| With the economic development and social advancement, the demands for the radar ranging in all fields of society are keeping rising. In this context, the design of the RF front-end of a high precision radar system, which is based on linear frequency modulated continuous wave (LFMCW) system, is accomplished.In this paper, the structure of LFMCW radar system is presented briefly and its ranging principle of triangle wave utilizing beat frequency and phase offset is analysed, the ranging formulas and ranging precision is shown respectively as well. On this basis, a compound ranging scheme utilizing both beat frequency and phase offset is put forward. The results of theoretical calculations indicate that the ranging precision of LFMCW radar system has been improved significantly. According to system requirements, the core indicators of ranging radar system are demonstrated and calculated.Secondly, the frequency synthesizer of ranging radar system is designed according to the ranging scheme mentioned above. We completed the design of L-band sweep source by comparing varieties of composite structures between DDS and PLL. The sweep source has deep spurious signal suppression, with the phase noise performance of-98.79dBc/Hz@10KHz,-111dBc/Hz@100KHz,-125.7dBc/Hz@1MHz. Then a X-band frequency hopping source, which shortens the frequency switching time by adopting pre-placing frequency technology, is designed based on chip PE3236. The frequency hopping source has a good phase noise performance of-92dBc/Hz@100KHz,-112.3dBc/Hz@1MHz. Meanwhile, its switching time is less than1ms on condition of100MHz stepped-frequency.The RF front-end of radar system is accomplished based on frequency synthesizer designed before ultimately. The experimental results ultimately complied with the theoretic results, thus verified the feasibility of the ranging radar system. The research work in this dissertation has laid a good foundation for the subsequent development of LFMCW ranging radar system. |
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