Design And Realization Of Low Cost Digital IF Weather Facsimile Receiver

Because of its wide coverage and high broadcasting efficiency,wireless meteorological facsimile image broadcast by short-wave radio has become an important means for ships at sea to obtain real-time meteorological information.Weather map fax broadcasting almost covers all over the world ocean,Marine meteorological fax machine applied in the process of driving,can receive real-time regional meteorological department issued the waters of the weather,the meteorological forecast and warning useful Marine meteorological information,such as the sailing for the improvement of Marine navigation safety coefficient,choose the best route,etc all have important significance.Based on the shortcomings of the existing meteorological fax machine in hardware cost,receiver performance and digital integration,as well as the development and application trend of software radio in recent years and the actual application,this paper puts forward a low-cost IF digital meteorological fax receiver design scheme.Intermediate frequency signal after filtering amplifier and other processing,the use of ADC to intermediate frequency signal undersampling,collecting data through digital low-pass filter,digital frequency conversion and signal demodulation software after the data in the Shared buffer,using single-chip microcomputer to cache the data further processing,generate meteorological image upload first place machine,to implement low cost intermediate frequency digital weather facsimile receiver.It is divided into three modules through the system function design: RF front-end module,ADC sampling and digital processing module,and system control module.The RF front-end module is mainly used to filter and amplify the received shortwave signal after mixing it once,and then move the signal to the appropriate frequency band.ADC sampling and digital processing module can realize the functions of analog-digital conversion,digital orthogonal down-conversion and demodulation of IF signal.The main board of the system is designed based on the Cortex M7 core microprocessor minimum system circuit,storage expansion circuit and network communication,etc.The single chip microcomputer runs Free RTOS embedded operating system to realize the task control of the whole system,image data processing and storage and data command interaction with the upper computer.Paper focuses on the low cost of intermediate frequency digital weather facsimile receiver design principle,the key technology of each module,complete the procession of system hardware and software design of each module and function of each module is verified and the overall online debugging,this paper design the low cost of intermediate frequency digital weather facsimile receiver to meet the performance requirements,validate the correctness of the meteorological facsimile machine design scheme.