Reasons for Solution
As opposed to analog television coverage technology, digital TV coverage technology is a significant leap. The use of technology not only supplies user much better audio-visual service, but also greatly enhances operators transmission system bandwidth utilization, allowing operators to give user more channels choices through existing analog transmission system bandwidth. More importantly, the adoption of digital TV technology could enable operators to provide television programming in the basic services, and achieve more increment services such as user control, SMS TV, Web TV, e-magazines, TV shopping, EPG, TV games, video-on-demand etc. It will not only increase operators income, but also greatly enhances old user loyalty and potential users attraction, and further to ensure that operators increase the profit margin.
*City Mobile Digital TV is "the closest to people of media". Due to structural problems, it is unavoidable for weak and blind spots when operators finished construction. In the feebleness or zero signal areas, on-board digital mobile TV will be a mosaic or dropped suddenly and so on. Therefore, it is urgent to resolve these areas coverage problem in the most reasonable investment.
*The basic characteristics mountainous rural areas are living scattered. Radio, Film and Television fiber are not accessible in these remote areas, where are surrounded by mountains, its coverage has more difficulty. If we adopt the same way as city cable TV with fiber-optic network covering all areas, a county at least needs to invest about 20,000,000 yuan. And how to reduce the transportation cost in rural areas so that users can receive a good digital signal, which is one of the major challenges at present.
Solution Outline and Feature
*Construction of modern cities change with each passing day, resulting in more and more weak blind areas of digital mobile TV. But the areas are relatively small, according to coverage spots range and characteristics we can apply digital TV (same frequency, frequency difference , fiber, FSK) repeater to solve problems. It can be used to achieve the desired effect coverage and cost-effective.
*The basic characteristics mountainous rural areas are living scattered. Radio, Film and Television fiber are not accessible in these remote areas, where are surrounded by mountains, its coverage has more difficulty. If we adopt the same way as city cable TV with fiber-optic network covering all areas, the cost is too high. And the investment of wireless digital TV networks establishment is one-fourth of cable networks. Wireless is not only low cost but more television channels, and good picture quality, which has been welcomed by villagers.
Compared with Analog TV, Digital TV has the following advantages
*Good television rating, high-definition images, high-quality audio to meet people's sense demand
*Strong anti-jamming ability, less vulnerable to outside interference, avoid to cross channels, cross sound, noise and so on.
*Transmission efficiency, every analog TV channels could transmit dard definition 8-10 sets standard definition digital TV programs in existing channels.
*Compatible with existing analog television, normal tv can receive digital tv program with the installion digital TV set-top boxes.
*Mobile reception, the use of mobile terminals to receive digital tv program in anytime and anywhere.
*Provide new business, digital TV will achieve freely to play program and choose web information ,and supply many digital increment service with two-way networks.
Digital TV Application
From business range, we have three aspects as follows:
*Basic business: as long as gaining program source license, users can watch hundreds of digital TV programs, and dozens of sets of FM radio and digital audio broadcasting (DAB) programs.
*Expanded business: to offer Teletext, video conferencing, data broadcasting, TV encryption, video-on-demand etc.
*Increment services: With two-way interactive communication system, multi-purpose applications could offer more and more service, such as Internet access, Math remote, telemedicine, e-mail, computer networking, data communications, home security monitoring, and other multi-media information services.
From application object , digital TV scope has following aspects
*Digital TV village project. Digital TV possess some advantages, such as clear signal, stable, reliable, strong anti-interference, and digital transmission is easy to achieve high-security, high-quality scramble/descrambe, encryption/decryption, and information bradcasting, distance education, VOD video order programme and so on.
*Digital mobile TV in city and township building lifts. As a special equipment, lift is essential in people's lives and work. Being installed LCD TV systems in elevators, digital television technology would be applied to publicize system, display city visualize, release government information, and play public information like culture, health, traffic, weather etc.
*Cover blind spots in highways, tunnels, railway, and subway. To ensure that 2~4 sets programs could be transmitted, and watch TV show correctly in 120km / h. As network coverage might be affected by mountain, tunnel and low-lying road, relay station must be done network optimization.
Product Range
Frequency Repeater
Frequency repeater’s main principle is received signal by antennas in existing coverage fields that would been launched to pending coverage area after finishing to filter and expand. Main features: simple structure, signal forward delay time short. But the most important and urgent problem is frequency repeater isolation, the project construction has more difficulties.
Frequency Repeater Schematic
接收天线: receiving antennas；滤波器: filter；LNA: LNA；下变频、中频滤波、上变频: down-conversion, IF filtering, conversion；预失真功放:predistortion power amplifier
滤波器: filter；发射天线: antennas
Difference Frequency Repeater
Difference Frequency Repeate, that is, frequency shift repeater, with the similar principles to frequency repeater, but output signal frequency has been moved to the specified band. Main features: simple structure, signal forward delay time short, different frequencies send/receive signal ensure isolation to no self-excitation. Construction is easy.
Difference Frequency Repeater Schematic
接收天线: receiving antennas；滤波器: filter；LNA：LNA；下变至中频、中频滤波、上变频至指定频率: down-conversion to IF, IF filtering, conversion to specify frequency；预失真功放: predistortion power amplifier；滤波器: filter；发射天线: antennas
Fiber Repeater
Fiber Repeater firstly transform fiber-optic light signals into radio frequency signal, after amplification filter, and then launched into the region to be covered. Main features: As it is optical input signal, input signal-no-noise is high, more simple structure, no self-excitation, easy construction.
Fiber Repeater Schematic
光纤接口: fiber interface；光纤转射频: fiber switch RF；滤波器: filters；预失真宽带功放: predistortion broadband power amplifier ；滤波器: filters；发射天线: antennas
Digital TV Repeater
Digital TV repeater machine is metal sheet structure, size is 400mm × 600mm × 210mm. Door and box frame are used by metal structure. Cabinet bottoms adopt entire radiator, module rank single radiator inner surface. There are hinges to connect with door and cabinet to tighten lock. Door inside pasted rubber seal to achieve seal and water-resistant effect.
施主天线接口: donor antenna interface；射频监测口: RF monitoring port
重发天线接口: repeat antenna interface；本地监控RS232接口: local monitoring RS232 interface
远程监控天线接口: remote monitoring antenna port；防雷接地口: lightning protection port
电源接口: power interface
数字直放站通过安装附件与墙壁或安装杆连接: Digital TV repeater is connected with wall or installation pole by accessories equipment.
数字电视直放站的外形如上图所示: Digital TV repeater figure as pic
Centron Real Products Photos:
Success cases
Lian Xing village, Yongchun country
Lian Xing village owns complex terrain and scattered residence. MUDS digital project design case relied on Quanzhou city administrative region field intensity coverage. Front room by 64QAM modulation, fiber-optic links to the Optical counties with using frequency shift mode, output channel 700-760MHz, and then been launched by MUDS transmitting equipment, customers could receive signal through DVB-C set-top box, so can resolve AV signals to play by TV.
Transmitting equipment adopt high-quality broadband adjacent frequency transmission component system, allowing the system to ensure performance guidelins the program has many transmission sets, designed frequencies are 6.
Experiment System Schematic
光机输出信号: optical machine output signal；功分器: Power Splitter；变频器: Converter
合路器: Combiner；放大器: Amplifiers；发射机: Transmitter；板状天线: Plate antenna
用户机顶盒: Users set-top box；八木天线: Yagi antenna；用户接收端: users receiving end
