Study Of Tempest Technology In Computer Video Display Unit

This paper firstly discusses the actuality and trend of the electromagnetic information leakage and analyses the mechanism of the electromagnetic leakage in a computer video display units, and analyses information leakage of video signal in frequency quantificationally. Secondly the paper develops two new techniques that enable the software on a computer to control the electromagnetic radiation of CRT monitor transmits at very low cost: digital filter and dithering technique, validates the two methods to reduce the information leakage by a experiment. Aiming at the shortage of software process, This paper gives a new method which combines the software with hardware. Different from the traditional enclosure design project of TEMPEST computer, it adopts the idea of combination of hardware and software, and designs a real-time digital signal processing system with the CPLD chip as the core which includes visual sample module, algorithm process module and display module.Video signal process has speciality of high-speed, large-scale signal processing and complex time serial ,this digital signal processing system takes high-speed CPLD device as control unit of video sample and display output, management unit of data transferring and address, and process unit of FIR processing, this system use high-speed static SRAM as unit of data sample and transferring. Compared with software processing, this system has advantage of High-speed, accuracy and stability, fulfill the real-time request completely.