AIS system demodulation method and demodulation system of ship vdes system

Abstract

The invention relates to an AIS system demodulation method and demodulation system for a ship VDES. According to the method, special signal detection, frequency offset estimation and frequency discrimination demodulation are adopted to achieve signal demodulation, the defect that the demodulation performance of traditional differential demodulation is poor is overcome, the method is applied to data demodulation under any conditions such as single / multiple time slots and short frame / long frame signals, the application range of data demodulation is greatly widened, signal detection is conductedby counting the adjacent code element sign bit change conditions according to the training sequence characteristics in a data frame structure, the method is simple in design and easy to achieve, and the signal detection result is accurate and has the high precision; by adopting frequency discrimination demodulation to achieve signal demodulation, the demodulation performance of the system is significantly improved; by means of a spectral analysis principle, the frequency difference between a local carrier signal and an AIS receiving signal is extracted from a carrier phase discrimination error, the carrier frequency of the AIS receiving signal can be quickly recovered, and not only is the capture cycle short, but also the accurate degree is high.

Description

technical field [0001] The present invention relates to the technical field of modulation and demodulation of ship data exchange system, in particular to a demodulation method and demodulation system of AIS system of ship VDES system. Data demodulation in case. Background technique [0002] In February 2014, Recommendation ITU-R M.1371-5 of the International Telecommunication Union proposed the technical characteristics of the automatic identification system (AIS) using time-division multiple access in the VHF maritime mobile frequency band, and made corresponding communication technical characteristics of the AIS system stipulations, but no corresponding stipulations are made on the implementation methods, especially the implementation methods under any circumstances such as single / multiple time slots, regular / burst signals, etc., are not clearly stated. [0003] In the existing AIS system communication system, the signal demodulation method adopts 1bit / 2bit differential d...

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Problems solved by technology

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art, and provides a demodulation method of the AIS system of a ship's VDES system, which uses special signal detection, frequency offset estimation and frequency discrimination demodulation to realize signal demodulation, overcomes the The defect of poor demodulation performance of traditional differential demodulation is suitable for data demodulation in any situation such as single / multiple time slots, short frame / long frame signals, etc., greatly broadening the scope of application of data demodulation

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