The Design And Realization Of L-Band Direct Digital Frequency Hopping Synthesizer

The invention of Direct Digital Synthesis (DDS) is the revolution of signal frequency synthesis technology. DDS has shown its advantages increasingly along with the development of microelectronics technique. Now it has been widely used in the fields of radar, communication, apparatus, etc.This paper first introduced the concept and development of frequency synthesis, as well as the present situation and the trend of development of the direct digital frequency synthesis technology. It has analyzed the principle and the basic structure of DDS, it also has carried on the theoretical analysis to the ideal DDS frequency spectrum characteristic. For the effective suppression of DDS spur, the paper has discussed three main origins of DDS spur and analyzed influence of the spur to the DDS output frequency spectrum. Last design the circuit based on DDS.Doubling model improves the upper limit frequency and spurious level of DDS in the paper. Doubling model is made of three parts: amplifying element circuit, doubling element circuit and filtering element circuit. The theory and noise analysis are detailed state in this paper. Based on the analysis of double, the design of the system schema and the design of element circuit are detailed stated in this paper. The theory and design of the element circuits are also introduced in the paper. The test results of doubling model are listed in this paper. Doubling model could be applied in frequency source of centimeter-wave radar or electronic system which is strict to input frequency.In the last part of the thesis some suggestions are proposed to further improve the result of frequency synthesis.