JP2011072025A - Transmission line structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission line structure which suppresses the degradation of performance due to leakage and reflection of an electromagnetic wave from a division surface of a conductor and achieves cost reduction. <P>SOLUTION: The transmission line structure is configured such that waveguide lines 2a to 2c for transmitting electromagnetic waves are formed by a first conductor plate 1a and a second conductor plate 1b divided by a division surface common to the waveguide lines 2a to 2c. The respective waveguide lines 2a to 2c are arranged such that a wall thickness D of a conductor plate between adjacent transmission lines in the common division surface becomes an odd-number multiple of almost 1/4 of propagation wavelength of free space in an operating frequency. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmission line used in a high frequency band including a microwave band and a millimeter wave band, and more particularly to a transmission line structure that constitutes a waveguide line and a waveguide circuit.

  In general, when dividing a waveguide, when dividing the waveguide by a dividing plane parallel to the short side of the waveguide cross section parallel to the propagation direction of the electromagnetic wave and perpendicular to the propagation direction of the electromagnetic wave, It is possible to select a split surface that does not divide the current flowing through the inner side wall (in this case, the wide wall surface).

  In addition, when the cross section of the waveguide perpendicular to the propagation direction of the electromagnetic wave has a symmetric shape, it is generated by dividing the waveguide by dividing the waveguide at a dividing plane passing through the substantially midpoint of the long side of the waveguide cross section. The propagation mode of the electromagnetic wave propagating through the waveguide line is not disturbed due to the gap. Therefore, in this case, performance deterioration due to the gap can be minimized.

  Such a split surface (hereinafter referred to as an “ideal split surface”) that can suppress performance degradation due to the gap to a minimum is the shape of the waveguide cross section and the material constant of the material forming the waveguide ( In some cases, the ideal dividing plane deviates from the approximate midpoint of the long side of the waveguide cross section.

  However, for example, when a conversion circuit to another waveguide is provided on the waveguide line as an additional structure that becomes a factor disturbing the distribution (current distribution) of the current flowing through the side wall in the waveguide line. As described above, the performance degradation cannot be sufficiently suppressed only by selecting the ideal dividing plane. That is, in the waveguide line, it is not possible to realize good reflection characteristics and pass characteristics, or good isolation characteristics from other channels.

Then, as what solves said problem, the following are mentioned, for example.
The conventional waveguide plate has a plurality of waveguide lines, and on both sides of the long side of each waveguide cross section orthogonal to the propagation direction of the electromagnetic wave, from the end of the waveguide line at the operating frequency. A choke structure having a depth of about 1/4 (λ / 4) of the propagation wavelength in the free space is formed at a position separated by about 1/4 (λ / 4) of the propagation wavelength in free space. (For example, refer to Patent Document 1).

Hereinafter, a conventional transmission line structure will be described with reference to the drawings.
FIG. 4 is a cross-sectional view showing a conventional transmission line plate (transmission line structure). The transmission line plate of FIG. 4 is a transmission line plate that is divided by a dividing plane parallel to the short side of the waveguide cross section that is parallel to the propagation direction of the electromagnetic wave and orthogonal to the propagation direction of the electromagnetic wave. The waveguide plate shown is applied. A conversion circuit to another waveguide is provided on the waveguide line as an additional structure that disturbs the current distribution in the waveguide line.

In FIG. 4, in this transmission line plate, the first conductor plate 21a and the second conductor plate 21b are parallel to the propagation direction of the electromagnetic wave and parallel to the short side of the cross section of the waveguide perpendicular to the propagation direction of the electromagnetic wave. It is configured to be in contact with the dividing surface.
Further, the first conductor plate 21a and the second conductor plate 21b are in contact with each other to form all three-channel waveguide lines 22a to 22c. Further, a gap 26 is formed on the dividing surface.
The first conductor plate 21a is provided with choke structures 23a to 23d provided so as to sandwich each of the waveguide lines 22a to 22c.

In addition, in the waveguide lines 22a to 22c, separate waveguides 24a to 24c for each channel are coupled slots that are conversion circuits that realize the connection between the waveguide lines 22a to 22c and the waveguides 24a to 24c. (Additional structure) It is connected via 25a-25c. The coupling slots 25a to 25c are coupling holes.
In FIG. 4, coupling slots 25a to 25c are provided as additional structures that disturb the current distribution in the waveguide lines 22a to 22c. However, the present invention is not limited to this, and power is distributed to a plurality of transmission lines. It may be a branch circuit or a matching element that improves the reflection characteristics of the waveguide line.

Here, the choke structures 23a to 23d are on both sides of the long side of each waveguide cross section orthogonal to the propagation direction of the electromagnetic wave, and the propagation wavelength in free space at the use frequency from the end of the waveguide 22a to 22c. Are formed at a depth of about 1/4 (λ / 4) of the propagation wavelength in free space at the used frequency.
Thereby, the performance deterioration by the leakage and reflection of the electromagnetic wave from the division surface of a conductor plate is suppressed.

JP 2003-188601 A

However, the prior art has the following problems.
In the conventional transmission line plate shown in FIG. 4, when the choke structures 23a to 23d are formed, the propagation in free space at least at the used frequency is used as the wall thickness of the conductor plate between the adjacent waveguide lines 22a to 22c. It is necessary to secure at least half of the wavelength.
For this reason, a processing cost for forming the choke structure is required, which increases the manufacturing cost.

  The present invention has been made to solve the above-described problems, and the object thereof is to suppress the deterioration of performance due to leakage and reflection of electromagnetic waves from the divided surface of the conductor and to realize cost reduction. It is in providing the transmission line structure which can do.

  A transmission line structure according to the present invention is a transmission line structure in which a plurality of transmission lines for transmitting electromagnetic waves are formed by a plurality of conductors that are divided by a common dividing plane into a plurality of transmission lines, Each of the plurality of transmission lines is arranged such that the wall thickness of the conductor between adjacent transmission lines on the common dividing plane is an odd multiple of about 1/4 of the free space propagation wavelength at the operating frequency. is there.

According to the transmission line structure of the present invention, each of the plurality of transmission lines has an odd wall thickness of a conductor between adjacent transmission lines on a common dividing plane that is approximately 1/4 of the free space propagation wavelength at the operating frequency. It is arranged to be doubled. Here, the conductor between the transmission lines having a thickness that is an odd multiple of about 1/4 of the free space propagation wavelength functions as an impedance transformer of 1/4 wavelength, and a choke structure is provided between adjacent transmission lines. Without leakage and reflection of electromagnetic waves.
Therefore, it is possible to suppress performance deterioration due to leakage or reflection of electromagnetic waves from the divided surface of the conductor, and to realize cost reduction.

It is sectional drawing which shows the transmission line plate which concerns on Embodiment 1 of this invention. (A) is sectional drawing which shows the transmission line plate which concerns on Embodiment 2 of this invention, (b) is arrow sectional drawing along the II line | wire of the transmission line plate shown to (a). It is. It is another sectional view showing a transmission line plate concerning Embodiment 2 of this invention. It is sectional drawing which shows the conventional transmission line plate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts will be described with the same reference numerals.

Embodiment 1 FIG.
1 is a cross-sectional view showing a transmission line plate (transmission line structure) according to Embodiment 1 of the present invention.
The transmission line plate of FIG. 1 is divided into transmission lines that are parallel to the tube axis direction (electromagnetic wave propagation direction) of the waveguide and that are parallel to the short side of the waveguide cross section perpendicular to the tube axis direction. In the plate, a conversion circuit to another waveguide is provided on the waveguide line as an additional structure that disturbs the current distribution flowing through the side wall in the waveguide line.

  In FIG. 1, this transmission line plate includes a common first conductor plate 1a and second conductor plate 1b that are parallel to the tube axis direction and parallel to the short side of the waveguide cross section perpendicular to the tube axis direction. It is configured to be in contact with the dividing surface. The common dividing plane passes through a substantially midpoint of the long side of the waveguide cross section perpendicular to the tube axis direction. Here, the approximate midpoint of the long side of the waveguide cross section may be a midpoint of mechanical dimensions or a midpoint of electrical dimensions.

Further, the first conductor plate 1a and the second conductor plate 1b are in contact with each other to form all three-channel waveguide lines 2a to 2c (transmission lines). Further, a gap 7 is formed on the dividing surface.
The first conductor plate 1a is formed with choke structures 3a and 3b provided so as to sandwich the waveguide lines 2a to 2c. The choke structures 3a and 3b are separated from the outside of the waveguide lines 2a and 2c at both ends of the waveguide lines 2a to 2c by approximately 1/4 of the propagation wavelength in the free space at the use frequency. It is formed so as to have a depth of about ¼ of the propagation wavelength in free space.

Further, a transmission line 4a is formed between the waveguide line 2a and the waveguide line 2b by a gap 7 when the first conductor plate 1a and the second conductor plate 1b are divided. A transmission line 4b is formed by a gap 7 between the waveguide line 2b and the waveguide line 2c.
In addition, in the waveguide lines 2a to 2c, separate waveguides 5a to 5c for each channel are coupling slots that are conversion circuits that realize connection between the waveguide lines 2a to 2c and the waveguides 5a to 5c. (Additional structure) It is connected via 6a-6c. The coupling slots 6a to 6c are coupling holes.

In the transmission line plate shown in FIG. 1, the first conductor plate 1a and the second conductor plate 1b are brought into contact with each other in the vicinity of the ideal dividing plane, similarly to the conventional transmission line plate described above. Therefore, if it is a normal transmission line, the leakage of the electromagnetic wave from the division surface of a conductor plate can be prevented.
This is because, in the current vector flowing through the side wall (wide wall surface) in the normal waveguide line, the current vector orthogonal to the tube axis direction is not distributed on the ideal dividing plane determined only by the waveguide conditions. This is because the current flow is not divided by the division.

If the waveguide cross-sectional shape and the material constant of the material forming the waveguide (conductivity, dielectric constant, surface roughness, etc.) are symmetrical with the dividing plane as the symmetry plane, ideal division The surface is a divided surface that passes through a substantially midpoint of the long side of the waveguide cross section.
However, if the material constant and processing method (processing R, draft angle, etc.) of the material forming the waveguide are not symmetrical with the dividing surface as the symmetric surface, the ideal dividing surface is the length of the waveguide cross section. The position may deviate from the midpoint of the side, and its position depends on the material constant and processing method.

  Here, in the transmission line plate of FIG. 1, coupling slots 6 a to 6 c are provided on the upper portions of the waveguide lines 2 a to 2 c as additional structures that disturb the current distribution flowing through the side walls in the waveguide lines 2 a to 2 c. It has been. Therefore, a current vector orthogonal to the tube axis direction is distributed even in the vicinity of the ideal dividing plane determined from the cross-sectional shape of the waveguide.

  Therefore, as shown in FIG. 1, when the coupling slots 6a to 6c that cause disturbance of the current distribution are provided on the waveguide lines 2a to 2c, the cross-sectional shape and material of the waveguide as described above. The performance deterioration cannot be sufficiently suppressed only by selecting the ideal dividing plane determined only from the above. In other words, without providing a choke structure on both sides of the waveguide line, it is impossible to achieve good reflection characteristics and pass characteristics or good isolation characteristics with other channels in each waveguide line. .

Therefore, in the transmission line plate of the first embodiment, the waveguide lines 2a to 2c have the wall thicknesses of the transmission lines 4a and 4b between the adjacent waveguide lines 2a to 2c on the common dividing plane (waveguide). The conductor plate thickness (D) between the lines 2a to 2c is arranged to be approximately 1/4 (λ / 4) of the free space propagation wavelength at the operating frequency.
Here, by forming the wall thickness D of the transmission lines 4a and 4b to be approximately ¼ of the free space propagation wavelength, a gap 7 is formed when the first conductor plate 1a and the second conductor plate 1b are brought into contact with each other. The transmission lines 4a and 4b to be operated function as a quarter wavelength impedance transformer. Further, since the end portions on the adjacent channel side of the transmission lines 4a and 4b become open points by the adjacent waveguide lines 2a to 2c, an equivalent short-circuit point is obtained at the end portion on the own channel side. Can do. Therefore, leakage and reflection of electromagnetic waves can be prevented without providing a choke structure between adjacent waveguide lines 2a to 2c.

According to the transmission line structure according to Embodiment 1 of the present invention, the plurality of transmission lines have a wall thickness between adjacent transmission lines on a common dividing plane of approximately ¼ of the free space propagation wavelength at the used frequency. It is arranged to be.
Here, the wall between the transmission lines having a thickness of about ¼ of the free space propagation wavelength functions as a quarter wavelength impedance transformer, and electromagnetic waves can be generated without providing a choke structure between adjacent transmission lines. Prevent leaks and reflections.
Therefore, it is possible to suppress performance deterioration due to leakage or reflection of electromagnetic waves from the divided surface of the conductor, and to eliminate the choke structure and reduce the manufacturing cost of the transmission line structure. Moreover, since the space | interval between waveguide lines can be narrowed, the size of a transmission line structure can be reduced.
Further, in each waveguide line, it is possible to realize good reflection characteristics and pass characteristics, or good isolation characteristics from other channels.

  Here, when there are adjacent waveguide lines on both sides of the waveguide lines 2a to 2c, the transmission lines 4a and 4b can be arranged as described above to obtain good characteristics. When there is no adjacent waveguide line on both sides of the wave guide line, the choke structure 3a, 3b or dummy waveguide is provided on the side where the adjacent waveguide line does not exist, as in the conventional transmission line plate. It is necessary to provide a pipe line.

In the first embodiment, the coupling slots 6a to 6c are provided as additional structures that disturb the current distribution flowing through the side walls in the waveguide lines 2a to 2c. However, the present invention is not limited to this.
Additional structures include coupling holes that connect waveguide lines and free space, branch circuits that distribute power to multiple transmission lines, bend circuits that change the propagation direction of electromagnetic waves, and reflection characteristics of waveguide lines. Examples include an improved matching element, a radiation slot that functions as an antenna, a branch circuit such as an H-plane T-branch and an E-plane T-branch, a bend circuit such as an H-plane bend and an E-plane bend, and an iris or a post for matching applications.
In these cases, the same effect as in the first embodiment can be obtained.

  Moreover, although the said Embodiment 1 demonstrated the case where the additional structure which disturbs the current distribution which flows through the side wall in the waveguide lines 2a-2c existed, it is not limited to this. Even when the additional structure does not exist, when the current flowing through the side wall in the waveguide line is divided, the transmission lines 4a and 4b according to the first embodiment are applied, so that The same effect as in the first embodiment can be obtained.

  In the case where the current flowing through the side wall in the waveguide line is divided, the first conductor plate and the second conductor plate are first divided by the division surface parallel to the short side of the waveguide cross section perpendicular to the tube axis direction. In the case of dividing the line, there may be a case where the divided surface is out of the ideal divided surface. Further, as another case where the current flowing through the side wall in the waveguide line is divided, the first conductor plate and the second conductor are formed on the divided surface parallel to the long side of the cross section of the waveguide orthogonal to the tube axis direction. A case where the plate is divided is mentioned. In these cases, the first conductor plate and the second conductor plate are divided at the end of the waveguide cross section.

Embodiment 2. FIG.
FIG. 2A is a cross-sectional view showing a transmission line plate (transmission line structure) according to Embodiment 2 of the present invention. FIG. 2B is a cross-sectional view taken along line II of the transmission line plate (transmission line structure) shown in FIG.
The transmission line plate in FIGS. 2A and 2B is divided by a dividing plane orthogonal to the tube axis direction of the waveguide (the propagation direction of the electromagnetic wave).

2 (a) and 2 (b), this transmission line plate is configured such that the first conductor plate 11a and the second conductor plate 11b are in contact with each other at a common dividing plane orthogonal to the tube axis direction. Yes.
Further, the first conductor plate 11a and the second conductor plate 11b are in contact with each other to form all three channel waveguide lines 12a to 12c (transmission lines). Further, a gap 17 is formed on the dividing surface.

  The first conductor plate 11a is formed with choke structures 13a and 13b provided so as to sandwich the waveguide lines 12a to 12c. The choke structures 13a and 13b are free at the use frequency at positions separated from the outside of the waveguide lines 12a and 12c at both ends of the waveguide lines 12a to 12c by approximately 1/4 of the propagation wavelength in the free space at the use frequency. It is formed so as to have a depth of about 1/4 of the propagation wavelength in space.

  Also, a transmission line 14a is formed between the waveguide line 12a and the waveguide line 12b by a gap 17 when the first conductor plate 11a and the second conductor plate 11b are divided. A transmission line 14b is formed by a gap 17 between the waveguide line 12b and the waveguide line 12c.

As shown in FIG. 2, the transmission line plate configured to be in contact with the dividing plane orthogonal to the tube axis direction is different from the above-described conventional transmission line plate and the transmission line plate of the first embodiment, and the conductor plate. There is no ideal split surface that hardly leaks electromagnetic waves from the split surface.
This is because the current vector flowing through the side wall in the waveguide line is necessarily divided at the dividing plane orthogonal to the tube axis direction.

In such a case, as shown in Patent Document 1, the free space at the use frequency is located at a position that is approximately 1/4 of the propagation wavelength in the free space at the use frequency from the end of the waveguide line. By installing a choke structure having a depth of about ¼ of the propagation wavelength inside, deterioration in performance can be suppressed. That is, by providing the choke structure around the waveguide line, it is possible to realize good reflection characteristics and pass characteristics or good isolation characteristics from other channels in each waveguide line.
However, as described above, forming the choke structure increases the size of the transmission line plate and increases the manufacturing cost.

Therefore, in the transmission line plate according to the second embodiment, the waveguide lines 12a to 12c have the wall thicknesses of the transmission lines 14a and 14b between the adjacent waveguide lines 12a to 12c on the common dividing plane (waveguide). The conductor plate thickness (D) between the lines 12a to 12c is arranged to be approximately ¼ (λ / 4) of the free space propagation wavelength at the operating frequency.
Here, by forming the wall thickness D of the transmission lines 14a and 14b to be approximately ¼ of the free space propagation wavelength, the transmission lines 14a and 14b are formed by the gap 17 when the first conductor plate 11a and the second conductor plate 11b are brought into contact with each other. The transmission lines 14a and 14b to be used function as a quarter wavelength impedance transformer. Further, since the end portions on the adjacent channel side of the transmission lines 14a and 14b become open points by the adjacent waveguide lines 12a to 12c, an equivalent short-circuit point is obtained at the end portion on the own channel side. Can do. Therefore, leakage and reflection of electromagnetic waves can be prevented without providing a choke structure between adjacent waveguide lines 12a to 12c.

According to the transmission line structure according to Embodiment 2 of the present invention, the plurality of transmission lines have a wall thickness between adjacent transmission lines on a common dividing plane of approximately ¼ of the free space propagation wavelength at the used frequency. It is arranged to be.
Here, the wall between the transmission lines having a thickness of about ¼ of the free space propagation wavelength functions as a quarter wavelength impedance transformer, and electromagnetic waves can be generated without providing a choke structure between adjacent transmission lines. Prevent leaks and reflections.
Therefore, it is possible to suppress performance deterioration due to leakage or reflection of electromagnetic waves from the divided surface of the conductor, and to eliminate the choke structure and reduce the manufacturing cost of the transmission line structure. Moreover, since the space | interval between waveguide lines can be narrowed, the size of a transmission line structure can be reduced.
Further, in each waveguide line, it is possible to realize good reflection characteristics and pass characteristics, or good isolation characteristics from other channels.

  Here, when there are adjacent waveguide lines on both sides of the waveguide lines 12a to 12c, the transmission lines 14a and 14b can be arranged as described above to obtain good characteristics. When there are no adjacent waveguide lines on both sides of the wave guide line, the choke structures 13a and 13b or dummy waveguides are provided on the side where there is no adjacent waveguide line, as in the case of the conventional transmission line plate. It is necessary to provide a pipe line.

  In addition, as shown in FIG. 3, the waveguide lines orthogonal to the tube axis direction are set so that the tube axes of the adjacent waveguide lines 12a to 12c are offset from each other, that is, for each of the waveguide lines 12a to 12c. The positions of the waveguide lines 12a to 12c are in the division plane so that straight lines passing through the midpoints of the sides of the cross sections 12a to 12c and the axes of the waveguide lines 12a to 12c are offset from each other in the common division plane. By displacing them, the isolation characteristics between the waveguide lines 12a to 12c can be further improved.

In the first and second embodiments, the waveguide lines 2a to 2c and 12a to 12c are described as the transmission lines, but the present invention is not limited to this. A coaxial line etc. are mentioned as a transmission line.
In these cases, the same effects as those of the first and second embodiments can be obtained.

In the first and second embodiments, the waveguide lines 2a to 2c and 12a to 12c are disposed adjacent to each other in the short side direction in the waveguide cross section orthogonal to the tube axis direction. However, the present invention is not limited to this. The waveguide line may be arranged adjacent to the long side direction in the waveguide cross section. The same applies to transmission lines other than the waveguide line described above.
In these cases, the same effects as those of the first and second embodiments can be obtained.

In the first and second embodiments, the wall thickness D of the transmission lines 4a, 4b, 14a, and 14b formed between the adjacent waveguide lines 2a to 2c and 12a to 12c is the free space propagation at the use frequency. Although it has been described that the wavelength is approximately ¼ (λ / 4), the present invention is not limited to this.
The wall thickness of the transmission line formed between adjacent waveguide lines may be an odd multiple of approximately ¼ of the free space propagation wavelength at the operating frequency.
Also in this case, the transmission line formed between the adjacent waveguide lines functions as a quarter wavelength impedance transformer, so that leakage or reflection of electromagnetic waves can be prevented without providing a choke structure between the adjacent transmission lines. Can be prevented.
At this time, the propagation in the free space at the use frequency is located between the adjacent waveguide lines and at a position approximately 1/4 of the propagation wavelength in the free space at the use frequency from the end of the waveguide line. By forming a choke structure having a depth of approximately ¼ of the wavelength, it is possible to further suppress performance deterioration due to leakage or reflection of electromagnetic waves from the divided surface of the conductor.

In the first and second embodiments, the transmission line plate is described as being configured by a plurality of conductor plates. However, the present invention is not limited to this. Instead of using a conductor plate, the transmission line plate may be formed by molding a plastic, resin, or the like, and plating the conductor on the surface that functions as the transmission line.
In these cases, the same effects as those of the first and second embodiments can be obtained.

  1a, 1b, 11a, 11b Conductor plate, 2a-2c, 12a-12c Waveguide line (transmission line), 3a, 3b, 13a, 13b Choke structure, 4a, 4b, 14a, 14b Transmission line, 6a-6c Slot (additional structure).

Claims (2)

A plurality of transmission lines for transmitting electromagnetic waves is a transmission line structure formed by a plurality of conductors divided by a common dividing surface to the plurality of transmission lines,
Each of the plurality of transmission lines is arranged such that the wall thickness of the conductor between adjacent transmission lines on the common dividing plane is an odd multiple of about 1/4 of the free space propagation wavelength at the operating frequency. A transmission line structure characterized by that.   A depth of approximately ¼ of the free space propagation wavelength at the use frequency is set between adjacent transmission lines and at a position approximately ¼ of the free space propagation wavelength at the use frequency from the end of the transmission line. The transmission line structure according to claim 1, wherein a choke structure is formed.

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