Compositions – Magnetic – With wax – bitumen – resin – or gum
Patent
1998-05-28
2000-04-18
Koslow, C. Melissa
Compositions
Magnetic
With wax, bitumen, resin, or gum
252 6255, 307 71, H01R 100, H01Q 1700, H05K 900
Patent
active
060511567
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an electromagnetic interference suppressing body for a high frequency region, particularly, a microwave band, and in particular, to a composite magnetic material therefor.
BACKGROUND ART
In recent years, the spread of electronic devices, including digital electronic devices, using high frequency waves has been advanced and, among them, the spread of mobile communication devices using quasi-microwave bands or microwave bands has been remarkable. In those mobile communication devices represented by portable telephones, demands for reduction in size and weight are so great that high-density mounting of electronic components has become the greatest technical problem. Accordingly, since the electronic components, the printed wiring, the inter-module wiring, etc. which are mounted overcrowdedly, approach to each other extremely, and further since the speed-up of the signal processing speed is schemed, the inter-line coupling due to the electrostatic coupling and/or the electromagnetic coupling becomes large and interference due to radiant noise or the like is caused, so that not a few situations have occurred wherein normal operations of the devices are impeded.
Conventionally, against such so-called high-frequency electromagnetic interference, a measure has been mainly taken to apply a conductor shield.
However, since the conductor shield is an electromagnetic interference countermeasure utilizing reflection of electromagnetic waves due to impedance mismatch relative to the space, it can provide a shielding effect but has a drawback to promote the electromagnetic coupling due to reflection from an undesired radiation source. For solving such a drawback, it could be considered effective as a secondary electromagnetic interference countermeasure to use a magnetic loss of a magnetic body, that is, an imaginary part permeability .mu." so as to suppress the undesired radiation.
It has been known that the absorption efficiency of undesired radiation increases corresponding to a magnitude of .mu." in a frequency range where .mu.">.mu.'. Accordingly, for obtaining a large magnetic loss at a microwave band, it is necessary to realize a characteristic where the real part permeability attenuates due to the magnetic resonance at a VHF band (30 MHz to 300 MHz), a quasi-microwave band (300 MHz to 3 GHz) or a low-frequency side of a microwave band (3 GHz to approximately 10 GHz).
Therefore, it is an object of the present invention to provide a composite magnetic body where the magnetic resonance appears in a range from VHF band to microwave band and, as a result, a magnetic loss at the microwave band is large (that is, an imaginary part permeability .mu." is large). It is another object to provide an electromagnetic interference suppressing body using such a composite magnetic body.
DISCLOSURE OF THE INVENTION
According to the present invention, there is obtained a composite magnetic body characterized in that semi-hard magnetic powder is bonded by an organic bonding agent, and a magnetic resonance appears in a range from VHF band to microwave band.
The foregoing semi-hard magnetic powder is characterized in that a coercive force Hc thereof is 10 to 300 Oe.
The foregoing semi-hard magnetic powder is characterized by having a flat or needle shape and being oriented/aligned in the composite magnetic body.
As a material of the foregoing semi-hard magnetic powder, a magnetic metal alloy, such as Fe--Co--Mo alloy, Co--Fe--Nb alloy or Fe--Co--V alloy, can be cited.
Further, as another material of the foregoing semi-hard magnetic powder, an oxide magnetic body, such as .gamma.-Fe.sub.2 O.sub.3 (maghemite) or Co--Ti substituted Ba ferrite, can be cited.
According to the present invention, there is obtained an electromagnetic interference suppressing body using, as a material thereof, the foregoing composite magnetic body, and having a large magnetic lose at a microwave band.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram schematically showing a section of a composit
REFERENCES:
patent: 3047428 (1962-07-01), Goto et al.
patent: 3652334 (1972-03-01), Abeck et al.
patent: 4585568 (1986-04-01), Nagai et al.
patent: 5093100 (1992-03-01), Sadamura et al.
patent: 5123989 (1992-06-01), Horiishi et al.
Kamei Koji
Sato Mitsuharu
Yoshida Shigeyoshi
Koslow C. Melissa
Tokin Corporation
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