JP2001237617A - Transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission line suitable for small-loss transmission to be used in high frequency bands and to provide the producing method therefor. SOLUTION: A transmission line 1 is provided with low and high dielectric constant parts 11 and 12 as first and second dielectrics for forming a three- dimensional cyclic structure with a prescribed cutoff frequency band and, as main components a waveguide area 12 which does not have the prescribed cutoff frequency band. At least any one of first and second dielectrics is formed of dielectric materials containing high polymer materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line mainly used in a high frequency band (including a microwave band, a quasi-millimeter wave band, a millimeter wave band, and a submillimeter wave band in the present application).

The present invention relates to a resonator, an oscillator, a directional coupler, a branch, and a filter used in satellite communication equipment, mobile communication equipment, wireless communication equipment, high-frequency / ultra-high-frequency communication equipment, and their base stations. It is suitable for use as a transmission line having a predetermined cut-off frequency band that constitutes an IC circuit board or the like.

[0003]

2. Description of the Related Art In high-frequency / ultra-high-frequency communication from a microwave band to a quasi-millimeter wave band, a millimeter wave band, and a submillimeter wave band, a transmission line is used as a basic technology for forming a resonator, a filter, and the like. As the transmission line, a strip line, a coplanar line, or a triplate line is widely used in a microwave band, and an NRD line is used in a millimeter wave band.

In a conventional microwave transmission line,
For example, “Microwave” (The University of Tokyo Press, 1983)
As described in (1), by forming electrodes made of a metal such as copper (Cu) or silver (Ag) on the surface or inside of a polymer material, strip lines, coplanar lines, and triplate lines can be formed. Make up. In the millimeter wave band, for example, in Japanese Patent No. 2692328, as shown in FIG. 10, an NRD line having a configuration in which a dielectric strip 82 is sandwiched between metal parts 81 is used as a transmission line.

On the other hand, a photonic crystal having a photonic band gap has an embodiment in which a refractive index changing region is formed for application to an optical waveguide or an optical filter for an optical communication system. No. 2,186,627.

[0006]

However, in a strip line or a coplanar line, since the transmission electrodes are arranged on the outer surface of the dielectric portion, electromagnetic field radiation loss to the outside air occurs, and the entire transmission line is lost. However, there is a problem that the loss is large. Further, since the transmission line on which the electromagnetic field is concentrated is exposed to the outer surface, the transmission line is easily affected by external noise.

Although the above-mentioned problem does not occur in the triplate line, since the electrodes are formed inside the dielectric, voids, cracks, and peeling occur at the interface between the electrodes and the dielectric, so that the quality of the product is constant. There is a problem that not.

Another problem common to strip lines, coplanar lines, and triplate lines is that the surface of the metal electrode must be roughened because the adhesive strength between the polymer material and the metal electrode is weak, and the principle of the skin effect. Therefore, there is a problem that high-frequency current flowing intensively on the metal surface is affected and metal loss is greatly increased.

In the NRD line, since there are many constituent members, high cost is required for assembly. There is also a disadvantage that transmission characteristics become unstable due to assembly variations. The combination of separate metal plates and dielectric strips is unsuitable for integration and difficult to combine with other devices, which limits the development of high-frequency and ultra-high-frequency modules.

A strip line and a coplanar line,
Since all transmission lines of the triplate line and the NRD line are composed of a dielectric part and a metal part, the transmission loss includes not only the dielectric loss derived from the dielectric material but also the metal loss due to the metal part. Have been. In addition, there is also a problem that the device becomes heavy because it contains a metal having a large specific gravity.

Further, for example, when a structure containing holes is used, there is an advantage that the weight of the transmission line can be reduced, but on the other hand, the mechanical strength becomes insufficient, the moisture resistance is poor, and the desired reliability is obtained. Or the problem of not being obtained.

An object of the present invention is to provide a transmission line suitable for exhibiting low-loss transmission characteristics. Another object of the present invention is to provide a lightweight transmission line which can be manufactured at low cost with good reproducibility and has a flexible shape.

[0013]

The object of the present invention is to provide a first dielectric having a first dielectric constant and a second dielectric having a second dielectric constant different from the first dielectric constant. And the first
And a periodic structure in which the second dielectric is arranged at a predetermined period;
A transmission line comprising a predetermined cutoff frequency band defined based on the first and second dielectric constants and the period so as to prohibit propagation of a predetermined electromagnetic wave in a high frequency band. Achieved by

In the transmission line of the present invention, the periodic structure is a three-dimensional periodic structure in which the first and second dielectrics are three-dimensionally arranged at a predetermined period.
Further, the first dielectric is formed of a dielectric material containing at least one of a polymer material and a ceramic material.

Further, the second dielectric is made of a dielectric material including a polymer material.
Still further, the dielectric material of the second dielectric includes a ceramic material. Alternatively, the dielectric material of the second dielectric is made of a composite material containing two or more polymer materials.

The transmission line of the present invention, wherein the first
The dielectric material of the second dielectric has a laminated structure. Further, in the transmission line of the present invention,
It is characterized by including a transmission area where the periodic structure is not formed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A transmission line according to an embodiment of the present invention will be described with reference to FIGS. First, a schematic configuration of the transmission line according to the present embodiment will be described with reference to FIGS. FIG. 1 is a perspective view showing an example of a transmission line having a three-dimensional periodic structure having a predetermined cutoff frequency band according to the present embodiment. FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. Is shown.

The transmission line 1 according to the present embodiment has a three-dimensional periodic structure having a predetermined cut-off frequency band. The transmission line 1 includes a low dielectric constant material portion 11 and a high dielectric constant material portion 12 serving as a first dielectric or a second dielectric forming a periodic structure serving as a predetermined cutoff frequency band, and a predetermined cutoff. A waveguide region (transmission region) 13 having no frequency band is provided as a main component.

Here, the transmission line 1 according to the present embodiment
Now, the principle of generating a predetermined cutoff frequency band will be described. In the high frequency and ultra high frequency band, the electromagnetic wave of the wavelength lambda in vacuum, case of propagating material of a relative dielectric constant epsilon _gamma, occur wavelength shortening effect, becomes actually transmitted that as a wave of λ / √ε _γ. If the boundary condition of the period a exists in this substance, Bragg reflection occurs in which the incident wave is canceled out as the reflected wave when the following condition is satisfied.

[0020]

(Equation 1)

If this material forms a periodic structure three-dimensionally with dielectric materials having different relative dielectric constants, electromagnetic waves having the above-mentioned wavelengths are blocked from propagating in all directions. That is, when the substance has the boundary condition of the period a in all of the x, y, and z directions,

[0022]

(Equation 2)

The frequency can no longer exist as a wave. Here, c is the speed of light. In this way, by forming a three-dimensional periodic structure with dielectric materials having different relative dielectric constants and controlling the period and relative dielectric constant, a cut-off frequency band that prohibits any propagation in all directions in the material is created. be able to. The above is theoretically considered from the mask well equation. The following equation describing the electromagnetic field

[0024]

(Equation 3) Considering the rotation of

[0025]

(Equation 4)

Is obtained. Since we consider a three-dimensional periodic structure, this material has the same Bloch theorem as a normal crystal, and the basic translation vector of the periodic lattice

(Equation 5) Against

[0027]

(Equation 6) If a vector-valued function that satisfies is used, the eigenfunction of Expression (3) is

[0028]

(Equation 7) It can be expressed as. here,

[0029]

(Equation 8)

Is a wave vector in the first Brillouin zone, and n is an integer specifying a band. Wave vector

(Equation 9) The condition of Bragg reflection for causing a wave having the following to be diffracted is represented by Expression (7).

[0031]

(Equation 10)

Wave vector

[Equation 11] Is

(Equation 12)

## EQU1 ## Here, considering the three-dimensional periodic structure in the same way as a crystal, the vector

(Equation 13) Is the reciprocal lattice vector. When Bragg reflection occurs one after another, the wave becomes a standing wave in which the wave does not travel in any direction, and this standing wave is composed of the following two traveling waves.

[0034]

[Equation 14]

The combination can be considered. If this traveling wave is present in a periodic structure consisting of three-dimensionally different dielectric constants of dielectric materials, its potential energy is different, and a cutoff frequency band corresponding to the band gap of the crystal, which inhibits the propagation of electromagnetic waves, is created. become.

Returning to FIGS. 1 and 2, the low dielectric material portion 11 includes a polymer material having a characteristic of a low relative dielectric constant, a composite material of a polymer material and a ceramic material, and a A composite material or the like is used. In order to form a broadband cut-off frequency band, the larger the ratio of the relative permittivity of the low-permittivity material portion 11 to the relative permittivity of the high-permittivity material portion 12 is, the more advantageous the relative permittivity is. Moderate. Although it is not impossible to use air having a relative dielectric constant of 1.0 as the low-dielectric-constant material portion 11, in consideration of product reliability and strength,
Low dielectric constant polymer materials are mainly used.

For example, a polymer material obtained by polymerizing a monomer composition containing a fumaric acid diester disclosed in JP-A-9-208627 or a homopolypropylene disclosed in JP-A-11-60645 Polymer obtained by graft-polymerization of styrene and (styrene / divinylbenzene) polymer, vinylbenzyl resin disclosed in JP-A-9-31006, polytetrafluoroethylene (P
TFE) resin, polyethylene (PE) resin, polystyrene (PS) resin, polycarbonate (PC) resin, polymethyl methacrylate (PMMA) resin, epoxy resin, polyimide resin, vinyl triazine (BT resin)
Resins, polyphenylene ether (PPE) resins, polyphenylene oxide (PPO) resins, polyolefin resins, vinyl chloride resins, unsaturated polyester resins, thermoplastic resins such as fluororesins, etc. are preferably used due to their low dielectric constant and low dielectric loss. .

For the high dielectric constant material portion 12, a polymer material having a high relative dielectric constant, a composite material of a polymer material and a ceramic material, a composite material of polymer materials, a ceramic material, or the like is used. . As described above, in order to form a broad cut-off frequency band, the higher the relative permittivity of the high-permittivity material portion 12, the better. For example, high dielectric constant polymer materials such as polyvinylidene fluoride resin, melamine resin, urea resin, and polyvinyl fluoride resin are preferably used. further,
When a material having a high relative dielectric constant is required, it is desirable to use a composite material of various polymer materials and a ceramic material as described above, or a ceramic material alone.

As a ceramic material, Japanese Patent Application No. 11-7 / 1999
BaO-Nd proposed in No. 0005_TwoO_Three-TiO_Two−
B_TwoO_Three-ZnO_Two-CuO-based materials and Al_TwoO_Three-TiO_Twosystem
Material, TiO_TwoSystem material, BaO-Bi_TwoO_Three-Nd_TwoO_Three−
TiO_TwoSystem material, BaO-Bi _TwoO_Three-Nd_TwoO_Three-TiO_Two
-SrTiO_ThreeSystem material, BaO-PbO-Nd_TwoO_Three-T
iO_TwoMaterial, BaNd_TwoTi_FiveO₁₄System material, BaSm_TwoT
i_FiveO₁₄Based material, Ba (Zn, Nb) O_ThreeSystem material, BaT
i_FourO₉System material, Ba_TwoTi₉O₂₀Material, (Zr, Sn)
TiO_FourMaterial, Ba (Zn, Ta) O_ThreeSystem material, Ba
(Mg, Ta) O _ThreeSystem material, MgTiO_Three-CaTiO_Three
Materials are particularly preferred due to their high dielectric constant and low dielectric loss.
New

Since the waveguide region 13 is a portion other than the periodic structure, it does not have a predetermined cutoff frequency band. Therefore, any material such as a polymer material, a composite material of a polymer material and a ceramic material, a composite material of polymer materials, and the like may be used for the waveguide region 13. Preferably, a material having low dielectric loss characteristics at the propagation frequency of the transmission line is advantageous because of the region that is responsible for the propagation of electromagnetic waves. Considering that the waveguide region 13 is manufactured at a low cost, it is desirable to use the material of the low dielectric constant material portion 11 or the high dielectric constant material portion 12 for the waveguide region 13 in an overlapping manner.

For the purpose of controlling the coefficient of thermal expansion and increasing the strength, the low-dielectric-constant material portion 11, the high-dielectric-constant material portion 12, and / or the waveguide region 13 are made of glass fiber. Or other reinforcing fibers.

In order to keep a predetermined cutoff frequency band stable,
In addition, in order to eliminate the temperature dependence of the transmission characteristics, it is preferable that the relative dielectric constant temperature coefficient of the low dielectric constant material portion 11, the high dielectric constant material portion 12, and the waveguide region 13 be close to zero. In this case, it is possible to provide a transmission line that can guarantee stable frequency-temperature characteristics over a wide temperature range. However, even if the low dielectric constant material portion 11, the high dielectric constant material portion 12, and the waveguide region 13 have poor temperature stability, this does not apply when a mechanism for compensating for the temperature drift is provided outside.

In the transmission line 1 having the three-dimensional periodic structure having a predetermined cut-off frequency band manufactured by the above-described configuration, the transmission line 1 is formed from the periodic structure of the low dielectric constant material portion 11 and the high dielectric constant material portion 12. When a frequency within a predetermined cut-off frequency band propagates, electromagnetic wave penetration into the periodic structure is prohibited, so that all electromagnetic waves concentrate on the waveguide region 13,
The light propagates along the waveguide region 13. Therefore, a low-loss transmission line in which no radiation loss occurs except for the transmission line is obtained. Further, since the waveguide region 13 can be formed in a closed structure not in contact with the outside, there is no influence of external noise.

In addition, according to the structure of the present embodiment, since the metal electrode portion which is indispensable in the conventional transmission line is not used, the metal loss does not contribute to the loss of the transmission line, and high efficiency transmission is possible. Become. Furthermore, since the metal electrode portion is not contained, there is an advantage that no gap, crack, or peeling occurs between the metal electrode and the dielectric. These features make it possible to supply device products stably and with good reproducibility. In particular, the fact that there is no need to consider the adhesive strength between the polymer material and the metal electrode is a great advantage in terms of both properties and manufacturing.

In addition, as compared with the NRD line shown in FIG. 10, the transmission line 1 according to the present embodiment has fewer components and does not require an assembling process, so that a stable product can be manufactured at low cost and easily. It is a feature. Since the transmission line 1 according to the present embodiment is easily integrated, it can be applied to a resonator, an oscillator, a directional coupler, a branch path, a filter, a circuit board for IC, and the like, using the transmission line as a basic component. It is possible.

Further, since the transmission line is formed mainly of a polymer material having a small specific gravity, the weight can be reduced as compared with a transmission line made of a ceramic material or a semiconductor. Not including a metal part in the transmission line also helps to reduce the weight.

When the above-described periodic structure is formed by the low dielectric material portion 11 and the high dielectric material portion 12, a film forming process, a spin coating process, a flow coating process, a curtain coating process, a press molding process, a dipping process, Process, a printing process, a transfer process, an inkjet process, a bubble jet process, a photolithography process, an ultraviolet light curing process, a laser trimming process, an etching process, a manufacturing method having any process of a bonding process, or a combination thereof. use. Thus, there is an advantage that a very complicated and expensive manufacturing process such as a semiconductor process is not required. Furthermore, since the polymer material is molded using the above-described manufacturing process, it is a great feature that the polymer material can be flexibly formed into an arbitrary shape.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The transmission line 1 according to the present embodiment will be specifically described below using embodiments. [Embodiment 1] A transmission line 1 having a three-dimensional periodic structure having a predetermined cutoff frequency band according to Embodiment 1 has the structure shown in FIGS. 1 and 2 already described. For the low dielectric material portion 11, a polymer material obtained by polymerizing dicyclohexyl fumarate (di-cHF) having a relative dielectric constant of 2.4 is used. In the high dielectric constant material portion 12 and the waveguide region 13,
The ratio of 20 mass% negative-working photosensitive polyimide resin is the dielectric constant is 13.3 and the _{BaO-MgO-CoO-Nb 2} O 5 based material 80 wt% of the polymeric material - using a composite material according to the ceramic material. With a combination of these materials, a 5.5 times higher relative dielectric constant ratio can be realized in the periodic structure, so that a wide cut-off frequency band can be realized.

Next, a method of manufacturing the transmission line 1 according to the present embodiment will be described with reference to FIG. FIG. 3 (a) to (g)
Indicates a cross section of the substrate during the manufacturing process of the transmission line 1. FIG. 3H is a perspective view of the completed transmission line 1.
First high dielectric constant material 20% 12 negative-working photosensitive polyimide resin and _{BaO-MgO-CoO-Nb 2} O 5 based material 80 wt% of the polymeric material - a composite material solution was dissolved in toluene solvent by a ceramic material And the polymer material solution 12
Obtain a. The organic solvent is not particularly limited as long as it exhibits good solubility and does not affect the evaporation rate.
As shown in FIG. 3 (a), after coating the polymer material solution 12a on the substrate by spin coating, heat treatment is applied to remove the solvent, and to maintain the solvent resistance.

Next, as shown in FIG. 3B, dicyclohexyl fumarate (di-cHF) is formed in order to form a solution portion of the low dielectric constant material 11 in the same manner as described above.
Is formed on the coating film of the polymer material solution 12a by spin coating.

Next, as shown in FIG. 3C, only a region having a desired shape, such as a dot, is cured by ultraviolet light using a masking technique, and the uncured portion is removed with an organic solvent. Then, by performing a heat treatment, a patterned low dielectric material portion 11 is formed on the high dielectric material portion 12.

As shown in FIGS. 3 (d), (e), (f), and (g), the three-dimensional periodic structure (FIG. 3 (h) Reference) is made. However, a layer in which the waveguide structure 13 in which the periodic structure is broken is contained in the layer in the middle of repeating the process. Thereafter, by dividing into a desired shape and drying, a transmission line 1 having a three-dimensional periodic structure having a predetermined cutoff frequency band can be obtained.

In the present embodiment, since the waveguide region 13 is formed of a high dielectric constant composite material of a polymer material-ceramic material, the effect of shortening the wavelength of the propagation frequency is achieved in addition to the advantage of low transmission loss. Yes, it is possible to meet the demands of downsizing. Since the wavelength in the dielectric is inversely proportional to the square root of the dielectric constant, the size can be reduced to 1 / 3.6 (= 1 / √13.3) as compared with using a waveguide, and Teflon (registered trademark) is used. ) Can be reduced in size by 1 / 2.5 (√ (2.1 / 13.3)) as compared with an NRD line using ()).

[Embodiment 2] Transmission line 1 according to Embodiment 2
Is shown in FIG. FIG. 4 is a perspective view illustrating the transmission line 1 having a two-dimensional periodic structure having a predetermined cutoff frequency band according to the present embodiment. For the low dielectric constant material portion 11 and the waveguide region 13, a polymer material obtained by graft polymerization of homopolypropylene having a relative dielectric constant of 2.3 and a (styrene / divinylbenzene) polymer is used. In part 12,
BaO—Bi ₂ O ₃ —Nd ₂ O ₃ having a relative dielectric constant of 93.0
-Uses a TiO ₂ -based material.

The high-permittivity material portion 12 is processed into a columnar shape, is periodically arranged, and is embedded in the polymer material of the low-permittivity material portion 11. However, the columnar sample of the high dielectric constant material portion 12 is not arranged at the center, and the waveguide region 13 in which the periodic structure is broken is formed.

Next, a method of manufacturing the transmission line 1 according to this embodiment will be described with reference to FIG. 5 (a) to 5 (c)
FIG. 3 is a perspective view showing a substrate during a manufacturing process of the transmission line 1.
First, as shown in FIG. 5A, a polymer material obtained by graft-polymerizing a homopolypropylene and a (styrene / divinylbenzene) polymer, which is a low dielectric constant material portion 11, is hot-pressed on a film to form a sheet. 11a is obtained.

Next, as shown in FIG. 5 (b), the BaO-Bi ₂
O ₃ -Nd ₂ O ₃ as -TiO ₂ based material forms a two-dimensional periodic structure, using the mounter device, arranged in mechanical.

Thereafter, as shown in FIG. 5 (c), the polymer material of the low dielectric material portion 11 is poured into the empty space on the sheet so as to fill the high dielectric material portion 12, and hot pressing is performed again. However, the high dielectric constant material portion 12
By not disposing the columnar sample, the waveguide region 13 in which the periodic structure is broken can be formed. Thereafter, by dividing the transmission line 1 into a desired shape, the transmission line 1 having a two-dimensional periodic structure having a predetermined cutoff frequency band can be obtained.

In this embodiment, since the waveguide region 13 is formed of the low dielectric constant material 11, there is an effect that the propagation speed is increased in addition to the advantage of the low transmission loss, and the high speed communication is supported. Can be. Since the propagation velocity (phase velocity) in a dielectric medium is inversely proportional to the square root of the relative permittivity, Al ₂
Compared to using an O ₃ substrate, 2 (√ (9.5 / 2.
3)) The speed can be increased by a factor of 4.1, and the speed can be increased by 4.1 (／(38.8/2.3)) times as compared with using a Ba ₂ Ti ₉ O ₂₀ substrate.

Third Embodiment In the third embodiment, the function of a cutoff frequency band in a transmission line 1 having a three-dimensional periodic structure having a predetermined cutoff frequency band will be clarified by an electromagnetic field calculation method. Three-dimensional periodic structure model 2 of the third embodiment
Has a structure shown in FIG. 6, and uses a material having a relative dielectric constant of 2.4 for the low dielectric constant portion 11 and a material having a relative dielectric constant of 12.0 for the high dielectric constant portion 12. I have. In FIG. 6, the period of the periodic structure, that is, the center interval between the high-permittivity portions 12 dots is set to 5.81 mm, and the radius of the high-permittivity portions 12 dots is set to 1.04 mm (occupancy rate 0.1). For the electromagnetic field calculation method, a time domain difference method (FD-TD), which has high calculation accuracy and shortens the calculation time, was used. FIG. 7 shows the result of the simulation using the above model structure. As a result, a cutoff frequency band having a wide band and large attenuation was confirmed. Therefore, in the transmission line 1 having the three-dimensional periodic structure,
It can be seen that a sufficiently practical cut-off frequency band is provided.

The present invention is not limited to the above embodiment, but can be variously modified. For example, as shown in FIG. 8, a three-dimensional periodic structure can be realized by providing the high dielectric constant material portion 12 in a wave shape. Further, as shown in FIG. 9, the propagation direction of the electromagnetic wave can be arbitrarily changed by bending the waveguide region 13 into a U-shape or an L-shape.

[0062]

As described above, according to the present invention, there is provided a transmission line having a two-dimensional or three-dimensional periodic structure having a predetermined cut-off frequency band, which is suitable for exhibiting low-loss transmission characteristics. Can be. Further, as a further effect of the present invention, a transmission line having a two-dimensional or three-dimensional periodic structure having a predetermined cutoff frequency band suitable for exhibiting low loss characteristics can be manufactured with good reproducibility and at low cost. Thus, it is possible to provide a transmission line having a lightweight two-dimensional or three-dimensional periodic structure having a flexible shape.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a transmission line having a three-dimensional periodic structure having a predetermined cutoff frequency band according to an embodiment of the present invention;
FIG.

FIG. 2 is a first embodiment of a transmission line having a three-dimensional periodic structure having a predetermined cutoff frequency band according to one embodiment of the present invention;
FIG.

FIG. 3 is a first embodiment of a transmission line having a three-dimensional periodic structure having a predetermined cutoff frequency band according to one embodiment of the present invention;
It is the schematic which shows the manufacturing method of.

FIG. 4 is a second embodiment of a transmission line having a two-dimensional periodic structure having a predetermined cutoff frequency band according to one embodiment of the present invention;
FIG.

FIG. 5 is a second embodiment of a transmission line having a two-dimensional periodic structure having a predetermined cut-off frequency band according to one embodiment of the present invention;
It is a perspective view which shows the manufacturing method of.

FIG. 6 is a perspective view of Embodiment 3 of a three-dimensional periodic structure model having a predetermined cutoff frequency band according to an embodiment of the present invention.

FIG. 7 is a transmission characteristic diagram of Example 3 of a three-dimensional periodic structure model having a predetermined cutoff frequency band according to an embodiment of the present invention.

FIG. 8 is a perspective view showing a modification of a transmission line having a three-dimensional periodic structure having a predetermined cut-off frequency band according to an embodiment of the present invention.

FIG. 9 is a perspective view showing another modified example of a transmission line having a three-dimensional periodic structure having a predetermined cut-off frequency band according to an embodiment of the present invention.

FIG. 10 is a perspective view showing a conventional NRD line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission line 2 Three-dimensional periodic structure model 11 Low dielectric constant material part 12 High dielectric constant material part 13 Waveguide area 81 Metal plate 82 Dielectric strip

Claims (8)

[Claims] A first dielectric having a first relative dielectric constant; a second dielectric having a second relative dielectric constant different from the first dielectric constant; and the first and second dielectrics. A predetermined structure defined based on the first and second dielectric constants and the period so as to forbid propagation of a predetermined electromagnetic wave in a high frequency band. A transmission line comprising a frequency band. 2. The transmission line according to claim 1, wherein the periodic structure is a three-dimensional periodic structure in which the first and second dielectrics are three-dimensionally arranged at a predetermined period. Transmission line. 3. The transmission line according to claim 1, wherein the first dielectric is made of a dielectric material including at least one of a polymer material and a ceramic material. Transmission line. 4. The transmission line according to claim 3, wherein the second dielectric is formed of a dielectric material including a polymer material. 5. The transmission line according to claim 4, wherein the dielectric material of the second dielectric includes a ceramic material. 6. The transmission line according to claim 4, wherein the dielectric material of the second dielectric is a composite material containing two or more polymer materials. 7. The transmission line according to claim 4, wherein the dielectric material of the first and second dielectrics has a laminated structure. . 8. The transmission line according to claim 1, wherein the transmission line includes a transmission region in which the periodic structure is not formed.