Satellite-based AIS signal intercept and demodulation method

Abstract

The invention provides a satellite-based AIS signal intercept and demodulation method and aims to provide a demodulation method which can simplify configuration and complex degree of receiving equipment and can be adapted with large Doppler frequency shift and long signal time delay and realizes relatively low consumed resource amount. The method is realizes through the following steps of directly performing RF AD sampling after amplification filtering is performed on a signal which is received by an antenna; performing two-path digital channelization preprocessing on the AD sampling data in an FPGA, and outputting two paths of baseband IQ data; respectively calculating instantaneous phases of the two paths of baseband IQ data, and performing 1bit differential algorithm processing on the instantaneous phases for obtaining an instantaneous frequency; performing comparison decision on a buffered instantaneous frequency value f(n) with a frequency central value, and performing correlation operation on a decision result and a standard synchronous sequence; on the condition that a correlation operation value exceeds a threshold and reaches a highest value, determining demodulation bit synchronization and finding out an optimal sampling point for demodulation; detecting a signal end mark in the demodulation process, and outputting all demodulation results on the condition that the end mark occurs.

Description

technical field [0001] The invention relates to an AIS reconnaissance system for a space-borne ship automatic identification system, and a method for reconnaissance and demodulation of AIS signals based on a radio frequency direct acquisition scheme. More specifically, the present invention relates to an AIS signal processing flow and method in a spaceborne AIS reconnaissance system. Background technique [0002] The Automatic Identification System (AIS for short) is a new type of navigation aid system used between ships and base stations that integrates maritime ship identification, safety monitoring, communication and navigation functions. The space-borne AIS system has the characteristics of large Doppler frequency shift, fast channel time variation, and serious multi-user interference, and the complexity of coherent detection increases. The AIS system is mainly used to transmit AIS message information, mainly short message data transmission, and the number of operating ...

AI Technical Summary

Problems solved by technology

The receiving channel of this architecture is complex to implement, requiring frequency synthesizers and mixers, and it is expensive to implement on the spaceborne platform

In the signal demodulation, it mainly relies on the dedicated AIS signal demodulation processing chip, and the dedicated processing chip can only handle the frequency deviation of ±2.5kHz, which cannot meet the needs of AIS signal demodulation on the satellite platform; in addition, different manufacturers are producing AIS equipment The signal parameters and spectrum characteristics designed at the time will be different, and the difference in performance when using a dedicated processing chip to receive and process these signals will be unavoidable

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