Mingwei Shen

An ultra-low sidelobe ADBF algorithm for digital array

To obtain an ultra-low sidelobe level of adaptive digital beamforming, a process of designing auxiliary beams is introduced into the conventional adaptive sidelobe canceller (ASLC). In contrast to auxiliary elements utilized in ASLC, the steering directions of auxiliary beams are in accordance with jamming locations, and approximately orthogonal to the quiescent sum beam. Thus, the proposed beamformer can not only suppress the sidelobe level, but also reduce the processor’s degrees of freedom, which consequently results in a fast convergence rate and a much lower computational load.

Multichannel SAR wide-swath imaging based on adaptive removal of azimuth ambiguities

By exploiting the direction of arrival (DoA) information of azimuth ambiguity, an innovative algorithm for the adaptive suppression of azimuth ambiguity for multichannel synthetic aperture radar (SAR) wide-swath imaging is presented. It firstly estimates the DoA value of each azimuth component within a Doppler cell using the efficient noise subspace-based iterative estimation technique. Then the spatial filter for sequentially extracting the desired azimuth component is derived, which is designed to be used with the newly estimated DoA information within each Doppler bin. Finally, the azimuth ambiguities can be suppressed via the implementation of spatial filtering. The proposed approach is robust to aircraft velocity errors, and its effectiveness is validated via simulation results.

An Efficient Broadband Adaptive Beamforming Algorithm Based on Frequency–Space Cascade Processing

In this paper, the performance loss caused by the aperture fill phenomena and heavy computational burden in broadband adaptive beamforming (ADBF) is analyzed, and an efficient approach based on frequency–space cascade processing is presented. First, a digital compensation method is applied to compensate for the aperture fill time of the broadband phased array in the range-frequency domain, removing the dependence of the wideband array steering vector on the instantaneous frequency. Second, a subband adaptive beamforming scheme using range-compressed data is implemented, reducing the degrees of freedom of wideband jamming and avoiding signal cancelation in the ADBF covariance matrix estimation. Moreover, the conjugate gradient algorithm is used to iteratively calculate the ADBF weight vector to reduce the computational complexity. Finally, wideband ADBF can be achieved by subband synthesis. Theoretical analysis and simulation results are provided to demonstrate that the proposed approach can suppress jamming sufficiently with a rapid convergence rate, making this approach feasible for engineering implementation.

AN EFFICIENT ADAPTIVE CLUTTER COMPENSATION ALGORITHM FOR BISTATIC AIRBORNE RADAR BASED ON IMPROVED OMP APPLICATION

In this study, the misalignment of bistatic clutter spectral centers is considered, and an efficient adaptive main-lobe clutter compensation approach is presented for mitigating the bistatic geometry-induced clutter dispersion. In order to reduce computational load, an improved orthogonal matching pursuit (OMP) is introduced into the space-time clutter spectrum estimation. This method can accurately extract the required parameters for compensating the clutter spectral centers misalignment via sparse reconstruction with the desired Doppler cells. Simulation results are presented to demonstrate the effectiveness and efficiency of the proposed method.

An auto-focusing algorithm for monopulse imaging technique

To overcome the deterioration of azimuth resolution caused by errors of monopulse response curve (MRC) in practical processing, this paper proposes an auto-focusing algorithm for monopulse imaging technique. By applying iterative steps, this algorithm automatically extracts the echo signals of isolated strong scatterers from the received data, and employs them to accurately estimate the actual MRC. The estimated curve is then used in the procedure of monopulse imaging to autofocus the image in azimuth. As is verified by simulation and experimental results, this algorithm can effectively reduce the impact of MRC errors on monopulse imaging and is robust to most of the ground scenes, making it feasible in practical processing.

Fast implementation of spectral slope-based compensation for non-sidelooking airborne radar STAP

ABSTRACT This letter proposed a spectral slope-based compensation approach for space–time adaptive processing to mitigate the non-sidelooking geometry-induced clutter dispersion. In this approach, a cascade clutter spectrum estimation method is applied to reduce the computational complexity. This method can accurately extract the required compensation parameters via sparse reconstruction within the desired Doppler cells. Theoretical analysis and simulation results are presented to demonstrate the effectiveness and efficiency of the proposed method.

Space-time adaptive monopulse for RD-STAP parameters estimation

Space-time adaptive processing (STAP) is the key technology of airborne early-warning radar to suppress both clutter and interference, and the extended factored approach (EFA) is the well-established reduced-dimension (RD) STAP approach for engineering implementation. In this paper, the adaptive monopulse technique is introduced into EFA, and an efficient space-time adaptive monopulse to jointly estimate the target velocity and location is presented. Theoretical analysis and simulation results demonstrate that, when the real target Doppler frequency deviates from the central frequency of the Doppler bin, the proposed approach can estimate the velocity and angle parameters more precisely than the conventional adaptive monopulse.

CFAR detection of moving target for Monopulse-SAR based on statistical analysis of complex monopulse ratio

An efficient approach to achieve ground moving target indication (GMTI) for synthetic aperture radar (SAR) is to use the Monopulse-SAR system. This paper examines the statistics of complex monopulse ratio (CMR) for SAR/GMTI model when complex Gaussian clutter-plus-noise is considered. The two dimensional probability density function (pdf) of CMR is analyzed in detail. An automatic constant false-alarm rate (CFAR) detector with the probability of false alarm given in a closed-form for moving targets is provided and extended to a multi-CMRD form to further improve the final detection performance. Experimental results are presented to examine the detection performance and validate the theoretical analysis.

Statistical analysis of Monopulse-SAR for CFAR detection of ground moving targets

An efficient approach to achieve ground moving target indication (GMTI) for synthetic aperture radar (SAR) is to use the Monopulse-SAR system. This paper examines the statistics of monopulse ratio (MR) for SAR/GMTI model when complex Gaussian clutter-plus-noise is considered. The probability density function (pdf) of MR is analyzed in detail. Especially, the conditional likelihood function of MR under the null hypothesis is given in a closed-form defined by special functions. An automatic constant false-alarm rate (CFAR) detector for moving targets is provided and extended to a multi-MRD form to further improve the final detection performance. Experimental results are presented to examine the detection performance and validate the theoretical analysis.