Compression Of Radar Data

Radar(Radio Detection And Ranging) detect the objects in the space and estimate the objects' parameters ,such as distance,azimuth,angle of elevation,velocity,by transmitting radio wave. In national economy,it is used in navigation,weather forecast,geological mapping,military affairs and so on. The information collected by radar is all included in radar echo,to save or transmit radar echo needs a vast amount of memory capacity or band width,so how to spend littler memory capacity or band width is the primary duty of radar data's compression.At first,this paper gives an overall introduction to the basic theories of matching filter and the properties of linear frequency modulation signal,preprocessing the radar data by the matching filter will give advantage to improve the compression performance in later processes. Secondly,we bring statistic coding,prediction coding,transform coding and analysis & synthesis coding into radar area. According to the properties of radar data,we take 4 methods,which are Huffman coding;prediction error model and LZW coding;FFT,uniform quantization in each frequency bank and Huffman coding;wavelet transform,uniform quantization in each frequency bank and LZW coding,to compress the genuine ground clutter radar data and give the corresponding results. In the fifth chapter,author improved Huffman coding and LZW coding,which can not only increase the compression ratio,and also make the programe more useful in varied circumstance. According to information theory,we conclude that lossless compression of radar data couldn't obtain high compression ratio. This point has been verified by the results of the experiments.In addition,the principle and the application of wavelet analysis have been full illustrated in this paper. Wavelet has many good properties,such as multiresolution analysis,constant quality factor and the capacity of representing the local characters of signal in time-frequency field,which make it a useful tool in signal processing,removing the traditional defect of FFT when FFT processes nonstationary signal. So wavelet analysis is suitable for processing radar data which is a kind of nonstationary signal. At the end of this paper,after comparing the four algorithm,author suggests that user chooses the forth algorithm,when distortion is admitted ina certain range.