Design And Implementation Of Weather Facsimile Receiver Base On RF Direct Sampling

The meteorological facsimile signals cover most sea of the world.Ships receive meteorological maps through meteorological facsimile receivers.In the ocean,they can receive information to timely predict typhoons,waves and other risk factors that threaten the safety of navigation,so that they can be planned or changed route of the ship on time.The meteorological information received by the meteorological fax machine is of great significance to the safety of the ship and the selectivity of the route.Most of the meteorological fax machines used at this stage are superheterodyne architectures.The processing of analog signals is complicated,the fault points are difficult to detect,and the digital integration is not high.Aiming at the advantages and disadvantages of the existing receiver structure,the paper proposes a design scheme of RF direct sampling meteorological fax receiver based on software radio idea.With this scheme,the RF signal is directly digitized after being sampled,eliminating the analog demodulation,simplifying the design of the RF front-end while reducing the volume,improving system integration,and reducing faults risk caused by analog signal processing.The RF direct-acquisition meteorological facsimile receiver is mainly composed of three parts: RF front-end module,A/D sampling and digital down-conversion module,system control and data processing module.The RF front-end module is composed of an antenna matching protection circuit,a band-pass filter circuit,a high-frequency amplification and an automatic gain control circuit and a frontend control circuit;the A/D sampling and digital down-conversion module is composed of an anti-aliasing filter and a signal processing circuit,analog-to-digital converter and FPGA;the system control and data processing module is based on the OMAPL138 dual-core processor;the system backplane provides the power circuit and the peripheral interface circuit for above modules.The approximate processing of the signal is as follows: the RF signal received by the antenna,through band-pass filter and signal amplified by the front module.After A/D sampling,the digital down-conversion process is performed in the FPGA,and the FPGA sends the data to the DSP core for differential detection demodulation processing,the DSP transfers data to the ARM core through the Share Region Memory,and the image data formed by the ARM core,finally uploaded to the host computer interface through the Ethernet for image display.This paper introduces the RF direct sampling meteorological facsimile receiver,compares the performance indicators with other types of receivers,explains the hardware design principle and software design idea,on this basis completes the detailed analysis and design of each module of the system,and finally debugging and analyzing the whole system to prove the correctness of the system design.