Research On AIS Signal IF Sampling And Processing Technology

AIS(Automatic Identification System)can be used to ensure the navigation of ships sailing on the sea by receiving and identifying their real-time information.It is a receiving and processing system integrated the computer technology,wireless communication technology,digital signal processing and so on.SAT-AIS(satellite-borne AIS)expands the signal coverage of AIS,making the supervision of a wide range,even of global ocean come true.However,the development of SAT-AIS is still in its initial stage nowadays in China.There still exist a lot of problems,such as Doppler frequency offset,signal collision,the low performance of signal etc.Therefore,the SAT-AIS receiver is of great significance for the researches.This paper starts from the introduction of the AIS system,referring the character,the modulation and the working frequency range of the AIS signal.It elaborates the design and implementation of an AIS receiver.The RF-passband sampling,the DDC processing,the decimation filter and the frame-head detection are also discussed later.Besides,this paper also studies the non-coherent demodulation of the AIS baseband-signal,and a better one is chosen between the two methods of signal non-coherent demodulation after comparison.Moreover,the frequency offset estimation,the symbol timing technology and the NRZI decoding are also discussed.The whole signal processing module and baseband-signal algorithm,as aforementioned,simulated and verified the feasibility of the AIS receiver.This paper accomplishes the AIS receiver,which is based on Artix-7 platform of the Xilinx and TMS320C6748 of the TI.In addition,the transmission of FPGA and DSP hardware interfaces are also achieved,such as EMIF and UART.Eventually,the function and performance of the whole system are tested to verify the feasibility and the instantaneity of the AIS receiver.And the result of the test can satisfy the requirement of the project.