An Analysis of the Application of Stellar Broadcom Common Cable "One Line" TV Surveillance Transmission-Innovation and Exploration of TV Surveillance Transmission

Abstract: The emergence of "one line" TV monitoring and transmission equipment with broadband common cable not only provides a high-quality and inexpensive solution for the bidirectional broadband synchronous transmission of multi-channel monitoring signals within the range of 1-5 km, but also completely changes the traditional monitoring spider web The star-shaped structure wiring method can make the forty-channel audio, video and control signals adopt the bus structure "one line through" transmission. This article discusses the characteristics and advantages of the transmission technology of broadband "one line" TV monitoring, and lists several typical application cases.

1 Overview

With the deepening of reform and opening up and the rapid development of the national economy, the city ’s floating population has increased significantly, which has brought many unstable factors to the society. The security situation is becoming increasingly serious. The incidence of criminal cases, especially burglary and robbery, has increased year by year. Relevant state departments have proposed comprehensive management of public security, and closed-circuit television monitoring has become an indispensable system in security.

The application of CCTV monitoring is getting wider and wider, and many new technologies are constantly being applied to the monitoring field. In terms of transmission, the use of optical fibers and optical transceivers not only makes long-distance monitoring possible, but also makes the transmission quality of monitoring images and monitoring signals qualitatively improved. In the monitoring transmission of tens of kilometers to hundreds of kilometers, optical transmission is the best choice for transmission. However, in monitoring applications below 1-5km, considering the cost of the system, most of the occasions have to use the traditional coaxial video cable transmission method, because the optical fiber and optical transceiver are not economical for the close-range monitoring system. However, because the coaxial cable greatly attenuates the video signal, if the transmission distance exceeds two or three hundred meters, the image quality will be significantly distorted and attenuated. Even if the video amplifier is added, the transmission distance is difficult to increase significantly, and the image quality is difficult to end. Expectedly, the construction cost has also increased significantly. Therefore, the transmission of images and signals around 1-5 kilometers has become a major bottleneck in the field of surveillance applications. Is there no good and cheap solution? A new technology has emerged, which will solve this problem that plagues people. This is the transmission technology of "one-line communication" monitoring of broadband common cables. The emergence and application of this new transmission technology is a major change to the wiring method of TV monitoring, and the monitoring transmission method has achieved a leap in programming.

2. Several monitoring image transmission methods

Before the emergence of the "one-line" TV surveillance transmission technology with broadband common cables, traditional video cables and optical fibers were mainly used to transmit TV surveillance image signals.

Video coaxial cable is the earliest used and the longest used transmission method. When the video signal is transmitted in the coaxial cable, not only the overall amplitude of the signal is attenuated, but also the frequency components and the video amplitude attenuation are very different, especially the color saturation part is the most attenuated. Therefore, traditional video cables are only suitable for transmitting image signals at close range, generally around 200-300 meters. Although the transmission distance can be extended by adding a video amplifier, there are also difficulties in project opening / debugging / maintenance, as well as unsatisfactory image quality and limited distance. In addition, if there are other control signals while transmitting the image signal, additional wiring needs to be added, resulting in increased engineering costs and difficulty in construction. At the same time, the transmission resistance of traditional video cables is extremely poor. For example, in places with strong interference sources in power plants and large factory workshops, this is also the fatal weakness of video coaxial cables. The transmission distance and interference problems are extremely limited. Its scope and development.

Optical fiber and optical transceivers are the best choice for distance monitoring systems above the kilometer level, and the transmission distance of coaxial cables is limited. In this way, people always face a dilemma for the distance range of 300m to 5km: the use of coaxial cables and video amplifiers has no effect Good, the amount of cable is large and the cost is not low, and the use of optical fiber is uneconomical. Nowadays, the emergence of broadband "one line" TV monitoring transmission equipment solves this problem, and it will become an inevitable choice for monitoring transmission of several kilometers to tens of kilometers.

3. Transmission advantages of broadband common cable one-line communication monitoring

The reason why broadband one-wire "one-line" TV monitoring has become an inevitable choice is because it has many advantages such as strong anti-interference ability, long transmission distance, easy wiring, and low price. The transmission equipment adopting the "one-line communication" monitoring of wide-band common cable can transmit multi-channel monitoring signals to several kilometers or even further, and the quality of the transmitted image can be comparable to that of the optical transceiver, and the image quality can reach more than level 4, which is not difficult to see. In the monitoring system, the use of broadband common cable "one line" monitoring for transmission has obvious advantages:

1) Long transmission distance and high transmission quality. Because of the advanced processing of intermediate frequency processing and up-conversion technology in broadband modems, it excellently compensates for the attenuation of the high-frequency coaxial cable to the amplitude of the video signal and the attenuation difference between different frequencies. The brightness and color of the original image and the real-time performance are maintained. When the transmission distance reaches several kilometers or more, the image signal is basically free of distortion. If the relay high-frequency amplification method or the combination of fiber + cable is used, the transmission distance will reach tens of kilometers.

2) Simple wiring and high cable utilization. "One" coaxial cable can transmit more than 40 lines of monitoring signals and downlink control signals. The wiring combination is eclectic, and multiple structures such as bus, tree, and star can be used to integrate multi-point images and control into one cable bus for bidirectional transmission. The broadband common cable "one line through" TV monitoring and transmission system makes full use of the cable resource space, which greatly simplifies the wiring structure and greatly reduces the wiring costs and construction costs. With this system, you can experience the convenience brought by the use of eight lines of transmission from two hundred monitoring points, and the maintenance volume and cost are also suddenly reduced.

3) Strong anti-interference, applicable to a wide range of carrier high-frequency transmission methods can effectively suppress common mode interference and electromagnetic interference, even in the harsh electromagnetic environment of power plants, coal mines, etc. can ensure image quality.

4) Mature technology and high stability ST-6000 broadband common cable "one-line communication" TV monitoring and transmission system is based on the development of cable TV technology. The application of cable TV technology in China has a history of 20 to 30 years. Reliability is obvious to all.

5) Data modulation and two-way transmission The control signal adopts FSK data modulation technology, which is transmitted in the same cable with the camera's return video signal in two directions. The control signal adopts intermediate frequency modulation to be stable and reliable.

6) Simple expansion and smooth upgrade The structure of the bus topology does not require a separate wiring, and the local bus is added.

7) Powerful function and good expansibility. It is fully compatible with monitoring, alarming and broadcasting. The multi-functional two-way transmission platform realizes program leap in monitoring transmission mode.

4. Engineering application

It is very flexible and convenient to use broadband common cable "one-line communication" equipment in the monitoring project. The following figure is a schematic diagram of transmission:

The front-end camera is connected to a broadband common cable modulator, and the control center is connected to a video demodulator to transmit a 1-channel image several kilometers away. Multiple common cable modulators can also be used to transmit multi-point monitoring signals at a distance.

The following are two engineering application examples.

Project example one:

In an international logistics group in Shandong, it is necessary to realize the dispatching and command of multiple warehouses within a 2.5km radius of the entire logistics group in the monitoring center. A universal gimbal is installed in front of each warehouse. The power supply signal needs to be provided from the central monitoring room. In the original scheme design, video cables were used for image transmission, and video amplifiers were used to compensate for the video attenuation. Control cables were laid to transmit control signals. During the construction, it was found that the chroma, brightness and saturation of the monitored image could not be nested synchronously after remote transmission, causing image distortion. The addition of cable noise and nearby electromagnetic interference caused the image to have extremely bright noise and texture, which could not meet the requirements of the monitored image. . After careful consideration and deliberation of the implementation plan, the broadband transmission cable "one-line communication" monitoring and transmission equipment was finally selected to transform the transmission of image signals and control signals without changing the original lines. Since the high-frequency transmission only attenuates the carrier signal, the image chroma, brightness and saturation are synchronously nested and the loss is very small. The returned image fully reaches level 4 and the image is clear; the use of high-frequency transmission has strong anti-interference ability, and the image has no Noise and texture. The system diagram is as follows:

Engineering example two:

During the engineering design, the closed-circuit monitoring system of a coal mine in Shaanxi Province all used coaxial cables to transmit image signals. When the project reached the end, it was found that many images from the camera points were interfered by coal mining equipment, and the images were gray and connected to the network. Interference, the project could not pass the acceptance for more than a year after the project was completed. Later, all the points with interference in the image were transformed with our company's broadband common cable transmission equipment, which effectively solved the interference problem, and the image was clear and stable, and was recognized by the user. This engineering application further shows the super anti-jamming performance of the broadband common cable transmission equipment.

5. Conclusion

The application of the broadband common cable "one-line communication" TV monitoring system in the monitoring field not only effectively solves the problem of high-quality image transmission in short and medium distances, but also simplifies the wiring structure, saves the engineering cost and time, and brings a great deal to the engineering company. convenient. The use of broadband "one line" monitoring transmission equipment has completely changed the traditional wiring method and provided a powerful solution for the monitoring project.

Beijing Hengxing Ketong Wang Zhijun 010-82566461