JP2840814B2 - Chip type transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-type transformer, and more particularly to an impedance converter for converting the impedance of a transmission line in a high-frequency circuit of a UHF band or higher, a signal of a balanced transmission line and a signal of an unbalanced transmission line. The present invention relates to a chip type transformer used as a balun transformer such as a signal converter or a phase converter for mutually converting.

[0002]

2. Description of the Related Art A balun transformer is, for example, for mutually converting a signal on a balanced transmission line (balanced transmission line) and a signal on an unbalanced transmission line (unbalanced transmission line). It is an abbreviation of balance-unbalance.

A balanced transmission line is, as shown in FIG.
It includes two signal lines that form a pair and propagates a signal as a potential difference between the two signal lines. In a balanced transmission line, since external noise affects two signal lines equally, there is an advantage that the external noise is canceled out and is less affected by the external noise. Further, since the internal circuit of the analog IC is constituted by a differential amplifier, the input / output terminal for the signal of the analog IC is often of a balanced type which inputs or outputs a signal as a potential difference between the two terminals.

On the other hand, an unbalanced transmission line is one that
As shown in FIG. 2, a signal propagates as a potential of one transmission line with respect to a ground potential (zero potential). For example, a coaxial line or a signal line (microstrip line) on a substrate corresponds to this.

FIG. 13 is an illustrative view showing one example of a balun transformer which is the background of the present invention and to which the present invention is applied. The balun transformer 1 has three input / output terminals 2a, 2b
And 2c. Using this balun transformer 1,
In order to mutually convert the signal of the unbalanced transmission line and the signal of the balanced transmission line, for example, one input / output terminal 2a
Unbalanced transmission line is connected to the other two input / output terminals 2
Two signal lines of balanced transmission lines are connected to b and 2c, respectively. Then, the signal on the unbalanced transmission line is extracted between the two signal lines of the balanced transmission line, or the signal between the two signal lines of the balanced transmission line is extracted by the balun transformer 1 to the unbalanced transmission line.

FIG. 14 is a perspective view showing an example of a conventional balun transformer using a core. The balun transformer 1 shown in FIG. 14 includes an eight-shaped core 3, on which three coils 4a, 4b and 4c are wound together. One ends of the coils 4a, 4b and 4c are connected to input / output terminals 2a, 2b and 2c, respectively, and the other ends of the coils 4a, 4b and 4c are grounded. Therefore, the balun transformer 1 shown in FIG.
Has an equivalent circuit shown in FIG.

However, a balun transformer 1 shown in FIG.
As shown in FIG. 16, the conversion loss is large in a high-frequency band equal to or higher than the UHF band, and there is a limit to miniaturization.

Therefore, in such a band, a balun transformer having a laminated structure is used.

FIG. 17 is an illustrative view showing one example of a conventional balun transformer having a laminated structure. The balun transformer 1 shown in FIG. 17 includes two laminated dielectric substrates (layers) 5a and 5b. On one main surface of the uppermost dielectric substrate 5a,
A first strip line 6 is formed. The first strip line 6 includes a linear first portion 6a having a narrow width and a linear second portion 6b having a wide width. One end of the first strip line 6 is connected to one input / output terminal 2a. The other end of the first strip line 6 is open. A linear second strip line 7a and a linear third strip line 7b are formed between the two dielectric substrates 5a and 5b. in this case,
The second strip line 7a is formed so as to be electromagnetically coupled to the first portion 6a of the first strip line 6. Further, the third strip line 7b is formed so as to be electromagnetically coupled to the second portion 6b of the first strip line 6. Opposite inner ends of the second strip line 7a and the third strip line 7b are connected to the other two input / output terminals 2b and 2c via lead-out portions 8a and 8b, respectively. A ground electrode 9 is formed on the other main surface of the dielectric substrate 5b. The outer ends of the second strip line 7a and the third strip line 7b are connected to the ground electrode 9. Therefore,
The balun transformer 1 shown in FIG. 17 has an equivalent circuit shown in FIG.

However, the balun transformer 1 shown in FIG.
In such a case, since the dimensional accuracy affects the characteristics, it is difficult to apply the circuit design to a circuit that requires miniaturization, such as a mobile wireless device.

Therefore, the inventor of the present application has devised a chip type transformer which can be used in a balun transformer and can be reduced in size. This chip type transformer includes a dielectric substrate, a first strip line formed in a meandering or spiral shape on one main surface of the dielectric substrate, and a meandering or spiral shape in the other main surface of the dielectric substrate. And a second strip line electromagnetically coupled to the first portion of the first strip line, and a meandering or spiral shape formed on the other main surface of the dielectric substrate, 2
And a third strip line that is electromagnetically coupled to a portion of the chip type transformer.

In the above-mentioned chip type transformer, the first strip line, the second strip line, and the third strip line are formed on one main surface and the other main surface of the dielectric substrate in a laminated manner. No large area dielectric substrate is required to form these strip lines.
Further, since the first strip line, the second strip line, and the third strip line are formed in a meandering or spiral shape, respectively, the respective strip lines do not become longer in one direction. Therefore, this chip type transformer can be downsized.

In order to use the above-mentioned chip type transformer as a balun transformer, an unbalanced transmission line is connected to the first strip line, and two balanced transmission lines are connected to the second strip line and the third strip line. The two signal lines are respectively connected. Then, the signal of the unbalanced transmission line is extracted between the two signal lines of the balanced transmission line, or the signal between the two signal lines of the balanced transmission line is extracted to the unbalanced transmission line by the chip type transformer.

[0014]

In the balun transformer 1 shown in FIG. 17 and the above-described chip type transformer, the first part of the first strip line, the second part of the first strip line, and the second strip If the line and the third strip line are formed to have the same length, ideally, the phase difference of the signal between the two input / output terminals to which the balanced transmission line is connected is 180 degrees. , The phase difference is 1
It is extremely difficult to design with a high degree of accuracy at 80 degrees. Therefore, noise in the two signal lines of the balanced transmission line connected to the two input / output terminals is not efficiently canceled.

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a chip type transformer used in a balun transformer and capable of efficiently canceling noise in two signal lines of a balanced transmission line.

[0016]

According to the present invention, there is provided a dielectric substrate, a first strip line formed on one main surface of the dielectric substrate, and a first strip line formed on the other main surface of the dielectric substrate. A second strip line electromagnetically coupled to the first portion of the strip line, and a second strip line formed on the other main surface of the dielectric substrate;
A third stripline electromagnetically coupled to a second portion of the first stripline, wherein the first portion of the first stripline and the second stripline are formed to have the same length, and The second portion of the strip line and the third strip line are formed to have the same length, and further, the second strip line and the third strip line are formed to have different lengths. is there.

In the chip type transformer according to the present invention, in order to reduce the size, the first portion of the first strip line, the second portion of the first strip line, the second strip line, and the The strip lines 3 are preferably formed in a meandering or spiral shape, respectively.

[0018]

In order to use the chip type transformer according to the present invention as a balun transformer, an unbalanced transmission line is connected to the first strip line, and two balanced transmission lines are connected to the second strip line and the third strip line. The two signal lines are respectively connected. Then, the signal of the unbalanced transmission line is extracted between the two signal lines of the balanced transmission line, or the signal between the two signal lines of the balanced transmission line is extracted to the unbalanced transmission line by the chip type transformer.

Further, in the chip type transformer according to the present invention, the first portion of the first strip line and the second strip line are formed to have the same length, and the second portion of the first strip line is connected to the second portion of the first strip line. The third strip line is formed to have the same length, and the second strip line and the third
Of the second strip line and the third strip line to which the balanced transmission line is easily connected can be designed so that the phase difference of the signal between the second strip line and the third strip line becomes 180 degrees. . Therefore, noise in the two signal lines of the balanced transmission line connected to the second strip line and the third strip line can be efficiently canceled.

[0020]

According to the present invention, it is possible to obtain a chip type transformer used in a balun transformer and capable of efficiently canceling noise in two signal lines of a balanced transmission line.

Further, in the chip type transformer according to the present invention, the first portion of the first strip line and the first portion are connected to each other.
If the second portion, the second strip line, and the third strip line of the strip line are formed in a meandering or spiral shape, respectively, the respective strip lines do not become longer in one direction. Therefore, the size of the chip transformer can be reduced.

Further, according to the present invention, since the lengths of the second strip line and the third strip line are formed to be different lengths, the signal of the signal between the second strip line and the third strip line is formed. 1 phase difference
It is easy to design at 80 degrees, the design accuracy is not so required, and the degree of freedom can be increased.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0024]

FIG. 1 is a perspective view showing an embodiment of the present invention. A balun transformer 10 as a chip-type transformer includes a multilayer body 12, and the multilayer body 12, as shown in FIG. 2, is laminated with first, second, third, fourth, and fifth dielectric substrates (layers). ) 14a, 14b, 14c, 14d and 14e
including.

On one main surface of the second dielectric substrate 14b from the top, a connection electrode 20 is formed obliquely from substantially the center to the other end.

On one main surface of the third third dielectric substrate 14c from the top, a first strip line 22 of λ / 2 is formed. The first strip line 22 includes a first spiral portion 24a having a small width and a second spiral portion 2a.
4b. The second portion 24b is a first portion 24
For example, it is formed to have a length of 1.08 times as long as a. Further, a portion outside the first portion 24a and a portion outside the second portion 24b are formed and connected in series. Furthermore, the first
Of the inside of the portion 24a of the second dielectric substrate 14b
Is connected to one end of the connection electrode 20 via the via hole 15a formed in the second portion, and the tip inside the second portion 24b is opened.

On one main surface of the fourth fourth dielectric substrate 14d from the top, a spiral second strip of λ / 4 having the same length as the first portion 24a of the first strip line 22 is provided. A line 26 and a spiral strip strip line 28 of λ / 4 having the same length as the second portion 24b of the first strip line 22 are formed at intervals. That is, the third strip line 28 is formed to be, for example, 1.08 times as long as the second strip line 26.
In this case, the second strip line 26 is formed so as to face the first portion 24a of the first strip line 22 with the third dielectric substrate 14c interposed therebetween. Therefore, the second strip line 26 is electromagnetically coupled to the first portion 24a of the first strip line 22. That is, the first portion 24a of the first strip line 22
And the second strip line 26 constitutes a coupler. The third strip line 28 is formed to face the second portion 24b of the first strip line 22 with the third dielectric substrate 14c interposed therebetween. Therefore, the third strip line 28 is electromagnetically coupled to the second portion 24b of the first strip line 22. That is, the second portion 24b of the first strip line 22
And the third strip line 28 constitutes a coupler. Further, one end outside the second strip line 26 and one end outside the third strip line 28 are formed toward one end side of the fourth dielectric substrate 14d.

A ground electrode 30 is formed on substantially one entire surface of one bottom surface of the fifth fifth dielectric substrate 14e.
Four lead-out terminals 32a, 32b, 32c and 32d are formed from the ground electrode 30 toward the end of the fifth dielectric substrate 14e. Two extraction terminals 32a and 32
"b" is formed toward one end of the fifth dielectric substrate 14e, and is formed spaced apart from each other. The other two lead-out terminals 32c and 32d are formed toward the other end of the fifth dielectric substrate 14e, and are formed apart from each other. The other end inside the second strip line 26 and the other end inside the third strip line 28 are connected to the ground electrode 30 via via holes 15b and 15c formed in the fourth dielectric substrate 14d. Are respectively connected.

As shown in FIG. 1, the eight external electrodes 34a, 34b, 34c, 3
4d, 34e, 34f, 34g and 34h are formed. Of these external electrodes, four external electrodes 34a to 34a to
34d is formed on one end of the multilayer body 12, and the other four external electrodes 34e to 34h are formed on the other end side of the multilayer body 12.

External electrodes 34a, 34d, 34e and 3
4h is a lead terminal 32a, 32b, 3 of the ground electrode 30.
2c and 32d, respectively. Therefore,
These external electrodes 34a, 34d, 34e and 34h
Are used as ground terminals.

The external electrode 34b is connected to one end of the second strip line 26, and the external electrode 34c is connected to one end of the third strip line 28.
g is connected to the other end of the connection electrode 20 connected to the first strip line 22. These external electrodes 34b, 3
4c and 34g are used as input / output terminals, respectively.

Therefore, this balun transformer 10
It has an equivalent circuit shown in FIG.

In the balun transformer 10, the first strip line 22, the second strip line 26 and the third strip line 28 are connected to the third dielectric substrate 14
c is formed on one main surface and the other main surface in a laminated manner,
No large area dielectric substrate is required to form these strip lines. Further, in the balun transformer 10, the first portion 2 of the first strip line 22 is
4a and the second portion 24b of the first strip line 22
And the second strip line 26 and the third strip line 28 are each formed in a spiral shape, so that the respective strip lines do not become longer in one direction. Therefore, the size of the balun transformer 10 can be reduced.

In the balun transformer 10, in order to convert the signal of the unbalanced transmission line and the signal of the balanced transmission line into each other, the unbalanced transmission line is connected to the first strip line 22 via the external electrode 34g or the like. Are connected, and two signal lines of balanced transmission lines are connected to the second strip line 26 and the third strip line 28 via the external electrodes 34b and 34c, respectively. The balun transformer 10 extracts a signal of the unbalanced transmission line between the two signal lines of the balanced transmission line, or extracts a signal between the two signal lines of the balanced transmission line to the unbalanced transmission line.

In this case, in the balun transformer 10,
The first portion 24a of the first strip line 22 and the second
Are formed to have the same length, the second portion 24b of the first strip line 22 is formed to have the same length as the third strip line 28, and the second strip line 26 is formed to have the same length. By forming the third strip line 28 with a different length in advance, the signal phase difference between the two input / output terminals to which the balanced transmission line is easily connected, that is, the external electrodes 34b and 34c is reduced to 180 degrees. Can be designed to be.

Therefore, in the balun transformer 10, the noise in the two signal lines of the balanced transmission lines connected to the external electrodes 34b and 34c can be efficiently canceled.

In this balun transformer 10,
The first portion 24a of the first strip line 22 and the second
Are formed to have the same length, and the second portion 24b of the first strip line 22 and the third strip line 28 are formed to have the same length. The ratio L3 / L2 (%) of the length L2 to the length L2 of the second strip line 26 and the phase difference of the signal between the two input / output terminals to which the balanced transmission line is connected, ie, between the external electrodes 34b and 34c ( 4) is shown in FIG.

The balun transformer 10 is used, for example, as shown in FIG. 5, for extracting signals from two output terminals of an analog high-frequency IC to an unbalanced transmission line, or as shown in FIG. It is used on the input side and output side of two amplifiers in a balanced power amplifier, respectively, or as a 180-degree phase converter in a double balanced mixer as shown in FIG.

Further, in the balun transformer 10, the strip lines and the electrodes between the dielectric substrates are connected via via holes, and the external electrodes on the surface of the laminate 12 are used as terminals, so that other electric circuits and the like can be used. Good electrical matching.

In the balun transformer 10, since the external electrodes serving as the input / output terminal and the ground terminal are formed on the surface of the laminated body 12, it can be surface-mounted on, for example, a printed circuit board.

Further, in the balun transformer 10, the thickness of the dielectric substrate can be arbitrarily set, and if the thickness is changed, the characteristic impedance changes, so that the degree of freedom of the characteristic impedance is large.

As the material of the dielectric substrate, either resin or ceramic dielectric may be used. However, the dielectric loss of the ceramic dielectric is smaller than that of glass epoxy resin as shown below. Since it is small and has an excellent heat radiation effect, if a ceramic dielectric is used as the material of the dielectric substrate, the loss can be reduced and the size can be further reduced. Glass epoxy resin tan δ = 0.02 Ceramic dielectric tan δ = 0.0007

If a ceramic dielectric or a glass epoxy resin having a small dielectric loss is used as a material of the dielectric substrate, and a material having a high conductivity such as copper is used as a material of the strip line and the electrode, A balun transformer with a small conversion loss can be obtained.

The balun transformer 10 includes, for example, a plurality of large first dielectric substrates 14a, a plurality of connection electrodes 20 formed large second dielectric substrates 14b, A large third dielectric substrate 14c on which a first strip line 22 is formed, and a large fourth dielectric substrate 14d on which a plurality of second and third strip lines 26 and 28 are formed. By stacking a large fifth dielectric substrate 14e on which a plurality of ground electrodes 30 and the like are formed into a mother laminate and cutting it into individual laminates 12, mass production is possible.

FIG. 8 is a perspective view showing another embodiment of the present invention, and FIG. 9 is an exploded perspective view of the laminate of the embodiment shown in FIG. In the embodiment shown in FIG. 8, a ground electrode 16 is formed on almost the entirety of one main surface of the first dielectric substrate 14a on the top of the stacked body 12, as compared with the embodiment shown in FIG. Further, from the ground electrode 16 toward the end of the first dielectric substrate 14a, four lead-out terminals 18a, 18b, 18c are provided.
And 18d are formed. In this case, the two lead terminals 18a and 18b are formed toward one end of the first dielectric substrate 14a, and are formed at an interval from each other. The other two lead-out terminals 18c and 18d are formed toward the other end of the first dielectric substrate 14a, and are formed apart from each other. These lead terminals 18a, 1
8b, 18c and 18d are external electrodes 34a and 34
d, 34e and 34h, respectively.

In the embodiment shown in FIG. 8, the connection electrode 20 is formed obliquely as shown in FIG.
Is connected to the external electrode 34g. Therefore, the embodiment shown in FIG. 8 has the equivalent circuit shown in FIG.

In the embodiment shown in FIG. 8, as in the embodiment shown in FIG. 1, it is possible to reduce the size and efficiently cancel noise in two signal lines of the balanced transmission line.

In the embodiment shown in FIG.
Since the ground electrode 16 is formed on the upper surface of the device, a shielding effect is provided. The ground electrode 16 is preferably formed at a certain distance from the strip line so as not to adversely affect the characteristics of the balun transformer 10. In addition, the ground electrode 16 does not necessarily need to be exposed on the upper surface of the multilayer body 12, and may be integrally covered with another dielectric substrate (layer).

In each of the above-described embodiments, the first portion 24a, the second portion 24b, and the second
Strip line 26 and third strip line 28
Are formed to specific lengths, however, if the characteristics are adjusted, they may be formed to other lengths.

In each of the above embodiments, the first portion 24a of the first strip line 22, the second portion 24b of the first strip line 22, the second strip line 26, and the third strip line Although each of the strip lines 28 is formed in a spiral shape, in the present invention, the strip lines may be formed to meander. Even if each strip line is formed so as to meander, each strip line does not become longer in one direction, and downsizing can be achieved.

The first strip line 22 and the second strip line 22
The strip line 26 and the third strip line 28 may be formed linearly.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of 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 shows a ratio L3 / L2 (%) of the length L3 of the third strip line and the length L2 of the second strip line in the chip type transformer shown in FIG. 6 is a graph showing a relationship with a phase difference (degree) between output terminals.

FIG. 5 is a circuit diagram showing an example of an application of the embodiment shown in FIG. 1;

FIG. 6 is a circuit diagram showing another example of the use of the embodiment shown in FIG. 1;

FIG. 7 is a circuit diagram showing still another example of the application of the embodiment shown in FIG. 1;

FIG. 8 is a perspective view showing another embodiment of the present invention.

FIG. 9 is an exploded perspective view of the laminate of the embodiment shown in FIG.

FIG. 10 is an equivalent circuit diagram of the embodiment shown in FIG.

FIG. 11 is an illustrative view showing one example of a balanced transmission line;

FIG. 12 is an illustrative view showing one example of an unbalanced transmission line;

FIG. 13 is an illustrative view showing one example of a balun transformer which is a background of the present invention and to which the present invention is applied;

FIG. 14 is a perspective view showing an example of a conventional balun transformer using a core.

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

16 is a graph showing frequency characteristics of the balun transformer shown in FIG.

FIG. 17 is an illustrative view showing one example of a conventional balun transformer having a laminated structure;

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 balun transformer 12 laminated body 14 a to 14 e dielectric substrate (layer) 15 a to 15 c via hole 16, 30 ground electrode 18 a to 18 d, 32 a to 32 d extraction terminal 20 connection electrode 22 first strip line 24 a first portion 24 b second Part 26 second strip line 28 third strip line 34a-34h external electrode

Claims (2)

(57) [Claims] A first strip line formed on one main surface of the dielectric substrate; a first portion of the first strip line formed on the other main surface of the dielectric substrate; A second strip line electromagnetically coupled to the first strip line and a third strip line formed on the other main surface of the dielectric substrate and electromagnetically coupled to a second portion of the first strip line. A first portion of the strip line and the second strip line are formed to the same length; a second portion of the first strip line and the third strip line are formed to the same length; Further, a chip type transformer, wherein the second strip line and the third strip line have different lengths. 2. A first portion of the first stripline, a second portion of the first stripline, the second stripline, and the third stripline, respectively, 2. The chip type transformer according to claim 1, wherein the chip type transformer is formed in a meandering or spiral shape.