Research On Narrow-band Interference Suppression Technology Of BDS Receiver

In recent years,Beidou satellite navigation system（BDS）has developed rapidly and gradually improved,and has become the national infrastructure,it is closely related to the lives of the public.Because satellite navigation signals are very weak,they are susceptible to various types of intentional or unintentional interference,such as radar signals,signals from broadcast communications and their harmonics,and various types of intentional interference devices.Since the narrow-band interference is simple and easily causes the receiver to work unstable and produces undesired navigation results.Therefore,it is necessary to add the interference suppression module to the receiver.But the current processing methods often produce different degrees of damage to the useful signal,causing loss of C/N₀ and reducing navigation performance.Narrow-band interference suppression in the receiver is the most economical method at present.Considering the complexity,real-time,interference suppression ability and the influence of real navigation signals,the thesis studies the narrow-band interference suppression method based on receiver.The thesis mainly studies the narrow-band interference suppression technology based on single antenna.The research focuses on the narrow-band interference suppression technology based on BDS receiver that can reduce the loss of useful signals while effectively suppressing interference.The main research contents are as follows:（1）According to the composition of the Beidou B1I signal,the Beidou B1I digital intermediate frequency signal is simulated by MATLAB.The correctness of the simulation is verified by the spectrum and the result of acquisition.The common narrow-band interference signals are modeled and simulated to support the verification of subsequent narrow-band interference suppression algorithms.（2）According to the different of correlation between BDS signals and narrow-band interference,the time-domain adaptive filtering technique based on prediction ideas is studied.The least mean square algorithm,the normalized least mean square algorithm and the recursive least squares algorithm are derived and analyzed in detail.The above algorithms are simulated and compared,and the normalized least mean square algorithm with better comprehensive performance is selected as the representative of the time domain suppression technique,it is used to compare the performance with the interference suppression algorithm proposed later.（3）Aiming at the problem of slow processing speed and poor ability to suppress fast-changing interference through the time domain suppression,the frequency domain suppression based on FFT is studied.The method of using 50%overlap kaiser window to reduce the spectrum leakage and signal distortion of FFT.Then aiming at the determination of the narrow-band interference detection threshold,an adaptive interference detection algorithm based on consecutive mean excision is proposed,which has good detection performance and serves as the basis of the subsequent time-frequency domain combination algorithm.Finally,the algorithm is simulated to verify its effectiveness.（4）Considering the complexity,real-time,interference suppression ability and the influence of real navigation signals,a narrow-band interference suppression method based on time-frequency domain combination is designed.Aiming at the problem that the FFT has large deviation of the estimated value of the interference parameter,an algorithm combining FFT and CZT is applied to the accurate estimation of the interference parameters,obtain a more accurate estimation of the interference parameter.And focusing on the time domain notch filter,based on the second-order direct type IIR notch filter widely used in the field,an improved design method based on zero-poles assignment is proposed,the notch filter has a steeper notch characteristic.By simulating analysis,it is proved that the method can reduce the loss of useful signal while ensuring the effective suppression of the interference signal,and has the advantages of low complexity,better real time and being suitable for practical application.In summary,based on the existing narrow-band interference suppression algorithm,the thesis proposes improved method for some content,which has a certain degree of improvement on the performance of the algorithm.