JP2002190413A - Laminated balun transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated balun transformer that is reduced in size, particularly, in thickness. SOLUTION: This laminated balun transformer is composed of a first strip line 21, having first and second conductors 22a and 22b and provided on one main surface of a dielectric substrate 12c, a second strip line 23 which is provided on the other main surface of the substrate 12 to face the first conductor 22a, and a third strip line 24 faced to the second conductor 22b via the substrate 12c. The transformer is also composed of a grounding electrode 16, which faces the first strip line 21 via the substrate 12b and to which one ends of the first and second conductors 22a and 22b are connected via the substrate 12c.

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. 6, a balun transformer 1 has three input / output terminals 2a, 2b and 2c, an unbalanced transmission line 3, and balanced transmission lines 4a and 4b. In order to use the balun transformer 1 to convert the signal of the unbalanced transmission line 3 and the signal of the balanced transmission lines 4a and 4b to each other, for example, the unbalanced transmission line 3 is connected to one input / output terminal 2a. The balanced transmission lines 4a and 4b are connected to the other two input / output terminals 2b and 2c, respectively. Then, the signal of the unbalanced transmission line 3 is extracted between the balanced transmission lines 4a and 4b by the balun transformer 1, or the signal between the two signal lines of the balanced transmission line is extracted to the unbalanced transmission line. Here, a balun transformer 1 'having a coaxial structure is generally used in a high-frequency band equal to or higher than the UHF band in consideration of conversion loss.

FIG. 5 is an explanatory diagram showing an example of a common balun transformer 1 'having a coaxial structure. The balun transformer 7 'shown in FIG. 5 includes a center electrode 3'. One input / output terminal 2a 'is connected to one end of the center electrode 3'. The other end of the center electrode 3 'is open. Around the center electrode 3 ', two internal electrodes 4a' and 4b 'are provided so as to be electromagnetically coupled to the center electrode 3'.

[0004] Opposite inner ends of the two internal electrodes 4a 'and 4b' are connected to the other two ends via leads 5a 'and 5b'.
And input / output terminals 2b 'and 2c', respectively. Further, a ground electrode 6 'is provided around the two internal electrodes 4a' and 4b 'with a dielectric interposed therebetween. Both ends of the ground electrode 6 'are connected to outer ends of the internal electrodes 4a' and 4b '. In the balun transformer having the coaxial structure having the above-described configuration, it is difficult to apply the circuit to a circuit design that requires a small size, such as a mobile wireless device, because the structure tends to be large.

[0005] Therefore, a small-sized balun transformer of a laminated type has recently been devised. FIG. 7 shows a stacked type small balun transformer structure. As the present structure, the dielectric substrate 12
0a to 120e are laminated, and the dielectric substrate 120 is a laminated body.
c first strip line 210 of λ / 2 on one main surface
However, the second and third striplines 230 and 240 of λ / 4 are formed on the other main surface of the dielectric substrate 120c, and the ground electrodes 160 and 160 are sandwiched from above and below. In addition, one end of the first strip line 210 is connected to the connection electrode 200 formed on the dielectric substrate 120b via the dielectric substrate, while each of the second and third strip lines 230 and 240 is respectively connected. Is connected to a ground electrode 160 formed on the lower side. 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).

[0007]

However, in the balun transformer shown in FIG. 6, when compared with the conventional coaxial structure,
Although effective for miniaturization, the two ground electrodes 160, 16
Substrate 120b on which the first and second connection electrodes 200 are formed
Must be laminated on the equivalent circuit, and there is a problem in terms of the number of laminations when further miniaturization and consideration of a substrate inner layer type such as a high-frequency module.

The present invention has been devised in view of the above problems, and an object of the present invention is to provide a balun transformer that can be reduced in size, particularly, reduced in thickness.

[0009]

According to the present invention, there is provided a first dielectric substrate having a first dielectric substrate having a first conductor and a second conductor having one end opened and formed in a spiral or meandering shape on one principal surface of the first dielectric substrate. A strip line, on the other main surface of the first dielectric substrate,
Facing the first conductor via a dielectric substrate, and
A second strip line formed in a spiral or meandering shape corresponding to the conductor, and on the other main surface of the first dielectric substrate,
A third strip line which is opposed to the second conductor via a dielectric substrate and is formed in a spiral or meandering shape corresponding to the second conductor, and a second dielectric substrate is provided on the first strip line. A stacked balun transformer comprising a ground electrode opposed to the ground electrode and having one end of the second conductor and the third conductor connected via the first dielectric substrate and the second dielectric substrate.

[0010]

According to the structure of the present invention, the earth electrode has a structure in which one end of the second conductor and one end of the third conductor are connected to face only the first strip line, and the dielectric material substantially contributes to the thickness. Since the substrate is a dielectric substrate on which the first to third strip lines are formed, it can have a thin structure.

[0011]

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 includes dielectric substrate layers 12a, 12b,
It comprises a laminated body 11 in which 12c and 12d are sequentially laminated.

As shown in FIG. 2, a connection electrode 20 is formed on one main surface of the uppermost dielectric substrate 12a, and the connection electrode 20 is drawn out to the end face side of the dielectric substrate 12a. It is connected to the end face electrode 15b.

As shown in FIG. 2, a ground electrode 16 is formed on substantially one entire surface of one main surface of the second dielectric substrate 12b from the top. The three lead-out terminals 14a, 14b, 14 are provided on the ground electrode 16 toward the end of the dielectric substrate 12a.
c is formed, and the terminal electrodes 15a, 15c, 1
5e.

On one main surface of the third dielectric substrate 12c from the top, a λ / 2 first strip line 21 is formed. The strip line 21 includes a spiral first conductor 22a and a spiral second conductor 22b. The first conductor 22a and the second conductor 22b are formed at the same length with an interval therebetween. Further, the portion outside the first conductor 22a and the portion outside the second conductor 22b are formed and connected in series. Further, an inner end of the first conductor 22a is connected to one end of the connection electrode 20 via a via hole 13b formed in the dielectric substrate 12b and a via hole 13a formed in the dielectric substrate 12a. The tip of is opened. The via-hole conductor 13a has a structure in which the inside of the notch 16a formed in the ground electrode 16 communicates.

On one main surface of the fourth dielectric substrate 12 d from the top, a second λ / 4 of half of the first strip line 21 having a length corresponding to the first strip line 21 is provided.
The strip line 23 is formed in a spiral shape from the center to the outside. In addition, the second strip lines 23 are spaced apart from each other.
Λ / 4 third strip line 2 of the same length as
4 are formed, and the strip line has a spiral shape extending from the center to the outside. In this case, the second strip line 23 is formed so as to face the first conductor 22a of the first strip line 21 with the dielectric substrate 12c interposed therebetween. Therefore, the second strip line 2
3 is electromagnetically coupled to the first conductor 22a of the first strip line 21. That is, the first strip line 21
The one conductor 22a and the second strip line 23 constitute a coupler. Similarly, the third strip line 24 is formed so as to face the second conductor 22b of the first strip line 21 with the dielectric substrate 12c interposed therebetween, and is electromagnetically coupled to form a coupler.

Further, the outside where the second strip line 23 spirals and the outside where the third strip line 24 spirals are formed toward the end face of the dielectric substrate 12d, and the terminal electrodes 15d and 15f are connected. Is done.
The other ends inside the second strip line 23 spirals and the other inside the third strip line 24 spirals are via holes 13e and 13f formed in the dielectric substrate 12c and via holes formed in the dielectric substrate 12b. 13
The electrodes are connected to the earth electrode 16 of the dielectric substrate 12b via the terminals c and 13d. The via holes 13e,
As the position of the dielectric substrate 12c where 13f is formed,
It is preferable that the first and second conductors 22a and 22b be formed so as to penetrate through the inner central region formed by the spiral. This position is a dead space where no signal line is formed, and by forming it here, it is possible to form the circuit compactly without drawing out electrodes and without complicating the circuit. However, the present invention is not limited to such a configuration, and may be drawn to the outer end face and connected to the ground electrode 16.

The above-mentioned six external terminal electrodes 15a, 15
b, 15c, 15d, 15e, and 15f are formed on the side surfaces of the multilayer body 11. Note that, as described above, the external terminal electrode 15
a, 15c, and 15e are the extraction terminals 14 of the ground electrode 16.
a, 14b, and 14c, respectively, and these external electrodes 15a, 15c, and 15e are used as ground terminals. The external electrode 15d is connected to one end of the second strip line 23, the external electrode 15f is connected to one end of the third strip line 24, and the external electrode 15b is a connection electrode connected to the first strip line 21. 20
Is connected to the other end. These external electrodes 15b, 15
d and 15f are used as input / output terminals, respectively.

In the balun transformer 10, the first strip line 21, the second strip line 23 and the third strip line 24 are formed on one main surface and the other main surface of the dielectric substrate 12c in a laminated manner. Therefore, a dielectric substrate having a large area is not required to form these strip lines. In this balun transformer 10,
First strip line 2 via external electrode 15b or the like
1 is connected to an unbalanced transmission line, and external electrodes 15d and 1
Two signal lines of balanced transmission lines are respectively connected to the second strip line 23 and the third strip line 24 via 5f. And this balun transformer 10
As a result, the first and second conductors 22 serving as unbalanced transmission lines
a and 22b are extracted between the two signal lines of the second strip line 23 and the third strip line 24 which are balanced transmission lines, or the signal between the two signal lines of the balanced transmission line is unbalanced transmission line. Is taken out.

In the balun transformer 10, the strip lines and the electrodes between the dielectric substrates are connected through via holes, and the external electrodes on the surface of the laminate 11 are used as terminals, so that the balun transformer 10 can be connected to other electric circuits. Good electrical matching.

In the above-described embodiment, the first conductor 22a and the second conductor 22b of the first strip line 21
Although the second strip line 23 and the third strip line 24 are each formed to have a length of λ / 4,
If the properties are adjusted, they need not necessarily be formed to a length of λ / 4.

As another embodiment, as shown in FIG.
The connection electrode 20 formed on the surface of the dielectric substrate 12a in FIG.
By omitting a part of the ground electrode on the surface of the dielectric substrate 12b and forming the connection electrode 20 in the cutout for the purpose of omitting the above, the number of stacked layers can be reduced and the thickness can be further reduced.

[0022]

According to the structure of the present invention, the earth electrode has a structure in which one end of the second conductor and the third conductor is connected to face only the first strip line, and substantially contributes to the thickness. Since the dielectric substrate is a dielectric substrate on which the first to third strip lines are formed, a laminated balun transformer having a thin structure can be provided.

[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. 4 is an exploded perspective view of a laminate according to another embodiment.

FIG. 5 is an explanatory diagram showing an example of a balun transformer having a coaxial structure.

FIG. 6 is an equivalent circuit diagram of the balun transformer shown in FIG.

FIG. 7 is an exploded perspective view of a conventional multilayer balun transformer.

[Explanation of symbols]

 10: Balun transformer 11: Laminated body 12a to 12d: Dielectric substrate layer 13a to 13f: Via hole 14a to 14c: Lead terminal 15a to 15f: External electrode 16: Earth electrode 20: Connection electrode 21: First strip line 22a: First conductor 22b: Second conductor 23: Second strip line 24: Third strip line

Claims (1)

[Claims] A first strip line having a first conductor and a second conductor formed in a spiral or meandering shape on one main surface of a first dielectric substrate, the first dielectric substrate having an open end and a spiral or meandering shape; A second strip line facing the first conductor via a dielectric substrate, and formed in a spiral or meandering shape corresponding to the first conductor, on the other main surface of the body substrate; A third strip line opposing the second conductor via a dielectric substrate and formed in a spiral or meandering shape corresponding to the second conductor, on the other main surface of the body substrate; A multilayer balun comprising a ground electrode opposed to the line via a second dielectric substrate and one end of a second conductor and a third conductor connected to the ground electrode via the first dielectric substrate and the second dielectric substrate. Trance.