Linear Frequency Modulation Interference Suppression For Satellite Navigation Receiver With Single Antenna

With the development of the Global Navigation Satellite System(GNSS),satellite navigation receivers have been widely used in the fields of national defense and national economy.However,satellite navigation signals are very fragile and vulnerable to radio frequency interference.Linear Frequency Modulation(LFM)signals are widely used in military and civilian navigation jammers due to their broadband non-stationary characteristics,which severely threatens the normal use of satellite navigation receivers.Especially with the development of electronic information technology,the LFM interference signal is not only strong,but also has variable frequency parameters and many components,which makes it difficult for the existing interference suppression technology to ensure the reliability and availability of single antenna satellite navigation receivers.Facing the need to improve the ability of single antenna satellite navigation receivers to suppress LFM interference,this paper analyzes the influence of the LFM interference signal’s chirp turning point and the number of components on the typical fractional Fourier transform domain interference suppression method,and then proposes the chirp turning point estimation and fractional Fourier transform domain interference suppression method.The key research contents are as follows:In the traditional fractional-domain interference suppression method,when there is a chirp turning point in the truncation window,the navigation signal loss is large.Aiming at this problem,an interference suppression method based on adaptive windowing in the fractional Fourier transform domain is studied.First,a time-domain difference-based chirp turning point information estimation technology is proposed to obtain the chirp turning point position and interference period length information of the interference signal.Then,according to the information of the chirp turning point,the window length and position required by the fractional Fourier transform are adaptively adjusted to increase the degree of aggregation of chirp interference signals and reduce the loss of useful signals when the interference is eliminated.In the same simulation scenario,compared with the traditional method,the proposed method can achieve a higher output signal-to-interference-to-noise ratio,so that the normalized mean square error of the output navigation signal is lower.In the multi-component LFM interference scenario,the chirp turning point in the processing window will affect the interference component detection and suppression effect.Aiming at this problem,a method for suppressing interference in the fractional Fourier transform domain based on the chirp turning point is studied.First,a chirp turning point estimation technique based on time domain difference and singular value decomposition is proposed to obtain the chirp turning point interval of the LFM interference signal of each component.Then,according to the interval of chirp turning point,the interference center area is selected to perform the fractional domain optimal order search and bottom noise energy estimation,thereby eliminating the interference successively according to energy in the fractional domain and calculating the adaptive residual interference suppression threshold in the time domain.Compared with the traditional method,the proposed method can better select the multi-component LFM interference suppression sequence and the residual interference suppression threshold.