Research On Carrier Recovery Algorithm Based On National DTTB Standard

HDTV is recently one of the hot points in the broadcasting industry. It has gigantic market potential, and will influence the polity, economy, culture and life in a nation. Before Chinese DTTB standard came out, there has been three main standards of terrestrial broadcasting of digital television : ATSC(U.S.A), DVB-T(Europe) and ISDB-T(Japan). On August 30^th in 2006, Chinese DTTB standard GB20600-2006 was issued by the Standardization Administration of China(SAC), and was carried into execution on August 1^st in 2007. The issue and actualization of Chinese DTTB standard established the foundation for the development of Chinese terrestrial DTV, and started up Chinese DTV market.During the process of DTV receiver designing, synchronization is principal. It is the basic of other part's well-working, such as equalization and decoding. Carrier recovery is the chief component of synchronization, and also is the central part of this paper. Because of the imprecision of the local oscillator clock and the channel's fast decline, transmitted signal may depart from the central frequency, which will result in the frequecy offset of the baseband signal after down-converting. At the same time, during the process of transmission, the cable channel's time-variation and the down-converting circuit may arouse phase jitter. Both frequency offset and phase jitter need carrier recovery to compensate.In this paper, the author introduced the Chinese DTTB transmission system firstly. In succession, through theoretic analysis and simulation, this paper presented a new dual-pilot carrier recovery algorithm, which can be applied to the single-carrier mode in the national DTTB Standard and focused on illuminating the principle and structure of the new algorithm. This algorithm takes full advantage of dual-pilot under single-carrier mode, and utilizes a couple of independent FPLL to estimate frequency offset. Furthermore, this algorithm adopts weighted adding to resist pilot decline caused by multipath-interference. At the end of the paper, the algorithm was simulated under different channel condition such as AWGN, SSE and DSE, and was proved to have better performance than single-pilot carrier recovery algorithm in multipath channel.