GB2358290A

GB2358290A - Nonreciprocal circuit element

Info

Publication number: GB2358290A
Application number: GB0027602A
Authority: GB
Inventors: Satoru Shinmura; Masaru Fujino; Takashi Takagi; Takenori Sekijima
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 1999-11-15
Filing date: 2000-11-10
Publication date: 2001-07-18
Anticipated expiration: 2020-11-10
Also published as: GB0027602D0; GB2358290B; CN1296307A; JP2001144508A; KR100431143B1; KR20010060283A; DE10056543A1

Abstract

A nonreciprocal circuit element 10 has a magnetic member 22 and a magnet 24 for applying a DC magnetic field to said magnetic member, wherein the magnetic member has a ferromagnetic resonance half width of about 200 A/m or less. The member is preferably a magnetic garnet single crystal material.

Description

2358290

NONRECIPROCAL CIRCUIT ELEMENT BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a nonreciprocal circuit element, and more specifically, to a nonreciprocal circuit element such as a circulator and an isolator, for use in a microwave band. 2. Description of the Related Art

Generally, lumped constant isolators employed in mobile communication appliances such as cellular telephones serve to pass signals only in the transmission direction while blocking the signal in the opposite direction. As the demand for smaller and lighter mobile communication appliances grows, the lumped constant isolators are also required to be smaller and lighter.

However, the problem is that when the size of the component in the conventional lumped constant isolator is reduced, the low insertion loss property, a property critical for the isolators, is degraded. SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a nonreciprocal circuit element which meets the demand for a smaller and lighter element.

A nonreciprocal circuit element according to the present invention has a magnetic member and a magnet for applying a DC magnetic field to the magnetic member. The nonreciprocal circuit element is characterized in having a ferromagnetic resonance half width of the magnetic member at about 200 A/m or less.

In the nonreciprocal circuit element according to the present invention, the magnetic member is preferably made of a single crystal material, and more preferably, a magnetic garnet single crystal material.

Since the nonreciprocal circuit element of the present invention uses the magnetic member having the ferromagnetic resonance half width of about 200 A/m or less, reducing the size and weight thereof while maintaining the low insertion loss property can be achieved.

For the purpose of illustrating the invention, there is shown in the drawing a form which is presently preferred, it being understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown.

BRIEF DESCRIPTION OF THE DRAWING

Fig. I is an assembly view showing a lumped constant isolator in which the present invention is applied is presented.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, the preferred embodiments of the present invention are explained in dat ilil with reference to the drawings.

Example I

Fi I is an assembly view of a lumped constant isolator according to one aspect oil. t 9 present invention. A lumped constant isolator 10 includes an upper yoke 12 and a lower y6le 14. Between the upper yoke 12 and the lower yoke 14, a housing 16 made of resin is provided. In the housing 16, three capacitors 18, a resistor 20, a magnetic garnet 22 as a magnetic material, and a permanent magnet 24 are accommodated. Here, on the surface of the magnetic garnet 22, three central conductors 26 which are electrically isolated from ont i another are stacked so as to form an angle of 120 degrees therebetween. Among the three central conductors 26, two of the central conductors 26 are connected to two of capacitors j for the purpose of impedance matching, each of the two central conductors 26 being connected to one of the two capacitors 18, one being the input terminal and the other bein-q the output terminal, at one end thereof. The other end of each is grounded. The remaining central conductor 26 is connected to one of the capacitors 18 and to a resistor 20 so that tlwp central conductor 26 operates as an isolator. The other end is grounded. The lumped constant isolator 10 shown in Fig. I is formed so as to have measurements of 1.6 mm x 1.6 mm x 0.6 mm.

Example I employs, as the magnetic garnet 22 in the lumped constant isolator 10 shown in Fig. 1, a slice of 0.5 mm diameter and 0.2 mm thickness, cut from single crystal materials (Y3Fe5O12) having various ferromagnetic resonance half width. The single cryst-,kl are grown by the floating zone method. Table I shows the relationship between a ferromagnetic resonance half width and insertion loss at I GHz in Example 1.

1. 1 Table 1

Sample Ferromagnetic resonance Insertion loss Number half width (A/m) (dB) 1 60 0.9 2 120 1.2 3 160 1.5 4 200 2.0 240 2.

As shown in Table 1, samples 1 to 4 whose ferromagnetic resonance half widths are 200 A/m (about 2.50e) or less have an insertion loss of less than 2.0 dB and are thus preferable for use as isolators. Sample 5 whose the ferromagnetic resonance half width is more than 200 A/m, however, has the insertion loss greater than 2.0 dB and is not suitable for use as an isolator.

It should be noted that the sample indicated by the number with an asterisk is not within the scope of the present invention. Others are in the scope of the present invention. Example 2 Example 2 employs, as the magnetic garnet 22 in the lumped constant isolator 10 shown in Fig. 1, a slice of 0.5 mm diameter and 0.2 mm thickness, cut from single crystal materials (Y3Fe5012) having various ferromagnetic resonance half widths. The single crystals are grown by the flux method. Table 2 shows the relationship between a ferromagnetic resonance half width and insertion loss at 1 GHz in Example 2.

Table 2

Sample Number Ferromagnetic resonance half Insertion loss width (A/m) (dB) 6 80 1.1 7 140.6 8 180 1.9 9 260 2.6 As shown in Table 2, even when magnetic garnet single crystals grown by the flux method are concerned, samples 6 to 8 whose ferromagnetic resonance half widths are 200 A/m or less have the insertion loss of less than 2.0 dB and are thus preferable for use as isolators. Sample 9 whose the ferromagnetic resonance half width is more than 200 A/m, 1 i i It should be noted that the sample indicated by the number with an asterisk is not within the scope of the present invention. Others are in the scope of the present invention. Example 3 3 Example 33 employs, as the magnetic garnet 22 in the lumped constant isolator 10 shown in Fig. 1, a slice which has 0.5 mi-n diameter, a 0. 1 - mm-thick magnetic garnet single crystal material and a 0. 1 -mm-thick nonmagnetic garnet single crystal material, cut from single crystal materials (Y3Fe5012) having various ferromagnetic resonance half widths. Tfi single crystals are grown by the liquid phase epitaxial growth method. Table 3 shows the relationship between a ferromagnetic resonance half width and insertion loss at 1 GHz in Example 3.

1: 1 As shown in Table 3, even when the magnetic garnet single crystals grown by the liquid phase epitaxial growth method, samples 10 to 12 whose ferromagnetic resonance hall widths are 200 A/m or less have the insertion loss of less than 2.0 dB and are thus preferabll for use as isolators. Sample 1 whose ferromagnetic resonance half width is more than 200 A/m, however, has the insertion loss greater than 2.0 dB and is not suitable for use as an isolator.

It should be noted that the sample indicated by the number with an asterisk is not within the scope of the present invention. Others are in the scope of the present invention..

As is understood from the above-described examples, the ferromagnetic resonance half width of the ferromagnetic member is not simply determined by a composition ratio.---Fpr example, in the case where the ferromagnetic material is a polycrystal, the ferromagnetic resonance half width may depend on a sintering density of the ferromagnetic member. In lh6, case where the ferromagnetic member is a single crystal, the crystalinity and surface state o Table 3

Sample Number Ferromagnetic resonance insertion loss half width (A/m) (dB) 330 0.7 11 80 0.9 12 200 2.0 260 2.5 -5the ferromagnetic member affects the ferromagnetic resonance half width thereof It is therefore important to adjust the ferromagnetic resonance half width such that the magnetic member has a ferromagnetic resonance half width of 200 A/m or less. As long as the ferromagnetic resonance half width is about 200 A/m or less, the magnetic member may be Y3Fe5O12 in which a portion of Y is replaced with Bi or rare earth elements other than Y and a portion of Fe is replaced with Ga, Al, In or Sc.

It is to be noted that page 8 of "High-Frequency Device Components and Equipment Design" (1997) published by Mimatsu Data System shows samples of ferromagnetic resonance half widths regarding magnetic garnets employed as magnetic members of the lumped constant isolators presently on the market. According to this, 398 A/m is the lowest value.

It is also to be noted that Japanese Unexamined Patent Publication No. 10233308 discloses polycrystal ceramic magnetic material which has a small ferromagnetic resonance half width and is suitable for nonreciprocal circuit elements. According to the document, a smallest ferromagnetic resonance half width is 160e (1280 A/rn), which far larger than the value used in the present Invention. In addition, the ferromagnetic member in the document has a disc shape having a diameter of 25 mm, and a thickness of 1.5 mm.

It should be noted that although each of the above-described examples is described in terms of the lumped constant isolators in the I GHz band, the present invention is applicable to other frequency bands and to other types of the nonreciprocal circuit elements other than isolators, such as circulators. Furthermore, the overall configuration of the nonreciprocal circuit element according to the present invention is not limited to the configuration shown in Fig. 1.

While preferred embodiments of the invention have been disclosed, various modes of carrying out the principles disclosed herein are contemplated as being within the scope of the following claims. Therefore, it is understood that the scope of the invention is not to be limited except as otherwise set forth in the claims.

Claims

-6CLAIMS

1 A nonreciprocal circuit element comprising a magnetic member and a mago t for applying a DC magnetic field to said magnetic member, wherein said magnetic memt)ttr',, has a ferromagnetic resonance half width of about 200 A/m or less.

2. A nonreciprocal circuit element according to Claim 1, wherein said magnet ic member comprises a single crystal material.

13. A nonreciprocal circuit element according to Claim 2, wherel n said single crystal comprises a Y3Fe5012 which optionally contains at least one of Bi, Ga, AI, In, Sc ail a 1 rare earth element.

4. A nonreciprocal circuit element according to Claim 1, wherein said magned a member comprises a magnetic garnet single crystal material.

5. A nonreciprocal circuit element according to Claim 1, wherein the ferromagnetic resonance half width is about 180 A/m or less.

6. A nonreciprocal circuit element according to any one of Claims 1 to 5, wherein said nonreciprocal circuit element is an isolator.

7. A nonreciprocal circuit element according to any one of Claims 1 to 5, wherein said nonreciprocal circuit element is a lumped constant isolator.

8. A nonreciprocal circuit element according to any one of Claims 1 to 5, wherein said nonreciprocal circuit element is a circulator.

1:

9.. A nonreciprocal circuit element substantially as hereinbefore described with reference to the accompanying drawing.

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9. A nonreciprocal circuit element substantially as hereinbefore described with, reference to the accompanying drawing.

Amendments to the claims have been filed as follows -' -7 CLAIMS 1. A nonreciprocal circuit element comprising a magnetic member and a magnet for applying a DC magnetic field to said magnetic member, wherein said magnetic member has a ferrornagnetic resonance half width of 200 A/m or less and the nonreciprocal circuit element has an insertion loss of 2. 0 dB or less.

2. A nonreciprocal circuit element accord.ing to Claim 1, wherein said magnetic member comprises a single crystal material.

3. A nonreciprocal circuit element according to Claim 2, wherein said single crystal comprises a Y3Fe5012 which optionally contains at least one of Bi, Ga, AI, In, Sc and a rare earth element.

4. A nonreciprocal circuit element according to Claim 1, wherein said magnetic member comprises a magnetic garnet single crystal material.

6. A nonreciprocal.circuit element according to any one of Claims 1 to 5, wherein said nonreciprocal circuit element is an isolator.