JPH0770889B2 - Directional coupler - Google Patents

Description

DETAILED DESCRIPTION [Outline] A distributed-coupling type directional coupler including a microstrip line, in which an input / output line and a coupling line are tightly coupled and a dielectric is used. A vertical conductor of the first, second, and third strip conductors, particularly the first strip conductor, which forms an input / output line on the front surface of the substrate, and a coupling conductor as a coupling line formed on the back surface of the electric substrate. Λ
Oppositely arranged and coupled over a length of g / 4.

[Industrial application field]

The present invention relates to an improvement of a distributed coupling type directional coupler used in a microwave band or the like, and more particularly to a tightly coupled directional coupler configured by a microstrip line, which is used for dividing / combining microwaves, Is widely used as a basic circuit such as a balanced modulator / demodulator and a mixer.

As a directional coupler of this type, it is desired that a coupling degree of about 3 dB be realized by a compact and low-cost microwave IC (integrated circuit).

[Conventional technology]

As the directional coupler in the microwave band, there are a branch line type using a microstrip line and a distributed coupling type, and the former branch line type is often used, but the circuit occupies a large area. Also, there is a drawback that the frequency band is narrow.

On the other hand, a distributed coupling type directional coupler does not have the above-mentioned drawbacks, but it is generally difficult to realize a tight coupling of about 3 dB by using edge coupling of a microstrip line.

However, the distributed-coupling type directional coupler having wide-band characteristics is extremely useful in practice, and efforts are being made to make it tightly coupled.

As a conventional distributed coupling type and tight coupling directional coupler, there are an A. tandem connection type and a B. interdigitated type shown in FIG.

The tandem connection type A is a directional coupler connected in two stages to realize a coupling degree of 3 dB as shown in the figure, and the interdigitated type B is an edge formed by dividing two coupled lines into two. This is a circuit in which the degree of coupling is increased by increasing the number of coupling sections.

[Problems to be solved by the invention]

In the conventional distributed-coupling type directional coupler described above, it is necessary to bridge the coupling lines between the tandem connection type A and the intermediate type B type by wire or ribbon conductors. There is a limit to conversion,
There is a problem that the substrate cannot be realized unless it is a dedicated thin film substrate, and the low-cost general-purpose printed circuit board dielectric substrate cannot be used.

[Means for solving problems]

According to the present invention, the above-mentioned problem is that the first and second partial conductors are formed on the surface of the dielectric substrate, and the vertical conductors and the first and second partial conductors are connected to both ends of the vertical conductors and are connected at substantially right angles in opposite directions. Of the strip conductor (1) and the vertical conductor of the first strip conductor (1) are spaced apart from each other at both ends and extend substantially collinearly in the opposite direction to the first and second partial conductors. On both sides of the input / output line formed by the existing second and third strip conductors (2, 3) and the vertical conductor of the first strip conductor (1), spaced apart in parallel, No. 2,
Two ground electrodes (5, 6) made of strip conductors are arranged inside the third strip conductors, and are opposed to the vertical conductors of the first strip conductors (1) on the back surface of the dielectric substrate. And includes both ends of the coupling conductor (4), which is made of strip conductors and is opposed to the ends of the second and third strip conductors, and the opposing positions of the two ground electrodes (5, 6). , A ground conductor (7) formed separately on the entire surface of each side is arranged, and each end of the coupling conductor (4) is provided with a through hole (8, 9) through the corresponding second and third portions.
Of the strip conductors (2, 3), and the two ground electrodes (5, 6) are connected to the ground conductor (7) through through holes (10 to 15), respectively. Is solved by a directional coupler.

[Action]

Coupling of the vertical conductors of the first, second, and third strip conductors 1, 2, 3 on the surface of the substrate, which are the input / output lines of the directional coupler, especially the first strip conductor 1, and the back surface of the substrate, which is the coupling line. Since the conductor and the conductor face each other across the constant length of the dielectric substrate, the coupling between the two can be easily made dense by adjusting the thickness of the substrate and the facing area. The microwave signal input from the input end of the first strip conductor is distributed and output to the output end of the first strip conductor 1 and the output end of the second strip conductor 2 due to the phase relationship. It is not output to the output terminal of the strip conductor 3 of No. 3.

Further, the ground electrodes 5 and 6 provided along both sides of the vertical conductor of the first strip conductor 1 on the front surface of the substrate are also connected to the ground conductor 7 on the rear surface.
Since they are connected symmetrically through through holes 10, 11, 12 and 13, 14, 15, the circuit is miniaturized while maintaining symmetry, and good directivity can be maintained in the high frequency band.

〔Example〕

FIG. 1 is a configuration diagram showing a configuration of a directional coupler according to an embodiment of the present invention, where A is a front view of the directional coupler configured by a microstrip line, B is a cross-sectional view, and C is a rear view. Is.

1, 2 and 3 are strip conductors that form the input / output lines on the surface of the dielectric substrate (100), of which 1 is the first strip conductor, which is a vertical conductor and opposite ends thereof as shown in the drawing. It is constituted by connecting the extending first and second partial conductors.

2 is a second strip conductor, the end of which is spaced apart from one end of the vertical conductor of the first strip conductor,
The first strip conductor is formed to extend substantially in the same line in the opposite direction to the first partial conductor.

3 is a third strip conductor, the end portion of which is spaced from the other end of the vertical conductor of the first strip conductor,
The first strip conductor is formed to extend substantially in the same line in the opposite direction to the second partial conductor.

5 and 6 are ground electrodes, which are made of strip conductors,
The strip conductors 1 are arranged parallel to each other on both sides of the vertical conductor and inside the first, second, and third strip conductors.

Reference numeral 4 denotes a coupling conductor composed of a strip conductor on the back surface of the substrate, which faces the first strip conductor and has both ends each having a first conductor.
The second and third strip conductors have a shape facing the corresponding ends of the strip conductors and form a coupled line.

Reference numeral 7 denotes a grounding conductor, which is formed on the entire surface of each side of the coupling conductor with a space therebetween.

In the directional coupler of the present embodiment, the length of the vertical conductor of the first strip conductor 1 serving as the input line on the surface of the substrate is about 1/4 of the effective wavelength λg of the microwave signal input to the circuit. The length of the coupling conductor 4 made of a strip conductor that is a coupling line facing the vertical conductor of the first strip conductor 1 on the front surface of the substrate is selected to be about 1/4 of the effective wavelength λg. To be done.

The ends of the coupling conductors 4 are through holes and the second and third strip conductors 2 and 3 on the surface of the substrate which are the output lines of the directional coupler.
Connected via 8,9.

In addition, the ground electrodes 5 and 6 made of strip conductors, which are the connection points with the external circuit on the surface of the board, respectively have through holes 10 and
It is symmetrically connected to the ground conductor 7 on the rear surface through 11,12 and 13,14,15.

Since the vertical conductor of the first strip conductor 1 and the coupling conductor 4 face each other across the length of λg / 4 across the dielectric substrate,
The microwave power input from the input terminal at one end of the first strip conductor 1 is transmitted through the vertical conductor of λg / 4 length on the front surface and goes to the output terminal at the other end, and at the same time, a part of the microwave power is transferred to the back surface. Is coupled to the coupling conductor 4 of FIG. However, as a result of the phase relationship, the combined output appears at the terminal, but not at the terminal.

Further, the vertical conductor of the first strip conductor 1 and the coupling conductor 4 are coupled to each other by tight coupling by appropriately selecting the thickness of the dielectric substrate between the strip conductors 1 and 4 and the width of each strip conductor. And a directional coupler with a coupling degree of 3 dB is easily realized.

〔The invention's effect〕

As described above, according to the present invention, there is an effect that a distributed coupling type tightly coupled microwave directional coupler configured of a microstrip line can be realized in a small size and at low cost.

[Brief description of drawings]

FIG. 1 is a structural diagram showing a configuration of a directional coupler of the present invention, and FIG. 2 is a structural diagram showing a configuration of a conventional directional coupler. In FIG. 1, 1 is a first strip conductor, 2,3 are second and third strip conductors, 4 is a coupling conductor as a coupling line, 5 and 6 are ground electrodes, 7 is a ground conductor, and 100 is a dielectric. Is the substrate

Claims (1)

[Claims] 1. A first strip made of a vertical conductor and first and second partial conductors connected to both ends of the vertical conductor in opposite directions at substantially right angles on the surface of a dielectric substrate. Both ends of the conductor (1) and the vertical conductor of the first strip conductor (1) are spaced apart from each other, and extend substantially in the same line in the opposite direction to the first and second partial conductors. The input / output line formed by the second and third strip conductors (2, 3) and both sides of the vertical conductor of the first strip conductor (1) are spaced apart and parallel to each other. Two ground electrodes (5, 6) made of strip conductors are arranged inside the second and third strip conductors, and the vertical conductor of the first strip conductor (1) is arranged on the back surface of the dielectric substrate. Located opposite to
Both ends include the combined conductor (4) made of strip conductors facing each other corresponding to the ends of the second and third strip conductors, and the facing positions of the two ground electrodes (5, 6). The ground conductor (7) formed separately is disposed on the entire surface of the side, and each end of the coupling conductor (4) has a through hole (8,
9) through corresponding second and third strip conductors (2,3)
The two ground electrodes (5, 6) are connected to the end of the through hole (10
To 15) are connected to the ground conductor (7) via a directional coupler.