A study on suppression of self resonance of metal chassis by means of the hybrid magnetic material

Many noise suppression techniques have been applied and put to practical use, but in the near future, the signal processing speed and frequency spectrum will become increasingly higher, and the size of equipment will become smaller, and so new technology to reduce EMI radiation and to enhance immunity are still demanded. It is expected that not only the interference between inter-systems by EMI radiation from the equipment but also the interference inside the equipment causes the degradation of system reliability. The equipment cabinet constructed of conductive materials has self-resonance frequency. When electromagnetic excitation occurs inside the cabinet by EMI radiation from inner circuits, the strong electromagnetic field is generated inside the cabinet at the self-resonance frequency, makes EMI radiation from cabinet increase and degrades the immunity of the inner circuit. To suppress the radiation from the cabinet and interface cable by suppressing Q of the self-resonance and to enhance immunity are requested. The authors propose to use hybrid magnetic materials which contain magnetic material and dielectric material in order to suppress the value of Q and verify the effect.