The world’s countries are vigorously developing the ground Digital TV Broadcasting (DTTB), terrestrial digital TV broadcasting using advanced terrestrial digital TV transmission technology, has the following features: large capacity information transmission. 8MHz channel can be transmitted in a more than 20Mbps of data, some of the largest payload modulation rate up to 33Mbps, to meet the transport of a HDTV and SDTV sets of requirements; has good resistance against multi-path and Doppler frequency shift features, in various environments strong anti-interference. Terrestrial digital TV transmission technology commonly used by the most advanced error correction and signal modulation techniques to enable the receiver to a variety of conditions and environments reliable received signal, to anti-static multi-path (receiver at-intensive buildings environment, only a simple antenna can be used to meet the normal reception) and dynamic multi-path interference (sports environment suitable to receive, in the case of speed up to 150KM per hour, can be stable to receive), and resistant to various home appliances pulse interference . The feature not only for fixed receivers and also applies to portable receivers, people traveling by car and train through the mobile phone, PMP (portable multimedia players), PDA (personal digital assistants) and laptop computers and other receiving terminal access to reliable, real-time multimedia information services; In addition, television frequencies is rich in resources, quality, determine the terrestrial digital TV transmission technology has a good application market and development space. Terrestrial digital television broadcasting agreements: DVB-T, DVB-H , DAB, ISDB-T and domestic made DMB-T/ADTB-T/TiMi, following me in the terrestrial digital TV transmission technology in the field of application of live television on your point of view.

Terrestrial digital TV transmission technology currently on live TV application mainly in Microwave Cameras and digital microwave transmission, the following I highlight the current domestic television news use more mobile broadcast trucks microwave transmission system.

A technical description of microwave systems

1. Using the standard Domestic television news mobile broadcast trucks used in the microwave transmission technology are based on the existing terrestrial digital TV transmission technology, but use a different standard. Some companies adopt the European DVB-T standard, some companies use the GB20600-2006 “digital terrestrial television broadcasting transmission system frame structure, channel coding and modulation” in the single-carrier modulation techniques, as well as the company used is GB20600-2006 “digital terrestrial television broadcasting transmission system frame structure, channel coding and modulation” of multi-carrier modulation technique, other manufacturers basically use similar modulation techniques. Terrestrial digital TV using modern technology to produce digital microwave interference performance with strong support for the advantages of fast-moving receivers, overcome all kinds of multipath interference, you can send and receive side of the non-realization of sight transmission.

2. News mobile broadcast trucks used by radio frequency

Car microwave frequency range from 300MHz to 10GHz, the frequency is too low, although the diffraction ability, but susceptible to interference, in big cities is hard to find available frequencies; frequency is too high, although the frequency of easy to find, but electromagnetic wave transmission capacity decreased significantly, in a sheltered environment, does not travel very far, so the best choice of available frequency range and low frequency. Because different parts of the electromagnetic environment, before first use Test Good use of local frequency, and then matching its corresponding transmitter, the transmitter output bandwidth is typically 8MHz, 300MHz tuning range of generally about some aspects of factory equipment in the frequency adjustment step can be adjusted in units of 1MHz; Some aspects of factory equipment in the frequency adjustment step is adjusted in units of 8MHz, 1MHz tunable device can better overcome a similar frequency interference from outside in order to fully use the precious frequency resources. As far, in the 80MHz bandwidth of the antenna around, so much change in the frequency range is meaningless, unless a few more with different frequency antennas vice. In the frequency of use, the city departments to use a lot of radio frequency, frequency range occupied by wide band in the traditional TV channels can be used hard to find, about the current domestic use 1.2GHZ frequencies for mobile broadcast television stations in more vehicles.

weihua -
About the Author:

I am batik wall hanging , wooden switch plates.