JPS6047762B2 - directional coupler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a directional coupler that has a simple configuration, good directionality, and can be tightly coupled.

Generally, the length of the coupling line for a directional coupler is λg/
4, and the following conditions are required in order to improve directionality or obtain a degree of close coupling. (
Here, λg is the tube wavelength. ) Condition 1: In order to improve directivity, the effective dielectric constants Eodd and Eeven of the odd mode and even mode of the coupled line are made equal.

Condition 2: In order to obtain tight coupling, the impedances of the odd mode and even mode of the coupled line are set as Zodd and Ven, respectively.
When , Zodd/Zeven is made smaller.

FIG. 1a is a configuration plan view showing an example of a conventional directional coupler, and FIG. 1 is a sectional view taken along line AA' in FIG. 1a.
FIG. 1c is a sectional view taken along line BB' in FIG. 1a(7).

The main structure of this directional coupler is that an internal conductor consisting of a main line 2 and a coupled line 3 is formed on one side of a dielectric substrate 1, and a ground conductor 4 is formed on the other side. .

With such a configuration, a directional coupler can be realized extremely easily.

However, the disadvantage of this directional coupler is that it cannot satisfy conditions 1 and 2 above, so the directionality is poor and the degree of coupling is -
The limit was 6 dB, and tight coupling could not be achieved. In order to improve these drawbacks, the following directional couplers have been devised.

FIG. 2a is a configuration plan view showing an example of a conventional directional coupler, FIG. 2 is a sectional view taken along line A-A' (7) in FIG. a(7) BB' sectional view.

The main structure of this directional coupler is that an internal conductor consisting of a main line 2 and a coupled line 3 is formed on one side of a dielectric substrate 1, a ground conductor 4 is formed on the other side, and a coupled line is formed on the other side. A coupling auxiliary conductor 6 is mounted on top of the conductor 3 with a dielectric layer 5 interposed therebetween. With this configuration, the dielectric layer 5 and the coupling auxiliary conductor 6 mainly act on the odd mode of the coupling line 3, so conditions 1 and 2 above can be satisfied, and the directionality is good. A directional coupler capable of tight coupling has been realized. However, the disadvantage of this directional coupling five coupler is that it has a very complicated structure and is therefore difficult to implement. That is, the conventional directional coupler can satisfy the conditions 1 and 2 above without complicating the configuration.In addition, the dielectric layer 5 and the coupling auxiliary conductor 6 simply connect the odd mode of the coupled line 3. Since it only acts on the target, there is little freedom in design and it is not practical.

In order to eliminate these drawbacks, the present invention provides an air layer and a coupling auxiliary conductor between the dielectric substrate and the other conductor, and will be described below with reference to the drawings.

FIG. 3a is a plan view of the configuration of a directional coupler according to an embodiment of the present invention, FIG. 3b is a sectional view taken along line A-A'' in FIG. It is a B-B'' sectional view of figure a. The main structure of the directional coupler of the present invention is that an internal conductor consisting of a main line 2 and a coupled line 3 is formed on one side of a dielectric substrate 1, and an internal conductor consisting of a main line 2 and a coupled line 3 is formed on the other side through an air layer 7. Further, a coupling auxiliary conductor 6 is formed at the interface between the dielectric substrate 1 and the air layer 7 below the coupling line. With this configuration, the drawbacks of conventional directional couplers can be eliminated, and a directional coupler with a simple configuration, good directionality, tight coupling, and a high degree of freedom in design can be realized. .

These reasons will be explained below. FIGS. 4A and 4B show the electric field distributions of the odd mode and even mode in the coupled line 3 taken along the line B-B'' in FIG. 3.

Here, FIG. 4a shows the odd mode, and FIG. 4b shows the even mode.

As can be seen from these figures, the coupled auxiliary conductor 6 mainly acts on the odd mode of the coupled line 3, and the air layer 7 mainly acts on the coupled line 3.
It is acting on the even mode of . From this, it is possible to satisfy conditions 1 and 2 above by appropriately selecting the dimensions of the coupling auxiliary conductor 6, the thickness of the air layer 7, etc., and to create a directional coupler with good directionality and a high degree of coupling. It can be achieved.

Unlike conventional directional couplers, the directional coupler according to the present invention can be realized with a simple structure because the coupling line 3 and the coupling auxiliary conductor 6 are formed on the upper and lower surfaces of a single dielectric substrate 1. Furthermore, since the coupling auxiliary conductor 6 and the air layer 7 act separately on the odd mode and even mode of the coupling line 3, there is a degree of freedom in design, and this is very practical.

Although the MIC type directional coupler has been described above, the present invention may also be used in a triplate type directional coupler.

As described above, according to the present invention, by providing the coupling auxiliary conductor 6 and the air layer 7 between the dielectric substrate 1 and the other conductor 4, it is possible to achieve a simple structure, good directionality, and tight coupling. A directional coupler can be realized, which is advantageous in terms of practical application due to the degree of freedom in design.

[Brief explanation of the drawing]

Fig. 1a is a configuration plan view showing an example of a conventional directional coupler, Fig. 1b is a sectional view taken along line A-A'' in Fig. 1a (7), Fig. 1c
1A (7) B-B'' sectional view, FIG. 2A is a structural plan view showing another example of a conventional directional coupler, and FIG. 2B is a cross-sectional view of FIG. 2A (7) A- A″ sectional view, Figure 2c is the same as Figure 2a (7
) B-B" cross-sectional view, FIG. 3 a is a structural plan view showing an embodiment of the present invention, FIG. 3 b is a cross-sectional view taken along FIG. 3 a (7) A-N,
Figure 3c is a sectional view taken along line B-B'' in Figure 3a, and Figures 4A and b are diagrams showing the electric field distributions of odd and even modes in the coupled line section at line B-B'' in Figure 3a, respectively. There is. In the figure, 1 is a dielectric substrate, 2 is a main line, 3 is a coupling line, and 4
5 is another conductor, 5 is a dielectric layer, 6 is a coupling auxiliary conductor, and 7 is an air layer.

Claims (1)

[Claims] 1. In a directional coupler in which an internal conductor consisting of a main line and a coupled line is formed on one side of a dielectric substrate and another conductor is formed on the other side, the connection between the dielectric substrate and the other conductor is A directional coupler characterized in that an air layer is provided at the bottom of the coupling line, and a coupling auxiliary conductor is formed at the interface between the dielectric substrate and the air layer below the coupling line.