Large-scene imaging method of near-space slow-velocity platform synthetic aperture radar

Abstract

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.

Description

technical field [0001] The invention belongs to the technical field of synthetic aperture radar (Synthetic Aperture Radar, SAR) imaging, and in particular relates to a large-scene imaging method for an adjacent space slow platform SAR. Background technique [0002] Compared with optical sensors, Synthetic Aperture Radar (SAR) has the unique advantages of strong penetrability and ability to work around the clock. It has been widely used in the fields of earth remote sensing, resource exploration, reconnaissance, surveying and mapping, and disaster forecasting. [0003] Near space (Near space) is the space 20km to 100km away from the ground. As a SAR carrier platform, it has many unique advantages compared with other platforms. For example, compared with airborne SAR, near space SAR has long residence time, strong survivability, high efficiency Compared with spaceborne SAR, near-space SAR has the advantages of flexible maneuverability and short revisit cycle; it plays an impor...

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Problems solved by technology

However, this method involves sub-aperture division and sub-aperture image splicing, etc., and has the problems of complex algorithm and low efficiency; ):2352-2360) to remove Doppler aliasing by copying and expanding the echo Doppler spectrum, and after focusing, use the copying and expanding of the azimuth time domain data to remove the aliasing in the azimuth time domain, because data replication in the azimuth direction is required Stitching and down-sampling operations will not only increase the data storage and processing burden of the system, but also increase aliasing energy and noise, resulting in image quality degradation; the literature "Sliding Spotlight and TOPS SAR Data Processing Without Subaperture" (IEEE Geoscience and Remote Sensing Letters, 2011, 8(6):1036-1040) uses the preprocessing method of Doppler center de-slope and re-tilt for Doppler anti-aliasing, and then uses the linear Chirp Scaling algorithm for range cell migration correction (RCMC ), the problem with this method is that the RCMC error is large due to the neglect of the space-variation of the echo range modulation frequency, and there is aliasing in the time domain of the echo azimuth after preprocessing, and it is impossible to use a more accurate nonlinear frequency modulation scaling (Non-linear Chirp Scaling, NLCS) algorithm or Extended Chirp Scaling (ECS) algorithm for RCMC

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