CN-121978690-A - Novel joint regularization-based metamaterial phased array super-resolution imaging method

CN121978690ACN 121978690 ACN121978690 ACN 121978690ACN-121978690-A

Abstract

The invention relates to a novel joint regularization-based metamaterial phased array super-resolution imaging method which comprises the steps of obtaining echo signals of each distance unit in a metamaterial phased array scanning radar, establishing an imaging model between the echo signals of any distance unit and a target scattering coefficient, constructing an objective function comprising multiple regularization items aiming at the imaging model, wherein the objective function comprises a data fidelity item, a weighting L 1 norm item used for suppressing noise and sparse constraint, a self-adaptive group sparse L 2,1 norm item used for implementing differential constraint on structural characteristics of an imaging area, and a directional diagram error constraint item, and carrying out iterative solution on the objective function by adopting an alternate direction multiplier method to output a super-resolution target scattering characteristic reconstruction image. The scheme fully fuses the self-adaptive weighted L 1 norm item, the self-adaptive group sparse L 2,1 norm item and the joint correction and reconstruction mechanism, so that the scheme can cooperatively improve the structural fidelity and the system robustness of imaging.

Inventors

LUO CHENGGAO
ZHANG HENG
WANG HONGQIANG
LI ZHENJIANG
YANG QI
DENG BIN

Assignees

中国人民解放军国防科技大学

Dates

Publication Date: 20260505
Application Date: 20260403

Claims (9)

1. The novel joint regularization-based metamaterial phased array super-resolution imaging method is characterized by comprising the following steps of: S1, acquiring an echo signal of each distance unit in a metamaterial phased array scanning radar, and establishing an imaging model between the echo signal of any distance unit and a target scattering coefficient; S2, constructing an objective function comprising multiple regularization items aiming at the imaging model, wherein the objective function comprises a data fidelity item, a weighted L 1 norm item for suppressing noise and sparse constraint, an adaptive group sparse L 2,1 norm item for implementing differential constraint on structural characteristics of an imaging region, and a directional diagram error constraint item; S3, carrying out iterative solution on the objective function by adopting an alternate direction multiplier method, and outputting a super-resolution objective scattering characteristic reconstructed image.
2. The metamaterial phased array super-resolution imaging method based on novel joint regularization as claimed in claim 1, wherein in step S1, the step of obtaining the discretized echo signal of the metamaterial phased array scanning radar includes: s11, constructing a metamaterial phased array scanning radar model, wherein the metamaterial phased array scanning radar model comprises a horn antenna for transmitting signals and a metamaterial array antenna for receiving feed signals of the horn antenna and target echo signals; s12, constructing a transmitting signal model based on the signal type of the signal transmitted by the horn antenna; s13, assuming that a point target exists in a scanning scene, and the distance of the point target relative to a metamaterial phased array scanning radar is R, and the azimuth angle is beta m , acquiring a target echo signal model based on the transmitting signal model; s14, performing pulse compression on the target echo signal model to obtain echo signals of each distance unit.
3. The method for super-resolution imaging of a metamaterial phased array based on novel joint regularization as claimed in claim 2, wherein in step S12, in the step of constructing a transmit signal model based on the signal type of the signal transmitted by the horn antenna, the transmit signal model is expressed as: Wherein, the Representing the transmitted signal(s), A rectangular function is represented and is used to represent, The pulse width is indicated as such, The distance-wise time is indicated as such, Representing the carrier frequency of the carrier wave, Representing the tuning frequency; In step S13, in the step of acquiring the target echo signal model based on the transmission signal model, the target echo signal model is expressed as: Wherein, the Representing the echo signal of the object, Representing the back-scattering coefficient of the target, Is a metamaterial array antenna modulation function, belongs to a directional diagram function, Representing the two-pass echo time delay, The speed of light is indicated as being the speed of light, Representing the beam pointing angle; In step S14, in the step of performing pulse compression on the target echo signal model to obtain an echo signal of each range cell, the echo signal of each range cell is expressed as: Wherein, the An echo signal representing the distance element, Representing the bandwidth of the chirp signal, Representing the signal envelope after pulse compression.
4. A novel joint regularization-based metamaterial phased array super-resolution imaging method as claimed in any one of claims 1 to 3, wherein in step S1, an imaging model between echo signals of any distance unit and a target scattering coefficient is built, and the imaging model is built based on echo signals in a matrix form and is expressed as: Wherein Y represents a length of And (2) echo signals of , Representing echo signals at different angles of beam pointing, X represents the scattering characteristics of the target, and , Representing the scattering coefficients of the targets at various points at different angles, The number of sampling points representing the azimuth direction of the same distance unit in the original scene, N represents an additive noise vector, and , Representing the corresponding noise at different angles, Represents the antenna pattern modulation matrix and is expressed as: 。
5. the method for super-resolution imaging of a metamaterial phased array based on novel joint regularization as recited in claim 4, wherein in step S2, in the step of constructing an objective function including multiple types of regularization terms for the imaging model, the objective function is expressed as: Wherein, the In the case of a data-fidelity item, In order to weight the L 1 norm term, For the adaptive set sparse L 2,1 norm term, As a constraint term for the error of the pattern, An error matrix representing the antenna pattern modulation matrix, Representing the matrix of the adaptive weights, 、、 The regularization parameters are represented by a set of values, The product of the Hadamard is represented, The norm of the L 1 is indicated, The norm of the L 2,1 is indicated, Indicating the Frobenius norm.
6. The novel joint regularization-based metamaterial phased array super-resolution imaging method as claimed in claim 5, wherein in the step S3, the objective function is iteratively solved by adopting an alternate direction multiplier method, and the step of outputting a super-resolution target scattering characteristic reconstructed image comprises the following steps: S31, introducing auxiliary variables aiming at objective functions Auxiliary variable Converting the objective function into an objective function optimized based on constraints, wherein, , ; S32, constructing an augmented Lagrangian function based on the converted objective function; S33, carrying out iterative solution on the extended Lagrangian function by adopting an alternate direction multiplier method; s34, judging whether a convergence condition is met, if so, outputting a super-resolution target scattering characteristic reconstructed image, otherwise, continuing iteration until the convergence condition is met.
7. The metamaterial phased array super-resolution imaging method based on novel joint regularization as recited in claim 6, wherein in step S31, auxiliary variables are introduced for the objective function Auxiliary variable In the step of converting the objective function into the constraint-based optimized objective function, the converted objective function is expressed as: Wherein, the Representing the constraints that need to be met.
8. The method for super-resolution imaging of a metamaterial phased array based on novel joint regularization as recited in claim 7, wherein in the step of constructing an augmented lagrangian function based on the converted objective function in step S32, the augmented lagrangian function is expressed as: Wherein, the Representing an augmented lagrangian function, The two-pair variables are represented by the two-pair variables, Represents penalty parameters, and And (4) represents an inner product operation.
9. The method for super-resolution imaging of a metamaterial phased array based on novel joint regularization as recited in claim 8, wherein in step S33, in the step of iteratively solving the augmented lagrangian function by using the alternate direction multiplier method, the error matrix is updated sequentially Scattering characteristics of target Auxiliary variable Auxiliary variable Dual variable And dual variables It comprises: S331 updating error matrix Wherein, at the fixed target scattering characteristics Auxiliary variable Auxiliary variable Dual variable And dual variables Is based on minimizing the matrix of errors To update the error matrix The update procedure is expressed as: Wherein, the Represent the first The error matrix after a number of iterations, Representing update error matrices Is a target function of (2); For objective function The differentiation can be obtained by: Wherein, the Representing the trace of the matrix, i.e. the sum of all elements on the main diagonal of the matrix; Let the derivative be 0, it is possible to obtain: Wherein, the Representing the identity matrix; S332 updating the scattering characteristics of the target Wherein the error matrix is updated at a fixed location Auxiliary variable Auxiliary variable Dual variable And dual variables Is based on minimizing the scattering properties with respect to the target To update the target scattering characteristics The update procedure is expressed as: Wherein, the Represent the first The scattering properties of the target after a number of iterations, Representing updated target scattering characteristics Is a target function of (2); sorting objective function The method can obtain: Wherein, the The term of the constant is represented by a term, Representing a pattern matrix comprising errors, an ; For objective function The derivation can be carried out: ; Let the derivative be 0, a system of linear equations is obtained: Wherein, the Representing the identity matrix; S333, updating auxiliary variables Wherein, in a fixed error matrix Scattering characteristics of target Auxiliary variable Dual variable And dual variables On the basis of minimizing the variables related to the auxiliary To update the auxiliary variable The update procedure is expressed as: Wherein, the Represent the first An auxiliary variable of L 1 norms L 1 at each iteration; Order the Then: Wherein, the The sign function is represented by a sign function, A critical value representing a soft threshold, for determining the intensity of the contraction, Representing intermediate combined variables; s334, updating auxiliary variables In a fixed error matrix Scattering characteristics of target Auxiliary variable Dual variable And dual variables On the basis of minimizing the variables related to the auxiliary To update the auxiliary variable The update procedure is expressed as: Wherein, the Represent the first An auxiliary variable of L 2,1 norms L 21 at each iteration; for each grouping block g, let In the corresponding part of packet block g, then: Wherein, the Representation of A sub-matrix or vector of elements belonging to the grouping block g, A weighted combination representing the current solution; S335 updating the dual variables And dual variables A dual rising step: Wherein, the 、 Respectively represent the first Second iteration and first The dual variables of the number of iterations, 、 Respectively represent the first Second iteration and first The dual variables of the multiple iterations.

Description

Novel joint regularization-based metamaterial phased array super-resolution imaging method Technical Field The invention relates to the field of radars, in particular to a metamaterial phased array super-resolution imaging method based on novel joint regularization. Background Radar forward-looking imaging technology has been widely focused by researchers due to its important application value in many key fields such as topographic mapping, marine searching, autopilot, etc. In the technical field, conventional imaging modes such as Synthetic Aperture Radar (SAR) and Inverse Synthetic Aperture Radar (ISAR) cannot realize forward-looking high-resolution imaging due to high dependence on relative motion with a target, so that the application range of the imaging modes is limited to a large extent. To break through the limitations of conventional SAR in forward looking imaging, bistatic SAR and forward looking array SAR have evolved. Although the bistatic SAR can realize forward-looking imaging, the bistatic SAR faces the problems of difficult synchronization and complex hardware structure, which not only increases the design and maintenance cost of the system, but also can influence the stability and accuracy of imaging. The foresight array SAR can achieve the foresight imaging purpose, but is limited by a limited platform space, so that the performance advantage of the foresight array SAR is difficult to fully develop in practical application. The real aperture scanning radar has the remarkable advantages of wide imaging range, simple working mode and system structure and the like, and becomes common equipment for realizing forward-looking imaging. The front-view imaging task is completed by scanning an imaging area through the wave beam, and the application is wider. However, the real aperture scanning radar has some problems which are difficult to ignore. The feed network of the antenna array in the system has larger energy loss, which not only reduces the energy utilization efficiency of the radar, but also can influence the imaging quality, and meanwhile, the design complexity of the feed network is high, and the research and development cost and the technical difficulty are increased. In addition, the transceiver (T/R) module is high in cost, so that the overall cost of the real aperture scanning radar is high, and the large-scale application and popularization of the real aperture scanning radar are greatly limited. Therefore, to promote the further development of radar forward-looking imaging technology, research on new antenna arrays with low cost and low power consumption and new system real aperture scanning radars are urgently needed. In recent years, the artificial composite material which is made of a sub-wavelength patterned structure and is a metamaterial has been widely researched in academia and industry because of low cost, easy manufacturing and capability of flexibly manipulating electromagnetic waves. With the continuous progress of metamaterial technology, programmable metamaterials become a hot spot for research. The programmable metamaterial can realize wave front modulation of electromagnetic waves by changing the coding states of 0 and 1 of the unit structure, so that the accurate control of the propagation characteristics of the electromagnetic waves is realized. Considering the factors of manufacturing cost, processing difficulty, system complexity and the like, the 1bit programmable metamaterial is most commonly used at present. The phase mutation can be realized by arranging unit structures with phase responses of 0 degrees and 180 degrees, and a relatively simple and economical mode is provided for realizing a specific electromagnetic wave regulation effect. The metamaterial phased array antenna is generally composed of 1-bit programmable metamaterial units, and phase compensation is carried out on each unit to enable the metamaterial phased array antenna to meet required phase distribution, so that effective control over beam scanning is achieved. Based on these characteristics, metamaterial phased array antennas are considered as the most potential alternatives to conventional real aperture scanning radar antennas. Meanwhile, the new system real aperture scanning imaging radar based on the metamaterial phased array antenna shows important application prospect in the civil application field. In the azimuth direction, the radar echo can be modeled as the convolution of an antenna pattern and a target scattering coefficient, so that super-resolution imaging can be realized by a regularized deconvolution method. However, existing related methods often present problems or face limitations when applied to objects having a continuous structure, such as ships. For example, the L 1 norm tends to produce thin fluffs during the solution process, which may result in excessive cutting of the continuous area, so that the hull isohedral target is broken or discontinuous in the imaging, and t