The Resarch On Dttb’s Over-Sea Transmission

ITU promulgated three international DTV transmission standard, named by senior American TV system committee proposed ATSC digital TV standard, the European broadcasting union proposed DVB standards, Japan integrated services digital broadcasting organization of ISDB standard, our country has put forward in2007the national terrestrial digital TV transmission standard, which was started on August1,2007, in the nationwide implementation.All terrestrial digital transmission system standard use different Information source coding technology, error correction coding technology, the modulation and demodulation technology, be able to achieve the transmission of digital Terrestrial TV, But when the environment changes or climate is very bad, terrestrial digital TV transmission system will also get a certain influence, signals multipath fading caused by multipath transmission is one problem of in the terrestrial digital TV transmission should not be neglected specially In over-sea transmission conditions, due to the reflection of sea level, the changing of the tides, multipath fading especially obvious, terrestrial digital TV transmission system stability will be badly affected. How to overcome multipath fading and improve the terrestrial digital television transmission system to deal with all kinds of complicated environment ability, is the important links in present research.This paper first analyzes the radio transmission channel characteristics, and according to the characteristics of the radio waves transmission deduced the formula to multipath fading,And then introduced the terrestrial digital television transmission system channel coding technology, modem technology, and national standard of related technologies.In the end, this paper researched several technologies what could resistant multipath fading, including diversity technology, MIMO-OFDM technology, etc. Simulated the case in different number of transmitting antenna and receiving antenna and Alamouti space-time block coding (STBC). And researched the best height problem of receiving antenna in the cross-sea transmission consider sea level reflection and tidal variation.According to the Oriental pearl radio and television tower to ShengSi island television transmission system, used receiving diversity technology, low cost and verified through practice can effectively overcome the cross-sea transmission multipath fading.