C-band Step Study Of The Low Phase Noise Frequency Synthesizer Design

Frequency synthesizer is the key component in electronic systems, whose performance directly affects the capability of various systems such as radar, navigation system, etc. Nowadays, by the development of modern electronic communication technology, higher requirement has been presented. In various high performance, wide dynamic range frequency convertings, phase noise is a main limiting factor. As an important target of frequency synthesizer design, phase noise determines system's sensitivity and selectivity whose design is being the emphasis as well as nodus at all times. Fine resolution is used to largen the capability of channels as well as to improve the system agility.The design tried to develop high performance frequency synthesizers especially fine resolution and low phase noise frequency synthesizers.Firstly, this paper summarized the development of frequency synthesizers in recent dozens of years. Then according to the emphasis of the design, went deeply into the theory of PLL frequency synthesizers widely used, described PLL's working principle, structure and several types in detail, and made research and analysis of PLL frequency synthesizers'phase noise, including the effect of the active loop filter on the phase noise, and give some methods to make improvement as well, such as changing loop filter form, reducing divide number, and increase phase detector frequency, etc. Then paper introduced the principle character and phase noise analysis of Direct Digital Frequency Synthesizer(DDS) and injection phase lock circuit, which are also important circuits in the design. DDS is used to achieve fine resolution, while injection phase lock circuit is used to realize low phase noise high performance input reference frequency. Finally, the production, which is designed and debugged all by myself, C band fine resolution low phase noise frequency synthesizer was introduced by module, including respective schedule, frequency distribution and phase noise experiment results. Then whole circuit phase noise result, picture of spectrum with spur were presented, by which above theory was proved, analysis of the result was given, and the existing problem as well as methods to resolve it were motioned.