Study in BDS Triple-Frequency Phase Ionospheric Delay Estimation and Code Hardware Delay Separation Method

Abstract

Precise phase ambiguity resolution is needed to obtain high-precise ionospheric delay with the phase observations, extreme wide-lane (EWL) combination can be easily fixed owing to the long wavelength, MW combination wide-lane (WL) ambiguity fixing may fail because of the influence of code hardware delay, observation noise, and multipath. In this paper, BDS triple-frequency observation and GIM production is applied to fix the WL ambiguity with the fixed EWL ambiguity and phase WL geometry-free (GF) combination, then high-precise ionospheric delay is reconstructed with the fixed ambiguities, also the satellite and receiver code hardware delay is separated. The test results show an obvious improvement of WL ambiguity success rate of fixing, and a systemic bias of 0.5–0.8 m exists between the reconstructed ionospheric delay and GIM correction, meaning an equivalent ionospheric delay correction precision of 3–5 TECU. The separated code hardware delay is stable and the stability of GEO and IGSO satellites is obviously better than MEO satellites, also the code hardware delay bias between different frequencies of IGSO satellites coincides best with DCB estimated from ionosphere modeling.