Design Of Access System For Wireless Meteorological Facsimile Image

Facsimile image is transmitted by wireless meteorological facsimile station via wireless short-wave frequency, it becomes one of the chief means that ships accessing to meteorological information due to its wide coverage range.Meteorological facsimile cover almost maritime surface throughout the world, though facsimile receiver, ships can timely receive a great deal of useful maritime meteorological information, such as circumstance, weather forecast, warning and so on. It is great significance for guarantee the safety of sea sails; select the best sea route, etc.In this paper, a whole scheme of access system of wireless meteorological facsimile image is present for the insufficiency of current facsimile machine. The hardware and software scheme of access system of meteorological facsimile image are given on the basis of facsimile signal characteristics.Facsimile signal can be demodulated and facsimile image can be recognized though the system, and restored facsimile images are storged in PC,thus it is convenient for the management and utilization of maritime meteorological information.The proposed hardware module, which including analog signal acquisition, zero-crossing detecting data processing and upload these data into PC, is designed and implemented based on mixed-signal FPGA.The proposed software module, which is designed by Matlab simulation software, is divided into two parts. In the first part, frequency offset of facsimile signal is estimated by using the amendment Rife algorithm, then frequency is corrected according to the value of frequency offset. The detection of the remote control signal and phase synchronization signal, selection of speed can be accomplished in the second part of software module. Appropriate image processing scheme can be carried out according to different situation. Otherwise, the meteorological facsimile image is recorded as bitmaps with four gray-scales, the quality and visual effect of image is improved greatly. Finally, this whole system obtains the satisfactory result, and proves the program feasibility. Therefore, the scheme can establish basis for practical project application.