Design Of Image Format Transformation And FSK Modulation Of Meteorological Facsimile System Based DSP

The meteorological facsimile broadcast covers almost the seas around the world.Most coastal countries have their own meteorological facsimile radio stations to transmit meteorological data to the seas near them regularly by the fixed frequencies.Ships at sea,especially ocean-going vessels,receive meteorological facsimile charts of the seas near them by meteorological facsimile receiving equipment.They can receive timely distribution of weather information such as typhoon warnings,weather forecasts and other useful marine meteorology messages released by local meteorological department,which are of great significance to the protection of maritime navigation safety,choosing the best route,etc.The main purpose of the research work of this thesis is to develop a FSK modulation scheme based on a DSP board for the "Information Transmission and Modulation System" of a "Shore-based Meteorological Facsimile Radio Transmission System Improvement Project".On the basis of analyzing deeply the mechanism of wireless meteorological facsimile broadcast,the paper puts forward a meteorological facsimile chart conversion and FSK modulation system based on a DSP,which is a part of the meteorological facsimile broadcast.The system gets the meteorological facsimile chart from the meteorological department,and converts the format of it.The gray levels information of pixels abstracted from the meteorological chart is modulated using FSK modulation and inserted synchronization signal through the timer and the interrupt of the timer in a DSP after being transmitted to the digital hardware circuit based on the TMS320VC5416 DSP.The code width of every signal the system outputting is precise,and the receiving device demodulates the image signal with the same code width.At the same time,the system inserts some synchronization signals with the accurate timing through the timer interrupt,such as the start signal,the phase signal,line synchronization signal and the end signal,so that the receiving device can get the correct meteorological facsimile chart.There is a comprehensive examination to the system designed in this thesis,and the testing result is satisfying.Not only does this system complete the FSK modulation of the image data,but also the code width of the outputting signal and the image signal is accurate and equal,,verifying the function of the system.