| Satellite navigation systems such as GPS,Beidou,Galileo,and GLONASS have been widely used,but the shortcomings that they are susceptible to interference are also exposed.Therefore,improving the anti-jamming performance of satellite navigation systems is critical to their further use.Based on the application of antenna array receiver of satellite navigation system,this thesis analyzes the influence of channel characteristics in anti-jamming and researches the optimization algorithm,in order to solve the bottle neck problems encountered in engineer applications and to further improve the performance of anti-jamming.Besides,for the sake of measuring the pseudo-range with high precision in the circumstance of jamming and anti-jamming,this thesis also studies the anti-jamming algorithm of antenna array with ranging deviation constraint.The main tasks of the paper include:(1)Classifying the main transmission channel characteristics that influence the performance of antenna array anti-jamming,including the dispersion effect,amplitude-phase characteristics and multipath of jamming.It can be concluded that many characteristics of transmission channel,such as its dispersion effect,amplitude-phase characteristic and multipath of jamming,can be treated as an equivalent filter,so as the weight of time domain taps of space-time adaptive filters,and this equivalent filter is used to equalize the effect of transmission channel.The performance of this equalizing increases with the number of time domain taps.Simulation results suggest that the performance of anti-jamming is strongly affected by the dispersion effect,amplitude-phase characteristics and multipath of jamming.However,this problem of transmission channel effect can be successfully solved with the help of space-time adaptive filter.It can be known from the real data test that in the circumstance of single interference whose interference noise ratio is 50 dB,the performance of anti-jamming deteriorates more than 30 dB because of the transmission channel effects.(2)Optimizing the anti-jamming algorithm to mitigate the effect of transmission channel in three aspects: the selection of reference element,the optimization of the time domain tap number in the space time adaptive processing,and the relative correction of each array metadata.The selection of reference element should be based on the fact that the selected element has the best correlation with other elements,because the characteristics of channel lead to the difference of correlation among array elements,and the anti-jamming performance is improved with the increase of correlation.As for the number of time domain taps,the selection of it should make a balance between the anti-jamming performance and the convergence speed of the algorithm,and this thesis proposes a preferred loop based on the minimum output power of the array to achieve that goal.Besides,in order to enhance the mitigation of jamming,the received data of the selected array element is used as the reference signal in this thesis,and the channel correction is performed to increase the correlation of data between the reference element and the others by applying the LMS algorithm.Simulation and real data results both show that the performance of anti-jamming can be significantly improved using the proposed algorithm of reference element selection,number of taps optimization and array element data relative correction.The real data test shows that the proposed three methods can improve the performance by 3dB,10 dB and 15 d B respectively in the circumstance of single interference whose interference noise ratio is 40 dB.(3)The pseudo range measurement value of navigation signal will be biased in antenna array anti-jamming algorithm applying power inverse criterion.The mathematical deduction and simulation show that less than 0.4ns bias will be induced by spatial domain anti-jamming algorithm while more than 10 ns for the space-time anti-jamming algorithm,considering using a 4 half wavelength element circular array at the frequency of B3 of BeiDou signal.However,in the situation where the transmission channels are not perfect,the performance of spatial domain anti-jamming algorithm will decrease,leading to a reducing availability of navigation signal.In order to solve this problem,this thesis proposes a reference matrix element direct-pass spatial domain adaptive interference suppression algorithm for relative correction of array metadata.In this algorithm,whose essence is to suppress the interference of the navigation signal,the constraint of time delay guarantees the distortion-free transmission of the navigation signal in the reference array element,so that the array metadata relative correction and spatial domain adaptive algorithm can effectively suppress interference.The simulation shows that in the circumstance of two interferences(wide band Gaussian noise interference with interference noise rate of 60 dB and single frequency interference with interference noise rate of 40dB),assuming the signal comes from elevation 60°and taking the amplitude-phase characteristic into consideration,the performance difference between proposed algorithm and traditional algorithm is less than 1d B.Besides,by both comparing with the pseudo range measurement in jamming free circumstance,the bias induced by traditional algorithm is more than 10 ns while it is less than 0.5ns induced by proposed algorithm and it is only suboptimal to 0.4ns in ideal circumstance.Finally,the research results and application of this paper are summarized.Some of the results of the thesis have been applied to the antenna array anti-jamming receiver of the BeiDou satellite navigation in China. |
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