JP2002314308A - Two-terminal pair isolator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-terminal pair isolator that bears a low insertion loss and has a wide bandwidth for insertion loss. SOLUTION: In this two-terminal pair isolator in which first and second center conductors are arranged adjacently to ferrite sheets so as to cross each other in an electrically insulative state, a static magnetic field is applied to the ferrite sheets by a magnet, one ends of the first and second center conductors become first and second input-output terminals respectively, the other ends are connected to a common part, a first matching capacitor is connected between the first input-output terminal and the common part, a second matching capacitor is connected between the second input-output terminal and the common part, and a resistive element is connected between the first and second input-output terminals, at least one of the ferrite sheets is rectangular in shape, the respective first and second central conductors are parallel to respective sides that make an angle of the rectangular ferrite sheet, and central parts of the respective central conductors are divided into three or more parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of high frequency isolators, and more particularly, to the field of two-terminal isolators having a wideband reverse loss characteristic.

[0002]

2. Description of the Related Art As a technical situation of a high frequency isolator at present, one terminal of a three-terminal pair type circulator is generally terminated with a matching impedance.
The junction type circulator is classified into two types, that is, a distributed constant type circulator and a lumped constant type circulator. The circulator has an irreversible electrical characteristic and its basic structure is a structure in which a magnetic field is applied vertically to a ferrite thin plate and a conductor is close to the periphery of the ferrite thin plate. The former distributed constant type is the one where the size of the ferrite thin plate in the isolator element is 1/4 or more of the wavelength of the high frequency wave transmitted therethrough, and the latter lumped constant type is 1 /
In the case of 8 or less, they are properly used. Therefore,
The lumped parameter type is more suitable for miniaturization.

FIG. 11 is a schematic structural view and schematic view of a case where a matching impedance (resistance element R) is connected to one terminal pair of a lumped constant type circulator currently used in a cellular phone or the like to realize an isolator. FIG. The ferrite thin plate is made of a garnet type ferrite G, and three center conductors L1, L2, L3 are arranged at an angle of 120 degrees on this upper surface. One end of each central conductor is an input / output terminal of a terminal pair, and the other end is connected to a common part GR serving as a ground conductor. The matching capacitors C1, C2, and C3 are connected in parallel between one ends of the center conductors L1, L2, and L3 and the common part GR, respectively. Further, in order to realize an isolator, an energy absorbing resistance element R is mounted between the terminal pair and the common part GR. Although a permanent magnet is loaded so that a substantially perpendicular static magnetic field is applied to the main surface of the ferrite thin plate G, it is omitted in the drawing. By carefully adjusting the direction and strength of the static magnetic field, and the size of the center conductors L1, L2, L3 and the matching capacitors C1, C2, C3, the structure shown in FIG. 11 has the desired frequency (hereinafter referred to as the center frequency). It operates as a circulator at fo. The high frequency input from the terminal pair is transmitted to the terminal pair, and the high frequency input from the terminal pair is transmitted to the terminal pair with a small loss. When the resistance element R is connected to the terminal pair, almost all energy is absorbed there, and a state in which high frequency hardly propagates from the terminal pair to the terminal pair is realized.
That is, it is possible to realize an isolator that is an element that supports propagation in only one direction and blocks propagation in the opposite direction.

The structure shown in FIG. 11 has the advantage that the insertion loss is small and the bandwidth is wide, but has the disadvantage that the bandwidth of the reverse loss is narrow. That is, since the three sets of center conductors intersect at an angle of 120 degrees, at a frequency slightly higher than the center frequency fo, the coupling of the center conductors cannot be ignored, and the second transmission loss at a high frequency of about 1.4 fo (S. Takeda; 1999 IEEE MTT-S Digest, pp1361
-1364 (WEF3-1)), that is, the attenuation of the reverse loss is degraded to about 5 dB. Under the influence of this, there is a disadvantage that the attenuation of 2fo and 3fo cannot be made so large.

On the other hand, a two-terminal pair isolator as shown in FIG. 10 (JP-A-52-134349, JP-A-53-129)
No. 561) has two center conductors L1 and L2 and they are perpendicular to each other, so that even if the correct isolator operation cannot be established away from the vicinity of the center frequency, a high attenuation can be obtained. It was pointed out that there was an advantage. In this structure, the matching capacitors C1 and C2 are connected to the center conductors L1 and L2.
Are connected in parallel between one end of the common line and the common portion GR. The major difference is that the two terminals of the energy absorbing resistor R are
That is, they are connected to one ends of the center conductors L1 and L2, respectively. The other ends of the center conductors L1 and L2 are connected to a common part GR that is a ground conductor. This structure is characterized in that the number of central conductors is one and the number of matching capacitors is one, as can be seen from the structure of FIG. 11, which is extremely convenient for miniaturization and thinning of an isolator. is there.

[0006]

However, the structure shown in FIG. 10 has not been put into practical use until now. The reason is that although the bandwidth of the reverse loss is wide, the bandwidth of the insertion loss is narrow. Furthermore, the value of the insertion loss itself is shown in FIG.
That is, it is slightly larger than the structure of the circulator of three terminals. As an example, to widen the bandwidth, it is conceivable to weaken the static magnetic field,
In this case, the magnetic loss increases and the insertion loss increases. Another reason is that, like a three-terminal circulator, its operating principle has not been studied so much in circuit theory. The inventors of the present invention have developed a unique circuit simulator capable of analyzing the circuit of FIG. 10, and have been able to obtain various basic knowledge based on the circuit simulator. Hereinafter, the operation principle of FIG. 10 will be briefly described based on the circuit analysis.

[0007] The high frequency wave from the terminal pair causes a current to flow through the center conductor L1 to excite the ferrite thin plate G. The ferrite thin plate G is a permanent magnet that is magnetized in the direction of its main surface, and generates a high-frequency magnetic field component that is coupled to the orthogonal center conductor L2. This is due to the ferromagnetic resonance effect of ferrite in the microwave band. Without this effect, no energy would propagate to the center conductor L2. The matching capacitors C1 and C2 are paired with the center conductors L1 and L2, respectively, to form a parallel resonance circuit that resonates at the center frequency fo. What should be noted here is the phase change when propagating. That is, when energy is transmitted from the terminal pair to the terminal pair, the phase difference is 360 degrees, and if the amplitude is the same between the input and the output, no current flows through the resistance element R. Conversely, when energy is transmitted from the terminal pair to the terminal pair, the phase difference is exactly 180 degrees. At this time, a large current flows through the energy absorption resistance element R, and energy is consumed by the resistance element R. That is, energy is not easily transmitted from the terminal pair to the terminal pair.

FIG. 1 shows the relationship between a parallel two-wire center conductor and a disk-shaped ferrite thin plate according to the prior art. FIG. 1A is a plan view showing an arrangement relationship between a first ferrite thin plate G1 and two parallel two-line center conductors L1 and L2. Here, the second ferrite thin plate G2 is omitted. FIG. 1B shows the center conductors L1 and L2 between the first ferrite sheet G1 and the second ferrite sheet G2.
FIG. 4 is a cross-sectional view of substantially the center when is disposed. One end of the first center conductor L1 is connected to a common part GR which is a ground conductor. The second center conductor having substantially the same shape is disposed on the first center conductor via an insulating film (omitted in the drawing) so that its major axis is perpendicular to the second center conductor. Connected. The other ends of the center conductors L1 and L2 serve as input / output terminals as they are. The second ferrite thin plate G2 is arranged closely to the second parallel two-line center conductor L2.

FIG. 2 (a) shows the relationship between a parallel two-wire center conductor and a ferrite thin plate, which is another embodiment of the prior art.
The difference from FIG. 1 is that the shape of the first ferrite thin plate G1 is rectangular. FIG. 2B is a plan view of the second ferrite thin plate G2 closely contacted on the second center conductor L2. Since the two parallel two-line center conductors are orthogonal,
The coupling of the center conductors L1 and L2 can be somewhat improved in the geometric symmetry as compared with the embodiment of FIG.

FIG. 3 shows two parallel two-line center conductors L1, L2 which are electrically insulated from each other and cross each other in the structure of FIG.
Are not simply overlapped but are knitted in a basket shape. With such a configuration, two more central conductors
The coupling between L1 and L2 can be improved. Center conductor L1, L2
It has been clarified by a circuit simulator developed in-house that in a two-port isolator in which is orthogonal to each other, poor coupling appears directly as degradation of insertion loss.
It cannot be said that the conventional structures shown in FIGS. 2 and 3 efficiently couple the two center conductors L1 and L2 over the entire rectangular ferrite thin plates G1 and G2. In particular, there is a disadvantage that the peripheral portion of the ferrite thin plate cannot be well connected to the connection between the two center conductors.

As described above in the prior art embodiment, the conventional two-port isolator has a disadvantage that although the reverse loss bandwidth is wide, the insertion loss is large and the bandwidth is narrow. SUMMARY OF THE INVENTION The present invention has been made in view of the situation of the related art, and has as its object to provide a two-port isolator having a small insertion loss and a wide bandwidth of the insertion loss.

[0012]

According to a first aspect of the present invention, a first and a second center conductor are arranged close to a ferrite thin plate so as to intersect each other in an electrically insulated state. A static magnetic field is applied by a magnet, and the first, second
One ends of the center conductor are first and second input / output terminals, respectively, and the other ends are connected to a common part, and a first matching capacitor is connected between the first input / output terminal and the common part. A second input / output terminal and the common unit
Wherein the at least one ferrite thin plate has a rectangular shape, wherein the shape of the at least one ferrite thin plate is rectangular. A pair of two terminals, wherein each of the second center conductors is parallel to each of the sides forming an angle of the rectangular ferrite thin plate, and the center portion of each center conductor is divided into three or more. It is an isolator.

According to a second aspect of the present invention, the first and second center conductors are arranged close to a ferrite thin plate so as to intersect each other in an electrically insulated state, and the ferrite laminate is made of a static magnetic field by a magnet. Is applied, one ends of the first and second center conductors become first and second input / output terminals, respectively, and the other ends are connected to a common unit, and the first input / output terminal and the common unit are connected to each other. A first matching capacitor is connected therebetween, a second matching capacitor is connected between the second input / output terminal and the common portion, and a first matching capacitor is connected between the first and second input / output terminals. In a two-terminal isolator having a resistance element connected thereto, the first and second center conductors are arranged between a plurality of ferrite laminates fired simultaneously, and at least one ferrite thin plate has a rectangular shape. Wherein each of the first and second center conductors is Serial and parallel to each edge forming an angle of rectangular ferrite sheet, and a two-terminal-pair isolator, wherein a central portion of each central conductor is divided into three or more.

According to a third aspect of the present invention, in the first or second aspect, the overall width of the center conductor is at least half the length of one side of the rectangular ferrite thin plate. It is an isolator. According to a fourth aspect of the present invention, in the first to third aspects, the ferrite thin plate, the center conductor, the matching capacitor, and the resistance element are housed in a rectangular case, and the resistance element is one of the rectangular cases. This is a two-terminal pair isolator that is included in close proximity to only two corners. The invention of claim 5 is
5. The method according to claim 1, wherein the ferrite thin plate, the center conductor, the matching capacitor, and the resistance element are housed in a rectangular case, and the matching capacitor is a plate capacitor, and a long side of the plate capacitor is A two-terminal pair isolator characterized by being arranged in parallel to a side of a rectangular ferrite thin plate. According to a sixth aspect of the present invention, in the first to fifth aspects, the first and second center conductors which intersect each other in an electrically insulated state are closely contacted between two first and second ferrite thin plates. Wherein a static magnetic field is applied to the ferrite thin plate from one side by a permanent magnet, wherein the saturation magnetization of the second ferrite thin plate is larger than the saturation magnetization of the first ferrite thin plate. It is a terminal pair isolator. The invention of claim 7 is the two-terminal pair isolator according to any one of claims 1 to 6, wherein the common portion is a ground conductor.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 4 shows one embodiment of the present invention. As shown in FIG. 4A, unlike the prior art, on the first rectangular ferrite thin plate G1,
A first parallel six-line center conductor L1 is disposed, and a substantially parallel second parallel six-line center conductor L2 is in close contact therewith. FIG. 4B is a plan view of a second ferrite thin plate G2 closely arranged on the second parallel six-wire center conductor G1. Further, in the present embodiment, unlike the conventional parallel two-wire center conductor, the parallel six-wire center conductor is used, so that the high-frequency magnetic field generated by the current flowing through the first center conductor is generated by the first and second ferrites. Energy is transmitted to the second parallel six-wire center conductor efficiently through the ferrite thin plate, spread evenly over the entire flat surface of the thin plate. Such a configuration is realized only because the shape of the ferrite thin plate is rectangular.
As described above, the main reason for the large insertion loss of the two-terminal isolator in the prior art is that it occurs because the coupling between the first center conductor L1 and the second center conductor L2 is not perfect. It was found by examination on circuit theory. This connection is only possible via the ferrite sheet, and therefore a direct consequence of the poor connection between the center conductor and the ferrite sheet. The gist of the present invention is based on the view that improving this coupling is essential for reducing insertion loss. This also results in a wider insertion loss bandwidth.

FIG. 4, which is the main feature of the present invention, will be described while comparing FIG. 2 of the prior art. That is, in the conventional parallel two-wire center conductor, only the vicinity of the center of the rectangular ferrite thin plate can be excited at a high frequency, and the coupling of the two center conductors is concentrated only in the center part. On the other hand, in the parallel 6-wire center conductor of FIG. 4 of the present invention, it is possible to excite the high frequency up to the peripheral portion of the ferrite thin plate, and the coupling between the first and second center conductors L1 and L2 is rectangular. It can be extended to the whole ferrite sheet. Comparing this with the overall width W of the center conductor and the length S of one side of the rectangular ferrite, W / S is 1/3 in the conventional technology.
To 2/5, whereas in the embodiment of the present invention, W / S is
It is easily possible to make it 1/2 or more. Incidentally, in the embodiment of the present invention shown in FIG. 4, the W / S was approximately 0.9. However, the effect of the present invention is not limited to the parallel six-wire center conductor of FIG. 4 but also increases as the number of conductors increases compared to the conventional two center conductors of FIG. It is stated in claim 1. Two orthogonal center conductors
L1 and L2 need to be combined with the ferrite sheet through the presence of each other. To facilitate this, it is necessary to optimize the width ratio between the six parallel lines and the five window portions in FIG. That is, to reduce the loss due to electrical conduction,
The width of the six parallel element lines is preferably wide, but if it is too wide, the shielding effect is promoted by each other, and the coupling with the far ferrite thin plate is weakened. In addition, the line capacitance between the two center conductors increases as a secondary effect, which has an adverse effect. Conversely, when the window portion is widened, although the coupling is improved, the width of the line becomes thinner and the electric conduction loss increases, which is not preferable. In general, it is better to use a window whose width is slightly wider than the width of each parallel element line.

FIG. 5 is an assembly view in which a ferrite thin plate, a center conductor, a resistance element, and a matching capacitor according to another embodiment of the present invention are incorporated in a rectangular case SH. Thereby, the effect of the present invention is further clarified. The rectangular ferrite thin plate G1 is slightly shifted to the lower right side of the rectangular case SH. This creates a space on the left side of the case, above the case, and in the upper left corner of the case. A resistance element R is inserted in the upper left corner, and is arranged below the input / output terminals L1 and L2 in the direction perpendicular to the plane of the paper. In addition, the long side of the rectangular matching capacitor is parallel to and close to each side of the ferrite thin plate. As shown in FIG. 5, it can be seen that there is almost no gap, and an extremely efficient mounting with a high space factor is realized. As described above, according to the present embodiment, in the 7-mm square isolator of 1000 MHz, the insertion loss of 0.68 dB in the conventional technology can be realized to 0.4 dB.

FIG. 6 is an assembly view of a ferrite thin plate and a center conductor according to another embodiment of the present invention. Rather than simply overlapping the two center conductors L1 and L2, this is a method in which the two center conductors are knitted like a cage as shown in FIG.

FIG. 7 is a sectional assembly view of a magnetic circuit according to another embodiment of the present invention. That is, this is a case where two rectangular ferrite thin plates G1 and G2 are housed in a magnetic seal case SH in which one permanent magnet MAG is inscribed. The first ferrite thin plate G1 is disposed below the shield case SH, and the second ferrite thin plate G2 is disposed on the permanent magnet MAG side. To further improve the coupling between the parallel six-wire center conductors L1 and L2, it is necessary to keep the static magnetic field inside the ferrite thin plate as uniform as possible. In the magnetic circuit of FIG. 7, since there is one permanent magnet,
A strong magnetic field acts on the second ferrite thin plate G2 close to the permanent magnet, and the first ferrite thin plate G1 has a relatively weak magnetic field. In order to further enhance the effects of the present invention, it is desirable to reduce this non-uniformity as much as possible. As a method of improving this, it has been found that it is effective to make the saturation magnetization of the second ferrite thin plate G2 larger than that of the first ferrite thin plate G1. The second ferrite thin plate G2 close to the permanent magnet MAG has a large demagnetizing field due to a large saturation magnetization, and its magnetic field strength is weakened even when placed under a strong external magnetic field. On the other hand, for the first ferrite sheet G1 farther from the permanent magnet MAG, the second ferrite sheet G2 is equivalent to the approach of a magnetic pole having a large saturation magnetization, and the external magnetic field is considered to be strong. is there. From this, the requirement of claim 5 of the present invention was derived.

FIG. 8 (a) is a perspective view showing another embodiment of the present invention, in which first and second center conductors are embedded in a co-fired ferrite laminate G. Each center conductor is represented by a dotted line. FIG. 8B is a perspective view of the above. One ends L1 and L2 of the center conductor connected to the input / output terminals protrude from the upper surface of the ferrite laminate. In this embodiment, the electrodes with the embedded surface electrodes are connected through side surfaces. Similarly, the terminal GR connected to the ground conductor appears on the lower surface of the laminate, and is connected to the other end of the center conductor by the side electrode of the ferrite laminate.

FIG. 9 is an expanded sheet of each element of the ferrite laminate. The bottom G11 sheet is relatively thick, and the ground conductor electrode GR is printed on the back surface. The upper sheet G12 is relatively thin, on which a first parallel six-line center conductor L1 is printed in parallel with the lateral side of the rectangular ferrite laminate. The sheet G21 thereon is rather thin, on which a second parallel six-line center conductor L2 is printed parallel to the vertical sides of the rectangular ferrite laminate.
The top sheet is relatively thick, and external electrodes L1 and L2 connected to the input / output terminals are printed thereon. The above sheet is a state in which ferrite powder is solidified with a binder. After pressing the four laminated bodies, the binder is burned by firing at a high temperature, so that the first and second central conductors are formed. A sintered body of the embedded ferrite laminate can be obtained. Generally, each sheet G11, G12, G21, G22
Although ferrite materials having the same composition are used, it is clear that increasing the saturation magnetization of G22 close to the permanent magnet is more effective as described in the embodiment of FIG. Further, since the sheet G21 functions as a magnetic shield for the first central conductor L2, the thinner the better, the better. However, if the sheet G21 is too thin, an undesired phenomenon that the wire winding capacity is increased also occurs. In this case, conversely, it is effective to lower the saturation magnetization more than G11, G12, and G22 so that the magnetic shield effect does not increase even with a certain thickness. Also, as a method of connecting the external electrode and the internal electrode, only the case of the side electrode applied in a later step has been described, but a through-hole method capable of connecting in the process of printing and laminating is also possible. In particular, the side-surface through-hole method penetrating only one side in the vertical direction is effective in the configuration of FIG.

[0022]

As described above, according to the two-terminal isolator according to the first aspect of the present invention, the first and second center conductors are close to the ferrite thin plate so as to cross each other in an electrically insulated state. And a static magnetic field is applied to the ferrite element by a permanent magnet. One end of each of the first and second center conductors becomes a first and second input / output terminal, and the other end is connected to a common unit. A first matching capacitor is connected between the first input / output terminal and the common unit, a second matching capacitor is connected between the second input / output terminal and the common unit, In a configuration in which a resistance element is connected between the first and second input / output terminals, the shape of the at least one ferrite thin plate is rectangular, and each of the first and second center conductors is rectangular. Each side of the ferrite thin plate at an angle Since they are parallel and the central part of each central conductor is divided into three or more, the coupling between the first central conductor and the second central conductor can be strengthened, and low insertion loss and wide band can be realized simultaneously. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is an assembly drawing of a center conductor and a ferrite thin plate according to the prior art.

FIG. 2 is an assembly drawing of a center conductor and a ferrite thin plate in the prior art.

FIG. 3 is an assembly drawing of a center conductor and a ferrite thin plate in the prior art.

FIG. 4 is an assembly diagram of a center conductor and a ferrite thin plate according to an embodiment of the present invention.

FIG. 5 is a structural diagram of a center conductor and a ferrite thin plate according to an embodiment of the present invention.

FIG. 6 is a structural diagram of a center conductor and a ferrite thin plate according to another embodiment of the present invention.

FIG. 7 is a magnetic circuit diagram according to an embodiment of the present invention.

FIG. 8 is a structural diagram of a center conductor and a ferrite laminate according to still another embodiment of the present invention.

FIG. 9 is a development view of an element sheet of the ferrite laminate according to the embodiment of the present invention.

FIG. 10 is an equivalent circuit and a schematic assembly diagram of a conventional two-terminal pair isolator.

FIG. 11 is an equivalent circuit of an isolator based on a conventional three-terminal pair circulator.

[Explanation of symbols]

L1, L2 ... center conductor W ... maximum width of center conductor G, G1, G2 ... ferrite sheet G11, G12, G21, G22 ... element sheet of ferrite laminate S ... side length of ferrite sheet GR ... ground conductor C1, C2… Matching capacitor R… Resistor…… I / O terminal MAG… Permanent magnet SH… Magnetic shield case

Claims (7)

[Claims] A first and a second center conductor are arranged close to a ferrite thin plate so as to cross each other in an electrically insulated state, and the ferrite thin plate is applied with a static magnetic field by a magnet, One ends of the first and second center conductors become first and second input / output terminals, respectively, and the other ends are connected to a common unit. A matching capacitor is connected, a second matching capacitor is connected between the second input / output terminal and the common part, and a resistance element is connected between the first and second input / output terminals. In the two-terminal isolator, the shape of the at least one ferrite thin plate is rectangular, and each of the first and second center conductors is parallel to each of the sides forming an angle of the rectangular ferrite thin plate, And the central part of each center conductor Is divided into three or more lines. 2. A ferrite laminate in which first and second center conductors are arranged close to a ferrite thin plate so as to cross each other in an electrically insulated state, and a static magnetic field is applied to the ferrite laminate by a magnet. , The first and second central conductors have first and second input / output terminals, respectively, and the other end is connected to a common unit, and a first input / output terminal is provided between the first input / output terminal and the common unit. A second matching capacitor is connected between the second input / output terminal and the common portion, and a resistance element is connected between the first and second input / output terminals. In the two-terminal pair isolator, the first and second center conductors are disposed between a plurality of ferrite laminates that have been co-fired, and the shape of at least one ferrite thin plate is rectangular. Each of the first and second center conductors is the rectangular ferrite. The central part of each central conductor is parallel to each of the sides forming the angle of the
A two-port isolator characterized by being divided into more than two. 3. The two-terminal pair isolator according to claim 1, wherein an entire width of the center conductor is equal to or more than １ ／ of a length of one side of the ferrite thin plate. 4. The ferrite thin plate, the center conductor, the matching capacitor, and the resistance element are housed in a rectangular case, and the resistance element is included in close proximity to only one corner of the rectangular case. The two-terminal pair isolator according to claim 1, wherein 5. The ferrite thin plate, the center conductor, the matching capacitor, and the resistance element are housed in a rectangular case, and the matching capacitor is a flat plate capacitor, and a long side of the flat plate capacitor has the rectangular shape. 5. The two-terminal-pair isolator according to claim 1, wherein the two-terminal pair is arranged parallel to a side of the ferrite thin plate. 6. The first and second center conductors, which are electrically insulated from each other and intersect with each other, are closely arranged between two first and second ferrite thin plates, and the first and second center ferrite plates are provided by a permanent magnet. A static magnetic field is applied from the direction of the second ferrite thin plate, and the saturation magnetization of the second ferrite thin plate
6. The two-terminal-pair isolator according to claim 1, wherein the saturation magnetization is larger than the saturation magnetization of the ferrite thin plate. 7. The two-terminal pair isolator according to claim 1, wherein the common part is a ground conductor.