| Ultra Wideband Through-wall Detection Radar (UWB-TWDR) is a new type of radar based on ultra-wideband technology and synthetic aperture technology. It has the advantages of high resolution, strong penetrability etc., and can detect, locate and image the moving targets behind walls or other barriers. Therefore, it is extremely important in the application of military and civilian.In the thesis, the imaging system of the UWB-TWDR is researched and the synthetic aperture imaging with its fast realization is mainly discussed. The primary contributions are summarized as follows:1. According to the characteristics of UWB signals, the basic UWB beamforming theory in frequency domain is analyzed. Derivation process, as well as simulation is derived, which provides academic supports for the imaging methods.2. Considering the electromagnetic interference (EMI), the mathematical model of the echo is built. In order to separate the clutter and noise from the useful signals, the technologies such as waveform average, median filter, wavelet decomposition and singular value decomposition (SVD) are introduced. Experimental results show that the above methods are correct and effective.3. To overcome the disadvantage of low location accuracy in conventional imaging method based on delay-and-sum beamformer, the weights obtained by minimal variance distortionless response and coherence factor (CF) are applied to optimize the imaging process. And the experimental results indicate that the improved algorithm has higher resolution and better target-to-clutter ratio.4. To meet the real-time requirement, an improved algorithm based on Cordic algorithm is proposed. Then the improved-Cordic algorithm, along with Newton’s iterative algorithm, is introduced into the UWB-TWDR imaging system to simplify the time-consuming process of square root operation. The simulation of DSP units shows that the accuracy is guaranteed and the capability of real-time processing of the imaging system is increased greatly. |
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