Feature Analysis Of The Influence Of Cross Sea Bridge On VHF Signal Propagation

A new era of maritime digital communication is opened up by the automatic identification system(AIS:Automatic Identification System)which is working in the VHF channel.The very high frequency data exchange system(VDES:Very High Frequency Data Exchange System)will push sea digital communications to another commanding point,which is in the stage of development.AIS and VDES are all working in the VHF(Very High frequency)band.In order to improve the reliability of VHF information transmission,the study of the propagation characteristics of VHF signals in a variety of environments has a certain innovation and positive practical significance.Based on this,this paper studies the characteristics of the influence of the cross sea bridge on the VHF signal propagation,which is helpful to the research and development of VDES system.Firstly,this paper designs and implements the VHF signal collection and analysis platform for the feature analysis of the influence of cross sea bridge on VHF signal propagation.The platform includes two parts:hardware system and software system.The hardware system is composed of signal generator,power amplifier,Yagi directional antenna,signal synchronization device and USRP(Universal Software Radio Peripheral).The signal synchronization device includes PRS10 rubidium oscillator and UM220 navigation/timing module.The software system mainly includes:Qt development platform based on Windows which is used for the configuration parameters of the signal generator and GNU Radio open-source development platform based on Linux system which is used for receiving data and storing data.Based on the above signal collection and analysis platform this paper designs three kinds of practical test system which are the test system for verifying the stability of the designed platform,the test system for verifying the directionality of antenna and the practical test system at sea.Among them,the first two test systems are the verification test system,which are the basis for the actual test over the sea.Based on the data collected from the practical test at sea,the MATLAB tool is used for the data processing and the theory of radio wave propagation loss is used for data analysis.The results of this paper give the relationship between the influence of the cross sea bridge on VHF signal and the relative location of the bridge to the mobile VHF signal receiver.The contents of this paper is a part of the project of National Natural Science Foundation of China "Research on new theory and key technology of ship wireless automatic positioning based on AIS communication system"(61231006).