JPH0426201A - Directional coupler - Google Patents

Abstract

PURPOSE:To obtain large coupling between two microstrip lines by setting the line length of a first strip conductor and the line length of a second strip conductor so as to be different each other in the coupling part of the strip conductors. CONSTITUTION:On a strip conductor 4a connecting the two bent parts of a strip conductor 4 formed on a dielectric substrate 1 and the dielectric substrate 1, a dielectric thin film 5 having width wider than that of the coupling part strip conductor 4a is formed. Next, a strip conductor 3 is formed on the dielectric thin film 5 and the dielectric substrate 1. In this case, a length between the two linear strip conductors extending from respective terminal parts 21 and 32 of the strip conductor 3, a line length l1 of a coupling part strip conductor 3a is set longer than a line length l2 of the coupling part strip conductor 4a as a length between the two linear strip conductors extending from respective terminal parts 22 and 24 of the strip conductor 4. Thus, the large amount of coupling can be obtained between the strip conductors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a directional coupler used in microwave bands and millimeter wave bands.

[Prior art] Fig. 7 shows a conventional 1/4 wavelength distribution coupling type directional coupler (
Hereinafter, this will be referred to as the first conventional example. ) is shown.

In FIG. 7, on a dielectric substrate 1 on which a ground conductor 2 is formed on the entire back surface, two strip conductors 3 and 4 each bent in a fold-back shape are separated from each other by a predetermined distance at a joint 10. They are formed facing each other by a length of λg/4. Here, the strip conductor 3 and the ground conductor 2 form a first microstrip line, and the strip conductor 4 and the ground conductor 2 form a second microstrip line.

In the directional coupler configured as described above, when a microwave signal is input between one end 21 of the strip conductor 3 and the ground conductor 2, the difference between the one end 22 of the strip conductor 4 and the ground conductor 2 and the strip conductor Microwave signals having a phase difference of 90 degrees and a power level lowered by 3 dB from the input power level are output between the other end 23 of 3 and the ground conductor 2, respectively. Note that the input microwave signal is not output between the other end 24 of the strip conductor 4 and the ground conductor 2.

In the first conventional directional coupler, when attempting to obtain a large amount of coupling between the two microstrip lines, the distance between the strip conductor 3 and the strip conductor 4 at the coupling portion 10 is reduced. There is a need. However, there is a problem in that it is very difficult to maintain the same spacing and reduce the spacing in terms of actual manufacturing.

In order to solve this problem, we developed a distributed coupling type directional coupler (hereinafter referred to as a second conventional example) which can obtain a large coupling amount and is easy to manufacture.

has been proposed in Japanese Patent Application Laid-Open No. 60-4306, and this directional coupler is shown in FIG.

In this @2 conventional example, WstI is placed on the strip conductor 4.
After forming the gold thin film 5, a strip conductor 3 is formed on the dielectric thin film 5 adjacent to the strip conductor 4.

In the second conventional example configured as described above, since the dielectric thin film 5 is provided at the joint 11 between the two strip conductors 3.4, the interval between the two strip conductors 3.4 is reduced. or connect the two strip conductors 3 and 4 to each other.
:x can be arranged side by side, which has the advantage that a large amount of binding can be obtained.

[Problem to be Solved by the Invention j However, in the second conventional example, since the two strip conductors 3 and 4 are in different states with respect to the ground conductor 2 in the joint portion 11, they are originally at 90 degrees. The problem is that the phase difference between the two output terminals forming the phase difference changes with the signal frequency, making it difficult to obtain a 90 degree phase difference at a desired frequency.

The purpose of the present invention is to solve the above-mentioned problems and provide a direction in which a predetermined phase difference can be obtained between the above-mentioned output terminals at a desired frequency, and a large amount of coupling can be obtained between two microstrip lines. The purpose is to provide a sexual coupler.

[Means for Solving the Problems] A directional coupler according to the present invention has a ground conductor formed on the back surface; a first strip conductor is formed on a dielectric substrate;
In a directional coupler, a dielectric film is formed on the first strip conductor, and a second strip conductor is formed on the dielectric film so as to be close to and electromagnetically coupled to the first strip conductor. , characterized in that the line length of the first strip conductor and the line length of the second strip conductor at the joint portion of the first strip conductor and the second strip conductor are set to be different from each other. .

[Function] According to experiments conducted by the present inventor, in a directional coupler configured as described above, when a microwave signal is inputted to one end of the first strip conductor, for example, the effects of other than the first strip conductor The phase difference between each microwave signal outputted to one end of the first strip conductor and one end of the second strip conductor is determined by the line length of the first strip conductor at the joint portion of the first strip conductor and the second strip conductor. It has been found that it is determined by the ratio of the line lengths of the second strip conductors.

Therefore, at a desired frequency, the phase difference between the microwave signals outputted to each of the output ends becomes a predetermined phase difference, so that the By adjusting and setting the line length of the first strip conductor and the line length of the second strip conductor, a directional coupler having a predetermined phase difference can be configured. Furthermore, in this directional coupler I, the first strip conductor and the second strip conductor are close to each other with the dielectric film interposed therebetween! Since they are formed so as to be magnetically coupled, a large amount of coupling can be obtained between the first strip conductor and the second strip conductor.

[Example] Hereinafter, an example according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a distributed coupling type directional coupler which is an embodiment of the present invention, and FIG.
Components that are the same as those in the figures are given the same reference numerals.

The directional coupler of this embodiment has a structure similar to that of the second conventional directional coupler shown in FIG.
The line length Q+ of the strip conductor 3a in the coupling part 1
It is characterized by being longer than the line length a of the strip conductor 4a in No. 3.

In FIG. 1, a strip conductor 4 bent in a U-shape is formed on a dielectric substrate l on which a ground conductor 2 is formed on the entire back surface, and then the two bent portions of the strip conductor 4 are A rectangular dielectric thin film 5 having a width larger than the width of the connecting strip conductor 4a is formed on the connecting strip conductor (hereinafter referred to as the connecting portion strip conductor) 4a and the dielectric substrate l. Next, the strip conductor 3 bent in a U-shape is placed on the dielectric thin film 5 and the dielectric substrate l, and the joint strip conductor 3a connecting the two bent portions of the strip conductor 3 is placed on the dielectric thin film 5 and the dielectric substrate l. The coupling portion strip conductor 4a is located close to and directly above the conductor 4a, and is overlapped with the coupling portion strip conductor 4a.

2, the line length Q1 of the joint strip conductor 3a, which is the length between the two linear strip conductors extending from each end 21, 23 of the strip conductor 3, is It is set to be longer than the line length ρ of the coupling portion strip conductor 4a, which is the length between two straight strip conductors extending from 22 and 24.

Here, in the coupling part I3, where the strip conductor 3 and the ground conductor 2 constitute a first microstrip line, and the strip conductor 4 and the ground conductor 2 constitute a second microstrip line, The wcl and the second microstrip line are electromagnetically coupled.

In the directional coupler configured as described above, when a microwave signal is input between one end 21 of the strip conductor 3 and the ground conductor 2, the difference between the one end 22 of the strip conductor 4 and the ground conductor 2 and the strip conductor Microwave signals having a certain phase difference are output between the other end 23 of the conductor 3 and the ground conductor 2, respectively. Note that the input microwave signal is not output between the strip conductor 24 and the ground conductor 2.

Now, connect the input end of the microwave signal to the stringo conductor 3.
For example, by fixing the line length C3 and increasing the line length Q1, the phase of the microwave signal output to the other end 23 of the strip conductor 3 can be changed to the end 221 of the string conductor 4. This can be delayed compared to the output microwave signal. Furthermore, by fixing the line length Q and increasing the line length Q2, the phase of the microwave signal output to the one end 22 of the strip conductor 4 can be changed to the phase of the microwave signal output to the one end 23 of the strip conductor 3. It can be delayed compared to the signal.

Therefore, in the directional coupler of this embodiment, by adjusting the line length Ql and the line length Q2, the phase difference between the microwave signals outputted to the respective output ends 22 and 23 at a certain desired frequency can be adjusted. can be adjusted.

FIG. 2 shows a distributed coupling type directional coupler which is a modification of this embodiment. In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals.

In this modification, the line length ρ1 is set smaller than the line length ρ2, and the coupling portion strip conductors 3a and 4a formed through the dielectric thin film 5 form the coupling portion 14.

First Experimental Example In the structure of the directional coupler of this example, the line length Q1 is fixed and the line length a is set as shown in FIGS. 3(A) to 3(E).
As shown in the figure, the line length Q varies from a value smaller than to a value larger than the line length Q, and in each case, the input end of the microwave signal is set to -@21 of the string conductor 3, and its output end is set to -@21 of the strip conductor 3. When the other end 23 and one end 22 of the string conductor 4 were used, the input end of the microwave signal was set as the one end 22 of the strip conductor 4, and its output end was set as the one end 21 of the strip conductor 3 and the other end 24 of the strip conductor 4. When the above line length Q.

The frequency at which the two strip conductors 3 and 4 are closely coupled and the phase difference between each output terminal were measured.

The measurement results are shown in FIG.

As is clear from FIG. 5, one end 2 of the strip conductor 5
When I is the input terminal, as the line length C2 is increased, the phase difference between each output terminal becomes smaller and changes from about 98 degrees to about 68 degrees. When the line length a is increased, the phase difference between each output terminal becomes larger, and becomes approximately 103
It varies from about 143 degrees to about 143 degrees. Furthermore, in any of the above cases, the frequency of close coupling becomes lower as the line length a becomes longer, and when the line lengths of the coupled strip conductors 3a and 4a are the same (Fig. 3(C) ),
(D) and (E)), the frequency of the close-packed coupling hardly changes.

Second Experimental Example In the structure of the directional coupler of this example, the line length Q is fixed and the line length Ql is set as shown in Figure 4 (A) to Figure 4 (E).
As shown in the figure, the line length changes from a smaller value to a larger value than the line length a2, and in each case, the input end of the microwave signal is one end 21 of the strip conductor 3, and the output end is the other end of the strip conductor 3. 23 and one end 22 of the strip conductor 4, and the input end of the microwave signal is the one end 22 of the strip conductor 4, and its output ends are one end 21 of the strip conductor 3 and the other end 24 of the strip conductor 4; At this time, the frequency at which the two strip conductors 3.4 were closely coupled for the above-mentioned line length of 12 degrees and the phase difference between each output terminal were measured.

The measurement results are shown in FIG.

As is clear from FIG. 6, one end 2 of the strip conductor 3
1 as the input end, as the line length ρ1 increases, the phase difference between the respective output ends increases and changes from about 71 degrees to about 93 degrees.

Further, when one end 22 of the strip conductor 4 is used as an input end, as the line length a1 is increased, the phase difference between each output end becomes smaller and changes from about 128 degrees to about 105 degrees. Furthermore, the frequency of close coupling becomes lower as the line length Q1 increases in any of the above cases,
When the line lengths of the connected strip conductors 3a and 4a are the same (4th cgJ (C), (D) and (E)
), the frequency of the close-packed coupling hardly changes.

From the above experimental results, we found the following.

(1) By changing the ratio between each line length 121 and a, the phase difference between the respective output terminals can be changed.

(2) The frequency of close coupling is determined depending on the line length of the coupled strip conductors 3a, 4a.

Therefore, as in the second conventional example, even if the line length g and Q2 are the same, if the phase difference does not reach the desired phase difference,
For example, in the case where the angle is not 90 degrees, each of the above line lengths Q
It becomes possible to adjust to a desired phase difference by changing Q1 and Q2 differently from each other.

As explained above, at a desired frequency, the line length 12° of the coupling portion strip conductor 3a and the line length ρ of the coupling portion strip conductor 4a are adjusted such that the phase difference between the respective output ends becomes a predetermined phase difference. , and the line length 12. are made different from each other. By setting 42 and a, it is easy to manufacture the two strip conductors 3 as in the second conventional example.
, 4, and has a predetermined phase difference at a desired frequency.

[Effect of the Invention 1] As detailed above, according to the present invention, in the second conventional directional coupler, the first strip conductor at the joint portion of the first strip conductor and the second string conductor Since the line length of the second strip conductor and the line length of the second strip conductor are set to be different from each other, the line length of the second strip conductor is set to be different from each other.
the first strip conductor at the joint portion of the first strip conductor and the second strip conductor so that the phase difference between the microwave signals outputted to each of the output terminals is a predetermined phase difference; By adjusting and setting the line length and the line length of the second strip conductor, a directional coupler having a predetermined phase difference can be configured. Furthermore, in this directional coupler, the first strip conductor and the second strip conductor are formed so as to be close to each other via the dielectric film and to be electromagnetically coupled.
There is an advantage in that a large amount of coupling can be obtained between the upper 29JI strip conductor and the second strip body.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a distributed coupling type directional coupler which is a one-cased embodiment of the present invention, FIG. A) to Fig. 3 (E) are respectively plan views of the distributed coupling type directional coupler of the experimental example of Hire 1, and Fig. 4 (A) to Fig. 4 (E) are the distribution of the second experimental example, respectively. A plan view of a coupled directional coupler, FIG. 5 is a graph showing the characteristics of the frequency of close coupling and the phase difference between each output terminal with respect to the length of the line below the coupling part in the first experimental example, Fig. 6 is a graph showing the characteristics of the frequency of close coupling and the phase difference between each output terminal with respect to the length of the line below the coupling part in the second experimental example, and Fig. 7 is a graph of the characteristics of the phase difference between the output terminals of the first conventional example. A perspective view of a quarter-wavelength distribution coupling type directional coupler. FIG. 8 is a perspective view of a second conventional distributed coupling type directional coupler. l...Dielectric substrate, 2...Ground conductor, 3.4...Strip conductor, 3a, 4a...Coupling portion strip conductor, 5...Dielectric thin film, 13.14...Coupling Part S,, a2...Line length of the strip conductor at the coupling part. Patent applicant: Murata Manufacturing Co., Ltd. Agent: Patent attorney: 1 person (see above) Figure 1 Figure 2 jI5 Figure 1.7 15.6 19.5 23.4 27:3 Lower 4.j /l)! pride 4 n + fz (mrnl
-1-Figure 6 1413 is the length of the canter slip 3? Force (mm) → Fig. 7 Fig. 8

Claims (1)

[Claims] (1) On the dielectric substrate with a ground conductor formed on the back side,
a dielectric film is formed on the first strip conductor, and a second strip conductor is formed on the dielectric film so as to be close to and electromagnetically coupled to the first strip conductor. In the formed directional coupler, the line length of the first strip conductor and the line length of the second strip conductor are set to be different from each other at the joint portion of the first strip conductor and the second strip conductor. A directional coupler characterized by: