Research On Carrier Synchronization Technology In Satellite Communication On-the-move

This thesis focuses on the Carrier Synchronization Technology for Satellite Communication on-the-move. The work finished in this thesis is a part of a key project undertaken by the laboratory the author works in. The Satellite Communication on-the-move is widely used in civilian and military affairs fields, and the carrier synchronization is one of the crucial technologies.The main works and innovations obtained in this thesis are summarized as follows:1. The mobile satellite communication signal model is given, in which doppler frequency and doppler rate are the most important two parameters. The scheme of modulation information cancellation for PSK,QAM signals are studied, especially the blind scheme of QAM signals. The non-linear functions are adopted to reduce the amplitude modulation information, while the phase modulation information is reduced by the fourth power method. Simulation results show that the modulation information can be effectively reduced by this scheme.2. Several doppler frequency estimation algorithms are studied. The existing algorithms need prior information, and the estimation range is small which is unapplicable to the high-order QAM signals. In order to solve these problems, the cyclostationary properties and high-order cyclic-statistical of the signals are analyzed. Meanwhile, a frequency estimation algorithm based on cyclic-statistical tests is proposed, in which the high order cyclic-statistic of the signal is calculated and the non-zero discrete spectral lines of the cyclic frequency is extracted to estimate the frequency. Modulation cancellation is not needed in this algorithm, and it outperforms the existing algorithms when the SNR is low, and the estimation range is larger.3. The existing estimation methods can not estimate large doppler frequency or large doppler rate, in order to solve this problem, a new joint algorithm of blind doppler frequency and doppler rate estimation based on cyclic-statistical tests and phase difference is proposed. An algorithm based on cyclic-statistical tests is adopted to estimate the frequency, and after the data-aided modulation cancellation, the doppler rate is estimated by the phase difference. Simulation results show that the joint algorithm performs excellently, and the estimation result is close to the real value.4. In non-cooperate communication, the pilot information is usually unknown. So a blind doppler parameters estimation algorithm is proposed based on the cyclic-statistic. By dividing the data, the frequency is estimated in each segment. The doppler rate is derived under the hypothesis that the frequency is linear time-varying. Simulation results show that the proposed algorithm realizes the blind estimation of doppler parameters and fills the gaps in existing algorithms.5. By analyzing the characteristic of the demodulated signals and the frequency modulated signals, this thesis corresponds the doppler parameters to the polynomial phase coefficients of the frequency modulated signal to get the doppler rate, which is estimated by the CP function used in instantaneous frequency rate estimation; by detecting one of the cyclic frequencies of signals, doppler frequency is effectively estimated. Comparing to existing algorithms, this method realizes the joint blind estimation and improves the doppler-rate performance.6. After analyzing exsiting phase estimation methods for QAM signals, this thesis focuses on the full constellation decision method. Combining with the frequency estimation method based on the cyclic-statistical tests, a carrier synchronization track loop is proposed. The doppler frequency is estimated by the algorithm based on the cyclic-statistic first, which slows down the input frequency value of the loop. Simulation results show that the novel algorithm realizes the accurate track for the doppler time-varying frequency of both square and cross QAM signals.