40 results about "Chirp scaling" patented technology

The invention relates to a construction method for an ionospheric three-dimensional probe satellite-bone SAR imaging processing platform, comprising the twelve steps of: step 1: initiating parameters and reading echo signal; step 2: carrying out orientation transformation toward Fourier; step 3: multiplying by Chirp Scaling (CS) factors; step 4: carrying out distance transformation toward Fourier; step 5: multiplying by distance compensation factors; step 6: carrying out distance inverse transformation toward Fourier; step 7: multiplying by orientation compensating factors; step 8: carrying orientation inverse transformation toward Fourier; step 9: multiplying by orientation Deramp factors; step 10: carrying out orientation transformation toward Fourier; step 11: carrying transverse toward Fourier; and step 12, outputting three-dimensional compression signals. The invention has the advantages of compact structure and fast processing speed, can generate three-dimensional distribution images with high resolution, realizes three-dimensional fine observation of an ionospheric irregular body on a top layer, lays solid technical foundation for developing new-generation ionospheric spaceenvironment detection load systems, and has wide practical value and application prospect.

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 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 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 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 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.