Research On Synchronization And Diversity Combining Of Multi-channel Signals In DSSS

In data link communication,the reliability of information transmission is very important,and the link performance is also affected by factors such as Doppler shift and multipath interference.The purpose of this paper is to achieve dependable communication of data link through the synthesis of diversity technology.As a hidden diversity method,direct sequence spread spectrum is widely employed in data link communication because of its superior anti-jamming performance.In this thesis,a general multi-channel signal synchronization and diversity merging algorithm is proposed,and then the design of the multi-channel spread spectrum diversity receiver is completed combined with the single channel direct spread signal reception.In addition,in order to eliminate multipath interference,Rake receiving technology is introduced into spread spectrum diversity receiver to realize multi-domain diversity merging.The main contributions are illustrated as follows:1.With space diversity for multiple antennas,a multi-channel signal synchronization and diversity merging algorithm is proposed.In this algorithm,the limitation of diversity multiplicity is broken through by the design of parallel loop,and the phase detection algorithm based on cross-correlation is utilized to adjust channel signals for the same frequency and phase,without restriction of the type of signal modulation,which is universal.Several simulations of this algorithm have been provided which shows the maximum combined gain can be obtained for the N-channel signals is(10log₁₀N)dB.2.Considering the diversity of multi-channel signals in direct sequence spread spectrum communication system,a multi-channel spread spectrum diversity receiving system is designed.The simulation results indicate that the receiver can acquire the combined gain from both multi-channel signals and Spread spectrum signals,which further improves the signal-to-noise ratio of combined signal and the reliability of the link.3.Aiming to reduce multipath interference in data link communication,Rake receiving technology is studied intensively.Based on the fast approximated power iteration subspace tracking algorithm,it is applied to the spread spectrum diversity receiver,which can realize multi-domain diversity combination including time domain,space domain and frequency domain.The simulation results demonstrate that the spread spectrum diversity receiver combined with Rake receiving technology has good performance in multipath environment.4.The multi-channel spread spectrum signal synchronization and diversity merging algorithm is transplanted and verified through hardware system.A closed-loop test system composed of upper monitor,transmitting module and receiving module is designed.The working conditions of the receiver loop are tested systematically,and the effectiveness and feasibility of the algorithm are verified.