Research On GNSS Ionospheric Scintillation Monitoring

Ionospheric scintillation is an important factor affecting the accuracy,integrity,continuity and availability of Global Navigation Satellite System.Because of its sudden,occasional,regional and other characteristics,it is difficult to capture and verify in real environment.The study of ionospheric scintillation model is of vital importance to the repeatability simulation and test.Ionospheric scintillation monitoring is also a significant part of satellite navigation signal quality monitoring.The outline of this thesis is as follows:(1)For the Cornell model,the phase scintillation index is not controllable and the AJ-Stanford model lacks the limitation of scintillation frequency.A three-parameter Ionospheric Scintillation model based on Cornell model is proposed.The results show that the phase scintillation index can be controlled accurately by standardization under the condition that the scintillation frequency is not strictly limited.(2)The tracking performance of a second-order phase lock loop under the influence of ionospheric scintillation is quantitatively analyzed from two aspects:carrier cycle slip and tracking threshold.The performance of four typical carrier-to-noise ratio estimation algorithms is analyzed quantitatively from three criterions:estimation error,stability and complexity.The results show that additional noise channel method can achieve unbiased estimation as well as taking into account both stability and complexity.(3)Aiming at the demand of high precision monitoring of ionospheric scintillation,a high accuracy measurement method of phase scintillation based on a second-order phase lock loop parameter optimization design is proposed.By establishing a two-dimensional parameter optimization model,taking the carrier phase measurement precision as optimization target,the loop bandwidth and damping ratio of the second-order PLL are optimized.It is shown that main effect of the optimization target is the loop bandwidth and under weak phase scintillation(phase scintillation index ?_?=0.1 rad),the phase measurement accuracy can achieve up to 0.003 cycles.