Improved frequency stepping synthetic aperture radar (SAR) imaging method based on frequency domain frequency spectrum reconstruction

Abstract

An improved frequency stepping synthetic aperture radar (SAR) imaging method based on frequency domain frequency spectrum reconstruction specifically includes: 1 grouping frequency stepping SAR echo data stepping at carrier frequency n points to obtain n groups of sub-band echo data (including data of m distance lines) with different carrier frequencies; 2 judging whether aliasing can happen on distance frequency of the sub-band echo data performed with two-dimensional focus processing, and performing expanding operation on distance frequency spectrum of the sub-band echo data on yes judgment; 3 performing SAR imaging operation on the sub-band echo data, and removing an overlapped part of the frequency spectrum by windowing the distance frequency spectrum in the distance compression process when sub-band echo band width is larger than stepping frequency interval; 4 performing direction registering on n sub-images; and 5 performing distance frequency spectrum reconstruction on data of a kth distance line taken from each sub-image, repeating for m times and obtaining two-dimensional images with high range resolution. The method removes influence of sub-band data distance frequency spectrum aliasing and ensures distance frequency spectrum reconstruction to be performed smoothly.

Description

Technical field [0001] The invention relates to an improved frequency stepped SAR imaging method based on frequency domain spectrum reconstruction, belonging to the technical field of SAR imaging. Background technique [0002] Stepped frequency SAR imaging methods based on frequency domain spectrum reconstruction are mainly divided into two categories: ① first perform range compression and frequency domain spectrum reconstruction, and then perform range migration correction and azimuth focusing processing; ② perform two-dimensional focusing processing first, then do Range frequency spectrum reconstruction. For the first method, the distance compression operation needs to be performed before the distance spectrum reconstruction, but this structure cannot be used in combination with an efficient imaging algorithm—CS algorithm, so its adaptability is worse than the second method. However, the second method has a problem: after the two-dimensional focus processing, the range spectru...

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Problems solved by technology

[0003] The purpose of the present invention is to address the problem of range spectrum aliasing that may exist in the frequency-stepping SAR imaging method (the second method mentioned in the background technology) that performs two-dimensional focusing processing and then reconstructs the range-frequency domain spectrum. An improved frequency-stepped SAR imaging method based on frequency-domain spectral reconstruction is proposed

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