Sea Clutter Suppression And Target Detection In Complex Environments

Sea clutter suppression and target detection in complex environments have always been a key research for researchers.However,the complexity of the sea environment makes the research in this field many challenges.In order to solve this problem,in this thesis,we study the distribution models of sea clutter and the relevant theory of target detection after clutter suppression from the perspective of sea clutter characteristics and detector design,and on this basis,several detection methods under the background of sea clutter are proposed.Therefore,the detail research contents of this thesis include the follows.1)Firstly,we analyze the background knowledge about sea clutter suppression and target detection,and introduce the formation mechanism of sea clutter,the basic physical characteristics in time and space of sea clutter.The in-depth analysis is carried out,and the influence of the parameteron each distribution model is studied.Finally,we introduce the data used in this thesis and its related parameter.2)In view of the serious tail of sea clutter under the high-resolution radar,we should consider the fitting accuracy of the measured sea clutter data by the Compound Gaussian distribution.resorting to the texture,we propose a texture-based Minimum Mean Square Error(MMSE)estimation algorithm and a texture-based maximum a posteriori(MAP)estimation algorithm and apply them to deduce the detectors in the Inverse Gaussian Distribution(IGD)and the Generalized Gaussian Distribution(GGD),respectively.At the same time,combined with Generalized Likelihood Ratio Test(GLRT),four detectors are derived and named as MMSE-IGD-GLRT,MMSE-GGD-GLRT,MAP-IGD-GLRT,MAP-GGD-GLRT.From the theoretical analysis and experimental results,the proposed four detectors have better detection performance.3)Considering the clutter suppression of Orthographic Projection(OP)and Singular Value Decompositon(SVD)from the perspective of subspace decomposition,we propose a clutter suppression method based on SVD in projection space.We construct a clutter space by using the secondary samples in the received echoes firstly,and obtain an OP operator by projecting on the clutter space,which is a first clutter suppression.Then we add SVD on it,and obtain the second clutter suppression operator in the signal subspace by taking the first Q larger singular values.Finally,the clutter suppression operator is combined with the detection framework of Constant False Alarm Rate(CFAR)to detecte the target,which is denoted as OP-SVD-CFAR.4)Based on the accumulation effect on signal energy by the fractional Fourier transform(FRFT),the sea clutter data measured by radar is converted into the fractional domain,and we constructe the clutter space of the secondary sample The clutter suppression operator is calculated by the OP in the clutter space.Due to the energy accumulation of the short pulse sequence in the FRFT domain,the energy gap between the target signal and the clutter signal will expand,so it is better to use the OP for clutter suppression.Finally,target detection is realized by combining the CFAR,and the detector is denoted as FRFT-OP-CFAR.