Measurement of radiated emission from PC computer system

The model of the radiated emission from a personal computer (PC) system is discussed by treating the components as electric dipoles and/or magnetic dipoles. The measurement results of the radiated emissions from each component or device of the PC system are introduced and discussed using the model. The measurement was carried out in an open site in which the background noise was also measured and compared with the radiated emission of the PC. The frequency range for the measurement spread from 20 MHz up to 200 MHz. Both periodic signal and random signal are measured. It is found that the main source of the radiation is the video channel including the video cable. the drive circuit in the VDU, and the CRT. The radiated level from these devices may reach as high as 40 dB above background noise. Other components such as the PCB, the disc drive, and the CPU may also produce radiation, but not as high as the video channel. It should be noted that the metal box may have some shielding effect on the component in the box