Research On The Video Information Leakage Based On The LED Display System

In recent years, with the continuous development of information and computer technology, the LED large screen has achieved wide attention and has been applied in more and more occasions because of its excellent display performance. But, the high working speed of the system, large driving pulse current, a very large number of wires, connectors, and high frequency switching power supply, display screen that can not be completely shielded, all these factors make the LED large screen display system a very serious electromagnetic radiation source. Inevitably there is a risk of video information leakage. Detecting and protecting the electromagnetic leakage form the LED large screen display system is a new research task that we are facing.Taking the LED display system based on FPGA control and Ethernet transmission as the research object, this paper analyzed the structure and working principle of the system. According to the research route, necessarily the whole system is divided into several modules and the potential video information leakage source of the system was initially positioned. After this, we carried out the functional characteristics, working principle, signal processing method and transmission way on the cable of those three modules, including LED video source, LED sending and receiving system, LED scanning and driving system. Then we built the signal model and simulated with Matlab to get the signal waveform in time domain and spectral features in frequency domain. Finally, we verified the correctness of the modeling method in combination with actual radiation test results, also judged out the key circuits that existed video information leakage problem.Transmission of electromagnetic energy has two ways: radiation coupling and conductive coupling. The analysis and conclusions before built the theory foundation for the research of inhibiting electromagnetic leakage. The host computer, sending controller, LED screen and other equipment can be the shielded with special materials to inhibit the radiation coupling according to engineering reinforcement scheme. The conductive coupling, among the power line, USB control line, and various video transmission lines, has a great influence on the judgment of information disclosurepositions, and may also become a new radiation source, to threaten the information security again. EMI filter is the most effective tool to suppression of the conductive coupling. This paper discussed the transmission network, key parameters and design method of the EMI filter in detail. F inally a EMI filter used for power supply was designed. Through simulating and testing, we made a comprehensive evaluation o f its performance, to demonstrate the feasibility and effectiveness of this suppression device, which has a good engineering application value.