Research On Location Techniques Of The New NAVTEX System

The old-typed NAVTEX is the system that broadcasts and automatically receives the maritime safety information by means of a Narrow Band Direct Printing telex (NBDP), which is the important part of GMDSS. It has simplex function and it is also lower intellectualizes which can not make it adapt to the development of modern times ship.This paper is based on the old-typed system. Modern communication technology is used to update the system and in the same time the information frequency which is appointed by the IMO to transmit native language is used to release orientation information. Because of this wireless navigation function is added, this made the system fit the need of modernization.It's investigated that the problem related with positioning precision of NAVTEX wireless navigation system, the acquisition and tracking of spreading signal are modeled and realized with simulation tools, the effects of multi-path signals are investigated in great detail.Based on the theory of spread spectrum communication and range positioning system, the paper puts forward direct spread system, so the paper introduces basal theory about spectrum communication and navigation. The radio broadcast character is one of important factors which can influence the precision of the navigation system in different environment, calculate the groundwave field strength off seashore 400km on the frequency of 4.2MHz. In this paper, based on the definition of the GDOP of GPS, GDOP is also proved in theory by matrix theory, simulated the fig of the equal precision. In practice, GDOP can be used as a reference to locate the navigation stations, can also be used to analyze its performance. In this paper based on typical receiver tracking loop, code phase tracking error and carrier error are studies in theory, and the analysis has been validated by computer simulation.