381 results about "Synthetic aperture radar imaging" patented technology

An active imaging system for imaging a target is described. The system includes a transmitting unit, a receiving unit, an antenna arrangement coupled to the transmitting unit and/or the receiving unit via a front end unit, and an image processing unit coupled to the receiving unit. The system also includes a control system coupled to the transmitting unit, the receiving unit and/or the image processing unit for controlling operation thereof. The antenna arrangement includes at least one rotating antenna synthetically forming a circular antenna. The image processing unit is configured for creating an image of the object by employing a synthetic aperture radar imaging algorithm.

The invention discloses a 3D terrain imaging system of the interferometric synthetic aperture radar (InSAR) and an elevation mapping method thereof, which mainly solve the problems that the existing InSAR has bad imaging pragmaticality and can not implement 3D elevation mapping on the fast-changing terrain and the transilient terrain. The system comprises three sub-aperture antennas, a radar transmitter, a radar receiver and an imaging data processor; the imaging signal processor comprises a SAR image processing unit and an InSAR image processing unit. The invention receives radar echo through the three sub-apertures, then conducts SAR imaging process on the radar echo respectively received by the three sub-apertures, and then conducts InSAR imaging process on the obtained SAR complex pattern, wherein the InSAR imaging process comprises image registration, phase filtering and phase unfolding based on cluster analysis. The processed InSAR phase unfolded image is processed with an elevation inversion to recover a three dimensional digital elevation map. The invention has the advantages of wide adaptability to mapped terrains, and high imaging effectiveness, therefore, the invention can be used in the mapping of the 3D terrain.

The invention discloses a linear array SAR sparse reconstitution imaging and model phase error correction method. According to the characteristic that scattering targets are sparse in an actual linear array three-dimensional SAR imaging scene space, the linear array SAR sparse reconstitution imaging and model phase error correction method establishes a linear measurement matrix of linear array SAR original echo signals and scattering coefficients in a scene target space, phase error factors existing in the linear array three-dimensional SAR actual measurement are also taken into account, a scattering phase vector between a phase error matrix and a scene target is estimated through iterative optimization, imaging processing of the sparse targets in a linear array SAR three-dimensional space is realized, the effect on imaging by phase errors is restrained, and the stability of linear array SAR sparse reconstitution imaging and the imaging precision of a linear array SAR are improved. The linear array SAR sparse reconstitution imaging and model phase error correction method can be applied to synthetic aperture radar (SAR) imaging, earth remote sensing and other fields.

The invention discloses an imaging method for a bistatic forward-looking synthetic aperture radar (SAR). Aiming at the defect existing when the existing method is used for the imaging process of the bistatic forward-looking synthetic aperture radar, the imaging method adopts a bistatic forward-looking SAR point target response two-dimensional frequency spectrum based on the least square polynomial fitting; the frequency spectrum is the least square approximation of the two-dimensional frequency spectrum with the accurate theory. According to the characteristics of bistatic forward-looking invariant SAR direction, variant range and nonlinear and variant Doppler centroid range of range cell migration in an RD (radar domain) domain, bistatic forward-looking SAR range migration correction, secondary-range compression and high-order phase compensation are realized by the frequency spectrum so as to accurately focus the bistatic forward-looking SAR. Compared with the traditional SAR imaging method and the bistatic forward-looking SAR imaging method, the method disclosed by the invention has higher imaging precision.

The invention provides a linear array SAR imaging method based on iterative minimization sparse Bayesian reconstitution. The method is prior distributional hypothesis based on a linear array SAR original echo signal measurement model, it is assumed that a prior probability density function of a scattering coefficient in a linear array SAR observation scene target space complies with complex exponential prior distribution, it is also assumed that a posterior probability density function of a linear array SAR original echo signal complies with Gaussian stochastic distribution, a reconstitution cost function of the scattering coefficient in the linear array SAR observation scene target space is set up through the Bayesian criterion, sparse reconstitution of the scattering coefficient in the linear array SAR observation scene target space is achieved through complex exponential distribution parametric optimization estimation and the iterative minimization constitution cost function, and therefore performance of linear array SAR sparse imaging is improved. The linear array SAR imaging method can be applied to the synthetic aperture radar imaging field, the global remote sensing field and other fields.

The invention discloses an inverse synthetic aperture radar imaging method for maneuvering targets on the basis of the sparse aperture. The inverse synthetic aperture radar imaging method for the maneuvering targets on the basis of the sparse aperture comprises the implementation steps that (1) original echo data, with the sparse aperture, of an inverse synthetic aperture radar are received; (2) distance compression and envelope alignment processing are carried out; (3) phase correction is accurately carried out; (4) sparse aperture echo signals are reconstructed; (5) fast Fourier transform is carried out to achieve distance-Doppler imaging. According to the inverse synthetic aperture radar imaging method for the maneuvering targets on the basis of the sparse aperture, accurate phase compensation and accurate data reconstruction can be carried out on ISAR imaging processing under the conditions of the maneuvering targets and the sparse aperture, and a more focused high-quality ISAR imaging result is obtained.

The invention discloses a method for compressed sensing synthetic aperture radar imaging based on dual sparse constraints. The method mainly solves the problems that a complete SAR image cannot be obtained in imaging through a traditional synthetic aperture radar imaging method and time loss is large. The method comprises a first step of utilizing radar to irradiate a ground sparse scene D and obtain echo signals r of the scene; a second step of constructing an orientation direction base matrix A of the scene and a distance direction base matrix B of the scene; a third step of obtaining an orientation direction measurement matrix theta, a distance direction measurement matrix omega and an echo measurement matrix S according to the orientation direction base matrix and the distance direction base matrix; a fourth step of constructing a Lagrangian function f(Y,U) according to the orientation direction measurement matrix, the distance direction measurement matrix and the echo measurement matrix; and a fifth step of using an alternate iteration multiplier method to solve the Lagrangian function f(Y,U) in the fourth step and obtaining an image of the scene D. The method can achieve high-resolution imaging of synthetic aperture radar in downsampling, is quick in imaging speed and can be used for large-area topographic mapping and cartography.

The invention discloses a synthetic aperture radar imaging method based on L<1/2> regularization and relates to a radar two-dimension imaging technology. The synthetic aperture radar imaging method includes the steps of a, establishing a synthetic aperture radar imaging model based on the L<1/2> regularization according to a synthetic aperture radar observation model; and b, using an iteration half threshold value algorithm to reconstruct an observation scene backscattering coefficient. Compared with traditional synthetic aperture radar imaging methods, the synthetic aperture radar imaging method is capable of reducing a sampling quantity required by the correct reconstruction of an objective scene and achieving effective imaging of synthetic aperture radar data.

The invention provides a synthetic aperture radar anti-deceptive-interference method based on shadow characteristics. Firstly, SAR images with and without shadows of several types of targets under different postures are obtained by using a synthetic aperture radar imaging method and an electromagnetic scattering simulation method. The SAR images obtained at different radar incident angles are used as training samples and test samples for a convolutional neural network. In order to overcome the disadvantage of poor shadow characteristic identification effect of the convolutional network, a first-level convolutional neural network is used to classify the targets and the backgrounds to obtain targets and backgrounds of different types, a standard threshold segmentation method and multi-value processing are employed for key target images to obtain multi-value images after target regions are segmented, and real targets and deceptive targets are distinguished by a convolutional neural network classification method. The functions of SAR automatic target identification and interference target identification are realized, and high-performance SAR anti-deceptive-interference in the image domain is achieved.

The invention discloses an ISAR (inverse synthetic aperture radar) imaging method based on a convolutional neural network, and the imaging method comprises the following steps: S1, constructing an ISAR data set; S2, obtaining an initial image by two-dimensional Fourier transform; S3, constructing the convolutional neural network; S4, constructing a training set and a verification set of the convolutional neural network; S5, updating the parameters of the convolutional neural network through using a supervised learning method; S6, using the trained convolutional neural network to achieve the ISAR downsampling data imaging. The convolutional neural network of the invention can be used for extracting more feature information and can effectively avoid the gradient dispersion phenomenon, thereby reconstructing a higher quality ISAR image.

The invention discloses a terahertz inverse synthetic aperture radar imaging method based on a frequency modulation step frequency to solve the problem that in the prior art, the range resolution and the direction resolution of inverse synthetic aperture radar imaging in the microwave band are not high. The method includes the steps of firstly, obtaining a terahertz pulse echo signal; secondly, conducting pulse compression; thirdly, synthesizing a broadband; fourthly, conducting windowing and correcting; fifthly, conducting distance Doppler imaging; sixthly, obtaining an imaged picture. According to the method, the characteristic that the terahertz wave has the high frequency and the broadband is combined with the frequency modulation step frequency system so that the high-resolution terahertz inverse synthetic aperture radar imaging can be achieved through the method of synthesizing the broadband.

The invention provides a hard threshold OMP (orthogonal matching pursuit)-based linear array SAR (synthetic aperture radar) sparse imaging method. A linear measurement matrix of original echo signals of a linear array SAR and scattering coefficients in a target space of an observed scene is established for the characteristic that main scattering targets are spatially sparse in the target space of the observed scene of the linear array SAR, and contrast between maximum and minimum target scattering coefficients and a target scattering coefficient change rate are used as iteration ending conditions for the iteration processing of a hard threshold OMP algorithm, so that the dependence of a conventional OMP algorithm on the number of the main scattering targets in linear array SAR sparse imaging is overcome. Compared with a conventional OMP algorithm-based linear array SAR sparse imaging method, so that the method has the advantages that the number of the main scattering targets in the target space of the observed scene is not required to be known, and the method is more applicable to the linear array SAR sparse imaging when the number of the main scattering targets is unknown under actual conditions; the imaging accuracy of the linear array SAR is improved. The method can be applied to the fields of SAR imaging, earth remote sensing and the like.

The invention discloses an SAR (Synthetic Aperture Radar) imaging signal processing data transposing method based on an FPGA (Field Programmable Gata Array), which is mainly used for solving the problems of high power consumption, low speed, low efficiency and no radiation resistance existing in a real-time imaging processing CTM (Communication Terminal Module) based on a DSP (Digital Signal Processor). The method comprises the following implementation steps of: storing signal processing data in a DDRII SDRAM (Double Data Rate II Synchronous Dynamic Random Access Memory) through the FPGA; performing matrix partitioning on matrix data in the DDRII SDRAM; transposing a diagonal mode matrix block and a symmetrical non-diagonal mode matrix block in sequence; when the quantity of distance direction sampling points is unequal to that of azimuth direction sampling points, transposing the an asymmetrical non-diagonal mode matrix block; resetting after transposition; and reading out the transposed data in the DDRII SDRAM as required by using the FPGA. Due to the adoption of the transposing method, the working efficiency of the DDRII SDRAM is improved greatly, and a transposition memory CTMsystem runs more stably, has lower power consumption, higher speed and higher efficiency and is resistant to radiation; and the transposing method can be applied to the design of an SAR imaging system.

The invention discloses a method for imaging a stationary transmitter bistatic foresight synthetic aperture radar (ST-BFSAR). The method comprises the following specific steps: after obtaining a target echo, rectifying a two-dimensional space variant of a distance migration of the ST-BFSAR by using first-order Keystone transform, wherein an object which has a same bistatic distance sum at a slow time zero moment is moved to a same distance gate during the operation; and after the distance migration rectification is accomplished, balancing the Doppler chirp scaling of an object in the same distance gate by using a non-linear chirp scaling variant object so as to eliminate the space variant of the Doppler chirp scaling along a directional bit and accomplishing the directional bit compression, so that the precise focusing of the ST-BFSAR is realized, and the problem that the two-dimensional space variant during the data treatment of the ST-BFSAR cannot be solved by using a traditional SAR (Synthetic Aperture Radar) imaging method and an existing bistatic foresight SAR imaging method is solved.

The invention provides a linear array SAR (Synthetic Aperture Radar) three-dimensional imaging method based on a threshold gradient tracking algorithm. The method comprises the steps of establishing a linear measurement model between linear array SAR original echo signals and a three-dimensional observation scene target scattering coefficient using a correlation among linear array SAR system parameters, motion platform parameters, space parameters of an observation scene target and original echo signals, and then reconstructing the observation scene target scattering coefficient using a TBGP (Total Blood Granulocyte Pool) method based on the signal linear measurement model. By using the contrast of maximum and minimum target scattering coefficients and the change rate of the target scattering coefficient as algorithm iteration termination conditions, the linear array SAR sparse imaging performance of a GP (Genetic Programming) algorithm under the condition that the sparsity of the observation scene is unknown is improved, the operation efficiency and the space storage efficiency are improved relative to an OMP (Orthogonal Matching Pursuit) algorithm, and the method can be applied in the fields of synthetic aperture radar imaging, earth remote sensing and the like.

The invention relates to an ultra-low signal-to-noise ratio medium and high orbit satellite target ISAR imaging method, and mainly relates to the technical field of inverse synthetic aperture radar imaging. The method provided by the invention comprises the steps that the slant range course between a ground radar and a target satellite is calculated by using a target satellite orbit and the phasecenter position of a radar antenna, and pulse compression is carried out on original echo data received by the radar; according to the slant range course and radar imaging geometric parameters, the curvature walk of a target envelope is corrected; the delay phase of an ionized layer is compensated along azimuth, and a linear model is used to correct an envelope alignment error caused by a radar geometric parameter measurement error and a satellite orbit measurement error; the translation phase of the target is compensated, and fast Fourier transform (FFT) along azimuth is carried out to acquire an initial ISAR image; and finally, the quadratic translation phase error of the target is estimated and compensated according to the initial ISAR image, so as to acquire a final medium and high orbit satellite target ISAR image.

The invention discloses an airborne three-dimensional synthetic aperture radar imaging system based on transmitted beam scanning. In the current three-dimensional synthetic aperture radar imaging system, echo data volume is large, imaging processing is complex and timeliness is low. Using the airborne three-dimensional synthetic aperture radar imaging system of the invention can solve the above problems. In the invention, a radar transmitter generates narrow wave beams possessing different preset orientations in a vertical heading by using a transmitted beam forming technology. A phased-arrayantenna, which is arranged vertically to the heading in a flight plane, successively transmits the narrow wave beams generated by the radar transmitter one by one. Narrow wave beam scanning to the vertical heading can be performed in every direction at any time. The echo is received by a single array element of the phased-array antenna and is sent to a radar receiver so as to complete acquisitionof single channel echo data. An imaging processor can be used to three-dimensionally image the collected echo data. By using the invention, echo data volume is small, imaging processing is not complex and timeliness is strong. And the system has the ability of rapid three dimensional imaging an object scene, especially the complex object scene.

The invention belongs to an imaging method for nonlinear frequency modulation label change in the synthetic aperture radar imaging technology, which comprises the steps of two-dimensional frequency domain unfolding, filtering processing, nonlinear frequency modulation label change, distance compression, distance migration correction, rest phase compensation and position compression. In the method of the invention, the characteristics of orthogonality and minimum square error of the Legendre polynomials are utilized for carrying out three-order unfolding on the two-dimensional frequency domain signals of the obtained echo signals according to the Legendre orthogonality polynomials, and then, the focusing imaging on targets is realized through carrying out filtering processing and the like on three-order phase items in echo signal two-dimensional frequency domain expression. When the method of the invention is adopted, the maximum phase error under the same condition is less than 0.2 percent of the maximum phase error in the prior art, so the assurance is provided for the high-precision imaging under the large-inclination view angle condition. Therefore, the method of the invention has the characteristics that the phase error in the imaging process can be effectively reduced, the imaging processing of the large-inclination view angle is realized, in addition, the imaging effect is good, the imaging processing efficiency and the precision are high, and the like.

An imaging method of interference fitting aperture radar based on multiple ultra-displayed point includes selecting out pixel point with heavy energy named as ultra-displayed point from ISAR image, using interference means to obtain phase main value, making dewrapping on said main value to obtain true value of each ultra-displayed point, carrying out scaling on said point to obtain Doppler frequency and horizontal distance, fitting out relation of said frequency to said distance and carrying out scaling on each pixel point of ISAR image to obtain In ISAR image reflecting true size of object.

The present invention discloses a spread spectrum through-the-wall radar imaging method based on the compression perception technology. After an index average background elimination method is employed to remove the direct wave and the wall clutter, measurement signals are obtained through a random measurement matrix, a dictionary having been set and the measurement matrix are combined to construct a compressed perception model of a multi-measurement vector (MMV), target image information after the all is reconstructed from the measurement including few measurement values through an orthogonal matching pursuit (OMP) method, and finally, the through-the-wall radar is completed according to the target after the wall. Compared with a traditional synthetic aperture radar imaging method, the spread spectrum through-the-wall radar imaging method based on the compression perception technology is able to greatly reduce the number of the observation points and the data storage amount and shorten the recording time. The problems are solved that the spread spectrum through-the-wall radar SAR imaging method in the prior art requires lots of observation antennas, large data storage space and long data recording time.