Improved Adaptive Hatch Filter Algorithm Based on Code-carrier Divergence

doi:10.3969/j.issn.1000-1093.2021.03.011

Abstract

Abstract: The smoothing accuracy of carrier-phase smoothing pseudorange in single-frequency ground-based augmentation system (GBAS) is easily affected by the ionospheric delay and pseudorange measurement noises. The influence of code-carrier divergence of satellite signal on the smoothing accuracy of Hatch filter is analyzed, and an improved adaptive Hatch filter algorithm based on code-carrier divergence is proposed. The code-minus-carrier is computed using pseudorange and carrier-phase measurements, and its first-order linear model is established. The ionospheric delay rate is estimated by using the least square method. Given the estimated ionospheric delay rate, the pseudorange measurement noise can be separated. A function model between the root mean square of smoothed pseudorange and the ionospheric delay rate, the standard deviation of pseudorange measurement noise and the smoothing time of Hatch filter is established, from which the optimal smoothing time of Hatch filter can be calculated. The verification experiments were carried out by using GBAS prototype. The experimental results show that the adaptive Hatch filter is able to calculate the optimal smoothing time of filter based on the real-time ionospheric delay rate and the standard deviation of pseudorange measurement noise. Compared with the traditional fixed smoothing time algorithm, the maximum position accuracy of airborne differential positioning is improved by 53.19 percent by using the adaptive Hatch filter algorithm, which verifies the effectiveness of the proposed algorithm.

Key words: ground-basedaugmentationsystem, Hatchfilter, ionosphericdelay, pseudorangemeasurementnoise, code-carrierdivergence

CLC Number:

TN967.1

HU Jie， ZHANG Lin， ZHU Yixian， ZHOU Ling. Improved Adaptive Hatch Filter Algorithm Based on Code-carrier Divergence[J]. Acta Armamentarii, 2021, 42(3): 555-562.

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