Yong-Liang Wang

Ground Moving Target Signal Analysis in Complex Image Domain for Multichannel SAR

For along-track multichannel synthetic aperture radar, this paper proposes a novel ground moving target signal model in the high-resolution complex image domain. Based on the range-Doppler imaging of static scene, the 2-D complex response of an isolated rectilinearly moving target is derived via the stationary phase principle (SPP) approximations. It is shown that moving targets in complex domain can be divided into three types according to the 2-D motion distribution and the SPP approximation conditions. Different from the known peaklike response of a static target, different amplitude and phase modulations will appear for different types of moving targets. Moreover, a single target can be split into two targets in the image when its Doppler spectrum spreads over two ambiguous Doppler zones. All types of targets will have the same Doppler interferometric effect along multichannel images, which is decided by the targets ambiguous Doppler frequency. Furthermore, with the proposed signal model, the complex image properties can be completely described and analyzed. Finally, some numerical experiments are also provided to demonstrate the effectiveness of the proposed signal model and analysis.

Parametric Velocity Synthetic Aperture Radar:Signal Modeling and Optimal Methods

Velocity synthetic aperture radar (VSAR) is equipped with a linear array to receive the echoes from a radar illuminating area via multiple channels, each of which can reconstruct a reflectivity image for the same stationary scene. Based on analysis of pixel vector sampled among multi-images, VSAR may effectively suppress the strong ground clutter and improve moving target detection and location. In this paper, different Doppler-distributed properties are derived for the moving target and clutter, respectively. Then, we propose a novel parametric statistical model for VSAR by dividing the pixel vector into three components, namely, target, clutter, and noise. Furthermore, a method of adaptive implementation of optimal processing (AIOP-VSAR) is presented for moving target detection. It is shown that the optimum detection performance may be obtained via AIOP-VSAR, particularly for the slowly moving target in an inhomogeneous clutter environment. Also, the Cramer-Rao bounds (CRBs) are derived for the estimation of unknown model parameters, as well as the azimuth locations of moving targets, and the maximum-likelihood methods are proposed to reach these CRBs. Based on the proposed target detection and parameter estimation methods, we present a complete parametric flowchart for VSAR. It is demonstrated that the proposed flowchart may effectively mitigate the azimuth location ambiguity of VSAR and has the super-resolution ability to resolve velocity layover for multiple targets. Finally, some detailed numerical experiments and scene simulations are provided to show the effectiveness of the proposed methods.

Parametric Velocity Synthetic Aperture Radar: Multilook Processing and Its Applications

Based on a parametric model and some optimum methods, it has been previously proved that parametric velocity synthetic aperture radar (VSAR) may improve the performances of moving target detection and parameter estimation simultaneously. In this paper, multilook processing is studied for parametric VSAR. At first, statistical signal models are established for azimuth multilook processing (AMLP) and range multilook processing (RMLP), respectively. By combining the multiple AMLP sublook pixel vectors, it is shown that the clutter parameter estimation accuracy can be further improved via the maximum-likelihood estimation methods. Meanwhile, based on the adaptive implementation for the optimum processing of VSAR, RMLP can be used to improve slowly moving target detection performance via the noncoherent integration of multiple range sublooks. Furthermore, it is shown that the Doppler frequencies of moving targets vary linearly with different range sublooks due to the different carrier frequencies of sublooks. Therefore, based on a proposed novel two-step multilook diversity (TS-MLD) estimator for RMLP, the azimuth location ambiguity of VSAR can be well resolved via least squares linear regression, without configuration change of the conventional VSAR. Also, the estimation accuracy of targets unambiguous Doppler frequency, as well as targets azimuth location, is derived for the proposed TS-MLD method. Finally, numerical experiments and scene simulations are provided to demonstrate the effectiveness of the proposed multilook-based methods.

Adaptive detection of moving target based on velocity synthetic aperture radar

By dividing a vector sampling at a specified pixel into three components, namely target, clutter, and noise, a novel parametric statistical model is proposed in the multi-channel and multi-look image domain of velocity synthetic aperture radar (VSAR). With the proposed parametric model, an adaptive moving target detection method is also obtained for VSAR, based on which the optimum improvement factors may be achieved. Furthermore, discussions are given for some VSAR systemic parameters. Some detailed numerical experiments are provided to demonstrate the effectiveness of the proposed model and the parametric methods of target detection.

Clutter modeling for bistatic SAR with phased array antenna and arbitrary geometry configuration

For bi-static synthetic aperture radar (Bi-SAR) with phased array antenna and arbitrary bi-static geometry configuration, this paper proposes a clutter modeling method for clutter suppressing and ground moving target detection. Furthermore, based on the simulated space-time clutter spectrum of four typical specific geometry configurations, the detailed analysis is also given for the clutter suppressing performance with space-time adaptive processing (STAP), Finally, some important conclusions are given for Bi-SAR with different geometry configuration.

VSAR parameter estimation based on azimuth multi-look processing

Based on the parametric velocity synthetic aperture radar (VSAR), the novel model of VSAR with azimuth multi-look processing is first established in this paper. Furthermore, Cramer-Rao bounds (CRBs) are derived for the VSAR model parameters estimation based on the maximum likelihood (ML) methods. It is shown that the clutter parameter estimation accuracy may be improved via azimuth multi-look processing as long as clutter-to-noise ratio is not too low. Finally, some numerical experiments are also provided to validate the proposed model and methods.

Signal modelling for ground moving target in complex image domain of multi-channel SAR

For along-track multi-channel synthetic aperture radar (SAR), this paper proposes a novel ground moving target signal model in the high-resolution complex image domain. It is shown that moving targets can be divided into three types according to the 2D motion distribution and the SPP approximation conditions. Moreover, a single target can be split into two targets in the image. All types of targets will have the same Doppler interferometric effect along multichannel images, which is decided by the targets ambiguous Doppler frequency. Furthermore, with our derived signal model, the complex image properties, i.e., amplitude reduction, azimuth shift, azimuth defocus, range blur, 2D slant, second-order phase modulation, split, interferometry and the effects of 2D accelerations are analyzed for airborne and spaceborne SAR, respectively. Finally, some experimental results are also provided to demonstrate the effectiveness of the proposed signal model and analysis.

Moving target location of VSAR based on maximum likelihood method

Based on the pixel vector sampled among multi-images, VSAR may effectively suppress the strong ground clutter and realize the moving target detection and locating. In this paper, the Cramer-Rao bounds (CRBs) are derived for the estimation of a proposed VSAR model parameters, as well as the azimuth locations of moving targets, and the maximum likelihood (ML) methods are further proposed to reach these CRBs. Finally, some detailed numerical experiments are also provided to show the effectiveness of the proposed methods.