability in practical applications.

[0036] It should be noted that artificial magnetic conductors (AMCs), as a typical electromagnetic metamaterial structure, possess unique in-phase reflection properties. Replacing the metal reflector in a synthetic aperture with an AMC converts the "-1" in the transfer matrix to a "1," thereby increasing the matrix rank. The AMC's reflection phase can continuously vary from 180° to -180° within a certain frequency band, reaching zero at a certain frequency. The following analyzes the in-phase reflection properties of AMCs from the perspective of surface impedance.

[0037] like Figure 3 As shown in (a), the incident wave enters the AMC surface along the -x direction. At this time, the AMC surface impedance is: (7) in, It represents the surface impedance of the artificial magnetic conductor (AMC) (unit: Ω), reflecting the surface response characteristics of the AMC to electromagnetic waves. represents the component of the electric field in the direction perpendicular to the AMC surface (z direction) (unit: V / m), It represents the component of the magnetic field parallel to the AMC surface (y direction) (unit: A / m).

[0038] When electromagnetic waves are incident on the surface of the AMC structure, the incident waves will be reflected on the surface of the structure, and a standing wave composed of the incident waves and the reflected waves will be formed above the AMC structure. , the reflected wave is , then the electric field and magnetic field above the structure are: (8) (9) in, represents the electric field above the structure, represents the magnetic field above the structure, and represents the electric and magnetic field complex amplitudes of the incident wave, and represents the complex amplitudes of the electric and magnetic fields of the reflected wave, is the base of natural logarithms, is an imaginary unit, represents the wave number, represents the position coordinate along the propagation direction of the electromagnetic wave, Indicates the electromagnetic wave Phase change in directional propagation (reflected wave component), Indicates the electromagnetic wave Phase change in the direction of propagation (incident wave component).

[0039] exist At , the surface impedance can be obtained from the boundary conditions: (10) Free space wave impedance satisfy: (11) in, and Indicates that the incident wave is at position The complex amplitudes of the electric and magnetic fields at ; and Indicates that the reflected wave is at position The complex amplitudes of the electric and magnetic fields at .

[0040] Combining equations (7)-(11), the phase difference between the incident wave and the reflected wave in the space above the structure can be obtained as for: (12) According to formula (12), when the surface impedance Much smaller than the free space wave impedance When the reflected wave phase is opposite to the incident wave phase, the reflected phase is about ±180°, which means it has ideal electrical surface characteristics. Much larger than the free space wave impedance When the phase of the reflected wave is almost in the same direction as the incident wave, the reflected phase is approximately 0°, which indicates a co-directional reflection characteristic. The reflection phase band of -90° to +90° is defined as the co-directional reflection band gap of AMC.

[0041] As described in step S300 above, after replacing the traditional metal reflector, the introduction of AMC directly changes the calculation model of the antenna correlation value. In the traditional system, the metal reflector causes the phase of the signal to flip when it is reflected, and the correlation value expression contains alternating positive and negative terms (such as equations (1) and (2)); this is because the incident signal will inevitably be inverted when passing through the metal reflector, resulting in the transfer matrix P A non-zero element "-1" appears in . "-1" will make P This can further increase the rank deficiency, ultimately leading to lower quality in the reconstructed brightness temperature image. This phenomenon occurs because the rank deficiency causes the transfer equation to be underdetermined, resulting in an infinite number of solutions. This requires a special method to specify the solution, namely, cosine visibility. However, this cosine visibility does not fully conform to the ideal cosine visibility, resulting in significant errors in the reconstructed image.

[0042] After adopting AMC, the reflected signal is in phase with the incident signal, and all items in the correlation value calculation formula (Equation (13)) are positive values, as follows: (13) in, 、 and 、 Antenna and The coordinates of is the wavelength, Represents the two-dimensional cosine visibility function.

[0043] This property makes the transfer matrix All non-zero elements of are "1", which significantly reduces the rank deficiency error of the matrix, as shown in formula (14): (14) in, For rank deficiency, is the number of cosine visibility, is a matrix rank.

[0044] The following tests verify this conclusion. First, a single antenna with 10 antennas in both x and y directions is used. Antenna array, wavelength normalized antenna minimum spacing , are all 1.5, and the array coordinates are (1, 1). "An antenna is added one at a time on the basis of the array until a two-dimensional full array antenna array is formed. There are a total of 82 antenna arrangements. Figure 5 For antenna arrangement, Figure 5 (a) is a single " "Array, Figure 5 (b) is a half-full array, Figure 5 (c) is a full array. The transfer matrix in the linear equation system is composed of equations (1) and (13). P To calculate the rank and rank deficiency of each antenna array, in formula (1) P There are 4 non-zero elements in each row of , which are "1, -1, 1, -1". This matrix is called P1. P There are 4 non-zero elements in each row that are all "1", and the matrix is called P 2 .exist Figure 6 (a) It can be found P 2 The rank is greater than P 1 , P 2 The rank deficiency is less than P 1 , as the number of antennas increases ，P 2 The rank of increases and gradually increases to full rank, and P 1 Although the rank of increases with the increase in the number of antennas, it is difficult to increase to the full rank, and there is always a rank deficiency.

[0045] Further, Figure 6 (b) The original scene is the target pair " "Array, half full array (single " "Array adds 40 antennas) and full array P 1 and P 2 Solve the cosine visibility and reconstruct the brightness temperature image. Figure 7 As shown, from left to right are single " ” array, half-full array and full array reconstructed images, where Figure 7 (a)-(c) P 1 Reconstruct the image, Figure 7 (d)-(f) is P 2 Reconstructed image. The results show that based on P 2 Comparison of reconstructed images P 1 The reconstructed images are improved, and as the number of antennas gradually increases to a full array, the reconstructed images become clearer and clearer.

[0046] In order to show more clearly based on P 1 and P 2 The error of the reconstructed image is calculated using the root mean square error (RMSE) with the reconstructed image of the ideal cosine visibility as the benchmark. The RMSE is defined as: (15) in, represents the root mean square error, Indicates the reconstructed image The brightness temperature of the pixel, Indicates the ideal image The brightness temperature of the pixel, and Indicates the number of rows and columns of the reconstructed image.

[0047] The ideal reconstructed image is obtained by calculating the ideal cosine visibility of the original scene and then performing a two-dimensional inverse cosine transform. There is no rank deficiency error, so it can be used as a reference. In formula (15), is the reconstructed image under any antenna arrangement, For an ideal reconstructed image, Represents the reconstructed image Pixels. As shown in Table 1, a single "In the formation P 1 、 P 2 The reconstructed image errors are 54.77K and 53.67K respectively. P 1 、 P 2 The reconstructed image errors are 20.5K and 17.5K respectively. P 1 、 P2 The reconstructed image errors are 13.03K and 0.43K respectively. The results show that no matter what antenna arrangement is used, P 2 The error is always less than P 1 , a transfer matrix with a smaller rank defect P Therefore, artificial magnetic conductors are used instead of reflective metal plates to reduce P The rank deficiency in the matrix is beneficial for image reconstruction of two-dimensional mirror synthesis aperture.

[0048] Table 1 Root mean square error of reconstructed images (K)

[0049] In this embodiment, the metal reflector in the original two-dimensional mirror comprehensive aperture will cause a larger rank deficiency error. A method of replacing the metal reflector with an electromagnetic metamaterial is proposed. The electromagnetic control characteristics of the metamaterial are used to make the phase of the reflected wave in phase with the incident wave, thereby transferring the matrix P All non-zero elements in are converted to "1", reducing the rank deficiency error. Simulations with different antenna arrays show that the metasurface-based two-dimensional mirrored aperture synthesis has a smaller RMSE, resulting in a more ideal brightness temperature reconstruction image.

[0050] As described in step S500 above, the solution of the linear equations can be achieved by the least square method or matrix inversion.

[0051] It can be understood that the present invention proposes a method for improving the imaging quality of two-dimensional mirror synthesis aperture using artificial magnetic conductor (AMC) metamaterials. Traditional two-dimensional mirror synthesis aperture technology achieves high-resolution imaging with fewer antennas by combining antenna arrays with metal reflectors and utilizing the mapping relationship between antenna correlation values and cosine visibility. However, the metal reflector causes the phase of the incident signal to be inverted, introduces negative elements (-1) into the transfer matrix, causes matrix rank deficiency, and seriously restricts the accuracy of the reconstructed image. To solve this problem, the present invention uses an artificial magnetic conductor (AMC) with in-phase reflection characteristics to replace the metal reflector. Specifically, it includes: designing a cross-type AMC structure (parameters: , , , , FR4 dielectric layer), simulations confirm that it has a stable 0° reflection phase (in-phase reflection) in the 5.47–8.25 GHz and 15.13–16.07 GHz dual-bands and is robust to changes in TE / TM polarization and incident angle.

[0052] The in-phase reflection characteristic of AMC eliminates the signal phase reversal, so that all negative elements (-1) in the transfer matrix are converted to positive values (1). By comparing 82 antenna arrays (including single L array, half-full array and full array), it is found that the improved transfer matrix ( ) is significantly higher than the rank of the traditional matrix ( ), the rank loss is greatly reduced, especially when the formation is fully deployed, it approaches full rank.

[0053] Reconstruction experiments show that the AMC-based system ( ) has a lower root mean square error (RMSE) than the traditional system ( When the array is fully deployed, the RMSE is reduced from 13.03 K to 0.43 K, and the image clarity is significantly improved (e.g. Figure 7 The error of the half-filled array is also reduced from 20.5 K to 17.5 K.

[0054] This method fundamentally solves the rank deficiency problem through the electromagnetic control characteristics of AMC without increasing the complexity of the system. In summary, the present invention optimizes the mathematical model of the two-dimensional mirror comprehensive aperture through the innovative application of metamaterials, achieving a breakthrough improvement in imaging quality.

[0055] According to another aspect of an embodiment of the present application, an electronic device is provided, including a processor and a memory, wherein the processor is configured to implement the steps of the method when executing a computer program stored in the memory.

[0056] In the above embodiments of the present invention, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0057] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only exemplary. For example, the division of the units can be a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0058] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0059] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk, etc. Various media that can store program codes.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for reconstructing an image using a metamaterial-improved two-dimensional mirror aperture synthesis, characterized in that: The steps include: Configuring a two-dimensional mirror-image synthetic aperture system, wherein the two-dimensional mirror-image synthetic aperture system includes a two-dimensional antenna array and two sets of mutually perpendicular reflective structures; Replacing the two sets of mutually perpendicular reflection structures with a magnetic conductor structure, wherein the magnetic conductor structure has an in-phase reflection characteristic within a target frequency band; Calculating correlation values between antenna pairs based on the position coordinates of the antennas in the two-dimensional antenna array and the in-phase reflection characteristics of the magnetic conductor structure; Constructing a transfer matrix according to the calculated correlation values, wherein the non-zero elements of the transfer matrix are positive values; Establishing a linear equation system by using the transfer matrix and the cosine visibility function, and solving the linear equation system to obtain the cosine visibility; An inverse cosine transform is performed on the cosine visibility to reconstruct a brightness temperature image of the target scene.

2. The method for reconstructing an image using a metamaterial-improved two-dimensional mirror image synthesis aperture according to claim 1, wherein: The magnetic conductor structure includes a cross-shaped upper metal pattern, an intermediate dielectric layer and a bottom metal plate.

3. The method for reconstructing an image using a metamaterial-improved two-dimensional mirror synthetic aperture as claimed in claim 2, wherein: The material of the intermediate dielectric layer is FR4, with a dielectric constant of 4.3 and a tangent loss of 0.0025.

4. The method for reconstructing an image using a metamaterial-improved two-dimensional mirror image synthesis aperture according to claim 1, wherein: The in-phase reflection characteristic frequency bands of the magnetic conductor structure are: 5.47-8.25 GHz and 15.13-16.07 GHz; and the reflection phase is in the range of -90° to +90°.

5. The method for reconstructing an image using a metamaterial-improved two-dimensional mirror synthetic aperture as claimed in claim 1, wherein: Calculating the correlation values between antennas includes: For any two antennas and , the correlation value Determined by the sum of the following four cosine visibility terms: in, 、 and 、 Antenna and The coordinates of is the wavelength, Represents the two-dimensional cosine visibility function.

6. The method for reconstructing an image using a metamaterial-improved two-dimensional mirror image synthesis aperture as claimed in claim 1, wherein: The construction of the transfer matrix includes: Represent each correlation value as a linear combination of multiple cosine visibilities; The matrix elements are formed by the coefficients of the linear combination, and the coefficients are all positive.

7. The method for reconstructing an image using a metamaterial-improved two-dimensional mirror image synthesis aperture as claimed in claim 1, wherein: The method for establishing the linear equation system includes: Arranging the correlation values into a correlation value matrix in vector form according to antenna pairs; Determine each element of the transfer matrix according to the position coordinates of the antenna pair, wherein each element corresponds to a cosine visibility coefficient of a different spatial frequency combination, and the cosine visibility coefficients are all +1; Representing the cosine visibility function as a cosine visibility matrix in vector form; By multiplying the transfer matrix, the cosine visibility matrix, and the correlation value matrix, a linear equation system is constructed: in, represents the correlation value matrix, represents the transfer matrix, Represents the cosine visibility matrix.

8. The method for reconstructing an image using a metamaterial-improved two-dimensional mirror synthetic aperture as claimed in claim 1, wherein: The solution of the linear equations is achieved by the least square method or matrix inversion.

9. The method for reconstructing an image using a metamaterial-improved two-dimensional mirror image synthesis aperture as claimed in claim 1, wherein: The brightness temperature reconstruction formula of the inverse cosine transform is: in, is the brightness temperature distribution of the target scene, which represents the brightness temperature of the reconstructed image. and is the minimum spacing of spatial frequencies, corresponding to the antenna array in the horizontal direction and vertical direction The wavelength-normalized value of the minimum antenna spacing, and Represents the spatial frequency in the horizontal direction and vertical direction The total number of sampling points, is a two-dimensional cosine visibility function, which represents the spatial frequency point The visibility value obtained by measurement or calculation, is the weight coefficient, and is the direction cosine, and is the cosine basis function, which is used to convert the cosine visibility in the frequency domain back to the brightness temperature distribution in the spatial domain.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for reconstructing an image using a metamaterial-improved two-dimensional mirror synthetic aperture are performed as recited in any one of claims 1 to 9.

Images