| With the increasing complexity of electromagnetic environment,satellite navigation terminal is faced with severe mixed interference problem,while the traditional anti-jamming structure is not good at suppressing the mixed interference of pulse and narrowband,and the signal carrier-to-noise ratio loss is large.According to the needs of Beidou system construction,and aiming at improving the anti-mixed jamming ability of satellite navigation terminal in view of the shortcomings of impact analysis and suppression methods of narrowband and pulse mixed jamming,this paper is divided into the following three aspects.(1)Deduce the anti-jamming quality factor calculation formula of pulse interference,analyze the influence of pulse,narrowband and their mixed interference on the satellite navigation terminal without anti-jamming structure.Through theoretical analysis,the time domain calculation method of anti-interference quality factor of pulse interference and mixed interference is proposed.The effect of interference is evaluated and the accuracy of anti-interference quality factor is verified by the equivalent carrier-to-noise ratio after simulation signal correlation.The results show that the anti-interference quality factor of mixed interference is smaller than that of single narrowband or pulse interference.When evaluating the impact of pulse interference with different duty cycles,the equivalent carrier-to-noise ratio error of numerical calculation and simulation is less than 0.5d B.(2)Establish mixed interference models with different parameters,and analyze the shortcomings of traditional anti-jamming structures in suppressing mixed interference.The time-frequency domain characteristics of hybrid jamming with different duty cycle and interference intensity are studied,and two traditional anti-jamming structures,narrowband-first structure and pulse-first structure,are evaluated.The influence of hybrid jamming with different duty cycle on anti-jamming of satellite navigation terminal is analyzed theoretically.The traditional hybrid interference suppression method ignores the mutual influence of the two kinds of interference,the interference suppression effect is not good,and the carrier-to-noise ratio loss of the satellite navigation terminal is serious after interference suppression.The simulation and measurement results of typical interference scenarios show that when the jam-to-noise ratio of the two interferences is 30 d B,the carrier-to-noise ratio of the signal decreases by about 5d B.In the case of the traditional structure,the influence of mixed interference is greater than the total effect of single pulse or narrowband.The carrier-to-noise ratio loss caused by mixed interference is greater than 5 d B.(3)The pulse interference detection technology under mixed interference is studied,and the nonlinear fusion suppression method of pulse and narrowband mixed interference is proposed.In order to reduce the interaction between pulse and narrowband interference in the process of interference suppression,the traditional anti-jamming structure is improved.Firstly,the parameters of pulse interference are extracted,then the data segment with pulse interference is avoided by changing the step length of FFT,and narrowband interference is suppressed first and then pulse interference is suppressed.Simulation and measurement results show that when the intensity of narrowband interference and pulse interference is the same,the detection accuracy of pulse interference is more than 96%,and the loss of carrier-to-noise ratio of the nonlinear fusion suppression method of pulse and narrowband mixed interference is2～3d B less than that of the traditional method,and the mixed interference of pulse and narrowband can be suppressed more effectively.It is of great significance to support the construction of Beidou-3 ground transportation control system and upgrade of satellite navigation terminal. |
PDF Full Text Request