Research On Satellite Interference Location And Adaptive Beamforming Technology

In satellite communications, satellite platform is vulnerable to all kinds of radio frequency interferences, intentionally or unintentionally. In recent years, the airspace anti-interference technology based on adaptive antenna array is widely used in the satellite communication system to solve the interference problem. The basic idea of airspace anti-interference technology is to null the antenna pattern of antenna array in the direction of interference sources and maximize antenna pattern gains in the direction of desired signal, by the adaptive adjustment of weighted coefficient of each array element on the basis of interferences and signal environment. From the perspective of spatial filtering, interference sources locating technology and adaptive beamforming technology can be combined effectively to achieve high performance of spatial filtering. Therefore, the two key questions of achieving high performance of spatial filtering are how to estimate the direction information of the interference sources quickly and accurately and how to use the direction information of the interference sources to realize adaptive nulling. In this background, this dissertation launches the research from two aspects: interference sources location and interference suppression. In terms of satellite interference source location, spatial spectrum estimation technology has laid a solid theoretical foundation for the high precision and high resolution positioning of interference sources, and the directions of interference sources can be estimated accurately for a single satellite by applying spatial spectrum estimation technology to antenna array signals. In the aspect of interference suppression, we can use the adaptive beamforming technology combined with the prior information of the interference sources location to realize the suppression or elimination of interference sources in the airspace.In this dissertation, we carried on a research to narrowband signal DOA estimation algorithms in the basis of a small number of snapshot data received by uniform linear array. We proposed a method of DOA estimation based on extended pseudo covariance matrix, a method of DOA estimation based on vector reconstruction and a method of DOA estimation based on singular value decomposition and coherent accumulation. We also extend a kind of single snapshot DOA estimation method based on data preprocessing. The performances of the four DOA estimation methods are simulated and analyzed under the condition of coherent interference. On the basis of the wideband coherent source signal model, we improved a method of coherent wideband signal 2-d DOA estimation algorithm based on angle frequency separation for broadband focusing, and made a brief analysis of how array configuration affects algorithm performance. On the premise of interference sources DOA information is known, we conduct a study on adaptive beam-forming algorithm with DOA information. A beamforming algorithm based on uncertain set and projection subspace, and a correctional multi-beam constrained minimum variance beamforming algorithm based on the feature subspace are proposed, both of which have a good performance in terms of array output SINR and robustness.