The Technology Research Of Low Sidelobe Pulse Compression

In radar system, because pulse compression can solve the contradiction between radar’s detection range and range resolution, so it is widely used.And in the process of pulse compression, the choosing of signal waveform is of great importance in the result of the compression. Therefore, it is necessary to research and design radar waveforms of good performance. C urrently, chirp signal(LFM), non- linear FM signal(NLFM) and phase-coded signals are three widely used pulse compression signal.This thesis will describe these three signals and make focus on the simulation study of NLFM signal’s waveform design.Compared with LFM, the NLFM signal can get very low main sidelobe ratio without weighting, so there is no loss of SNR and the main lobe will not be widen.But in some actual radar application,such as some new type of weather radar, because the ground can reflect the level of clutter to-55 d B, in order to measure the intensity o f the rain, so the normalized sidelobe level must reaches below-60 d B, but if you use NLFM to matched filtering directly, under reasonable selection of window function and many other parameters of radar case,the final main sidelobe ratio can only reach abo ut-40 d B. Therefore, how to further reduce the sidelobe level of the signal is very practical and significant.This thesis makes a focus on the low sidelobe pulse compression of the non- linear FM signal and describes several methods to optimize waveform design.Firstly, describes a traditional method to design N LFM signal, which is use the stationally phase principle and based on the reverse window function, the results of the simulation show that using this method to design waveform, after pulse compression, the main sidelobe ratio can reach about-42 d B; Secondly,simulate and analysis another method to optimize the waveform:based on spectral correction technique,the so-called spectrum amendment is to make the compressed output is more close to the ideal window function.through simulation we can find that this technique can suppress the sidelobe in a certain degree.And then, another waveform design method is proposed:baesd on the continuous non- linear FM function,it can be found by simulation that if you reaso nable select the parameters of the FM function and window function,the final effect of pulse suppression is very good,but due to the introduction of the window function,the loss of SNR and broaden of the mian lobe is inevitable;Lastly,also introduces a waveform design method based on amplitude weighting,this method can also be good to reduce sidelobe level of the signal under certain SNR loss and broaden of the main lobe.