The Design And Realization Of Facsimile And NAVTEX Receiver Baced On The DSP

Facsimile and NAVTEX are important means to make ocean navigation safe and reliable, which got more and more attention of every country, with the rapid development of maritime industry. Nowdays, facsimile and NAVTEX information are received by facsimile receiver and NAVTEX receiver separately. Only a few manufactories work on the equipment which can receive facsimile information and NAVTEX information at the same time. It is not include our country. This thesis is to develop the kind of receiver which can receive facsimile information and NAVTEX information at the same time (New receiver).To develop the new receiver has many difficities: (1) To develop the receiving front-end. We need a receiving front-end to demodulate main carrier modulation signal which is available for both facsimile and NAVTEX. (2) The new receiver must have two kings of operation mode: Ethernet-operation by the mathed of which every operation are through ethernet and stand-alone-operation. This design makes it can link to other system, and work with them as a member. (3) Design the program which can process data of facsimile and NAVTEX received by receiving front-end based on DSP at the same time.The receiving front-end adopts a double superheterodyne method to demodulat the main carrier modulation signal. The base band modulation signal is sampled by oversampling techniques, and the data is send to DSP to be processed. The receiver's local oscillation circuit is designed based on DDS, which make the NAVTEX'receiving frequency changeable according to the user's need. During the design, single-chip computer is used with DSP to complete the control task. And make the Ethernet-operation and the stand-alone-operation realized more convenient. This thesis also analysed the mechanism of receiving facsimile information and NAVTEX information at the same time, and design the program based on DSP.The new receiver's PCB also designed, and the circuits are debugged successfully.