The Design And Practice On Digital Television In MMDS System

The broadcasting covering of country areas in China has been a weak sector of work in broadcasting enterprises for a long time. Only few analog TV channels are there in country areas and what more the covering range of the analog transmitters is smaller than that of digital transmitters which though with the same power, which result in that the covering site of broadcasting signals is always the urban areas while people who live in the remote areas receive no TV program signals, and as the essential parts of utilities for our party and governments to expressing its administration conception, broadcasting in suburban areas by far cannot give the government the ability to give publicity to the people effectively. The center government and local governments have attached much importance to the broadcasting covering project over country areas, and have put forward many new requirements for the construction of TV Broadcasting network over country areas in the new century. A scheme that to use digitalized CATV signals in some inner areas while to use microwaves in some areas for where with no probability using the cable network, which is an extraordinary perfect transition measure, efficiency, economy and a shortcut, before the digital television terrestrial broadcasting standards come into practice.The current status about the digital television in our nation and some other developed countries are introduced in this dissertation. And the basic theories such as sampling, quantization, coding techniques, techniques of co-running in multi-channels, conditional access, STB, techniques of microwave transferring about MMDS is also discussed. The basic technologic scheme on microwave transmission, currently maturate and advanced microwave transfer technology and equipment, efficiency slot gap antenna, character quality filter, mixer, exact crystalloid concussion apparatus, power backspacing technology, pre-distortion adjustment. Furthermore, the technologic schemes practicing using multilevel microwave transfer technology in some areas such as Lengshuijiang is introduced in the paper.The method that MMDS wireless digital television overcastting based on CATV standards is not only usable in terms of techniques and credible in quality, but also the industrious in investments, and the simple establishment, maneuverability of the method has been proved in practice, which will discussed in the paper in details. The operation results of Liling practicality is appropriating which works on the only CATV network operating platform. As the most important technique in the wholly digital-switching of HUNAN CATV, especially on the country overcast, MMDS wireless digitalized overcastting becomes an essential procedure in the way of the evolution of HUNAN CATV. MMDS will be a complementary and assistant mean of CATV to realize the broadcasting covering of the...