| 摘要 |
PROBLEM TO BE SOLVED: To provide a shielding material for coil, which will hardly change the resonance frequency of a resonance circuit, even when the material is put around a coil in the resonance circuit, and in addition, will hardly change the resonance frequency nor lowers the Q-value of the circuit, even if the material is coupled electromagnetically with an outside object. SOLUTION: Since the inductance variation of the coil 12 is offset by means of a magnetized soft magnetic material 22 and a conductive material 23 in which an eddy current is induced, the resonance frequency of the resonance circuit will hardly change, even when the shielding material 21 is put around the coil 12. In addition, since the leakage magnetic flux from the coil 12 and the electromagnetic coupling between the coil 12 and outside object are weakened by the materials 22 and 23, the resonance frequency is hardly changed by the object outside. Moreover, when a nonconductive material is used as the soft magnetic material 22 and a nonmagnetic material is used as the conductive material 22, the eddy current losses which occur in the soft magnetic material 22 and conductive material 23 are reduced, and since the leakage magnetic flux from the coil 12 is weakened by the materials 22 and 23 and the eddy current loss which occurs in the outside object is made smaller, the Q-value of the resonance circuit hardly drops.
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