Study On Delay, Quantization And Motion Adaptability Issues Of Satellite Navigation Anti-jamming Technology

Satellite navigation system is a typical spread spectrum communication system for the basic purpose of pseudo-range measurement. Current study about navigation anti-jamming technology focuses mainly on improving the availability of receivers under interference environment, taking the navigation receiver of user segment as background. When implied to space segment and control segment, anti-jamming and high precision ranging should be taken into accout simultaneously. Beidou navigation system building and terminal development as the application background, around the the two main techniques of "interference" and "pseudo-range measurement", this thesis focuses on delays, quantization and motion adaptabilty problems:Firstly, for the problem of delay variation caused by anti-jamming processing, a new delay estimator model of array receiver is established, and the theory expressions of estimation accuracy and zero value of time delay are derived. The results showed that: when amplitude-frequency response of array filter is an even function and the phase-frequency response is linear, the anti-jamming processing does not change the zero value, but impacts delay estimation accuracy; if amplitude frequency response is further constrained constant, the estimation accuracy can be maximumly maintained; when all channels of the array receiver is corrected to constant amplitude and linear phase, the accuracy of pseudorange measurement can be maximumly maintained. This result provides a theoretical basis for interference in the high-precision satellite navigation receiver.Secondly, for the problem of digital filter design which can hold zero values constant, theoretical proof is provided that the sufficient condition that FIR filter does not change zero value is the coefficients are conjugate symmetric or asymmetric, then the interference algorithm forms of time-domain and space-time are given. Simulation results show that: The time domain filter with symmetrical coefficients can reduce zero value offset from 4ns to 0.2ns; in the case of non-ideal RF channel, when the group delay fluctuation is less than 3ns, the zero offset is less than 1ns. The space-time filter with symmetrical coefficients can reduce zero value offset from 2.5ns to 0.2ns.Thirdly, for the problem of quantization word choice in anti-jamming and spread spectrum receiver, an analysis model of non-uniform quantizer with front anti-aliasing filter is established, and taking the maximum of the SINR at the output of correlator as a design goal, the optimization design of quantitative parameters is studied. Theory and simulation results show that: in the case of no interference, if sampling frequency equals to Nyquist frequency the SNR loss introduced by front-end anti-aliasing filter and quantization can be separated; there are no significant performance difference between uniform quantizer and non-uniform quantizer when the word length is greater than 2bit. Under the interference conditions, word length should increase 1bit when the interference-to-noise ratio increases 6 d B in a given amount of loss.Fourth, to solve the problems faced by the anti-jamming receiver such as circuit oscillation caused by short time pulsed interference and the power instability after anti-jamming, a analog-digital mixed architecture is brought forward which is cascaded by a digital-controlled feedback AGC and a full-digital feedforward AGC, and the algorithms of digital-controlled AGC based on pulse interference suppression and all-digital AGC without multiplication are proposed. The new algorithms can effectively improve the stability of the AGC circuit without increasing the quantization word length, and the additional SNR loss is less than 0.1d B if the shift and truncation operations are used to adjust power and word length respectively.Fifth, for the problem that the performance of airspace algorithm may decline under unstable conditions, an array signal model under the motive condition is established, the influence of angle disturbance and interference intensity on array performance under the existence of zero-point error is quantitatively analysed. Then, a new nulling broadening algorithm based virtual interference is put forward. Simulation results show that: when the MSE of interference angle perturbation is less than 1 °, the nulling broadening algorithm can keep the performance loss caused by null pointing error less than 0.5d B; when the MSE equal to 1 ° and 2 °, the new algorithm can achieve 1.5d B and 2.0d B SNR improvement compared to conventional algorithms.This study is the expansion and deepening of the classic anti-jamming theory in the field of satellite navigation. Some results of this study have been tested in practice and successfully applied to the development of a variety of anti-jamming satellite navigation equipments.