Key Technique Of The High-Accuracy Synthesizer And Frequency Transmit

The accuracy of Time and frequency measurement is highest in the physical quantities, that is about four orders of magnitude higher. So many basic and precision physical measurements are achieved in the form of frequency measurement. In addition, time and frequency technology is also widely used in navigation, orbit determination, communication, military defense, industrial production and so on. In summary, time and frequency technology represents the forefront of technological. And it has a profound impact that directly promote the development of the level of human nature, and directly contributed to the development of many applications in human life.The technology of Time and frequency includes many aspects such as frequency generation, maintained, transfer and measurement. And generation of high stability frequency signal is the prerequisite technology for the others.Atomic clock is the equipment produces the precision standard of frequency. It generats highly stable single-frequency signal with locking the local source to the reference frequency of atomic transition spectrum. Since the frequencies are different between the atomic transition and the local frequency source, it requires a low noise frequency synthesizer as a key equipment. For the cold cesium atomic fountain clock, the purpose of the synthesizer is to converting the 5 MHz of the local frequency source to the 9.192 GHz of hyperfine transition frequency. In order to reducing local frequency source instability deterioration level to the clock(Dick effect), the additional noise level of the frequency synthesizer link must be far lower than the local oscillator source. For optical atomic clock, the frequency of local frequency source is same with the atomic transition. However, in the development and applications of optical clocks, it requires optical comb to convert the laser frequency to microwave frequency, in which femtosecond laser is fully controlled.In this thesis, works are around the atomic frequency synthesizer, which is commenced into the following parts:(1) Describing structure and composition of cesium atomic fountain clock, based on the implementation of cesium atomic fountain clock experimental device. And it is focused on the 9.2GHz synthesizer frequency designing(with the technology of PLL+DDS) in cesium atomic fountain clock. And it gave the structure designing and performance testing, and finally the closed loop results of cesium atomic fountain clock.(2) Introducing the structure and composition of new space atomic clock, such as POP and CPT atomic clock. Both details of the experimental setup and implement was list. And the major work was concentrated on the frequency synthesizer and associated circuitry design in the POP CPT based atomic clock. Both development and improvement is described. Finally, we test the stability results of the atomic clocks.(3) It is the work introduction around the femtosecond laser in the erbium-doped optical femtosecond optical comb for the Sr atomic clock. Femtosecond optical comb is the most effective tool linking the optical frequency and microwave frequency currently. And femtosecond pulse laser is the core component of femtosecond optical comb. The femtosecond laser we develop has high repetition rate, a very wide dynamic range of the pump power locks, as well as lower intensity noise. This thesis introduced the principle of none-liner polarization rotation(NPR) used in the mode-locked laser device. Using the approach of “pulse track”, we had a numerical calculations and numerical simulations describing the pulse forming process of the NPR mode-locked fiber laser.(4) It is introduced ultra-stable 9.2GHz frequency transfer via a 50 km fiber spool. The experimental system based on the method of phase conjugation stabilization realized real-time noise cancellation. By measuring a round trip phase change signal, phase compensation was realized in real time, substantial increasing the stability of the transmission frequency signal. The method completely relies on circuitry, making a simpler, low cost and more effective structure. With nine days of continuous testing in a lab environment, frequency transfer stability was measured when free running.In this thesis, we not only discussed synthesizer in microwave frequency band, but also in the light frequency band required by the atomic frequency standards. Both theoretical and experimental researches are including. Phase-locked loop and DDS synthesis technology is used in microwave band frequency synthesizer. And femtosecond optical frequency comb is used to achieve light band. In addition, the optical fiber transmission is introduced which has higher performance than the traditional spatial frequency transfer method.