Research On Technique Of Beidou Satellite Navigation Signal Suppressing Narrowband Interference

Beidou Satellite Navigation System(BDS)is a global satellite navigation system independently established and developed in China.The aim is to build a stable,reliable,open and compatible satellite navigation system for global users.Since satellite navigation signals are transmitted from space to the ground through complex space channels and inevitably subject to man-made or non-human interference,it is of great practical significance to develop Beidou narrow-band interference suppression system.In this paper,the time domain method and transform domain method of narrow-band interference suppression technology are studied.This paper introduces linear and nonlinear filtering algorithms for time-domain interference suppression algorithms.The simulation results show that these algorithms are slow in convergence and complex in implementation,and are not suitable for practical engineering implementation.Aiming at the transform domain interference suppression algorithms,the simulation of FFT method proves that the algorithm is simple and easy to suppress narrowband interference.FFT is chosen as the interference suppression algorithms.Based on the statistics of Beidou satellite signal and the narrowband interference model of Beidou narrow-band interference suppression system,the FFT interference suppression algorithm is analyzed and perfected.In this paper,the selection of window fonction,the realization of overlapped frames,the selection of reshuffling method and the selection of interference threshold detection algorithm are all studied,and the narrow-band anti-jamming scheme of overlapped frame with window FFT is determined.By simulating the influence of different window functions on SNR,the Blackman window is selected as the window function.By comparing the influence of different overlap factors on SNR,the overlap factor of the system is determined to be 1/2.Through the comparison between the selection method and the addition method,it is determined that the selection method is the reshuffling algorithm according to the actual situation.By adding the AGC module to the front end of the narrow-band interference suppression module,the saturation of the receiver system can be effectively avoided.Finally,the whole design and realization of Beidou narrow-band interference suppression System are carried out.The Beidou narrow-band interference suppression Algorithm is developed by using chip XC6SLX150.The design and engineering implementation of overlapping frame forming module,window adding module and XC6SLX150 module,threshold detection module,de-overlapping module and so on are completed.In the realization of overlapping framing module,by using 31 MHz write clock and 62MHz read clock and data buffer mechanism to realize the algorithm,the cost of narrowband anti-jamming algorithm is reduced by 50%.The test results show that the narrow-band interference suppression system has good narrow-band interference suppression performance in the range of signal-to-interference ratio from-20 dB to-60 dB,and the success rate of location is more than 95%under the scenes of multi-tone interference,scan tone interference and pseudo code modulation interference.Beidou narrow-band interference suppression system is affected not only by narrow-band interference,but also by broad-band interference.Therefore,in order to make Beidou terminal have a wider application scenario,it is necessary to develop terminal equipment with broad-band and narrow-band anti-interference capability.At the same time,there is still a lot of optimization space for the narrow-band interference suppression algorithm,which needs further research and optimization.This will be the focus of my next work.