Two-dimensional imaging methods, devices, and storage media based on array amplitude weighting

Abstract

This application discloses a two-dimensional imaging method, apparatus, and storage medium based on array amplitude weighting. The method includes: establishing a three-dimensional Cartesian coordinate system; dividing the main lobe of the beam into several imaging units to obtain a matrix representation of the echo signal; transforming the linear solution problem in the matrix representation into a minimum optimization problem; estimating the scattering intensity of each imaging unit; and achieving image reconstruction within the main lobe range of the beam. This application achieves azimuth and elevation resolution superior to that of a real aperture antenna beamwidth under staring imaging conditions without platform motion or beam scanning.

Description

Technical Field

[0001] This application relates to the field of radar imaging, and in particular to two-dimensional imaging methods, apparatus and storage media based on array amplitude weighting. Background Technology

[0002] Array radar is a fully digital array antenna radar based on beamforming mechanisms, where both the receiving and transmitting beams can be formed digitally using digital technology and methods. The basic structure of an array radar generally consists of an antenna array, a digital transmit / receive (T / R) module, a clock, a data transmission system, and a digital processor. The T / R module is the core of the digital array radar, integrating the transmitter, receiver, exciter, and local oscillator signal generator into a complete transmitter and receiver subsystem.

[0003] The relevant array radar requires a combination of platform movement and staring imaging conditions with beam scanning to obtain azimuth and elevation resolutions superior to those of a real aperture antenna beamwidth, and to achieve two-dimensional imaging, which is a rather inconvenient process.

[0004] Therefore, the aforementioned technical problems in the relevant technologies urgently need to be solved. Summary of the Invention

[0005] This application aims to solve one of the technical problems in related technologies. To this end, embodiments of this application provide a two-dimensional imaging method, apparatus, and storage medium based on array amplitude weighting, capable of achieving two-dimensional imaging of a specified target.

[0006] According to one aspect of an embodiment of this application, a two-dimensional imaging method based on array amplitude weighting is provided, the method comprising:

[0007] Establish a three-dimensional Cartesian coordinate system;

[0008] The beam main lobe is divided into several imaging units to obtain a matrix representation of the echo signal;

[0009] The linear problem in the matrix representation is transformed into an optimization problem of minimizing the value. The scattering intensity of each imaging unit is estimated to achieve image reconstruction within the main lobe range of the beam.

[0010] In one embodiment, in the three-dimensional Cartesian coordinate system, the center of the uniform circular array antenna is located at the origin of the coordinate system, the number of array elements is N, the array radius is a, and the coordinates of the nth array element in the three-dimensional Cartesian coordinate system are (x... n ,y n ,0), Let I be the azimuth angle of the nth array element. During transmission, the amplitude weighting coefficient of the nth array element is I. n .

[0011] In one embodiment, after establishing the three-dimensional Cartesian coordinate system, the method further includes:

[0012] Based on the three-dimensional Cartesian coordinate system, the expressions for the single-frequency pulse signal, the signal at any point P in space, the echo reflected from point P, the received signal of the nth array element, the sum of the received signals of N array elements, and the total echo from M scattering points are obtained.

[0013] In one embodiment, the formula for the single-frequency pulse signal is:

[0014]

[0015] Among them, f c Where is the carrier frequency of the transmitted signal, and T is the pulse width of the transmitted signal.

[0016] In one embodiment, the expression for the signal at any point P in the space is:

[0017]

[0018] Among them, t n f is the time delay from the nth array element to point P. c Where is the carrier frequency of the transmitted signal, and T is the pulse width of the transmitted signal.

[0019] In one embodiment, the echo expression of the reflection from point P is:

[0020]

[0021] Where σ is the scattering intensity at point P in the far field, I n t is the amplitude coefficient of the nth unit. n Let f be the signal delay from point P in the far field to the nth array element. c Where is the carrier frequency of the transmitted signal, and T is the pulse width of the transmitted signal.

[0022] In one embodiment, the expression for the received signal of the nth array element is:

[0023]

[0024] The sum of the signals received by the N array elements is expressed as:

[0025]

[0026] Factors in the echo This can be represented as exp[i(L α α+L β In the form of β), α and β are the azimuth and elevation angles of point P in the rectangular coordinate system;

[0027] Where t' is the time delay from point P in the far field to the center of the coordinate system, t n f is the signal delay from far-field point P to the nth array element. c α is the carrier frequency of the transmitted signal, T is the pulse width of the transmitted signal, α is the azimuth angle in the rectangular coordinate system, and β is the elevation angle in the rectangular coordinate system.

[0028] In one embodiment, the expression for the total echo from the M scattering points is:

[0029]

[0030]

[0031]

[0032] In one embodiment, dividing the main lobe of the beam into several imaging units to obtain a matrix representation of the echo signal includes:

[0033] Choose N = M phase changes with gradient magnitude L, and gradient directions respectively. The echo signal is obtained by modulating the field, and the phase change rates of the echo signal in the azimuth and elevation directions are respectively... as well as The echo signal is represented by a matrix as y = Hx + n.

[0034] In one embodiment, the linear solution problem in the matrix representation is transformed into a minimum optimization problem, and the scattering intensity of each imaging unit is estimated to achieve image reconstruction within the main lobe range of the beam, including:

[0035] The minimum value expression is obtained from the matrix expression of the echo signal:

[0036]

[0037] Find the scattering intensity estimate that minimizes the objective function. The scattering intensity of each imaging unit is estimated.

[0038] According to one aspect of an embodiment of this application, a two-dimensional imaging apparatus based on array amplitude weighting is provided, the apparatus comprising:

[0039] At least one processor;

[0040] At least one memory for storing at least one program;

[0041] When at least one of the programs is executed by at least one of the processors, the array amplitude-weighted two-dimensional imaging method as described in the preceding embodiments is implemented.

[0042] According to one aspect of the embodiments of this application, a storage medium is provided, the storage medium storing a processor-executable program, which, when executed by a processor, implements the array amplitude-weighted two-dimensional imaging method as described in the preceding embodiments.

[0043] The beneficial effects of the two-dimensional imaging method, apparatus, and storage medium based on array amplitude weighting provided in this application are as follows: The method of this application includes: establishing a three-dimensional Cartesian coordinate system; dividing the main lobe of the beam into several imaging units to obtain a matrix representation of the echo signal; transforming the linear solution problem in the matrix representation into a minimum optimization problem, estimating the scattering intensity of each imaging unit, and realizing image reconstruction within the main lobe range of the beam. This application can obtain azimuth and elevation resolutions superior to those of a real aperture antenna beamwidth under staring imaging conditions without platform motion or beam scanning.

[0044] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 A flowchart illustrating a two-dimensional imaging method based on array amplitude weighting, provided for embodiments of this application;

[0047] Figure 2 This is a schematic diagram of a circular array antenna provided in an embodiment of this application;

[0048] Figure 3 This is a schematic diagram of the azimuth-elevation two-dimensional imaging plane provided in an embodiment of this application;

[0049] Figure 4 This is a schematic diagram of spatial phase modulation field imaging provided in an embodiment of this application;

[0050] Figure 5 This is a schematic diagram of a two-dimensional imaging device based on array amplitude weighting, provided as an embodiment of this application. Detailed Implementation

[0051] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0052] The terms "first," "second," "third," and "fourth," etc., used in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0053] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0054] Array radar is a fully digital array antenna radar based on beamforming mechanisms, where both the receiving and transmitting beams can be formed digitally using digital technology and methods. The basic structure of an array radar generally consists of an antenna array, a digital transmit / receive (T / R) module, a clock, a data transmission system, and a digital processor. The T / R module is the core of the digital array radar, integrating the transmitter, receiver, exciter, and local oscillator signal generator into a complete transmitter and receiver subsystem.

[0055] The relevant array radar requires a combination of platform movement and staring imaging conditions with beam scanning to obtain azimuth and elevation resolutions superior to those of a real aperture antenna beamwidth, and to achieve two-dimensional imaging, which is a rather inconvenient process.

[0056] To address the aforementioned issues, this application proposes a two-dimensional imaging method, apparatus, and storage medium based on array amplitude weighting. This method achieves superior azimuth and elevation resolution compared to the beamwidth of a real-aperture antenna under staring imaging conditions that do not require platform motion or beam scanning. It has significant application value in scenarios requiring high-resolution forward-looking imaging, such as terminal-guided precision strikes and autonomous vehicle radar.

[0057] Figure 1 A flowchart of a two-dimensional imaging method based on array amplitude weighting provided in this application embodiment is shown below. Figure 1 As shown, the two-dimensional imaging method based on array amplitude weighting provided in this application includes:

[0058] S101. Establish a three-dimensional Cartesian coordinate system;

[0059] S102. Divide the main lobe of the beam into several imaging units to obtain a matrix representation of the echo signal;

[0060] S103. The linear solution problem in the matrix representation is transformed into an optimization problem of minimizing the value. The scattering intensity of each imaging unit is estimated to achieve image reconstruction within the main lobe range of the beam.

[0061] like Figure 2 As shown, in the three-dimensional Cartesian coordinate system, the center of the uniform circular array antenna is located at the origin of the coordinate system, the number of array elements is N, the array radius is a, and the coordinates of the nth array element in the three-dimensional Cartesian coordinate system are (x... n ,y n ,0), Let I be the azimuth angle of the nth array element. During transmission, the amplitude weighting coefficient of the nth array element is I. n .

[0062] The transmitted single-frequency pulse signal can be represented as

[0063]

[0064] f c Let be the carrier frequency of the transmitted signal. Then, any point in space... The signal at this location can be represented as

[0065]

[0066] Where t n The time delay from the nth array element to point P, t n =t'-Δd / c, t'=r / c, Assuming the scattering intensity at point P is σ, then the echo reflected from point P is...

[0067]

[0068] When N array elements receive signals with equal amplitude and in phase, the received signal of the nth array element can be expressed as:

[0069]

[0070] When the detection distance is long, t n=t'-Δd / c, where t'>>Δd / c, and t in the pulse envelope. n It can be approximated as t', and the second phase of Δd / c in the phase approximation can be ignored. Equation (4) can be expanded as follows:

[0071]

[0072] The sum of the signals received by N array elements is:

[0073]

[0074] Factors in the echo This can be represented as exp[i(L α α+L β In the form of β), α and β are the azimuth and elevation angles of point P in a rectangular coordinate system. Assume there are M scattering points at the same distance r from point P in the azimuth direction, and the azimuth angle of the m-th scattering point is α. m Pitch angle β m The scattering intensity is σ m The total echoes from all M scattering points can be expressed as:

[0075]

[0076] in,

[0077]

[0078] like Figure 3 As shown, the main lobe of the beam is divided into M = K × K imaging units. The coordinates of each imaging unit are (α... k ,β k The scattering intensity is σ. kk When there are scattering points within the imaging unit, σ kk The scattering intensity at this scattering point is σ when there are no scattering points within the imaging unit. kk The value is zero. According to inversion imaging theory, the target echo can be viewed as the dot product of the phase modulation field pattern and the scattering intensity of the target scattering point. To estimate the scattering intensity of each imaging unit, a measurement matrix H needs to be constructed using N ≥ M different phase gradient modulation fields. We choose N = M phase change gradients with magnitude L and gradient directions of... The echo signal is obtained by modulating the field, and its phase change rates in the azimuth and elevation directions are respectively... as well as The echo signal can be represented by a matrix as follows:

[0079] y = Hx + n (9)

[0080]

[0081] In the formula, H is an N×M dimensional measurement matrix containing N row vectors, each representing a spatial phase distribution of a modulation field. Each row vector contains M complex elements, corresponding to the differential spatial phase distribution within each imaging unit under that spatial phase modulation field. x is a column vector containing target scattering intensity information, with each element σ kk Represents the coordinates (α) k ,β k The scattering intensity of the imaging unit, y is an N-dimensional column vector containing N types of modulated field echo signals. Based on the spatial phase modulation field of the circular array, both azimuth and elevation have differential phase distributions. The target position information at different azimuths and elevations is reflected in the echo phase exp[i(L α α+L β In β), a physical basis is provided for achieving azimuth-elevation imaging at the same distance. The linear solution problem of x in equation (9) is transformed into an optimization problem of minimizing the value.

[0082]

[0083] Find the scattering intensity estimate that minimizes the objective function. The imaging problem is transformed into estimating the scattering intensity vector x from the measurement result y. By estimating the scattering intensity of each imaging unit, image reconstruction within the main lobe range of the beam can be achieved.

[0084] Furthermore, this application also proposes a two-dimensional imaging device based on array amplitude weighting, such as... Figure 5 As shown, the device includes:

[0085] At least one processor;

[0086] At least one memory for storing at least one program;

[0087] When at least one of the programs is executed by at least one of the processors, the array amplitude-weighted two-dimensional imaging method as described in the preceding embodiments is implemented.

[0088] In addition, this application also proposes a storage medium storing a processor-executable program that, when executed by a processor, implements the array amplitude-weighted two-dimensional imaging method as described in the preceding embodiments.

[0089] Similarly, the content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented in this storage medium embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0090] In some alternative embodiments, the functions / operations mentioned in the block diagrams may not occur in the order shown in the operation diagrams. For example, depending on the functions / operations involved, two consecutively shown blocks may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order. Furthermore, the embodiments presented and described in the flowcharts of this application are provided by way of example to provide a more comprehensive understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is changed and sub-operations described as part of a larger operation are executed independently.

[0091] Furthermore, although this application is described in the context of functional modules, it should be understood that, unless otherwise stated to the contrary, one or more of the functions and / or features may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in a separate physical device or software module. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding this application. Rather, given the properties, functions, and internal relationships of the various functional modules in the apparatus disclosed herein, the actual implementation of the module will be understood within the scope of conventional technology for an engineer. Therefore, those skilled in the art can implement the application set forth in the claims using ordinary techniques without excessive experimentation. It is also understood that the specific concepts disclosed are merely illustrative and not intended to limit the scope of this application, which is determined by the full scope of the appended claims and their equivalents.

[0092] If a function is implemented as 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 this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0093] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0094] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0095] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0096] In the foregoing description of this specification, the references to terms such as "one embodiment," "another embodiment," or "some embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0097] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

[0098] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A two-dimensional imaging method based on array amplitude weighting, characterized in that, The method includes: A three-dimensional Cartesian coordinate system is established, in which the center of the uniform circular array antenna is located at the origin, the number of array elements is N, the array radius is a, and the coordinates of the nth array element in the three-dimensional Cartesian coordinate system are: , , Let be the azimuth angle of the nth element. During transmission, the amplitude weighting coefficient of the nth element is: ; Based on the three-dimensional Cartesian coordinate system and the amplitude weighting coefficients, array amplitude weighting processing is performed to obtain the weighted single-frequency pulse signal, the signal at any point P in space, the echo reflected from point P, the received signal of the nth array element, the sum of the received signals of N array elements, and the total echo of M scattering points. The beam main lobe is divided into several imaging units to obtain a matrix representation of the echo signal; The linear problem in the matrix representation is transformed into an optimization problem of minimizing the value, and the scattering intensity of each imaging unit is estimated to achieve image reconstruction within the main lobe range of the beam. The expression for the received signal of the nth array element is: The expression for the sum of the signals received by the N array elements is: Factors in the echo It can be represented as In the form of, where the phase change rates of the received signal in the azimuth and elevation directions are defined as follows: , , and for P The azimuth and elevation angles of a point in a rectangular coordinate system; Where t' is the time delay from point P in the far field to the center of the coordinate system, t n Let f be the signal delay from point P in the far field to the nth array element. c Where α is the carrier frequency of the transmitted signal, T is the pulse width of the transmitted signal, α is the azimuth angle in the rectangular coordinate system, and β is the elevation angle in the rectangular coordinate system. The expression for the total echo from the M scattering points is: in, m For the first m The scattering intensity at each scattering point is defined as the phase change rate of the total echo from each scattering point in the azimuth and elevation directions, respectively. ; The step of dividing the main lobe of the beam into several imaging units to obtain a matrix representation of the echo signal includes: choose The phase change gradient has a magnitude of L and gradient directions of [missing information]. The echo signal is obtained by modulating the field, and the phase change rates of the echo signal in the azimuth and elevation directions are respectively... as well as The echo signal is represented by a matrix as follows: Where n represents the nth element in the uniform circular array, and H is... The H-dimensional measurement matrix contains N There are 1 row vectors, each representing a spatial phase distribution of the modulation field; x is a column vector containing target scattering intensity information, each element... Represents coordinates The scattering intensity of the imaging unit, y is the sum of the scattering intensities of the imaging unit. N Type of modulated field echo signal N 3D column vector; The linear solution problem in the matrix representation is transformed into a minimum optimization problem. The scattering intensity of each imaging unit is estimated to achieve image reconstruction within the main lobe range of the beam, including: The minimum value expression is obtained from the matrix expression of the echo signal: Find the scattering intensity estimate that minimizes the objective function. The scattering intensity of each imaging unit is estimated.

2. The two-dimensional imaging method based on array amplitude weighting according to claim 1, characterized in that, The formula for the single-frequency pulse signal is: Among them, f c Where is the carrier frequency of the transmitted signal, and T is the pulse width of the transmitted signal.

3. The two-dimensional imaging method based on array amplitude weighting according to claim 1, characterized in that, The expression for the signal at any point P in the space is: in, f is the time delay from the nth array element to point P. c Where is the carrier frequency of the transmitted signal, and T is the pulse width of the transmitted signal.

4. The two-dimensional imaging method based on array amplitude weighting according to claim 1, characterized in that, The expression for the echo reflected from point P is: Where σ is the scattering intensity at point P in the far field, I n t is the amplitude coefficient of the nth unit. n Let f be the signal delay from point P in the far field to the nth array element. c Where is the carrier frequency of the transmitted signal, and T is the pulse width of the transmitted signal.

5. A two-dimensional imaging device based on array amplitude weighting, characterized in that, The device includes: At least one processor; At least one memory for storing at least one program; When at least one of the programs is executed by at least one of the processors, the array amplitude-weighted two-dimensional imaging method as described in any one of claims 1-4 is implemented.

6. A storage medium, characterized in that, The storage medium stores a processor-executable program, which, when executed by the processor, implements the array amplitude-weighted two-dimensional imaging method as described in any one of claims 1-4.

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