The Research And Realization Of Digital Communication System Based On VHF

Relying on this issue with Dalian Maritime university and Liaoning Fisheries Group cooperation projects "digital voice encryption technology in the maritime communications system applications (item number : 900522)." Now maritime communications systems primarily include satellite communications, single side band, VHF (VHF). VHF communication systems which have lower communication costs, equipment simple, wide bandwidth advantages etc, for a wide range of data communications applications in this system . This topic is based on this perspective, the use of more advanced digital communications technology for marine VHF data communications. Involving serial interface communication technologies, digital modems demodulate, correction of errors were wrong coding and modulation demodulate signals and VHF fired accept matching system. The main topic of the design and realization of a plug-in system design, achieved through VHF data signals long-range wireless communications system for data transmission. The major work completed as follows :1. Communications program design and realization1) In the design and realization of the DSP as the core system applications boards, including Flash, data memory and FPGA design, installation and debugging.2) using serial interface technology through RS-232 interface to realize the data communication between the PC machine and the application board card.3) With using the technology of GMSK to design and achieve the modem.4) Modem signals will be transferred through the VHF communications system has a second modulation, through VHF communication system access to data communications.2. PC machine interface programmingProviding a user interface programming using VC to achieve serial interface communications programming.3. Modem designDigital modulation and demodulation, coding and cutting-fault rectification by programmable chips CMB909 achieved. Modems used for the entire time series FPGA control, the use of DSP to CMB909 executable program control, data and images of the packaging and communications between PC machine and serial interface. 4. Modem and VHF communication systems matchingIn order to achieve data communications through VHF communications equipment, the interface circuits of a modem and VHF communication equipment were designed.In short, the DSP technology to achieve this VHF radio-based data communications systems, the design has certain real values of maritime communications.