Research On Fine Processing Method Of Sea Detection Radar

The study of sea surface echo data has always been a popular direction in the field of radar signal processing.The study of the characteristics of sea clutter is of great significance to the application of sea clutter modeling and sea surface target detection.With the improvement of radar resolution,the sea clutter under high sea conditions has similar characteristics to targets in both time and frequency domains,while traditional MTI,MTD and constant false alarm detection methods may detect strong sea clutter signals as targets,resulting in excessive false alarms.In response to these problems,this paper will focus on the characteristics of sea surface echo signal,the modeling and simulation of sea clutter,and the target detection of surface warships under high sea conditions.The main contents are as follows:1.Characteristics of sea surface echo signal.Firstly,the sea surface echo data measured by a shore-based radar in three different sea conditions are described,and then the three important characteristics of frequency spectrum,amplitude statistics and correlation are studied respectively.In the study of spectral characteristics,the Welch method and AR model method are used to analyze the spectral characteristics of the sea clutter and the target.The experimental results show that the sea clutter has multiple spectral peaks and a large spectral width in the frequency domain,while the target has a single spectral peak and the spectral width is narrow and the energy is high.In the study of the statistical characteristics of amplitude,four typical distribution models are introduced,then they are used to fit three groups of measured data respectively,and the goodness of fit of each model is tested,and the conclusion that the effect of K distribution is the best is obtained.The study of correlation includes the correlation study of space,time and Doppler frequency.The analysis results show that the spatial correlation distance and correlation time of strong sea clutter are longer than those of weak sea clutter,and the target has a strong frequency correlation,the strong sea clutter has frequency correlation only on a few adjacent pulses,while weak sea clutter has no frequency correlation.2.Sea clutter modeling and simulation.The scattering mechanism method and statistical method are used to simulate sea clutter.In the scattering mechanism method,the classification standard of sea state grades is briefly described,then the three-dimensional sea surface under different sea state conditions is constructed,the RCS matrix of the sea surface is obtained by the dual-scale method,and the sea surface echo signal is generated.In the statistical modeling method,measured data are used to estimate the K-distribution parameters,then sea clutter obeying K-distribution is generated by SIRP method.The probability density curve of simulated clutter is consistent with the theoretical value of Kdistribution,which proves SIRP method can accurately fit sea clutter.3.Research on ship target detection method under high sea conditions.First,the traditional MTI,MTD and constant false alarm detection methods are introduced.Then,two steps of MTI processing and setting protection unit are added to the method of orthogonal projection to suppress sea clutter.The improved method enhances the ability to suppress sea clutter under high sea conditions.Aiming at the difference in frequency correlation between the target and sea clutter,the target distance unit determination step is added in the correlation suppression method,which reduces the possibility of misjudging sea clutter as a target under high sea conditions.Finally,this paper proposes a detection method based on CEMD energy ratio for surface ship targets in high sea conditions.First,the data is processed by twodimensional CEMD,and each range unit signal is decomposed into multiple components.Then calculate the maximum energy-to-remaining energy ratio for each distance unit,taking its value as the detection statistic.Then,the statistical value is detected by constant false alarm,the signal of the target range unit is retained,and the non-target range unit is normalized to the noise level.After processing a large amount of measured data,it is verified that the method proposed in this paper has the effect of reducing false alarms and accurately detecting targets in high sea conditions.