JP3021337B2 - Directional coupler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional coupler which can be used in the field of radio equipment such as portable telephones and automobile telephones, and various other communication equipments. The present invention relates to a directional coupler which is a surface mount component.

[0002]

2. Description of the Related Art Generally, a directional coupler is a circuit having four or more input / output terminals, and is used to detect a level at which a signal input / output to / from a directional coupler passes in one direction. For example, as shown in the equivalent circuit diagram of the directional coupler in FIG. 9, two strip lines form a first coupling line (main line) and a second coupling line (sub-line). When a signal is input to the input terminal of the first coupling line and the signal is output from the output terminal (1), the coupling degree set from the first coupling line is output to the output terminal (2) of the second coupling line. Power is generated according to However, no power is generated at the output terminal (3) at this time. In an actual circuit, when a signal is input from the input terminal of the directional coupler, a part of the signal output from the output terminal (1) is reflected by an input unit or the like of a subsequent circuit, and the reflected signal is output in a direction. The power is re-entered from the output terminal (1) of the sex coupler, and power is generated at the output terminal (3) according to the degree of coupling set between the first and second coupling lines by the reflected signal. However, no power is generated at the output terminal (2) at this time. Therefore, the power of the output terminal (2) outputs only the power corresponding to the degree of coupling set between the first and second coupling lines by the signal input from the input terminal of the directional coupler. Because
This indicates the function of detecting the unidirectional power of the signal passing through the directional coupler.

Usually, when a directional coupler is used in a circuit, the line impedance of the first and second coupling lines is set to 50Ω, and the output terminal (3) has a 50Ω resistor whose other end is grounded. Is added. The items representing the performance of the directional coupler include a signal input from the input terminal in a state where a resistance of 50Ω is added to the output terminal (3) in FIG. 9, and an output through the first coupling line. The loss that occurs when the signal is output from the terminal (1) is “insertion loss”, and the power appearing at the output terminal (2) with respect to the signal passing through the first coupling line from the input terminal is “coupling degree”. The minute power appearing at the output terminal (2) with respect to the signal input from the terminal (1), passing through the first coupling line, and output from the input terminal is called "isolation". Further, the difference between the "coupling degree" and the "isolation" is called "directivity", and is an index of one-way detection capability for a signal passing through a directional coupler. The "coupling degree" is determined by the distance between the first and second coupling lines. If the distance between the first and second coupling lines is short, the coupling is tight, and if the distance is large, the coupling is loose. Also,
When the length of the first and second coupling lines is about １ ／ wavelength with respect to the target frequency band, the directional coupler can obtain a large isolation in the frequency band.

FIG. 10 is an external perspective view of a conventional laminated directional coupler 20, and FIG. 11 is an exploded perspective view. This laminated directional coupler 20 is composed of a laminate of dielectric layers 20-1 to 20-10, and each dielectric layer has a strip line 4-1 constituting a first coupling line (main line). 5-1; strip lines 7-1 to 8-1-1 constituting a second coupling line (sub line); ground electrodes 2-1 and 10-1; and through-hole electrodes 11 and 12 for connecting between layers. And lead portions 2 leading to the respective terminals from the first and second coupling lines and the ground electrode on the side surface of the laminated directional coupler 20 from each layer.
-2-2-3, 4-2 to 5-2, 7-2 to 8-2, 10-2
10-3 are provided. Further, terminal electrodes 1 </ b> A to 1 </ b> A for external connection are provided on side surfaces of the multilayer body of the multilayer directional coupler 20.
6A is provided.

More specifically, a dielectric layer 20-4 and a strip line 4-1 and a strip line 5-1 formed on the dielectric layer 20-5 are connected by a through-hole electrode 11 to form a first coupling line. (The main line), the dielectric layer 20-7 and the strip line 7-1 and the strip line 8-1 formed on the dielectric layer 20-8 are connected by the through-hole electrode 12, and the second coupling is performed. A line (sub line) is configured. Between these first and second coupling lines,
A dielectric layer 20-6 for adjusting the degree of coupling is inserted, and the ground electrode 2-1 and the ground electrode 10-1 are located outside the center in the stacking direction of the dielectric layers of the first and second coupling lines, They are formed on the dielectric layer 20-2 and the dielectric layer 20-10, respectively.

Furthermore, in order to adjust the input impedance of the first and second coupling lines to, for example, 50Ω, a dielectric for setting the distance between the strip line and the shield layer constituting the first and second coupling lines, respectively. Body layer 20-3
And a dielectric layer 20-9 are inserted. And the ground electrode 2-
1 is covered by the dielectric layer 20-1.

The above dielectric layers are laminated and integrated. Each of the strip lines and the ground electrode constituting the first and second coupling lines are connected to terminal electrodes 1A to 6A for external connection of the laminated directional coupler 20 from the side lead-out portion to each terminal. The ground electrode 2-1 and the ground electrode 10-1 are connected to the external electrode 2 by the side lead-out part 2-2 and the side lead-out part 10-2.
Connect to A. Also, it is connected to the external electrode 5A by the side surface lead portion 2-3 and the side surface lead portion 10-3. The first connection line is formed by the side surface deriving unit 5-2 and the side surface deriving unit 4-2.
The second coupling line is connected to the external connection electrode 1A and the external connection electrode 3A, respectively, and the second coupling line is connected to the external connection electrode 6A and the external connection electrode 4A by the side surface lead-out portion 7-2 and the side surface lead-out portion 8-2, respectively.

In the directional coupler as described above, the line length of the strip line serving as the coupling line is not set to １ ／ wavelength for the target frequency band.
For example, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-131111, a strip line is formed in a coil shape. This has the advantage that the conductor length of the strip line can be shorter than that of a directional coupler using a ス ト リ ッ プ wavelength strip line with respect to the target frequency band, and the directional coupler can be easily miniaturized. Further, since the first and second coupling lines are set to have substantially the same self-inductance, the first and second coupling lines are set up and down with respect to the center of the directional coupler 20 in the stacking direction. The coupling line, the dielectric layer, and the ground electrode may be substantially symmetrically stacked.
There was also a design advantage.

[0009]

On the other hand, with the miniaturization of such a directional coupler, the pattern area of the strip line constituting the coupling line becomes narrower. However, in order to satisfy the characteristics as a directional coupler, there arises a problem that it is difficult to secure a pattern region for patterning a strip line having a line length with which a sufficient self-inductance can be obtained. If the coupling line does not have sufficient self-inductance, the band in which large isolation is obtained shifts to the high frequency side. Therefore, when the frequency band to be designed is lower than the frequency band,
Sufficient isolation cannot be obtained in the target frequency band.

As a method of giving a sufficient self-inductance to the coupling line, it is conceivable to reduce the line width of the coupling line. However, when the electrode width of the coupling line is reduced, the actual resistance component of each line increases, so that the signal insertion loss increases. When the directional coupler is used in a high-frequency circuit of a portable device such as a mobile phone, the directional coupler is used for detecting the output power level of the transmission amplifier after the transmission amplifier. In this case, the high power amplified by the transmission amplifier is used. Since a signal (for example, about 1 W) passes through the directional coupler, an increase in insertion loss occurs for the amplified high-power signal. The portable communication device needs to drive the transmission amplifier so as to be able to transmit the power of the signal of the level to be set, which causes an increase in current consumption of the portable communication device. This increase in current consumption is an important problem in securing a long talk time, especially for a battery-powered portable communication device having a transmission amplifier that consumes a large amount of current.
When an attenuation amount such as an insertion loss occurs for a large power signal and a small power signal, when the attenuation amount is treated as a logarithm (dB), they are expressed by the same amount of change, but the absolute value of the amount of change ( The (exponential number) is an order of magnitude larger for the large power signal and the small power signal, and is larger for the large power signal.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem, to realize both miniaturization and low insertion loss of a directional coupler, and to realize sufficient isolation.

[0012]

In order to solve the above problems, a directional coupler according to the present invention comprises first and second coupling lines formed with a dielectric layer interposed between the first and second coupling lines. A first and a second ground electrode, which are disposed with a dielectric layer circumscribing the coupling line and the first and second coupling lines, respectively, and cover substantially the entire surface thereof; The second connection line is characterized in that the first connection line has a wider line width, a shorter line length, or a combination thereof as compared with the second connection line.

Further, the directional coupler of the present invention comprises a first and a second coupling line formed with a dielectric layer interposed between the first and second coupling lines.
And a first and second ground electrode disposed on both sides of a dielectric layer circumscribing the first and second connection lines and covering substantially the entire surface of the first and second connection lines, respectively. The self-inductance in the first and second coupling lines is characterized in that the self-inductance of the first coupling line is smaller than that of the second coupling line.

In the directional coupler of the present invention, each of the first and second coupling lines is preferably formed over two or more dielectric layers. In the present invention, it is preferable that the first and second connection lines have a spiral shape, a helical shape, or a combination thereof.

(Operation) FIG. 5 shows an equivalent circuit diagram for explaining the principle of the directional coupler of the present invention, and FIG. 6 shows an equivalent circuit diagram close to an actual circuit. In the directional coupler of the present invention, the length of the spiral strip line of the first coupling line (main line) through which the signal passes is determined by the spiral of the second coupling line (sub-line) where the signal appears due to inter-line coupling. The length is set shorter than the length of the strip line. In other words, when designing a directional coupler with a multilayer substrate as described with reference to FIG.
Since the area for designing the pattern of the coupling line becomes smaller as the size of the directional coupler becomes smaller, it becomes impossible to design the coupling line with sufficient self-inductance. To compensate for this, the line width of the spiral strip line of each coupling line is reduced. At this time, the line length of the spiral strip line on the side of the first coupling line (main line) through which a signal passes is set. Set short and second
The length of the spiral strip line of the connection line (sub line) is set to be longer than the spiral strip line of the first connection line (main line).

FIG. 7 is a cross-sectional view of the directional coupler showing an example of the arrangement relationship of the strip lines of the first and second coupling lines of the directional coupler of the present invention. By making each coupling line thinner as described above, an area where the spiral stripline can be patterned can be secured, and by making the line itself thinner, the self-inductance of the spiral stripline also increases. Furthermore, when designing a coupling line with a helical structure coil pattern, the area of the area surrounded by the coil conductor that circulates in the planar direction is substantially smaller when the coil conductor is narrower when the helical pattern is designed within the same patterning area. Since the coil can be designed widely, the self-inductance as a coil can be further increased.

The characteristics of the directional coupler of the present invention will be explained by calculation of an equivalent circuit shown in FIG. In FIG. 6, L1 is the self-inductance of the first connection line, L2 is the self-inductance of the second connection line, M is the mutual inductance between the first and second connection lines, and Co is the first connection line. Stray capacitance between the second coupling line and C1
Is the stray capacitance between the first coupling line and the ground electrode, C2 is the stray capacitance between the second coupling line and the ground electrode, and CP1 is the first capacitance.
Is the stray capacitance of the second coupling line itself, and CP2 is the stray capacitance of the second coupling line itself. Normally, a 50Ω resistor is connected to the output terminal (3) of the directional coupler in the form of being grounded as shown in FIG. In the present invention, the relationship of the self-inductance of each coupling line in FIG.
L2, but suppose that the directional coupler for the same frequency band as the directional coupler of the present invention is designed such that the self-inductance of each line (the inductance at that time is Lo) is almost equal to the conventional example. In this case, the relationship of the self-inductance of the first coupling line and the second coupling line in the present invention is such that L1 <Lo <L2 with respect to the inductance Lo at this time. As described above, the self-inductance of each coupling line changes in proportion to the conductor length when the conductor width of the strip line of each coupling line is the same. Therefore, due to the above-mentioned relationship of self-inductance, the conductor length in the first coupling line is shorter than in the conventional design, so even if the line width is reduced, the actual resistance component of the first coupling line does not increase. As a result, the insertion loss as a directional coupler does not increase. Further, depending on the conditions of the conductor length and conductor width of the main line, the insertion loss can be improved.

Next, regarding the isolation characteristics,
The length of the strip line of the second coupling line (sub-line) is adjusted while keeping the length of the strip line of the coupling line (main line) short as described above. In the present invention, it has been found that a band in which a large value can be obtained can be adjusted. FIG. 8 shows the situation. The graph in the figure shows the change in the isolation characteristics when the length of the first coupling line in the directional coupler is fixed and the length of the strip line is changed only for the second coupling line. I do.
In FIG. 8, when the first coupling line (main line) has the same line length as the second coupling line (sub line), the isolation band of -40 dB or less is a band of 1.2 to 2 GHz. By making the line length of the second coupling line (sub line) longer than that of one coupling line (main line), the isolation band can be reduced to a band of 1.2 GHz or less. That is, the directional coupler of the present invention increases the line length of the strip line of the second coupling line (sub-line) from the strip line of the first coupling line (main line), thereby increasing the isolation band. This shows that the directional coupler can be moved to the lower frequency side with more freedom than the conventional directional coupler. The first
And the line width of the strip line of the second coupling line is narrower than the conventional directional coupler design, but the line length of the strip line on the first coupling line (main line) side is as described above. Is shorter,
The insertion loss of the directional coupler does not need to be increased. However, the strip line of the second coupling line (sub-line) has a smaller line width and a longer line length than the conventional directional coupler design, so that the second coupling line (sub-line) is longer. The actual resistance component of the strip line itself is increasing. However, the power flowing through the second coupling line (sub-line) is about 15 to 25 dB lower than the power of the first coupling line (main line), and the output end (2) of the second coupling line (sub-line) The same power is not necessarily applied to the output terminal (3) and the output terminal (3) because of the above-described directivity relationship. Since the entire second coupling line (sub-line) only receives power in a small signal area in terms of power, it is portable. There is no problem that leads to significant power loss in circuits such as telephones. In addition, the actual increase in the loss amount is about 0.05 to 0.15 dB, and there is almost no problem in a small signal area.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, referring to FIG. 1 and FIG. 2, a directional coupler according to the first embodiment has a spiral shape of a plurality of dielectric layer green sheets 30-1 to 30-10 and a plurality of strip lines. 1 coupling line 4-
a, 5-a, spiral second connection lines 7-a, 8-a composed of a plurality of strip lines, and a plurality of ground electrodes 2-a, 10-a are laminated and fired. Integrated and formed. This directional coupler includes a plurality of lead portions 2-b, 2-c, 4-b, 5-b, 7-b that lead from each dielectric layer to terminals on the side of the stacked directional coupler.
A plurality of through-hole electrodes 15 and 16 for connecting b, 8-b, 10-b and 10-c to the strip lines between the layers are provided.

The dielectric layer 30-4, spiral strip lines 4-a and 5-a formed on the dielectric layer 30-5
Are connected by a through-hole electrode 15 to form a first coupling line (main line), and a dielectric layer 30-7, a dielectric layer 3
Spiral strip line formed on 0-8
a and 8-a are connected by a through-hole electrode 16, and the second
(Combination line). At this time, the spiral strip lines 4-a and 5-
The length obtained by adding a was set to be shorter than the length obtained by adding the spiral strip lines 7-a and 8-a of the second connection line. Further, the first and second coupling lines are opposed to each other at an arbitrary position in the stacking direction of the substrate without taking into account a specific arrangement such that, for example, the center of the spiral of each spiral strip line is matched. First,
No design was made for the direction in which the spiral strip line of the second coupling line turns or for patterning such that they run alongside each other.

A dielectric layer 30 for adjusting the degree of coupling is provided between the spiral strip lines of the first and second coupling lines.
-6 was inserted. Outside the center of the spiral strip line of the first coupling line in the stacking direction, ground electrodes 2-a and 10-a are connected to the dielectric layers 30-2 and 30-.
10 respectively. Further, in order to adjust the input impedance of each coupling line to 50Ω, dielectric layers 30-3 and 30-9 were inserted to set the distance between the spiral strip line of each coupling line and the ground electrode.

In the conventional example, since the spiral strip lines of each coupling line have substantially the same length, the dielectric layer can be designed with substantially the same thickness. Since the spiral strip line of the first coupling line (main line) is longer than the spiral strip line of the second coupling line (sub line), the thickness of the dielectric layer that sets the distance from the ground electrode Is set so that the dielectric layer 30-9 is thicker than the dielectric layer 30-3. Note that the thickness of the dielectric layer may be adjusted by adjusting the sheet thickness of the dielectric layer of each layer. Although not shown in the exploded perspective view of this embodiment (FIG. 1), it is also possible to adjust the thickness of the dielectric layer by inserting a plurality of dielectric layer sheets. And the ground electrode 2-a is
It is covered by the dielectric layer 30-1.

After the respective dielectric layers are laminated and fired, they are integrated as shown in FIG. The ground electrode and the first and second coupling lines each lead out an electrode on the side of the directional coupler. The ground electrodes 2-a and 10-a are connected to the external connection electrode 2B by the side surface lead portions 2-b and 10-b, and are connected to the external connection electrode 5B by the side surface lead portions 2-c and 10-c. In addition, the first connection line is a side derivation unit 5-
b and 4-b are connected to the external connection electrodes 1B and 3B, respectively, and the second coupling line is connected to the side lead-out portion 7-b
And 8-b were connected to the external connection electrodes 6B and 4B, respectively.

The length of the spiral strip line of the first coupling line (main line) of the directional coupler of this embodiment is 8.05 mm, and the length of the spiral strip line of the second coupling line (sub line) is The width was designed to be 12.95 mm and the width of each strip line was to be 0.15 mm. With this pattern, the shape of the directional coupler is 3.5 × 2.
It became 5 x 1.6 (mm). FIG. 3 shows the characteristics of the directional coupler. In terms of electrical performance, the insertion loss is 0.2 dB or less in the 1 GHz band, and the isolation is 40 in absolute value.
More than dB was obtained, and the directivity (difference between isolation and coupling degree) was more than 20 dB. Normally, as the size of the directional coupler is reduced, sufficient directivity tends not to be obtained. However, the above-mentioned performance can be said to be very good for this shape.

(Other Embodiments) The present invention can be implemented as follows. In the first embodiment, the shape of the coupling line on the input side (first) is designed in a spiral pattern, and the line length of the spiral strip line is used as a parameter. There is a problem in the magnitude of the self-inductance of the (first) coupling line. Therefore, in order to reduce the self-inductance, the coupling line on the input side (first) may have a helical pattern as shown in FIG. This input side (first) coupling line is formed by a plurality of dielectric layer green sheets 4.
0-1 to 40-2 and a helical first connection line including a plurality of strip lines 1 and 3 are formed by lamination. Further, a plurality of lead portions 2, 4 leading to terminals on the side of the directional coupler laminated from the respective dielectric layers, and a through-hole electrode 12 for connecting a strip line between the layers are provided. The helical strip lines 1 and 3 formed on the dielectric layers 40-1 and 40-2 are connected by the through-hole electrode 12, and constitute a first coupling line (main line). At this time, the length obtained by adding the helical strip lines 1 and 3 of the first connection line is shorter than the length of the second connection line so that the turning diameter and the number of turns of the strip line between each connection line are set. Can be changed.

A directional coupler may be designed by combining the first coupling line with a spiral type and a helical type.

The strip line of the coupling line on the input side is patterned over two layers in the embodiment, but it may be patterned over more layers.

[0028]

As described above, the present invention has the following effects.

(1) The insertion loss of the directional coupler can be improved.

(2) It is possible to lower the frequency of the isolation band of the directional coupler and obtain a large isolation.

(3) The above requirements can be satisfied, and the size of the directional coupler can be reduced.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a first embodiment of the present invention.

FIG. 2 is an external perspective view of the first embodiment of the present invention.

FIG. 3 is a characteristic diagram of the first embodiment of the present invention.

FIG. 4 is a pattern of a first connection line according to a second embodiment of the present invention.

FIG. 5 is a conceptual diagram of a directional coupler explaining the principle of the present invention.

FIG. 6 is an equivalent circuit diagram of a directional coupler explaining the principle of the present invention.

FIG. 7 is a cross-sectional view of a directional coupler illustrating the principle of the present invention.

FIG. 8 is a diagram showing a change in isolation when the length of a first coupling line of the directional coupler of the present invention is changed.

FIG. 9 is an exploded perspective view of a conventional directional coupler.

FIG. 10 is an equivalent circuit diagram of a conventional directional coupler.

FIG. 11 is an external perspective view of a conventional directional coupler.

[Explanation of symbols]

20, 30 Directional coupler 20-1 to 20-10, 30-1 to 30-10, 40-1 to
40-2 Dielectric Layers 4-1 5-1 4-1 4-a 5-a Spiral Strip Lines 7-1, 8-1, 7-a, 8-a Second Constituting First Coupling Line Spiral strip lines constituting the first coupling line 1, 3-1, Helical strip lines constituting the first coupling line 2-1, 10-1, 2-a, 10-a Ground electrode

Continuation of the front page (56) References JP-A-7-131211 (JP, A) JP-A-9-55608 (JP, A) JP-A-8-335809 (JP, A) JP-A-61-230510 (JP) JP-A-57-21102 (JP, A) JP-A-54-51445 (JP, A) JP-A-50-145051 (JP, A) JP-A 62-98213 (JP, U) JP-A 58-59205 (JP, U) JP44-21141 (JP, B1)

Claims (4)

(57) [Claims] 1. A main line and a main line formed with a dielectric layer interposed therebetween.
Beauty and binding line the secondary line, are disposed to sandwich the dielectric layer circumscribing respective coupling lines serving as the main line and the secondary line, the first covering substantially the entire surface
And a second ground electrode, wherein the coupling line serving as the main line and the sub line is a sub line.
The main line has a wider line width or a shorter line length than the main line , or a combination thereof. The self-inductance of the main line is L1, the self-inductance of the sub-line is L2, and the desired frequency band Main line and auxiliary line required in
And the self-inductance is L0.
A directional coupler having a relationship of L1 <L0 <L2 . 2. The directional coupler according to claim 1, wherein thicknesses of dielectric layers circumscribing the main line and the sub-line are different from each other. . 3. The directional coupler according to claim 1, wherein each of the coupling lines serving as the main line and the sub line is :
A directional coupler formed over two or more dielectric layers. 4. The directional coupler according to claim 1, wherein the coupling line serving as the main line and the sub line has a spiral shape, a helical shape, or a combination thereof. A directional coupler, comprising: