Research And Implementation Of Key Technologies For Link16 Data Link Modulation And Demodulatio

The Link16 data link is the preferred one by the U.S.army in Network-centric Warfare Theory.It combines the advantages of previous data links,achieves the interconnection and intercommunication of the armed services,enhances the cooperative engagement capability,and improves communication capacity,anti-interference,confidentiality and other performance.Based on the current research on the Link16 data link,this study has done the following work around its signal transmission technology:First,this paper studies the characteristics of the Link16 system and analyzes its TDMA network structure,message format and transmission waveform processing flow.Emphasis is placed on the functions and characteristics of each module in the signal waveform generation process.Secondly,the key technology of physical layer transmission is simulated and modeled,mainly including MSK modulation and demodulation,time synchronization,CCSK spread spectrum.Considering the flexibility and complexity of engineering realization,the digital modulation scheme of generating MSK signal by DDS technology is determined.By studying coherent demodulation,multi-symbol detection and one-bit differential demodulation performances,one-bit differential demodulation scheme which is not sensitive to frequency offset and timing errors is determined on the basis of the characteristics of Link16 signal burst transmission.Through the simulation and comparison between cross-correlation and differential correlation synchronization schemes,combined with the characteristics of synchronous pulse transmission at equal intervals,a synchronization scheme based on the combination of cross-correlation and peak counting is proposed.Finally,the correction performance of CCSK spreading sequence is studied.Several new CCSK spreading sequences are found by searching,and the new spreading sequence can correct one more code chip error.Then,the xc7z100ffg900 chip of the ZYNQ series is used to realize the system physical layer transmission technology.First,the implementation platform of this project is briefly described,and then the functions and implementation of each module of the transmitter and receiver are discussed in detail.The CCSK spreading scheme is improved: only one chip sequence needs to be stored locally,and the storage resource usage is reduced by one time.In the meantime,a CCSK despreading scheme based on FIR filter is proposed,which has low complexity and high stability.Last,the performance test of Link16 data link system is completed.The communication function of the Link16 data link is tested under the direct wired test environment,and the test results are compared with the simulation results.The test mainly includes the system bit error rate,packet error rate and anti-frequency offset performance.