JP6005228B1 - converter - Google Patents

Abstract

In a converter for mutually converting a waveguide mode of a waveguide and a waveguide mode of a microstrip line, it is possible to realize a converter that can be reduced in cost more easily than in the past. A single-sided mounting substrate having a dielectric substrate (13a) and a signal line (13) formed on the surface of the dielectric substrate (13a) is used as a microstrip line (13). Further, the conductor plate 12 and the back short block 14 are insulated from each other, and the formation of vias for short-circuiting them on the dielectric substrate 13a is omitted. [Selection] Figure 1

Description

  The present invention relates to a converter that mutually converts a waveguide mode of a waveguide and a waveguide mode of a microstrip line.

  With the demand for higher speed and larger capacity of wireless communication, the frequency band used for wireless communication has been increased. For this reason, the frequency of signals to be processed by wireless devices is also increasing. Specifically, it is necessary to process a high-frequency signal having a frequency (30 GHz or more and 300 GHz or less) corresponding to a millimeter wave.

  An example of a transmission medium that can efficiently transmit such a high-frequency signal is a waveguide. However, the waveguide cannot be directly connected to the integrated circuit mounted on the circuit board. For this reason, a configuration in which a microstrip line is interposed between an integrated circuit and a waveguide is widely used. In the case of adopting such a configuration, a converter that mutually converts the waveguide mode of the waveguide and the waveguide mode of the microstrip line is required.

  Such a converter includes a microstrip line, a waveguide bonded to the back surface of the microstrip line (a surface on which a planar conductor functioning as a ground is formed), and the surface of the microstrip line (as a signal line). A device having a conductor block (hereinafter also referred to as “back short block”) joined to a surface on which a functioning strip-like conductor is formed is widely known.

  Patent Documents 1 and 2 disclose a converter using a short-circuited waveguide formed in a dielectric substrate as a back short. In the converter described in Patent Document 1, the waveguide is directly connected to the back surface of the microstrip line. On the other hand, in the converter described in Patent Document 2, the waveguide is connected to the back surface of the microstrip line via a base in which an opening is formed.

JP 2008-193162 A (released on August 21, 2008) JP 2008-193243 A (released on August 21, 2008)

  However, the conventional converter employs a configuration in which a double-sided mounting substrate having a signal line formed on the front surface and a ground formed on the back surface is used as a microstrip line. A double-sided mounting board is higher in manufacturing cost than a single-sided mounting board. For this reason, the conventional converter has a problem that it is difficult to reduce the cost.

  In the conventional converter, vias are formed in the dielectric substrate constituting the microstrip line, and the back short circuit is short-circuited to the waveguide (Patent Document 1) or the base (Patent Document 2) using the vias. The configuration to be adopted was adopted. The formation of vias on the dielectric substrate is expensive because it requires processes such as sputtering and plating. Therefore, this point is also a factor that hinders cost reduction of the converter.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a converter that mutually converts a waveguide mode of a waveguide and a waveguide mode of a microstrip line at a lower cost than conventional ones. This is to realize a converter that can be easily realized.

  In order to solve the above problems, a converter according to the present invention includes a conductor plate in which an opening is formed, a waveguide joined to the back surface of the conductor plate so that the inside of the tube communicates with the opening, and a dielectric. A microstrip line having a body substrate and a signal line formed on a surface of the dielectric substrate, wherein a back surface of the dielectric substrate is a surface of the conductor plate so that a tip of the signal line overlaps the opening. A conductor block having a microstrip line bonded to the bottom surface and a recess opened to the bottom surface and the side surface, wherein the bottom surface is the dielectric substrate so that the signal line enters the recess from the side surface. And a conductor block bonded to the surface of the conductor plate, wherein the conductor plate and the conductor block are insulated from each other.

  According to the above configuration, since the conductor plate is joined to the back surface of the dielectric substrate, the signal line is formed on the surface of the dielectric substrate without forming a ground layer on the back surface of the dielectric substrate. The mounting substrate can function as a microstrip line. According to the above configuration, since the conductor block is insulated from the conductor plate, there is no need to form a via in the dielectric substrate for short-circuiting the conductor block to the conductor plate.

  That is, according to the above configuration, it is not necessary to form a ground layer on the back surface of the dielectric substrate, and it is not necessary to form a via in the dielectric substrate. Therefore, the manufacturing cost of the converter can be easily reduced.

  Note that the thickness of the conductor plate is set such that the distance between the waveguide and the signal line is a distance that minimizes the insertion loss (for example, 1/4 of the free space wavelength λ corresponding to the center frequency of the operating wavelength of the converter). It functions as a spacer to be adjusted, and corresponds to a base in the converter described in Patent Document 2.

  In the converter according to the present invention, it is preferable that the dielectric substrate has a thickness of 50 μm or less.

  According to said structure, sufficient capacitive coupling can be made between a conductor block and a conductor board. Thereby, even if it does not short-circuit a conductor block to a conductor board, if the shape of a conductor block is designed suitably, a conductor block can be functioned as a back short circuit.

  In the converter according to the present invention, the conductor block has a rectangular parallelepiped shape, the recess has a T-shape in plan view, and the space in the recess has a front wall opened at the center, the front It is preferable that the four sides are surrounded by a pair of side walls orthogonal to the wall and a rear wall facing the front wall.

  According to the above configuration, the electromagnetic wave propagated through the waveguide region of the waveguide is efficiently incident on the microstrip line, and the electromagnetic wave propagated through the waveguide region of the microstrip line is efficiently guided into the waveguide. Can be made incident.

  In the converter according to the present invention, it is preferable that the thickness of the rear wall normalized by a free space wavelength corresponding to the center frequency of the operation band of the converter is 0.08 or more and 0.48 or less.

  According to said structure, the converter with a low insertion loss is realizable over a wide band.

  In the converter according to the present invention, it is preferable that the thickness of the side wall normalized by a free space wavelength corresponding to the center frequency of the operation band of the converter is 0.10 or more and 0.30 or less.

  According to said structure, the converter with a low insertion loss is realizable over a wide band.

  In the converter according to the present invention, it is preferable that the thickness of the front wall normalized by a free space wavelength corresponding to the center frequency of the operation band of the converter is 0.25 or more and 0.76 or less.

  According to said structure, the converter with a low insertion loss is realizable over a wide band.

  ADVANTAGE OF THE INVENTION According to this invention, in the converter which mutually converts the waveguide mode of a waveguide, and the waveguide mode of a microstrip line, the converter whose cost reduction is easier than before is realizable.

It is a disassembled perspective view of the converter which concerns on one Embodiment of this invention. It is sectional drawing of the converter shown in FIG. It is a top view of the metal plate with which the converter concerning a 1st example is provided. It is a top view of the resin substrate with which the converter concerning the 1st example is provided. It is a three-plane figure of the back short block with which the converter concerning a 1st example is provided. It is a graph which shows the frequency characteristic of the insertion loss of the converter which concerns on a 1st Example. It is a top view of the back short block with which the converter concerning the 1st modification is provided. It is a graph which shows the frequency characteristic of the insertion loss of the converter concerning the 1st modification. It is a graph which shows the specific bandwidth of the frequency band whose insertion loss exceeds -3 dB in the converter which concerns on a 1st modification. It is a top view of the back short block with which the converter concerning the 2nd modification is provided. It is a graph which shows the frequency characteristic of the insertion loss of the converter concerning the 2nd modification. It is a graph which shows the specific bandwidth of the frequency band where insertion loss exceeds -3dB in the converter which concerns on a 2nd modification. It is a top view of the back short block with which the converter concerning the 3rd modification and the 4th modification is provided. It is a graph which shows the frequency characteristic of the insertion loss of the converter concerning the 3rd modification. It is a graph which shows the specific bandwidth of the frequency band where insertion loss exceeds -3dB in the converter which concerns on a 3rd modification. It is a graph which shows the frequency characteristic of the insertion loss of the converter which concerns on a 4th modification. It is a graph which shows the specific bandwidth of the frequency band in which the insertion loss exceeds -3 dB in the converter which concerns on a 4th modification.

[Construction of the converter]
The structure of the converter 1 which concerns on one Embodiment of this invention is demonstrated with reference to FIG.1 and FIG.2. FIG. 1 is an exploded perspective view of the converter 1, and FIG. 2 is a cross-sectional view of the converter 1.

  As shown in FIG. 1, the converter 1 includes a waveguide 11, a conductor plate 12, a microstrip line 13, and a back short block 14, and the waveguide mode of the waveguide 11 and the waveguide of the microstrip line. It functions as a converter for converting between modes.

  The waveguide 11 is a tubular member that is open at both ends, and is arranged so that its tube axis is parallel to the z-axis in the illustrated coordinate system. The tube wall 11a of the waveguide 11 is made of a conductor such as metal, and the inside of the waveguide 11 filled with a dielectric functions as a waveguide region 11b that guides electromagnetic waves. In the present embodiment, a hollow rectangular waveguide having a rectangular parallelepiped waveguide region 11 b filled with air is used as the waveguide 11.

  The conductor plate 12 is a plate-like member made of a conductor such as metal, and is arranged so that its main surface is parallel to the xy plane in the illustrated coordinate system. An opening 12 a is formed in the conductor plate 12. The planar view shape of the opening 12a viewed from the positive direction of the z-axis is a rectangle having a long side parallel to the x-axis and a short side parallel to the y-axis. The waveguide 11 described above has the back surface of the conductor plate 12 so that the tube axis thereof is orthogonal to the main surface of the conductor plate 12 and the waveguide region 11b and the opening 12a of the conductor plate 12 communicate with each other. To be joined.

  The microstrip line 13 includes a plate-like dielectric substrate 13a made of a dielectric material such as a resin, and a belt-like signal line 13b made of a conductor such as a metal formed on the front surface of the dielectric substrate 13a. It is comprised by. The dielectric substrate 13a is arranged so that its main surface is parallel to the xy plane in the illustrated coordinate system. The signal line 13b extends in the y-axis positive direction in the illustrated coordinate system, and its tip reaches a position overlapping the opening 12a of the conductor plate 12 when viewed from the z-axis positive direction. The above-described conductor plate 12 is joined to the microstrip line 13 so that its front surface is in contact with the back surface of the dielectric substrate 13a, and serves as a ground layer for the microstrip line 13. A region in the dielectric substrate 13a sandwiched between the signal line 13b and the conductor plate 12 functions as a waveguide region 13c that guides electromagnetic waves.

  The back short block 14 is a conductor block in which a recess 14a opened to the bottom surface and the side surface is formed. In the present embodiment, a metal block having a rectangular parallelepiped shape and having a T-shaped recess 14 in plan view is used as the back short block 14. The space in the recess 14 is divided into four sides: (1) a front wall 14b1 having an open center, (2) a pair of side walls 14b2 orthogonal to the front wall 14b1, and (3) a rear wall 14b3 facing the front wall 14b1. being surrounded. The back short block 14 is microstrip so that the bottom surface thereof is in contact with the front surface of the dielectric substrate 13a and the signal line 13b enters the recess 14a from the opening of the front wall 14b1. It is joined to the line 13.

  Note that the coordinate system shown in FIG. 1 is determined as follows. That is, (1) An axis parallel to the axial direction of the signal line 13b is taken as a y-axis. The direction of the y-axis is determined so that the direction from the root of the signal line 13b toward the tip is a positive direction. (2) The axis parallel to the thickness direction of the signal line 13b is taken as the z-axis. The direction of the z-axis is determined so that the direction from the dielectric substrate 13a toward the signal line 13b is a positive direction. (3) The axis parallel to the width direction of the signal line 13b is taken as the x-axis. The direction of the x axis is determined so that the x axis forms a right-handed system together with the y axis and the z axis described above.

  In the present specification, of the six surfaces constituting the front surface of the plate-like member, the two surfaces having the largest area are referred to as main surfaces, and the remaining four surfaces are referred to as side surfaces. Moreover, when distinguishing two main surfaces of a plate-shaped member mutually, one side is called a front (front) surface and the other is called a back surface. The front surface and the back surface are merely convenient names for distinguishing the two main surfaces from each other, and do not limit the plate-like member.

[Function of the converter]
In the converter 1, the waveguide mode of the waveguide 11 is converted to the waveguide mode of the microstrip line 13 as follows. That is, an electromagnetic wave input to the waveguide 11 from the end on the negative side of the z axis propagates in the waveguide region 11b of the waveguide 11 in the positive direction of the z axis. The electromagnetic wave propagated in the positive z-axis direction through the waveguide region 11 b of the waveguide 11 enters the microstrip line 13 through the opening 12 a of the conductor plate 12. The electromagnetic wave incident on the microstrip line 13 propagates through the waveguide region 13c of the microstrip line 13 in the negative y-axis direction. The electromagnetic wave propagated in the y-axis negative direction through the waveguide region 13c of the microstrip line 13 is output from the end of the microstrip line 13 on the y-axis negative direction side.

  In the converter 1, the waveguide mode of the microstrip line 13 is converted to the waveguide mode of the waveguide 11 as follows. That is, the electromagnetic wave input to the microstrip line 13 from the end on the negative side in the y-axis propagates in the waveguide 13c of the microstrip line 13 in the positive y-axis direction. The electromagnetic wave propagated in the y-axis positive direction through the waveguide region 13 c of the microstrip line 13 enters the waveguide 11 through the opening 12 a of the conductor plate 12. The electromagnetic wave incident on the waveguide 11 propagates through the waveguide region 11b of the waveguide 11 in the negative z-axis direction. The electromagnetic wave that propagates in the waveguide region 11b of the waveguide 11 in the negative z-axis direction is output from the end of the waveguide 11 on the negative z-axis direction.

  Here, in the converter 1, the tip of the signal line 13 b is accommodated in the recess 14 a of the back short block 14. Therefore, the electromagnetic wave propagated through the waveguide region 11b of the waveguide 11 is efficiently incident on the microstrip line 13, and the electromagnetic wave propagated through the waveguide region 13c of the microstrip line 13 is efficiently guided. It becomes possible to enter the tube 11. That is, a loss (hereinafter referred to as loss generated when the waveguide mode of the conductor plate 12 is converted into the waveguide mode of the microstrip line 13 and when the waveguide mode of the microstrip line 13 is converted into the waveguide mode of the conductor plate 12. , Described as “insertion loss”).

[Features of the converter]
Characteristic points in the converter 1 according to the present embodiment are as follows.

  That is, in the converter 1 according to the present embodiment, a single-sided mounting substrate in which a ground layer is not formed on the back surface is used as the microstrip line 13. Thereby, compared with the conventional converter which uses the double-sided mounting board | substrate with which the ground layer was formed in the back surface as a microstrip line, manufacturing cost can be held down.

  Here, the single-sided mounting substrate on which the ground layer is not formed on the back surface can function as the microstrip line 13 because the conductor plate 12 bonded to the back surface of the dielectric substrate 13 serves as the ground layer. Because it is.

  Further, in the converter 1 according to the present embodiment, the back short block 14 and the conductor plate 12 disposed on the front and back of the dielectric substrate 13a constituting the microstrip line 13 are insulated from each other. As a result, the back short block and the conductor plate arranged on the front and back of the dielectric substrate constituting the microstrip line are short-circuited with each other through a via formed in the dielectric substrate. Manufacturing costs can be reduced.

  Here, the via that short-circuits the back short block 14 and the conductor plate 12 can be omitted because the back short block 14 and the conductor plate 12 are capacitively coupled. According to the knowledge obtained by the inventors, even if the back short block 14 is not short-circuited to the conductor plate 12, the insertion loss can be sufficiently reduced over a sufficiently wide frequency band if the shape is sufficiently examined. It can be kept small.

  The thickness of the dielectric substrate 13a constituting the microstrip line 13 is preferably 50 μm or less. As is clear from the examples and modifications shown below, if the thickness of the dielectric substrate 13a is 50 μm or less, it is sufficient between the back short block 14 and the conductor plate 12 disposed on the front and back of the dielectric substrate 13a. Since the capacitive coupling is formed, the insertion loss can be sufficiently reduced over a sufficiently wide frequency band by appropriately setting the shape of the back short block 14.

[Example 1]
A first example of the converter 1 according to this embodiment will be described with reference to FIGS.

  In the converter 1 according to the present embodiment, each part of the converter 1 shown in FIG. 1 is configured as follows so that the operating band is the 60 GHz band (frequency band having 60 GHz as a central frequency). The free space wavelength λ corresponding to the center frequency (60 GHz) of this operating band is 5.0 mm.

  Waveguide 11: A hollow rectangular waveguide WR-15 (EIA standard) was used as the waveguide 11.

  Conductor plate 12: An opening 12a having a shape shown in FIG. 3 was formed on a copper plate having a thickness of 100 μm, and this was used as the conductor plate 12.

  Microstrip line 13: A liquid crystal polymer substrate having the shape shown in FIG. 4 and having a relative dielectric constant of 3, a dielectric loss tangent of 0.003, and a thickness of 50 μm was used as the dielectric substrate 13a. Further, a copper foil having the shape shown in FIG. 4 was formed on the front surface of the dielectric substrate 13a, and this was used as the signal line 13b.

  Back short block 14: As the back short block 14, a copper block having the shape shown in FIG. 5 was used.

  FIG. 6 is a graph illustrating frequency characteristics of | S21 | (21 components of S parameter) in the converter 1 according to the present embodiment. | S21 | is an index of insertion loss, and means that the larger the value, the smaller the insertion loss. For calculating | S21 | at each frequency, HFSS of a finite element method analysis simulator was used. The input / output ends are the opening of the waveguide 11 and the tip of the microstrip line 13.

  Referring to FIG. 6, it can be seen that | S21 | exceeds the general required level of −3 dB in a sufficiently wide band (60.3 GHz to 65 GHz).

[Modification 1]
A first modification of the converter 1 according to the first embodiment will be described with reference to FIGS.

  The converter 1 according to the present modification changes the thickness yblk1 (see FIG. 7) of the rear wall 14b3 of the back short block 14 without changing other dimensions in the converter 1 according to the first embodiment. It was obtained by this. By changing the thickness yblk1 of the side wall 14b3, an effect similar to that of forming a stub on the signal line 13b of the microstrip line 13 can be obtained.

  FIG. 8 shows the side wall normalized by the free space wavelength λ (5.0 mm) corresponding to the center frequency (60 GHz) of the operating band when the thickness yblk1 of the side wall 14b2 is changed from 0.4 mm to 2.4 mm. It is a graph which shows the frequency characteristic of | S21 | obtained when the thickness yblk1 / λ of 14b2 is changed from 0.08 to 0.48. FIG. 9 is a graph showing the yblk1 / λ dependency of the specific bandwidth FBW | S21 | in which | S21 | exceeds -3 dB.

  Referring to FIG. 9, when 0.10 ≦ yblk1 / λ ≦ 0.30, the specific bandwidth FBW exceeds 10%, that is, in the same manner as the converter 1 according to the first embodiment, It can be seen that a converter with low insertion loss can be realized.

[Modification 2]
A second modification of the converter 1 according to the first embodiment will be described with reference to FIGS.

  The converter 1 according to the present modification changes the thickness xblk1 (see FIG. 10) of the side wall 14b2 of the back short block 14 without changing other dimensions in the converter 1 according to the first embodiment. Is obtained. By changing the thickness xblk1 of the side wall 14b2, an effect similar to that of forming a stub in the signal line 13b of the microstrip line 13 can be obtained.

  FIG. 11 shows the side wall normalized when the thickness xblk1 of the side wall 14b2 is changed from 0.12 mm to 2.2 mm, that is, the free space wavelength λ (5.0 mm) corresponding to the center frequency (60 GHz) of the operating band. 14 is a graph showing the frequency characteristics of | S21 | obtained when the thickness xblk1 / λ of 14b2 is changed from 0.12 to 0.44. FIG. 12 is a graph showing the xblk1 / λ dependency of the specific bandwidth FBW | S21 | in which | S21 | exceeds -3 dB.

  Referring to FIG. 12, when 0.10 ≦ xblk1 / λ ≦ 0.52, the specific bandwidth FBW exceeds 10%, that is, as in the converter 1 according to the first embodiment, the bandwidth is wide. It can be seen that a converter with low insertion loss can be realized.

[Modification 3]
A third modification of the converter 1 according to the first embodiment will be described with reference to FIGS.

  The converter 1 according to this modification is the same as the converter 1 according to the first embodiment, except that the thickness lbf (see FIG. 13) of the front wall 14b1 of the back short block 14 is changed only on one side without changing other dimensions. It was obtained by changing. By changing the thickness lbf of the front wall 14b1 only on one side, an effect similar to that of forming a stub on the signal line 13b of the microstrip line 13 can be obtained.

  FIG. 14 shows the standard when the thickness lbf of the front wall 14b1 is changed from 1.09 mm to 2.49 mm on only one side, that is, the free space wavelength λ (5.0 mm) corresponding to the center frequency (60 GHz) of the operating band. It is a graph which shows the frequency characteristic of | S21 | obtained when the thickness lbf / λ of the converted front wall 14b1 is changed from 0.218 to 0.498 only on one side. FIG. 15 is a graph showing the lbf / λ dependency of the specific bandwidth FBW | S21 | in which | S21 | exceeds -3 dB.

  Referring to FIG. 15, when 0.31 ≦ lbf / λ ≦ 0.43, the specific bandwidth FBW exceeds 10%, that is, as in the converter 1 according to the first embodiment, It can be seen that a converter with low insertion loss can be realized.

[Modification 4]
A fourth modification of the converter 1 according to the first embodiment will be described with reference to FIGS. 13, 16, and 17. FIG.

  The converter 1 according to this modification is the same as that of the converter 1 according to the first embodiment, with the thickness lbf (see FIG. 13) of the front wall 14b1 of the back short block 14 on both sides without changing other dimensions. It was obtained by changing. By changing the thickness lbf of the front wall 14b1 on both sides, an effect similar to that of forming a stub on the signal line 13b of the microstrip line 13 can be obtained.

  FIG. 16 shows a standard when the thickness lbf of the front wall 14b1 is changed from 1.09 mm to 3.49 mm on both sides, that is, at a free space wavelength λ (5.0 mm) corresponding to the center frequency (60 GHz) of the operating band. It is a graph which shows the frequency characteristic of | S21 | obtained when the thickness lbf of the converted front wall 14b1 is changed from 0.218 to 0.698 on both sides. FIG. 17 is a graph showing the lbf / λ dependency of the specific bandwidth FBW | S21 | in the band where | S21 | exceeds -3 dB.

  Referring to FIG. 17, when 0.25 ≦ lbf / λ ≦ 0.76, the specific bandwidth FBW exceeds 10%, that is, as in the converter 1 according to the first embodiment, the bandwidth is wide. It can be seen that a converter with low insertion loss can be realized.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be used, for example, in a high frequency circuit that processes a high frequency signal belonging to the millimeter wave band.

DESCRIPTION OF SYMBOLS 1 Converter 11 Waveguide 11a Tube wall 11b Waveguide area | region 12 Conductor plate 12a Opening 13 Microstrip line 13a Dielectric board | substrate 13b Signal line 13c Waveguide area | region 14 Back short block (conductor block)
14a Concave part 14b1 Front wall 14b2 Side wall 14b3 Rear wall

Claims (6)

A conductor plate in which an opening is formed;
A waveguide directly joined to the back surface of the conductor plate so that the inside of the tube communicates with the opening;
A microstrip line comprising a single-sided mounting substrate having a dielectric substrate and a signal line formed on the surface of the dielectric substrate, wherein the back surface of the dielectric substrate is arranged such that the tip of the signal line overlaps the opening. A microstrip line directly bonded to the surface of the conductor plate;
A conductor block formed with a recess opened to the bottom surface and the side surface, wherein the bottom surface is joined to the surface of the dielectric substrate so that the signal line enters the recess from the side surface; , And
The conductor plate and the conductor block are insulated from each other;
A converter characterized by that. The dielectric substrate has a thickness of 50 μm or less.
The converter according to claim 1. The conductor block has a rectangular parallelepiped shape,
The concave portion has a T-shape in plan view,
The space in the recess is surrounded on all sides by a front wall having an open center, a pair of side walls perpendicular to the front wall, and a rear wall facing the front wall.
The converter according to claim 1 or 2, characterized by the above-mentioned. The thickness of the rear wall normalized by a free space wavelength corresponding to the center frequency of the operating band of the converter is 0.08 or more and 0.48 or less.
The converter according to claim 3. The thickness of the side wall normalized by the free space wavelength corresponding to the center frequency of the operating band of the converter is 0.10 or more and 0.30 or less.
The converter of any one of Claims 3-4 characterized by the above-mentioned. The thickness of the front wall normalized by a free space wavelength corresponding to the center frequency of the operating band of the converter is 0.25 or more and 0.76 or less,
The converter according to any one of claims 3 to 5, wherein:

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