| With the development of science technology, video transmission system has become a necessary and significant component in modern industry management because it has the characteristic of real time, accuracy, safety and convenience. Transmission capacity is developed from initial single video to multi-channel transmission in this system, at the same time; the mode of video transmission is changed from simulation to digital direction. Therefore, it is very important to study multi-channel digital video transmission system.This paper mainly introduces transmission system and provides new ways to solve specific problems for the equipment with transmission function. Basic thought for system design is that 8 video simulation signals are transformed into digital signals by Analog-to-Digital (A/D) converters and divided into two groups, then, transformed each of group with 4 video signals to 1 high speed signal, at last, the parallel digital signals were converted a serial signal and coupled to single fiber to send by making use of difference Alternating Current (AC) coupled. The sequential control circuit and data selectors were realized by a Complex Programmable Logic Device (CPLD) chip which is produced by Altera Corporation. Receiving is the converse of sending, reversion of video signal is carried out by photoelectric conversion, serial to parallel conversion, demultiplexing with splitter, Digital-to-analog (D/A) conversion and buffer circuit separately. Digital technology and CPLD technology are combined skillfully in the whole system, so as to transferring eight channels of video signal over a single optical fiber has been realized. At present, a few manufacturers have produced multi-channel digital video transmission system, so, how to complete the system by making use of simple thought and low cost method is an emphasis in this paper. This paper emphasizes on the design of hardware circuit and the argumentation of system scheme and, too. The technologies of signals' synchronous multiplexing, A/D conversion, D/A conversion, parallel-to-serial conversion, serial-to-parallel conversion, coding and decoding, phase-locked loop and optical fiber transmission are used in this solution.The uncompressed multi-channel digital video transmission system adopts structure modular design which enable device to work credibility and agility and automatically compatible with PAL, NTSC and SECAM video standards. Furthermore, all of its optical and electrical interfaces agree with the international standards. The experiments show that the system can work steadily and be suitable for working environment of remote monitoring and security guard system, and so on. |
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