40 results about "Chirp scaling" patented technology

The invention belongs to the field of radar signal processing, and discloses a missile-borne SAR sub-aperture forward squint high-order nonlinear chirp scaling imaging method. According to the method, missile-borne SAR forward squint high-order nonlinear chirp scaling imaging is achieved through sub-aperture data, and the method can be used for SAR imaging of airborne platforms or missile-borne platforms. The method mainly includes the steps of firstly, conducting distance pulse pressure and time domain walking correction on an echo signal; secondly, converting the signal into the two-dimensional frequency domain, conducting frequency domain migration correction and secondary compression, and compensating for the high order phase in the orientation direction; thirdly, leading high-order nonlinear chirp scaling disturbance factors into the orientation frequency domain, and correcting the space variability of the Doppler frequency modulation and the high-order terms in the orientation direction; fourthly, focusing an image on the orientation frequency domain through spectrum analysis. The method solves the problem of decoupling of distance orientation and the orientation focus depth problem caused by time domain walking correction, and the method can meet the requirements for different scenes and high resolution and can be used for the field of ground mapping and other fields.

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 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 discloses a two-dimensional multi-aperture scan synthetic aperture radar (SAR) imaging method. The method includes the following steps of S101, subjecting echo data received by sub-apertures to range direction pulse compression respectively by using a range direction matched filter; S102, uniting the echo data which are subjected to pulse compression in a range direction and an azimuth direction to form a matrix Z and subjecting rows of the matrix Z to weighting summation by using a two-dimensional weighting vector wk respectively; and S103, subjecting the echo data to focusing imaging by using an extended chirp scaling (ECS) algorithm. By means of range direction and azimuth direction united two-dimensional digital beam forming (DBF) processing, echo separation of various sub-swaths and frequency spectrum reconfiguration of azimuth periodicity non-uniform sampling signals are achieved, and problems of mutual interference and azimuth multi-channel non-uniform sampling of echo signals of various sub-swaths under a two-dimensional multi-aperture scan SAR mode are solved.

The invention relates to an improved NCS (Nonlinear Chirp Scaling) imaging algorithm suitable for a geosynchronous orbit (GEO) SAR (Synthetic Aperture Radar), belonging to the technical field of SAR imaging. The NCS imaging algorithm is improved by establishing a curved locus signal model for replacing an equivalent linear model in an original NCS imaging algorithm and evaluating a two-dimensional resolving spectrum expression suitable for the NCS imaging algorithm on the basis of the established curved locus signal model. Compared with the prior art, the improved NCS imaging algorithm has the advantages that: a novel curved locus model suitable for the GEO SAR is obtained with a high-order Taylor expansion method, and the defects of large error of a near equivalent linear model, completely unavailable application of a far equivalent linear model and the like of the GEO SAR can be overcome by adopting the locus model; and meanwhile, a two-dimensional resolving spectrum suitable for the NCS algorithm is obtained on the basis of the equivalent linear model, and various compensation functions of the NCS algorithm can be resolved by using the spectrum, so that the requirement on large-scene imaging of the GEO SAR is met.

The present invention discloses an FPGA (Field Programmable Gate Array) realization method of a SAR (Synthetic Aperture Radar) signal processing algorithm, belonging to the radar imaging and digital signal processing technology field. The method comprises: building hardware configuration of an upper computer, an Ethernet data communication module, an algorithm processing module, a DDR3 SDRAM and a control module thereof, a data selection module, a reset module, a clock management module, the algorithm processing module is provided with a polar coordinate format imaging algorithm of dechirp signals based on the Chirp Scaling principle and a two-dimensional self-focusing algorithm, and therefore the problem of high resolution ratio imaging of a mini-type SAR system and the ultrahigh resolution imaging processing of SAR etch signals are realized.

The invention belongs to the technical field of SAR imaging, and particularly relates to an improved sub-aperture SAR chirp scaling Omega-K imaging method. The method includes the specific steps of firstly, conducting range-direction Fourier transform on original echo data; secondly, conducting azimuth-direction matched filtering on a signal, multiplying the signal by a rotation correction function, and achieving the forward lateral processing for a wave number spectrum supporting area; thirdly, conducting azimuth-direction Fourier transform on the signal, and conducting azimuth resampling interpolation a two-dimensional wave number field; fourthly, multiplying the signal by a unified phase compensation function, conducting expansion Stolt interpolation, and achieving the range-direction spatial position field focusing through the range inverse Fourier transform; fifthly, multiplying the signal by a deramp correction function, conducting azimuth inverse Fourier transform, multiplying the azimuth spatial position by an azimuth position correction function in the azimuth spatial position field, and finally achieving the azimuth-direction wave number field focusing through the azimuth Fourier transform. The method is wide in application range, capable of achieving the high-resolution imaging, and can be used for the fields of ground mapping, target recognition and the like.

The invention discloses a single-pixel photon counting three-dimensional imaging system and method based on multi-resolution wavelet approximation. The imaging system comprises a structure light projection system, a photon receiving system and a synchronous control and signal processing system; a target scene is imaged through adopting a single-photon camera structure formed by combining a single-pixel photon detector and a digital micro-mirror device (DMD). According to a multi-resolution wavelet approximation principle, detail information from a low resolution to a high resolution ratio of the target scene is gradually obtained from an initial resolution ratio image, and is used for reconstructing a final resolution ratio three-dimensional image. According to the single-pixel photon counting three-dimensional imaging system and method, the number of times of sampling is effectively reduced and the imaging time is shortened; the single-pixel photon counting three-dimensional imaging system and method are applicable to high resolution ratio three-dimensional imaging application; meanwhile, the computation cost of a CS (Chirp Scaling) algorithm is avoided and the time needed by reconstruction is shortened; the single-photon camera structure formed by combining the single-pixel photon detector and the DMD is utilized so that the system size is reduced and the system structure is simplified; the single-pixel photon counting three-dimensional imaging system and method have the characteristics of simple structure, high reliability and low cost.

The invention relates to a compressive sensing imaging method for a synthetic aperture radar. The method includes: constructing a standard orthogonal basis for indicating radar echo signals by the aid of a Chirp Scaling operator, processing distance-vector and azimuth-vector two-dimensional data simultaneously by compressive sensing, and sparsely optimizing finally so as to obtain high-resolution radar images based on low data size. By the method, the data size is decreased in the distance vector and the azimuth vector firstly, then the standard orthogonal basis for indicating the radar echo signals is constructed by the aid of the Chirp Scaling operator, and two-dimensional sparse optimization is performed in the distance vector and the azimuth vector by means of compressive sensing so that the radar images are obtained. The data size can be decreased effectively under the circumstance of sparse observation scenes to lower requirements on data storage devices and transmission devices of the synthetic aperture radar, and the compressive sensing imaging method is of great practical significance to a practical system.

The invention provides an improved double-base synthetic aperture radar NLCS (Nonlinear Chirp Scaling) imaging algorithm. The improved double-base synthetic aperture radar NLCS imaging algorithm comprises the following specific steps: firstly, calculating a cubic phase phi 3 of range direction of a target echo, selecting a reference point, acquiring a cubic phase phi'3 at the reference point according to the phi 3 and then multiplying the target echo by the conjugation of phi'3 at the reference point in a two-dimensional frequency domain to obtain a signal for eliminating the influence of high-order phase; secondly, multiplying the processed signal in the first step by a disturbing function phi in a range Doppler domain and multiplying the multiplied result by a matched filter phi R in the two-dimensional frequency domain; thirdly, converting the processed signal in the second step to a two-dimensional time domain to be multiplied by a direction distribution function phi 4, then multiplying the multiplied result and a matched filter phi 5 in the range Doppler domain and finally multiplying the multiplied result and phi 6 in the two-dimensional time domain to obtain an SAR (Synthetic Aperture Radar) slope-distance image; and fourthly, carrying out geometric rectification on the SAR slope-distance image acquired in the third step to obtain an SAR ground range image. According to the improved double-base synthetic aperture radar NLCS imaging algorithm, the influence generated by the two-dimensional spatial variability of the range tuning frequency and high-order phase when a sender is seen obliquely is improved.

The invention provides a synthetic aperture radar (SAR) imaging method for azimuth-direction nonlinear chirp scaling of a diving model. The synthetic aperture radar imaging method includes carrying out range-direction fast Fourier transform (FFT) for raw echoed data of SAR and then carrying out range walk correction; carrying out range compensation after the azimuth-direction FFT; carrying out range-direction inverse fast Fourier transfer (IFFT) before three times of phase compensation; carrying out azimuth-direction nonlinear chirp scaling after the azimuth-direction IFFT; and finally carrying out azimuth-direction FFT again, carrying out azimuth compensation, and then carrying out azimuth-direction IFFT for data subjected to azimuth compensation to obtain a final SAR image. By the synthetic aperture data imaging method, SAR imaging at large squint angles can be realized, azimuth-direction focusing depth is increased, and high-precision SAR imaging under high-azimuth focusing depth can be realized in the diving model.

The invention relates to a radar interference confrontation technology, and especially relates to a synthetic aperture radar interference technology. The invention discloses a synthetic aperture radarinterference method based on frequency-controlled array antenna. The method includes the following main steps: a. a frequency-controlled array antenna model and a synthetic aperture radar interference model are established; an antenna model of a frequency-controlled array is a linear array; b. intermediate frequency sampling and storage are performed on a frequency-controlled array signal received by a synthetic aperture radar; and c. distance Doppler processing is performed on a received frequency-controlled interference signal to obtain a position of the frequency-controlled array antenna.Beneficial effects of the method are that: interference can be generated to a synthetic aperture radar imaging system using a distance Doppler (RD) imaging algorithm and a chirp scaling (CS) imaging algorithm, and multiple false targets are generated; and the distance between the false targets and the number of the false targets are related to frequency offset and the number of array elements between frequency-controlled array antenna elements. The method is very suitable for interference in an airborne synthetic aperture radar imaging system.

The invention is applicable to the field of deep space communication, and provides a deep-space-communication-oriented cross-layer joint file transmission method. An image is compressed by adopting a CS (chirp scaling) algorithm in the transmission process of the image, so that the image can be jointly optimized with the Spinal code of a bottom layer and then is transmitted; a cross-layer joint transmission mechanism refers to that the CS image compression of an application layer, the CS erasure correction of a transmission layer and the Spinal code of a data link layer/physical layer are jointly optimized and a transmission mechanism is designed in combination with an LTP (Licklider transmission protocol), and after finishing sending certain data, a sending end determines a symbolic number to be sent at a next moment through Markov prediction and feedback information without waiting for feedback. After receiving the feedback, the sending end pauses sending the data, processes the feedback, and additionally sends the symbolic number aiming at a coding block with an error, and the additionally sent symbolic number is decoded together with the symbolic number sent before. On the premise that certain reliability is guaranteed, the effectiveness of a system is improved.

The invention discloses an FPGA parallel implementation method applied to a polar coordinate format algorithm in an airborne SAR real-time processing system and solves defects that an existing signalprocessing platform is insufficient in processing capacity and low in imaging precision under the requirements of extremely low power consumption, light weight limitation and miniaturization. A PFA high-precision imaging algorithm is adopted, engineering improvement of the algorithm is carried out on the basis of the Chirp Scaling principle (PCS), distance direction interpolation can be equivalently realized through two FFT operations, calculation is greatly reduced, acceleration processing of a polar coordinate format algorithm is achieved efficiently in parallel in an FPGA chip, and algorithm execution efficiency and the processing speed of a real-time imaging system are improved. The method is applied to an airborne SAR real-time processing system, has the capacity of conducting continuous and stable high-resolution imaging on the ground, has high application value and is worthy of popularization.

The invention provides a monolithic FPGA (field programmable gate array) based Chirp Scaling imaging method. The method specifically includes creating an FFT (fast Fourier transform) operation module, a Doppler center frequency estimating and fitting module, a Doppler frequency modulation slope estimating and fitting module, a parameter calculating module, a Chirp Scaling factor generating module, a range direction compensation factor generating module, an azimuth direction compensation factor generating module, a complex multiplication module, a data transposition module, a core calculation module and an image quantization module on an FPGA, and performing Chirp Scaling imaging according to the created modules. According to the method, the framework for realizing the Chirp Scaling imaging is analyzed, the degree of parallelism of imaging calculation is increased to the uttermost, the advantages of the FPGA can be given full play, and real-time performance of imaging is further improved.

The invention discloses a color image acquisition method. The method comprises the following steps: firstly, reconstructing a brightness image Y which has a relatively high resolution and can reflect more details under white light; reconstructing a red monochrome image R and a blue monochrome image B which have relatively low resolutions under red light and blue light respectively; calculating a green monochrome image G by using a linear relation according to the acquired brightness image Y, the red monochrome image R and the blue monochrome image B; performing linear conversion according to the obtained red monochrome image, green monochrome image and blue monochrome image to obtain a monochrome image U and a monochrome image V presenting chrominance information; extending the resolutions of the monochrome image U and the monochrome image V to a solution being the same as that of the brightness image Y through up-sampling; and lastly, fusing a component Y, a component U and a component V to reconstruct a color image. Through adoption of the color image acquisition method, the sampling times are reduced effectively; important information is not lost; calculation overhead needed by a CS (Chirp Scaling) algorithm is avoided; and time needed by reconstruction is shortened.

The present invention relates to a non-uniform velocity CS imaging method which eliminates the influence of the platform non-uniform velocity motion on an imaging result on the basis of a conventional time domain walk correction CS imaging method, and by analyzing a non-uniform velocity signal model and introducing a velocity sequence and a tertiary correction function. The non-uniform velocity CS imaging method of the present invention not only can obtain the higher imaging resolution, but also is lower in processing complexity by not having the interpolation operation, and is suitable for the synthetic aperture radar (SAR) imaging of various miniature platforms.