| The real-time monitoring of the marine environment is of great significance to the construction of maritime power.Some useful ocean parameters can be obtained by inversion of radar images,but rainfall interference will adversely affect it.The detection and suppression of radar rainfall interference can provide a guarantee for the effective inversion of ocean parameters.This paper is based on the national defense project of "Shipboard X-Band Navigation Radar Inversion Wave Technology",and based on a large number of original image data of X-band navigation radar and rainfall data.The detection and suppression techniques of rainfall interference in radar echo signal are studied in this paper.In this paper,the rainfall interference detection and suppression technology of navigation radar are divided into three steps: rainfall interference detection,rainfall intensity inversion and rainfall interference suppression.Aiming at the detection of rainfall interference,this paper proposes two methods for detecting rainfall interference in the measuring area of ocean waves,which respectively from the spatial domain and the wavenumber domain on the premise of the spatial heterogeneity of rainfall.Firstly,by studying the difference of echo in spatial domain of radar image,it is found that there is a significant difference in the mean value of echo difference between rainfall and non-rainfall in radar image wave monitoring area.Based on this phenomenon,a radar image rainfall interference detection algorithm based on echo difference is proposed.The distance of calculating the echo difference value was redefined,and it takes the mean value of the echo difference value within the selected range of the wave monitoring area as the parameter to detect regional rainfall interference in the wave monitoring area of the radar image.Secondly,the effect of rainfall interference on the energy distribution in the wave number energy spectrum of radar image is verified by experiments,and it is found that the energy ratio of wave number decreases gradually with the increase of rainfall interference.Based on this phenomenon,a method of rainfall interference detection based on the characteristics of wave number energy spectrum is proposed.The wave energy ratio in wave number energy spectrum is taken as the detection parameter.Through the analysis of the data of the difference value of echo and the energy ratio of wave number under different rainfall conditions,the appropriate threshold is set up,and the correction of different wind speed is carried out to detect the rainfall interference.The measured data proves that the algorithm is more suitable than other traditional methods in the wave monitoring area.The suppression of rainfall interference needs the auxiliary explanation of rainfall intensity.Aiming at the inversion of rainfall intensity,the inversion of rainfall intensity is carried out by using the mean value of echo difference and the energy ratio of wave number segment in this paper.The relationship between two parameters and rainfall intensity was determined by experiments,and the two rainfall intensities are combined to obtain the final value and determine the rainfall intensity level.The experimental results show that this method has a good precision in the inversion of rainfall intensity and provides data support for the suppression of rainfall interference.For the suppression of rainfall interference,because the radar image during the heavy rain has been seriously damaged,there is no inhibitory significance.In this paper,only slight and light rain interference is filtered in wavenumber domain to suppress rainfall interference,and the reliability of wave parameter inversion before and after suppression is analyzed.Other radar images only output rainfall intensity and do not invert wave parameters.Finally,the whole design of rainfall interference detection and suppression technology of navigation radar is carried out in this paper. |
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