Since the occupation density of microwave frequency band is highly increased, the electromagnetic environment is getting worse seriously. It is sometimes reported that electronic machines are not normally operated because of the influence of undesired electromagnetic wave. It often gives fatal blow to even human life and thus becomes serious social problems. Some international organizations such as IEC, FCC, CISPR, VCCI, VDE, ANSI, etc., have enacted laws and regulations related to the protection against EMI (Electromagnetic Interference) and EMS (Electromagnetic Susceptibility), are farther strengthening the regulations.
To meet these tendency, in this thesis, a kind of electromagnetic compatibility (EMC) problems was solved by developing a broad-band EMC filter. As a solution, an EMC filter has been designed which is composed of feed-through capacitors and ferrite beads with high permeability. The proposed EMC filter satisfied the EMC requirements for a wide-band noise signal from 10 MHz to 1.5 GHz in power supply line. The optimum values of the ferrite bead structure and capacitance of the feed-through capacitors was found by calculating the load effect of ferrite beads and the filtering performances.
As a result, the filter showed excellent differential- and common-mode noises filtering characteristics above with 28 to 70 dB in the frequency band from 10 MHz to 1.5 GHz. The immunity characteristics are improved more than 10 to 30 dB over the frequency band from DC to 1.8 GHz.