Dielectric waveguides, wireless antennas

Abstract

To provide a dielectric waveguide with small propagation loss.SOLUTION: A dielectric waveguide 100 is formed of a dielectric, and a cavity 112 extending in the longitudinal direction of the dielectric waveguide 100 is present inside the dielectric waveguide 100. Preferably, the number of cavities 112 is one in a cross section perpendicular to the longitudinal direction of the dielectric waveguide 100 at a portion of the dielectric waveguide 100 where cavities 112 are located. Also, in this cross section, it is preferable that the center of the dielectric waveguide 100 coincides with the center of the cavity 112.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a dielectric waveguide suitable for the propagation of electromagnetic waves having frequencies in the millimeter wave band (30 GHz to 300 GHz) or the quasi-millimeter wave band (although there is no clear definition, approximately 20 GHz to 30 GHz), and a wireless antenna including the dielectric waveguide.

Background Art

[0002] In the fifth-generation mobile communication system (so-called 5G), electromagnetic waves having high frequencies in the quasi-millimeter wave band or the millimeter wave band are used to improve the data rate of wireless communication. Such electromagnetic waves having high frequencies have the characteristic that the diffraction loss due to obstacles is large (in other words, the directivity of the electromagnetic waves is high) compared with electromagnetic waves having lower frequencies (for example, 700 MHz, 2 GHz) that have been used in the fourth-generation mobile communication system (so-called 4G). Therefore, a technique for reducing dead zones (that is, regions where electromagnetic waves do not reach) is required.

[0003] Patent Document 1 discloses, as one of the techniques for reducing dead zones, a wireless antenna including a dielectric waveguide that is a wired transmission medium and a dielectric attachment that can be installed at any location of the dielectric waveguide. According to the wireless antenna of Patent Document 1, a dielectric waveguide is laid from a wireless base station, and a dielectric attachment is installed at a portion of the dielectric waveguide located near a region that would be a dead zone if the wireless antenna were not used. As a result, the dielectric attachment radiates electromagnetic waves, thereby realizing the reduction of the dead zone. According to the wireless antenna of Patent Document 1, since active components such as a repeater are not used and a dielectric attachment (that is, a radiation source of electromagnetic waves) can be formed at any location of the dielectric waveguide, coverage according to the situation can be formed with low power consumption. For example, in high-frequency communication, coverage can be efficiently formed inside a factory or a room where people or equipment exist as obstacles.

[0004] When a dielectric waveguide exists in the communication path between a communication terminal and a radio base station within a coverage area, in order to ensure a good signal-to-noise ratio (hereinafter referred to as "SN ratio"), it is desirable to minimize the propagation loss of the dielectric waveguide as much as possible. The loss of the dielectric waveguide is determined by the dielectric loss inherent in the dielectric material. Therefore, as a method for realizing a low-loss dielectric waveguide, the use of a dielectric with a low dielectric loss is considered. However, even polytetrafluoroethylene (PTFE), which is generally known as a dielectric material with a low dielectric loss, has a dielectric tangent of about 0.001. Even when a dielectric material with a low dielectric loss is used, non-negligible propagation loss occurs in a long dielectric waveguide.

[0005] If the radiated power of electromagnetic waves into space due to installing a dielectric attachment on the dielectric waveguide (this means disturbing the permittivity distribution of the dielectric waveguide) is large, the average received power of the communication terminals arranged within the coverage area will improve, and the SN ratio of the communication will also improve. In a dielectric waveguide, many components of the propagation mode are confined inside the dielectric waveguide, and a slight mode component (i.e., an evanescent component) that leaks out to the outside of the dielectric waveguide (for example, the cladding which is air) senses the disturbance of the permittivity distribution given to the dielectric waveguide from the outside, resulting in electromagnetic wave radiation into space. However, according to the prior art dielectric waveguide, since the energy ratio of the evanescent component in the propagation mode is low, the radiated power of the electromagnetic waves generated by installing a dielectric attachment on the dielectric waveguide is not necessarily large.

[0006] Furthermore, since the relative permittivity of the dielectric has temperature dependence, the propagation characteristics of the dielectric waveguide change due to changes in the external temperature. When the relative permittivity decreases due to a temperature change, the cutoff frequency of the propagation mode in the dielectric waveguide changes. The change in the cutoff frequency can cause a significant degradation in the quality of wireless communication. Generally, a dielectric waveguide has high-pass characteristics similar to a metal waveguide and has a low-frequency cutoff frequency. However, when the relative permittivity of the dielectric decreases due to a temperature change, the low-frequency cutoff frequency increases. That is, a signal that was propagating through the dielectric waveguide before the temperature change can no longer propagate through the dielectric waveguide due to the temperature change, and the signal-to-noise ratio decreases significantly.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] As described above, the prior art dielectric waveguide has the following three problems. (1) The propagation loss of the dielectric waveguide due to dielectric loss inherent in the dielectric material is large. (2) The radiated power from the dielectric attachment installed on the dielectric waveguide is small. (3) The propagation characteristics of the dielectric waveguide are easily affected by changes in the outside air temperature.

[0009] An object of the present invention is to provide a dielectric waveguide that simultaneously solves these three problems and a wireless antenna including the dielectric waveguide.

Means for Solving the Problems

[0010] The technical matters described herein are not for explicitly or implicitly limiting the invention described in the claims of the patent, nor are they an indication of tolerating such limitations by persons other than those who benefit from the present invention (for example, the applicant and the patentee), but are merely described for facilitating the understanding of the gist of the present invention. The outline of the present invention from other viewpoints can be understood, for example, from the claims of this patent application at the time of filing. The dielectric waveguide of the present invention is formed of a dielectric, and there is a cavity extending in the longitudinal direction of the dielectric waveguide inside the dielectric waveguide. The wireless antenna of the present invention includes the above-described dielectric waveguide and dielectric attachment.

Advantages of the Invention

[0011] According to the present invention, since the main component of the propagation mode exists in the cavity of the dielectric waveguide as the transmission medium, the influence of dielectric loss can be reduced, and high-frequency transmission with low loss can be realized as compared with the dielectric waveguides of the prior art. Further, according to the present invention, since many evanescent waves leak to the outside of the dielectric waveguide as compared with the dielectric waveguides of the prior art, the power radiated from the dielectric attachment provided on the dielectric waveguide can be increased. Furthermore, according to the present invention, since the energy of the propagation mode mainly exists in the gas in the cavity (the temperature change of the relative dielectric constant of the gas is usually smaller than that of the dielectric), the temperature dependence of the propagation characteristics is smaller as compared with the dielectric waveguides of the prior art.

Brief Description of the Drawings

[0012]

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Best Mode for Carrying Out the Invention

[0013] To explain the principle of the present invention, first, the propagation of electromagnetic waves by a prior-art dielectric waveguide 900 will be described. FIG. 1(a) shows a cross-sectional view of the prior-art dielectric waveguide 900. As shown in FIG. 1(a), the prior-art dielectric waveguide 900 includes a core 910 and a cladding 920. Each of the core 910 and the cladding 920 is made of a uniform dielectric. The core 910 is a solid object having an elongated rectangular parallelepiped shape. The cladding 920 is not necessarily a solid object. For example, when air functions as the cladding 920, the dielectric waveguide 900 does not have a cladding 920 as a solid object (see FIG. 1(b)). The relative permittivity of the dielectric material of the core 910 is greater than the relative permittivity of the dielectric material of the cladding 920. By appropriately designing the difference between the relative permittivity of the core 910 and the relative permittivity of the cladding 920, it is possible to generate the attitude (so-called propagation mode) of an electromagnetic wave that propagates in the direction perpendicular to the plane of FIG. 1 (i.e., the longitudinal direction of the dielectric waveguide 900) while being confined in the vicinity of the core 910. With this propagation mode, information transmission using the dielectric waveguide can be performed.

[0014] The electric field intensity distribution of the propagation mode (here, the fundamental mode that is most likely to propagate) of the dielectric waveguide 900 when the cladding 920 is air is shown in FIG. 2. In the propagation mode of the dielectric waveguide 900, although there is a certain degree of penetration (called an evanescent wave) of the electric field intensity distribution outside the core 910, most of it is confined within the core 910. Therefore, the propagation loss of the propagation mode is mainly determined by the dielectric loss of the dielectric material of the core 910. In particular, when air is the cladding 920, since the dielectric loss of air is almost 0, the dielectric loss of the core 910 directly causes the propagation loss of the dielectric waveguide 900.

[0015] The present invention is characterized in that, in order to reduce the dielectric loss of the core, the main part that confines the propagation mode is a gas (usually air) with substantially no dielectric loss. First, the outline of the dielectric waveguide 100 of the embodiment will be described, and its details will be described later. The cross section of the dielectric waveguide 100 is shown in FIG. 3. In this example, inside the dielectric waveguide 100, there is one cavity 112 extending in the longitudinal direction of the dielectric waveguide 100 (that is, the propagation direction of the electromagnetic wave). As described above, in a dielectric waveguide, an electromagnetic field is confined in a region with a high relative permittivity and its vicinity. Therefore, if the ratio of the cavity 112 in the cross section of the dielectric waveguide 100 is too large, the electromagnetic wave cannot be confined in the dielectric waveguide 100 including the cavity 112, and there is no propagation mode (this is called cutoff). However, when the size of the cavity 112 is small to a certain extent, a propagation mode having an electric field strength distribution as shown in FIG. 7 can be formed.

[0016] The reason for the existence of such a propagation mode can be qualitatively explained as follows. In Fig. 7, consider the dielectric walls 100a located at both ends in the width direction of the cavity 112 (in this example, the x-axis direction in Fig. 7). Assume that the width (the length in the x-axis direction) of the dielectric wall 100a is determined such that it cannot maintain a propagation mode when it exists alone in air. In this case, even if an electromagnetic wave enters a single dielectric wall 100a isolated in air, since the propagation mode is in a cutoff state, the electromagnetic wave will eventually be radiated into the air. When the electromagnetic wave is radiated, since the relative permittivity of the dielectric wall 100a is larger than that of air, the electric field intensity distribution takes a form in which the evanescent wave is gradually radiated into the air while maintaining a mountain-shaped shape with the maximum value of the electric field intensity at the center of the dielectric wall 100a (a shape obtained by compressing the electric field intensity distribution shown in Fig. 2 in the x-axis direction). In the dielectric waveguide 100 of the embodiment, two dielectric walls 100a are located at both ends in the x-axis direction of the cavity 112. When two dielectric walls 100a exist, by setting the distance between the dielectric walls 100a (that is, the width of the cavity 112) to be narrow to some extent, as shown in Fig. 7, the evanescent wave component of the electromagnetic wave radiated from one dielectric wall 100a penetrates into the other dielectric wall 100a, reflects at the interface between the other dielectric wall 100a and air, and overlaps with the electric field intensity distribution of one dielectric wall 100a to reinforce each other. That is, in this case, the two dielectric walls 100a equivalently form a dielectric waveguide having a width thicker than that of a single dielectric wall 100a, and the propagation mode can be maintained. Therefore, in the dielectric waveguide 100, as shown in Fig. 3, the annular structure of the dielectric surrounding the cavity 112 in the circumferential direction of the dielectric waveguide 100 equivalently functions as a core.

[0017] In this case, the propagation mode formed is such that, as shown in FIG. 7, most of the energy of the propagation mode exists in the cavity 112. Therefore, in the propagation mode of the dielectric waveguide 100, the influence of the dielectric loss of the dielectric constituting the dielectric wall 100a is relatively reduced. As a result, the propagation loss of the dielectric waveguide 100 is smaller than that of the prior art dielectric waveguide 900. Also, since the electromagnetic wave mainly propagates through the cavity 112, the equivalent relative permittivity of the dielectric waveguide 100 is smaller than that of the prior art dielectric waveguide 900, specifically taking a value close to air (a value close to 1). Therefore, in the dielectric waveguide 100 of the embodiment, the confinement of the electric field strength distribution to the equivalent core including the cavity 112 is weaker than that of the prior art dielectric waveguide 900 (the equivalent relative permittivity of the dielectric waveguide 900 is close to the relative permittivity of the dielectric), and its propagation mode takes a form in which more evanescent waves penetrate into the air. Thus, according to the dielectric waveguide 100, the power of the electromagnetic wave radiated due to the perturbation of the relative permittivity applied from the outside increases more than that in the prior art dielectric waveguide 900. Furthermore, according to the dielectric waveguide 100, since most of the energy of the propagation mode exists in the air where the temperature change of the relative permittivity is smaller than that of the dielectric, the variation in the propagation characteristics due to the change in the relative permittivity of the dielectric caused by the temperature change is smaller than that in the prior art dielectric waveguide.

[0018] Note that when actually designing the dielectric waveguide 100, by using electromagnetic field analysis or the finite element method with the sizes of the core, cavity, and cladding and their relative permittivities as variables in the cross-sectional shape, it is possible to easily confirm whether a propagation mode exists.

[0019] <Embodiment> Embodiments of the present invention will be described with reference to the drawings. The wireless antenna 200 of the embodiment includes a dielectric waveguide 100 of the embodiment and a dielectric attachment 130 (see FIG. 3). In this embodiment, one end of the dielectric waveguide 100 is connected to a signal device (not shown. Specifically, it is a signal generation device, a reception device, or a transmission / reception device) that generates a signal having a frequency of millimeter wave (30 GHz to 300 GHz) or quasi-millimeter wave (no clear definition, but approximately 20 GHz to 30 GHz). There is no limitation on the type of this signal, and it may be an analog signal, a digital signal, a discrete-time signal, or a continuous-time signal. The other end of the dielectric waveguide 100 may be open without being connected to anything, may be short-circuited, may be connected to an antenna (for example, a linear antenna, an aperture antenna, etc.), or may be terminated.

[0020] The dielectric waveguide 100 of the embodiment is a physical object formed of a dielectric, and as shown in FIG. 3, has an external shape in which the length is significantly larger than the width, like a cable, for example. The dielectric waveguide 100 may have a linear shape, or may have a shape that meanders slightly, in other words, a shape having a bend to such an extent that it does not adversely affect the low-loss propagation of the dielectric waveguide 100. The dielectric waveguide 100 has a uniform structure in which the shape, size, and material are constant at any position.

[0021] As shown in FIG. 3, the dielectric waveguide 100 has a structure that is a tube itself or has a structure including a tube. Inside the dielectric waveguide 100, there are N cavities 112 (that is, spaces filled with gas) extending in the longitudinal direction of the dielectric waveguide 100 (that is, the direction in which electromagnetic waves will propagate). N is an integer satisfying N≧1. A "tube" is an elongated hollow structure in which a cavity extending without interruption in its longitudinal direction exists inside, and at least at one end thereof, the cavity communicates with the outside. From the viewpoint of ease of manufacturing, the N cavities 112 extend linearly and preferably extend parallel to each other.

[0022] When the dielectric waveguide 100 has a structure that is the tube itself, the dielectric waveguide 100 has an elongated hollow structure including N cavities 112, and each of the N cavities 112 extends without interruption in the longitudinal direction of the dielectric waveguide 100 inside the dielectric waveguide 100, and communicates with the outside of the dielectric waveguide 100 (usually air which is the outside air) at one or both ends of the dielectric waveguide 100. From the viewpoint of low-loss propagation of electromagnetic waves, preferably, the N cavities 112 extend from one end to the other end or near the other end of the dielectric waveguide 100. FIG. 3 shows an example of the structure of the dielectric waveguide 100 which is the tube itself (however, N = 1). Each cavity 112 is filled with the outside air, that is, air.

[0023] When the dielectric waveguide 100 has a structure including a tube, the dielectric waveguide 100 has a structure including, for example, an elongated hollow tube including N cavities 112 and covers 117 closing both ends of this tube, and each of the N cavities 112 extends without interruption in the longitudinal direction of the dielectric waveguide 100 inside the dielectric waveguide 100, and does not communicate with the outside of the dielectric waveguide 100 (usually air which is the outside air) at both ends of the dielectric waveguide 100. From the viewpoint of low-loss propagation of electromagnetic waves, preferably, the dielectric waveguide 100 extends from near one end to near the other end. Usually, each cavity 112 is filled with air, but at least one of the N cavities 112 may be filled with a gas having a relative permittivity smaller than that of air (for example, helium). When it is required to avoid deformation of the dielectric waveguide 100 due to the difference between the pressure of the gas in each cavity 112 and the outside air pressure (for example, when the dielectric waveguide 100 is used at a location with an air pressure different from the air pressure at its manufacturing location), a through hole 115 communicating the outside of the dielectric waveguide 100 with at least one cavity 112 may be formed. The through hole 115 has a size (specifically, diameter) sufficiently small with respect to the wavelength of the electromagnetic wave. By the through hole 115, the difference between the pressure in the cavity 112 and the outside air pressure can be eliminated without degrading the propagation characteristics of the dielectric waveguide 100. FIG. 4 shows an example of the structure of the dielectric waveguide 100 including a tube (however, N = 1).

[0024] When N ≥ 2, two different cavities 112 do not communicate with each other inside the dielectric waveguide 100. Further, when N ≥ 1, in any cross-section of the dielectric waveguide 100 perpendicular to the longitudinal direction of the dielectric waveguide 100 at the position of the part of the dielectric waveguide 100 where at least one cavity 112 is located, preferably N cavities 112 are present, and each cavity 112 does not communicate with the external space of the dielectric waveguide 100. In other words, in this cross-section, each cavity 112 is surrounded by the dielectric material forming the dielectric waveguide 100.

[0025] When N ≥ 2, in the cross-section of the dielectric waveguide 100 perpendicular to the longitudinal direction of the dielectric waveguide 100, the arrangement of the N cavities 112 preferably has line symmetry or rotational symmetry. An example of the cross-section of the dielectric waveguide 100 perpendicular to the longitudinal direction of the dielectric waveguide 100 in the case of N = 4 is shown in FIG. 5.

[0026] In any cross-section of the dielectric waveguide 100 perpendicular to the longitudinal direction of the dielectric waveguide 100 at the position of the part of the dielectric waveguide 100 where the cavity 112 is located, the outer peripheral shape of the dielectric waveguide 100 may be any of, for example, a square, a rectangle, a circle, and an ellipse, and the shape of the cavity 112 may be any of, for example, a square, a rectangle, a circle, and an ellipse. The outer peripheral shape of the dielectric waveguide 100 does not have to match the shape of the cavity 112. For example, a configuration in which the outer peripheral shape of the dielectric waveguide 100 is a rectangle and the shape of the cavity 112 is a circle is also acceptable.

[0027] From the viewpoints of ease of manufacturing or ease of electromagnetic field analysis, preferably N = 1. In this case, it is preferable that the center of the dielectric waveguide 100 coincides with the center of the cavity 112. In the cross-section of the dielectric waveguide 100 perpendicular to the longitudinal direction of the dielectric waveguide 100 at any position of the part of the dielectric waveguide 100 where the cavity 112 is located, when the outer peripheral shape of the dielectric waveguide 100 is square or rectangular, its center is the intersection of the diagonals; when it is circular, its center is the center of the circle; when it is elliptical, its center is the intersection of the major axis and the minor axis. Similarly, when the inner peripheral shape of the dielectric waveguide 100, that is, the shape of the cavity 112, is square or rectangular, its center is the intersection of the diagonals; when it is circular, its center is the center of the circle; when it is elliptical, its center is the intersection of the major axis and the minor axis.

[0028] From the viewpoint of long-distance transmission, in the frequency band of the electromagnetic wave propagating through the dielectric waveguide 100, the number of propagation modes of this electromagnetic wave is preferably 1 in at least one of the vertically polarized wave and the horizontally polarized wave. That is, it is desirable that the dielectric waveguide 100 satisfies the single-mode condition.

[0029] The relative permittivity of the dielectric waveguide 100 is larger than the relative permittivity around the dielectric waveguide 100. In the example shown in FIG. 3, the surroundings of the dielectric waveguide 100 are air, and the permittivity of air is approximately 1, so the permittivity of the dielectric waveguide 100 is larger than 1. For this reason, when there is no dielectric attachment 130, the electromagnetic wave entering from one end of the dielectric waveguide 100 concentrates on the dielectric waveguide 100 with a large relative permittivity and is transmitted with low loss toward the other end of the dielectric waveguide 100 and reaches the other end of the dielectric waveguide 100.

[0030] In the above example, it can be understood that the dielectric waveguide 100 is the core and air is the cladding. The cladding is not limited to air and may be a solid object formed of a dielectric. That is, a cover 110 formed of a dielectric may be disposed on the outer periphery of the dielectric waveguide 100 (see FIG. 6 which is a cross-sectional view perpendicular to the longitudinal direction of the dielectric waveguide 100). The cover 110 is in close contact with the dielectric waveguide 100. The relative permittivity of the dielectric waveguide 100 is greater than the relative permittivity of the cover 110. Therefore, the electromagnetic wave that enters from one end of the dielectric waveguide 100 concentrates on the dielectric waveguide 100 having a large relative permittivity and is transmitted with low loss toward the other end of the dielectric waveguide 100 in the case where there is no dielectric attachment, and reaches the other end of the dielectric waveguide 100.

[0031] The dielectric attachment 130 provided on the dielectric waveguide 100 functions as a radiation part or a reception part of an electromagnetic wave (see the above Patent Document 1). The dielectric attachment 130 is formed of a dielectric. The shape of the dielectric attachment 130 is not limited at all, and for example, it may be a polygonal prism, a cylinder, a sphere, or a part of any of them, or a laundry clip.

[0032] In an example where the dielectric attachment 130 is positioned on the dielectric waveguide 100, the dielectric attachment 130 may be formed integrally with the dielectric waveguide 100 or may be formed separately from the dielectric waveguide 100. In the latter case, the dielectric attachment 130 is attached to the dielectric waveguide 100, but thereafter, it may not be removable from the dielectric waveguide 100 or may be removable from the dielectric waveguide 100. Even when the dielectric attachment 130 is removable from the dielectric waveguide 100, once the dielectric attachment 130 is attached to the dielectric waveguide 100, it is desirable that the dielectric attachment 130 does not move on the dielectric waveguide 100. The dielectric attachment 130 is in close contact with the dielectric waveguide 100. For this reason, when attaching the dielectric attachment 130 to the dielectric waveguide 100, the dielectric attachment 130 has a contact surface having the same surface shape as the local surface shape of the portion of the dielectric waveguide 100 to which the dielectric attachment 130 is attached. For example, if the dielectric waveguide 100 is an elongated rectangular parallelepiped, the contact surface of the dielectric attachment 130 is composed of at least one plane, and if the dielectric waveguide 100 is an elongated cylinder, the contact surface of the dielectric attachment 130 is a part of the cylindrical surface. When using an adhesive or an adhesive to bring the dielectric attachment 130 into close contact with the dielectric waveguide 100, it is desirable that the relative permittivity of the adhesive or the adhesive is about the same as the relative permittivity of the dielectric waveguide 100 or about the same as the relative permittivity of the dielectric attachment 130.

[0033] In an example where the dielectric attachment 130 is located in the vicinity of the dielectric waveguide 100 away from the dielectric waveguide 100, the upper limit of the distance between the dielectric attachment 130 and the dielectric waveguide 100 is determined by the relative permittivity of the dielectric attachment 130, the relative permittivity of the dielectric waveguide 100, the relative permittivity of the medium (examples of the medium include air or foamed plastic) between the dielectric attachment 130 and the dielectric waveguide 100, the intensity of the signal propagating through the dielectric waveguide 100, the shape of the cross-section of the dielectric waveguide 100, the size of the cross-section of the dielectric waveguide 100, and the like. However, here, the "distance between the dielectric attachment 130 and the dielectric waveguide 100" refers to the shortest of the distances between any point on the dielectric attachment 130 and any point on the dielectric waveguide 100. If the distance between the dielectric attachment 130 and the dielectric waveguide 100 is equal to or less than the above upper limit, the dielectric attachment 130 functions as a radiation part or a receiving part. In other words, the "vicinity of the waveguide" where the block is located is the range in which the dielectric attachment 130 can function as a radiation part or a receiving part.

[0034] The positional relationship between the dielectric attachment 130 and the dielectric waveguide 100 may be a permanent relationship or a temporary relationship. In the case of a permanent relationship, for example, as shown in FIG. 8(a), the dielectric attachment 130 is fixed to a mounting component 310 fixed to the dielectric waveguide 100. The material of the mounting component 310 may be a dielectric or a metal. However, it is desirable to avoid the presence of an electrical conductor (for example, when the material of the mounting component 310 is metal, a part or all of the mounting component 310) between the dielectric attachment 130 and the dielectric waveguide 100. The mounting component 310 serves as a holder for holding the dielectric attachment 130 and as a spacer for keeping the distance between the dielectric attachment 130 and the dielectric waveguide 100 constant.

[0035] In the case of a temporary relationship, as shown in FIG. 8(b) for example, the dielectric attachment 130 is fixed to the cylindrical slider 320, and this slider 320 is attached to the dielectric waveguide 100. The slider 320 can move along the dielectric waveguide 100. The material of the slider 320 may be a dielectric or a metal. However, also in this example, it is desirable to avoid the presence of an electrical conductor (for example, when the material of the slider 320 is metal, it is part or all of the slider 320) between the dielectric attachment 130 and the dielectric waveguide 100. The slider 320 serves as a holder for holding the dielectric attachment 130 and as a spacer for keeping the distance between the dielectric attachment 130 and the dielectric waveguide 100 constant.

[0036] As another example of a temporary relationship, an example can be given in which the dielectric attachment 130 is attached to a movable object (examples of the movable object include footwear, an object worn on the human body such as an anklet, or a transport robot), and all or part of the dielectric waveguide 100 is buried in a structure such as a floor or a passage. FIG. 8(c) shows an example in the case where the movable object is the transport robot 330. In this case, when the movable object moving on the structure approaches the dielectric waveguide 100, that is, when the dielectric attachment 130 attached to the movable object enters the range where the distance from the dielectric waveguide 100 is below the above upper limit, the dielectric attachment 130 functions as a radiation part or a reception part. When the movable object has a receiver or a transmitter (the movable object may have electronic components such as an amplifier as necessary), communication is realized between the signal device (not shown) and the receiver or transmitter of the movable object. According to the example in which the dielectric attachment 130 is attached to the movable object, electromagnetic wave radiation occurs only when the movable object approaches the dielectric waveguide 100, so the energy utilization efficiency is improved.

[0037] <First Embodiment> As a first embodiment, a dielectric waveguide 100 used in the 28 GHz band will be described. Fig. 9 shows the cross-sectional structures of a prior art dielectric waveguide 900 (comparative example) and the dielectric waveguide 100 of the first embodiment, both of which satisfy the single-mode condition. The dielectric is polytetrafluoroethylene, with a relative permittivity of 2.1 and a dielectric tangent of 0.001. The cavity 112 is located at the center of the dielectric waveguide 100.

[0038] Fig. 10 shows the calculation results of the propagation loss by electromagnetic field analysis. From Fig. 10, it can be seen that at 28 GHz, the propagation loss of the dielectric waveguide 100 is 1.65 dB / m, which is smaller than the propagation loss of 2.3 dB / m of the prior art dielectric waveguide 900. As described above, this is due to the fact that the propagation mode of the dielectric waveguide 100 mainly propagates through air with low dielectric loss. Therefore, the communication distance can be extended by using the dielectric waveguide 100.

[0039] Since the energy of the propagation mode of the dielectric waveguide 100 is mainly distributed in the air, the temperature dependence of the propagation characteristics is less sensitive compared to the prior art. Therefore, the dielectric waveguide 100 can withstand use in places with large temperature changes, such as around machines placed in a factory or around servers in a server room.

[0040] <Second Embodiment> As a second embodiment, an example in which a dielectric attachment 130 is installed on the dielectric waveguide 100 used in the 28 GHz band will be described. As an analysis model for reproducing the situation where the dielectric attachment 130 is installed on the dielectric waveguide 100, as shown in Fig. 11, a model is used in which a rectangular parallelepiped dielectric attachment 130 (polytetrafluoroethylene, relative permittivity 2.1, dielectric tangent 0.001) is arranged in contact with the wall surface of the dielectric waveguide 100. The size of the dielectric attachment 130 is 10 mm × 20 mm × 30 mm as shown in Fig. 11.

[0041] In the model shown in FIG. 11, the radiation efficiency (the ratio of the energy radiated into the air out of the energy propagating through the dielectric waveguide) when adopting the prior art dielectric waveguide 900 shown in FIG. 9(a) and when adopting the dielectric waveguide 100 shown in FIG. 9(b) as the dielectric waveguide was calculated and compared by electromagnetic field analysis. The calculation results are shown in FIG. 12. It can be seen from FIG. 12 that at 27 to 29 GHz, the radiation efficiency is improved by 15 to 35% by using the dielectric waveguide 100. By installing the dielectric attachment 130 on the dielectric waveguide 100, electromagnetic waves can be efficiently radiated into space, and thus the coverage area covered by one dielectric attachment 130 can be expanded.

[0042] The technical features disclosed in the above various embodiments are not necessarily mutually exclusive. As long as there is no contradiction from a technical perspective, the technical features of one embodiment may be applied to the technical features of other embodiments.

[0043] <Addendum> Although the present invention has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes can be made and its elements can be replaced with equivalents without departing from the scope of the present invention. Furthermore, many modifications can be added to adapt a particular system, device, or its components to the teachings of the present invention without departing from the essential scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed for carrying out the present invention, but includes all embodiments included in the appended claims.

[0044] Furthermore, the use of terms such as "first", "second", etc., if any, does not indicate order or importance, and terms such as "first", "second", etc. are used to distinguish elements. The terms used in this specification are for the purpose of describing embodiments and are in no way intended to limit the present invention. The term "comprising" and its inflected forms, when used in this specification and / or the appended claims, disclose the presence of the recited features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The term "and / or" includes any and all combinations of one or more of the associated listed elements, if any. In the claims and the specification, unless otherwise specified, the terms "connected", "coupled", "joined", "linked", or their synonyms, and all their inflected forms, do not necessarily deny the existence of one or more intermediate elements between, for example, two that are "connected" or "coupled" to each other or "linked" to each other. In the claims and the specification, the term "any", if any, should be understood as a term having the same meaning as the universal quantifier ∀ unless otherwise specified. For example, the expression "for any X" has the same meaning as "for all X" or "for each X".

[0045] Unless otherwise specified, all terms used in this specification (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the related art and this disclosure, and should not be interpreted ideally or overly formally unless explicitly defined otherwise.

[0046] In the description of the present invention, it will be understood that many techniques and steps are disclosed. Each of these has individual advantages and can also be used in combination with one or more, or in some cases all, of the other disclosed techniques. Therefore, to avoid complication, this specification refrains from describing every possible combination of the individual techniques or steps. Nevertheless, the specification and claims should be read with the understanding that such combinations are fully within the scope of the present invention and the claims.

[0047] In the following claims, all structural, material, acts, and equivalents of the corresponding functional elements combined with a means or step are intended to include, if any, the structure, material, or act for performing the function in combination with other elements.

[0048] As described above, embodiments of the present invention have been described, but the present invention is not limited to these embodiments. Various changes and modifications are permitted without departing from the gist of the present invention. The selected and described embodiments are for explaining the principles of the present invention and its practical applications. The present invention can be used in various embodiments with various changes or modifications, and such changes or modifications are determined according to the expected use. All such changes and modifications are intended to be included within the scope of the present invention as defined by the appended claims and are intended to be given the same protection when interpreted in accordance with the breadth fairly, legally, and equitably accorded.

Claims

1. A dielectric waveguide formed of a dielectric, wherein two or more cavities extending in the longitudinal direction of the dielectric waveguide are present inside the dielectric waveguide, in a cross-section of the dielectric waveguide perpendicular to the longitudinal direction of the dielectric waveguide, the two or more cavities are arranged in line symmetry or rotational symmetry, both ends of the dielectric waveguide are closed, a through-hole that connects at least one of the two or more cavities to the outside of the dielectric waveguide is formed in the dielectric waveguide Dielectric waveguide.

2. In the dielectric waveguide according to Claim 1, two different cavities among the two or more cavities do not communicate with each other Dielectric waveguide characterized by this.

3. In the dielectric waveguide according to Claim 1 or Claim 2, in the frequency band of the electromagnetic wave propagating through the dielectric waveguide, the number of propagation modes of the electromagnetic wave is 1 in at least one of vertical polarization and horizontal polarization Dielectric waveguide characterized by this.

4. In the dielectric waveguide according to any one of Claims 1 to 3, in a cross-section of the dielectric waveguide perpendicular to the longitudinal direction of the dielectric waveguide, the outer peripheral shape of the dielectric waveguide is any one of a square, a rectangle, a circle, and an ellipse, and the shape of each of the two or more cavities is any one of a square, a rectangle, a circle, and an ellipse Dielectric waveguide characterized by this.

5. A wireless antenna capable of transmitting and receiving signals in the millimeter wave band or the quasi-millimeter wave band, including the dielectric waveguide according to any one of Claims 1 to 4 and a dielectric attachment formed of a dielectric, the dielectric attachment is located on or near the dielectric waveguide, the relative permittivity of the dielectric waveguide is larger than the relative permittivity of the surroundings of the dielectric waveguide excluding the dielectric attachment Wireless antenna.

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