The Research OF Ultra-Low Phase Noise Synthesizer

A variety of spacecraft reference frequency source are implicated in the satellite based applications such as gravity field measurements, communication, and navigation and deep-space exploration. The system made increasingly stringent requirements, especially on stability.In this paper, the universal type of10MHz Ultra-stable oscillators (USO), rubidium atomic clock and hydrogen atomic clock are applied as reference source to generate the special frequency points. The features of reference source are well transferred to target frequency point with the frequency synthesis technique. The development cost and cycle are shortened; the screening of the crystal for special frequency is avoided.In this paper, the principle and characteristics of direct digital synthesis (DDS) are discussed based on the study of frequency synthesizer technology. For the key technologies of gravity field measurement-USO in K band ranging system (KBR), the DDS-frequency division-mixing solution are given.The feasibility is discussed. The design of frequency synthesis circuits is given, furthermore, the reliability of DDS circuits are analyzed. Two prototypes are developed. The measurement shows that the clutter suppression is better than92dBc and short-term stability is achieved to2.32X10-13/s while1.5X10-13/s of reference source.The two months of joint tests prove the prototypes are met the system requirements with high stability. The KBR project successfully passed the full test.