JPH0537206A - Irreversible circuit element - Google Patents

Abstract

PURPOSE:To realize the irreversible circuit element in which a transmission loss at a high frequency UHF band is reduced, the ferrite is made small in diameter while securing an inductance of a center conductor and small sized light weight components are employed. CONSTITUTION:Three center conductors 10 are arranged so as to be in crossing at a prescribed angular interval in the electric insulation state while an insulation sheet 11 is interposed among them, a ferrite 9 is abutted with the crossing part and a DC magnetic field is applied to the ferrite to form the irreversible circuit element. Then a cross sectional shape of the center conductors 10 in a direction of the DC magnetic field is formed flat, main parts 10a of each center conductor 10 are arranged opposite to each other with the ferrite 9 having a 1st major side 9a and a 2nd major side 9b inbetween and one-ends of each main body 10a are connected integrally with a connection part 10b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reciprocal circuit device, such as an isolator or a circulator, which is used as a high frequency component in the UHF band, and particularly, it can reduce the transmission loss in the high frequency band and secure the inductance of the center conductor. While making ferrite smaller in diameter, parts are made smaller,
The present invention relates to a structure that can be reduced in weight.

[0002]

2. Description of the Related Art Generally, isolators and circulators used in the UHF band have a function of causing little attenuation in the signal transmission direction and increasing attenuation in the opposite direction. , It is used in mobile communication devices such as car phones. The isolators and circulators used in this mobile communication device are required to be small and lightweight for their application. Therefore, at present, lumped constants that can be made smaller and lighter than the distributed constant type are available. The mold is widely used. Conventionally, as such a lumped constant type circulator, there are a microstrip line type and a strip line type as shown in FIGS. 12 and 13. In this microstrip line type, as shown in FIGS. 12 (a) and 12 (b), a ground plate 51 is brought into contact with the lower surface of one ferrite 50, and three central conductors 52 are provided on the upper surface of the ferrite 50.
Is electrically insulated by interposing an insulating sheet 53, and
It is arranged so that it intersects every 120 degrees, and a DC magnetic field is applied to this intersection. Further, one end of each center conductor 52 is connected to the ground plate 51, and the other end is connected to the input / output port 55 via the matching circuit element 54. In addition, the above stripline type is
As shown in FIGS. 13 (a) and 13 (b), three center conductors 51
The pair of ferrites 56, 56 is brought into contact with the intersection of the above, and the ground plate 57 is brought into contact with the outer surface of each ferrite 56.

[0003]

By the way, the above UHF
Mobile communication devices used in the band, such as mobile phones, are under development to be further downsized, and accordingly, demands for downsizing and weight reduction of isolator and circulator are also increasing. In order to meet such requirements, it is effective to make the diameter of the ferrite as small as possible. However, in each of the conventional structures described above, if the diameter of the ferrite is reduced, it becomes difficult to secure the required inductance of the central conductor, and as a result, there is a problem that the electrical characteristics are deteriorated. In the case of the lumped constant type, this is not affected by the frequency even if the ferrite diameter is reduced, but in order to obtain the necessary electrical characteristics, the inductance value of the center conductor must be set large from the conditions of the matching circuit section. .. This inductance value is determined by the length of the center conductor, and this length is determined by the diameter value of ferrite. Therefore, the smaller the ferrite diameter, the shorter the effective length of the center conductor, and the smaller the inductance value. Here, in order to increase the inductance value, it is conceivable to narrow the electrode width of the central conductor, but this causes a problem that the Q of the central conductor decreases and the insertion loss of the isolator and the circulator increases. Therefore, at present, it is difficult to reduce the ferrite diameter.

The present invention has been made in view of the above-mentioned conventional circumstances. A nonreciprocal circuit that can meet the above-mentioned demands by reducing the diameter of ferrite to reduce the size and weight of components without deteriorating the electrical characteristics. The purpose is to provide a device.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention is constructed so that ferrite is brought into contact with the intersecting portions of a plurality of center conductors arranged in an electrically insulated state and intersecting each other at a predetermined angular interval. In the non-reciprocal circuit device, the central conductor has a flat cross-sectional shape in the direction of the DC magnetic field, and is a strip plate arranged on both surfaces of the first and second main surfaces of the ferrite. It is characterized in that one end portions of the respective center conductors on the first and second main surfaces are electrically connected to each other at the side portions of the ferrite.

Here, the flat section in the present invention may be, for example, a rectangle or an ellipse. In this case, w / t between the thickness t and the width w of the center conductor
It is desirable that the ratio be 10 or more. This is because a high Q can be obtained while maintaining the required inductance. Further, disposing the center conductor on both main surfaces of the ferrite and connecting one ends to each other means that the center conductor is wound around the ferrite. In this case, one winding or multiple windings are performed. Things are included. The specific structure of the central conductor is, for example, a structure in which a strip-shaped metal plate is bent into a substantially U-shape and attached to a ferrite, or the central conductor is formed on a substrate, and the pair of substrates is formed into a ferrite. It is possible to adopt a structure in which both ends of the central conductors are brought into contact with each other and the end portions of the central conductors are connected to each other by a conductor piece, and further, a structure in which the central conductor is directly coated by printing, etching, or plating on the ferrite.

The central conductor has a flat cross section,
For example, when used in the UHF band of 250 MHz or more, the transmission loss of the high frequency current flowing through the conductor is reduced, and the size of the element is prevented from increasing. Since the resistance value of the unit length of the transmission line is inversely proportional to the cross-sectional area of the part where the current flows in the conductor, for example, when using a central conductor made of a wire with a circular cross section, to prevent an increase in transmission loss. The diameter will be increased. However, although there is no problem at a low frequency such as the VHF band of 250 MHz or less, when the frequency is higher than this, a problem occurs that high frequency current is concentrated on the surface portion of the conductor due to the so-called skin effect. Therefore,
When used at a high frequency such as the UHF band, even if the diameter is increased, the effect of reducing the transmission loss is low because only the portion where no current flows increases due to the skin effect. Moreover, when the central conductor made of the wire having the circular cross section is crossed on the ferrite, the crossing part rises and becomes higher, and the whole part becomes larger and the space between the crossing part and the case becomes smaller, resulting in electromagnetic interference. There is also a problem that the field characteristics deteriorate. Further, there is a large difference in position between the one overlaid and the one underneath, which leads to a difference in electrical characteristics, and as a result, the symmetry of electrical characteristics between the ports deteriorates.

[0008]

According to the nonreciprocal circuit device of the present invention, since the flat center conductors are arranged on the first and second main surfaces of the ferrite and one ends of the center conductors are connected to each other, the conventional ferrite The effective length of the central conductor can be made longer than that of the structure in which the central conductor is provided only on one surface, and therefore the ferrite can be made small in diameter while sufficiently securing the inductance value of the central conductor. Further, since the cross-sectional shape of the center conductor is made flat, for example, when used for high frequencies of 250 MHz or more, there are few portions where high-frequency current does not flow, and therefore transmission loss of the transmission loss is higher than that when using the center conductor with the circular cross section. Greatly reduces the effect.
Moreover, since the flat shape is adopted, the height of the intersecting portion is low, and it is possible to prevent the element from becoming large and the electromagnetic field characteristics from being deteriorated as in the case of the center conductor having a circular cross section.
The weight can be reduced and the above-mentioned demand can be met.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are views for explaining a non-reciprocal circuit device according to a first embodiment of the present invention. In the present embodiment, a case of application to a lumped constant type isolator will be described as an example. In the figure, 1 is an isolator to which the structure of this embodiment is applied. In this isolator 1, a permanent magnet 3 is adhered on a bottom surface 2a of a lower case 2 made of a magnetic metal, a dielectric substrate 4 is arranged above the permanent magnet 3, and a central portion of the dielectric substrate 4 is arranged. The ferrite assembly 5 is inserted into the hole 4a formed in the lower case 2 and the upper case 6 made of magnetic metal is attached to the lower case 2 to form a magnetic circuit. It is configured to apply a bias magnetic field.

Grounding pieces 2b are integrally formed on the left and right edges of the lower case 2, and hook-shaped side walls 2c are respectively provided upright at the four corners. The dielectric substrate 4 is placed on the upper surface of the side wall portion 2c.
There is a slight gap between the and the permanent magnet 3.
A ground electrode 4b is formed on the entire lower surface of the dielectric substrate 4, and the ground electrode 4a is soldered to the side wall portion 2c.

Further, three matching circuit capacitor electrodes C1, C2 are provided around the hole 4a on the upper surface of the dielectric substrate 4.
C3 is formed, and these are formed by printing Ag in a thick film shape. These two capacitor electrodes C
One end of the input / output terminals 7 and 7 is soldered to the terminals 1 and C2, and the other end of the input / output terminals 7 and 7 project outward from the opening of the upper case 6. Further, the remaining capacitor electrode C3
Is connected to one end of a termination resistance film R formed by thick film printing, and the other end of the resistance film R is connected to the through-hole electrode 8
It is connected to the earth electrode 4b through.

The ferrite assembly 5 faces the upper surface (first main surface) 9a and the lower surface (second main surface) 9b of the disk-shaped ferrite 9 with the ferrite 9 interposed therebetween.
The central conductor 10 of the book is attached and configured. Each of the central conductors 10 is formed by bending a strip-shaped metal plate into a substantially U shape, and is composed of a main body 10a for exciting electric power and a connecting portion 10b for connecting one end of the main body 10a. ing. Each of the main body portions 10a is formed on both sides 9 of the ferrite 9.
The connecting portions 10b are in contact with the side surfaces of the ferrite 9 and extend in the diametrical directions of a and 9b, and are arranged in a cross shape with an insulating sheet 11 at an angle of 120 degrees. Further, the other end 10c of each main body 10a projects outward from the ferrite 9, and each other end 10c on the lower surface 9b side of the ferrite 9 is connected to the ground electrode 4b of the dielectric substrate 4 by soldering. Each of the other end portions 10c on the upper surface 9a side has the above-mentioned respective capacitor electrodes C1, C2, C3.
It is soldered to. Here, as shown in FIG. 5A, the cross-sectional shape of the permanent magnet 3 in the direction of the DC magnetic field, that is, the direction orthogonal to the longitudinal direction of each central conductor 10 is rectangular, and the thickness t thereof is t. And the w / t ratio of width w
It is set to 10 or more.

Next, the function and effect of this embodiment will be described. The lumped-constant type isolator 1 of the present embodiment is, for example, 25
It is used in the transmission circuit section of car phones and mobile phones used in the UHF band of 0 to 900 MHZ and has the function of preventing backflow of the transmission output. Further, according to the present embodiment, since the cross-sectional shape of the central conductor 10 is rectangular and the w / t ratio thereof is 10 or more, it is possible to obtain a high Q value while securing a necessary inductance value. In addition, it is possible to reduce the transmission loss when used in the high frequency of the UHF band. Further, in this embodiment, the central conductor 10 is arranged such that the body portion 10a is located on both sides 9a and 9b of the ferrite 9 and the body portion 10a is
Since one ends of the main body 10a are integrally connected by the connecting portion 10b, the effective length of the main body portion 10a that abuts on the ferrite 9 can be increased, and the ferrite value can be reduced without deteriorating the inductance value of the center conductor. The diameter can be reduced. As a result, the size of the isolator 1 as a whole can be reduced and the weight thereof can be reduced, and the amount of the ferrite material used can be reduced, so that the cost can be reduced accordingly. By the way, the ferrite assembly 5 of the structure of this embodiment and the stripline type of the conventional structure (see FIG. 13) are adopted, and the I.S. L. Comparing the sizes of ferrites with the same insertion loss (insertion loss) value, the conventional structure required a ferrite diameter of 4.0mmφ and a thickness of 0.6mm. On the other hand, in the case of the structure of this example, the diameter of the ferrite is 2.5 mm φ, the thickness is 0.3 mm, and the diameter is about 1/2,
The total thickness was about 1/4. It should be noted that the same I.D. L. No value was obtained.

Now, a test for finding the optimum value of the w / t ratio of the central conductor will be described. In this test,
As shown in Fig.8, a conductor plate with a length of l8.5mm and a thickness of t0.035mm is adopted. With the length l and the thickness t fixed, only the width w of the conductor plate is changed and the w / t ratio is changed. The inductance value and the Q value were measured when the value was changed. The frequency is 38
I went at 0MHZ. In the figure, the solid line shows the Q value and the broken line shows the L value.
As is clear from the figure, as the width w of the conductor plate is increased, that is, as the w / t ratio increases, the inductance value decreases. On the other hand, the Q value increases as the w / t ratio increases. From this, it is desirable that the w / t ratio is 10 or more in order to obtain a high Q value while securing the required inductance value.

In the first embodiment, the case where the central conductor 10 has a rectangular cross section has been described as an example.
The central conductor of the present invention is not limited to this, and may have a trapezoidal shape, a rhombic shape, or an elliptical shape as shown in FIGS. 5 (b) to 5 (d). Any shape can be adopted as long as it is 10 or more.

In the first embodiment, the case where the central conductor 10 is wound once on both surfaces 9a and 9b of the ferrite 9 has been described as an example, but the central conductor of the present invention may be wound plural times. For example, the structure shown in FIG. 6 is an example in which the strip-shaped center conductor 15 is wound around the ferrite 9 twice, and two main body portions 15a are formed in the diametrical direction of the upper and lower surfaces 9a and 9b of the ferrite 9. They are arranged in parallel, and one end portions of the respective main body portions 15a are integrally connected by connecting portions 15b and 15b '. In addition, FIG. 7 shows an example in which the center conductor 16 is wound 1.5 times around the ferrite 9, and two body portions 16a are arranged on the upper surface 9a of the ferrite 9 and one is formed on the lower surface 9b. The main body portion 16a is provided, and one end portions of the upper and lower body portions 16a are integrally connected by a connecting portion 16b. According to each of the above-mentioned structures, the central conductor is wound by 1.5 to 2 turns to be long, so that the diameter of the ferrite can be further reduced.

Furthermore, in the first embodiment, the case where the strip-shaped metal plate is bent to form the central conductor has been described as an example, but the central conductor of the present invention is not limited to this, and for example, screen printing, It may be formed directly on both sides of the ferrite by photoetching, electroless plating or the like, or the center conductor may be formed on an insulating substrate and the pair of substrates may be brought into contact with the ferrite. 8 and 9 (a)
9A and 9B show the second and third embodiments in which the central conductor is formed by screen printing, and FIGS.
Shows the fourth and fifth embodiments in which the central conductor is formed on the insulating substrate. In the second embodiment shown in FIG. 8, the upper surface 9 of the ferrite 9 is
a, a main body 2 having two parallel lines by printing electrodes on the lower surface 9b
0a is formed, and an insulating member is printed on the upper surface of the main body portion 20a of both surfaces 9a and 9b of the ferrite 9 to form the insulating film 21. A second main body 20a is formed on the upper surface of the insulating film 21 so as to intersect with the main body 20a, the insulating film 21 is formed on the upper surface of the second main body 20a, and a third main body 20 is formed on the upper surface of the insulating film 21. To form. Then, a side surface electrode is printed on the peripheral side surface 9c of the ferrite 9 to form a connecting portion 20b, and the connecting portion 20b connects one end portions of the respective main body portions 20a. As a result, both sides 9a, 9 of the ferrite 9 are
Three main body portions 20a intersecting with each other in an electrically insulating state are formed in b, and one end portion of each main body portion 20a is connected to the connecting portion 20.
The central conductor 20 connected by b is comprised. According to the above-mentioned structure, the electrodes are directly printed on the ferrite 9 and the central conductor 2
Since 0 is formed, in this case, the assembling work can be simplified, the productivity can be improved, and the component cost can be further reduced.

In the third embodiment shown in FIG. 9 (a), a part 22 of the center conductor 22 is formed on both sides 9a, 9b of the ferrite 9.
a is formed, an insulating film 23 is formed on the upper surface of the a, and the remaining portion 22b of the center conductor 22 is formed on the upper surfaces of the insulating films 23 on both surfaces 9a and 9b of the ferrite 9.
The inner end portions of 2a and 22b are connected to each other through the through-hole electrode 24 formed on the insulating film 23, and the one end portions of the portions 22a on both sides are connected to the peripheral side surface 9c of the ferrite 9. It is an example configured by connecting with 22c. Furthermore, the modification of the third embodiment shown in FIG.
A part 25a of the parallel central conductor 25 is formed on both surfaces 9a, 9b of the ferrite 9, and the remaining part 25b is formed via the insulating film 23.
In this example, the inner ends of 5b are connected to each other by the through-hole electrode 26. According to each of the above structures, the number of times of printing the center conductors 22 and 25 and the insulating film 23 can be reduced as compared with the structure of FIG.
Manufacturing cost can be reduced.

In the fourth embodiment shown in FIG. 10, the three central conductors 30 made of metal pieces formed in a frame shape are connected to the first conductor portion 3.
0a and the second conductor portion 30b are formed separately, and the insulating substrate 31
The first conductor portion 30a is arranged on one main surface, and the second conductor portion 30b is arranged on the upper surface of the first conductor portion 30a with the insulating sheet 32 interposed therebetween.
The leading end portions of the above are connected by penetrating the insulating sheet 32. Further, the center conductors 30 of the pair of insulating substrates 31 are brought into contact with both surfaces 9a, 9b of the ferrite 9, and the outer end portions of the first conductor portions 30a of the insulating substrates 31 are arranged on the sides of the ferrite 9. The connection pins 33 are connected to each other.

In the fifth embodiment shown in FIG. 11, a part 36a of the center conductor 36 is formed on one main surface of the insulating substrate 35, and the remaining part 36b of the center conductor 36 is formed on the other main surface. , 36a and 36b are connected by a through-hole electrode 37 formed on the insulating substrate 35, the pair of insulating substrates 35 are brought into contact with both surfaces 9a and 9b of the ferrite 9, and the central conductors 36 of both insulating substrates 35 are connected. Outer edge 3
Connection pin 3 with 6c placed on the side of ferrite 9
8 are connected.

[0021]

As described above, according to the nonreciprocal circuit device of the present invention, the central conductor has a flat cross-sectional shape and the strips are arranged on both the first and second main surfaces of the ferrite. Since one end of each of the center conductors is electrically connected to each other, transmission loss can be reduced without deteriorating electromagnetic field characteristics in the UHF band, and ferrite can be downsized to reduce the size and weight of the entire component. There is an effect that can be converted.

[Brief description of drawings]

FIG. 1 is a perspective view showing a ferrite assembly for explaining an isolator according to a first exemplary embodiment of the present invention.

FIG. 2 is a side view of the ferrite assembly according to the first embodiment.

FIG. 3 is an exploded perspective view of the isolator of the first embodiment.

FIG. 4 is a characteristic diagram showing test results for finding the w / t ratio of the central conductor of the first embodiment.

FIG. 5 is a view showing various sectional shapes of the central conductor of the first embodiment.

FIG. 6 is a perspective view showing a state in which a central conductor according to another example of the first embodiment is wound twice.

FIG. 7 shows a center conductor according to another example of the first embodiment of 1.5.
It is a perspective view of the state which rolled.

FIG. 8 is a perspective view showing a ferrite assembly having a central conductor printed thereon according to a second embodiment of the present invention.

FIG. 9 is a perspective view showing a ferrite assembly having a center conductor printed thereon according to a third embodiment of the present invention.

FIG. 10 is an exploded perspective view of a ferrite assembly in which a central conductor according to a fourth embodiment of the present invention is formed on an insulating substrate.

FIG. 11 is an exploded perspective view of a ferrite assembly in which a central conductor according to a fifth embodiment of the present invention is formed on an insulating substrate.

FIG. 12 is a view showing a structure of a center conductor by a conventional microstrip line tamper.

FIG. 13 is a view showing a structure of a center conductor by a conventional stripline tamper.

[Explanation of symbols]

1 Isolator (non-reciprocal circuit element) 9 Ferrite 9a Upper surface (first main surface) 9b Lower surface (second main surface) 10, 15, 16, 20, 22, 25, 30, 36 Center conductor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takashi Kawanami 2-26-10 Tenjin, Nagaokakyo, Kyoto Prefecture Murata Manufacturing Co., Ltd. (72) Inventor Akinori Den, 2-26-10 Tenjin, Nagaokakyo, Kyoto Murata Manufacturing

Claims (1)

Claim: What is claimed is: 1. A ferrite is brought into contact with the intersecting portions of a plurality of central conductors arranged in an electrically insulated state so as to intersect at a predetermined angular interval, and a DC magnetic field is applied. In the non-reciprocal circuit device configured as described above, the central conductor has a flat cross-sectional shape in the direction of the DC magnetic field, and is a strip plate shape arranged on both the first main surface and the second main surface of the ferrite. And a non-reciprocal circuit device characterized in that one end portions of the respective central conductors on the first and second main surfaces are electrically connected to each other at a side portion of the ferrite.