Design and implementation of intermediate frequency (IF) downconversion and direct radio frequency (RF) sampling in AIS receivers
Guohao Chen, D. Yu, Na Wu, Zhaolei Yu, Wen Zheng Gao · 2025
This paper presents a practical approach for processing AIS signals after RF direct acquisition in the ship automatic identification system. The method involves shifting the signals of the two AIS frequencies to baseband using two stages of digital downconversion (DDC). A multi-stage decimation filtering design is then employed to isolate the low-rate AIS signals of both channels. The implementation is carried out on the FPGA-JFM7K325T from Fudan Micro Company, followed by extensive repeated testing. The results demonstrate that the multi-stage filter extraction method effectively reduces hardware resource consumption and meets the design requirements, confirming the viability of this approach for enhancing AIS signal processing efficiency.