51 results about "Keystone transform" patented technology

The invention discloses a ground moving target imaging method for a single-channel synthetic aperture radar (SAR). The method comprises the following steps of: (1) correcting distance curvature; (2) correcting distance migration; (3) estimating Doppler parameters; (4) estimating motion parameters; (5) compressing a direction; and (6) repeating the steps until all moving targets are processed. In the invention, the distance curvature of moving target echo data is corrected by second-order Keystone transform, so the method has the advantage of high-resolution SAR data imaging; by uniformly correcting the distance curvature of all stationary targets and all moving targets, the defect of large computation amount in the prior art is overcome; and by building a second-order moving target imaging model, parameter estimation and imaging of maneuvering moving targets can be performed, and the moving states of the moving targets can be more accurately described from aspects of speed, acceleration and the like.

The invention discloses an improved algorithm based on parameter estimation and compensation of a quadratic phase function, and belongs to the technical field of signal and information processing. Thealgorithm performs range walk correction on slow time-range frequency domain echo signal considering range walk and Doppler diffusion through Keystone transform, and then eliminates a coupling relation between the range frequency f and the slow time tn in a second-order phase item corresponding to the acceleration in a narrow-band condition; meanwhile, a folding factor corresponding to the blindspeed is searched, a folding factor compensation item is constructed to correct the range walk caused by the blind speed; then the target acceleration is estimated by using the quadratic phase function, and a second-order phase item corresponding to the acceleration is constructed to compensate Doppler diffusion of the echo signal; and finally, long-term phase-coherent accumulation is performed soas to realize high-speed weak target detection of bistatic radar. The method disclosed by the invention is high in operation speed, stable in performance and applicable to detection of weak targets with a low signal-to-noise ratio and difficultly estimated target parameters.

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 relates to a quick implementation method for passive radar range migration compensation and belongs to the technical field of radar target detection. The method comprises the following steps: (1) a direct wave signal and an echo signal received by a passive radar antenna are segmented and rearranged into two-dimensional matrices; (2) each row of the direct wave and the echo wave is transformed to the frequency domain; (3) the transformed direct wave matrix is multiplied by the conjugate transpose of the transformed echo wave matrix; (4) each row is extracted after being processed by a low-pass filter; (5) each column is subjected to CZT; and (6) each row is transformed to the time domain, and a cross-ambiguity function result subjected to migration compensation is obtained. Compared with a conventional range migration compensation method based on CZT and IFFT to achieve keystone transform, the provided method reduces operation steps and the amount of computation substantially while the gain accumulated is almost the same.

The invention discloses a high-speed maneuvering target detection method based on discrete linear frequency modulation Fourier transform. The method comprises the steps that 1 a radar echo is received, and demodulation and pulse pressure processing are carried out on the radar echo; 2 in the fast time domain, Fast Fourier transform and Keystone transform are carried out on the echo signal in order; 3 the search range, interval and number of the speed fuzzy number, the linear frequency modulation slope and the secondary frequency modulation slope are initialized, and a fuzzy speed compensation function is built; 4 Keystone transformed data are multiplied by the fuzzy speed compensation function, and then fast inverse Fourier transform is carried out in the fast time domain; 5 improved discrete linear frequency modulation Fourier transform is carried out on the data processed in the step 4; and 6 the steps of 4 and 5 are repeated until the search of the speed fuzzy number is completed, and a detection unit diagram is constructed for constant false-alarm detection. The method provided by the invention has the advantages of better detection performance and smaller calculation amount, and can be used for remote early warning of a ground-based radar.

The invention discloses a bi-static radar eustatic movement target detection method based on a Beidou satellite radiation source. The method comprises the following steps: performing range migration correction on an echo signal under long observation time by adopting symmetric second-order Keystone transform, and performing unified de-sloping processing on the echo signal under the whole observation time, and then performing the framing processing, performing coherent accumulation on an intra-frame signal and performing incoherent accumulation on an inter-frame signal, thereby effectively solving a problem that a Beidou satellite is low in target echo signal-to-noise ratio when being served as an external radiation source. The range motion and the range bending can be simultaneously removed under the condition of unknowing a Doppler parameter by adopting the symmetric second-order Keystone transform, so that the range migration correction can be better realized; since the intra-frame signal only needs to perform the addition computation and the inter-frame signal does not to perform Doppler centroid compensation operation when being in the energy accumulation processing, and the computation burden is greatly reduced.

The invention discloses a moving-target instantaneous distance Doppler imaging method based on detuning and keystone processing; and problems that larger range migration exists in the traditional moving-target moving technology under a circumstance that moving-target motion parameters are unknown and complete azimuth spectra are not included in a baseband are mainly solved. The realizing process comprises the following steps of: (1) receiving an original synthetic aperture radar echo signal and carrying out Fourier transform on the echo signal at range; (2) constructing an azimuth detuning function so as to detune the echo signal; (3) removing linear walking momentum of the echo signal by using Keystone transform; (4) estimating an azimuth fuzzy number of the echo signal after the linear walking momentum is removed and filtering the echo signal at azimuth; and (5) carrying out inverse Fourier transform and Fourier transform on the echo signal, which is filtered at azimuth, at both the azimuth and the range, so as to obtain an imaging result of the echo signal; and according to the invention, an imaging effect of a moving target can be effectively improved; and the moving-target instantaneous distance Doppler imaging method based on detuning and keystone processing, disclosed by the invention, can be used for the field of moving target detection, identification and imaging.

The invention discloses a nonlevel flight double-station SAR frequency domain FENLCS imaging method based on a quadratic elliptic model. The method comprises the following steps: firstly, performing range direction pretreatment, namely applying linear range walk correction, KT (keystone transform), bulk range cell migration correction and second range compression in a range direction; secondly, executing residual high-order range cell migration correction treatment of azimuth space variation. According to a range direction pretreatment result, the quadratic elliptic model is put forward in theinvention, and the quadratic elliptic model is used for accurately describing azimuth space variation characteristics of an equidistant point receiver squint angle and beam center slope distance. Theimproved FENLCS imaging processing method based on the quadratic elliptic model, provided by the invention, realizes removal of characteristics of space variation with azimuth positions of a residualdoppler center, doppler modulation frequency and a high-order phase coefficient, and consequently completes azimuth unified focusing treatment. Additionally, a frequency domain high-order non-space variation prefiltering method is provided, a derivation procedure of a FENLCS algorithm is simplified, and focusing quality is improved.

The invention provides an ultra-wideband radar single-channel digital beam forming method based on a space-time coding array, and aims to reduce the sidelobe level of the distance dimension and the angle dimension of a DBF output signal and improve the precision and the angle resolution of a beam pointing angle. The method comprises the following implementation steps of constructing a space-time coding array; obtaining a digital baseband signal based on the space-time coding array; performing pulse compression on the digital baseband signal; performing Fourier transform on the signal obtainedby pulse compression; performing Keystone transform on the frequency domain signal; setting frequency domain equivalent DBF algorithm parameters; and obtaining an ultra-wideband radar digital beam forming result based on a frequency domain equivalent DBF algorithm. According to the ultra-wideband radar single-channel digital beam forming method provided by the invention, the space-time coding array is constructed, and spatial coding is carried out on the array spatial domain signal, so that the sidelobe level of the distance dimension and the angle dimension of the DBF output signal is effectively reduced, the ultra-wideband radar digital beam forming result is obtained based on frequency domain equivalence, and the precision and the angle resolution of the beam pointing angle are effectively improved.

The present invention relates to a Keystone transform airspace and time domain walking compensation method based on the PD radar system. Firstly, the distance-array element plane obtained by a single PRT sampling is subjected to distance-dimensional Fourier transform, and the distance-array element plane is transformed into fast Fourier. leaf-array element plane, and then perform interpolation between the array elements on each fast Fourier channel to realize the Keystone transformation of the space domain; secondly, perform DBF, that is, form the directional beam of the desired signal, and the weight is Ideal weight; finally, the fast Fourier-slow time plane in the dwell time of the beam is interpolated in the slow time dimension, and the frequency domain pulse is compressed to realize the distance walking compensation in the time domain.

The invention provides a moving target focusing method based on keystone transform and an integral quadratic function, which mainly solves the problem that conventional moving target focusing method cannot effectively compensate for the high order range and Doppler migration of a moving target. The method comprises the steps of emitting pulse linear frequency modulation signals and receiving radarecho; reading radar echo signals for range pulse compression and rapid Fourier transform; performing azimuth slow time reversal transform in a range frequency domain; performing second-order keystonetransform on the signals subjected to the azimuth slow time reversal transform; performing range frequency domain inverse fast Fourier transform on the signals subjected to the second-order keystonetransform; extracting the azimuth slow time signals of a single range unit for integral quadratic function processing, estimating a quadratic term, building a compensation function for focusing on a moving target and traversing all range units to focus on all targets. The method can effectively compensate for high order range and Doppler migration of a moving target and is used for synthetic aperture radar moving target focusing imaging.

The invention belongs to the technical field of radar target signal estimation, and particularly relates to a maneuvering target coherent detection method based on coordinate rotation and non-uniformFourier transform. The method comprises the following steps that: aiming at a radar signal to establish a maneuvering target signal model; carrying out range migration processing on the maneuvering target signal model; and through the coordinate rotation and the non-uniform Fourier transform, jointly estimating a target motion parameter. By use of the method, a contradiction between calculation complexity and detection performance can be alleviated, a second-order Keystone transform (SoKT) is used for eliminating QRM (Quadric Range Migration), a relationship between a rotation angle and Doppler frequency is combined to construct a phase compensation function, and a simulation experiment is used for verification. Compared with an existing representative algorithm, the method can obtain almost ideal detection performance by low operation complexity, and has a good application prospect.

The invention relates to a method for removing target detection Doppler dispersion of broadband signals based on sub-band processing, and belongs to the technical field of radar target acquisition. According to the method, a direct wave is decomposed into a plurality of sub-bands, phase-coherent accumulation is conducted on each sub-band, plural superposition is conducted on a phase-coherent accumulation result of each sub-band, and a final CAF output result is obtained. In order to make a target peak value accumulated by each sub-band be located on the same Doppler unit, different accumulation time needs to be selected according to a carrier frequency of each sub-band. Compared with a traditional Keystone transform method, a sub-band method is free of the hypothesis that the signal waveform is unchanged, and avoids the signal to noise ratio loss caused by the hypothesis that the signal waveform is unchanged. The method obviously removes the target Doppler dispersion through the sub-band method, effectively improves the phase-coherent accumulation grain, accordingly, improves detection performance of a system, and is especially suitable for being used on application occasions for detecting high-speed targets with long-time accumulation adopted.

The invention discloses a moving target tracking method based on video SAR cross-domain combination. The implementation scheme is as follows: 1) performing coarse detection on a moving target shadow by utilizing background difference in an image domain; 2) carrying out range walk correction in a range Doppler domain by utilizing Keystone transform, and carrying out coarse detection on echo energyof a moving target by utilizing improved OS-CFAR; 3) performing intra-frame data association on the rough detection results formed in the two domains; 4) performing inter-domain matching on the weak correlation track set formed in the two domains; and 5) performing frame-by-frame management on the output flight path. According to the method, confidence judgment is carried out on the tracks in theimage domain and the distance Doppler domain according to the closeness degree of inter-frame data association, inter-frame matching processing is carried out on the weakly combined tracks, high falsealarm and high missing alarm conditions in the image domain or the distance Doppler domain are effectively reduced, and real-time detection and tracking of the video SAR moving target are realized.

The invention provides a joint estimation method for multi-target motion parameters in a pulse Doppler radar system. The specific process comprises the steps of first, modeling radar echo data, carrying out pulse compression on the radar echo data, and transforming into a fast time-frequency domain to obtain a range frequency domain-azimuth time domain signal; second, performing range walk correction on the range frequency domain-azimuth time domain signal based on Keystone transform, and performing inverse Fourier transform on the corrected signal along the range direction; and third, performing Lv's transform on the processed signal in the second step to estimate motion parameters of targets. The joint estimation method provided by the invention for multi-target motion parameters in thepulse Doppler radar system can simultaneously perform Keystone transform and Lv's transform on multiple targets respectively, so that high-precision parameter estimation can be simultaneously carriedout on multiple targets in the same range unit of the same beam.

The invention discloses an NLCS imaging-based multi-channel two-pulse clutter cancellation method for double-base forward looking SAR. According to the method, the migration of a distance unit is firstly corrected by using keystone transform, and then the azimuth space change of an echo is removed through an NLCS algorithm, so that a clutter and a moving target are separated from each other in a two-dimensional space-time domain; and finally, a clutter canceler is designed to suppress the clutter according to clutter and echo characteristics, thereby improving the signal-to-noise ratio of theecho, and then laying a foundation for improving the subsequent moving target detection.

The invention discloses an estimation method for a motion parameter of a stepped frequency radar target, and belongs to the field of radar signal processing. The stepped frequency radar signal is verysensitive to the target motion, therefore the motion speed of the target needs to be accurately estimated before a high resolution range profile is synthesized. The method comprises the steps of firstly, analyzing radar echo signal characteristics of a uniform-speed motion target, and eliminating a secondary phase term of the echo through Keystone transform; and secondly, performing IFFT (InverseFast Fourier Transform) operation on a group of stepped frequency echo signals and then performing FFT (Fast Fourier Transform Algorithm) operation to obtain a two-dimensional distance-speed parameter spectrum, and obtaining accurate estimation values of the target speed and the initial distance according to the peak position. However, when noise interference exists, the target parameter estimation is not accurate, therefore, the distance dimension parameter spectrum is denoised by using a maximum likelihood estimation threshold-based Morlet wavelet denoising method so as to obtain the accurate parameter estimation of the target in low signal to noise ratio. The estimation method for the motion parameter of the stepped frequency radar target disclosed by the invention has popularization and application values in the field of stepped frequency radar signal processing.

The invention discloses a method for estimating micro-movement geometric parameters of broadband radar ballistic targets based on phase ranging, which belongs to the field of radar technology. Theoretical results of the macro-distance curve of the i-th scattering center: the range-time echo signal of the i-th scattering center is segmented and Keystone transformed using the segmented approximate macro-curve extraction method, and the rough estimated instant of the i-th scattering center is obtained The macro curve uses the phase ranging macro curve extraction method to obtain the high-precision macro curve of the i-th scattering center, and then obtains the estimated value of the precession frequency of the cone target and the estimated value of the target half-cone angle The estimated value of the busbar length of the cone target, the estimated value of the height of the cone target and the estimated value of the radius of the bottom surface of the cone target are used as the estimated results of the fretting geometric parameters of the broadband radar ballistic target based on phase ranging.