Abstract
The image of ground maneuvering targets may be defocused due to the Doppler ambiguity, high-order range migration (RM), and Doppler frequency migration (DFM) caused by the target’s complex motions in a synthetic aperture radar (SAR) system. To settle these problems, an efficient algorithm based on discrete polynomial-phase transform (DPT), keystone transform (KT), and matched filtering processing (MFP) is presented for ground maneuvering target refocusing and motion parameter estimation in this paper. Firstly, the DPT is applied to transform the cubic phase into the quadratic phase and simultaneously eliminate the quadratic RM, cubic RM, and quadratic DFM. Furthermore, the Doppler ambiguity containing Doppler center blur and Doppler spectrum ambiguity is also dealt with effectively by introducing a very small fixed lay time after DPT operation. Then, the KT is performed to correct the linear RM. After that, the matched filtering function related to the target’s equivalent third-order coefficient is constructed to compensate for the residual linear DFM in the range-time and slow-time domain. Lastly, a well-refocused image of the maneuvering target can be acquired, and the target’s motion parameters can be estimated effectively. The proposed algorithm has high computational efficiency and possesses favorable refocusing performance and motion parameter estimation precision. Simulation and real data processing results prove the effectiveness of the presented algorithm.
Highlights
Synthetic aperture radar (SAR), which can work on all time scales and in all weather conditions, is widely applied in the civil and military fields [1,2,3,4,5,6,7,8,9]
We propose an efficient method for ground maneuvering target refocusing based on discrete polynomial-phase transform (DPT), keystone transform (KT), and matched filtering processing (MFP), i.e., DPT–KT–MFP
We develop an efficient method for ground maneuvering target refocusing based on DPT–KT–MFP in this paper
Summary
Synthetic aperture radar (SAR), which can work on all time scales and in all weather conditions, is widely applied in the civil and military fields [1,2,3,4,5,6,7,8,9]. To address the abovementioned problems, the generalized radon Fourier transform (GRFT) [28] was proposed to eliminate the high-order RM and DFM, as well as deal with the Doppler ambiguity This method has optimal coherent accumulation performance and parameter estimation precision, the computational complexity of GRFT on the basis of four-dimensional (4D) parameter search is so huge that it is difficult to implement in practice. The KT-based method was proposed in [29], which first employs the KT to eliminate the linear RM, and eliminates the residual RM and DFM by jointly searching the acceleration, jerk, and Doppler ambiguity number This method can acquire similar target detection capability and parameter estimation precision to the GRFT method, but the focusing performance of the proposed method may deteriorate severely when the Doppler spectrum of a maneuvering target, whose bandwidth is greater than half of the pulse repetition frequency (PRF), is not entirely in one PRF band.
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