Abstract: Military communication equipments produce electromagnetic leakage during normal works. The signals can be restored into useful information by the enemy's intelligence system, which results in disclosure of confidential. It is a great threat to national information security. This paper designs a serial communication card against electromagnetic leakage by using the TEMPEST technology to start from the components, the filter circuit, wiring and printed circuit board, eliminating the root causes of a strong electromagnetic wave. In order to achieve that CPCI interface could communicate with the serial port directly, a new type of structure using FPGA as the core is introduced. An asynchronous FIFO is used for the cross-clock domain data buffer. The top-down design method is adopted to complete FPGA logic design. The experimental result shows that the design not only realizes the basic RS232 protocol and achieves optional of the baud rate, the data bits, the parity bit and the stop bit, but also meets the requirements of military electromagnetic radiation, prevents the leakage of electromagnetic, guarantees the information and communication security, and has been successfully used for the air test system.

Key words: electromagnetic leakage prevention, TEMPEST technology, information security, FPGA, RS232