The Research Of Time And Frequency Processing Technology Of Rubidium Atomic Frequency Standard

The atomic clock uses the radiation frequencies for atomic transition between hyperfine energy levels to measure time. Because of its accuracy and stability, the atomic clock has become one of the indispensable devices in the fields such as aeronautics and astronautics, navigation, communications and scientific measurement in the past 50 years. Atomic clocks mainly include the physical parts and wiring sections, and are the physical lock system of high stability crystal oscillators, its performances mainly depend on the cooperate of physical parts and wiring sections. Normally, the physical parts cannot achieve the ideal effect because of the influence of some factors such as ambient temperature change and their own aging, and at the same time, wiring parts need complex frequency conversions such as multistage frequency doubling and mixing to lock the jump frequency of the physical part to high stability crystal oscillators, in this process, the introduction of additional noise affects the short-term stability indexes of atomic clocks. We can use line section compensation techniques and time-frequency signal processing techniques of precision frequency link to resolve the insufficient of the physical part and the line section. Based on the widespread use of rubidium atomic clocks, the following aspects are completed in the article:1. Temperature compensation technology aiming at the temperature drift problem of rubidium atomic clocks is researched in this paper. The author uses the stability of the reproducibility that the output of atomic clocks changes with temperature and compensates the rubidium atomic clocks with a direct digital synthesizer, under the premise of little impact on the short-term stability of frequency source compensated, the temperature coefficient of the atomic clock is reduced. The feasibility and effectiveness of the method is validated.2. The question is researched that the long term drift of rubidium atomic clocks results in the decrease of frequency accuracy. The average long-term drift-free characteristics of 1PPS signals from the GPS receiver is used to design a Rubidium atomic clock tame system, which is based on the 1PPS signals from GPS. The author compares the results before and after the improvements and finds that the indicators are effectively improved.3. Line simplification is studied aiming at traditional rubidium atomics. Based on the research of traditional lines, a simplify processing technology of circuits is proposed according to regular changes of Phase groups of phase comparison between the periodic signals, this method is as follows, a special frequency of 13.669375MHz from the VCOCXO is firstly multiplied by 500, then excitation signals from rubidium atomic energy level transitions can be obtained directly, After being locked through the clock tame, the output frequency signal indicators of 13.669375MHz from the VCOCXO are improved. However, the signal of 13.669375MHz often cannot be used directly, we can use precision frequency link technology based on Periodic signals to transmit the signal indicator of 13.669375MHz and owning the high performance characteristics of rubidium atomic energy level transition to that of 10MHz, which are both from the VCOCXO. After the improvement, the indicators of phase noise are improved.