Study On Clutter Filtering Technology For X-band Weather Radar

Weather is an important factor in human life,production and military operations.Real-time weather radar detection is the basis of weather forecasting,disaster early warning,equipment experiment and battlefield action.Typical precipitation radars,which have a large coverage and high precision measurement,usually work in the S-band and C-band.S-band radar is usually used in radar detection network of meteorological system,and C-band radar is commonly used for weather detection in airport terminal areas and used in areas with relatively few heavy rains and less severe weather attenuation.Compared with S-band and C-band weather radar,the atmospheric attenuation of X-band weather radar is relatively large,which is not particularly suitable for long-range detection.X-band radar has a smaller size,lower infrastructure requirements and better mobility.It is commonly used in the system of weather modification,weather protection of major experiments/events and proximity forecast of high disaster area.Compared with S-band and C-band weather radar,X-band weather radar faces more serious problems of ground clutter suppression and the contradiction between speed and distance measurement.This subject is oriented to X-band weather radar application requirements,mainly studies key issues of noise estimation,ground clutter decision and clutter suppression in weather radar detection.The goal is to improve the data quality of X-band weather radar.The main work of this paper includes:First,ground clutter filtering technology.The past time domain filters cause damage to the weather signal while filtering out the ground clutter.The adaptive filters analyze the shape of the spectra,adaptively decide where to reduce the clutter power and use Gaussian fit to recover the filtered weather signal.The filtering performance of the Gaussian model adaptive processing(GMAP)technique and the spectral stationary echo filter(SSEF)is analyzed for the strong ground clutter problem at low elevation angle.Then,the estimation performance is validated by X-band measured IQ data of Foshan Meteorological Bureau.Second,ground clutter recognition technology.For a given radar,ground clutter changes with seasons and weather.The anomalous propagation of radar signals can also lead to significant differences within hours in clutter.Therefore,the construction of clutter map is the key technology in radar technology.The ground clutter has an average speed close to zero and a narrower spectral width.A variety of clutter suppression techniques use the characteristics of clutter to achieve ground clutter reduction.However,in rain,drizzle or zero-Doppler lines with strong rainfall,weather echoes and clutter have similar velocity characteristics,so various clutter filtering techniques have some problems of filtering out weather signals.It brings bias to the final reflectivity,speed,spectral width and other radar products.In this paper,we apply the clutter mitigation decision algorithm(CMD),which used in the S-band radar,to the X-band radar,and test the algorithm using the IQ data of X-band weather radar.The results show that the CMD algorithm can effectively identify the clutter.In this paper,the adaptive filter and the CMD algorithm are combined to perform ground clutter filtering,which improves the data quality of X-band weather radar.Third,the noise estimation technology.The noise estimation is the basis for accurate measurement of radar data such as radar reflectivity and differential reflectivity.When strong clutter and/or range folding exist,noise is an important factor influencing the performance of moment estimation in weather radar.For different operating modes,the noise estimation algorithm in GMAP and the radial-based noise power estimation algorithm(RBNE)under clutter are studied.The performance of two algorithms is analyzed by the simulation method and the measured data of C-band.The work on clutter filtering is of great significance to waveform design and signal processing in X-band radar.The work on clutter identification and noise estimation can be applied to weather radars and other ground-based radars.In this paper,adaptive filtering algorithm,clutter recognition algorithm and radial-based noise power estimation algorithm are combined to provide a solution for X-band radar design.