38 results about "Doppler bandwidth" patented technology

The invention discloses a DCS algorithm-based satellite-borne video SAR (synthetic aperture radar) imaging processing method. The method includes the following steps that: 1, satellite-borne SAR beam bunching mode echo simulation data and corresponding parameters are read; 2, Doppler bandwidth and synthetic aperture time required by frame images are determined; 3, a data partitioning mode is determined, and data are partitioned; 4, de-sloping processing is performed on frame segment data in an azimuth direction; 5, signals obtained after the de-sloping processing are subjected to azimuth-direction Fourier transform, multiplied by an CS factor, subjected to range-direction Fourier transform, and multiplied by a range-direction compensation factor sequentially; 6, the phase difference between the center slope distance of each frame of data and the center slope distance of the entire echo data is compensated; 7, range-direction Fourier transform, azimuth-direction compensation processing, azimuth-direction inverse Fourier transform are performed, so that an imaging result can be obtained; 8, step 4 to step 7 are repeated, so that all frame images can be obtained; and a video SAR product can be obtained. With the DCS algorithm-based satellite-borne video SAR imaging processing method of the invention adopted, the resolutions of the frame images can be consistent.

The invention discloses a high-resolution imaging method for radar based on multi-beam scanning, and is applied in the field of radar imaging. The method comprises the steps: forming a plurality of received subbeams through the digital beam forming technology, and enabling the received beams to employ a folding-fan working mode for the scanning of a front view region, thereby reducing the front view Doppler fuzzy region. Meanwhile, the bigger Doppler bandwidth is obtained through the echo overlapping of multiple beams, thereby improving the target azimuth resolution of a big front view region of an airborne platform, and achieving the large-range high-resolution imaging of the big front view region of a radar. The method proposed by the invention can be used for solving a problem of inherent conflicts between the resolution and the front view imaging blind region in the conventional Doppler beam sharpening technique.

The invention provides an SAR motion target detection method based on Doppler spectral analyses. The SAR motion target detection method based on Doppler spectral analyses is used for detecting ground motion targets in an SAR picture, and mainly solves the problem that an existing detection method is not high in detection probability so as to improve detection probability. According to the method, rectangular neighborhoods of scattering points in the SAR picture are chosen, clutter lock is conducted on Doppler frequency spectrums in each neighborhood to acquire Doppler center frequency, and then standard deviations of frequency spectrums after clutter lock are calculated to represent Doppler bandwidths. Traversal is conducted on all scattering points in the SAR picture, the scattering points are processed in the same way, statistics is then carried out, a measure is constructed through obtained statistics to ensure that the detection boundary of the measure is an oval, and a detection threshold is determined according to constant false alarm rate (CFAR). Because the detection boundary is an oval, on the premise that the constant false alarm rates are the same, oval detection boundary detection probability is larger than rectangle detection boundary detection probability, and target missing detection does not occur easily.

The invention discloses a subaperture wave number domain imaging method for a squint sliding spotlight SAR (Synthetic Aperture Radar). A traditional sliding spotlight SAR subaperture method is improved aiming at squint conditions. The subaperture wave number domain imaging method comprises the following steps: firstly, overlapping a whole aperture and dividing subapertures; taking an extended wave number domain method used for the squint conditions as a subaperture basic imaging method; and finishing azimuth processing in a distance Doppler domain by adopting an improved BAS method to splice the subapertures, so as to obtain a whole aperture image under the squint conditions. With the adoption of the subaperture wave number domain imaging method, the problems of the squint sliding spotlight SAR of large data size, non-zero azimuth Doppler center and oversized Doppler bandwidth are solved, and the practical value is larger.

The invention provides an azimuth parameter obtaining method for a satellite-borne synthetic aperture radar in a sliding bunching mode. An azimuth initial imaging belt length, an antenna beamwidth, an initial squint angle, a terminate squint angle and a target slant distance are utilized to establish a reference slant distance model corresponding to a beam rotation center; reference slant distance data are obtained, and an effective irradiation time model corresponding to a point target is established according to the reference slant distance data; effective initial irradiation time and effective terminate irradiation time of the point target are obtained, and an effective Doppler frequency and Doppler bandwidth model corresponding to the point target is established according to the effective initial irradiation time and effective terminate irradiation time of the point target; initial effective Doppler frequency, terminate effective Doppler frequency, the Doppler bandwidth and the resolution declining coefficient corresponding to the point target are obtained, an azimuth resolution model corresponding to the point target is established according to the initial effective Doppler frequency, terminate effective Doppler frequency, the Doppler bandwidth and the resolution declining coefficient corresponding to the point target, and the azimuth resolution corresponding to the point target is obtained; when the azimuth resolution is larger than a resolution index requirement, the maximum azimuth imaging belt length datum is output.

The invention belongs to the field of radar technology, and discloses an azimuth multichannel SAR signal adaptive reconstruction method. The method comprises the steps of acquiring a two-dimensional spectrum of echo data which are received by each channel; obtaining a corresponding multichannel data matrix by means of the two-dimensional spectrum and obtaining a corresponding covariance matrix for each base band frequency in a base band frequency range; constructing a corresponding first guiding vector at each Doppler frequency in a Doppler frequency range, and furthermore calculating N Doppler spectrums at the Doppler frequency by means of the first guiding vector and a covariance matrix which corresponds with each base band frequency, determining a base band Doppler center and an effective Doppler bandwidth by means of N Doppler spectrums at each Doppler frequency, obtaining a fuzzy component number according to the base band Doppler center and the effective Doppler bandwidth at each base band frequency, and a signal matrix at the base band frequency is reconstructed by means of the fuzzy component number. The azimuth multichannel SAR signal adaptive reconstruction method can keep integrity of the Doppler spectrum and improves signal-to-noise ratio of the reconstructed signal.

The invention discloses a land-sea clutter classification method based on time domain and frequency domain multi-features. The method comprises the following steps: 1, calculating normalized power variance, Doppler bandwidth, Doppler spectrum entropy and Doppler spectrum peak power ratio of echoes of a single radar spatial resolution unit; 2, generating feature data and category data of ground clutter and sea clutter based on the step 1; 3, constructing a BP neural network; 4, calculating normalized power variance, Doppler bandwidth, Doppler spectrum entropy and Doppler spectrum peak power ratio of each spatial resolution unit in a radar detection scene; and 5, performing judgment according to an output result. According to the land-sea clutter classification method based on time domain and frequency domain multi-features, land and sea clutter classification of different motion platform radars can be realized.

The invention discloses a method and device for determining the effective Doppler bandwidth of a fuze receiver. The method comprises the steps of dividing a target into multiple target scattering surface elements after geometric modeling is conducted on the target, calculating the Doppler shift of each target scattering surface element and the echo power generated by each target scattering surface element under the missile target encounter condition, drawing a Doppler frequency spectrum diagram of the target according to the calculated Doppler shift and echo power of each target scattering surface element, and cutting out a spectral line range within which echo power is larger than set threshold power from the drawn Doppler frequency spectrum diagram and determining the effective Doppler bandwidth of the fuze receiver according to the cut-out spectral line range. By the adoption of the method and device, estimation of the effective Doppler bandwidth of the fuze receiver can be achieved, so that the fuze receiver can be designed based on the estimated effective Doppler bandwidth of the fuze receiver during fuze slideway testing, and then fuze slideway testing is facilitated.

The invention relates to a ship target interference detection method based on a satellite-borne Ka-band SAR (Synthetic Aperture Radar) system, which comprises the following steps of: scanning orthogonal signals of a pulse repetition period in an imaging area by using a Ka-band transmitting antenna to realize coverage of large width and large Doppler bandwidth; before pulse emission, a Ka wave band receiving antenna is used for carrying out parallel receiving and digital beam forming recovery on echo signals with large breadth and large Doppler bandwidth, and direction sources of interference signals are obtained; receiving data of a Ka-band receiving antenna is subjected to weighting processing to control a direction function, a nulling technology is used in the direction of an interference signal, the interference signal is suppressed, and interference caused by a sidelobe strong target of the Ka-band receiving antenna is suppressed at the same time; and obtaining an interference SAR image of the imaging area by using the Ka-band SAR cross-rail baseline, extracting elevation winding distribution information, and detecting and identifying the ship target according to the elevation winding distribution characteristics of the ship target. The ship target detection and recognition performance can be improved.

The invention discloses a synthetic aperture radar (SAR) azimuth signal reconstruction method. The method comprises the following steps of according to a first channel transfer function matrix, determining a signal to noise ratio (SNR) amplification factor of the first channel transfer function matrix, and according to the SNR amplification factor, determining an equivalent Doppler bandwidth; according to the equivalent Doppler bandwidth and the first channel transfer function matrix, determining a second channel transfer function matrix corresponding to each Doppler frequency point; according to the second channel transfer function matrix corresponding to each Doppler frequency point, a pre-measured aliasing frequency spectrum and an original frequency spectrum corresponding to the aliasing frequency spectrum, determining a frequency spectrum filter extracting a Doppler frequency spectrum. The frequency spectrum filter is used for extracting the Doppler frequency spectrum in an azimuth signal. The invention simultaneously discloses a SAR azimuth signal reconstruction apparatus.

The invention discloses a sparse representation-based doppler beam sharpened imaging method and device. The method comprises the following steps of carrying out matched filtering processing on an echo signal received in a range direction, carrying out range migration correction on the processed data; carrying out related function method processing on the data subjected to range migration correction and determining a mean value to obtain a doppler center value; carrying out doppler center compensation on the data subjected to range migration correction to obtain doppler center compensation data; carrying out DBS imaging on the doppler center compensation data and calculating the noise power level; constructing a hypercomplete sparse dictionary according to a doppler frequency resolution and carrying out sparse recovery on the doppler center compensation data; and extracting data corresponding to a doppler bandwidth from the sparse data in a range doppler domain by adopting a linear interpolation method, converting the extracted data into a geodetic coordinate by taking a first group of data as a criterion and sequentially splicing the extracted data until obtaining a wide-area monitoring image. The method has a relatively high transverse resolution.

The invention relates to an airborne synthetic aperture radar self-focusing method. According to the method, a channel cross correlation model is established in a noise-ignoring multichannel convolution model, an underdetermined homogeneous linear equation set about the ideal data is acquired, unknown parts exceeding doppler bandwidth partially realize zero setting, a non-zero solution is acquired, frequency spectrum leakage and additive noise are considered, singular value decomposition for a coefficient matrix is carried out, a unique solution under the Euclidean norm is acquired, the ideal data of zero is partially combined with the unique solution, the integral ideal data after recovery is acquired, and azimuth compression for the ideal data is carried out to acquire a focusing image. Through the method, an SAR imaging scene has not any hypothesis, good robustness is realized, the method can be applicable to any SAR imaging scenes, derivation under a theory framework of linear algebra is directly carried out, phase error estimation and compensation without iteration can be carried out to realize focusing of an SAR image, and thereby estimation and compensation of motion errors of the airborne synthetic aperture radar echo data can be effectively realized.

The invention discloses a geographical stripe SAR variable interval pulse sequence design method, which comprises the following steps: 1) providing imaging geometry of a platform and a target stripe, and calculating an initial center slope distance and a final center slope distance; 2) providing azimuth Doppler bandwidth and carrying out calculation to enable echo window time to be longest and meet initial pulse interval of whole-process non-aliasing sampling; and 3) substituting the initial pulse interval and the center slope distance course, calculating emission time of each pulse according to a recursion formula and obtaining all pulse sequences. The method can prevent the problem of pulse sheltering under the premise of enough sampling rate, and can carry out continuous imaging on stripes not parallel to platform trajectory and prevents transmission pulse shielding.