Research On Data Acquisition And Real-time Imaging Processing Technology Of Wideband Radar

As the basic of space target identification, high resolution radar has the ability to provide the shape and structure information of targets. This dissertation centers on the key technology of high resolution radar signal acquisition and processing. It has conducted deep researches on echo simulation of ISAR targets, digital quadrature demodulation, ISAR real-time imaging, design of high-speed and high-precision data acquisition circuit as well as high-speed data transmission. The dissertation is composed of three parts:In the first part, this dissertation studies the methods of echo simulation of ISAR targets and digital quadrature demodulation. Firstly, according to the moving characteristic of space targets, the model of target echo signal which has been processed by Stretch technology is established, and ISAR imaging simulation is conducted on the simulated echo data. The stretched echo signal of stationary target is simulated based on the echo simulator which is designed by the dissertation. Secondly, on the basis of polyphase filtering theory, this part obtains the mixer-free structure, which is mainly constituted of low-pass filters. The effect that filter parameters bring to the quadrature demodulation is discussed, and the quadrature demodulation module is designed and realized on the platform of FPGA.In the second part,ISAR real-time imaging technology is researched. In order to overcome the poor accuracy of conventional range alignment algorithm, the accurate distributed characteristic of the correlation coefficients of echoes is analyzed, and the refined offset value is calculated by polynomial-fitting method, then the frequency shift characteristics of Fourier Transform is used to complete the shift of envelope. The results of experiments on real data shows that polynomial-fitting method is suitable for real time ISAR imaging due to its high precision and low calculation. The imaging methods are implementted and optimized on the radar real-time signal processing platform which is based on multi-DSPs, which results in the realization of two dimensional real-time imaging. On the basis of direct-acquisition data, digital stretch method is researched in order to overcome the disadvantage of analog stretch. Real data is processed, indicating that digital stretch method can reach excellent performance as well as reduce the quantity of data. The result provides theory base for real-time imaging on direct-acquisition data.The third part focuses on the design and implementation technology of hardware circuit. According to requirement of the project, this part proposes the hardware design structure of data acquisition workstation. The card used for sampling and simulating stretched echo is designed and tested. The results indicate that all the indices meet the requirement of the project. Making use of this hardware platform, high speed data transmission technology based on PCI9656 and optical fiber is studied. The software design of this workstation is achieved, and the primary combined debug of the sub-system has been accomplished.The researching achievements of this dissertation ensure that development of the data acquisition and processing sub-system go on well, providing important technical support for data acquisition, processing and real-time imaging technology.