The Design And Implementation Of DCB-S2Receiver Carrier Synchronization Algorithm

DVB-S2satellite digital television signal will be added carrier frequency offset and phaseoffset when it transmits, and the carrier synchronization module in the receiver is used toeliminate the influence of these offset, and make the receiver demodulates the signal correctly.So, the carrier synchronization is very important in the receiver. In nowadays, manyresearches of carrier synchronization for DVB-S2system are based on the system works inthe pilot mode. But, DVB-S2system has a lot of work modes, and it is not every mode haspilot signal. The purpose on this paper is carry out a carrier synchronization algorithm schemecan compatible all kinds of DVB-S2system’s work modes.Nowadays, carrier synchronization used has two steps: frequency synchronization andphase synchronization. The frequency synchronization is to eliminate the large carrierfrequency offset, and the phase synchronization is to eliminate the carrier phase offset and theresidual carrier frequency offset. Because the carrier frequency offset is large, so thefrequency synchronization has two steps: coarse synchronization and fine synchronization.Zarlink had put forward “Blind sweep” for channel scan and parameters extraction.The main works in this paper are the following mention. Research on DVB-S2system’sstructure and every part’s function, and analyze the influence of the channel. Then carry outthe carrier synchronization scheme for DVB-S2system based on DVB-S2system’s problems,like large frequency offset, low SNR, many work modes. The carrier synchronization schemeis “Blind sweep+frequency synchronization+phase synchronization”. Because of the signalhas large carrier frequency offset, before the timing synchronization module the scheme willuse “Blind sweep” to estimate channel’s parameter. In the broadcast mode, the scheme willuse data aid algorithm to do frequency synchronization and choose the SOF data in frameheader as aid data. Then, it will use the polarity decision algorithm combine with Q-th powerclose-loop to do phase synchronization. In the interaction mode, the frequencysynchronization algorithm can use the pilot data and SOF data as aid data, and use thepilot-aided linear interpolation combine with Q-th power close-loop to do phasesynchronization.At last, the paper will use C program to built DVB-S2system platform to do thealgorithm simulation in all kinds of modulation modes and all kinds of SNR. In simulation, get the lowest SNR point which system can work correctly to show system’s characteristic.And the result of the performance of the system is close to requirements in the standard ofDVB-S2, and higher0.1~0.5dB then the standard require, so the carrier synchronizationscheme can work in DVB-S2system.