Abstract
Due to the independence of azimuth invariance and high implementing efficiency, a fast time-domain algorithm has significant advantages for airborne bistatic synthetic aperture radar (BiSAR) data process with general geometric configuration. In this article, the practical problem of unexpected motion errors of the airborne platform is carefully analyzed under a fast factorized back-projection (FFBP) framework for a general BiSAR process and a coherent data-driven motion compensation (MOCO) algorithm integrated with FFBP is proposed. By utilizing wavenumber decomposition, the analytical spectrum of a polar grid image is obtained where the motion error can be conveniently investigated in image spectrum domain and the coherence between azimuthal phase error (APE) and motion-induced nonsystematic range cell migration (NsRCM) can be perfectly revealed. Then, a new data-driven MOCO method for both APE and NsRCM correction is developed with the FFBP process. Different from the data-driven MOCO in most frequency-domain algorithms, the residual NsRCM introduced by the FFBP process is particularly analyzed and addressed in the MOCO, which significantly improves the image quality in focusing. Promising results from both simulation and raw data experiments are presented and analyzed to validate the advantages of the proposed algorithm for the airborne BiSAR process.
Highlights
D UE to the observing ability in all weather and all dayand-night, synthetic aperture radar (SAR) has become a significant tool for microwave remote sensing [1]
frequency-domain algorithm (FDA) includes range-Doppler algorithm, chirp-scaling algorithm, Omega-K algorithm, etc., which originates from monostatic SAR processing, and these algorithms have been extended to many Bistatic SAR (BiSAR) applications with high computational efficiency
Most FDAs are based on the classic azimuth-invariant assumptions that may not valid in BiSAR applications, such as the cases of an SAR system operating in a nonlinear trajectory with varying platform velocities [8], general geometric configurations, etc., which introduces difficulties to the FDA process
Summary
D UE to the observing ability in all weather and all dayand-night, synthetic aperture radar (SAR) has become a significant tool for microwave remote sensing [1]. In [21], an autofocusing method based coordinate descent and secant processing was proposed and integrated with FFBP, which can effectively improve the focusing performance for monostatic SAR application It cannot be directly utilized in BiSAR with general configuration. Different from the data-driven MOCO in most FDAs, the residual NsRCM introduced in the FFBP process is analyzed and addressed, which significantly improves the image quality in focusing for high-resolution BiSAR application. Both simulation data and raw data set acquired from a BiSAR test bed are utilized to evaluate the proposed algorithm, and the experimental results show its performance superiority in practical applications.
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