JP5646940B2 - Electromagnetic wave transmission medium - Google Patents

Description

  The present invention mainly relates to an electromagnetic wave transmission medium for connecting between high-frequency devices in the microwave band or higher, particularly 100 GHz band or higher, or between high-frequency devices and devices.

  There are coaxial lines and flexible waveguides as electromagnetic wave transmission media for connecting high-frequency devices whose relative positions cannot be accurately determined or where one or both positions change. Coaxial lines are often used because they are flexible and relatively inexpensive. However, as the frequency increases, the diameter needs to be reduced, increasing the transmission loss and improving the machining accuracy to maintain the transmission characteristics. Problems such as a rise and a decrease in durability occur. For example, when Teflon (registered trademark) is used as an insulator and the cutoff frequency fc is set to 100 [GHz] with a coaxial line, the inner diameter becomes about 1 [mm]. In such a thin coaxial line, not only the loss increases, but a slight mechanical error greatly affects the transmission characteristics.

  A flexible waveguide is excellent from the viewpoint of preventing transmission loss, but the flexible waveguide needs to be formed into a special shape (for example, bellows) in the tube wall portion (Patent Document 1, 2), production efficiency is extremely poor. In addition, the flexible waveguide requires a complicated and advanced processing technique in order to realize a structure that can be used up to, for example, a millimeter wave band exceeding 30 [GHz]. Further, such a thin flexible waveguide lacks durability.

  There is not a bellows-shaped metal waveguide but also a waveguide having an elliptical cross section in which a thin conductor is stuck on the surface of a dielectric rod without any gap (Patent Document 3). Such a waveguide has an advantage that it can be manufactured at a low cost because a waveguide can be obtained simply by winding a metal tape on the surface of the dielectric rod after forming the dielectric rod or applying a conductive plating. . However, such a waveguide has a large transmission loss and is not flexible enough. Furthermore, since the cross section is elliptical, the transmission mode becomes unstable with respect to bending, and the problem that the characteristics change remains.

  In order to solve such problems, the present inventors have disclosed an electromagnetic wave transmission medium that does not adversely affect the transmission mode even if bending occurs without increasing the manufacturing cost even if the frequency band of the electromagnetic wave used is high. (Patent Document 4). In this electromagnetic wave transmission medium, the cylindrical tube is molded so that the cross-sectional shape in the direction orthogonal to the tube axis is the same in the tube axis direction, and the impedance range matched by the ridge portion can be widened. Processing becomes easier compared to waveguides, coaxial lines, and the like. Further, since the ridge portion acts as a reinforcing material when bending occurs and the transmission mode can be stabilized, an excellent effect is obtained in that deterioration of characteristics due to bending can be suppressed.

Japanese Utility Model Publication No. 41-018451 Japanese Utility Model Publication No. 45-018273 JP-A-8-195605 JP 2010-16714 A

The electromagnetic wave transmission medium disclosed in Patent Document 4 has excellent effects as described above. However, in this electromagnetic wave transmission medium, there is an aspect in which the cross-sectional shape of the cylindrical tube is asymmetric with respect to the center. Therefore, although it is easier to process than a coaxial line having a conventional structure, it has been necessary to improve to a structure that can further improve the ease of processing and enhance the deformation resistance due to bending in all directions.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an electromagnetic wave transmission medium that is easier to process and that is resistant to deformation due to bending.

An electromagnetic wave transmission medium provided by the present invention has a cylindrical tube formed so that a cross section in a direction orthogonal to the tube axis has the same shape in the tube axis direction, and the inner wall of the cylindrical tube has a skin depth. The cross-sectional shape has n pairs (n is a natural number of 1 or more) ridges directed to the cylinder axis, and the cylindrical tube is bent. and is also a closed surface shape ridge portions of each pair to keep the line symmetry, thereby, the n is can be transmitted while the signal n is maintaining mutually independent through the ridge portion of the pair, the ridge portions of each pair Is characterized in that high-frequency power is fed independently from a portion different from each of the other pair of ridge portions.

  More specifically, the shape of the cross section of the electromagnetic wave transmission medium of the present invention is more specifically the first circle corresponding to the inner diameter of the cylindrical tube, and the inner wall of the first circle than the first circle, respectively. A closed curved surface shape is formed by integrally connecting the outer walls of n pairs of small circles having a small inner diameter, and each small circle forms the ridge portion.

In one embodiment, a line connecting opposing ridge portions includes two pairs of ridge portions that are orthogonal to each other on the cross section, and high frequency power of a first frequency is supplied to a predetermined portion of one pair of ridge portions. first and feed point exists of approximately 1/2 but only distant sites one at a by propagation wavelength of the RF power of the first frequency from the first feeding point of the ridge portion of the other pair Has a second feeding point for feeding high-frequency power having a second frequency different from the first frequency.

  The size of the cross section is, for example, that the free space velocity of electromagnetic waves is C, the total length of arcs that follow the inner circumference of the first circle is L, and the dielectric constant of the internal space of the cylindrical tube is ε. In some cases, the electromagnetic wave introduced into the internal space has a size that blocks the electromagnetic wave with a cutoff frequency fc (= 1.84 C / (√εL). The internal space may be a free space and is filled with a dielectric. May be.

In the electromagnetic wave transmission medium of the present invention, the cylindrical tube is molded so that the cross-sectional shape in the direction orthogonal to the tube axis is the same in the tube axis direction, and the impedance range matched by the ridge portion can be widened. Therefore, even if the frequency is increased (for example, even in a millimeter wave band of 100 GHz or more), the processing is easy, and there is an effect that the mass productivity is excellent.
Further, the cross-sectional shape of the electromagnetic wave transmission medium of the present invention is a circular ridge waveguide shape in which n pairs of ridge portions are symmetrical with respect to the center of the tubular tube, so that processing is easy and deformation by bending in all directions is possible. Resistance can be increased over existing ones.
Since the n pairs of ridge portions act as a reinforcing material when bending occurs, the deformation resistance due to bending can be increased as compared with the existing ones, and the transmission state can be stabilized, thereby suppressing deterioration of characteristics. be able to. Furthermore, since high frequency power is supplied to one ridge portion of each pair of ridge portions, n types of high frequency power can be transmitted simultaneously.

The perspective view which shows the cross-sectional structure example of 1st Embodiment of the cylindrical pipe | tube to which this invention is applied. Explanatory drawing which showed the electric field distribution of the cylindrical tube of 1st Embodiment. Side surface sectional drawing which shows the coupling structure of a cylindrical tube and a coaxial line. Sectional drawing in the B point of FIG. Sectional drawing in the C point of FIG. The passage characteristic figure of the cylindrical tube of a 1st embodiment. The transmission characteristic figure of the coaxial line shown as reference. The signal separation degree of the cylindrical tube of 1st Embodiment. The characteristic view which showed the change of the reflected power of the cylindrical tube of 1st Embodiment. Explanatory drawing of the measurement system of the high frequency device shown as an example of application of a cylindrical tube. The perspective view which shows the cross-section structural example of the cylindrical pipe | tube of 2nd Embodiment. The passage characteristic figure of the cylindrical pipe of a 2nd embodiment. The characteristic view which showed the change of the reflected power of the cylindrical tube of 2nd Embodiment. Sectional drawing of the cylindrical pipe | tube of 3rd Embodiment. Sectional drawing of the cylindrical pipe | tube of 4th Embodiment. The passage characteristic figure of the cylindrical pipe of a 4th embodiment. The characteristic view which showed the change of the reflected power of the cylindrical tube of 4th Embodiment. The signal separation degree of the cylindrical tube of 4th Embodiment.

Embodiments of an electromagnetic wave transmission medium according to the present invention will be described below with reference to the drawings.
[First Embodiment]
An electromagnetic wave transmission medium to which the present invention is applied mainly includes a flexible cylindrical tube and n pairs (n is a natural number of 1 or more) of internal conductors in which a part of the outer wall is connected to the inner wall of the cylindrical tube. Include as an element.
FIG. 1 is a perspective view showing an example of a cross-sectional shape in a direction perpendicular to the tube axis in a cylindrical tube where n is 2. As shown in FIG. The cylindrical tube 1 illustrated in FIG. 1 is symmetrical with respect to the first circle 1a and the center of the first circle (the tube axis of the tubular tube 1) inside the first circle 1a. A pair of the second circle 1b and the third circle 1c arranged in the first circle 1a, symmetrical with respect to the center of the first circle inside the first circle 1a, and the center of the second circle 1b and the third circle A closed curved surface is formed by connecting a pair of a fourth circle 1d and a fifth circle 1e located on an axis orthogonal to the axis connecting the center of the circle 1c.
A space surrounded by the arcs of the second to fifth circles 1b to 1e is referred to as a depressed space 40 in this specification. As the arc angles of the second to fifth circles 1b to 1e, values in the range of 90 degrees to 180 degrees in the left-right direction from the target axis can be employed, respectively, depending on the frequency to be used. In the case of 180 degrees, the depressed space 40 has a shape in which the second to fifth circles 1b to 1e are inscribed on the inner wall of the first circle 1a. The cross-sectional shape of FIG. 1 is molded so as to be the same in the tube axis direction of the tubular tube 1.

A portion of the tubular tube 1 corresponding to the first circle 1a is made of a conductor whose thickness is at least equal to or greater than the skin depth. However, since the portion in contact with the transmission space 30 for propagating the electromagnetic wave only needs to be a conductor, a conductive layer having a skin depth or more may be provided on the surface of a member that can be easily processed, such as resin. The conductor or conductive layer is made of gold, silver, copper, or a combination thereof.
“Skin depth” refers to the distance from the surface where the high frequency current is 37% of the surface due to the skin effect. At this distance, the high frequency current becomes 1 / e of the surface value. e is the base of natural logarithm (about 2.72), and 1 / e is about 0.37. The loss that occurs in the conductor or conductive layer is approximately given by the ohmic loss when it is assumed that it flows uniformly from the surface to the skin depth. The skin depth is about several microns or less in the millimeter wave band.

  The tubular tube 1 of this embodiment has both ends, and applies high frequency power of a first frequency to a pair of inner conductors on one end side, and a first frequency to the other pair of inner conductors. 2, an electric field E1 (broken line) generated by the high frequency power of the first frequency and an electric field E2 (solid line) generated by the high frequency power of the second frequency, as shown in FIG. Is excited.

A pair of inner conductors that are symmetrical about the tube axis function as a double ridge. Therefore, in the following description, the inner conductor whose cross section consists of a pair of the second circle 1b and the third circle 1c is the first double ridge, and the cross section thereof is the pair of the fourth circle 1d and the fifth circle 1e. The inner conductor formed is called a second double ridge. Further, when there is no need to distinguish each internal conductor, it is called a “ridge portion”.
The signal of the electric field E1 propagates in the tube axis direction of the tubular tube 1 while the electric field direction is constrained in the direction connecting the inner conductors constituting the first double ridge in the shortest direction, while the signal of the electric field E2 is 2 Propagates in the tube axis direction of the tubular tube 1 while the electric field direction is constrained in the direction connecting the inner conductors constituting the double ridge in the shortest direction.

  As a result, the signal of the electric field E1 and the signal of the electric field E2 can be taken out independently in the cross section of the other end of the cylindrical tube 1. While these two signals propagate, the electric field directions of the signals, that is, the directions of the electric fields E1 and E2, are electrically orthogonal to each other, so that the signals are not coupled to each other. That is, the electromagnetic waves of the vertically polarized wave and the horizontally polarized wave basically do not affect each other, and the signal of the electric field E1 and the signal of the electric field E2 do not interfere with each other during propagation. Even if crosstalk occurs between two signals, it is generated depending on the mechanical symmetry error of the cross-sectional shape or the error of orthogonality, so adjust these mechanical conditions. Can be reduced. Even if the cylindrical tube 1 is bent around the axis or in a direction perpendicular to the axis, if the mechanical symmetry in the cross section is maintained, the two signals are transmitted while maintaining independence from each other. The

<Coupled with coaxial line>
High-frequency power is supplied to the tubular tube 1 through a coaxial line or the like. 3 is a side cross-sectional view in the tube axis direction of the tubular tube 1 showing a coupling structure of the tubular tube 1 and the coaxial line, FIG. 4 is a cross-sectional view at point B in FIG. 3, and FIG. It is sectional drawing in the C point of FIG.
In the coaxial line, the center conductor 2a provided at the center of the connection medium 2 is a distance away from the short-circuited surface (point A) of the tubular tube 1 by a predetermined distance L1 (= approximately ¼λ (λ is a propagation wavelength)). ) (Point B) is connected to a ridge portion having a cross section of a circle 1e through a connection medium 2 penetrating the ridge portion having a cross section of a circle 1d, and an electric field E1 is excited in this direction.

In the other coaxial line, the central conductor 2b provided at the center of the connection medium 2 is located at a portion (point C) of L2 (= a distance of about 1 / 2λ (λ is a propagation wavelength)) from the point B. The connection medium 2 passing through the ridge having a cross section of a circle 1c is connected to the ridge having a cross section of a circle 1b, and the electric field E2 is excited in this direction.
The excited signals of the electric fields E1 and E2 propagate in the axial direction of the cylindrical tube in the transmission space 30 of the cylindrical tube 1 while being electrically orthogonal to each other.
On the receiving side, the signals of the electric fields E1 and E2 are transmitted to the coaxial line by the coupling structure having the same positional relationship as in FIGS.

<Characteristic>
Next, the characteristics of the cylindrical tube 1 will be described.
The inner diameter of the first circle 1a is D, the outer diameter of the second to fifth circles 1b to 1e is d, the number of the second to fifth circles is N (= 4), the cutoff frequency is fc, and the cutoff wavelength is λc. Then, the cut-off frequency fc when the second to fifth circles 1b to 1e are in contact with the first circle 1a can be approximately calculated by the following expression. C is the free space velocity of the electromagnetic wave.
fc = C / λc
= 1.84C / (π√ε (D + Nd))

Further, the second to fifth circles 1b to 1e are in contact with the first circle 1a, and the centers of the second to fifth circles 1b to 1e are offset to the outside. And the cut-off frequency fc and cut-off wavelength λc can be replaced as follows using the total arc L measured along the inner circumference of the cross section. it can.
fc = C / λc
= 1.84C / (√εL)

  The cut-off frequency fc must be lower than the operating frequency, contrary to the coaxial line, so that the thickness restriction is imposed on the coaxial line, whereas the tubular tube 1 is limited in thinness. It is done. For this reason, it is extremely advantageous in terms of processing at very high frequencies. The transmission characteristic impedance is determined by d / D. In the case of the tubular tube 1, d / D can be selected to be about 0.25 to 0.5. This ratio is comprehensively determined from the relationship between the external size, cutoff frequency, loss, and flexibility.

  Further, the center of the second to fifth circles 1b to 1e is slightly offset to the outside with respect to the condition that the relatively small second to fifth circles 1b to 1e are in contact with the relatively large first circle. As a result, the circles partially overlap and a part of the arc is lost. Assuming that the offset amount is the center shift dimension from the inscribed position of the second to fifth circles 1b to 1e / the radius of the second to fifth circles 1b to 1e, this offset amount is the twist of the tubular tube 1, For the purpose of stably transmitting polarized waves against bending, 0 (position where the second to fifth circles 1b to 1e are inscribed in the first circle 1a) to 0.5 (second to fifth circles 1b to 1b) A value greater than or equal to the position at which 1e is half buried in the first circle 1a is selected.

  That is, when the tubular tube 1 is not twisted or bent or is extremely small even if it occurs, the offset amount is 1 (the second to fifth circles 1b to 1e are completely buried in the first circle 1a, However, when the twist or bend of the transmission medium increases, the offset amount decreases so as to approach 0 in order to withstand this and transmit the polarization stably. It is necessary to let When the offset amount approaches 0, the cross-sectional area of the transmission space 30 decreases, and the angle formed by the arcs in contact therewith becomes an acute angle, the current density flowing on the inner wall surface of the tubular tube 1 and the skin effect increase, causing an increase in loss. It becomes. Further, when the convexity toward the inside becomes deep, the degree of difficulty in production increases. In consideration of such difficulty in manufacture and electrical characteristics (transmission state stability against transmission and bending and transmission loss), the offset amount is preferably selected between 0.25 and 0.75.

Next, D = 2mm, d = 0.6mm, offset = 0.03mm / 0.3mm, d / D = 0.3, offset = 0.1, the characteristics of the cylindrical tube 1 made of copper are concrete I will explain it.
FIG. 6 is a transmission characteristic diagram per line length of 5 mm, and shows an example in the range of 100 GHz to 330 GHz.
FIG. 7 is a pass characteristic diagram of a coaxial line that can be used up to 330 GHz.
When transmitting a signal with a high frequency in this way, the coaxial line needs to have a diameter of the outer conductor of less than 0.3 mm, but the cylindrical tube 1 of the present embodiment suffices with a size six times that of the coaxial line. It can be seen that the processing becomes much easier.
In the case of a coaxial line, for example, the passage loss at 150 GHz is at least about 3 dB per 100 mm, whereas the tubular tube 1 of the present embodiment is about 0.7 dB, and the passage loss can be greatly reduced. Recognize.

  FIG. 8 is a characteristic diagram showing an example of the signal separation of the cylindrical tube 1 configured under the same conditions as in FIG. 6 in the range of 100 GHz to 330 GHz. It can be seen that the tubular tube 1 of the present embodiment can achieve a signal separation of approximately 50 dB over a wide band of 120 GHz to 300 GHz, and can transmit two signals that are practically independent simultaneously.

  FIG. 9 is a characteristic diagram showing an example of the reflected power of the cylindrical tube 1 configured under the same conditions as in FIG. 6 in the range of 100 GHz to 330 GHz. It can be seen that the reflected power is also good over a wide band.

<Application example>
FIG. 10 is an explanatory diagram when the cylindrical tube 1 of the present embodiment is applied to a measurement system for a high-frequency device. The illustrated measurement system includes a test probe 5 having a high-frequency two-signal arrangement in which a coaxial line 4 and a signal (S) and ground (G) are combined between a high-frequency measuring device 3 and a two-terminal pair high-frequency device 6. A cylindrical tube 1 capable of transmitting two independent signals simultaneously is provided. Since the cylindrical tube 1 has a lower loss than the coaxial line 4, the distance can be extended by that amount, and two signals can be shared and transmitted through a single flexible, durable and inexpensive transmission line. In this case, the transmission line can be routed smoothly and the convenience of measurement can be improved.

<Production method>
The cylindrical tube 1 can be manufactured as follows.
First, a die that leaves the transmission space 30 in the above-described closed curved surface is created, and the base is drawn and molded using this die. As a result, an outer sheath (outer wall of the first circle 1a) and two pairs of double ridges are formed, and the entire cross section is circular. The pultrusion molding is a molding method in which a base is drawn from a steel die to obtain a cylinder having a closed curved section. Because it can extend as much as necessary in a substantially vertical direction with respect to the cross section of the tube that is perpendicular to the tube axis, the molded product has increased strength in one direction while maintaining the same cross-sectional shape. The (tubular tube 1) can be mass-produced.

  The outer sheath includes glass fibers and other reinforcing members for improving the buckling strength against bending. In order to make bending easier, it may have an appropriate elastomeric property. After pultrusion with a punching die, base plating for increasing the peel strength and surface plating for reducing skin resistance are applied to the transmission space 30 as necessary. A diffusion prevention layer may be sandwiched between the base plating and the surface plating as necessary. The surface plating forms a conductive layer.

  Since the transmission space 30 is a free space, it can contribute to an improvement in transmission loss, but the transmission space 30 may be filled with a dielectric. In this case, although the loss increases compared with the free space, it is possible to improve the buckling strength against the bending of the transmission path and to electrically shorten the transmission path diameter.

In the cylindrical tube 1 manufactured in this way, the transmission mode of the electromagnetic wave introduced into the transmission space 30 is substantially the same as that of the rectangular waveguide and the circular waveguide in that it has a pair of electric field poles in the cross section. It will be the same. That is, as shown in the electric field distribution diagram of FIG. 2, the cylindrical tube 1 substantially inherits the electric field distribution characteristic of the double ridge waveguide, which is an application of a circular waveguide and a rectangular waveguide.
In particular, in the example of this embodiment, by making the arcs of the second to fifth circles 1b to 1e act as ridge portions, not only the impedance matching range is expanded, but also the position of the electric field electrode is changed. Since it can be fixed, the transmission mode in the transmission space 30 can be stabilized even when bending occurs. This is very different from a circular waveguide or coaxial line whose electric field distribution changes due to bending.

[Second Embodiment]
The electromagnetic wave transmission medium of the present invention can be implemented in forms other than the first embodiment.
For example, the cylindrical tube illustrated in FIG. 11 has a cross-sectional shape in a direction orthogonal to the tube axis, and a pair of ridges, that is, a second circle 1b and a third circle 1c, on the inner wall of the first circle 1a. Forms a closed surface that connects pairs of. This cross-sectional shape is molded so as to be the same in the tube axis direction of the cylindrical tube.
FIG. 12 is a pass characteristic diagram when D = 1.8 mm, d = 0.9 mm, (d / D = 0.5), and offset 0.25 mm / 0.45 mm = 0.5. FIG. 13 shows the characteristics of the reflected power under the same conditions as in FIG.

[Third Embodiment]
In the first embodiment and the second embodiment, an example in which all the ridge portions have the same shape and size is shown, but the paired ridge portions have the same shape and size and are symmetrical with respect to the tube axis. For example, as shown in FIG. 14, circles 1 b ′ and 1 c ′ having different diameters may be provided at the portions of the second circle 1 b and the third circle 1 c described so far. good.

[Fourth Embodiment]
In the electromagnetic wave transmission medium of the present invention, four pairs of ridge portions can be provided.
For example, FIG. 15 shows the sixth circle 1f between the second circle 1b and the fourth circle 1d described in the first embodiment, and the eighth circle between the fourth circle 1d and the third circle 1c. A seventh circle 1g is provided between the circle 1h, the third circle 1c and the fifth circle 1e, and a ninth circle 1i is provided between the fifth circle 1e and the second circle 1b. The sixth circle 1f and the seventh circle 1g that are symmetric form a third double bridge, and the eighth circle 1h and the ninth circle 1i that are also symmetric with respect to the tube axis are the fourth A double bridge is formed. The outer diameters of the second to fifth circles 1b to 1e are d1, and the outer diameters of the sixth to ninth circles 1f to 1i are d2 (<d1).

FIG. 16 is a passage characteristic diagram of the cylindrical tube in the fourth embodiment, where D = 2 mm, d1 = 0.6 mm (d1 / D = 0.3), and offset 0.03 / 0.3 mm = 0.1. , D2 = 0.4 mm (d2 / D = 0.2) and offset 0.04 / 0.2 mm = 0.2. FIG. 17 shows the reflected power of the tubular tube in the fourth embodiment, and FIG. 18 shows the signal separation of the four signals.
It can be seen that practical results are obtained in both cases.

As described above, the cylindrical tube as an example of the electromagnetic wave transmission medium of the present invention is formed into a shape in which the cross section in the direction orthogonal to the tube axis is the same in the tube axis direction, and is in contact with the transmission space 30 Is formed of a conductor having a thickness equal to or greater than the skin depth, and the cross-sectional shape has n pairs (n is a natural number of 1 or more) of ridges directed to the cylinder axis, and each pair of ridges is a line. Since it is a closed curved surface that is symmetrical, the ridge portion acts as a reinforcing material, and the deformation resistance due to bending can be increased compared to the existing ones, and the transmission state can be stabilized, so that deterioration of characteristics can be suppressed. . In addition, since the matching impedance range can be widened by the presence of the ridge portion, the processing is facilitated because it is not necessary to reduce the size even in the millimeter wave band of 100 GHz or higher.
Furthermore, since high frequency power is independently fed to each pair of ridge portions from a portion different from each other pair of ridge portions, a plurality of signals can be transmitted simultaneously with one cylindrical tube.

DESCRIPTION OF SYMBOLS 1 Cylindrical tube 1a 1st circle | round | yen 1b-1i, 1b ', 1c' used as an outer conductor 2nd-9th circle used as an inner conductor 2 Connection medium 2a, 2b Center conductor of a coaxial line 3 High frequency measuring instrument 4 Coaxial Line 5 Test probe 6 Two-terminal pair high-frequency device 20 Outer sheath 30 Transmission space 40 Sink space

Claims (6)

Having a tubular tube molded so that the cross section in the direction perpendicular to the tube axis has the same shape in the tube axis direction;
The cylindrical tube is formed of a conductor whose inner wall has a thickness equal to or greater than the skin depth,
The cross-sectional shape has n pairs (n is a natural number greater than or equal to 1) of ridges directed to the cylinder axis, and each pair of ridges maintains line symmetry even when the cylindrical tube is bent. A curved surface , whereby the n signals can be transmitted while being independent from each other through the n pairs of ridges;
An electromagnetic wave transmission medium in which each pair of ridges is independently supplied with high-frequency power from a different part from the other pair of ridges.   In the cross section, a first circle corresponding to the inner diameter of the cylindrical tube and an outer wall of n pairs of small circles each having an inner diameter smaller than the first circle are integrally connected to the inner wall of the first circle. The electromagnetic wave transmission medium according to claim 1, wherein each of the small circles forms the ridge portion. The line connecting the opposing ridge portions includes two pairs of ridge portions orthogonal on the cross section,
There is a first feeding point for feeding high-frequency power of the first frequency at a predetermined portion of one pair of ridge portions,
Be one of the ridge portion of the other pair wherein the substantially 1/2 but only distant sites of the first propagation wavelength of the RF power of the first frequency from the feed point, a second frequency different from the first frequency The electromagnetic wave transmission medium according to claim 2, wherein there is a second feeding point for feeding the high-frequency power.   When the free space velocity of electromagnetic waves is C, the total length of arcs that follow the inner circumference of the first circle is L, and the dielectric constant of the internal space of the cylindrical tube is ε The electromagnetic wave transmission medium according to claim 3, wherein the electromagnetic wave introduced into the internal space has a size that blocks an electromagnetic wave at a cutoff frequency fc (= 1.84 C / (√εL).   The electromagnetic wave transmission medium according to claim 4, wherein the internal space is a free space. The electromagnetic wave transmission medium according to claim 4, wherein the internal space is filled with a dielectric.

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