JP3766554B2 - Directional coupler - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a directional coupler using a line conductor used for a mixer, a detector, a power amplifier or the like used in a microwave band and a millimeter wave band.
[0002]
[Prior art]
As a directional coupler using a line conductor such as a strip conductor used for a mixer, a detector, a power amplifier, etc. used in a microwave band and a millimeter wave band, a structure as shown in FIG. It has been known.
[0003]
FIG. 5 is a perspective view showing an example of the configuration of a conventional directional coupler. According to this directional coupler, two strip conductors 3 and 4 that are bent in the shape of a U and placed close to each other on the dielectric substrate 1 on which the ground conductor 2 is formed are connected to each other at the coupling portion. It is formed so as to be electromagnetically coupled at a predetermined interval.
[0004]
In order to obtain a large amount of coupling in such a directional coupler, it is necessary to reduce the distance between the coupling portions of the two strip conductors 3 and 4.
[0005]
[Problems to be solved by the invention]
However, in the directional coupler configured as shown in FIG. 5, it is very difficult to actually maintain and reduce the distance between the joint portions of the two strip conductors 3 and 4 in actual production. There was a problem that it was difficult to stably produce a product having good characteristics.
[0006]
In order to solve this problem, a directional coupler that can obtain a large coupling amount and is easy to manufacture is disclosed in, for example, Japanese Patent Laid-Open Nos. 60-4306 and 4-26201. A directional coupler configured as shown in a perspective view in FIG. 6 has been proposed.
[0007]
In the directional coupler shown in FIG. 6, 11 is a dielectric substrate, 12 is a ground conductor formed on the lower surface of the dielectric substrate 11, 13 is a first strip conductor formed on the dielectric substrate 11, and 14 is A thin film made of an insulator having a predetermined spread disposed on the first strip conductor 13, and 15 a second strip conductor arranged adjacent to the first strip conductor 13 on the thin film 14 made of an insulator. It is.
[0008]
According to such a directional coupler referred to as a broadside type, the first strip conductor 13 and the second strip conductor 15 are arranged so as to overlap each other via a thin film 14 made of an insulator. Thus, the distance between the two strip conductors 13 and 15 can be reduced, and this provides an advantage that a large coupling amount can be obtained.
[0009]
Further, by setting the line lengths of the first strip conductor 13 and the second strip conductor 15 in the coupling portion to be different from each other, a directional coupler having a predetermined phase difference can be configured. is there.
[0010]
However, in the directional coupler as shown in FIG. 6, the two strip conductors 13 and 15 are at different positions with respect to the ground conductor 12 and are in different ground states. As a result, there is a problem that it is difficult to obtain good isolation characteristics.
[0011]
Furthermore, since the coupling amount is changed depending on the amount of overlap between the two strip conductors 13 and 15, the amount of overlap between the two strip conductors 13 and 15 is slightly deviated from the desired coupling amount during manufacture. Thus, there is a problem that it is difficult to stably produce a directional coupler having desired characteristics.
[0012]
The present invention has been devised in view of the above problems of the prior art, and its purpose is to provide a directional coupler using a line conductor that has good isolation characteristics and is suitable for a line conductor during manufacture. An object of the present invention is to provide a directional coupler with little characteristic change due to displacement.
[0013]
[Means for Solving the Problems]
The directional coupler according to the present invention includes an external line conductor formed on an upper surface of a dielectric substrate, and a ground conductor formed on a lower surface, and the dielectric substrate located between the external line conductor and the ground conductor. An internal line conductor that is electromagnetically coupled to the external line conductor and has a narrower line width than the external line conductor is disposed.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, since the internal line conductor and the external line conductor are arranged so as to be electromagnetically coupled via the dielectric layer of the dielectric substrate, the distance between the two line conductors can be reduced to increase the coupling amount. While the amount of coupling is determined by the amount of overlap between the two line conductors, the inner line conductor is narrower than the external line conductor, that is, between the ground conductor and the external line conductor. Since the line width of the external line conductor is made wider than the line width of the positioned internal line conductor, the internal line conductor is It is possible to position the external line conductor and the ground conductor with a predetermined overlap amount, and it is possible to suppress the characteristic change due to the positional deviation.
[0015]
Hereinafter, a directional coupler according to the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a perspective view showing an example of an embodiment of a directional coupler according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA. In these figures, 21 is a dielectric substrate, 22 is a ground conductor formed on the back surface of the dielectric substrate 21, 23 is an internal line conductor formed on the dielectric substrate, and 24 is a dielectric on the internal line conductor 23. An external line conductor formed to be electromagnetically coupled through a layer. W1 indicates the line width of the internal line conductor 23, W2 indicates the line width of the external line conductor 24, h1 indicates the distance from the ground conductor 22 to the internal line conductor 23, and h2 indicates the distance from the ground conductor 22 to the external line. The distance to the conductor 24 is shown. In the present invention, the line width of the line conductor in the coupling portion is characterized by the line width W2 of the external line conductor 24 being wider than the line width W1 of the internal line conductor 23, that is, W1 <W2.
[0017]
In this example, the dielectric substrate on which the internal line conductor 23 is formed and the dielectric layer between the internal line conductor 23 and the external line conductor 24 are integrated into the dielectric substrate 21, that is, the internal line conductor 23 is dielectric. An example in which an inner layer line conductor is formed inside the body substrate 21 is shown. Not limited to this, the internal line conductor 23 is formed on a dielectric substrate, a dielectric layer is formed thereon so as to cover at least the coupling portion, and an external line conductor 24 is further stacked thereon. May be.
[0018]
Generally, a high frequency component needs to be designed to have a characteristic impedance that matches a predetermined input impedance and output impedance (for example, 50Ω). When this characteristic impedance is Z0, the inductance component of the signal line is L, and the capacitance component between the signal line and the ground conductor is C, there is a relationship of Z0 = √L / √C.
[0019]
The characteristic impedance in the directional coupler of the present invention is called effective impedance Zeff. When the inductance components of the internal and external line conductors 23 and 24 are L1 and L2, respectively, and the capacitance components between the internal and external line conductors 23 and 24 and the ground conductor 22 are C1 and C2, respectively, each line conductor 23 The effective impedance Zeff1 and Zeff2 of 24 are simply empirical formulas as follows:
Zeff1 ≒ √L1 / √C1, Zeff2 ≒ √L2 / √C2
It is expressed as
[0020]
Here, as shown in FIG. 2, the line width of the internal line conductor 23 and the distance from the ground conductor 22 are respectively W1 · h1, and the line width of the external line conductor 24 and the distance from the ground conductor 22 are respectively W2 · h2. When W1 ≧ W2, the distances from the ground conductors 22 of the line conductors 23 and 24 are h1 <h2, so L1 <L2 and C1> C2. As a result, Zeff1 <Zeff2, and Zeff1 and Zeff2 are always different from each other, so that the isolation characteristic of the directional coupler is deteriorated.
[0021]
On the other hand, according to the directional coupler of the present invention, since W1 <W2, L1> L2, but since the relationship between C1 and C2 can be largely adjusted by the line width, Zeff1 and Zeff2 Is smaller than the case of W1 ≧ W2, or Zeff1 and Zeff2 are substantially equal. As a result, reflection of a high-frequency signal due to impedance mismatch in the input / output unit is suppressed, so that a directional coupler having excellent isolation characteristics can be obtained.
[0022]
Further, since the coupling amount of the two line conductors in the broadside type directional coupler is determined by the overlapping amount of the internal and external line conductors 23 and 24, when W1 <W2, the pattern within the range of the difference W2-W1 Since the amount of overlap does not change due to the deviation, the change in the coupling amount due to the pattern deviation is reduced as compared with the case of W1 = W2 or W1> W2, and the characteristic change due to the position deviation can be suppressed to be small.
[0023]
As such line widths W1 and W2, it is preferable to set W1 ≦ 0.2 mm from the viewpoint of miniaturization of the directional coupler, and further, from the viewpoint of suppressing a change in characteristics due to misalignment of the line conductor, It is preferable to set W2 ≧ W1 + 0.1 mm (deviation amount).
[0024]
The relationship between the line widths W1 and W2 and the distances of the line conductors 23 and 24 from the ground conductor 22 is preferably set to h2−h1 ≦ 0.2 mm from the viewpoint of miniaturization and high coupling.
[0025]
The line length at the joint between the internal line conductor 23 and the external line conductor 24, the thickness of each conductor, and the material forming each conductor is preferably 10 mm or less from the viewpoint of miniaturization (however, However, the conductor thickness may be about 20 μm as a general thickness, and the conductor material is usually used for such high-frequency electronic components such as a low resistance conductor such as copper. Anything is acceptable.
[0026]
【Example】
As the directional coupler according to the present invention, W1 = 0.13 mm · W2 = 0.28 mm · h1 = using glass ceramics having a relative dielectric constant ε _r = 5.6 for the dielectric substrate 21 in the configuration shown in FIGS. 0.2 mm · h2 = 0.3 mm, thereby obtaining a sample A of the directional coupler of the present invention.
[0027]
Similarly, W1 = W2 = 0.13 mm · h1 = 0.2 mm · h2 = 0.3 mm using a glass-ceramic dielectric substrate having a relative dielectric constant ε _r = 5.6, thereby making a conventional directional coupling as a comparative example. A sample B of the vessel was obtained.
[0028]
With respect to these samples A and B, isolation characteristics were obtained using a high-frequency 2.5-dimensional electromagnetic field simulator “Momentum (manufactured by Hewlett-Packard)”. The results are shown graphically in FIG. In FIG. 3, the horizontal axis represents the frequency of 500 MHz to 1.5 GHz, the vertical axis represents the isolation (unit: dB), and the solid line and the broken line represent the frequency characteristics of the isolation of the sample A and the sample B, respectively.
[0029]
The result of FIG. 3 shows that the value of Sample A is lower than that of Sample B, and that Sample A has better isolation (insulation) characteristics. Thereby, according to the directional coupler of this invention, since the line width W2 of the external line conductor was made wider than the line width W1 of the internal line conductor, it was confirmed that good isolation characteristics were obtained.
[0030]
Next, in order to investigate the characteristic change with respect to the positional deviation of the line conductor, W1 = 0.13 mm / W2 = 0.28 mm / h1 = 0.2 mm / h2 = 0.3 mm / internal using the same dielectric substrate 21 for the sample A The deviation amount between the line conductor 23 and the external line conductor 24 was set to 0.1 mm, thereby obtaining a sample A ′ of the directional coupler of the present invention.
[0031]
Similarly, using the same dielectric substrate for the sample B of the conventional directional coupler, W1 = W2 = 0.13 mm, h1 = 0.2 mm, h2 = 0.3 mm, and the deviation amount of the line conductor is 0.1 mm. As a result, a sample B ′ of a conventional directional coupler as a comparative example was obtained.
[0032]
And about these sample A * A '* B * B', each high-frequency 2.5-dimensional electromagnetic field simulator "Momentum" (made by Hewlett-Packard) evaluated each coupling characteristic. The results are shown graphically in FIG. In FIG. 4, the horizontal axis represents the frequency of 500 MHz to 1.5 GHz, the vertical axis represents the amount of coupling (unit: dB), and the solid line and the broken line represent the frequency characteristics of sample A · A ′ and sample B · B ′, respectively. Is shown.
[0033]
From the results shown in FIG. 4, when the difference between the samples BB ′ and the sample AA ′ is viewed, the difference between the samples AA ′ is smaller, that is, the sample of the directional coupler of the present invention. It can be seen that the characteristic change with respect to the pattern position deviation of the line conductor is smaller. Similarly, with regard to the isolation characteristic, according to the directional coupler of the present invention, the characteristic change with respect to the positional deviation of the line conductor is smaller than that of the conventional directional coupler.
[0034]
Thus, according to the directional coupler of the present invention, since the line width W2 of the external line conductor is made wider than the line width W1 of the internal line conductor, the characteristic change with respect to the positional deviation of the line conductor can be suppressed small. It can be seen that a directional coupler having desired characteristics can be stably produced.
[0035]
It should be noted that the present invention is not limited to the examples of the embodiments described above, and various modifications and improvements can be added without departing from the scope of the present invention.
[0036]
【The invention's effect】
As described above, according to the directional coupler of the present invention, the external line conductor is formed on the upper surface of the dielectric substrate, the ground conductor is formed on the lower surface, and the dielectric located between the external line conductor and the ground conductor. In a directional coupler formed so that an internal line conductor electromagnetically coupled to an external line conductor is disposed inside the substrate, the internal line conductor and the external line conductor are electromagnetically coupled via the dielectric layer of the dielectric substrate. Since the distance between the two line conductors can be reduced to obtain a large amount of coupling because it is arranged so as to be coupled, the line width of the internal line conductor is made narrower than the line width of the external line conductor, Even if there is a misalignment between the two line conductors, the inner line conductor can ensure a certain amount of overlap between the outer line conductor and the ground conductor, has good isolation characteristics, and changes in characteristics due to misalignment. The ones that can win.
[0037]
As described above, according to the present invention, a broad-side type directional coupler using a line conductor has a good isolation characteristic and a directional coupler with little characteristic change due to a position deviation of the line conductor during manufacture. Could be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of an embodiment of a directional coupler according to the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a diagram showing isolation characteristics of a directional coupler.
FIG. 4 is a diagram showing coupling characteristics of a directional coupler.
FIG. 5 is a perspective view showing an example of a conventional directional coupler.
FIG. 6 is a perspective view showing another example of a conventional directional coupler.
[Explanation of symbols]
21 ... Dielectric substrate
22 ・ ・ ・ ・ ・ Grounding conductor
23 ・ ・ ・ ・ ・ Internal line conductor
24 ... External line conductor W1 ... Line width W2 of internal line conductor ... Line width of external line conductor

Claims (1)

An external line conductor is formed on the upper surface of the dielectric substrate, and a ground conductor is formed on the lower surface, and the external line conductor is electromagnetically coupled to the inside of the dielectric substrate located between the external line conductor and the ground conductor. A directional coupler comprising an internal line conductor having a line width narrower than that of the external line conductor .

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