The Research Of GNSS Anti-jamming Strategy With Complex Environment

Global navigation satellite system(GNSS) has been widely used in series of fields with the ability of providing positioning, navigation and timing functions globally, all-timely and real-timely. But the received satellite signals are very weak and vulnerable to interference. Although, many anti-jamming measures have been proposed, each one has its advantages and disadvantages. Therefore the thesis most pays emphasis on varied and complex blocking interference in the complexly electromagnetic environment. Firstly detects the interference signals, extracts their time-frequency characteristics, and recognizes their classification based on decision tree theory. Then researches the anti-jamming methods based on three aspects of system self-resistance, frequency domain filtering and spatial filtering at the end of receiver. Finally integrates the two modules into one effective anti-jamming strategy. The main researching content of this thesis are generalized as follows:1. Analyzes the complexly electromagnetic environment receivers faced, builds six typical interferences’ models, and discusses interference parameters. On the base of analyzing the existing anti-jamming methods, the self-resistance of GNSS is analyzed. And the anti-jamming strategy in complexly electromagnetic environment is designed, combining interferences detection recognition procedure and anti-jamming procedure. The related basic theories are giving too.2. The interference detection algorithms in frequency domain are studied. The threshold circle updating detecting algorithm is designed. And the performance is tested and verified in different built scenes. And through analyzing the interference signal characteristics, six feature parameters are extracted, including energy limit factor, spectrum bandwidth, spectral kurtosis, spectral flatness, maximum-to-mean ratio of signal in time domain and energy aggregation. Then the recognition and classification strategy is designed based on decision tree theory. The simulation is done for testing and verifying it.3. In frequency domain, the athematic model of various window functions and the compensation of signal spectrum leak by adding window are researched. Then the reverse adding overlap window is proposed to improve overlap window of FFT filter technology. In spatial domain, the weight iterated reduction of power inverse algorithm is studied in detail. And the optimization from correlation matrix calculation and varied step weight calculation is put forward, which makes matrix calculation and array nulling more accurate. Aiming at the high dynamic scene, the power inverse algorithm is improved by adding differential restriction, which can broaden the nulling of directional diagram. And the detailed calculation processing is proposed.4. Integrating the above interference recognition technology and anti-jamming technology, the integral anti-interference strategy is got. And the performance is analyzed by comparison. Finally, a visual simulation software for GNSS anti-jamming strategy in complex environment is developed by MATLAB GUI, providing powerful support for the subsequently related research.