Satellite-borne AIS signal differential detection method under frequency deviation compensation

Abstract

The invention discloses a satellite-borne AIS signal differential detection implementation method under frequency deviation compensation. The method comprises the following steps: according to intermediate frequency digital signals obtained through front-end processing of a satellite-borne AIS receiver, estimating Doppler frequency deviation of a received signal by utilizing a waveform matching method; on the basis of the estimated Doppler frequency deviation, enabling the intermediate frequency digital signals to pass through a delay differential detector under the frequency deviation compensation to conduct decoding, and realizing delay differential detection of AIS signals when the Doppler frequency deviation is larger. According to the method, the problem that under the condition that the Doppler frequency deviation of the satellite-borne AIS received signal is larger, the differential detection decoding is hard to realize is solved.

Description

(1) Technical field: [0001] The invention belongs to the field of ship automatic identification system (Automatic Identification System, AIS) communication technology, in particular to a space-borne AIS signal differential detection method under frequency offset compensation and its realization system. (two) background technology: [0002] In the process of decoding the GMSK carrier frequency signal using the 1bit delay differential detection algorithm and the 2bit delay differential detection algorithm, it is necessary to make the carrier frequency satisfy ω c T b =k 1 (2π) and 2ω c T b =k 2 (2π)(ω c is the angular frequency of the carrier frequency; T b is the duration of a single symbol; k 1 ,k 2 is an integer), if the carrier frequency cannot meet the above conditions, it will have a great impact on the decoding performance. The operating frequency of the spaceborne AIS system is two channels CH87B (161.875MHz) and CH88B (162.025MHz) in the VHF band, and the inf...

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Problems solved by technology

[0004] The purpose of the present invention is to solve the problem that although the performance of the existing differential detection algorithm has been improved, it has not considered the realization under a large frequency offset, so it cannot be directly applied to the satellite-borne AIS signal. The differential detection method of the on-board AIS signal, which can overcome the characteristics of the large Doppler frequency shift of the space-borne AIS received signal, and realize the differential detection of the space-borne AIS received signal with a large Doppler frequency offset

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