JPH03296304A - Directional coupler - Google Patents

Abstract

PURPOSE:To constitute the directive coupler of a microstrip circuit by arranging a conductor line whose length is not in excess of 1/4 wavelength to the edge coupled part of a 1/4 wavelength part being at least part of plural sections connected in cascade in a floating state. CONSTITUTION:Sections S1-S3 constitute semi-reentrant coupling are provided respectively with a floating conductor 10. The floating conductor 10 is provided to cover a gap over the edge of both conductors 5, 6 on the edge coupled part of the conductors 5, 6 of each section. Moreover, the floating conductor 10 is provided to each section separately respectively. That is, the length of the floating conductor 10 is selected not in excess of 1/4 wavelength so that each of the floating conductor 10 of each section is not in electric contact with each other among the sections S1-S3. Thus, the resonance is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a directional coupler, and particularly to a directional coupler constituted by a microstrip line.

[Prior Art] Conventionally, there are microwave directional couplers of the type shown in FIGS. 2A and 3A.

The directional coupler shown in FIG. 2A uses a strip line, and is constructed by connecting four sections of quarter-wavelength coupled lines in series. This directional coupler is 1/4
The conductors 25 and 26 constituting the wavelength coupled line are
As shown in the figure, it is constructed by disposing dielectrics 27a on different faces, dielectrics 27b and 27c on both sides, and grounding conductors 28 and 29 on the outside, forming a so-called broadside coupled line. It consists of Note that an input port 21 is provided at one end of the conductor 25, and an output port 24 is provided at the other end. Further, a coupling port 22 is provided at one end of the conductor 26, and an isolation port 23 is provided at the other end.
is provided.

The directional coupler shown in FIG. 3A uses a microstrip line, and is constructed by connecting two sections of quarter-wavelength coupled lines in series.

This directional coupler has conductors 35 and 36 forming a 1/4 wavelength coupling line, as shown in FIG. 3B.

It is arranged on a dielectric material 37, and this is arranged on a ground conductor 38, thereby forming a so-called edge-coupled line.

Note that the input port 31 is provided at one end of the conductor 35, and the output port 34 is provided at the other end. Further, a coupling port 32 is provided at one end of the conductor 36, and an isolation port 33 is provided at the other end.

[Problems to be Solved by the Invention] In recent years, microwave circuits have been increasingly integrated into integrated circuits. In addition, in order to accommodate various uses,
Broadband technology is being developed.

However, the above-mentioned conventional technology has the following problems in the flow of microwave circuit technology.

That is, the directional coupler shown in FIG. 2A can achieve close coupling, but the conductors 25 and 26 forming the 1/4 wavelength coupled line are arranged with the dielectric 27a sandwiched between them as shown in FIG. 2B. They are not on the same plane, and each requires a corresponding ground conductor. Therefore, it cannot be applied to a microstrip circuit in which conductors are arranged on the same plane, and therefore it is difficult to integrate the circuit. Another problem is that it is difficult to connect to other microstrip circuits.

On the other hand, the directional coupler shown in FIG. 3A is a microstrip line and can be easily integrated into an integrated circuit. but,
Since the degree of coupling is low, it is difficult to create multiple sections, and there is a limit to the bandwidth that can be achieved, making it impossible to achieve a wide band.

SUMMARY OF THE INVENTION An object of the present invention is to provide a directional coupler that can be constructed using a microstrip circuit, has a high degree of coupling, and can achieve a wide band.

[Means for Solving the Problems] The present invention has been made by focusing on semi-reentrant coupling in which the degree of coupling increases when a conductor is placed in a floating state at the coupling portion of an edge-coupled line.

That is, the present invention provides a directional coupler in which a plurality of quarter-wavelength coupling lines are connected in series to perform edge coupling, and in which at least one of the plurality of sections arranged in series is
174 wavelengths at the edge coupling portion of the 74-wavelength coupling line, respectively.
It is characterized in that a conductor line with a length not exceeding the wavelength is arranged in a floating state.

The portion where the floating conductor is arranged constitutes a semi-reentrant coupling. When a floating conductor is placed in some of the sections, that section becomes a semi-reentrant connection, and the other sections form a conventional edge connection.

[Function] An edge-coupled directional coupler, which is constructed by connecting multiple sections of conductors constituting a quarter-wavelength coupled line in series on the same plane, has a low degree of coupling, but is easy to integrate into an integrated circuit. .

Therefore, in the present invention, the degree of edge bonding is strengthened by arranging the conductor in a floating state in the edge bonding portion. As a result, multi-sectioning can be easily performed, the bandwidth can be widened, and a wideband directional coupler can be realized.

As described above, since the degree of edge coupling can be increased, the directional coupler can be constructed from a microstrip circuit in which multiple sections of conductors constituting a 174-wavelength coupled line are connected in series on the same plane. can. In addition, the floating conductor does not require any electrical connection to the outside, and the connection to the outside as a directional coupler is made by each boat of the 174 wavelength coupling line provided on the same plane. Even if a floating conductor is provided, it can be treated in the same way as a conventional microstrip circuit. Therefore, it becomes possible to form an integrated circuit.

The reason why the degree of coupling is increased by using a floating conductor is as follows.

If the cross section of a directional coupled line is symmetrical,
It can be analyzed using the concepts of even mode and odd mode. That is, the floating conductor acts as a floating state for even mode and as a ground for odd mode. In the odd mode, the ground is formed by a floating conductor, so that the odd mode impedance becomes low.

On the other hand, even mode impedance does not change much. The degree of coupling increases as the difference in impedance between the odd mode and the even mode increases, so placing a floating conductor results in lowering the odd mode impedance and increasing the degree of coupling.

Note that for the yami-entrant connection, (J, A,
G., Malherbe & 1. E,Losch”D
irectional Couplers Using
Sem1-Re-Entrant Coupled L
ines” Microwave Jour,, pp12
1-128. Nov. 1987) as a 90" hybrid coupler.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B show the configuration of a first embodiment of the directional coupler of the present invention. FIG. 1A schematically shows the conductor pattern of the directional coupler of this embodiment. Also, 1B
The figure shows an example in which the cross-sectional structure is schematically shown in FIGS. 1A and 1B.
5 are connected in cascade, of which 3 sections 5L-8
3 as a semi-reentrant connection, and the other 2 sections S
4. S5 is edge-coupled.

Section 5L-S5 of the 1/4 wavelength coupled line includes two conductors 5 and 6 continuously provided across each section.
Consisted of. This conductor 5.6 is connected to each section 5.
In L-55, they are provided symmetrically, and the width W and the interval are formed to increase in the order of sections S1 to 85. Further, an input port 1 is provided on one end (section SL) side of the conductor 5, and a connector port 4 is provided on the other end (section S5) side.

On the other hand, a coupling port 2 is provided at one end (section S1) of the conductor 6, and an isolation port 3 is provided at the other end (section S5).

Section 5L constituting the above semi-reentrant connection
-83 are each provided with a floating conductor 10. This floating conductor 10 is provided on the edge joint portion of the conductors 5, 6 of each section, spanning the edges of the conductors 5, 6, and covering the gap therebetween. Also,
This floating conductor 10 has, for each section,
They are provided separately. That is, in order to prevent electrical contact between the sections 5L-53, the length of the sections does not exceed 1/4 wavelength. This prevents resonance.

The width of the floating conductor 10 is determined depending on the desired degree of coupling in each section. In this embodiment, the width of the conductor 10 in section S1 is the largest, and then in the order of sections S2 and S3. of course.

It is not limited to this.

The directional coupler of this embodiment has a laminated structure, as shown in FIG. 1B. That is, the conductors 5 and 6 are formed on one surface of the dielectric 8, the floating conductor 10 is formed at a corresponding position on the other surface, and the dielectric 8 is connected to the conductor 5.
, 6 are placed on the dielectric material 7 with the lower surface side. A ground conductor 9 is provided on the lower surface side of the dielectric 7.

For example, the dielectric material 8 has a dielectric constant of 2.1 and a thickness of 0.0.
51mm Teflon plate (manufactured by ROGER5).

Duroid 5890) can be used. Further, as the dielectric material 7, for example, the dielectric constant is 2.2 and the thickness is 0.
゜508mm Teflon plate (manufactured by ROGER5, D
uroid5880) can be used.

The conductors 5, 6 and the floating conductor 10 are each formed by an etching technique. That is, the target conductors 5, 6, floating conductors, input ports 1, . It is manufactured by forming each pattern of the port 4, the coupling boat 2, and the isolation boat 3.

The design specifications of the directional coupler of this example are shown in FIG. 1C.

In the figure, k is the degree of coupling, Zoe is the even mode impedance, Zoo is the odd mode impedance,
εre is the even mode dielectric constant.

fro is the odd mode dielectric constant. Further, Wl is the width of the floating conductor 10, W is the width of the conductors 5 and 6, and D is the distance between the conductors 5 and 6. In addition.

Wl, W, and D have a certain degree of freedom in design with respect to the degree of coupling k. That is, for the same k, various dimensions can be matched.

In the directional coupler of this embodiment configured as described above, the borrow sign input from input port 1 is output to output port 4, and is also output to coupling port 2 by coupling each section. Ru.

The characteristics of the directional coupler of this example are shown in FIGS. 1D and 1E.

In FIG. 1D, S41 indicates the passage characteristic from input port 1 to output port 4, and S21 indicates the coupling characteristic from the input port to the coupling boat. In addition, in the figure, solid lines indicate actually measured values, and broken lines indicate calculated values. Further, in FIG. 1E, Sll indicates an input reflection characteristic, and S31 indicates an isolation characteristic.

As shown in these figures, according to this embodiment, 2-1
In the 8GHz band, the coupling characteristic S21 is -6,5±Q, 5dB
, the input reflection characteristic Sll is -13 dB or more.

Furthermore, it can be seen that an isolation characteristic S31 of -12 dB or more can be obtained.

According to this embodiment, tight coupling can be obtained by semi-reentrant coupling, making it possible to widen the band. Furthermore, it can be manufactured in the same way as a microstrip line, and each boat is on the same plane, making it easy to connect to other microwave circuit elements.

FIG. 4A shows the configuration of a second embodiment of the directional coupler of the present invention. FIG. 4A schematically shows the conductor pattern of the directional coupler of this embodiment. Moreover, FIG. 4B schematically shows the cross-sectional structure.

This embodiment is an example of a two-section directional coupler. That is, as shown in FIG. 4A, sections S1 and S2 of a 174-wavelength coupling line are connected in cascade, with section S1 being semi-reentrant coupling and section S2 being edge coupling. Section S1 has a length of, for example, 13.23+u+, and section S2 has a length of, for example, 13.55+*+a. This length can be designed using a linear equation.

λ=VO/fO/[r] 22, vO: speed of light in vacuum fo=4Gf(z tr= (tre“5ro)” Sections S1 and S2 of the 1/4 wavelength coupled line are:
It is composed of two conductors 41 and 42 that are continuously provided across both sections. This conductor 41.42 is
Each section 51. In S2, symmetrically provided,
The width W thereof is formed so as to increase in the order of sections S1 to 82. The spacing between the conductors 41 and 42 is set equal in both sections SL and S2. Conductor 41
An input port is provided at one end (section S1), and an output port 4 is provided at the other end (section S2).
A coupling boat 2 is provided on the 1) side, and an isolation port 3 is provided on the other end (section S2) side.

Section S1 constituting the above Yami-entrant connection
are each provided with a floating conductor 43.

This floating conductor 43 is connected to the conductor 4 of each section.
1.42 is provided over the edges of both conductors 41.42 to cover the gap therebetween.

As shown in FIG. 4B, the directional coupler of this embodiment has a laminated structure like the first embodiment. That is, the floating conductor 43 is formed on one surface of the dielectric 45. Meanwhile, conductors 41 and 42 are formed on the dielectric 44. Then, the dielectric 4 is placed on the dielectric 44.
5 with the floating conductor 43 on the top side,
It is constructed by stacking the sections so that their positions match the positions of the corresponding sections S1. A ground conductor 46 is provided on the lower surface side of this dielectric 44 .

For example, the dielectric material 45 has a dielectric constant of 2.1 and a thickness of 0.
076+++m Teflon plate (manufactured by ROGER5).

Duroid 5890) can be used. Further, the dielectric material 44 has a dielectric constant of 1, for example, a dielectric constant of 2.2. Thickness 0
．． 508+u+ Teflon plate (manufactured by ROGER3).

Duroid 5880) can be used.

The conductors 41, 42 and the floating conductor 43 are each formed by the etching technique as in the first embodiment.

The design specifications of the directional coupler of this example are shown in FIG. 4C.

In the figure, k is the degree of coupling, Zoe is the even mode impedance, Zoo is the odd mode impedance,
εre is the even mode dielectric constant.

tro is the odd mode dielectric constant. In addition, Wl is the width of the floating conductor 43, W is the width of the conductor 41°42,
D is the spacing between conductors 41,42.

Note that Wl, W, and D have a certain degree of freedom in design with respect to the degree of coupling k, as in the case of the first embodiment.

In the directional coupler of this embodiment configured in this way, the signal input from input port 1 is as follows.

It is output to the output port 4 and also to the connection boat 2 by combining each section.

The characteristics of the directional coupler of this example are shown in FIG. 4D.

In FIG. 4D, S41 indicates the passage characteristic from input port 1 to output port 4, S21 indicates the coupling characteristic from the input port to the coupling port, S11 indicates the input reflection characteristic, and S31 indicates the isolation characteristic. As shown in the figure, according to this embodiment, in the 2-6Gl (z band), the coupling characteristic S21 is 16±
O,,5dB, input reflection characteristic Sll is -16dB or more,
Furthermore, it can be seen that an isolation characteristic S31 of -18 dB or more can be obtained.

This embodiment also provides the same effects as the first embodiment.

Next, the cascade connection of the semi-reentrant coupling lines described above is not limited to the above embodiment, and other applications are also possible.

Examples include a broadband 90'' hybrid coupler, a symmetrical directional coupler, a tapered directional coupler, and the like.

The one shown in FIG. 5 is an example of a broadband 90' hybrid coupler, in which a quarter-wavelength coupled line is formed using conductors 51 and 52 such that sections 5l-85 are symmetrically connected in series; A floating conductor 53 is arranged in the central section S3 to provide semi-reentrant coupling, and the other four sections are edge coupled.

Moreover, the one shown in FIG. 6 is an example of a tapered type directional coupler, which is configured to perform edge coupling using tapered conductors 61 and 62, and a triangular floating conductor is included in a part of the coupler. 63 is arranged to form a semi-reentrant connection, and the other parts are formed into an edge connection.

In each of the above-described embodiments, an overlay structure is employed in which a floating conductor is provided on the upper surface side of a 1/4 wavelength coupled line via a dielectric, but the present invention is not limited to this. That is, an underlay structure can be provided in which a floating conductor is provided on the lower surface side of the 1/4 wavelength coupled line with a dielectric interposed therebetween.

For example, if this structure is applied to the first embodiment, the first
The structure is such that the dielectrics 8 in Figure B are stacked upside down. That is, a dielectric 8 with a conductor 5.6 provided on one surface and a floating conductor 10 on the other surface is placed on a dielectric 7 having a ground conductor 9 on the back side, with the floating conductor 10 on the bottom side. It has a laminated structure.

With this configuration, the conductors 5 and 6 that make up the 174-wavelength coupled line appear on the top surface, giving the appearance the same structure as a conventional microstrip circuit, making connections with other microstrip circuits easier. , it becomes easier to realize integrated circuits.

[Effects of the Invention] As explained above, according to the present invention, it is possible to realize a directional coupler that can be configured with a microstrip circuit, has a high degree of coupling, and can achieve a wide band. be.

[Brief explanation of drawings]

FIG. 1A is a plan view schematically showing the configuration of the first embodiment of the directional coupler of the present invention, FIG. 1B is an A-A end view schematically showing its cross-sectional structure, and FIG. 1C is the above-mentioned A table showing design specifications of the directional coupler of the first embodiment, FIG. 1D and FIG.
Figure E is a graph showing the characteristics of the directional coupler of the first embodiment, Figure 2A is a plan view showing the configuration of a conventional directional coupler using a strip line, and Figure 2B is its cross-sectional structure. Figure 3A is a plan view showing the configuration of a conventional directional coupler using a microstrip line, Figure 3B is a CC end view showing its cross-sectional structure, and Figure 4A is a FIG. 4B is a plan view schematically showing the configuration of the second embodiment of the directional coupler of the present invention, FIG. 4B is a DD end view schematically showing its cross-sectional structure, and FIG. 4C is the second embodiment of the directional coupler of the present invention A table showing the design specifications of the directional coupler of the example, FIG. 4D is a graph showing the characteristics of the directional coupler of the second embodiment, and FIG.
The figure is a plan view showing an example of a broadband 90° hybrid coupler, and FIG. 6 is a plan view showing an example of a tapered directional coupler. 5L-55...section, 1...input port,
2... Coupling port, 3... Isolation port, 4... Roka port, 5.6... Conductor, 7, 8...
- Dielectric, 9... Ground conductor, 10... Floating conductor.

Claims (3)

[Claims] 1. A directional coupler that performs edge coupling by connecting multiple sections of 1/4 wavelength coupled lines in cascade, the edge coupling portions of the 1/4 wavelength coupled lines of at least some of the multiple sections being cascaded, each A directional coupler characterized in that a conductor having a length not exceeding 1/4 wavelength is arranged in a floating state. 2. A dielectric body having a ground conductor on the back side is provided with a conductor constituting a 1/4 wavelength coupled line of multiple sections on one surface, and a 1/4 wavelength coupled line of at least a portion of the multiple sections on the other surface. A directional coupler characterized by having a structure in which dielectrics each having a floating conductor provided at a position opposite to an edge-coupled portion of a conductor are laminated with the floating conductor facing downward. 3. A directional coupler that performs edge coupling by cascade-connecting a plurality of sections of 1/4-wavelength coupling lines, the directional coupler being characterized in that a part of the cascaded sections is a semi-reentrant coupling line. combiner.