High-resolution squint SAR echo Doppler spectrum recovery method and system

Abstract

The invention discloses a high-resolution squint SAR echo Doppler spectrum recovery method and system. The method comprises the following steps: acquiring original echo data, and carrying out range-direction fast Fourier transform on the original echo data to obtain range-direction FFT data; performing range pulse compression on the range FFT data to obtain pulse compression data; performing Doppler frequency shift elimination on the pulse compression data to obtain Doppler frequency shift elimination data; carrying out azimuth deramp processing on the Doppler frequency shift elimination data to obtain deramp processing data; performing azimuth linear frequency modulation Z transformation on the deramp processing data to obtain CZT data; carrying out the Doppler modulation recovery on the CZT data to obtain an aliasing-free two-dimensional frequency spectrum, and then obtaining a high-resolution SAR image through a frequency domain imaging algorithm. According to the method, interpolation operation is avoided, the operation is simplified, the imaging quality is ensured, and the method is more universal.

Description

technical field [0001] The invention relates to the technical field of SAR imaging, in particular to a high-resolution squint SAR echo Doppler spectrum recovery method and system. Background technique [0002] Synthetic aperture radar (SAR) is a microwave remote sensing device with two-dimensional high resolution. By controlling the direction of the antenna beam, SAR can effectively break through the limitation of the radar antenna size on the azimuth resolution. However, in practical applications, the pulse repetition frequency (Pulse repetition frequency, PRF) of the system is usually limited. During the processing of full-aperture high-resolution SAR signals, the total Doppler bandwidth of the signal will be much larger than the PRF of the system. At the same time, the spaceborne SAR attitude control and beam pointing errors will introduce small oblique angles, and the existence of oblique angles will intensify the range and azimuth coupling of the signal, resulting in s...

AI Technical Summary

Problems solved by technology

The sub-aperture method divides the radar echo data into multiple sub-apertures in the azimuth direction, and then processes the sub-apertures separately to avoid spectrum aliasing, but the segmentation and reorganization of the data will increase the complexity of the algorithm and reduce the quality of the focused image

The two-step method is mainly aimed at full-aperture SAR data processing, through the azimuth deramp with a constant range and space, and oversampling the signal to increase the sampling interval in the Doppler domain, thereby restoring the spectrum without aliasing, but this method is not effective in processing high Doppler spectrum aliasing problem cannot be completely eliminated when using high-resolution spaceborne SAR data

An improved two-step method uses distance-space-variant azimuth deramp to make up for the shortcomings of the traditional two-step method, but does not consider the existence of oblique angles of view, and will cause uneven sampling in the Doppler domain, resulting in the inability to apply frequency domain algorithms in the future for high quality images

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