Research On Statistical Amplitude And Phase Distribution Models Of Sea Clutter At Low Grazing Angles

The analysis and modeling of sea clutter is widely applied in many aspects,such as radar system design,sea target detection,ocean remote sensing,over ocean communication and so on.So far,there have been two main methods in modeling sea clutter,random rough sea surface modeling and the statistical distribution clutter based on the measured sea echo respectively.However,each of these modeling methods has its own limitations.In this paper,the model of sea clutter based on combination with the measured sea data at grazing incidence and the distribution of the amplitude and phase is presented,and a statistical model which includes the amplitude and phase distribution of sea clutter is established.According to this statistical model,sea clutter at grazing incidence condition is generated rapidly.The main contributions of this paper are as follows:1.The electromagnetic scattering method of sea clutter has been studied in this paper,the modeling of the random rough sea surface is summarized.The time-varying sea surface are calculated by using the small efficient slope facet electromagnetic scattering model and then sea clutter sequences including I/Q channel are generated.The statistics traits including clutter's probability density distribution(PDF)based on physical model under the Ku band are provided.To verify the validity of the small efficient slope facet model,the simulated ea clutter of the time-varying sea surface is compared with the measured sea clutter data.It is found that the PDF of simulated sea clutter is similar to that of measured clutter,and both of these present the Gaussian distribution.Hence,the small efficient slope facet model is effective and can be utilized in engineering design2.The sea clutter modeling based on statistical characteristics is provided as well,including Rayleigh distribution,Weibull distribution,K distribution,etc.The Zero Memory Nonlinearity,(ZMNL)and the Spherically lnvariant Random Processes(SIPR)are used to simulate the sea clutter,and the measured data of IPIX radar is used to calculate the parameters of the sea clutter statistical model(K distribution).Through this way,the amplitude data of sea clutter at grazing incidence condition are generated.To sum up,by introducing the measured IPIX radar data,the method including ZMNL and SIPR can meet the requirement of the sea clutter simulation better.3.After the introduction of the concept of random field of echo sequence,the expressions of joint Gaussian distribution are given.By assuming normal distributed and correlated real and imaginary scattering components,we derive analytical probability density functions(PDF)for the sea amplitude and phase.The phase and amplitude distribution of sea clutter under different radar distance gates and different sea conditions are studied based on the IPIX measured data at grazing incidence.It is found that the amplitude distribution of clutter in high sea condition tends to have high value and the phase distribution of clutter tends to be uniformly distribution during a long period of accumulation.Besides,the sea clutter amplitude and phase sequence satisfying the required conditions is generated by the Monte Carlo method.So,the data of sea clutter at the grazing incidence are obtained.Finally,the simluted amplitude and phase distributions are in good agreement with the measured sea data.