Fractionally Spaced Equalizer Research Of National ADTB-T Receiving System

Digital Television Terrestrial Broadcasting (DTTB) is one of hotspots researched by universities and enterprises around the world recently. DTTB basically represents the developing precursor of broad band digital communication. Its potential of product value arouses the most care among the industry. At present, there are three DTTB standards: (1)ATSC standard, which adopts 8VSB modulation.(2) DVB-T sdandard,which adopts OFDM technology.(3)ISDB-T standard,which adopts BST-OFDM tehchnology. National DTTB standard, composed of single carrier ADTB-T standard and multi carrier DMBT standard has been released in 2006. Research on terrestrial transmission technique according to digital television standard of our country has far-reaching meaning.DTTB has the stumbling block of serious signal fading, which is caused by high multi-path pervasion in wireless broadcasting channel. Especially, it is more difficult to recovery signals in moving receiver environment, due to the fast time variable characteristic of the channel. So towards Dibital Television Terrestrial Broadcasting receiving system, how to deal with Inter-symbol Interference is a keystone and difficulty. For single carrier system, we always adopt timing equalizer to eliminate Inter-symbol Interference. A low complexity fractionally spaced equalizer is presented based on National DTTB Standard ADTB-T in this paper. At the beginning of this paper, National DTTB standard is introduced, and receiving system structure of National DTTB standard is given. Then paper discusses wireless channel model of DTTB system, and analyses equalizer theory in several aspaces, such as: equalization basic principium, structure sort of equalizer and self-adaptive algorithm of equalizer. At last, this paper discusses the design project of equalizer adopted in ADTB-T receiving system: a fractional spaced decision feedback equalizer structure is adopted to minish sensitivity of equalizer to time error. For algorithm of equalizer, a CMA+LMS omnibus algorithm with effective switching control make the equalizer have high convergent speed and well basic performance, at the same time, in order to optimize performance of equalizer, a series algorithm such as: Low complexity algorithm, step size control algorithm, Mitigating Error Propagation algorithm and so on, is presented this paper.According to the simulation results based on ADTB-T platform, this design has well performance towards not only for static channels but also for dymatic channels, and makes the performance damand of national ADTB-T standard's receiving system.