The Realization Of The Chinese NAVTEX Receiver Based On DSP

NAVTEX (NAVIGATION TELEX) is an international automated direct-printing service for promulgation of navigational and meteorological warnings and urgent information to ship. It will fulfill an integral role in the GMDSS (Global Maritime Distress and Safety System) developed by the International Maritime Organization and is already contributing to safety at sea.The development of new technology accelerates the progress of communication. Along with the rapid growth of VLSI (Very Large Scale Integration) technology and computer technology, DSP (Digital Signal Processor) has been used widely in communications areas.In this paper, the Chinese NAVTEX receiver based on DSP are studied and implemented.Based on the performance requirement of the system, an analog-to-digital conversion circuit is adopted to sample the NAVTEX signal directly according as band-pass sampling theorem, and the samples are processed in DSP. Through a digital band-pass filter, the signal in low frequency is obtained and taken out. The whole process of demodulation and decoding is completed after the samples are timed and detected. A novel algorithm to detect the 2FSK (Frequency-Shift Keying) signal is adopted to make the signal receiving simple, that is the Fast Fourier Transform algorithm, and this is the innovation of the paper. At the same time, the paper simulates NAVTEX system's performances using Matlab to validate the feasibility of the algorithm. The design and debug of a DSP target board is finished all alone to implement the receiving of the NAVTEX signal.The study in this paper is adapted to the development and change of current maritime communication technology and provides some theoretic foundation for more develop of Chinese NAVTEX receiver by using the Soft Radio technology. It isprovided with definite practicality. The significance of the paper is that it adopts the advanced digital technology and digital circuit design to meet the needs about low power consumption, high integration and steady performance of the system. That is to accomplish the system performance with the hardware as more simple as possible.