Research On Key Techniques Of Random Noise Ultra-wideband SAR

The modern high-tech war and the increasing complex electromagenic environment present much more challanges to the radar system. The investigation shows: the random noise signal radar possesses excellent electronic magnetic compatibility and target detection performance. This dissertation aims to develop the new system of random noise high resolution imaging radar, especially the study on its key technology, as a foundation to implement the random noise high resolution imaging radar.The summary of our research in this dissertation is as follows:1) The theoretical foundation and some proper imaging algorithms for the random noise ultra-wideband (UWB) imaging radar are studied, and the corresponding simulation results are given. The results show that two imaging algorithms of the wavefront reconstruction and improved back projection are suitable for the application requirement of the random noise UWB imaging radar.2) For the random noise ultra-wideband imaging radar, there are two kinds of power spectrums: Rectangular and Gaussian. The range sidelobe of rectangular power spectrum random noise presents the sinc shape envelope, and the length of the correlation data almost has no effect on its sidelobe level, and the sidelobe level is higher, adopting the apodization filtering technique can suppress effectively the sidelobe whist almost preserving the resolution of original SAR imaging. The range sidelobe of gaussian power spectrum random noise presents the ruleless shape envelope and decreases significantly with the correlation length increase, so it can be suppressed by increasing the length of the correlation data if the instruments are available.3) A hardware platform design scheme of digital random noise signal generator is proposed, and it is successfully implemented by using the devices of FPGA and mass capacity memory and so on. By analyzing the statistic performance of two kinds of random noise signal which are based on the improved Logistic-Map chaos signal and the Zigguart algorithm, for example, the mean, the variance, the correlation function and cross-correlation function, it is demonstrated that these two kinds of random noise signal generated can satisfy the application requirement. 4) The random noise circular SAR is demonstrated for the first time and is accomplished through the simulation. The circular SAR can image the target in the reconnaissance area in all orientations, so it can obtain more and more accurate information. Firstly the model of random noise circular SAR is studied, and then the detailed implement procedure is present.5) The speckle characteristic of random noise imaging radar is discussed for the first time and is obtained. The scattering object in the reconnaissance area is modeled, and the original echo signal of scattering objects is analyzed. The physical mechanism of the speckle generation about the radar electromagnetic wave is discussed. The simulation result shows: The speckle phenomenon exists in the random noise UWB SAR and the LFM SAR, however, the speckle in the latter is worse than the one in the former, and the amplitude variation extension of the range profile of the linear frequency modulation UWB imaging radar is larger about 3～5 dB than that one of the random noise UWB SAR for the radar imaging of a homogenous point target.6) The anti-jamming performance for random noise UWB imaging radar is analyzed and compared with the conventional linear frequency modulation (LFM) UWB imaging radar. The analysis show that the anti-jamming performance of the random noise UWB imaging radar is better than that one of the LFM UWB imaging radar, for example, the peak sidelobe level of the random noise UWB imaging radar shows approximately 9.6 dB improvement over the linear frequency modulation UWB imaging radar under the jamming of the LFM signal (whose frequency modulated slope is different from the one of the LFM imaging radar) and the jamming-to-signal ratio being 10 dB.