Cable TV system

The cable television system was initially established as a functional antenna system to address the viewing issues in remote areas or in urban areas where high-rise buildings obstructed the viewing experience. The real CATV appeared in the United States in the late 1950s. People used satellite, wireless, self-made and other program sources to transmit high-definition, multiple sets of TV through one-way radio lines. After entering the 1990s, the construction of Cable TV in China developed like mushrooms after rain. Based on the principle of clearer and more comprehensive transmission, the network is gradually upgrading from 300MHz adjacent frequency transmission, and high bandwidth and fiber optic cable are the foundation of urban Cable TV construction. HFC (Fiber Optic/Coaxial Cable Hybrid Network) network has begun to take shape nationwide. After 5-6 years of rapid development, the temperature of Cable TV has gradually cooled down. Where to add value and how to tap into the huge potential of the network have become the first problems that Cable TV needs to solve. People gradually realize that although the initial service of cable television networks was to provide high-quality, multi channel television services, and one-way broadcasting technology was also used during network construction, the business scalability of HFC is quite significant. The bandwidth for transmitting digital data integrated services on HFC networks can reach 1GHz. In addition to transmitting analog videos, there are also many bandwidth resources reserved for digital video transmission and bidirectional data communication. The use of HFC networks can better support Internet access, etc. So, connecting to the Internet through the Cable TV network was put on the agenda.

1.1.1Characteristics and advantages of the system

(1) There are many viewing programs and good image quality. In the cable television system, local television stations can broadcast television programs through open circuits, including programs from VHF and UHF channels. Cable TV uses high-quality signal sources to ensure a high level of signal quality, as it is transmitted through cables or baskets, avoiding issues such as ghosting and spatial clutter interference caused by open circuit transmission.

(2) The cable TV system can watch programs from Chinese and foreign C-band and Ku band TV channels transmitted on satellites.

(3) The cable television system can watch closed-circuit television transmitted by local cable television stations (or corporate cable television stations). CCTV can play excellent movies and TV shows, as well as self-produced TV programs.

(4) The cable TV system has a long transmission distance and a wide range of TV programs, which can well meet the requirements of users who are interested in watching TV. After adopting advanced neighboring frequency front-end and digital compression technologies, the number of channels can be greatly increased.

(5) According to the experience of many local cable TV stations and corporate cable TV stations, cable TV stations are not only more cost-effective than direct individual viewing, but also can greatly enrich program content. For a city, there will no longer be a large number of scattered Yagi antenna groups, but a centralized antenna array, making the city more beautiful.

(6) With the continuous development of technology and the continuous improvement of people's living standards, cable television can also further develop. For example, the number of television channels can continue to increase, self-produced programs can also continue to increase, and it can also develop two-way transmission function, using multimedia technology to integrate image, language, digital, computer technology into a whole for information exchange. The bidirectional system has already been put into practical use abroad, and its main functions include the following aspects:

1) Security, home shopping, electronic payment, medical care.

2) Pay TV programs can broadcast the latest movies and other content. Users can rent a channel on a monthly basis or pay based on the number of times they rent it. They can also watch the desired programs on demand. Paid users are equipped with decryptors, while unpaid users cannot watch.

3) Users can connect to the computing center for data signals and achieve computer communication.

4) Exchange television programs.

5) Monitoring the working status of the system.

1.1.2Composition of the system

The cable television system mainly consists of signal sources, front-end, trunk transmission, and user distribution networks. The main task of the signal source receiver is to provide various signals that the system intends to transmit to the front-end. It generally includes open circuit television reception signal, FM radio, ground satellite, microwave and cable television self-produced programs and other signals. The main task of the front-end part of the system is to filter, convert, amplify, modulate, and mix various signals sent by the signal source, making them suitable for transmission in the mainline transmission system.

1.1.1.1Simulated Cable TV System Diagram