JPH11214943A - Balloon transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a balloon transformer which has a balanced signal- unbalanced signal conversion function and also has a signal multiplexing or demultiplexing function. SOLUTION: This balloon transformer 20 is provided with two unbalanced transmission lines 15 and 16 and one balanced transmission line 17, that is provided between them. The lines 15 and 16 have respectively line parts L11 and L12 and line parts L15 and L16 which are connected serially. The line 17 has a pair of line parts L13 and L14. The parts L11 and L12 respectively have electric length that corresponds to quarter-wavelength of an application center frequency of an unbalanced signal S2, which is inputted and outputted to/from an unbalanced signal terminal 12. The electric length of the parts L13 and L14 compares the parts L11 and L12 with the parts L15 and L16 and adjusts the longer electric length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balun transformer, and more particularly to a balun transformer used as a balanced-unbalanced signal converter or a phase converter for an IC for a wireless communication device such as a portable telephone or a car telephone.

[0002]

2. Description of the Related Art A balun transformer is for converting a balanced signal of a balanced transmission line (balanced transmission line) and an unbalanced signal of an unbalanced transmission line (unbalanced transmission line) into and out of each other. Is an abbreviation for balance-unbalance. A balanced transmission line has two signal lines forming a pair, and a signal (balanced signal) propagates 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 susceptible to the external noise. Further, since the internal circuit of the analog IC is constituted by a differential amplifier, the input / output terminals for signals of the analog IC are often of a balanced type for inputting or outputting a signal as a potential difference between two terminals. On the other hand, an unbalanced transmission line is a signal in which a signal (unbalanced signal) propagates as a potential of one signal line with respect to a ground potential (zero potential). For example, a coaxial line or a microslip line on a substrate corresponds to this.

Conventionally, a balun transformer having a structure in which a winding is bifilar wound around a magnetic core such as ferrite has been used as a balance-unbalance converter for a transmission line in a high-frequency circuit. However, the balun transformer having this structure has a large conversion loss in a high-frequency band equal to or higher than the UHF band, and has a limit in miniaturization.

For such a frequency band, a balun transformer having a circuit configuration as shown in FIG. 4, that is, a so-called Marchand balun transformer 10 has been used. The balun transformer 10 includes one unbalanced transmission line 5 and one balanced transmission line 6. The unbalanced transmission line 5 has line portions L1 and L2 connected in series. One end of the unbalanced transmission line 5 is connected to the unbalanced signal terminal 1, and the other end is open. The balanced transmission line 6 has a pair of line portions L3, L4. Each of the line portions L3 and L4 has one end connected to the ground and the other end connected to the balanced signal terminal 2.
a, 2b. The line portions L1 to L4 each have an electrical length corresponding to a quarter wavelength, the line portions L1 and L3 are electromagnetically coupled, and the line portions L2 and L4 are electromagnetically coupled.

[0005]

The conventional balun transformer 10 converts one unbalanced signal and one balanced signal into unbalanced-balanced signals, but separates one balanced signal. It does not have a demultiplexing function of multiplexing and transmitting two unbalanced signals or a multiplexing function of multiplexing two unbalanced signals and transmitting as one balanced signal. On the other hand, as shown in FIG. 5, for example, two voltage-controlled oscillators (VCOs)
The two unbalanced signals having different frequencies output from 73a and 73b are combined by an adder circuit 74, and the output is converted into one balanced signal by a transformer 75, and then mixed with the output of an amplifier 77 by a mixer circuit. There is a demand for a circuit that combines two unbalanced signals and converts the unbalanced signals into one balanced signal.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a balun transformer having a signal multiplexing or demultiplexing function as well as a balanced signal-unbalanced signal conversion function.

[0007]

To achieve the above object, a balun transformer according to the present invention comprises a first unbalanced transmission line, a second unbalanced transmission line, and the first unbalanced transmission line and the second unbalanced transmission line. One unbalanced transmission line and one balanced transmission line electromagnetically coupled to the unbalanced transmission line are provided. For example, a stacked balun transformer includes a first strip line forming a first unbalanced transmission line, a second strip line forming a second unbalanced transmission line, the first unbalanced transmission line, and a second strip line. A second balanced transmission line that is electromagnetically coupled to each of the two unbalanced transmission lines, and a plurality of dielectric layers; and the first, second, third, and fourth strip lines. A laminate is formed by stacking the strip line and the dielectric layer.

[0008]

With the above arrangement, the first unbalanced transmission line and the second unbalanced transmission line are electromagnetically coupled to the balanced transmission line, respectively, and input to the first unbalanced transmission line and the second unbalanced transmission line, respectively. The obtained unbalanced signal is multiplexed by a balanced transmission line, converted to a balanced signal, and output. Conversely, the balanced signal input to the balanced transmission line is split by the first unbalanced transmission line and the second unbalanced transmission line, converted to an unbalanced signal, and output.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a balun transformer according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a circuit configuration of an embodiment of a balun transformer according to the present invention. The balun transformer 20 includes two unbalanced transmission lines 15 and 16 and one balanced transmission line 1.
7 is provided. One end of the unbalanced transmission line 15 is connected to the unbalanced signal terminal 11, and the other end is open. One end of the unbalanced transmission line 16 is connected to the unbalanced signal terminal 12, and the other end is open. These unbalanced transmission lines 1
5, 16 are line portions L11,
L12 and line portions L15 and L16. A balanced transmission line 17 is provided between the unbalanced transmission lines 15 and 16. The balanced transmission line 17 includes a pair of line portions L1.
3, L14. Each of the line portions L13 and L14 has one end connected to the ground, and the other end connected to the balanced signal terminals 13a and 13b.

Each of the line portions L11 and L12 has an electrical length corresponding to a quarter wavelength of the applied center frequency of the unbalanced signal S1 input / output to / from the unbalanced signal terminal 11.
Similarly, the line portions L15 and L16 are connected to the unbalanced signal terminal 1
1 of the applied center frequency of the unbalanced signal S2 input / output to / from the
Each has an electrical length corresponding to ４ wavelength. On the other hand, the electrical length of the line portions L13 and L14 is
11, L12 and the line portions L15, L16 are compared to match the longer electrical length.

The balun transformer 20 has an unbalanced signal terminal 1
1 and 12, respectively, the unbalanced signal S1 and the unbalanced signal S2.
Are input, these unbalanced signals S1 and S2 propagate through the unbalanced transmission lines 15 and 16, are multiplexed by the balanced transmission line 17, and are converted into the balanced signal S3. The balanced signal S3 is output from between the balanced signal terminals 13a and 13b. Conversely, the balanced signal S3 is supplied to the balanced signal terminals 13a and 13b.
Is input, the balanced signal S3 propagates through the balanced transmission line 17, and is split into unbalanced signals S1 and S2 by the unbalanced transmission lines 15 and 16. This unbalanced signal S1,
S2 is output from the unbalanced signal terminal 11 and the unbalanced signal terminal 12, respectively. Thus, the balun transformer 20
Is used, two unbalanced signals can be combined into one balanced signal, and conversely, one balanced signal can be separated into two unbalanced signals.

FIG. 2 is an exploded perspective view of an example of the laminated balun transformer 20 having the circuit configuration of FIG. As shown in FIG. 2, the multilayer balun transformer 20 includes a dielectric sheet 21 provided on the surface with a strip line 150 constituting the unbalanced transmission line 15 of FIG. 1, and an unbalanced transmission line 16 of FIG.
1, a dielectric sheet 24 provided with strip lines 170 and 171 constituting the balanced transmission line 17 shown in FIG. 1 on the surface, and extraction electrodes 31, 37 and 38. , 35 provided on the surface, and the dielectric sheet 2 provided on the surface with ground electrodes 33, 36, respectively.
3, 28, etc. Dielectric sheets 21 to 28
As a material for the above, a resin such as epoxy or a ceramic dielectric is used.

The strip lines 150 and 160 have line portions L11 and L12 and line portions L15 and L16 connected in series, respectively. The line portions L11 and L12 have a spiral shape and have a length corresponding to a quarter wavelength of the unbalanced signal S1 propagating through the strip line 150. Similarly, the line portions L15 and L16 have a spiral shape, and have a length corresponding to a quarter wavelength of the unbalanced signal S2 propagating through the strip line 160.

The strip lines 170 and 171 have line portions L13 and L14, respectively. This line section L1
Each of L3 and L14 has a spiral shape, and the length thereof is set to be longer than the lengths of the line portions L11 and L12 and the line portions L15 and L16. In the present embodiment, the length of the line portions L11 and L12 is equal to the length of the line portions L15 and L1.
6 is designed to be longer than the line section L1.
The lengths of L3 and L14 are set equal to the lengths of the line portions L11 and L12. One end 170a, 171a of each of the strip lines 170, 171 is
4 is exposed at the left and right sides of the center of the back side.

The line portions L11 and L13 and the line portion L12
And L14 are formed to face each other with the sheet 21 interposed therebetween. Accordingly, the line portions L11 and L13 and the line portions L12 and L14 are electromagnetically coupled, respectively. Similarly, the line portions L13 and L15 and the line portions L14 and L16
Are formed so as to face each other with the sheets 24 and 25 interposed therebetween. Therefore, the line portions L13 and L15 and the line portions L14 and L16 are electromagnetically coupled, respectively.

The extraction electrode 31 has one end 31a exposed at a position on the left side of the center of the front side of the sheet 22,
The other end 31b is electrically connected to one end 150a of the strip line 150 on the line portion L11 side via a via hole 32a provided in the sheet 22. One end 37 a of the extraction electrode 37 is exposed to the left side of the near side of the sheet 25, and the other end 37 b is a via hole 32 provided in the sheet 24.
b, it is electrically connected to the other end 170b of the strip line 170. The extraction electrode 38 is connected to one end 3
8a is exposed to the right side of the near side of the sheet 25, and the other end 38b is electrically connected to the other end 171b of the strip line 171 via the via hole 32c provided in the sheet 24. One end 35a of the extraction electrode 35 is exposed at a position on the right side of the center of the front side of the sheet 27, and the other end 35b is connected to the line portion L15 of the strip line 160 via a via hole 32d provided in the sheet 26. One end of
0a. Strip line 150,
160, the other ends 150b, 16 on the side of the line portions L12, L16.
0b is open.

The ground electrode 33 is provided on substantially the entire upper surface of the sheet 23, and the lead portions 33a and 33b are exposed to the left and right sides of the near side, respectively.
c and 33d are respectively exposed on the left and right sides of the back side. The ground electrode 36 is provided on substantially the entire upper surface of the sheet 28, and the lead portions 36a, 36b are exposed to the left and right sides of the near side, respectively, and the lead portions 36c, 3
6d are exposed on the left and right sides of the back side, respectively. These ground electrodes 33 and 36 are connected to the strip lines 150 and 16 in consideration of the characteristics of the balun transformer 20.
It is desirable to be located at a predetermined distance from 0, 170, 171. Extraction electrodes 31, 35, 3
7, 38, strip lines 150, 160, 170,
The 171 and the ground electrodes 33 and 36 are formed by a method such as a sputtering method, a vapor deposition method, and a printing method.
It is made of a material such as d, Ag, Pd, and Cu.

Each of the sheets 21 to 28 is stacked and baked integrally to form a laminate 3 as shown in FIG.
9 is assumed. Unbalanced signal terminals 11 and 12 and ground terminals G1 and G2 are formed on the front side surface of the laminate 39, and balanced signal terminals 13a and 13b and ground terminals G3 and G4 are formed on the rear side surface. . Terminals 11-1
3b, G1 to G4 are formed by a method such as a sputtering method, a vapor deposition method, a coating method, and the like, and Ag-Pd, Ag, Pd,
It consists of materials, such as Cu and Cu alloy.

The unbalanced signal terminal 11 is electrically connected to the end 31a of the extraction electrode 31, the unbalanced signal terminal 12 is electrically connected to the end 35a of the extraction electrode 35, and the ground terminal G1 is connected to the extraction electrode 37. The ground terminal G2 is electrically connected to the end 38a of the extraction electrode 38 and the ends 33b, 36b of the ground electrodes 33, 36. The balanced signal terminals 13a, 13b are connected to the ends 170a, 17 of the strip lines 170, 171, respectively.
1a, the ground terminals G3 and G4 are connected to the ends 33c and 36c of the ground electrodes 33 and 36, respectively.
33d and 36d are electrically connected.

When the electrical characteristics of the balun transformer 20 are adjusted, the thickness of the dielectric sheets 21 and 25 and the line width of the strip lines 150, 160, 170 and 171 are changed to change the electromagnetic characteristics between the line portions L11 and L13. Join,
The electromagnetic coupling between the line portions L12 and L14, the electromagnetic coupling between the line portions L13 and L15, and the electromagnetic coupling between the line portions L14 and L16 can be adjusted.

The balun transformer according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention. For example, the shape of the strip line constituting the balanced and unbalanced transmission line is arbitrary, and may be a meandering shape, a linear shape, or the like in addition to the spiral shape. Also, the line section does not necessarily need to be set to an electrical length of 1/4 wavelength.

Although the above embodiment has been described taking the case of individual products as an example, in the case of mass production, a mother board provided with a plurality of balun transformers is manufactured, cut into a desired size, and cut into a desired size. I do. Furthermore, in the above-described embodiment, the dielectric sheets on which the conductors are formed are stacked and then integrally fired, but the present invention is not necessarily limited to this. The sheet which has been baked in advance may be used. Further, the balun transformer may be manufactured by a manufacturing method described below. After a paste-like dielectric material is applied by printing or the like to form a dielectric layer, a paste-like conductor material is applied to the surface of the dielectric layer to form an arbitrary conductor.
Next, a paste-like dielectric material is applied over the conductor. A balun transformer having a laminated structure can be obtained by successively coating in this manner.

[0024]

As is clear from the above description, according to the present invention, when the first unbalanced signal and the second unbalanced signal are input, the first unbalanced signal and the second unbalanced signal are changed. It is multiplexed and converted into a balanced signal and output. Conversely,
When a balanced signal is input, it is split into a first unbalanced signal and a second unbalanced signal and output. Accordingly, multiplexing and demultiplexing can be performed in addition to the mutual conversion between the balanced and unbalanced signals transmitted.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram showing an embodiment of a balun transformer according to the present invention.

FIG. 2 is an exploded perspective view of a multilayer balun transformer having the circuit configuration of FIG. 1;

FIG. 3 is an external perspective view of the multilayer balun transformer shown in FIG. 2;

FIG. 4 is an equivalent circuit diagram of a conventional balun transformer.

FIG. 5 is an electric circuit diagram for combining two unbalanced signals and converting them into one balanced signal.

[Explanation of symbols]

 15, 16 unbalanced transmission line 17 balanced transmission line 20 balun transformer 21-28 dielectric sheet 39 laminate 150, 160, 170, 171 strip line L11-L14 line section

Claims (2)

[Claims] A first unbalanced transmission line, a second unbalanced transmission line, and a single balanced transmission line electromagnetically coupled to the first unbalanced transmission line and the second unbalanced transmission line, respectively. A balun transformer. 2. A first strip line forming a first unbalanced transmission line and a second strip line forming a second unbalanced transmission line.
And third and fourth strip lines constituting one balanced transmission line electromagnetically coupled to the first unbalanced transmission line and the second unbalanced transmission line, respectively.
A balun transformer comprising a plurality of dielectric layers, wherein the first, second, third, and fourth strip lines and the dielectric layers are stacked to form a laminate.