Design Of Frequency Synthesis Source For X - Band Radar Scattering Imaging System

Nowadays, it has been greatly improved by modern radar technology that detecting and tracing target, so that stealth technology, which mainly depends on Radar Cross Section, has become an effective way to enhance capabilities of surviving and attacting. Compared with theoretical calculation, radar imaging has been widely used in obtaining characteristics of goals quickly and precisely. Meanwhile frequency systhesizer of X-band has been widely used in radar imaging field with its high resolution, good stability, strong anti-interference ability and other characteristics.Based on the actual project, radar imaing, direct digital frequency synthesis (DDS) and phase-locked loop (PLL) technologies are studied in this paper, and a frequency synthsdizer of X-band controlled by console is developed.Firstly, basic principle of radar imaging and categories of radar scattering center as well as their own scopes of application are introduced. Also the vertical and horizontal resolutions of radar imaging are focused on. A detailed discussion of direct digital synthesizer’s (DDS) structure in realization and principle of each module is undergoing. Meanwhile, the advantages of DDS are briefly introduced and the mathematical model of DDS is reducted step by step then. The characteristics of idea DDS spectrum are analysed afterwards to determine spurious noise sources, and then two effective methods to suppress them are given.Secondly, Phase-Locked Loop (PLL) structure is introduced, which focuses on principles, components as well as indicators of each module. PLL phase module and its equation are also given then. In the end, three characteristics of PLL are disscused, which includes phase noise characteristic, spurious noise characteristic, and PLL stability when subjected to interference in "synchronization state".Thirdly, technical specifications of system are given. Also four common solutions are proposed and meanwhile working principle, advantages, disadvantages and application of each solution are introduced afterwards. The selection of DDS, PLL and CLOCK chip is disscused in detail. As a result, block diagram of system is given in which external PLL multiplier is adopted as DDS reference frequency. Afterwards, the feasibility of the program given above is demonstrated in output frequency, phase noise and spurious.Finally, frequency synthesizer of X-band is completed according to project requirements. In hardware design, FPGA is selected as MCU of system. Moreover, based on system function, system is devided into FPGA module, data storage module, data communication module, DDS module, PLL module and power module. Afterwards, detailed design of each module is undergoing. In software design, relying on chip selected, FLASH module, USB module, DDS module and PLL module are not only studied but also simulated then. At last, in cooperation with console, system debugging is completed, which shows that system works stably, which accomplishes each basic function.