BALUN transformer core material, BALUN transformer core and...

Details BALUN transformer core material, BALUN transformer core and... BALUN transformer core material, BALUN transformer core and...

2000-01-10

2001-04-17

Koslow, C. Melissa (Department: 1755)

Compositions

Magnetic

Iron-oxygen compound containing

C252S062590, C336S233000, C333S025000

Reexamination Certificate

active

06217790

ABSTRACT:

BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a BALUN transformer core material, a BALUN transformer core which is obtained by pressing and sintering the BALUN transformer core material, and a BALUN transformer which can be operated in a frequency band of 300 MHz or more.
(ii) Description of the Related Art
The BALUN transformer (Balance to Unbalance transformer: hereinafter abbreviated as BALUN) is a conversion component for smoothly connecting an unbalance circuit and a balance circuit, and used for various electronic apparatus, e.g., an antenna in a communication circuit and the like. Additionally, since the electronic apparatus have been made compact and operated at a high frequency in recent years, an essential countermeasure needs to be taken on constituent components of the electronic apparatus. The BALUN transformer is not an exception.
The BALUN transformer usually has a structure in which a conductor wire constituted of a metal is wound double around a toroidal or solenoid BALUN transformer core to form a winding (bifilar winding). As the BALUN transformer core, there is used a BALUN transformer core which is obtained by pressing and sintering a BALUN transformer core material having a high magnetic permeability, e.g., a spinel Ni—Cu—Zn ferrite as an oxide magnetic material. The spinel Ni—Cu—Zn ferrite has a relatively high magnetic permeability and specific resistance, and is not only used as the BALUN transformer core material but also frequently used in a high-frequency coil or other various electronic components.
However, the magnetic permeability of the spinel ferrite including the Ni—Cu—Zn ferrite has a frequency property. The magnetic permeability is reduced in a band of frequencies higher than frequencies at which ferrite starts resonance. Sufficient properties of the BALUN transformer cannot be obtained. There arises a problem that the core material cannot catch up with the high-frequency operation of the BALUN transformer.
To solve the problem, by lowering the magnetic permeability of the spinel ferrite and shifting the frequency at which resonance starts toward a high-frequency side to reduce a resonance loss, the BALUN transformer operable at a high frequency can be obtained. However, the ferrite has a logic of “Snake's limiting line”. Therefore, it is impossible to raise the frequency at which the resonance starts up to a high-frequency band exceeding the limitation. A BALUN transformer cannot be realized which provides an excellent property in the high-frequency band.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a BALUN transformer core material and a BALUN transformer core which can realize a high-property BALUN transformer which can be operated in a high-frequency band of 300 MHz or more and to provide a BALUN transformer which can be operated in a high-frequency band of 300 MHz or more.
To attain this and other objects, the present invention provides a BALUN transformer core material which contains a Z-type hexagonal system ferrite. Since the Z-type hexagonal system ferrite contained in the BALUN transformer core material has an in-plane anisotropy and a high magnetic permeability and a resonance frequency is in excess of the Snake's limiting line, the frequency properties of the magnetic permeability are extremely good.
Furthermore, the BALUN transformer core of the present invention is constituted of a sintered material of a ferrite obtained by pressing and sintering the BALUN transformer core material which contains the Z-type hexagonal system ferrite. The BALUN transformer core has a high initial magnetic permeability and specific resistance.
Moreover, the BALUN transformer of the present invention is obtained by applying a winding to the BALUN transformer core having the high magnetic permeability constituted of a sintered material of the ferrite obtained by pressing and sintering the BALUN transformer core material containing the Z-type hexagonal system ferrite. The BALUN transformer is provided with superior properties which are not poorer as compared with the BALUN transformer constituted of a conventional spinel ferrite, and it can also be used in a high-frequency band of 300 MHz or more at which the properties of the conventional BALUN transformer are deteriorated. The compact BALUN transformer with high properties have opened up possibilities of making chips.


REFERENCES:
patent: 3100852 (1963-08-01), Peek et al.
patent: 5593612 (1997-01-01), Lubitz
patent: 5954992 (1999-09-01), Onizuka et al.
patent: 6033593 (2000-03-01), Onizuka et al.
patent: 9-110432 (1997-04-01), None

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