1. Field of Invention
The present invention relates to a magnetic composite tape for inhibiting radiation noise and a radiation noise inhibiting component using such a magnetic composite tape.
2. Description of Related Art
Conventionally, when suppressing noise radiated from an interface cable or a head cable (power supply cable), a ferrite ring core or a cylindrical resin member containing a ferrite (cylindrical magnetic member) are inserted into the cable to generate a common-mode impedance and the noise is suppressed due to the generation of such impedance. Moreover, apart from this, by winding a tape-like magnetic rubber onto a predetermined portion of the cable, common-mode impedance is generated as with the above-mentioned ferrite ring core, and the noise is further suppressed.
When the noise is suppressed using the ferrite ring core or the cylindrical resin containing a ferrite, an outer diameter R1 of the ferrite ring core or the like and an inner diameter R2 thereof have a relationship such that the common-mode impedance generated is proportional to (R1-R2)/(R1+R2) and is also proportional to the length of the ferrite ring core or the like. Therefore, in order to obtain a large common-mode impedance, the ferrite ring or the like must have a relatively large size. Moreover, even if a material which has a high initial permeability is used, the so-called "Snoek's limit" phenomenon occurs. With this phenomenon, there is a problem that permeability decreases at the high-frequency area and consequently, the common-mode impedance does not increase to the extent expected. Furthermore, it is known that the ferrite ring core or the like is covered with a conductive member and the conductive member is grounded, then, a radiation noise inhibiting effect can be improved. However, when using the ferrite ring core or the like, it is necessary to provide the conductive member with the ferrite core before connecting the cable with a connector.
When suppressing noise by using a tape-like magnetic rubber, in order to obtain a large noise suppression effect, it is necessary to increase the common-mode impedance by methods such as winding the tape-like magnetic rubber for many turns to achieve the desired thickness of the magnetic rubber or extending the length along which the magnetic rubber is wound on the cable. Moreover, it is known that a large radiation noise inhibiting effect can be obtained by winding the tape-like magnetic rubber onto the cable and accommodating the wound magnetic rubber in a conductive case. However, the provision of the tape-like magnetic rubber and that of the conductive case must be performed separately and requires very complicated assembling processes.