Imaging method for high-squint synthetic aperture radar
A technology of synthetic aperture and imaging processing, applied in the field of signal processing, which can solve the problems of not considering the Doppler center and the degradation of imaging performance
Inactive Publication Date: 2018-01-26
HANGZHOU DIANZI UNIV
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Problems solved by technology
Aiming at this problem, some relevant literatures proposed a nonlinear chirp scaling (NLCS) algorithm based on Keystone transform (KT), but it did not consider the influence of Doppler center and residual range migration, resulting in the algorithm dealing with high squint, high Imaging performance degrades when using high resolution echo data
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[0079] Below in conjunction with accompanying drawing and attached table, the present invention is described by example.
[0080] figure 1 is the geometric model of SAS, point P is any point in the imaging area, the transmitter moves with speed v along the direction parallel to the y-axis in the yoz plane, θ is the oblique angle of view, R(η) is the instantaneous slant distance of P, R Rc for η c time slant distance.
[0081] figure 2 and image 3 They are the traditional method and the improved distance processing results respectively, where P0 is the center point, and P2 and P4 are the azimuth edge points. figure 2 Not only there is a more obvious distance migration residue, but also the edge points P2 and P4 have a more obvious defocus phenomenon. image 3 As a result of the processing of the method of the present invention, since the Doppler center frequency is removed and the residual term of the distance migration is corrected, a relatively good correction effect ...
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The invention discloses an imaging method for a high-squint synthetic aperture radar. The method includes the following steps: obtaining a received echo signal, performing Fourier transform on the received echo signal in the range direction; performing linear range migration correction on the signal in a range frequency, also removing the Doppler centroid frequency from the signal; reconstructingtime in the azimuth direction by performing Keystone transform, a design filter performing range compression; transforming the signal to an azimuth frequency, analyzing the relation between the azimuth chirp rate and a squint range, then transforming the azimuth frequency to an azimuth time frequency, and multiplying the azimuth time frequency and a scaling function; transforming the signal to theazimuth frequency, the design filter performing azimuth compression, transforming the signal that undergoes the azimuth compression to azimuth time frequency, and obtaining a focused image. Accordingto the invention, the imaging method herein can achieve excellent focusing effects in handling the high-squint and high-resolution echo data.
Description
technical field [0001] The invention belongs to the field of signal processing and relates to a synthetic aperture sonar imaging algorithm, in particular to a method for obtaining high-resolution imaging under high squint conditions. Background technique [0002] Synthetic Aperture Sonar (SAS, Synthetic Aperture Sonar) transmits broadband sonar signals underwater and receives reflected echoes for coherent processing to obtain images of the seabed. The traditional SAS imaging algorithm is mainly used in scenes with a small side view or oblique angle of view. This mode has a narrow range of applications and is not very flexible. The SAS in the scene of high squint has strong practicability, and its biggest advantage is that it has the ability to image outside the area, that is, the support body can directly image the seabed target in the area without directly passing through the area. [0003] Under the condition of high squint, the SAS echo signal has a large range migration...
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Inventor 章坚武杨樊张松钟华张艳军严爱博
Owner HANGZHOU DIANZI UNIV