25 results about "Range migration" patented technology

The invention provides a multilayer medium efficient imaging method suitable for frequency modulation continuous wave ice radar data, and belongs to the field of frequency modulation continuous wave ice radar imaging. Comprising the steps of multi-layer medium signal model construction, improved distance-Doppler algorithm implementation, distance migration accurate correction and azimuth focusing processing. According to the method, a multi-layer medium signal model containing refractive index and propagation velocity changes is established for the problem of target distance distortion caused by propagation velocity differences of electromagnetic waves in different media such as ice and snow; based on the model, a traditional distance-Doppler algorithm process is improved, distance migration caused by multiple layers of media is accurately corrected by introducing a medium-dependent distance migration factor, and efficient azimuth focusing is achieved. And finally, a high-resolution ice layer internal structure image can be generated, and the method is suitable for polar region large-range ice cover detection and rapid processing of a large amount of ice radar data.

The invention discloses a switching judgment method and device for a low-orbit satellite communication coverage area, and relates to the technical field of satellite communication. The method comprises the following steps: determining a first scanning wave position set of each wave beam of a low-orbit satellite in a current coverage area; determining a second scanning wave position set of each wave beam when the low-orbit satellite migrates to the next coverage area; according to the first scanning beam position set and the second scanning beam position set of each beam, determining a virtual beam position scanning scheme of each beam in a next-hop beam period by using a genetic algorithm; judging whether each beam is subjected to beam migration in a next-hop beam period or not; and migrating the communication coverage range of the low-orbit satellite to the next coverage area in the next-hop beam period under the condition that the number of the beams subjected to beam migration is judged to reach the preset threshold value. Therefore, the method can adapt to the scanning characteristics and coverage requirements of different beams of the multi-beam low-orbit satellite based on the independent judgment logic of each beam.

This application relates to a terahertz video synthetic aperture radar moving target imaging method based on time-frequency analysis. The method includes: constructing a radar echo model of the moving target based on instantaneous range and radar echo; processing the radar echo model by performing a short-time Fourier transform on the compressed echo signal; obtaining the Doppler center frequency of the scene echo from the obtained time-frequency distribution map; performing Doppler frequency zero-padding, range migration correction, and azimuth processing on the compressed echo signal according to a pre-set function; observing the range cell position of the moving target from the obtained imaging results; and extracting and performing time-frequency analysis on the moving target signal. After determining the Doppler center frequency of the moving target through time-frequency analysis and the time-frequency map, velocity estimation is performed; and the image of the moving target is refocused based on the characteristics of the time-frequency distribution line of the moving target echo. This method can quickly achieve velocity estimation and image refocusing of moving targets.

The application relates to a space target joint imaging and attitude inversion method based on a spaceborne platform, and relates to the field of inverse synthetic aperture radar imaging, in particular to a space target joint imaging and attitude inversion method based on a spaceborne platform. The application aims to solve the problems that in the existing space target imaging process of a spaceborne platform, three-dimensional high-order space-variable range migration and phase errors caused by complex relative motion between the target and the platform are difficult to realize high-precision imaging, and the existing attitude estimation algorithm needs to be completely compensated for the rectangular component segmentation and orbit error before the attitude inversion can be realized. The process is as follows: one, a narrowband tracking system of a radar obtains target slant range and a radar line-of-sight unit vector; two, a wedge-shaped transformed signal is obtained; three, spatial Doppler parameter distribution of a special point is obtained; four, an imaging result is obtained; and five, accurate estimation of target attitude parameters is completed through plane coefficient fitting.

The invention relates to a quality improvement method for a high-resolution image. The method comprises the following steps: obtaining an equal-target two-way slope distance; calculating a distance error; calculating a two-dimensional frequency spectrum; calculating a truncation phase error; obtaining data of each receiving array element after micro-Doppler phase error compensation; obtaining all receiving array element data after micro-range migration error correction; obtaining data of the class receiving and transmitting combined synthetic aperture sonar; obtaining N data blocks after truncation phase error compensation; obtaining multi-receiving array element synthetic aperture sonar data; filtering to obtain filtered data; obtaining the data after the nonlinear frequency modulation processing; calculating an accurate phase; obtaining a system frequency modulation rate after second-order Taylor series approximation; calculating a coefficient of the expression of the delay time and the distance direction frequency; solving an undetermined coefficient; performing high-order phase error compensation; and a high-resolution synthetic aperture sonar image is obtained. According to the method, the reconstruction performance can be effectively improved under the conditions of larger transmission signal bandwidth and larger accumulated beam angle.

The application discloses a kind of high-efficiency motorized weak target long-time coherent accumulation detection methods, belong to radar target detection field;Including the three-scale decomposition of motorized target radial motion parameter variable;In target blur scale motion parameter variable search space eliminates Doppler frequency blur effect;Through Keystone conversion correction first-order range migration caused by motorized target baseband speed;In target coarse scale baseband motion parameter variable search space, estimate motorized target coarse scale baseband motion parameter by GIFT conversion;In target fine scale baseband motion parameter variable search space, estimate motorized target fine scale baseband motion parameter, obtain temporary range-doppler spectrum;According to motorized target motion parameter variable three-scale decomposition model, estimate the complete motion parameter of motorized target;Based on motorized target motion parameter estimation, obtain motorized target range-doppler spectrum.The method has the characteristics of low computational complexity, Doppler blur effective compensation, high detection performance.

The invention discloses a method for imaging a space target by a space-based ISAR (inverse synthetic aperture radar), and relates to the field of inverse synthetic aperture radar imaging, in particular to the method for imaging the space target by the space-based ISAR. The invention aims to solve the problem that high-precision imaging is difficult to realize due to high-order space-variant range migration and phase error caused by complex relative motion and large-bandwidth signals between a target and a platform in a space target imaging process of a space-based ISAR (Inverse Synthetic Aperture Radar). The method comprises the following steps of: 1, acquiring a target slant distance and a radar sight observation angle according to orbit information of a satellite-borne platform, orbit information of a space target and a narrow-band tracking system of the satellite-borne platform; obtaining a radar sight line unit vector based on the radar sight line observation angle; 2, constructing a translational motion compensation item based on a target slant distance, and calculating an imaging compensation coefficient based on a radar line-of-sight unit vector; and 3, performing translational motion compensation by using the translational motion compensation item, performing rotational motion compensation by using the imaging compensation coefficient, and finally obtaining an imaging result.

This invention discloses a method for detecting and suppressing azimuth blur in spaceborne SAR scene matching curve imaging, comprising: 1. Modeling the azimuth blur, providing analytical expressions for the azimuth blur echo, range migration correction, and azimuth phase compensation terms; 2. Refocusing the nth-order azimuth blur based on the range migration correction and azimuth phase compensation terms; 3. Calculating the entropy difference between the SAR image and the nth-order blurred refocused image in blocks, and using the CFAR algorithm to detect blurred regions; 4. Filtering using a Wiener filter to generate a low-blur, low-resolution image; and combining the azimuth blur region detection results, replacing the detected sub-blocks to obtain a low-blur, high-resolution image. This invention can solve the azimuth blur problem in spaceborne SAR scene matching curve imaging mode, effectively improving image quality while preserving the resolution of the original image.

The invention discloses a space-time quick forward-looking imaging method for a forward-looking array radar of a motion platform, which comprises the following steps of: firstly, recording forward-looking area echoes by a multi-channel radar system based on a track cutting direction, and sampling to obtain distance-pulse-channel three-dimensional echo data; performing range-direction high-resolution processing, pulse compression and range migration correction on the data; traversing each range gate, performing azimuth Fourier transform on each frame-multichannel space-time two-dimensional data, intercepting a dominant Doppler unit greater than an energy threshold in a Doppler spectrum, and performing inverse Fourier transform to a time domain, namely performing dimension reduction processing in the Doppler domain; then, rank reduction processing is carried out based on the low-rank characteristic of the covariance matrix, and the energy of the signal is reserved through principal component analysis; and finally, estimating the position and amplitude information of the target through an adaptive iteration algorithm, and carrying out projection to obtain a final two-dimensional imaging result. According to the method, while the foresight resolution is effectively improved, the calculation complexity is remarkably reduced, and the operation efficiency is greatly improved.

There is a need to address the problem of compressed scanning in SAR acquisitions for microwave imaging. Embodiments of the present disclosure provide microwave imaging with multiple-input and multiple-output synthetic aperture radar using compressed multi-coset range migration technique. The present disclosure reduces the SAR acquisition time by compressed scanning, where a compressed scanning acquisition setup captures radar measurements to obtain a microwave image of a target scene by intermittently skipping blocks during SAR acquisition. Further, reconstruction of a microwave image of a target scene is performed using 2D Fourier Transform (FT) of the radar measurements based on a multi-coset range-migration framework. The multi-coset range migration framework makes use of intermittent scanning and formulates a compressed sensing-based architecture by leveraging block-sparsity constraints. Subsequently, a denoising convolutional neural network (DnCNN) is used to enhance and denoise the reconstructed microwave image to obtain a high-resolution image of the target scene.

This invention provides a frequency domain imaging method for spaceborne large-angle high-resolution sliding convergence SAR, achieving high-precision imaging of spaceborne large-angle high-resolution sliding convergence SAR. This invention solves the problem of nonlinear variation of the Doppler center of each target point with azimuth time by nonlinear deskewing, and solves the problem of inconsistency of azimuth spatial variables of range migration at different range gates by azimuth resampling, thus making up for the shortcomings of the prior art.

The application provides a long-time phase accumulation method with combined constraints of operation complexity and detection probability, belongs to the technical field of radar detection, and is mainly used for solving the range-Doppler migration problem of a radar when the radar is used for gazing at a weak maneuvering target. The application adopts Keystone transformation to eliminate range migration, optimizes the number of acceleration channels under the combined condition constraints of operation complexity and detection probability, and adopts double-stage acceleration channel fine Doppler demodulation technology to eliminate Doppler migration based on the optimization, so that long-time phase accumulation is realized.

The invention belongs to the field of radar signal processing, discloses a method for acquiring a one-dimensional range profile of a high-speed moving target by sub-pulse linear frequency modulation emission and inter-pulse frequency agility radar, and realizes frequency agility waveform echo high-speed target detection and correction based on sparse representation. In the prior art, distance and Doppler parameter estimation of target echoes can be generally realized by adopting sparse representation and sparse processing, and orthogonal matching pursuit (OMP) is one of common solution algorithms. The carrier frequency of a frequency agility radar jumps randomly between pulses, and the acquisition of a one-dimensional range profile of a high-speed moving target not only needs to correct inter-pulse range migration, but also needs to compensate intra-pulse range-Doppler coupling generated by the change of the carrier frequency. According to the method, firstly, compensation of intra-pulse distance-Doppler coupling is carried out, then distance migration correction is carried out on each frequency agility pulse based on a KeyStone method, sparse processing is carried out on a corrected echo signal by adopting an orthogonal matching pursuit algorithm, and a high-resolution one-dimensional distance image of a target is obtained. Experimental results show that the one-dimensional range profile processing method for performing inter-pulse range migration correction through the KeyStone algorithm is beneficial to target detection in high-speed motion.

The application discloses a kind of building thermal insulation layer bonding surface radar data acquisition methods, belong to radar data acquisition technical field, for building thermal insulation layer bonding surface data acquisition, including based on the principle of penetration imaging radar acquisition building thermal insulation layer bonding surface data, radar echo data is handled using range migration imaging and robust principal component analysis method, using edge detection method is connected and region filling to image edge, generate building thermal insulation layer bonding surface binary image, based on the method of the application builds building thermal insulation layer bonding surface radar data acquisition experimental platform.The application is collected to building thermal insulation layer bonding surface by radar data, and radar echo and image are optimized, provide scientific basis for evaluating the structural stability and potential risk of bonding layer, improve radar data acquisition precision and image definition;Building thermal insulation layer bonding surface radar data acquisition experimental platform is designed, realizes the method of collecting building thermal insulation layer bonding surface data in laboratory environment.

The application relates to a large downward-viewing-angle unmanned aerial vehicle (UAV) SAR motion compensation method based on an improved PGA algorithm, which comprises the following steps: performing inertial navigation coarse compensation and distance compression on echo signals to obtain first echo signals; performing non-space-variant phase error estimation on the first echo signals to obtain Doppler frequency modulation; performing non-space-variant range migration correction and coarse compensation of phase error on radar data according to the non-space-variant phase error to obtain a non-space-variant phase function after coarse compensation; estimating space-variant phase error, performing compensation processing according to the space-variant phase error, and obtaining a compensated space-variant phase function; splicing the compensated space-variant phase functions of all sub-apertures to obtain a full-aperture phase error; removing an overall linear component in the full-aperture phase error through linear fitting to obtain radar data after motion compensation; and performing imaging on the radar data after motion compensation by using a UAV SAR imaging algorithm to obtain imaging results. The application can accurately correct phase errors caused by distance space variation.

The application provides a SAR deception jamming method of mixed domain efficient track deviation compensation, comprising the following steps: after a SAR radar enters a detection range of a jammer, relevant parameters of the SAR radar are acquired, and a jammer deception template is constructed according to false electromagnetic features generated in a SAR image by jamming; azimuth focusing and range migration compensation calculation are performed on the jammer deception template in an azimuth frequency domain, and then inverse Fourier transform in the azimuth direction is performed to obtain an initialization template; after the SAR radar enters a jamming area, real-time modulation is performed, track deviation compensation is performed on the initialization template after coupling term decomposition in the azimuth time domain, and a real-time SAR system correlation filter is constructed in the azimuth time domain pulse by pulse; the real-time SAR system correlation filter and the jammer correlation filter are multiplied in a range frequency domain to obtain a non-linear track jamming frequency domain response function, and convolution operation is performed on the non-linear track SAR deception jamming signal obtained after the SAR signal intercepted to obtain a non-linear track SAR deception jamming signal.

The present application belongs to the technical field of radar moving target imaging, and particularly relates to a terahertz circular SAR moving target parameter estimation and refocusing method. The present application reduces two-dimensional coupling in the range and azimuth by dividing sub-apertures, performs range compression on the echo under each sub-aperture by performing inverse Fourier transform in the range direction and after slant correction, estimates the Doppler center by using the spectral peak measurement method and combining the shadow position, estimates the Doppler frequency by using the fractional Fourier transform, estimates the along-track speed and radial speed information of the moving target according to the estimated results, constructs a first-order and second-order phase compensation function, corrects the azimuth direction offset, partial defocusing and additional range migration, and compensates the residual quadratic and higher-order phase by using the phase gradient autofocus algorithm. The refocusing effect of the moving target in the simulation data verifies the effectiveness of the present method.

The present application belongs to the field of radar signal processing and radar imaging technology, and proposes a real-aperture scanning radar forward-looking super-resolution imaging method based on non-convex sparse and generalized total variation joint constraint: the system parameters of the real-aperture scanning radar forward-looking imaging are initialized, and the radar forward-looking scanning echo data are obtained; the radar forward-looking scanning echo data are sequentially subjected to range direction pulse compression and range migration correction; the range direction echo data of the target are extracted, and a range direction convolution observation model is established; a non-convex sparse constraint and generalized total variation joint regularization optimization problem is constructed; the non-convex sparse constraint and generalized total variation joint regularization optimization problem is solved, the target scattering coefficient estimation result is obtained, and the radar forward-looking super-resolution imaging result is output. The present application can simultaneously consider the super-resolution recovery ability of point-like scattering targets and the structure maintaining ability of extended targets, and improves the stability and reconstruction precision of the real-aperture scanning radar forward-looking super-resolution imaging.

The application discloses a kind of based on physical consistency modeling multiple scattering SAR imaging simulation method, system, equipment and medium, including the following steps: constructing the three-dimensional electromagnetic model of target;Geometric model under the condition of transmitting-receiving co-located SAR operating mode is constructed by light ray tracing;Using high-frequency electromagnetic scattering algorithm based on ray tracing, considering first-order, second-order and higher order multiple scattering path, the superposition and amplitude modulation of each order scattering contribution are carried out, the scattering field distribution of target under far-field condition is calculated, and the far-field scattering field is obtained;Total far-field scattering field is mapped by space propagation, and the far-field scattering result is mapped as radar platform near-field echo signal;Echo signal amplitude is corrected, and two-dimensional SAR near-field echo matrix is obtained;SAR imaging processing is carried out, and SAR imaging processing includes range compression, range migration correction RCM and azimuth compression.The application improves the fidelity and accuracy of SAR imaging simulation under complex target scene.

This invention provides a high-frequency signal processing method for a submarine pipeline SAS monitoring system, relating to the field of signal processing. This method acquires the original echo signal and transforms it to the range frequency domain. It then uses the phase characteristics of the submarine pipeline target in the echo to invert and correct the sound velocity parameters of each layer in a layered medium model, establishing a sound velocity recursive relationship. The method calculates the one-way propagation time corresponding to different range frequencies, obtains the equivalent frequency modulation parameter through numerical difference, and constructs a phase correction value in the range frequency domain to compensate for the nonlinear distortion of the range migration curve caused by sound velocity layering. After range compression, it calculates the actual propagation time sequence at different azimuth times based on the time delay-frequency relationship, and constructs correction coefficients through azimuth frequency domain group delay analysis to compensate for azimuth phase distortion. This invention achieves physical matching compensation for signal distortion caused by layered media, significantly improving the focusing performance and geometric fidelity of submarine pipeline SAS images.

The invention relates to the technical field of millimeter-wave radar target detection, in particular to a millimeter-wave radar efficient coherent accumulation method for engineering implementation, which comprises the following steps: S1, acquiring a radar echo data matrix, and segmenting the radar echo data matrix; s2, based on fast Chirp-Z transformation, performing in-subsegment range migration and Doppler frequency modulation efficient correction and compensation, and realizing in-subsegment coherent accumulation of target energy; s3, constructing a distance and azimuth unified nonlinear compensation function based on the distance and azimuth coupling relationship between the sub-segments, completing accurate compensation of migration and Doppler frequency modulation between the sub-segments, and then performing coherent accumulation between the sub-segments to obtain a target accumulation result; according to the invention, the calculation complexity is reduced and the parallel processing capability is improved; accurate compensation of inter-segment migration and modulation is completed based on an inter-segment distance orientation coupling relationship; the traditional technical means of parameter search and interpolation operation is replaced by fast Chirp-Z transformation, so that the operation efficiency is remarkably improved, and the storage requirement is reduced.

This invention discloses a super-resolution forward-looking imaging method for real-aperture scanning radar, relating to the field of radar technology. The method includes: establishing an echo signal model in the forward-looking imaging mode of a real-aperture scanning radar; performing pulse compression and range migration correction on the target echo signal obtained from the echo signal model to obtain a pre-processed target echo signal; correcting beam distortion of the existing echo signal model using a block approximation method, transforming the spatially variable convolution matrix into a locally spatially invariant Toeplitz matrix; and combining the beam-distortion-corrected echo signal model with the Gaussian maximum a posteriori algorithm and introducing the Barzilai-Borwein method to adaptively adjust the iteration step size to achieve super-resolution imaging. This solves the problem of insufficient azimuth resolution in forward-looking imaging and improves the signal-to-noise ratio of the imaging results.

This invention discloses a robust detection method and system for high-speed, highly maneuverable targets based on Radon-LVD transform, belonging to the field of radar signal processing. The method estimates the target's velocity and acceleration from the pulse-compressed echo signal using Radon-LVD transform; constructs a slow-time-range frequency domain quadratic phase compensation function using the velocity and acceleration estimates; performs migration compensation on the slow-time-range frequency domain of the echo signal; and then performs moving target detection in the range-Doppler domain. The two searches during this process improve the accuracy of target parameter estimation. This invention combines Radon transform and LVD transform, which can compensate for range migration and Doppler migration respectively, achieving coherent accumulation of energy in the echo signal of a uniformly accelerated target.

The application discloses a radar weak target multi-mode motion parameter estimation and coherent accumulation method, which comprises the following steps: S1, performing pulse compression on the radar echo of a maneuvering target along the distance direction to obtain an echo signal; S2, dividing the echo signal in a CPI based on a short-time window to obtain a sub-CPI signal; S3, correcting the range migration of the signal in the sub-CPI by using a short-time Keystone transformation, and extracting a range signal in the azimuth direction; S4, performing a short-time fractional Fourier transformation on the range signal in the azimuth direction, estimating the instantaneous motion parameters in the sub-CPI, estimating the motion mode conversion time based on the instantaneous motion parameters in the sub-CPI, and obtaining the number of motion modes and the motion parameters in each mode; and S5, constructing a phase compensation function according to the motion parameter estimation, compensating the range migration and Doppler migration in the original echo, and realizing long-time coherent accumulation. The application avoids high-dimensional search of parameters, has low calculation complexity, high calculation efficiency, and good engineering application prospect.

This disclosure relates generally to a method and system for local interpolation function (LIF) based synthetic aperture radar (SAR) imaging for irregular scanning geometries. Current available methods are computationally expensive, sensitive to initialization and lacks generalization, particularly when applied across sampling schemes in continuous sampling scale scenarios which is a key characteristic of irregular scanning geometries. The present disclosure achieves enhanced SAR image across various spatial coordinates. Noisy SAR images are obtained using Non-uniform Fast Fourier Transform (NUFFT) based Range Migration Algorithm (RMA). The noisy SAR image is mapped into a LIF feature map using an encoder of a trained LIF neural network. An enhanced SAR image is further predicted based on the LIF feature map using a decoder of the LIF neural network. The disclosed method for SAR image enhancement using LIF neural network is used for supply chain management, airport security screening, medical imaging and so on.