| 摘要 |
<p>PURPOSE:To enable a magnetic shield high in shielding ratio to be realized at low cost by making the magnetic characteristics of a magnetic layer angular magnetization characteristics and specifying the thickness of the magnetic layer and the shaking magnetic field frequency. CONSTITUTION:Considering the case that a low frequency magnetic field with a small oscillation width is applied, and the size of its magnetic field increases from O to H, magnetization curves 2a, b, c and d shift to other magnetization curves 4a', b', c' and d' so that the amounts of shifting in the direction of H axis may be H along the inclination of the angular magnetization curves 3. At this time, the change of magnetic flux density which is viewed using such a low area filter as to pass the component of f is B. Accordingly, the effective permeability to the frequency 5 is B/ H, and this becomes almost equal to the very great inclination of the angular magnetization curve 3, that is, the differential permeability. Hereby, the thickness of a magnetic layer is made several tens mum to several hundreds mum, and the shaking frequency is elevated to several hundreds Hz to several tens kHz, whereby enough shaking characteristics can be obtained, and also the leakage component of a shaking magnetic field can be attenuated enough by the eddy currents shield by a good conductor plate placed on the rear of the magnetic layer.</p> |
