A refocusing iterative optimization method based on the quad-beam mode for accurate estimation of the azimuth velocity of slow-moving targets using SAR

ABSTRACT

SAR slow-moving target detection and velocity estimation in ultra-high speed platform and strong clutter are a serious problem. The existing slow-moving target velocity estimation methods including fractional Fourier transform (FrFT), bidirectional imaging mode (DiBi) and the dual-beam interferometry mode (DBI) cannot suppress the clutter, which reduces the accuracy of velocity estimation. To solve the problem, we propose an accurate azimuth velocity estimating method refocusing iterative optimization (RIO) based on the quad-beam mode. Firstly, we use the back projection (BP) algorithm for the quad-beam imaging, and perform accurate registration and clutter suppression for the two forward (fore-) and two afterward (aft-) beams respectively. After that, the azimuth offset in fore- and aft-beam images is utilized to achieve the coarse azimuth velocity estimation. Then we put forward the RIO algorithm to compensate the error in velocity estimation. Through iterative search and compensation the azimuth velocity, the azimuth offset is gradually reduced to disappear, thus a more accurate estimation of azimuth velocity is realized. The experiments validate the accuracy of azimuth velocity estimation of the proposed method and the error is less than 0.01 m ${\mathrm{s}}^{-1}$, which is much better than the other three typical methods (FrFT, DiBi, DBI).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This paper was supported by the National Key R&D Program of China(No.2017YFB0502702) and the National Natural Science Foundation of China under Grant 61671113, 61501098, and 61571099.