Research And Implementation Of Direct RF Sampling AIS Signal Receiving And Processing Technology

Automatic Identification System(AIS)is an automatic continuous broadcast system working on the Very High Frequency(VHF)band and designed for ship-to–ship and ship-to-shore communications.SAT-AIS which is developed from AIS has greatly enlarged the monitored range of maritime vessels.Therefore,the research on SAT-AIS demodulation technique is of great significance.The main contents of this thesis include the following aspects.(1)Basic information of AIS signal,overall structure of AIS receiver are introduced and the RF sampling of AIS signal by A/D is designed and implemented.(2)The FPGA chip of Xilinx kintex-7 series is used to design and implement the digital down conversion,decimation filtering and preamble detection.The selection process of design scheme and hardware realization are described in detail.(3)The demodulation algorithm is designed and implemented based on the multi-core DSP.The frequency offset estimation,symbol synchronization,non-coherent demodulation,Signal Noise Ratio(SNR)estimation,and error correction are simulated and evaluated.The DSP implementation of various algorithms and the dual-slot AIS long message demodulation is investigated as well.(4)Finally,this thesis describes the environment and instruments needed for the test on AIS receiver.The test results of sensitivity,dynamic range,frequency offset adaptability,algorithm sensitivity and anti co-channel interference performance are presented.The sensitivity of AIS receiver is about-118d Bm,and the dynamic range is approximately 40d B.For E_b/N₀=12d B,with certain frequency offset,transmission delay,and co-channel interference,the correct reception probability of AIS frames is over90%.The test shows that the AIS system is good and can meet the project requirements.