JP2014165823A - Directional coupler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a directional coupler in which, even in the case where a coupling line impedance is made lower than a terminal impedance by restrictions in manufacture, the directivity is good.SOLUTION: A directional coupler has deletion parts 1106 provided in a ground conductor 1105 and arranged to be symmetrical to symmetry planes of a first signal conductor 1001 and a second signal conductor 1002, in a discontinuous structure having a function for delaying a phase and being smaller than a 1/4 wavelength of an operation frequency. Therefore, even in the case where a coupling line impedance is lower than a terminal impedance, in an even mode operation, the directional coupler is influenced by the deletion parts 1106 and the phase is delayed rather than the case where there is no deletion part 1106. In an odd mode operation, however, since the symmetry planes of the first signal conductor 1001 and the second signal conductor 1002 become electric walls, the directional coupler is not influenced by the deletion parts 1106 and a passing phase is not changed. Thus, a passing phase in the even mode operation and a passing phase in the odd mode operation can be matched, such that a directivity can be improved.

Description

  The present invention relates to a directional coupler used in the microwave band.

Directional couplers are widely used for power monitoring.
As a directional coupler, there is a configuration in which two parallel lines arranged in the same plane are brought close to each other (for example, see Non-Patent Document 1 below).
In this way, by arranging the lines close to each other, the two lines are electrically coupled, so that a directional coupler can be realized.

David M. Pozar, “Microwave Engineering-Second Edition” (pp. 384, John Wiley & Sons. Inc., published 1998).

However, the prior art has the following problems.
When a directional coupler is configured with a microstrip line, a coupled line that minimizes the reflection characteristics and isolation amount of the directional coupler and maximizes the coupling amount due to manufacturing restrictions such as substrate thickness and line width. The impedance may be lower than the terminal impedance connected to each terminal of the coupler.
When the coupled line impedance is lower than the termination impedance, the passing phase during the even mode operation advances more than the passing phase during the odd mode operation, so that a phase difference occurs during the even / odd mode operation and the directionality deteriorates. There are challenges.

  The present invention has been made to solve the above-described problems, and obtains a directional coupler with good directivity even when the coupled line impedance is lower than the termination impedance due to manufacturing restrictions. For the purpose.

  The directional coupler of the present invention includes a first signal conductor, a second signal conductor disposed in the same plane as the first signal conductor, and disposed in parallel with the first signal conductor, A ground conductor provided apart from the signal conductor and the second signal conductor and disposed parallel to a plane on which the first signal conductor and the second signal conductor are disposed; A reactance element having a discontinuous structure which is arranged so as to be symmetric with respect to the symmetry plane of the first signal conductor and the second signal conductor and has a function of delaying the phase and is small with respect to a quarter wavelength of the operating frequency; It is equipped with.

According to the present invention, the ground frequency conductor is disposed so as to be symmetrical with respect to the symmetry plane of the first signal conductor and the second signal conductor, and has a function of delaying the phase. A reactance element having a discontinuous structure small for four wavelengths was provided.
Therefore, even when the coupled line impedance is lower than the termination impedance, if a reactance element arranged so as to be symmetric with respect to the symmetry plane of the first signal conductor and the second signal conductor is provided, the reactance element is operated during even mode operation. The phase is delayed compared to the case where there is no reactance element due to the influence of the element. However, in the odd mode operation, the symmetry plane of the first signal conductor and the second signal conductor serves as an electric wall, so that the influence of the reactance element is exerted. Since the passing phase does not change, the passing phase in the even mode operation can be matched with the passing phase in the odd mode operation, so that the directionality can be improved.

It is a perspective view which shows the directional coupler by Embodiment 1 of this invention. FIG. 3 is a top perspective view showing the directional coupler according to Embodiment 1 of the present invention. It is sectional drawing which shows the A-A 'cross section of FIG. It is a perspective view which shows the conventional directional coupler. It is a top perspective view which shows the conventional directional coupler. It is sectional drawing which shows the A-A 'cross section of FIG. FIG. 10 is a top perspective view showing a conventional even / odd mode operation. It is a characteristic view which shows the passage phase with respect to the normalization frequency at the time of the even (100Ω) mode operation and the odd (25Ω) mode operation. It is a characteristic view which shows the passage phase with respect to the normalization frequency at the time of the even (80Ω) mode operation and the odd (20Ω) mode operation. FIG. 5 is a top perspective view showing the even / odd mode operation according to the first embodiment of the present invention. It is sectional drawing which shows the time of the odd mode operation | movement which assumed the B-B 'cross section in FIG. 10 as an electric wall. FIG. 11 is a circuit diagram illustrating an even mode operation assuming a B-B ′ cross section in FIG. 10 as a magnetic wall. It is a top perspective view which shows the other directional coupler by Embodiment 1 of this invention. It is sectional drawing which shows the A-A 'cross section of FIG. It is a top perspective view which shows the other directional coupler by Embodiment 1 of this invention. It is sectional drawing which shows the A-A 'cross section of FIG. 2 of the other directional coupler by Embodiment 1 of this invention. It is a top perspective view which shows the directional coupler by Embodiment 2 of this invention. It is sectional drawing which shows the A-A 'cross section of FIG. It is a top perspective view which shows the directional coupler by Embodiment 3 of this invention. It is sectional drawing which shows the A-A 'cross section of FIG.

Embodiment 1 FIG.
Hereinafter, preferred embodiments of a directional coupler according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

1 is a perspective view showing a directional coupler according to Embodiment 1. FIG.
In FIG. 1, 1000 is a dielectric substrate, 1001 is a first signal conductor provided on one surface of the dielectric substrate 1000, and 1002 is a second signal conductor provided on one surface of the dielectric substrate 1000. is there.
Reference numeral 1101 denotes a first input / output terminal provided on the first signal conductor 1001, and 1102 denotes a second input / output terminal provided on the first signal conductor 1001.
Reference numeral 1103 denotes a third input / output terminal provided on the second signal conductor 1002, and reference numeral 1104 denotes a fourth input / output terminal provided on the second signal conductor 1002.
Reference numeral 1105 denotes a ground conductor provided on the other surface of the dielectric substrate 1000.

2 is a top perspective view showing the directional coupler according to Embodiment 1, and FIG. 3 is a cross-sectional view showing the AA ′ cross section of FIG.
2 and 3, reference numeral 1106 denotes a deletion unit in which a part of the ground conductor 1105 is deleted.
Note that the length of each side of the deletion unit 1106 is sufficiently smaller than 1/4 of the free space wavelength at the operating frequency, for example, 1/10 wavelength or less.
1 to 3, the first signal conductor 1001 and the second signal conductor 1002 are arranged in parallel to form a side coupling portion.

In the directional coupler according to the first embodiment, even / odd mode analysis can be applied because it is symmetric in the BB ′ cross section in FIG.
FIG. 10 shows a top view when the BB ′ cross section in FIG. 2 is a magnetic wall / electric wall, that is, in an even / odd mode operation.
A cross section BB ′ in FIG. 10 becomes a magnetic wall during the even mode operation and an electric wall during the odd mode operation.

FIG. 4 is a perspective view showing a conventional directional coupler.
In FIG. 4, 9000 is a dielectric substrate, 9001 is a first signal conductor provided on one surface of the dielectric substrate 9000, and 9002 is a second signal conductor provided on one surface of the dielectric substrate 9000. is there.
Reference numeral 9101 denotes a first input / output terminal provided on the first signal conductor 9001, and 9102 denotes a second input / output terminal provided on the first signal conductor 9001.
9103 is a third input / output terminal provided on the second signal conductor 9002, 9104 is a fourth input / output terminal provided on the second signal conductor 9002, and 9105 is on the other surface of the dielectric substrate 9000. It is a ground conductor provided.

FIG. 5 is a top perspective view showing a conventional directional coupler, and FIG. 6 is a cross-sectional view showing an AA ′ cross section of FIG.
4 to 6, the first signal conductor 9001 and the second signal conductor 9002 are arranged in parallel to form a side coupling portion.

In the conventional directional coupler, even / odd mode analysis can be applied because it is symmetric in the BB ′ section in FIG.
FIG. 7 shows a top view when the BB ′ cross section in FIG. 5 is a magnetic wall / electric wall, that is, in an even / odd mode operation.
A cross section BB ′ in FIG. 7 becomes a magnetic wall during the even mode operation and an electric wall during the odd mode operation.

The impedance of the line in the side coupling part in the even mode operation with the BB ′ cross section as the magnetic wall is Z ′ _e , and the impedance of the line in the side coupling part in the odd mode operation with the BB ′ cross section as the electric wall. Assuming Z ′ _O , the coupled line impedance Z ′ is expressed by the following equation (1).

Further, assuming that the reflection characteristic during the even mode operation is S _11e , the _transmission characteristic is S _21e , the reflection characteristic during the odd mode operation is S _11o , and the _transmission characteristic is S _21o , the directional coupler reflection characteristic S 11 and the transmission characteristic S 21. The coupling characteristic S31 and the isolation characteristic S41 are expressed by the following equations (2) to (5), respectively.

Further, the directionality D is calculated by the following equation (6), and a directional coupler having a larger value becomes a directional coupler having better directionality.

By designing the side coupling portion so that the coupled line impedance Z ′ represented by the equation (1) becomes equal to the terminal impedance Z _{O of} the first input / output terminal 9101 to the fourth input / output terminal 9104, The amount of coupling can be maximized while minimizing the reflection characteristic and the amount of isolation of the directional coupler.

FIG. 8 shows the case where the impedance Z ′ _e of the line during the even mode operation is 100Ω, the coupled line length is 30 degrees, and the terminal impedance of the first input / output terminal 9101 and the second input / output terminal 9102 is 50Ω. The passing phase from the first input / output terminal 9101 to the second input / output terminal 9102, the impedance Z ′ _O of the line in the odd mode operation is 25Ω, the coupled line length is 30 degrees, the first input / output terminal 9101 and the second A calculation example of the passing phase from the first input / output terminal 9101 to the second input / output terminal 9102 when the terminal impedance of the second input / output terminal 9102 is 50Ω is shown.

  In this case, from equation (1), the coupled line impedance is 50Ω, which is the same as the termination impedance of the input / output terminal, so that the passing phases in the even / odd mode operation match as shown in FIG. The amount of passage during even / odd mode operation also matches.

Although the isolation characteristic can be obtained by equation (5), since the amplitudes of S _21e and S _21o are the same and the passing phase is the same, the isolation characteristic of the directional coupling coupler using the coupled line of this condition is used. Can be seen to be minimal.

However, the coupled line impedance may not be equal to the termination impedance due to manufacturing restrictions such as substrate thickness and line width.
For example, it is assumed that the line width cannot be reduced due to manufacturing restrictions, and the impedance Z ′ _e / Z ′ _O during even / odd mode operation is 80Ω / 20Ω, respectively.
The coupled line impedance at this time is 40Ω from the equation (1).
On the other hand, since the impedance of the circuit connected before and after the directional coupler is generally 50Ω, the termination impedance of the directional coupler at this time is 50Ω.

FIG. 9 shows a calculation example of the passing phase from the first input / output terminal 9101 to the second input / output terminal 9102.
Since the coupled line length is short, the amplitudes of the passages S _21e / S _21o at the time of even / odd mode operation are almost the same. However, as shown in FIG. It will be later than the passing phase, and the passing phase difference will increase.

From this and equation (5), in the conventional directional coupler, when the coupled line impedance is lower than the termination impedance connected to each terminal of the coupler due to manufacturing restrictions, the operation in the even / odd mode operation is performed. Since the passages (S _21e / S _21o ) do not cancel each other, there is a problem that the amount of isolation increases and the directionality deteriorates.

On the other hand, in the directional coupler according to the first embodiment, the ground conductor 1105 is provided with a deletion unit 1106 that operates as a reactance element.
The reactance element is an element that has an effect of delaying the passing phase of a signal passing through the reactance element, as compared with a normal straight line having no reactance element.
In the first embodiment, this reactance element is provided in a part of the ground conductor 1105 by the deletion unit 1106 having a function of delaying the phase and having a discontinuous structure sufficiently small with respect to a quarter wavelength of the operating frequency. Realize.
FIG. 11 shows a circuit in an even mode operation in the directional coupler according to the first embodiment, assuming that the BB ′ cross section in FIG. 10 is a magnetic wall.

As shown in FIG. 11, the current flowing through the ground conductor 1105 flows so as to bypass the deletion unit 1106.
For this reason, in the directional coupler according to the first embodiment, it is possible to delay the passing phase during the even mode operation of the conventional directional coupler.
That is, the deletion unit 1106 operates as a reactance element.

FIG. 12 shows the electric field distribution in the DD ′ section during the odd mode operation assuming that the BB ′ section in FIG. 10 is an electric wall.
In the odd mode operation of the directional coupler according to the first embodiment, as shown in FIG. 12, the cross section B serving as the first signal conductor 1001 and the electric wall is larger than the distance between the first signal conductor 1001 and the ground conductor 1105. -B 'is determined so that the interval is closer.
Thus, the electric field emitted from the first signal conductor 1001 exists only between the first signal conductor 1001 and the electric wall in the DD ′ section.
For this reason, since the passing phase of the place where the ground conductor 1105 exists under the first signal conductor 1001 and the passing phase of the place where the deletion portion 1106 exists under the first signal conductor 1001 are the same, The passing phase in the odd mode operation in the directional coupler of Embodiment 1 is the same as the passing phase when there is no reactance element.

That is, the deletion unit 1106 delays the passing phase during the even mode operation, but does not change the passing phase during the odd mode operation.
Accordingly, even when the coupled line impedance is lower than the termination impedance, the size of the deletion unit 1106 is determined so that the passing phase during the even mode operation matches the passing phase during the odd mode operation, thereby allowing the even / odd mode. Passing during operation cancels each other, and isolation characteristics can be improved.
Therefore, by forming the deletion portion 1106 in the ground conductor 1105, the direction of the directional coupler can be reduced even when the coupled line impedance is lower than the termination impedance connected to each terminal of the coupler due to manufacturing restrictions. Can improve sex.

  In addition, although the deletion part 1106 in Embodiment 1 was made into the rectangle, it is not restricted to this, If it is a symmetrical shape with respect to the symmetry plane of the 1st signal conductor 1001 and the 2nd signal conductor 1002, Good.

In the first embodiment, the deletion unit 1106 is used as the reactance element. However, the present invention is not limited to this, and the floating conductor 1107 may be arranged inside the deletion unit 1106 as shown in FIGS. good.
FIG. 13 is a top perspective view showing another directional coupler according to Embodiment 1, and FIG. 14 is a cross-sectional view showing the AA ′ cross section of FIG.

  During the even mode operation, the floating conductor 1107 is connected to the magnetic wall, so that there is no electrical influence on the directional coupler. However, during the odd mode operation, the floating conductor 1107 is connected to the electric wall. Therefore, it operates as a ground conductor.

For this reason, in order to delay the passage phase at the time of even mode operation | movement largely, when the deletion part 1106 is enlarged, the cross section used as the 1st signal conductor 1001 and an electrical wall rather than the space | interval of the 1st signal conductor 1001 and the ground conductor 1105 Even when the interval BB ′ cannot be made closer, a current also flows through the floating conductor 1107 during the odd mode operation, so that the influence of the deletion unit 1106 can be reduced. / It becomes easy to match the passing phase during odd mode operation.
That is, by arranging the floating conductor 1107 in addition to the deletion unit 1106, even when the coupled line impedance is lower than the terminal impedance connected to each terminal of the coupler due to manufacturing restrictions, the direction having good directivity is obtained. The sex coupler can be designed easily.

In the directional coupler according to Embodiment 1, one deletion unit 1106 is arranged. However, the present invention is not limited to this, and a plurality of deletion units may be arranged as shown in FIG.
FIG. 15 is a top perspective view showing another directional coupler according to the first embodiment. In the figure, reference numerals 1106 a, 1106 b, and 1106 c are deleted portions formed on the ground conductor 1105.
By adopting this configuration, it becomes easy to match the passing phase during the even / odd mode operation, so that the design becomes easy.

In the first embodiment, the second signal conductor 1002 is arranged on the first signal conductor 1001 and b on the surface layer of the dielectric substrate 1000. However, the present invention is not limited to this. AA in FIG. 'The first signal conductor 1001 and the second signal conductor 1002 may be arranged inside the dielectric substrate 1000 so that the cross section becomes a cross section as shown in FIG.
By adopting this configuration, the effective dielectric constant of the directional coupler is increased, so that the size can be reduced.

As described above, according to the first embodiment, the ground conductor 1105 is disposed so as to be symmetric with respect to the symmetry plane of the first signal conductor 1001 and the second signal conductor 1002, and the phase The deletion unit 1106 having a discontinuous structure small with respect to a quarter wavelength of the operating frequency having a function of delaying the delay time is provided.
Therefore, even when the coupled line impedance is lower than the termination impedance, if the deletion unit 1106 arranged to be symmetric with respect to the symmetry plane of the first signal conductor 1001 and the second signal conductor 1002 is provided, the even mode The operation is affected by the deletion unit 1106 during operation, and the phase is delayed as compared with the case where there is no deletion unit 1106. However, during the odd mode operation, the symmetry plane of the first signal conductor 1001 and the second signal conductor 1002 becomes an electrical wall. Since the passing phase does not change without being affected by the deletion unit 1106, the passing phase during the even mode operation and the passing phase during the odd mode operation can be matched, and thus the directionality can be improved.

According to the first embodiment, the reactance element is configured by the deletion unit 1106 from which a part of the ground conductor 1105 is deleted.
Therefore, the reactance element can be easily configured by the deletion unit 1106 from which a part of the ground conductor 1105 is deleted.

According to the first embodiment, the floating conductor 1107 disposed in the same plane as the ground conductor 1105 and provided in the deletion unit 1106 without contact with the ground conductor 1105 is provided.
Therefore, by adjusting the size and shape of the floating conductor 1107 in addition to the adjustment of the deletion unit 1106, the passing phases can be matched, and a directional coupler with good directivity can be easily designed.

According to the first embodiment, a plurality of deletion units 1106 are provided.
Therefore, it is possible to easily match the passing phases, and to easily design a directional coupler having good directivity.

Embodiment 2. FIG.
FIG. 17 is a top perspective view showing the directional coupler according to Embodiment 2, and FIG. 18 is a cross-sectional view showing the AA ′ cross section of FIG.
17 and 18, 1000 is a dielectric substrate, 1001 is a first signal conductor provided in the dielectric substrate 1000, and 1002 is provided on the same surface as the first signal conductor 1001 in the dielectric substrate 1000. A second signal conductor.
Further, reference numeral 1205a denotes a ground conductor provided on the upper surfaces of the first signal conductor 1001 and the second signal conductor 1002, and 1206a denotes a deleted portion thereof.
1205b is a ground conductor provided on the lower surface of the first signal conductor 1001 and the second signal conductor 1002, and 1206b is a deleted portion thereof.

Similar to the directional coupler according to the first embodiment, the directional coupler according to the second embodiment is affected by the deletion units 1206a and 1206b during the even mode operation, but the deletion unit 1206a during the odd mode operation. , 1206b.
In other words, the pass phase during even mode operation is delayed, but the pass phase during odd mode operation does not change, so even if the coupled line impedance is lower than the termination impedance, the pass phase during even mode operation and during odd mode operation By determining the sizes of the deletion units 1206a and 1206b so that the passage phases of each other coincide with each other, the passages during the even / odd mode operation cancel each other, and the directionality can be improved.
In addition, since the first signal conductor 1001 and the second signal conductor 1002 are configured to be sandwiched from the upper and lower surfaces by the ground conductor 1205a having the deletion portion 1206a and the ground conductor 1205b having the deletion portion 1206b, the passing phase is further facilitated. Therefore, it is possible to easily design a directional coupler having good directivity.

As described above, according to the second embodiment, the ground conductor having the deletion portion includes two ground conductors 1205a and 1205a, sandwiching the plane on which the first signal conductor 1001 and the second signal conductor 1002 are arranged. 1205b was placed.
Therefore, by arranging the ground conductors 1205a and 1205b having the deletion portions 1206a and 1206b across the first signal conductor 1001 and the second signal conductor 1002, the passing phases can be more easily matched. A directional coupler having good directivity can be easily designed.

Embodiment 3 FIG.
FIG. 19 is a top perspective view showing the directional coupler according to Embodiment 3, and FIG. 20 is a cross-sectional view showing the AA ′ cross section of FIG.
19 and 20, reference numeral 1000 denotes a dielectric substrate, 1001 denotes a first signal conductor provided on the upper surface of the dielectric substrate 1000, and 1002 denotes a second signal conductor provided on the upper surface of the dielectric substrate 1000. .
1305a to 1305d are ground conductors provided on the upper surface of the dielectric substrate 1000, 1306a is a deleted portion formed on the ground conductor 1305a surrounded by the first signal conductor 1001, and 1306b is a second signal conductor 1002. It is a deletion part formed in the enclosed ground conductor 1305b.

Similar to the directional coupler according to the first embodiment, the directional coupler according to the third embodiment is affected by the deletion units 1306a and 1306b during the even mode operation, but is deleted during the odd mode operation. , 1306b.
In other words, the pass phase during even mode operation is delayed, but the pass phase during odd mode operation does not change, so even if the coupled line impedance is lower than the termination impedance, the pass phase during even mode operation and during odd mode operation By determining the sizes of the deletion units 1306a and 1306b so that the passage phases of the two are matched, the passages during the even / odd mode operation cancel each other, and the directionality can be improved.
Since the ground conductor 1305a having the deletion portion 1306a and the ground conductor 1305b having the deletion portion 1306b are arranged in the same plane as the first signal conductor 1001 and the second signal conductor 1002, the directional coupling is performed. The vessel can be made thinner.

As described above, according to the third embodiment, the first signal conductor 1001 and the second signal conductor 1002 are arranged on the ground conductor 1305a having the deletion portion 1306a and the ground conductor 1305b having the deletion portion 1306b. Arranged in the same plane as the plane.
Therefore, a thin directional coupler can be obtained.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1000 dielectric substrate, 1001 first signal conductor, 1002 second signal conductor, 1101 first input / output terminal, 1102 second input / output terminal, 1103 third input / output terminal, 1104 fourth input / output terminal , 1105, 1205a, 1205b, 1305a to 1305d Ground conductor, 1106, 1106a, 1106b, 1106c, 1206a, 1206b, 1306a, 1306b Deleted portion, 1107 Floating conductor.

Claims (6)

A first signal conductor;
A second signal conductor disposed in the same plane as the first signal conductor and disposed parallel to the first signal conductor;
A ground conductor provided apart from the first signal conductor and the second signal conductor and disposed parallel to a plane on which the first signal conductor and the second signal conductor are disposed;
Provided to the ground conductor and arranged to be symmetric with respect to the symmetry plane of the first signal conductor and the second signal conductor, and has a function of delaying the phase to a quarter wavelength. On the other hand, a reactance element having a small discontinuous structure;
Directional coupler with The reactance element is
The directional coupler according to claim 1, wherein the directional coupler is configured by a deletion unit in which a part of the ground conductor is deleted. The reactance element is
A deleted portion obtained by deleting a part of the ground conductor;
A floating conductor disposed in the same plane as the ground conductor and provided in the deleted portion in a non-contact manner with the ground conductor;
The directional coupler according to claim 1, further comprising: The reactance element is
The directional coupler according to any one of claims 1 to 3, wherein at least two or more are provided. The ground conductor having the reactance element is:
5. The ground conductor according to claim 1, wherein two ground conductors are disposed so as to sandwich a plane on which the first signal conductor and the second signal conductor are disposed. Directional coupler. The ground conductor having the reactance element is:
5. The directional coupler according to claim 1, wherein the directional coupler is disposed on a same plane as a plane on which the first signal conductor and the second signal conductor are disposed. .

Images