JP2002260930A - Stacked balun transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a balun transformer which can be made compact and can improve insertion loss by optimizing the electromagnetic coupling of strip lines. SOLUTION: This standard balun transformer 11 is provided with a dielectric layer 12c where a spiral strip line 33 is formed, a dielectric layer 12b where a spiral strip line 32 is formed, a dielectric layer 12a where a spiral strip line 31 is formed, and a dielectric layer 12e where an earth electrode 40 is formed. The dielectric layers 12a and 12e are stacked in the transformer 11. In this case, the dielectric layer 12a and 12b are formed adjacent to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balun transformer. TECHNICAL FIELD The present invention relates to a multilayer balun transformer such as a signal converter or a phase converter for converting into a signal.

[0002]

2. Description of the Related Art As shown in FIG. 5, a balun transformer 1 has three input / output terminals 2a, 2b and 2c, an unbalanced transmission line 3 composed of two parts, and balanced transmission lines 4a and 4b. Using this balun transformer 1, the unbalanced transmission line 3
In order to mutually convert the signal of the transmission line 4a and the signal of the balanced transmission lines 4a and 4b, for example, the unbalanced transmission line 3 is connected to one input / output terminal 2a, and the balance is connected to the other two input / output terminals 2b and 2c. The transmission lines 4a and 4b are respectively connected.
The balun transformer 1 causes the unbalanced transmission line 3
Is extracted between the balanced transmission lines 4a and 4b, or the signal between the two signal lines of the balanced transmission line 3 is extracted to the unbalanced transmission line. Here, in a high-frequency band equal to or higher than the UHF band, a balun transformer ′ having a coaxial structure is generally used in consideration of conversion loss. However, in the balun transformer having a coaxial structure having the above-described configuration, it is difficult to apply it to a circuit design requiring a small size such as a mobile wireless device because the structure is easily enlarged. (Japanese Unexamined Patent Publication No.
176918). FIG. 6 shows a laminated type small balun transformer structure. As the present structure, the dielectric layers 120a to
A first strip line 210 of λ / 2, in which one is connected to the input-side terminal 200 and the other is open to form two spirals, is provided on one main surface of the dielectric layer 120c of the stacked body in which 120e is stacked. On the other main surface of the dielectric layer 120c, one is connected to the ground electrode 160, and the other is the spiral λ / 4 second and third strip lines 230, 2 and 2 on the output side.
40, and the ground electrode 160 is formed to face the second and third strip lines 230 and 240. Thus, the balun transformer 1 having the equivalent circuit shown in FIG. 6 is formed.

In such a balun transformer, downsizing can be achieved as compared with the conventional coaxial balun transformer, and the strip line 2 is formed by the upper ground electrode 160.
10 (unbalanced transmission line).

On the other hand, in order to make the balun transformer more compact than the balun transformer having the coaxial structure, the first, second and third balun transformers are used.
The strip lines are sequentially arranged in parallel in the horizontal direction and are connected to each other.
A conventional technology of wavelength has been disclosed (Japanese Patent Laid-Open No.
163715).

This balun transformer, as shown in FIG.
First strip line 100, second strip line 1
01, a third strip line 102, one end of the first strip line 100 is used as a signal input end 200,
And one end of the second strip line, and the other end of the second strip line 101 is connected to the third strip line 1.
02 is grounded, the other end of the first strip line 100 is a first signal output end 201, and the other end of the third strip line 102 is a second signal output end 202. is there.

When a signal is input from the signal input terminal 200 by the above-described configuration, a part of the signal is input to the first strip line 100.
Through the signal output terminal 201, and a part of the signal is resonated in the second strip line 101 to generate a standing wave. The power of the standing wave generated here is transmitted to the third strip line 102 and output from the signal output terminal 202. At this time, the phases of the signals output from the signal output terminals 201 and 202 are shifted from each other by 180 degrees. Become something. In this way, one signal is divided into two signals having the same level and a phase difference of 180 degrees.

[0007]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. 7-17691
The stacked balun transformer of No. 8 is certainly suitable for miniaturization as compared with a balun transformer having a coaxial structure. However, the second and third striplines 230, 240
Since There are formed on the same dielectric layer 120d, a further miniaturization is limited.

On the other hand, the balun transformer disclosed in Japanese Patent Application Laid-Open No. 10-163715 can be made smaller than a coaxial balun transformer, but a second stripline 101 for generating a standing wave and a third stripline for transmitting the power thereof. 1
02 are formed adjacent to each other, so that the direction of current flow is opposite to that of the third strip line 102 as compared to the second strip line 101. May occur. As a result, there is a problem that the insertion loss of the balun transformer becomes worse.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a laminated balun transformer which can be reduced in size and has improved insertion loss and improved reliability. Is to do.

[0010]

According to the present invention, a first dielectric layer having a spiral first strip line formed on one main surface and a spiral second strip line formed on one main surface are provided. and a second dielectric layer, whereas the third dielectric layer spiral third strip line is formed on the main surface, while a fourth dielectric layer substantially the entire area to the ground electrode main surface is formed ,
In the laminated balun transformer in which the first to fourth dielectric layers are stacked, an outer end of the first or second strip line is used as a signal input end, and the first and second strip lines are connected to each other. Connected at the end or in the vicinity thereof, grounding the center end of the second strip line and the center end of the third strip line to the ground electrode,
A center side end of the first strip line is a first signal output end, and an outside end of the third strip line is a second signal output end.
And wherein a third dielectric layer is laminated at least adjacent to the second dielectric layer.

According to the structure of the present invention, since the first and second signal output terminals are formed on different dielectric layers, the area in the plane direction can be formed compact.

The first to fourth dielectric layers are laminated so that the winding centers of the first to third strip lines are substantially coincident with each other, and the center side ends of the second and third strip lines are connected to the ground. If the configuration is such that the electrodes are connected by via-hole conductors, the internal wiring is not complicated and downsizing is achieved.

[0013] In the laminated balun transformer in which the first to fourth dielectric layers are laminated at least in the first to third order, the winding direction of the second strip line is set to the third direction.
A configuration in which the direction is opposite to the strip line may be adopted.

As described above, while the current directions of the second and third strip lines are opposite in the equivalent circuit, when the second and third strip lines are wound in opposite directions to each other, The electromagnetic coupling between the positive phase signal of the second strip line and the negative phase signal of the third strip line is strengthened, and the insertion loss of the balun transformer can be improved.

[0015]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the entire structure of the multilayer balun transformer of the present invention, FIG. 2 is an exploded perspective view of the multilayer body of the embodiment shown in FIG. 1, and FIG. 3 is an equivalent circuit diagram thereof.

The balun transformer 10 of the present invention comprises a laminated body 11 in which dielectric layers 12a, 12b, 12c and 12d are sequentially laminated. On one main surface of the uppermost dielectric layer 12a, there is provided a strip line 31 (third line) which is a distributed constant line.
A strip line is formed in a spiral shape, and its outer end is drawn out to the end face side of the dielectric layer 12a and connected to the balanced signal output terminal 35 (OUT2) formed there. The center side end of the strip line 31 is connected to a ground electrode 40 formed on the dielectric layer 12e via a via-hole conductor 50 described later.

On one main surface of the second dielectric layer 12b from the top, a strip line 32 (second strip line) which is a distributed constant line is formed in a spiral shape, and an outer end of the strip line 32 is formed. Is drawn out to the side surface of the dielectric layer 12b, and the input terminal 3 of the unbalanced signal formed there is formed.
Connected to 0. The center end of the strip line 32 is also connected to the dielectric layer 12 via a via-hole conductor 50 described later.
e is connected to the ground electrode 40 formed on the top of the e.

Here, the winding directions of the spiral strip lines 31 and 32 are set in opposite directions.

On one main surface of the third dielectric layer 12c from the top, a strip line 33 (first strip line), which is a distributed constant line, is spirally formed, and the outer end of the strip line 33 is a via hole conductor. The terminal 51 is connected to the input terminal 30 or the vicinity thereof. Also, the strip line 33
Of the dielectric layer 12 via the via-hole conductor 52.
d is connected to the output terminal 34 (OUT1) of the balanced signal formed on d. A region through which the via-hole conductor 50 can penetrate is formed in the vicinity of the center-side end of the strip line 33, thereby forming a via-hole conductor that is connected to the ground electrode 40 in a straight line to avoid complicated internal wiring. Wiring is simplified. Here, the winding directions of the spiral strip lines 32 and 33 are set to the same direction.

Further, on the lowermost dielectric substrate 12e,
A ground electrode 40 is formed on substantially the entire surface, and the via-hole conductor 5 is formed.
0 is connected. Also, from the ground electrode 40 toward both end surfaces of the dielectric substrate 12e, two lead terminals 41,
42 are formed.

Then, the dielectric layers 12a to 12e are laminated, and since the strip line 31 is exposed on the surface of the laminated body, the surface can be coated with glass, resin or the like to obtain the balun transformer 10.

In the present invention, the dielectric layers 12c, 12c
Although the layers are stacked in the order of b and 12a, the layers can be stacked in the reverse order, such as the dielectric layers 12a, 12b, and 12c, in this order. Also, the dielectric layers 12c, 12c
As long as b and 12a are protected, the dielectric layer 12e on which the ground electrode is formed can be laminated either above or below the laminate of the dielectric layers 12c, 12b and 12a.

Here, three strip lines 31, 3
Reference numerals 2 and 33 are set to have a length of about λ / 4, and are in a resonance state of about λ / 4 in the operating frequency range.

[0024] The side surface of the laminate 10, in particular as shown in FIG. 1, the external electrodes 15a~15e is formed. The external electrodes 15c and 15e are connected to the extraction terminal 41 of the ground electrode 40,
42 respectively. Therefore, these external electrodes 15c and 15e are used as ground terminals.
The external electrodes 15b and 15d are connected to the strip line 33.
And the output terminal connected to the strip line 31. External terminal 15
a is connected to the input terminal 30 connected to the strip line 32. Therefore, these external electrodes 15a, 1
5b and 15d are used as input / output terminals, respectively.

FIG. 3 shows an equivalent circuit of the multilayer balun transformer of the present invention. In the balun transformer 10, when a signal is input from the signal input terminal 15a, a part is output from the external electrode 15d through the strip line 33, and a part resonates in the strip line 32, and the Occurs. The standing wave power generated in the strip line 32 is transmitted to the strip line 31 and output from the external electrode 15c. At this time, the external electrode 15
The thicknesses of the dielectric layers on which the strip lines 31 to 33 are formed are appropriately set so that the levels of the signals output from d and 15c are equal. The phases of the signals output from the external electrodes 15d and 15c are 1
It is shifted by 80 degrees. In this way, one signal is divided into two signals having the same level and a phase difference of 180 degrees.

The dielectric layers 12a to 12e are stacked so that the winding centers of the strip lines 31 to 33 are substantially coincident with each other. Are connected by the via-hole conductors 50, the internal wiring does not become complicated, and miniaturization can be achieved without requiring other wiring.

Further, since the winding direction of the strip line 32 is opposite to that of the strip line 31, the current directions of the second and third strip lines are reversed on the equivalent circuit. On the other hand, if the strip lines 31 and 32 are wound in opposite directions, electromagnetic coupling between the positive-phase signal of the strip line 32 and the negative-phase signal of the strip line 31 is strengthened, and the insertion loss of the balun transformer is improved. Becomes possible.

To prove this, FIG. 4A shows the case where the winding directions of the strip lines 31 and 32 are reversed, and FIG. 4B shows the case where the strip lines 31 and 32 are wound. The insertion loss of the balun transformer 10 was examined by setting the winding direction to the same direction. As can be seen from FIG. 4, when the strip lines 31 and 32 are wound in opposite directions, the insertion loss is improved in a wider band, and the versatility is improved. Strip line 3 against it
It is understood that when 1, 32 are wound in the same direction, insertion loss is poor and versatility is lacking.

[0029]

According to the structure of the present invention, it is possible to reduce the size of the multilayer balun transformer and to provide a multilayer balun transformer in which the electromagnetic coupling between the strip lines is optimized and the insertion loss can be improved. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the overall structure of a multilayer balun transformer according to the present invention.

FIG. 2 is an exploded perspective view of the laminate of the embodiment shown in FIG.

FIG. 3 is an equivalent circuit diagram of the embodiment shown in FIG.

FIG. 4A is a diagram illustrating a relationship between an insertion loss and a frequency when the strip lines 31 and 32 are wound in opposite directions, and FIG.
It is a figure which shows the relationship between the insertion loss and frequency when 32 is wound in the same direction mutually.

FIG. 5 is an equivalent circuit diagram of a conventional balun transformer.

FIG. 6 is an exploded perspective view of the balun transformer of FIG.

FIG. 7 is an equivalent circuit diagram of another conventional multilayer balun transformer.

[Explanation of symbols]

 10: Balun transformer 11: Laminated body 12a to 12d: Dielectric layer 15a to 15f: External electrode 40: Earth electrode 31 to 33: Strip line 50, 51, 52: Via hole conductor

Claims (3)

[Claims] A first dielectric layer having a spiral first strip line formed on one main surface; a second dielectric layer having a spiral second strip line formed on one main surface; A third dielectric layer having a spiral third strip line formed on a main surface thereof, and a fourth dielectric layer having a ground electrode formed on substantially one entire surface of the main surface; In a laminated balun transformer in which body layers are laminated, an outer end of the first or second strip line is used as a signal input end, and the first and second strip lines are connected to each other at or near outer ends. The center end of the second strip line and the center end of the third strip line are grounded to the ground electrode, and the center end of the first strip line is used as a first signal output end. , The third
A stacked balun transformer, wherein an outer end of the strip line serves as a second signal output end, and a third dielectric layer is stacked at least adjacent to the second dielectric layer. 2. The first to fourth dielectric layers are laminated with the winding centers of the first to third strip lines substantially coincident with each other, and the center side ends of the second and third strip lines are grounded. 2. The multilayer balun transformer according to claim 1, wherein the electrodes are connected by via-hole conductors. 3. The multilayer balun transformer according to claim 2, wherein the winding direction of the second strip line is opposite to that of the third strip line.