Method and apparatus for reducing radiant noise energy

摘要

An EMI suppression apparatus allowing a common mode radiant noise energy to be reduced without attenuating a normal mode signal level is disclosed. A communication LSI has an earth terminal connected to the housing via a common mode impedance. A Common mode choke composed of two coils having a mutual inductance is provided in the housing. One coil connects a signal terminal of the communication LSI to a signal transmission wire. The other coil connects the earth terminal of the communication LSI to the quasi-ground surface of the housing. The common mode chokes causes a common mode radiant noise generated by the common mode impedance to be removed from the signal transmission wire without affecting a normal mode signal flowing through the signal transmission wire.