Noise-limiting transformer apparatus and method for making

• US 5,956,073 A
• Filed: 12/19/1996
• Issued: 09/21/1999
• Est. Priority Date: 12/19/1996
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Nemchik, Joseph Michael, Jin, Sungho, Zhu, Wei, Van Dover, Robert Bruce
• Primary Examiner(s): FLYNN, NATHAN J
• Application Number:
  US08/770,613
• Time in Patent Office: 1,006 Days
• Field of Search: 336/182, 336/220, 336/30, 336/160, 336/165, 336/221, 336/233, 336/178
• US Class Current: 725/105
• CPC Class Codes: H01F 17/04 with magnetic core
• CPC Class Codes: H01F 19/04 Transformers or mutual inductances suitable for handling frequencies considerably beyond the audio range resonant circuits H03H
• CPC Class Codes: H01F 3/10 Composite arrangements of magnetic circuits
• CPC Class Codes: H01F 38/02 for non-linear operation

Abstract

Embodiments of the invention include a transformer device having a saturation region for limiting ingress noise and other noise. The transformer comprises a magnetic core, an input coil and an output coil arranged so that the output signal caused by the magnetic linkage between the input and output coils through the magnetic core is based on the magnitude of the input signal. According to an embodiment of the invention, the magnetic core includes a saturation region that limits the output signal regardless of the magnitude of the input signal once the saturation region reaches its saturation magnetization state. The saturation region comprises a reduced saturation magnetization level caused by a geometrically constricted region of the magnetic core or, alternatively, by a modified, magnetic-equivalent region having properties similar to a geometrically constricted region.

Claims

1. A transformer, comprising:

a magnetic core having at least one input region and at least one output region wherein said input region and said output region are coaxial;

an input coil for transmitting an input signal, at least a portion of said input coil being wound around at least a portion of said input region; and

an output coil for transmitting an output signal, at least a portion of said output coil being wound around at least a portion of said output region,

said magnetic core capable of flowing a flux that magnetically couples said input and output coils in such a way that said output signal varies in response to said input signal,

said magnetic core including a saturation region in no more than one of said input region and said output region capable of a saturation magnetization state whereby said saturation region limits the flow of said flux through said magnetic core and thus the magnitude of said output signal, said saturation magnetization state limiting said output signal in such a way that said output signal does not vary in response to said input signal, wherein said saturation region is one of a geometrically constricted region of said magnetic core or a portion of the magnetic core modified to be the magnetic equivalent of a geometrically constricted region of said magnetic core, wherein said modification is selected from the group consisting of altering the chemical composition of said saturation region, altering the crystal structure of said saturation region and altering the internal stress state of said saturation region in such a way that said saturation region is the magnetic equivalent of a geometrically constricted region.

2. The transformer as recited in claim 1, wherein said magnetic core is made of one or more materials selected from the group consisting of a Fe-rich alloy and a Co--Fe-based alloy.

3. The transformer as recited in claim 1, wherein said magnetic core has a magnetic-hysteresis (M-H) loop squareness ratio greater than or equal to approximately 0.85.

4. The transformer as recited in claim 1, wherein said magnetic core has an anisotropy field, H_a, greater than or equal to approximately 2 oersted (Oe).

5. The transformer as recited in claim 1, wherein said magnetic core has a saturation magnetization, 4π

M_s, greater than approximately 3 kilogauss (kG).

6. The transformer as recited in claim 1, wherein said magnetic core has a coercivity, H_c, greater than or equal to approximately 10 oersted (Oe).

7. The transformer as recited in claim 1, wherein said magnetic core has a ferromagnetic resonance (FMR) frequency of at least 0.1 GHz.

8. The transformer as recited in claim 1, wherein said magnetic core further comprises a linear body having said output region in spaced relation to said input region and wherein said saturation region is formed therebetween.

9. The transformer as recited in claim 1, wherein said magnetic core further comprises a square frame having an input leg region, an opposing output leg region substantially parallel to and spaced apart from said input leg region, and a pair of connecting legs substantially perpendicular to said input and output leg regions, and wherein said saturation region is formed in at least one of said connecting leg regions.

10. The transformer as recited in claim 1, further comprising at least one permanent magnet in spaced relation to said transformer in such a way that a bias field at least 20 Oe is applied to said transformer in the easy axis direction.

11. The transformer as recited in claim 1, further comprising a film layer formed on at least one side of soft magnetic core for exchange-biasing said magnetic core, said film layer made of a material selected from the group consisting of an antiferromagnetic materials and a ferromagnetic material.

12. A method for making a noise-limiting transformer, said method comprising the steps of:

providing a magnetic core having at least one input region and at least one output region, wherein said input region and said output region are coaxial, said input region having associated therewith an input coil for transmitting an input signal and said output region having associated therewith an output coil for transmitting an output signal, said magnetic core capable of flowing a flux that magnetically couples said input and output coils in such a way that said output signal varies in response to said input signal; and

forming at least one saturation region within said magnetic core for limiting the flow of said flux through said magnetic core in such a way that the magnitude of said flux output signal is limited and does not vary in response to said input signal, wherein said forming step comprises geometrically constricting the volume of a portion of said magnetic core between said input and output regions.

13. The method as recited in claim 12, wherein said forming step comprises altering the chemical composition of a portion said magnetic core between said input and output regions in such a way that the magnitude of said output signal is limited and does not vary in response to said input signal.

14. The method as recited in claim 12, wherein said forming step comprises altering the internal stress state of said saturation region in such a way that the magnitude of said output signal is limited and does not vary in response to said input signal.

15. The method as recited in claim 12, wherein said forming step further comprises selectively patterning said magnetic core.

16. The method as recited in claim 12, wherein said input and output coils are formed by depositing a thin film of an electrically conductive material on said transformer and patterning said thin film in such a way to form said input and output coils.

17. A transformer, comprising:

a magnetic core having at least one input region and at least one output region;

an input coil for transmitting an input signal, at least a portion of said input coil being wound around at least a portion of said input region; and

an output coil for transmitting an output signal, at least a portion of said output coil being wound around at least a portion of said output region,

said magnetic core capable of flowing a flux that magnetically couples said input and output coils in such a way that said output signal varies in response to said input signal,

said magnetic core including a saturation region between said input region and said output region capable of a saturation magnetization state whereby said saturation region limits the flow of said flux through said magnetic core and thus the magnitude of said output signal, said saturation magnetization state limiting said output signal in such a way that said output signal does not vary in response to said input signal, wherein said saturation region is one of a geometrically constricted region of said magnetic core or a portion of the magnetic core modified to be the magnetic equivalent of a geometrically constricted region of said magnetic core, wherein said modification is selected from the group consisting of altering the chemical composition of said saturation region, altering the crystal structure of said saturation region and altering the internal stress state of said saturation region in such a way that said saturation region is the magnetic equivalent of a geometrically constricted region.