Research On Carrier Recovery And Timing Synchronization For High Speed Data Transmission

The commercialization of small satellites has boosted satellite data service industry.The downlink data volume has been in increasement as the resolution of satellite load continuously improved.Meanwhile,the rise of software-defined satellites also raised higher requirements for the uplink data capability of small satellites.While the total amount of small satellite data transmission increases,the transit time is limited.Therefore,higher speed data transmission is needed to meet the market demand.Firstly,the digital modulation and demodulation methods are introduced.Considering the feature of small satellite,which has small size and limited power consumption,as well as the characteristic of satellite communication channel,QPSK is selected as the satellite-used modulation method and the latter research is based on this.For carrier recovery,the principle of the common carrier recovery algorithms are introduced.Based on the analysis each algorithm's merits and demerits as well as the respective applicable scene,the hard-decision Costas loop method is determined to be applied for high-speed data transmission.And then the selected algorithm is simulated on MATLAB.The result shows that the designed carrier recovery loop can complete the frequency error and phase error recovery and tracking of high-speed data.For timing synchronization,Gardner algorithm is analyzed in detail.Each part of Gardner loop is discussed in principle and the idea of proper simplification of loop filter and interpolation filter is proposed for high-speed circumstance.Specifically,the influence of loop filter order and interpolation method on timing synchronization performance are analyzed by simulation.Moreover,on the basis of verifying the carrier independence of Gardner algorithm,the joint simulation of carrier recovery and timing synchronization loop is carried out.The BER performance of the whole system is tested and compared with the theoretical BER.According to the result,the designed loop has good demodulation performance,providing theoretical support for futther practical experiments.Finally,a broadband data transreceiver experiment platform based on Software Define Radio is established to verify the algorithm proposed before.The results show that the carrier recovery and timing synchronization algorithms in high-speed transmission studied in this paper have good performance and practical feasibility.