Study On The Analysis Theories And Algorithms Of The Time And Frequency Characterization For Atomic Clocks Of Navigation Satellites

Measuring of precise distances and positions is really measuring of precise time in a satellite navigation system. The atomic clock is the on-board time datum for measuring the distance in satellite navigation. And it is also one of the key navigation payloads of the satellite navigation system. The performance of the on-board clock affects the navigation and position directly. Therefore, It is very important to study the time and frequency characterization of the on-board atomic clocks. This dissertation mainly focuses on the analysis theories and algorithms of the time and frequency characterization for the atomic clocks of navigation satellites. The main works and contributions are summarized as follows:1. It is shown that the time deviation (or time error) and frequency-offset of atomic clock can be modeled by a deterministic part and a random part by analyzing its data. The deterministic part is quantified by the addition of a constant time offset, constant frequency offset, constant linear frequency drift and periodic components induced by environmental changes. The random part is characterized by seven independent power-law noises whose characterizations and noise mechanisms are also analyzed. Furthermore, the methods of testing and evaluating the time and frequency characterization of frequency standards are summarized and analyzed.2. Data plotting is one of the most important steps in preprocessing the measurement data for atomic clocks. A simple and effective technique for recognizing and removing outliers is presented. It is important to explain all outliers with the help of running environment of the frequency standard, thereby determining whether they are noise or the abnormal data caused by measurement process. Methods for dealing with phase steps, frequency steps and gaps are also developed. Additionally, the frequency offset and frequency drift are estimated and compared in the case of different kinds of noises.3. The data series of 6-months frequency offsets of three Rb clocks in the vacuum sampled with 100-seconds and the 651-day time errors of GPS Rb clocks and Cs clocks sampled with 5-minutes are processed. It is shown that the daily frequency drifts and the frequency offsets of the Rb clocks in the vacuum are more than 2 orders in magnitude than those of GPS Block IIR Rb clocks and all clocks are obviously affected by the periodic components.4. The methods for time-domain stability analysis of atomic clocks are discussed and their equivalent degrees of freedom (EDF) are studied in detail. The interesting results show that the improvement on the EDF of high frequency noise is more than that of low frequency noise for the overlapped estimators and the total estimators of stability variances, but the inverse...