Satellite-borne AIS signal demodulation method

Abstract

The invention provides a satellite-borne AIS (Automatic Identification System) signal demodulation method, which comprises the following steps of: performing band-pass sampling on an AIS intermediate frequency signal at a preset sampling rate through an AD (Analog to Digital) converter, and performing down-conversion and filtering extraction to obtain two paths of baseband sampling data of two frequency points; performing frame header detection on the baseband sampling data, and extracting a frame of complete AIS signal; performing frequency offset estimation and frequency offset compensation on the AIS signal through the code element information of the GMSK signal; aIS signal timing synchronization is completed on the signal sampling data subjected to frequency offset compensation; and carrying out matched filtering on the AIS baseband signal which finishes timing synchronization, sampling at an integer code element moment to obtain an output signal, and carrying out Viterbi decoding on the output signal to obtain an original code element information sequence. According to the method, the AIS signal can be demodulated, the number of operation times is small, the operation complexity is low, and the technical problem of signal demodulation of the AIS signal with the defects of low signal-to-noise ratio, large signal dynamic range and the like in the prior art is solved.

Description

technical field [0001] The invention relates to the technical field of radio communication, in particular to a method for demodulating a satellite-borne AIS signal applied to a signal receiver. Background technique [0002] In order to realize the supervision of ships in a large area and avoid safety accidents on ships, the AIS communication system has gradually been widely used. AIS communication systems mainly include shore-based systems and low-orbit satellite-based spaceborne AIS systems. Since shore-based systems cannot observe and track ships far away from land, the space-borne AIS system based on low-orbit satellites can realize the observation and tracking of ocean-going ships, which is the future development trend. [0003] The coverage of the space-borne AIS system can reach more than 1000km, and it can exchange navigation data between ships or between ships and base stations, so as to improve the navigation safety of ships and strengthen the monitoring of maritim...

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Problems solved by technology

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a satellite-borne AIS signal demodulation method, which can demodulate the AIS signal, with less calculation times and low calculation complexity, and solves the problems existing in the prior art for those with signal-to-noise Technical problems of signal demodulation of AIS signals with defects such as low ratio, serious co-channel interference, multi-signal mutual interference, and large signal dynamic range

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