JP7563447B2 - Flexible Substrate Waveguide - Google Patents

Description

The present disclosure relates to a waveguide with a flexible substrate.

The next-generation 5G (5th Generation) system, which is a wireless broadband communication system, uses radio waves in the millimeter wave band.

For example, a waveguide is used as a means for transmitting radio waves in the millimeter wave band (Patent Document 1, Patent Document 2).

Japanese Patent Application Publication No. 08-195605 JP 2017-228839 A

High-frequency signals transmitted from a base station through a waveguide are input, for example, to a circuit board and radiated to the outside through an antenna. When inputting high-frequency signals from the waveguide to the circuit board, it is desirable to transmit them efficiently. In addition, the use of flexible boards as circuit boards is being considered.

The present disclosure provides a technique for inputting a high-frequency signal propagating through a waveguide into a flexible substrate.

The present disclosure relates to a waveguide with a flexible substrate, the flexible substrate being provided along the outer surface of the waveguide such that a portion of the flexible substrate overlaps with the slit, and into which a high-frequency signal that has propagated through the waveguide is input from the slit.

The present disclosure provides a technology for inputting a high-frequency signal propagating through a waveguide into a flexible substrate.

FIG. 2 is a perspective view of a waveguide with a flexible substrate according to the first embodiment. FIG. 2 is a perspective view of a waveguide to which a flexible substrate according to the first embodiment is attached. 1 is a cross-sectional view of a waveguide with a flexible substrate according to a first embodiment; 4 is an enlarged cross-sectional view of a connection portion of the waveguide with a flexible substrate according to the first embodiment. FIG. 4 is a diagram showing an analytical model for analyzing the propagation characteristics of the waveguide with a flexible substrate according to the first embodiment; FIG. 5A to 5C are diagrams illustrating the results of analyzing the propagation characteristics of the waveguide with the flexible substrate according to the first embodiment. FIG. 11 is a cross-sectional view of a waveguide with a flexible substrate according to a second embodiment. FIG. 11 is an enlarged cross-sectional view of a connection portion of a waveguide with a flexible substrate according to a second embodiment. FIG. 11 is a top view of an unfolded flexible substrate according to a second embodiment. FIG. 11 is a bottom view of the unfolded flexible substrate of the second embodiment. 13A and 13B are diagrams illustrating the results of analyzing the propagation characteristics of a waveguide with a flexible substrate according to the second embodiment. FIG. 11 is a cross-sectional view of a waveguide with a flexible substrate according to a third embodiment. FIG. 13 is a cross-sectional view of a waveguide with a flexible substrate according to a fourth embodiment. FIG. 13 is a cross-sectional view of a waveguide with a flexible substrate according to a fifth embodiment. FIG. 13 is a side view of the waveguide of the flexible substrate-attached waveguide of the fifth embodiment. FIG. 13 is a cross-sectional view of a waveguide with a flexible substrate according to a sixth embodiment. FIG. 13 is a side view of a flexible substrate of a waveguide with a flexible substrate according to a sixth embodiment.

Below, the form for implementing the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding components are given the same or corresponding reference numerals, and duplicate explanations may be omitted. For ease of understanding, the scale of each part in the drawings may differ from the actual scale. In directions such as parallel, right angle, orthogonal, horizontal, vertical, up and down, left and right, deviations are permitted to the extent that do not impair the effect of the embodiment. The shape of the corners is not limited to right angles, and may be rounded in a bow shape. Parallel, right angle, orthogonal, horizontal, and vertical may include approximately parallel, approximately right angle, approximately orthogonal, approximately horizontal, and approximately vertical.

First Embodiment
<Waveguide with flexible substrate 1>
The flexible substrate-equipped waveguide 1 of the first embodiment is connected to a high-frequency signal propagating through the waveguide 20 by wrapping a flexible substrate 30 around the waveguide 20. The flexible substrate 30 is wound around the waveguide 20 and provided along an outer surface 20s1 of the waveguide 20. Fig. 1 is a perspective view of the flexible substrate-equipped waveguide 1 of the first embodiment. Fig. 2 is a perspective view of the waveguide 20 to which the flexible substrate 30 of the first embodiment is attached. Fig. 3 is a cross-sectional view of the flexible substrate-equipped waveguide 1 of the first embodiment.

For ease of explanation, an XYZ Cartesian coordinate system is set in the figure. For coordinate axes perpendicular to the paper surface of the drawing, a cross in a circle indicates that the back side relative to the paper surface is positive, and a black circle in a circle indicates that the front side relative to the paper surface is positive. However, this coordinate system is defined for the purpose of explanation and does not limit the attitude of the flexible board or the waveguide. In this disclosure, unless otherwise specified, the Z axis is the extension direction of the waveguide 20, and the X and Y axes are perpendicular to the extension direction of the waveguide 20.

The flexible substrate-equipped waveguide 1 of the first embodiment is used to transmit radio waves in the millimeter wave band used in the next-generation 5G system. For example, the waveguide 20 connects from a base station to an antenna installed in the space where the user is located.

The antenna may be, for example, a patch antenna or a dipole antenna formed from a flexible substrate. The antenna may also be a slot antenna formed by opening a slot in the waveguide. Furthermore, another waveguide may be connected to the end of the waveguide 20. For example, another waveguide may be connected via a flexible substrate.

The band of radio waves transmitted through the waveguide 20 in the first embodiment is, for example, 27.5 GHz to 29 GHz. For example, the center frequency is 28 GHz. This band is divided into 400 MHz bands for use by each operator. Note that the frequency band is not limited to 27.5 GHz to 29 GHz, and may be, for example, a frequency band centered around 26 GHz or 39 GHz. Furthermore, the frequency band is not limited to the millimeter wave band, and may be another frequency band.

The first embodiment of the flexible substrate-equipped waveguide 1 comprises a waveguide 20 whose ends are short-circuited by a closing member 10, and a flexible substrate 30. Each element of the flexible substrate-equipped waveguide 1 will be described.

[Waveguide 20]
The waveguide 20 is a waveguide that serves as a waveguide through which radio waves in the millimeter wave band propagate. The waveguide 20 is a cylindrical tube that extends in the direction in which the radio waves propagate. In FIG. 3, the direction in which the radio waves propagate is the Z direction.

The waveguide 20 comprises a dielectric tube 21 and a metal coating 22 covering the outside of the dielectric tube 21.

The dielectric tube 21 is a component that functions as a transmission path through which radio waves propagate. In the waveguide 20, radio waves propagate through the dielectric tube 21.

The dielectric tube 21 is formed of a dielectric material, for example, a fluororesin. Examples of the fluororesin that can be used include polytetrafluoroethylene (PTFE) and perfluoroalkoxyalkane (PFA).

For example, when the frequency band is 28 GHz, the outer diameter of the waveguide 20 is preferably 5 mm to 9 mm. The outer diameter of the dielectric tube 21 is 1 mm to 2 mm thinner than the outer diameter of the waveguide 20.

The metal coating 22 is a member that defines the transmission path. The metal coating 22 is formed from a conductive member, for example, copper. The metal coating 22 is formed, for example, by plating. Note that the metal coating 22 is not limited to being formed by plating, and for example, the metal coating 22 may be formed by wrapping copper foil or a metal mesh. Note that a further insulating coating may be provided on the outside of the metal coating 22 of the waveguide 20.

The +Z side end of the waveguide 20 is closed by a closing member 10. The closing member 10 is formed of a conductive material, such as copper. The closing member 10 is mechanically and electrically connected to the metal coating 22 of the waveguide 20, for example, by soldering, brazing, applying a conductive paste, or the like. By closing the waveguide 20 with the closing member 10, the end of the waveguide 20 is short-circuited.

The waveguide 20 has a slit 20p on the outer surface 20s1 of the waveguide 20. The slit 20p serves as a passageway for guiding radio waves propagating inside the waveguide 20 to the outside. The slit 20p is provided at a position one-quarter of a wavelength away from the short-circuited surface of the waveguide 20. Specifically, the center of the slit 20p is provided at a position one-quarter of a wavelength away from the short-circuited surface of the inner surface of the closing member 10 in the longitudinal direction of the waveguide 20 (-Z direction).

[Flexible substrate 30]
The flexible substrate 30 is, for example, a circuit board that processes a high-frequency signal transmitted from a base station via the waveguide 20. A line or a waveguide for propagating a high-frequency signal is formed on the flexible substrate 30. For example, a microstrip line or a coplanar line may be used as the line, and a substrate integrated waveguide (SIW) may be used as the waveguide.

The flexible substrate 30 only needs to have a degree of flexibility that allows it to be wound around a cylindrical waveguide without resistance, and the thickness of the flexible substrate 30 is preferably 0.012 mm or more and 0.8 mm or less. By making the flexible substrate 30 thinner, the flexibility of the flexible substrate 30 can be increased. The dielectric of the flexible substrate 30 is formed of a fluorine-based resin, liquid crystal, polyimide, or the like. As the fluorine-based resin, for example, perfluoroalkoxyalkane (PFA) can be used.

The flexible substrate 30 may include an amplifier on the substrate. The flexible substrate 30 may also include an antenna such as a patch antenna or a dipole antenna.

(Connection between the Waveguide 20 and the Flexible Substrate 30)
Fig. 4 is an enlarged cross-sectional view of a connection portion between the waveguide 20 and the flexible substrate 30 of the flexible substrate-equipped waveguide 1 of the first embodiment. Note that Fig. 4 shows a state before the flexible substrate 30 is wound around the waveguide 20 and attached.

An example in which the flexible substrate 30 constitutes a substrate integrated waveguide (SIW) will be described. The flexible substrate 30 includes an upper conductive layer 31, a lower conductive layer 32, and a dielectric layer 33 sandwiched between the upper conductive layer 31 and the lower conductive layer 32. The upper conductive layer 31 has a slot 30p. The slot 30p has approximately the same shape as the slit 20p of the waveguide 20. The flexible substrate 30 also includes a via 35 that connects the upper conductive layer 31 and the lower conductive layer 32. Therefore, the upper conductive layer 31 and the lower conductive layer 32 of the flexible substrate 30 are at the same potential.

As shown in FIG. 4, when connecting the waveguide 20 and the flexible substrate 30, the slit 20p of the waveguide 20 and the slot 30p of the flexible substrate 30 are aligned. Then, both sides of the slot 30p of the flexible substrate 30 are attached by wrapping it around the waveguide 20. When wrapping, for example, a conductive paste may be applied or a conductive adhesive may be used for bonding. By wrapping the flexible substrate 30 around the waveguide 20, a part of the flexible substrate 30 overlaps with the slit 20p of the waveguide 20. In addition, by wrapping the flexible substrate 30 around the waveguide 20, the flexible substrate 30 is provided so as to follow the outer surface of the waveguide 20. In addition, the metal coating 22 of the waveguide 20 and the upper surface conductive layer 31 of the flexible substrate 30 come into contact with each other, thereby preventing leakage of radio waves from the slit 20p.

(Propagation characteristics of radio waves from the waveguide 20 to the flexible substrate 30)
The propagation characteristics of the radio waves propagating through the waveguide 20 and then to the flexible substrate 30 will be described.

Figure 5 shows an analytical model for analyzing the propagation characteristics of the flexible substrate-equipped waveguide 1 of the first embodiment.

The waveguide MP is a waveguide corresponding to the part of the waveguide 20 through which the radio waves propagate. In FIG. 5, the extension direction of the waveguide MP is the Y axis. The directions perpendicular to the extension direction of the waveguide MP are the X axis and the Z axis. The waveguide MP is modeled as a tube with an inner diameter of 6 mm and an outer diameter of 7 mm, made of polytetrafluoroethylene (PTFE) material, wrapped with 0.01 mm of copper. The waveguide MP is incident on the incident surface SI. In this analysis, a polarized wave in the Z direction (quasi-TE11 mode) is incident on the incident surface SI. In addition, a reflection surface SR is formed on the waveguide MP. The radio waves incident on the incident surface SI are reflected by the reflection surface SR while propagating in the +Y direction inside the waveguide MP. The reflection surface SR is assumed to be a short-circuited surface. A slit SL is provided in the +X direction of the waveguide MP. From the slit SL, the radio waves in the waveguide MP are output to the outside of the waveguide MP. The center of the slit SL is located at a position that is one-quarter of the wavelength of the radio waves in the -Y direction from the reflecting surface SR. In this analysis, the wavelength of the radio waves is set to a frequency of 28 GHz, and the distance in the Y-axis direction from the center of the slit SL to the reflecting surface is set to 5 mm. The length of the slit SL in the Y-axis direction is 4.35 mm, and the width (the length along the outer periphery of the waveguide MF on a plane perpendicular to the Y-axis) is 0.9 mm.

The waveguide MF is a waveguide corresponding to the part of the flexible substrate 30 where the radio waves propagate. The waveguide MF is modeled as a substrate integrated waveguide (SIW) made in a flexible substrate with a width of 4.5 mm and a thickness of 0.2 mm. The radio waves are incident on the waveguide MF from the slit SL, and the radio waves propagate inside the waveguide MF. The slit SL is a slot of the substrate integrated waveguide (SIW). An iris post IP is provided in the middle of the waveguide of the flexible substrate. The length of each iris post IP in the Y-axis direction is 0.9 mm, and the width (length along the outer circumference of the waveguide MF on a plane perpendicular to the Y-axis) is 0.25 mm. The radio waves are incident on the waveguide MF from the slit SL (slot). The radio waves incident from the slit SL (slot) propagate inside the waveguide MF and are output from the output surface SO. In this analysis, radio waves in the TE10 mode from the emission surface SO were analyzed.

Figure 6 shows the results of an analysis of the propagation characteristics of the flexible substrate-equipped waveguide of the first embodiment. The horizontal axis indicates frequency. The vertical axis indicates the transmission coefficient and reflection coefficient in decibels. The transmission coefficient T1 represents the ratio of the radio wave intensity emitted from the exit surface SO to the radio wave intensity incident from the entrance surface SI. The reflection coefficient R1 represents the ratio of the radio wave intensity reflected to the entrance surface SI without emitting from the exit surface SO to the radio wave intensity incident from the entrance surface SI.

6, by positioning the slit SL at a quarter distance from the reflecting surface SR, radio waves can be transmitted from the waveguide MP to the waveguide MF. As a result of the above, by locating the slit SL along the outer surface 20s1 of the waveguide 20 so as to overlap with the slit 20p of the waveguide 20, radio waves can be transmitted from the waveguide 20 to the flexible substrate 30.

(Action and Effects)
In the waveguide 1 with a flexible substrate of the first embodiment, the flexible substrate 30 is arranged along the outer surface 20s1 of the waveguide 20 so as to overlap the slit 20p of the waveguide 20, so that a high-frequency signal propagated through the waveguide 20 can be input to the flexible substrate 30.

Second Embodiment
<Waveguide with flexible substrate 2>
The flexible substrate-equipped waveguide 2 of the second embodiment is connected to a high-frequency signal propagating through the waveguide 20 by wrapping the flexible substrate 130 around the waveguide 20 multiple times. The flexible substrate 130 is wound around the waveguide 20 and provided along the outer surface 20s1 of the waveguide 20. FIG. 7 is a cross-sectional view of the flexible substrate-equipped waveguide 2 of the second embodiment. FIG. 8 is an enlarged cross-sectional view of a connection portion of the flexible substrate-equipped waveguide 2 of the second embodiment. Note that FIG. 8 shows the flexible substrate 130 wound around the waveguide 20 in an expanded state. Also, in FIG. 8, the flexible substrate 130 is illustrated enlarged with respect to the waveguide 20 to explain the state in which the flexible substrate 130 is wound multiple times.

In the second embodiment of the flexible substrate-equipped waveguide 2, the flexible substrate 130 is wound around the waveguide 20 multiple times. Specifically, the flexible substrate 130 is laminated five times at the slit 20p of the waveguide 20. Note that the number of times of winding is not limited to five times, and may be two or more times.

[Flexible substrate 130]
The flexible substrate 130 has a microstrip line 130d formed as a line. The flexible substrate 130 includes an upper conductive layer 131, a lower conductive layer 132, and a dielectric layer 133 sandwiched between the upper conductive layer 131 and the lower conductive layer 132. The flexible substrate 130 also includes a via 135 for connecting the upper conductive layer 131 and the lower conductive layer 132. In FIG. 8, the numbers in parentheses indicate the layers stacked at the position of the slit 20p of the waveguide 20. For example, the upper conductive layer 131 of the first layer of the flexible substrate 130 that contacts the waveguide 20 is indicated as the upper conductive layer 131(1). Similarly, the upper conductive layer 131, the lower conductive layer 132, and the dielectric layer 133 of the nth layer are respectively indicated as the upper conductive layer 131(n), the lower conductive layer 132(n), and the dielectric layer 133(n).

The flexible substrate 130 is laminated multiple times at the slit 20p. The flexible substrate 130 has a connection portion 130a where a part of the upper surface conductive layer 131 (1) of the first layer is removed and the dielectric layer 133 (1) of the first layer is exposed. The slit 20p of the waveguide 20 contacts the connection portion 130a. Also, on the opposite side of the dielectric layer 133 (1) of the part where the slit 20p of the waveguide 20 contacts, a microstrip line 130d is formed on the lower surface conductive layer 132 (1) of the first layer. And, in the part corresponding to the connection portion 130a of the second to fourth layers, the upper surface conductive layer 131 and the lower surface conductive layer 132 are removed to expose the dielectric layer 133. That is, in the portion corresponding to the connection portion 130a of the second to fourth layers, the top surface conductive layer 131(2), the top surface conductive layer 131(3), the top surface conductive layer 131(4), the bottom surface conductive layer 132(2), the bottom surface conductive layer 132(3), and the bottom surface conductive layer 132(4) are removed. In the portion corresponding to the connection portion 130a of the fifth layer, the top surface conductive layer 131(5) and the bottom surface conductive layer 132(5) are formed. The top surface conductive layer 131(5) becomes the reflection surface 130b that reflects the radio wave incident from the connection portion 130a.

By wrapping the flexible substrate 130 around the waveguide 20, the flexible substrate 130 is provided so as to conform to the outer surface of the waveguide 20. When wrapping, for example, a conductive paste may be applied or a conductive adhesive may be used for bonding. In addition, contact between the metal coating 22 of the waveguide 20 and the upper surface conductive layer 131(1) of the first layer of the flexible substrate 130 can prevent radio waves from leaking from the slit 20p.

Figures 9 and 10 show a flexible substrate 130 forming the laminated structure shown in Figure 8. Figure 9 is a top view of the unfolded flexible substrate 130 of the second embodiment. Figure 10 is a bottom view of the unfolded flexible substrate 130 of the second embodiment.

Regions RT1, RT2, RT3, and RT4 indicate regions where the top surface conductive layer 131 of the flexible substrate 130 has been removed. Region RT1 is the region that corresponds to the connection portion 130a. Regions RT2, RT3, and RT4 are the regions that correspond to the connection portion 130a when the flexible substrate 130 is wrapped around the waveguide 20. Note that the top surface conductive layer 131 of region RT2 has also been removed from the region that overlaps with the wiring portion of the microstrip line 130d. Region RT5 represents the portion where the fifth layer of the top surface conductive layer 131 is provided and becomes the reflective surface 130b. Note that regions RT1, RT2, RT3, RT4, and RT5 are provided at intervals that correspond to the circumference of the waveguide 20.

Regions RB1, RB2, RB3, and RB4 indicate the regions where the bottom conductive layer 132 of the flexible substrate 130 has been removed. Region RB1 is the region where the microstrip line 130d is formed. Regions RB2, RB3, and RB4 are the regions that correspond to the connection portion 130a when the flexible substrate 130 is wrapped around the waveguide 20. Region RT5 represents the portion where the fifth layer of the bottom conductive layer 132 is provided outside the reflecting surface 130b. Regions RB1, RB2, RB3, RB4, and RB5 are provided at intervals corresponding to the circumference of the waveguide 20.

The portion corresponding to the connection portion 130a will be described. The actual thickness of the upper surface conductive layer 131 and the lower surface conductive layer 132 is about 20 μm, while the actual thickness of the dielectric layer 133 is 200 μm. Furthermore, by wrapping the flexible substrate 130 around the waveguide 20, the layers of the laminated flexible substrate 130 are in close contact with each other. That is, the portion corresponding to the connection portion 130a between the lower surface conductive layer 132 (1) of the first layer and the upper surface conductive layer 131 (5) of the fifth layer is laminated with the dielectric layer 133 (2), the dielectric layer 133 (3), and the dielectric layer 133 (4) in close contact with each other. In FIG. 8, a gap is shown between the layers to clarify the relationship between the layers. Therefore, the outside of the microstrip line 130d can be regarded as a layer in which multiple dielectric layers 133 are laminated, specifically, a layer in which three layers are laminated.

The distance L1 between the microstrip line 130d and the reflecting surface 130b can be increased by stacking the dielectric layer 133 multiple times.

An electromagnetic field analysis was performed on the flexible substrate-equipped waveguide 2 of the second embodiment. The analysis was performed with the dimensions of the slit 20p of the waveguide 20 being 5.4 mm in length and 0.5 mm in width, the flexible substrate 130 being a fluororesin substrate with a thickness of 0.2 mm, the conductive layer being copper with a line width of 0.2 mm, and the distance L1 of the resonator 130c being 2.5 mm.

Figure 11 is a diagram showing the results of analyzing the propagation characteristics of the flexible substrate-equipped waveguide 2 of the second embodiment. The horizontal axis indicates frequency. The vertical axis indicates the transmission coefficient and reflection coefficient in decibels. The transmission coefficient T2 represents the ratio of the radio wave intensity transmitted through the microstrip line 130d to the radio wave intensity of the Y-direction polarized wave (quasi-TE11 mode) in Figure 7 that is incident on the waveguide 20. The reflection coefficient R2 represents the ratio of the radio wave intensity that is reflected without being incident on the microstrip line 130d to the radio wave intensity of the Y-direction polarized wave (quasi-TE11 mode) in Figure 7 that is incident on the waveguide 20.

The results in Figure 11 show that at a frequency of 28 GHz, signals are efficiently propagated from the waveguide 20 to the microstrip line 130d.

Third Embodiment
<Waveguide with flexible substrate 3>
The waveguide 3 with a flexible substrate of the third embodiment is connected to a high-frequency signal propagating through the waveguide 220 by wrapping a flexible substrate 230 around the waveguide 220. In the waveguide 3 with a flexible substrate of the third embodiment, radio waves are incident on the flexible substrate 230 from slits 220p1 and slits 220p2 provided in two places on the waveguide 220. Fig. 12 is a cross-sectional view of the waveguide 3 with a flexible substrate of the third embodiment.

The waveguide 220 comprises a dielectric tube 221 and a metal coating 222 covering the outside of the dielectric tube 221.

The dielectric tube 221 is a component that functions as a transmission path along which radio waves propagate. In the waveguide 220, radio waves propagate through the dielectric tube 221. The metal coating 222 is a component that defines the transmission path. Note that the materials of the dielectric tube 221 and the metal coating 222 are the same as those of the dielectric tube 21 and the metal coating 22 of the waveguide 20.

The waveguide 220 has a plurality of slits. Specifically, the waveguide 220 has two slits, 220p1 and 220p2. The slits 220p1 and 220p2 serve as a passageway for guiding the radio waves propagating inside the waveguide 220 to the outside. The slits 220p1 and 220p2 are provided at a position a quarter of a wavelength away from the short-circuited surface of the waveguide 220.

Flexible substrate 230 receives radio waves from two points, slits 220p1 and 220p2. Other than being input from two points, it is similar to flexible substrate 30 and flexible substrate 130.

The flexible substrate 230 can convert the polarization in two directions by inputting radio waves polarized in the Y direction (quasi-TE11 mode) through the slit 220p1 and polarized in the X direction (quasi-TE11 mode) through the slit 220p2.

<Action and Effects>
According to a waveguide with a flexible substrate, which includes the waveguide of the present disclosure and a flexible substrate, a high-frequency signal propagating through the waveguide can be input to the flexible substrate. The waveguide with a flexible substrate of the present disclosure can be produced by wrapping the flexible substrate around the waveguide.

<Modification>
The shape of the waveguide is not limited to a cylindrical shape. For example, the waveguide may be a rectangular tube. The waveguide may have a cavity inside, and if the metal coating is self-supporting, the dielectric tube may be omitted.

Fourth Embodiment
<Waveguide with flexible substrate 4>
The waveguide 4 with a flexible substrate of the fourth embodiment is connected to a high frequency signal propagating through the waveguide 320 by wrapping a flexible substrate 330 around the waveguide 320. In the waveguide 4 with a flexible substrate of the fourth embodiment, the flexible substrate 330 is adhered to the waveguide 320 by a conductive adhesive 350. Fig. 13 is a cross-sectional view of the waveguide 4 with a flexible substrate of the fourth embodiment.

The waveguide 320 has a metal coating 322. The metal coating 322 is a member that defines the transmission path. The metal coating 322 is self-supporting and can maintain its shape, so the inside is a cavity 321. That is, in the waveguide 320, the radio waves propagate through the air in the cavity 321. Note that instead of the air in the cavity 321, a dielectric tube may be provided in the cavity 321. Note that the material of the metal coating 322 is the same as that of the metal coating 22 of the waveguide 20.

The waveguide 320 has a slit 320p. Radio waves propagating through the cavity 321 are incident on the flexible substrate 330 from the slit 320p.

The flexible substrate 330 constitutes a substrate integrated waveguide (SIW). The flexible substrate 330 includes an upper conductive layer 331, a lower conductive layer 332, and a dielectric layer 333 sandwiched between the upper conductive layer 331 and the lower conductive layer 332. In order to connect the upper conductive layer 331 and the lower conductive layer 332, the flexible substrate 330 includes a via (not shown). Therefore, the upper conductive layer 331 and the lower conductive layer 332 of the flexible substrate 330 are at the same potential.

The upper surface conductive layer 531 has a slot having approximately the same shape as the slit 320p. The radio waves from the slit 320p are introduced into the slot.

A conductive adhesive 350 is applied to the outer surface of the metal coating 322. The conductive adhesive 350 is, for example, an anisotropic conductive film sheet made of resin mixed with fine metal particles. The conductive adhesive 350 is applied while avoiding the slits 320p so as not to block the slits 320p. The conductive adhesive 350 is also applied so as to surround the slits 320p.

A conductive adhesive 350 is applied, the flexible substrate 330 is wrapped around the waveguide 320, and the conductive adhesive 350 is cured. The conductive adhesive 350 is cured to fix the flexible substrate 330 to the waveguide 320. By fixing the waveguide 320 and the flexible substrate 330 using the conductive adhesive 350, an electrical connection can be made between the metal coating 322 and the upper surface conductive layer 331 of the flexible substrate 330.

In addition, by applying conductive adhesive 350 so as to surround slit 320p, leakage of electromagnetic waves from the vicinity of slit 320p can be suppressed.

Fifth Embodiment
<Waveguide with flexible substrate 5>
The waveguide 5 with a flexible substrate of the fifth embodiment is connected to a high frequency signal propagating through the waveguide 320 by wrapping a flexible substrate 330 around the waveguide 320. In the waveguide 5 with a flexible substrate of the fifth embodiment, the flexible substrate 330 is bonded to the waveguide 320 by solder 450. Fig. 14 is a cross-sectional view of the waveguide 5 with a flexible substrate of the fifth embodiment.

Solder 450 is applied to the outer surface of metal coating 322 facing flexible substrate 330. Solder 450 is, for example, cream solder. A protective sheet 460 is attached around slit 320p so that solder 450 does not block slit 320p. Protective sheet 460 is, for example, polyimide tape.

15 is a side view of the waveguide 320 of the flexible substrate-equipped waveguide 5 of the fifth embodiment. The protective sheet 460 is attached to the outer periphery of the slit 320p so that the solder 450 does not flow into the slit 320p and block it. It is preferable that the protective sheet 460 is as narrow as possible to prevent deterioration of the propagation characteristics of the radio wave.

A protective sheet 460 is attached to the outer periphery of the slit 320p of the metal coating 322 of the waveguide 320. Solder 450 is then applied to the outer surface of the metal coating 322 of the waveguide 320 that faces the flexible substrate 330. Next, the flexible substrate 330 is wrapped around the waveguide 320. The waveguide 320 with the flexible substrate 330 wrapped around it is then heated and cooled to harden the solder 450.

The solder 450 hardens to fix the flexible substrate 330 to the waveguide 320. By fixing the waveguide 320 and the flexible substrate 330 using the solder 450, an electrical connection can be made between the metal coating 322 and the upper surface conductive layer 331 of the flexible substrate 330.

In addition, the protective sheet 460 can prevent the solder 450 from flowing into the slit 320p. Also, by providing the solder 450 so as to surround the slit 320p, leakage of electromagnetic waves from the vicinity of the slit 320p can be suppressed.

Sixth Embodiment
<Waveguide with flexible substrate 6>
The waveguide 6 with a flexible substrate of the sixth embodiment is connected to a high frequency signal propagating through the waveguide 320 by wrapping a flexible substrate 530 around the waveguide 320. In the waveguide 6 with a flexible substrate of the sixth embodiment, the flexible substrate 530 is bonded to the waveguide 320 by solder 450. Fig. 16 is a cross-sectional view of the waveguide 6 with a flexible substrate of the fifth embodiment.

The flexible substrate 530 constitutes a substrate integrated waveguide (SIW). The flexible substrate 530 includes an upper conductive layer 531, a lower conductive layer 532, and a dielectric layer 533 sandwiched between the upper conductive layer 531 and the lower conductive layer 532. In order to connect the upper conductive layer 531 and the lower conductive layer 532, the flexible substrate 530 includes a through hole 530th, which will be described later. Therefore, the upper conductive layer 531 and the lower conductive layer 532 of the flexible substrate 530 are at the same potential.

Figure 17 is a side view of the flexible substrate 530 of the flexible substrate-equipped waveguide 6 of the sixth embodiment. Figure 17 is a side view of the flexible substrate 530 seen from the side of the upper surface conductive layer 531.

The upper surface conductive layer 531 has a slot 530p having approximately the same shape as the slit 320p. Radio waves from the slit 320p are introduced into the slot 530p. A plurality of through holes 530th are provided to surround the slot 530p. The plurality of through holes 530th form a waveguide of the flexible substrate 530. Each of the plurality of through holes 530th electrically connects the upper surface conductive layer 531 and the lower surface conductive layer 532, and penetrates the dielectric layer 533.

The plurality of solder through holes 530sh are provided on the outside of the slots 530p of the plurality of through holes 530th. Each of the plurality of solder through holes 530sh connects the upper surface conductive layer 531 and the lower surface conductive layer 532, and penetrates the dielectric layer 533. The solder through holes 530sh have a larger diameter than the through holes 530th. Solder 450 is injected from the solder through holes 530sh.

The flexible substrate 530 is wrapped around the waveguide 320. Then, solder 450 is injected through the solder through-hole 530sh. Next, the waveguide 320 wrapped around the flexible substrate 530 is heated and then cooled to harden the solder 450. At this time, the solder 450 injected and heated through the solder through-hole 530sh flows into the inside of the through-hole 530th by capillary action and does not reach the slit 320p and slot 530p. Therefore, the solder 450 can be prevented from blocking the slit 320p and slot 530p.

The solder 450 hardens to fix the flexible substrate 530 to the waveguide 320. By fixing the waveguide 320 and the flexible substrate 530 using the solder 450, an electrical connection can be made between the metal coating 322 and the upper surface conductive layer 531 of the flexible substrate 530.

Furthermore, by arranging the solder 450 so as to surround the slit 320p, leakage of electromagnetic waves from the vicinity of the slit 320p can be suppressed.

It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

This application claims priority to basic patent application No. 2020-058876, filed on March 27, 2020, with the Japan Patent Office, the entire contents of which are incorporated herein by reference.

1, 2, 3, 4, 5, 6 Waveguide with flexible substrate 20, 220, 320 Waveguide 20p, 220p1, 220p2, 320p Slit 30, 130, 230, 330, 530 Flexible substrate 30p, 530p Slot 130b Reflecting surface 130c Resonator 130d Microstrip line 133 Dielectric layer

Claims (6)

A waveguide having a slit;
A flexible substrate,
the flexible substrate is provided along an outer surface of the waveguide such that a portion of the flexible substrate overlaps with the slit, and a high-frequency signal that has propagated through the waveguide is input from the slit ;
The flexible substrate constitutes a substrate integrated waveguide.
Waveguide with flexible substrate. the substrate integrated waveguide comprises a slot;
The slit and the slot are overlapped and attached.
2. The waveguide with the flexible substrate according to claim 1 . A waveguide having a slit;
A flexible substrate,
the flexible substrate is provided along an outer surface of the waveguide such that a portion of the flexible substrate overlaps with the slit, and a high-frequency signal that has propagated through the waveguide is input from the slit;
the flexible substrate includes a microstrip line;
The flexible substrate is laminated multiple times in the slit.
Waveguide with flexible substrate. a resonator including the microstrip line, a layer in which a plurality of dielectric layers are laminated, and a reflecting surface is formed in a portion of the flexible substrate corresponding to the slit;
4. The waveguide with a flexible substrate according to claim 3 . The slit is provided at a position a quarter of the wavelength of the radio wave propagating through the waveguide from the short-circuited surface of the waveguide.
The waveguide with the flexible substrate according to claim 1 . The slit is provided in plurality.
The waveguide with a flexible substrate according to claim 1 .

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