Adjacent space slow platform synthetic aperture radar big scene imaging method

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 field of synthetic aperture radar (Synthetic Aperture Radar, SAR) imaging technology, and specifically relates to a large-scene imaging method for a near-space slow platform SAR. Background technique [0002] Compared with optical sensors, Synthetic Aperture Radar (SAR) has the unique advantages of strong penetrability and can work all-weather and all-weather. It has been widely used in the fields of earth remote sensing, resource exploration, reconnaissance, surveying and mapping, and disaster forecasting. [0003] Near space is the space 20km to 100km from the ground. As a SAR carrier platform, it has many unique advantages compared to other platforms. For example, compared with airborne SAR, near space SAR has long residence time, strong survivability, and high efficiency. Compared with spaceborne SAR, near-space SAR has the advantages of flexibility and short revisit period; it plays an important role in application fields suc...

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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 extending the echo Doppler spectrum, and after focusing, remove the aliasing in the azimuth and time domain by copying and expanding the azimuth time domain data, because data replication in the azimuth direction is required Stitching and downsampling operations will not only increase the data storage and processing burden of the system, but also increase aliasing energy and noise, resulting in a decrease in image quality; 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-tilt 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 ignoring the space variation of the echo range modulation frequency, and the azimuth time domain of the preprocessed echo has aliasing, so 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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