Multipath Characteristics Analysis And Modeling Technology Research Of GNSS Signal

Satellite navigation system uses receiver to measure satellite signal to realize the positioning.Multipath effect is one of the most important factors that affect the positioning accuracy.Multipath error is so closely related to the receiver's working environment that can't be eliminated by the difference technique,and is very hard to establish an accurate mathematical model to describe it.Therefore the research on multipath is a key point in the field of satellite navigation.This thesis carries out some analyses on multipath characteristics of satellite navigation signal,through the multipath parameters estimation algorithm.At the same time it studies some key technologies of multipath modeling.Due to the high correlation with direct signal,multipath signal is difficult to detect and extract.This thesis uses Coupled Amplitude and Delay Lock Loops(CADLL)algorithm to realize the estimation of multipath features.It designs and achieves a GNSS software receiver with multipath estimation function,which can detect a multipath signal whose code phase delay is no less than 0.1 chips and relative amplitude with direct signal is no less than 0.05.A multipath signal can be characterized by four parameters as its relative amplitude with direct signal,code phase delay,carrier phase offset and carrier phase rate.This thesis performs some analyses on multipath characteristics of GNSS signals from different navigation scenes and satellite orbits,and compares the similarities and differences between BDS and GPS signal's multipath.The result shows that,GEO satellite signal's multipath parameters change slowly,while IGSO and MEO satellite signal's multipath have a characteristic of rapid change.Moreover,multipath characteristics are greatly affected by the navigation scene.Characteristic parameters change more quickly in the complex environment.This thesis starts from the existing multipath model,studies the multipath modeling technology based on real GNSS signal data.It verifies the existing models and puts forward a new extension from the perspectives such as multipath life-time.