GNSS Non-stationary Interference Suppression Technology Based On Time-frequency Analysis

With the continuous development of electronic information technology,electronic warfare is gradually becoming a new form of military operations,and electromagnetic space has become one of the main battlefields of new types of warfare.Navigation confrontation is a form of electronic warfare that aims to interfere enemy's satellite navigation equipment while ensuring that one's own satellite navigation equipment is not affected by enemy's interference.Improving navigational confrontation ability can make a sense of winning a electronic warfare.Fast-sweep interference is a kind of high-efficiency GNSS(Global Navigation Satellite System)non-stationary interference.It is being widely used in navigational defense.The time-frequency joint analysis technology can effectively analyze the time-frequency characteristics of non-stationary interference signals.So it can be used to suppress the GNSS non-stationary interference.Based on the above situation,this paper focuses on the following topics:(1)The mathematical model of fast sweep frequency interference is established,which proves the non-stationary nature of fast sweep frequency interference.The navigation interference and anti-interference indicators are proposed.The confrontation ability and effect of fast-sweep interference are evaluated.It is calculated that when the fast sweep frequency interference bandwidth is equal to the signal bandwidth and the center frequency is the same as the signal center frequency,the fast sweep interference will have the best confrontation ability with its interference effect close to the single tone interference,and its interference efficiency is the highest and better than traditional stationary interference.(2)An algorithm for calculating the fastest sweep speed of the fast-sweep interference that traditional anti-interference receiver can suppress is proposed based on the carrier-to-noise ratio loss.And a simulation experiment platform is established By theoretical derivation and simulation,it is concluded that when the sweep speed of the fast sweep frequency interference is faster than6.82×10~4 MHz/s,the traditional time domain interference suppression algorithm will fail with a large carrier-to-noise ratio loss And for the frequency domain interference suppression algorithm,the fastest sweep speed is related to signal bandwidth and FFT duration of the receiver.(3)A GNSS non-stationary interference suppression algorithm based on short-time Fourier transform is proposed.The Hamming window is selected as the window function used by the short-time Fourier transform.The time-window width selection algorithm based on the receiver's limit performance is proposed.The interference suppression algorithm based on the constant false alarm rate threshold is proposed to detects the interference spectrum and rejects it.To correct the threshold influenced by frequency aliasing,the correction algorithm based on reference value is proposed.A simulation analysis shows that the proposed algorithm can effectively suppress fast-sweep interference,with carrier-to-noise ratio loss below 2d B,and a interference rejection ratio close to the interference-to-noise ratio.The code phase deviation caused by the interference suppression algorithm is below 0.004 chips,and the influence on the positioning ranging accuracy is less than 0.15m.It is conclude that the proposed algorithm is greatly improved on traditional interference suppression algorithms.