JPH11112208A - Irreversible circuit element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an irreversible characteristic and to make an element to be thin by thinning the peripheral part of a ferrite plate so that the size of the thickness direction component of a DC magnetic field applied to the inner part of the ferrite plate W becomes almost uniform for the whole ferrite plate. SOLUTION: A permanent magnet 12 and the ferrite plate 11 are provided in a metal case 13 so that they face each other through a central conductor 14. The face of the ferrite plate 11, which faces the base of the case 13, is formed in a convex form and magnetic flux is prevented from being concentrated on the peripheral part. Thus, the magnetic field generated by the permanent magnet 12 is applied in the ferrite plate 11 so that the thickness direction component becomes almost uniform. The ferrite plate 11 is uniformly magnetized in the thickness direction. Namely, the magnetic field applied by the permanent magnet 12 sets the thickness of the respective parts of the ferrite plate 11 so that the thickness direction component in the ferrite plate 11 becomes almost uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-reciprocal circuit device such as a circulator and an isolator used mainly in a microwave band.

[0002]

2. Description of the Related Art Circulators and isolators used in the microwave band are used for both base stations and terminals in wireless communications such as portable telephones. The distributed constant type is mainly used for base stations, and the lumped constant type is mainly used for terminals. A conventional distributed constant type circulator has a central conductor 174 as shown in FIG.
And a disk-shaped ferrite plate 171 provided so as to sandwich the center conductor 174, permanent magnets 172 provided above and below via a ground conductor plate 175, and a support 176 provided above and below the permanent magnet 172. And a case 173 provided therethrough. The conventional lumped-constant type circulator is provided between a ferrite plate 181 and a permanent magnet 182 and a ferrite plate 181 and a permanent magnet 182 provided opposite to each other, for example, as shown in FIG. , Center conductors 184a, 184b, 184c
And a case 183a, 183b for accommodating them. Here, in the circulator of FIG. 15 or FIG.
72, 182, the ferrite plate 171,
The distance between 181 and permanent magnets 172 and 182 is set such that a magnetic field having a predetermined strength is applied in the thickness direction of ferrite plates 171 and 181. As a result, the ferrite plates 171 and 181 are magnetized in the thickness direction at a predetermined rate corresponding to the used frequency.

The circulator configured as described above outputs a high-frequency signal input from the input / output terminal Ta from the input / output terminal Tb, and outputs a high-frequency signal input from the input / output terminal Tb from the input / output terminal Tc. , Input / output terminal Tc
From the input / output terminal Ta. In addition, the isolator may be any one of the above-described configurations.
15 and 16, for example, when the input / output terminal Tc is terminated in FIGS. 15 and 16, a high-frequency signal input from the input / output terminal Ta can be output from the input / output terminal Tb. The high frequency signal input from the input / output terminal Tb can be prevented from being output from the input / output terminal Ta. The above is the basic operation of the circulator and the isolator. In both the distributed constant type and the lumped constant type, in addition to FIGS.
There are various types, such as a single magnet and a single or two permanent magnets for applying a DC magnetic field to the ferrite plate. In any case, in order to obtain good irreversible characteristics as the above-described circulator or isolator, it is important to apply a DC magnetic field uniformly in the thickness direction of the ferrite plate and uniformly magnetize the ferrite plate.

In recent years, individual devices such as circulators and isolators have also been required to be reduced in size and thickness in order to reduce the size of the equipment. However, when the size and thickness are reduced, it becomes difficult to obtain a uniform magnetic field strength. An even more important issue is how to apply a uniform magnetic field inside the ferrite plate to uniformly magnetize the ferrite plate. Conventionally, as a method for obtaining the uniformity of the magnetization state of the ferrite plate, as disclosed in Japanese Patent Application Laid-Open No. 49-73949, the surface of the permanent magnet 192 facing the ferrite plate 191 is thickened at the center. And rounded (Fig. 1
7), as disclosed in Japanese Patent Application Laid-Open No. 7-326908, there has been proposed a method of providing a depression 202 on the bottom surface of a shield case 201 as shown in FIG.

[0005]

However, in the conventional circulator (or isolator), FIG.
As shown in the figure, in the part near the center of the ferrite plate, almost uniform magnetic field strength is obtained, but the magnetic flux concentrates in the peripheral part of the ferrite plate, the magnetic field strength in the peripheral part increases, and the magnetization is There was a problem of non-uniformity. The concentration of the magnetic flux in the peripheral portion becomes more remarkable when the distance between the ferrite plate and the permanent magnet and the distance between the ferrite plate and the case are reduced in order to reduce the size and thickness of the circulator and the isolator. As indicated by the dotted line, the magnetic field intensity at the peripheral portion was further increased, resulting in greater nonuniform magnetization. For this reason, the irreversible characteristics have been further deteriorated.

An object of the present invention is to provide a non-reciprocal circuit device which has good non-reciprocal characteristics and can be made thin.

[0007]

Means for Solving the Problems In order to achieve the above object, the present invention has been completed as a result of studying a structure capable of uniformly applying a magnetic field to a ferrite plate and uniformly magnetizing the ferrite plate. . That is, the non-reciprocal circuit device according to the present invention includes a ferrite plate having a predetermined shape, a magnet provided to face the ferrite plate and applying a DC magnetic field to the ferrite plate, the ferrite plate and the permanent magnet. And a case constituting a part of a magnetic circuit, wherein the magnitude of the thickness direction component of the DC magnetic field applied inside the ferrite plate is substantially uniform over the entire ferrite plate. In this case, the periphery of the ferrite plate is thinned.

The non-reciprocal circuit device can be easily formed by forming at least one of the upper surface and the lower surface of the ferrite plate into a convex shape which swells smoothly toward the center.

In the nonreciprocal circuit device, when the other surface of the ferrite plate is provided to face the permanent magnet, the ferrite plate is formed in a concave shape facing one surface of the ferrite plate. It is preferable that the case is fixed to the case via a support made of a non-magnetic material having a curved surface. Thereby, the ferrite plate can be stably fixed.

In the nonreciprocal circuit device, the surface of the permanent magnet facing the ferrite plate is formed in a convex shape that swells smoothly toward the center, and the surface of the ferrite plate facing the permanent magnet is formed. It is preferable to form a concave shape which is smoothly depressed toward the center.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic sectional view of a 1.5 GHz band lumped constant type isolator according to Embodiment 1 of the present invention. The isolator according to the first embodiment includes a metal case 1
3, a permanent magnet 12 and a ferrite plate 11 are provided so as to face each other with a center conductor 14 interposed therebetween.
Here, particularly in the isolator of the first embodiment, the surface of the ferrite plate 11 facing the bottom surface of the case 13 is formed in a convex shape so that the thickness of the ferrite plate 11 becomes thinner in the peripheral portion. The magnetic flux is prevented from being concentrated on the As a result, the magnetic field generated by the permanent magnet 12 is applied so that the component in the thickness direction is substantially uniform inside the ferrite plate 11, and the ferrite plate 11 is uniformly magnetized in the thickness direction. In other words, in the isolator of the first embodiment, the thickness of each part of the ferrite plate 11 is set such that the magnetic field applied by the permanent magnet 12 has a substantially uniform thickness direction component inside the ferrite plate 11. I have. In the isolator according to the first embodiment, the distance between the ferrite plate 11 and the bottom surface of the case 13 and the distance between the permanent magnet 13 and the upper surface of the metal case 13 are eliminated for the purpose of thinning.

Next, in the first embodiment, by forming the ferrite plate 11 so as to be thinner in the peripheral portion, it is possible to prevent the magnetic flux from concentrating on the peripheral portion and to reduce the ferrite plate 11 in the thickness direction. The reason why uniform magnetization can be achieved will be described. First, generally, the magnetic flux has a property of trying to pass through a portion having a high magnetic permeability. Therefore, if a ferrite plate with high magnetic permeability is provided in a space that had a uniform magnetic field strength without a ferrite plate, the magnetic flux located outside the ferrite plate passes through the ferrite plate so that it is absorbed by the ferrite plate. I will be. Also, the magnetic flux tends to pass through the space at the shortest distance, so if the ferrite plate has a uniform magnetic permeability in the radial direction, the magnetic flux sucked into the ferrite plate from outside will cause the magnetic flux to pass through the ferrite plate. You will concentrate on the periphery.

However, when the ferrite plate 11 is configured to be thinner in the peripheral portion as in the first embodiment, the effective magnetic permeability in the peripheral portion can be made lower than that in the central portion because of the thinner ferrite plate. Thus, the concentration of the magnetic flux in the peripheral portion can be reduced. In the present invention, utilizing such properties, the magnetic field is applied to the inside of the ferrite plate with a uniform intensity. In the isolator according to the first embodiment, considering that the irreversible characteristics of the irreversible circuit element depend on the uniformity of magnetization in the thickness direction of the ferrite plate, the thickness of the magnetic field applied to the ferrite plate is particularly large. The thickness of the ferrite plate is varied so that the direction component is uniform.

As described above, in the isolator according to the first embodiment of the present invention, the magnetic field applied by the permanent magnet 12 is adjusted so that the component in the thickness direction is substantially uniform inside the ferrite plate 11. Since the thickness of each part is set, the ferrite plate 11 can be uniformly magnetized in the thickness direction, so that the loss in the transmission direction can be reduced and the loss in the reverse direction can be reduced. That is, the isolator according to the first embodiment can have good irreversible characteristics.

In the isolator of the first embodiment described above, the surface of the ferrite plate 11 facing the bottom surface of the case 13 is formed in a convex shape. However, the present invention is not limited to this, and as shown in FIG. The permanent magnet 1
2 (hereinafter, referred to as a first modification). Even with the above configuration, it operates in the same manner as the first embodiment and has the same effect.

In the isolator according to the first embodiment,
As shown in FIG. 3, the ferrite plate is preferably fixed to the bottom of the case 13 via a support 15 made of a non-magnetic material having a concave surface facing the convex surface of the ferrite plate. By providing the non-magnetic support 15 having such a shape, the ferrite plate can be stably fixed and the characteristics can be prevented from being deteriorated due to, for example, displacement.

Based on the first embodiment and the first modification, a 1.5 GHz band lumped-constant isolator is manufactured and evaluated. In this example,
Although the ferrite plate 11 and the permanent magnet 12 are formed in a disk shape, in the present invention, the ferrite plate 11 and the permanent magnet 12 are not limited to the disk shape. FIG.
Is a graph showing the distribution of the component of the magnetic field strength in the thickness direction with respect to the radial position of the ferrite plate. In addition, as shown in FIG. 4, Comparative Example 1 in FIG. 5 is a measurement example by a conventional configuration using a simple disk-shaped ferrite plate 11a having a constant thickness. Here, in Comparative Example 1, components other than the ferrite plate 11a are configured in the same manner as in Embodiment 1 and Modified Example 1, and are denoted by the same reference numerals in FIG. As is apparent from FIG. 5, in the first embodiment and the first modification according to the present invention, the concentration of the magnetic flux in the peripheral portion of the ferrite plate 11 is reduced, and the thickness direction component of the magnetic field intensity is reduced in the radial direction of the ferrite plate. It can be seen that the distribution is almost uniform. FIG. 6 shows the electrical characteristics of the isolators according to the first embodiment and the first comparative example. It can be seen that the device characteristics are improved due to relaxation of the magnetic flux concentration on the periphery of the ferrite plate 11. In the first embodiment and the modified example described above, the description has been made using the 1.5 GHz band lumped constant type isolator. However, it is needless to say that the same effect can be obtained even with another frequency, distributed constant type or circulator. .

(Embodiment 2) FIG. 7 is a schematic sectional view of a 900 MHz band distributed constant circulator according to Embodiment 2 of the present invention. The circulator according to the second embodiment includes:
A pair of permanent magnets 72 are provided in a metal case 73 so as to face each other at a predetermined interval, and a center conductor sandwiched between a pair of ferrite plates 71 is provided between the pair of permanent magnets. It is composed. Here, each of the pair of ferrite plates 71 has a central conductor 74 such that one surface is formed in a convex shape and the other surface (flat surface) faces each other.
Are sandwiched between them. In the circulator according to the second embodiment, similarly to the isolator according to the first embodiment, the magnetic field applied by the permanent magnet 72 is applied to the ferrite plate 7.
The thickness of each part of the ferrite plate 71 is set so that the components in the thickness direction are substantially uniform inside one.

Therefore, the circulator according to the second embodiment of the present invention configured as described above has a ferrite plate 7
1 can be uniformly magnetized in the thickness direction, the loss in the transmission direction can be reduced, and the loss in the reverse direction can be reduced. That is, the circulator of the second embodiment can improve the irreversible characteristics. A sample was manufactured based on the circulator of the second embodiment, and the intensity distribution of the magnetic field applied to the ferrite plate 71 and the characteristics of the circulator were evaluated. The results are shown in FIGS. 9 and 10, respectively. In this example, the ferrite plate 71 and the permanent magnet 72 are formed in a disk shape. However, in the present invention, the ferrite plate 71 and the permanent magnet 72 are not limited to the disk shape. In addition, for comparison with the circulator of the second embodiment, a circulator of a comparative example (hereinafter referred to as comparative example 2) shown in FIG. 8 was manufactured and similarly evaluated, and shown in FIGS. 9 and 10. here,
Comparative Example 2 shown in FIG. 8 has the same configuration as that of Embodiment 2 except that a simple disk-shaped ferrite plate 71a having a constant thickness is used.

As apparent from FIG. 9, Embodiment 2
In the circulator of (1), the magnetic field is applied almost uniformly to any position in the radial direction with respect to the ferrite plate 71, but in Comparative Example 2, the magnetic field is applied to the periphery of the ferrite plate in a concentrated manner. . Thus, the electrical characteristics of the circulator according to the second embodiment of the present invention are superior to those of the second comparative example, as shown in FIG. In the second embodiment, a 900 MHz band distributed constant type circulator has been described. However, it is needless to say that a similar effect can be obtained with another frequency, a lumped constant type, and an isolator.

(Embodiment 3) FIG. 11 shows Embodiment 3 of the present invention.
FIG. 2 is a schematic cross-sectional view of the isolator of FIG. Embodiment 3
Is different from the isolator according to the first embodiment in FIG. 1 in that a permanent magnet 17 is used instead of the permanent magnet 13 and a ferrite plate 16 is used instead of the ferrite plate 11. The configuration is the same as Here, in the third embodiment, the permanent magnet 17 has a surface facing the ferrite plate 16 formed in a convex shape swelling smoothly toward the center, and the permanent magnet 1 of the ferrite plate 16 is formed.
The surface facing the magnet 7 is formed in a concave shape that is smoothly depressed toward the center, so that the permanent magnet 17 and the ferrite plate 16 face each other at regular intervals. Further, the surface of the ferrite plate 16 facing the metal case 13 is formed in a convex shape bulging toward the center, and the thickness of the periphery of the ferrite plate is formed to be thinner than the center. Have been.

With the above configuration, the magnetic flux lines emitted from the permanent magnets 17 can pass vertically over the entire center conductor 14 as shown by arrows in FIG. This has the same effect as that of the first embodiment, and furthermore, the externally applied magnetic field is always applied from a fixed direction to the magnetic field generated by the microwave transmitted on the center conductor. , And the reverse loss can be further reduced. That is, the isolator according to the third embodiment can further improve irreversible characteristics.

According to the third embodiment shown in FIG.
A 00 MHz band lumped-constant type isolator was manufactured, and the distribution of the magnetic field intensity inside the ferrite plate 16 in the thickness direction and the isolator characteristics were evaluated. In this example, the ferrite plate 16 and the permanent magnet 17 are formed in a disk shape. However, in the present invention, the ferrite plate 71 and the permanent magnet 72 are not limited to the disk shape. The results are shown in FIGS. 13 and 14, respectively. As is clear from FIG. 13, also in the third embodiment, the intensity distribution of the magnetic field inside the ferrite plate 16 is substantially uniform. FIG. 14 shows that the isolator according to the third embodiment is excellent in both forward insertion loss and reverse loss. 13 and 14 show Comparative Example 3
What is shown as is the evaluation result of the isolator manufactured based on the configuration shown in the schematic sectional view of FIG. That is, the isolator of Comparative Example 3 shown in FIG.
Except for using a, the configuration is the same as that of the third embodiment.

In the third embodiment, the 900 MHz band lumped-constant type isolator has been described. However, it goes without saying that the same effect can be obtained with other frequency, distributed constant type, and circulators.

[0025]

As is apparent from the above description,
According to the nonreciprocal circuit device of the present invention, the peripheral portion of the ferrite plate is so arranged that the magnitude of the thickness direction component of the DC magnetic field applied inside the ferrite plate is substantially uniform over the entire ferrite plate. Is thinned, the ferrite plate can be magnetized uniformly, and a nonreciprocal circuit device having good nonreciprocal characteristics and a thin thickness can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an isolator according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of an isolator according to a modification of the first embodiment according to the present invention.

FIG. 3 is a schematic sectional view of an isolator according to a modification different from FIG. 2 of the first embodiment according to the present invention.

FIG. 4 is a schematic cross-sectional view of the isolator of Comparative Example 1.

FIG. 5 is a graph showing a thickness direction component magnetic field strength distribution of the ferrite plate in the isolator of the first embodiment.

FIG. 6 is a graph showing electrical characteristics of the isolator according to the first embodiment.

FIG. 7 is a schematic sectional view of a circulator according to a second embodiment of the present invention.

FIG. 8 is a schematic sectional view of a circulator of Comparative Example 2.

FIG. 9 is a graph showing the thickness direction component magnetic field strength distribution of the ferrite plate in the circulator of the second embodiment.

FIG. 10 is a graph showing electrical characteristics of the circulator according to the second embodiment.

FIG. 11 is a schematic sectional view of an isolator according to a third embodiment of the present invention.

FIG. 12 is a schematic sectional view of an isolator of Comparative Example 3.

FIG. 13 is a graph showing a magnetic field intensity distribution in a thickness direction of a ferrite plate in the isolator according to the third embodiment.

FIG. 14 is a graph showing electrical characteristics of the isolator according to the third embodiment.

FIG. 15 is an exploded perspective view of a conventional distributed constant circulator.

FIG. 16 is an exploded perspective view of a conventional lumped constant circulator.

FIG. 17 is a schematic view showing an example of a conventional example in which a magnetic field is uniformly applied to a ferrite plate.

FIG. 18 is a schematic view showing another example of a structure for applying a magnetic field uniformly to a ferrite plate in a conventional example.

FIG. 19 is a graph showing a thickness direction component distribution of a magnetic field intensity when a ferrite and a case are brought close to each other in a conventional example.

[Explanation of symbols]

11, 16, 71, 171, 181, 191 ... ferrite plate, 12, 17, 72, 172, 182, 192 ... permanent magnet, 13, 73, 173, 183, 201 ... metal case 14, 74, 174, 184 ... Center conductor, 15: support, 175, 185: ground plate.

Continued on the front page (72) Inventor Hiroyuki Hase 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Hiroshi Kagata 1006 Odaka Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A ferrite plate having a predetermined shape, a magnet provided to face the ferrite plate and applying a DC magnetic field to the ferrite plate, and a magnetic circuit including the ferrite plate and the permanent magnet. A non-reciprocal circuit device comprising: a ferrite plate, wherein the magnitude of a thickness direction component of the DC magnetic field applied inside the ferrite plate is substantially uniform over the entire ferrite plate. A non-reciprocal circuit device characterized in that the periphery of the device is thinned. 2. The non-reciprocal circuit device according to claim 1, wherein at least one of the upper surface and the lower surface of the ferrite plate is formed in a convex shape which swells smoothly toward the center. 3. A non-magnetic ferrite plate, wherein the other surface of the ferrite plate is provided to face the permanent magnet, and the ferrite plate has a concave surface facing the one surface of the ferrite plate. 3. The non-reciprocal circuit device according to claim 2, wherein the non-reciprocal circuit device is fixed to the case via a support made of a body. 4. The surface of the permanent magnet facing the ferrite plate is formed in a convex shape that smoothly swells toward the center, and the surface of the ferrite plate facing the permanent magnet faces the center. 2. The non-reciprocal circuit device according to claim 1, wherein the non-reciprocal circuit device is formed in a concave shape that is smoothly recessed.