| Since has been put forward in 1992, Software Radio has made remarkable progress,arose general attention and strong interest in recent years. It was based on theory of modern communication, digital signal processing, and technique of micro-electronics. The key conception of Software Radio is to construct a hardware platform, which has characteristics of commonality, standardization and modularization, then implement different function by software; In order to digitize the analog signal as early as possible, it required make A/D converter as close to RF antenna as possible. However, limited by the current device development level, it is difficult to realize RF signal digitalization. Thus , the prevalent choice is to make analog IF signal digitalized, convert IF signal to baseband by using digital down converter, then accomplish digital signal processing in baseband. Today, the technology of IF signal digitalization is one of technologies be in great progress of Software Radio. IF digitized receiver has becomes one of the most important parts of modern radar system ,communication system, and electronic warfare system. Therefore, it is significant to research into and develop IF digitized receiver.In this paper, the interrelated principle of IF digitalization is introduced at first. Then, we discuss the method to make a project in the purpose of designing a meteorological radar. We introduced the overall design plan of this system. And we analyzed the problems of sample rate, numerical control oscillator, filter designing and so on detailedly. Simultaneously, we made emulation for the design plan. After that we discussed the method to turn the project into reality, the method to realize digital down converter in FPGA is mainly discussed. At last, we integrated this units to be a system. Several tests were done to evaluate the developed system. The result of the tests indicated that the system could work well and the desired requirements could be satisfied. |
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