Design of an optimised carrier tracking loop robust to ionosphere scintillation in GNSS receivers

Abstract

The advancement in the navigation field has promoted the development of both regional newlineand global navigation systems. India is one such country apart from China and Japan which has newlineexhibited self reliance in the navigation field by developing its own navigation system- Indian newlineregional navigation satellite system (IRNSS) renamed as Navigation with Indian constellation newline(NavIC) with nine satellites in geostationary and geosynchronous orbits. Atmospheric factors, more particularly the ionosphere affects are proven to be newlinedetrimental to the effective functioning of navigation systems. Ionosphere delay and scintillation newlineare the dominant sources of errors, affecting the precision of position determination. Further, it newlineaffects the integrity and reliability of the GNSS system by causing loss of communication. The scintillation events are random in nature strongly newlineinfluenced by the solar activity in addition to geo location, local time and seasons and many newlineother geophysical phenomena. One of the objectives of this research is scintillation pattern study newlineover Jain Univeristy station. newlineScintillation degrades the signal tracking performance of the GNSS receivers. (CTL) newlinewhich is the main signal tracking unit of GNSS receiver perform poorly in scintillation condition newlineand lose track of the satellite signal, causing loss of communication. The conventional CTL is newlineanalyzed for its performance limitations and its robustness is enhanced for handling scintillation newlinesignals and optimized for performance by including Kalman filter. newlineKalman filter (KF) based carrier tracking scheme is implemented as an improvement over newlinethe conventional CTL. KF is optimal and a recursive filter which offers two fold advantages: newline newlineone, optimally estimates the parameters of interest from noisy observations. Second, offers newlineadaptable loop bandwidth unlike the conventional one which provides constant loop bandwidth. newlineScintillation signals are characterized as low carrier to noise ratio signal with high dynamics. The newlineConventional CTL is unable to track such signals leading to loss of lock of the signal. Kalman newlinefilter based CTL (KFCTL) offers loop bandwidth which is adaptable to signal conditions i.e., newlineKFCTL is tuned according to signal parameters and hence performs better than conventional. newlineThe KFCTL is tested over the conventional and the results are presented newline