Research On Key Technologies Of Spaceborne VDES Receiving System

In order to alleviate the load pressure of the Automatic Identification System(AIS),the International Maritime Organization proposed the concept of Very High Frequency(VHF)Data Exchange System(VDES).In VDES,Application Specific Message(ASM)and VHF Data Exchange(VDE)are added based on the Automatic Identification System(AIS),which can improve the performance of data transmission.This paper focuses on the demodulation technology of three subsystems and the collided signals separation algorithms with singlechannel and multi-channel satellite receiver.The main work of this paper is shown as follows:(1)Based on the analysis of technical standards on AIS,ASM and VDE subsystems,Viterbi differential demodulation method,baseband and intermediate frequency differential demodulation method and a demodulation method based on amplitude of constellation point are proposed to demodulate the AIS,ASM and VDE signals separately.Simulation results verify that the proposed methods have a good performance on bit error rate.(2)A multi-channel collided signals separation algorithm based on tensor decomposition is proposed,which is improved by stochastic proximal gradient algorithm.Tucker decomposition is utilized to compress the tensor and obtain kernel tensor,which can simplify the computational complexity.At the same time,the stochastic proximal gradient algorithm is introduced to speed up decomposition.Simulation results show that under well-posed and underdetermined conditions,the correlation coefficient between the source signals and the separated signals is greater than 90%,which indicates the proposed algorithm can achieve good separation performance for multi-channel collided signals.(3)Gray wolf optimized variational mode decomposition algorithm is proposed for singlechannel collided signals separation.The over-decomposition or under-decomposition may occurs when the classical variational mode decomposition(VMD)is used to separate the singlechannel collided signals because of the uncertainty of parameters.To solve this problem,the gray wolf optimization algorithm is utilized to determine the number of VMD initial signals and the penalty factor,which has better global search efficiency and faster convergence speed.Simulation proves that the algorithm has good separation performance for single-channel collision signals.(4)The overall design of the VDES satellite receiver is proposed.Detailed design process of the digital signal processing module is given and hardware implementation of the digital signal processing board is completed.The adaptability of Doppler shift of the receiver and the separation performance of collided signals are tested to verify the feasibility of the design.