115 results about "Azimuth compression" patented technology

Motion measurement errors that extend beyond the range resolution of a synthetic aperture radar (SAR) can be corrected by effectively decreasing the range resolution of the SAR in order to permit measurement of the error. Range profiles can be compared across the slow-time dimension of the input data in order to estimate the error. Once the error has been determined, appropriate frequency and phase correction can be applied to the uncompressed input data, after which range and azimuth compression can be performed to produce a desired SAR image.

The invention discloses a bistatic synthetic aperture radar (BSAR) frequency domain imaging method which specifically comprises the following steps of: initializing parameters of an imaging system; calculating a point target echo two-dimensional spectrum; performing rough matching focusing on a TV-BSAR by utilizing a reference point two-dimensional spectrum; performing Taylor expansion on the slope distance of a transmitting station, and combining residual phase terms; performing azimuth-to-frequency Stolt transform; performing distance-to-frequency Stolt transform; and performing two-dimensional inverse Fourier transform. The method disclosed by the invention adopts the two-dimensional Stolt frequency transform which enables the echo phase after rough focusing of the BSAR in a shift variant mode to finish the linearization of the airspace and frequency domain, thereby finishing residual distance migration correction, residual secondary distance compression and residual azimuth compression. The method effectively solves the two-dimensional space-variant problem in a shift variant bistatic mode, thereby realizing the precise focusing imaging of the BSAR in a shift variant mode.

The invention discloses a signal processing method of a satellite-bone sliding spotlight synthetic aperture radar. The method includes: performing molecule aperture processing on original echo data of the sliding spotlight synthetic aperture radar (SAR); performing range compression and range migration correction through a chirp scaling (CS) algorithm; introducing squint angle compensation in theCS algorithm; compensating scene space-variant performance; adjusting range migration amount of all sub-apertures to be identical with Doppler parameters of full apertures in CS scalar variable factors as the standard; performing azimuth compression and quadratic term compensation in the frequency domain, and performing frequency modulation processing in the time domain; splicing data of all the sub-apertures and restoring resolution ratio of the full apertures; and enabling signals to have phase preservation performance through spectrum analyzer (SPECAN) processing. By adopting the signal processing method, imaging quality can be improved under the condition of large scene squinting.

The invention relates to a maneuvering target ISAR imaging method, and belongs to the field of radar signal processing. The method comprises the following steps of: 1) realizing pulse compression through matched filtering according to baseband echoes received by a radar to generate a one-dimensional range profile sequence; 2) performing motion compensation on the one-dimensional range profile sequence; 3) performing cross-distance unit migration correction on the one-dimensional distance image sequence subjected to motion compensation by adopting keystone transformation; 4) according to the measurement information of the radar, obtaining a cumulative rotation angle change curve of the target in the imaging period, and performing second-order fitting to obtain an equivalent rotation angularvelocity and an angular acceleration value; 5) constructing a primary function matched with Fourier transform according to the equivalent rotation angular velocity and the angular acceleration valueof the target; and 6) performing MFT on each distance unit of the one-dimensional distance image after the cross-distance unit migration correction, and completing azimuth compression to obtain an ISAR two-dimensional image. According to the invention, by constructing an MFT primary function and performing MFT on each distance unit, the ISAR image of the maneuvering target is obtained, the steps are simple, and the imaging quality is high.

The invention discloses a bistatic forward-looking SAR (Synthetic Aperture Radar) motion compensation method. Azimuth-slow time decoupling operation is adopted, and different azimuth point targets in the same distance unit are separated and processed. The method mainly comprises steps of: (1) space-invariant motion error compensation; (2) distance focus processing; (3) distance space-variant motion error compensation; (4) azimuth space-variant motion error compensation; and (5) azimuth compression. The problem that the traditional SAR motion compensation method and the existing bistatic SAR motion compensation method are hard to correct motion error azimuth space variance can be overcome. The motion error azimuth space variance can be effectively removed, and precise compensation and focusing of the bistatic forward-looking SAR can be realized.

The invention discloses a large-squint high-resolution SAR imaging method based on a distance-azimuth circle model. The method comprises the following steps: 1, constructing an SAR system geometric model to obtain an echo signal; 2, carrying out the range direction preprocessing of the signal in a frequency domain; 3, constructing the distance-azimuth circle model according to a range direction preprocessing result, and describing the azimuth space-variant characteristics of the SAR signal; 4, modeling an azimuth space-variant part in a remaining high-order RCM through a result given by the distance-azimuth circle model, and constructing a new variable-scale function to implement QRCMC, and then designing a distance compressing filter and completing all the processing in the distance direction; 5, modeling the azimuth space-variant characteristics of a Doppler phase according to the distance-azimuth circle model, achieving azimuth equalization through using an ENLCS algorithm, finallydesigning a filter for azimuth compression, and obtaining a final focused image. The method has a better focusing effect during the processing of large-squint and high-resolution echo data.

The invention discloses a time division ground-based MIMO landslide radar imaging method based on IFFT and mix-match pursuit, and aims to solve the problems that an existing mountain landslide monitoring field imaging method is high in data processing complexity and uses too many antennas; aiming at a multi-target imaging pseudo shadow point problem, the method introduces the mix-match pursuit algorithm, thus greatly improving the imaging quality; the method comprises the following steps: building an equivalent random sparse transmit-receive array; building an echo signal acquisition model; range direction compression treatment; azimuth compression treatment; finishing two dimension object high resolution imaging. The advantages are that the method can reduce the array quantity, can reducehardware cost, can reduce the data processing complexity, and can improve the range and azimuth resolutions.

The invention discloses a three-dimensional focal imaging method of a look-down array antenna synthetic aperture radar, which relates to radar technology. The method comprises: A) performing slant-range compression of collected original echo data of the look-down array antenna synthetic aperture radar; B) performing azimuth range migration correction of a signal obtained by the step A); C) performing the azimuth compression of a signal obtained by the step B); E) performing the ground-range range migration correction of the signal which is subjected to slant-range compression and azimuth compression; and F) performing the ground-range slant removal and ground-range Fourier transform of the signal obtained by the step E), and reestablishing the three-dimensional radar image of an imaged area in a cylindrical coordinate system. In the method of the invention, fewer antenna array elements are used for reestablishing the three-dimensional radar image of the imaged area, the range migration correction problem, which is not solved in the conventional three-dimensional imaging method, is solved, the ground-range wave beam forming calculation performed in the conventional three-dimension imaging method is converted into one time of complex multiplication and the Fourier transform, and a three-dimensional resolution image is thus acquired, and the required imaging time is reduced.

The invention discloses an improved RDA-based method for inhibiting a synthetic aperture radar image target side lobe. In order to obtain a super-resolution SAR image, the method comprises the following specific processing steps of azimuth direction Fourier transformation of a two-dimensional echo signal, complementary migration correction, distance direction Fourier transformation, consistent migration correction and distance compression, distance direction inverse fast Fourier transformation, additional phase correction, azimuth direction inverse Fourier transformation and azimuth compression of a fusion inversion matrix. Compared with conventional imaging processing modes of matched filtering and the like, the processed imaging result energy is more concentrated, the space resolution ratio is significantly improved, and the super resolution target is achieved. Compared with a complete matrix-based SAR data processing, the method disclosed by the invention is combined with a high-efficiency traditional imaging algorithm, so that the processing efficiency is significantly improved.

The invention discloses an adjacent space slow platform synthetic aperture radar big scene imaging method. The method particularly comprises the following steps: according to the principle that time domain convolution of two signals is equivalent to frequency domain multiplication, convoluting the boost echo and the dechirp reference signal in the orientation time domain, and converting the result to obtain the Doppler domain, multiply a compensating factor in the Doppler domain to accomplish the Doppler aliasing step, overcome Doppler aliasing problem, and obtain the echo signal with non-aliased frequency domain; conducting reference phase function multiply in the two-dimensional frequency domain to accomplish consistent compression, and accurately accomplish residual distance ACTS nmo correction, secondary range compression and residual azimuth compression through Stolt interpolation, so as to accomplish focusing; obtaining the distance and orientation two-dimensional time domain focused image through orientation time domain aliasing step; obtaining the boost image, splicing to form a continuous wide surveying and mapping band image output. The method provided by the invention has the advantages of being high in surveying and mapping band width and imaging algorithm accuracy.

The present disclosure provides an imaging method for a Synthetic-Aperture Radar (SAR) in a high squint mode. The method includes: perform perturbation function multiplication for an echo signal in the azimuth Doppler domain-range time domain to eliminate the dependence of an echo signal quadratic azimuth-range coupling factor on the change of a target slant range; perform reference function multiplication in the two-dimensional frequency domain, wherein the reference function is a conjugate function of a point target echo spectrum at a reference slant range; complete compensation of all phases, which do not vary with the range, of a two-dimensional spectrum through the multiplication of the two-dimensional spectrum and the reference function; rectify the differential range migration factor of the echo signal in the two-dimensional frequency domain by utilizing Chirp-Z transform, complete range migration rectification by performing convolution once and phase multiplication twice; compensate an azimuth residual phase through the azimuth phase multiplication, and perform azimuth compression to obtain a focused SAR image. The method of the present disclosure can perform highly efficient and precise imaging for high squint SAR data.

The invention relates to a Legendre-orthogonal-decomposition-baesd curve motion trajectory SAR wave-number domain imaging method. The method comprises: constructing a slant range history expression ina curved motion trajectory mode by using a three-dimensional speed and a three-dimensional acceleration; carrying out polynomial expansion on the constructed slant range history expression and carrying out keeping to the fourth order; transforming an SAR echo signal corresponding to the slant range into a two-dimensional frequency domain to obtain a two-dimensional frequency spectrum; with a Legendre orthogonal polynomial, spreading the two-dimensional frequency spectrum for a distance range frequency and carrying out keeping to a third order; carrying out phase compensation based on a two-dimensional frequency spectrum developed based on Legendre and completing distance migration correction and distance range focusing; and carrying out azimuth compression in a distance-Doppler domain andcarrying out transformation in a two-dimensional time domain to obtain a focusing image. Therefore, a target imaging blurring problem at the scene edge is solved.

The invention discloses a full-resolution range model-based one-stationary bistatic SAR (synthetic aperture radar) imaging method. The method of the invention include the following steps that: 1, a one-stationary bistatic SAR system geometric model is accurately constructed, and echo signals are obtained; 2, range-direction pre-processing is performed on the signals in a range frequency domain; 3,a new full-resolution range model is constructed according to the result of the range-direction processing, and azimuth space-variation characteristics between point targets which are located on thesame range unit and distributed along an azimuth direction and the center distance of a receiver can be accurately described; and 4, accurate modeling is performed for the azimuth space-variation characteristics of complex Doppler phases according to the new full-resolution range model, and azimuth equalization is realized through an ENLCS algorithm, a filter is designed to perform azimuth compression, and a final focused image is obtained. The method of the invention enables a better focusing effect in processing the high-resolution echo data of a large-squint one-stationary bistatic SAR.

The invention provides a double-base imaging method based on navigation satellite signals. The method comprises the steps that range processing is carried out on an original echo; two-dimensional decoupling processing is carried out; range migration correction is carried out; azimuth compression processing is carried out; the echo obtained after azimuth compression processing is subjected to azimuth IFFT, and an imaging result of a two-dimensional time-domain midpoint target is obtained. The method has the advantage that in the double-station synthetic space radar imaging process based on thenavigation satellite signals, range compression, range migration correction, two-dimensional decoupling and azimuth compression processing are carried out; different from a conventional single-stationsynthetic aperture radar imaging SAR, range signals are no longer linear frequency modulation signals, but are binomial continuous waves, and range needs to obtain distinguishing performance according to correlation characteristics of C/A codes. According to the method, the double-base imaging quality can be obviously improved.

The invention discloses a method for three-dimensionally positioning target cooperatively formed images of a double-onboard SAR. The method comprises the steps that original echo data returned by a scene area is processed, and target scene imaging is completed through range direction compression, range migration correction and azimuth compression processing; double-parameter CFAR processing is conducted on two high-resolution SAR images respectively, target areas are detected out according to their geometrical characteristics, the geometric centers of the target areas are taken, and image point coordinates corresponding to target gray level areas are output; image point coordinate arrays are substituted into a positioning algorithm model, and coordinates of targets in a rectangular coordinate system are calculated by combining system parameters and directional parameters of two SAR through Newton iteration. Calculation can be directly performed after the image point coordinates of targets in images, accordingly the calculation quantity is greatly decreased, and real-timeliness is improved.

The invention relates to a polarization calibration method based on platform attitude time variation compensation. The method comprises steps that: S1, two-dimensional echo data is acquired; S2, scattering matrix observation values of a calibrator at one same irradiation time are extracted; S3, an incidence angle and an oblique angle of the calibrator irradiated by electromagnetic waves are acquired; S4, when the calibrator receives polarization calibration angles of the electromagnetic waves, deflection amount at each irradiation time is acquired; S5, full polarization echo data after attitude error compensation correction is acquired; S6, azimuth compression of the full polarization echo data after the attitude error compensation correction is carried out to acquire an image; and S7, scattering matrixes after calibrator deflection amount correction are extracted in each polarization channel of the image, an unbalance degree which is left over in the scattering matrixes after calibrator deflection amount correction and is led in by a transceiver module of a full polarization synthetic aperture radar system, and crosstalk in each channel are evaluated, error correction of the full polarization synthetic aperture radar system is realized, and the full polarization synthetic aperture radar image is acquired.

The invention provides an echo view registration method for a sub-aperture altimeter, which comprises the following steps of: multiplying a signal by a frequency scaling function to remove distance curved spatial variability; performing inverse fourier transform in a distance direction, multiplying by a conjugation of the inverse fourier transform of a certain function, namely a residual video phase correction function, and finishing residual video phase correction, namely 'deskew' processing; multiplying by an inverse frequency scaling function, namely eliminating a secondary phase error introduced by the frequency scaling function to finish scaling processing; multiplying the scaled signal by a linear phase function to perform distance migration correction so as to finish registration in a view distance direction; performing azimuth compression on an obtained sub-view of the view distance registration to obtain a compression sub-view corresponding to an aperture; and performing registration in an azimuth direction on all the obtained compression sub-views, and extracting each azimuth-registered equivalent sub-view unit for subsequent tracking estimation or imaging processing.

The invention discloses a geosynchronous orbit synthetic aperture radar (SAR) moving target imaging processing device based on time-frequency transformation and Doppler center correction. The geosynchronous orbit SAR moving target imaging processing device comprises a radar parameter output module, a migration correction and range compression module, a moving target detecting and parameter estimating module and a motion compensation and imaging processing module, wherein the radar parameter output module outputs working parameters of a radar and imaging parameters required for imaging processing; the migration correction and range compression module carries out range migration correction and range compression operation simultaneously on echoes under unknown target motion parameters according to the radar parameters output by the first module; the moving target detecting and parameter estimating module detects a moving target according to the difference between echo time-frequency features of the moving target and a static target, corrects the Doppler center according to frequency spectrum energy and estimates moving parameters; the motion compensation and imaging processing modulecompensates moving signals according to the moving parameters obtained by the third module and carries out azimuth compression to complete imaging.