Abstract-The imaging problem of spotlight synthetic aperture radar (SAR) in the presence of azimuth spectrum folding phenomenon can be resolved by adopting the azimuth deramping-based technique and traditional stripmap SAR imaging algorithm, and this method is the so-called two-step processing approach. However, when the spotlight SAR operates on squinted mode, the echo two-dimensional (2D) spectrum is shifted and skewed due to the squint angle. In such case, the original two-step processing approach is not suitable anymore. This paper presents a novel imaging algorithm using the deramping-based technique and azimuth nonlinear chirp scaling (ANLCS) technique. First, the problem of azimuth spectrum folding phenomenon in squinted spotlight SAR is analyzed. Subsequently, based on the analysis results, the linear range walk correction (LRWC) is applied for removing the squint angle impacts on signal azimuth coarse focusing. At last, a modified azimuth NLCS algorithm is proposed for overcoming the depth of focus (DOF) limitation problem that induced by the LRWC preprocessing. Point targets simulation results are presented to validate the effectiveness of the proposed algorithm to process squinted spotlight SAR data with azimuth spectrum folding phenomenon.
Abstract-In order to gain consistent focusing quality all over the imaging region for wide-beam wide-swath airborne synthetic aperture radar (SAR), higher motion compensation (MoCo) accuracy at the edge of the swath is needed. In this letter, an improved MoCo approach is proposed, and its performance is validated by using simulated data, as well as real data collected by a P-band SAR system.
Abstract-In this paper, a fast time domain imaging algorithm called bistatic forward-looking fast factorized backprojection algorithm (BF-FFBPA) based on sub-aperture and sub-image is proposed for general bistatic forward-looking synthetic aperture radar (BFSAR) with arbitrary motion. It can not only accurately dispose the large spatial variant range cell migrations and complicated motion errors, but also achieve high imaging efficiency. First, the imaging geometry and signal model are established, and the implementation of back projection algorithm (BPA) in the BFSAR imaging is given to provide a basis for the proposed BF-FFBPA. Then, considering motion errors, the more accurate requirements of splitting sub-aperture and sub-image in the BF-FFBPA is introduced based on the range error analysis to offer the tradeoff between the imaging quality and efficiency. Finally, the implementation and computational burden of the BF-FFBPA is provided and analyzed. Simulated results and evaluations are given to prove the correctness of the theory analysis and the validity of the proposed approach.
Wall parameters are essential for compensation of wall effects in the through-the-wall synthetic aperture radar imaging. In this paper, a new procedure is proposed to estimate wall parameters based on the idea of equation solving. By transmitting dual-frequency signals and extracting the time delay and magnitude information from the returns of outer and inner surfaces of a wall, we derive the analytical forms about the permittivity, the conductivity, and the thickness of a wall. Our new approach is simple and fast in the wall parameter estimation from range profiles.
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