JPH04280101A - Directional coupler - Google Patents

Abstract

PURPOSE:To improve the directivity by using a folded strip line as a connection strip line connecting two coupling parts so as to reduce the capacitive coupling between the microstrip line and the connection use microstrip line. CONSTITUTION:Two coupling parts C1, C2 branching part of microwave power by the capacitive coupling between a folded strip line T and a connection use strip line formed on a dielectric board are provided apart by a 1/4 wavelength of the microwave and the coupling parts are interconnected by a connection strip line. In the directional coupler having the constitution as above, since the connection strip line S is folded, the distance between the strip line T through which a microwave is sent and the connection strip line S is increased as l as shown in figure. Thus, the leakage of the microwave due to the capacitive coupling between the strip line T and the connection strip line S is reduced and the directivity of the directional coupling is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional coupler composed of a strip line with improved directionality.

0002

2. Description of the Related Art The structure of a directional coupler formed from a conventional microstrip line formed on a dielectric substrate will be explained with reference to FIG.

T is a microstrip line formed on a dielectric substrate for transmitting microwaves, and C1 and C2 are installed at a distance of one quarter wavelength of the microwaves transmitted by this microstrip line T. A part of the microwave power transmitted by capacitive coupling is branched. S is a microstrip line for connection to configure a directional coupler, and J1, J2
is the output terminal.

Now, when a microwave is transmitted to the microstrip line T from the direction shown by arrow A in the figure, a part of this microwave is branched at the coupling part C1 and transmitted through the connecting microstrip line S in the opposite direction. side joint C2
Since the phase of the microwave that has reached this point and the microwave branched at this coupling portion C2 are equal, these microwaves are combined and output from the output terminal J2.

However, the microwave branched at the coupling part C1 and the microwave transmitted by the microstrip line T, branched at the coupling part C2, passed through the connecting microstrip line S, and reached the coupling part C1. Since the phases differ by 180 degrees, these microwaves cancel each other out and are not output from the output terminal J1.

[0006] Also, an arrow B is shown on the microstrip line T.
When microwaves are transmitted from the direction indicated by arrow A, the branched microwaves are output from output terminal J1, but not from output terminal J2, contrary to the case where microwaves are transmitted from the direction indicated by arrow A above. is not output.

[0007]

[Problems to be Solved by the Invention] A directional coupler formed using a conventional microstrip line as described above has a connection that connects two coupling parts C1 and C2 that branch microwaves from a microstrip line T. A microstrip line S was provided close to the microstrip line T, which is the main microwave transmission line.

Therefore, the microwaves on the microstrip line T and the microwaves on the connecting strip line S are coupled together due to capacitive coupling between the microstrip line T and the connecting strip line S. For example, when microwaves are transmitted from the direction indicated by arrow A to the microstrip line T in FIG. It will be transmitted on the connection strip line S.

As a result, the phase difference between the microwave branched at the coupling part C1 and the microwave arriving via the microstrip line T, the coupling part C2 and the connecting strip line S does not become 180 degrees at the coupling part C1. Therefore, there is a problem that microwaves are also output from the output terminal J1, and the directionality of the directional coupler is not good.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved directional coupler that reduces capacitive coupling between a microstrip line and a connecting microstrip line and improves directivity.

[0011]

[Means for Solving the Problems] As shown in the principle diagram of the present invention in FIG.
Coupling portions C1 and C2 were provided separated by a quarter wavelength of the microwave, and these coupling portions were connected by a bent connecting strip line S.

0012

[Operation] In the directional coupler of the present invention having the above-described configuration, since the connecting strip line S is bent, the distance between the strip line T through which microwaves are transmitted and the connecting strip line S is reduced. can be increased as shown by l in the figure, and the leakage of microwaves due to capacitive coupling between these strip lines T and the connecting strip line S is significantly reduced. can be improved.

[0013]

Embodiment An embodiment of the present invention will be described with reference to FIG. In FIG. 2, components corresponding to those shown in FIGS. 1 and 2 are designated by the same reference numerals, and their explanations will be omitted.

[0014] R is a terminating resistor, G is an earth land,
The microwave power output from the output terminal J1 is absorbed by the terminating resistor R, one end of which is grounded by connection to the earth land G, and the microwave is transmitted from the left end of the microstrip line T in the direction indicated by arrow A. is output from the right end of this line T as shown by arrow A1, and is also output from the right end output terminal J2 of connection microstrip line S as shown by arrow A2.

In this configuration, the microwave input from the terminal marked with arrow A1 of the microstrip line T due to reflection from the antenna, for example, is transmitted to the left end output terminal J1 of the connecting microstrip line S.
is absorbed by the terminating resistor R.

According to the present invention, since the connecting microstrip line S is bent, there is little leakage of microwaves due to capacitive coupling between the microstrip line T and the connecting microstrip line S, which improves the directionality. As mentioned above, this is a significant improvement.

[0017]

[Effects of the Invention] As explained above, since a bent stripline is used as a connection stripline that connects two coupling parts, a microstrip line that is the main transmission path of microwaves and a microstrip for this connection can be connected to each other. The special effect of increasing the distance from the lines and reducing the capacitive coupling between them and improving the directionality of the directional coupler can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing a conventional example.

[Explanation of symbols]

T Microstrip line C1, C2
Connection part S Bent connection strip line J
1, J2 Output terminal R Terminal resistor G Earth land

Claims (1)

[Claims] Claim 1: A strip line formed on a dielectric substrate and two coupling parts that branch part of the microwave power by capacitive coupling are provided at a distance of one quarter wavelength of the microwave, and these coupling parts are separated by a quarter wavelength of the microwave. A directional coupler characterized in that the two are connected by a bent connection strip line.