چكيده به لاتين
Abstract:
Satellite navigation systems provide for the user with the necessary and appropriate access, as well as accurate information anywhere in the world. Signals from satellite navigation systems have two important features: Broadband and low power. These two features make the signals more vulnerable to noise and all kinds of intentional and unintentional interference such as jamming, spoofing, weak signaling and blockage. For this purpose, in this thesis, a vector tracking is among the available methods for coping with weak signals. In fact, vector tracking is one of the best methods to coping of weak signal conditions, which has been of great interest to researchers today. In this method, by combining the tracking loops and the navigation, the independence in tracking different channels is eliminated, and if the signal conditions are weakened in one or more channels, it can use the other channel features to continue tracking, thereby locking the signal from Do not miss. Sometimes, the signal conditions are such that there is no vector tracking or precision for locating or, in general, the loops are unlocked. Since the heart of the vector tracking is Kalman filter, the improvement in this filter can be a good idea for these conditions. Since fuzzy logic is based on human knowledge, it can be used for these conditions; in such a way that, given the characteristics of the system, in the event of a signal becoming severely weakened, the vector receiver can lock the signal in the tracking loops. The results show that the use of fuzzy logic in adaptation the important matrices R, Q, and P used in the Kalman filter significantly improved the resistance of the receivers in extremely inappropriate conditions than conventional vector receivers. In this thesis, also with the help of practical data collected, the intelligent vector receiver function has been evaluated, so that the proposed intelligent vector receiver can withstand a weak signal of about 25 seconds in very poor signal conditions while only 5 satellites are available. However, the traditional vector receiver could not resist in these conditions for more than 8 seconds.
Keywords: GPS, Weak Signal, Vector Tracking, Kalman Filter, Fuzzy Logic, Fuzzy Vector Tracking.
