High-speed Digital Demodulation, Symbol Synchronization Technology

With the rapid development of space communication, the amount of processing data leads to a dramatic rise accordingly. The requirement of real-time transfer data rate from the satellite to the ground is getting increasingly high, so the ground receiving system has to be developed with high speed digital processing technique. Nowadays, there is not a receiver whose data rate can be up to 600Mbps in Spaceflight Model. The research of high speed receiver is very important. Symbol timing recovery is one of the key techniques, which is focused in this paper.The symbol timing recovery is usually realized with the adoption of efficient algorithm and high speed processing. This paper starts out with the explanation that high demodulation should be implemented in all-digital system. Then a scheme using an improved interpolator based on Farrow structure and Gardner Timing error detection is proposed. In the feedback loop, a polynomial interpolator which is based on primary function is adopted. It can improve the performance of interpolation according to the actual requirements. Gardner algorithm as the timing error detection has been studied in detail. It is irrespective of carrier phase, and only needs two samples per symbol, which meets the need of high speed communication.In MF transmission model, QPSK signal is used as a sample. The simulation results show that the symbol timing recovery method is irrespective of carrier phase, and the performance of the improved interpolator is better than the cubic interpolator. With frequency offset and time error, simulation results prove that the method is effective.