Distributed Antennas and Distributed Antenna Systems

Abstract

A distributed antenna 20 comprises: a belt-shaped member 1 that extends in a belt shape and has a sheet-shaped dielectric, a first surface which is one surface of the dielectric, and a second surface on the opposite side from the first surface; a transmission path 3 that is provided on one of the first surface and the second surface, or is provided between the first surface and the second surface; and a plurality of antenna elements 2 that are electrically connected to the transmission path 3 and are positioned in a distributed manner on one of the first surface and the second surface, or are electrically connected to the transmission path and are positioned in a distributed manner between the first surface and the second surface.

Description

[Technical Field]

[0001] The present disclosure relates to distributed antennas and distributed antenna systems. [Background technology]

[0002] The millimeter wave band used in antennas for 5G wireless base stations has a high degree of directionality, making stable communication difficult when antennas are installed in one location. In addition, restrictions on the installation of wireless base stations are imposed depending on the weight and dimensions of the equipment, making it difficult to increase the number of wireless base stations installed to expand the coverage area.

[0003] According to the distributed antenna system of Patent Document 1, by comprising a baseband unit that generates high-frequency signals and a plurality of antennas that are separated from the baseband unit and placed in radio wave dead zones, etc., it is possible to realize stable wireless communication in radio wave dead zones such as inside buildings, underground shopping malls, and factories, while expanding the coverage area without being restricted by the installation of radio base stations. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-067855 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with conventional technology, when installing multiple antennas on the wall of a building, for example, each antenna must be attached to the wall one by one. Furthermore, transmission lines connected to these antennas must also be laid along the wall and secured in place. This poses a problem of the complicated installation process.

[0006] The present disclosure has been made in view of the above, and aims to provide a distributed antenna that is easy to install. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the distributed antenna of the present disclosure comprises a strip-shaped member having a plate-shaped dielectric, a first surface which is one surface of the dielectric, and a second surface opposite to the first surface, and extending in a strip-like shape; a transmission line provided on either the first surface or the second surface, or provided between the first surface and the second surface; and a plurality of antenna elements electrically connected to the transmission line and distributed on either the first surface or the second surface, or electrically connected to the transmission line and distributed between the first surface and the second surface. [Effects of the Invention]

[0008] The distributed antenna of the present disclosure has the effect of providing a distributed antenna that is easy to install. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 illustrates an example configuration of a distributed antenna and a base station according to an embodiment of the present disclosure. [Figure 2] A diagram showing an example of the arrangement of multiple antenna elements connected in branches to a transmission line. [Figure 3] A diagram showing an example of the arrangement of antenna elements 2 cascaded to a transmission line. [Figure 4] A diagram showing an example of the layout of signal processing circuits arranged on a transmission line. [Figure 5] FIG. 1 shows an example of the configuration of a belt-shaped member 1 in which a rigid portion 1B is fixed (laminated) to a flexible portion 1A. [Figure 6] FIG. 1 shows an example of the configuration of a belt-shaped member 1 in which a flexible portion 1A and a rigid portion 1B provided at a position distant from the flexible portion 1A are connected by a connector 1C or the like. [Figure 7] FIG. 1 is a diagram illustrating an example in which a plurality of antenna elements are distributed; [Figure 8] FIG. 1 shows an example of the configuration of a signal processing circuit. [Figure 9] FIG. 1 is a diagram showing an example of a connection between an amplifier module having a plurality of signal processing circuits and a plurality of antenna elements connected to the amplifier module. [Figure 10] FIG. 10 is a diagram showing an example in which an amplifier module is provided on a strip-shaped member. [Figure 11] A diagram illustrating the communication distance when a low-noise amplifier is not installed. [Figure 12] A diagram to explain the communication distance when a low-noise amplifier is installed [Figure 13] A diagram showing an example of a configuration in which multiple low-noise amplifiers are provided to extend the communication distance. [Figure 14] Schematic diagram of a branch-connected distributed antenna [Figure 15] Schematic diagram of a cascaded distributed antenna [Figure 16] Enlarged view of branch-connected distributed antenna [Figure 17] Diagram to explain what it would look like if a branch-connected distributed antenna was installed on the ceiling inside a station [Figure 18] Diagram to explain what it would look like if a cascade-connected distributed antenna was installed on the ceiling inside a station. [Figure 19] FIG. 10 is a diagram for explaining a modified example of a signal processing circuit. [Figure 20] FIG. 10 is a diagram showing a first modified example of a belt-shaped member. [Figure 21] FIG. 10 is a diagram showing a second modified example of the belt-shaped member. [Figure 22] Diagram showing an example of the flexible module configuration [Figure 23] A diagram showing an example of the configuration of a distributed antenna for a repeater [Figure 24] Diagram showing the layout of the antenna and poles used in this test [Figure 25] Diagram showing the configuration of the antenna used in this test [Figure 26] A diagram showing the antenna characteristics of the antenna used in this test [Figure 27]Table showing the measurement results (S21) for each pillar installation condition [Figure 28] Graph showing the measurement results (S21) from this test for each pillar installation condition [Figure 29] 1 is a plan view of a flexible antenna according to an embodiment; [Figure 30] FIG. 1 is a diagram illustrating an example of a cross-sectional configuration of a flexible antenna according to an embodiment. [Figure 31] FIG. 10 is a diagram showing another example of a cross-sectional configuration of a flexible antenna according to an embodiment. [Figure 32] FIG. 1 is a diagram showing an example of installation of a flexible antenna on a pole according to an embodiment; [Figure 33] Cross-sectional view of the flexible antenna shown in Figure 32 along the XY plane [Figure 34] FIG. 10 is a diagram showing a first modified example of an antenna pattern in the flexible antenna according to the embodiment; [Figure 35] FIG. 10 is a diagram showing a second modified example of the antenna pattern in the flexible antenna according to the embodiment. [Figure 36] FIG. 10 is a diagram showing a third modified example of the antenna pattern in the flexible antenna according to the embodiment. [Figure 37A] FIG. 10 is a diagram showing a first example of antenna characteristics of a flexible antenna according to an embodiment; [Figure 37B] FIG. 10 is a diagram showing a first example of antenna characteristics of a flexible antenna according to an embodiment; [Figure 38A] FIG. 10 is a diagram showing a second example of antenna characteristics of the flexible antenna according to the embodiment; [Figure 38B] FIG. 10 is a diagram showing a second example of antenna characteristics of the flexible antenna according to the embodiment; [Figure 39A] FIG. 10 is a diagram showing a third example of antenna characteristics of the flexible antenna according to the embodiment; [Figure 39B] FIG. 10 is a diagram showing a third example of antenna characteristics of the flexible antenna according to the embodiment; [Figure 40A] FIG. 10 is a diagram showing a fourth example of antenna characteristics of the flexible antenna according to the embodiment; [Figure 40B]FIG. 10 is a diagram showing a fourth example of antenna characteristics of the flexible antenna according to the embodiment; [Figure 41A] FIG. 10 is a diagram showing a fifth example of antenna characteristics of the flexible antenna according to the embodiment. [Figure 41B] FIG. 10 is a diagram showing a fifth example of antenna characteristics of the flexible antenna according to the embodiment. [Figure 42] FIG. 10 is a diagram showing a fourth modified example of the antenna pattern in the flexible antenna according to the embodiment. [Figure 43] An example of installation of the flexible antenna shown in Figure 42 on a pole. [Figure 44A] FIG. 43 is a diagram showing an example of antenna characteristics of the flexible antenna shown in FIG. 42. [Figure 44B] FIG. 43 is a diagram showing an example of antenna characteristics of the flexible antenna shown in FIG. 42. DETAILED DESCRIPTION OF THE INVENTION

[0010] Distributed antennas according to embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0011] Fig. 1 is a diagram illustrating an example configuration of a distributed antenna and a base station according to an embodiment of the present disclosure. The distributed antenna system 300 illustrated in Fig. 1 includes a base station 10, a distributed antenna 20, and a communication line 30. For example, the base station 10 is connected to the distributed antenna 20 via the communication line 30. The distributed antenna 20 is, for example, an antenna for a base station such as 5G.

[0012] The distributed antenna 20 includes a strip-shaped member 1, which is a strip-shaped dielectric material, and a plurality of antenna elements 2 distributed on the strip-shaped member 1. The distributed antenna 20 also includes a transmission line 3, which is a signal transmission line disposed on the strip-shaped member 1 and connected to a communication line 30, and which couples the plurality of antenna elements 2, and a signal processing circuit 4 for processing signals transmitted between the antenna elements 2 and a base station 10. The transmission line 3 may be formed, for example, by a substrate integrated waveguide (SIW), a stripline on a multilayer substrate, or the like. In this case, the transmission line 3 is provided between the first and second surfaces of the strip-shaped member 1. The first and second surfaces of the strip-shaped member 1 will be described in detail later. The transmission line 3 may also be a structure (for example, a microstripline) provided on either the first or second surface.

[0013] The strip-shaped member 1 is, for example, a flexible substrate having a strip-shaped dielectric as its core material. A flexible substrate is flexible enough to be bent, can be repeatedly deformed with a weak force, and maintains its electrical properties even after deformation. Compared to general rigid substrates, flexible substrates are thinner and easier to process, allowing for complex shapes. A flexible substrate has a structure in which a conductor foil is laminated to a thin dielectric film having a thickness of, for example, 12 μm to 500 μm. The dielectric is a material called solder resist (resist / photoresist) or coverlay, such as polyimide or polyester. Furthermore, when the dielectric contains a resin layer (i.e., when the dielectric is partially or entirely a resin layer), the resin layer can contain, for example, fluororesins such as tetrafluoroethylene polymers. The conductor foil can be made of, for example, gold, silver, copper, aluminum, platinum, or chromium. Instead of a flexible substrate, the strip-shaped member 1 may be a rigid substrate having a strip-shaped dielectric as its core material. Examples of rigid substrates include glass composite substrates, glass epoxy substrates, alumina substrates, and composite substrates. The strip-shaped member 1 may have a structure in which multiple dielectric layers are stacked. In this case, multiple antenna elements 2 are electrically connected to the transmission line and are provided between the first and second surfaces of the strip-shaped member 1. In other words, the antenna elements 2 may be embedded in the multilayer substrate. Alternatively, the multiple antenna elements 2 may be provided on the first or second surface.

[0014] The antenna element 2 is suitable for transmitting and receiving radio waves in high frequency bands (for example, above 1 GHz to 300 GHz) such as microwaves and millimeter waves. The antenna element 2 is applicable to, for example, a V2X communication system, a fifth generation mobile communication system (so-called 5G), an in-vehicle radar system, etc., but is not limited to these. The frequency band may be, for example, for ITS (Intelligent Transport Systems) (5.89 GHz), 5G (28 GHz band, 3.6 to 6 GHz band, 39 GHz band), or Wi-Fi (2.4 GHz, 5 GHz).

[0015] Next, with reference to FIGS. 2 to 4, an example of the arrangement of the antenna element 2 and the like on the strip-shaped member 1 will be described.

[0016] Fig. 2 is a diagram showing an example of the arrangement of multiple antenna elements branch-connected to a transmission line. The strip-shaped member 1 shown in Fig. 2 is provided with a transmission line 3, which is a first transmission line; an antenna element 2 arranged on the transmission line 3 (for example, at the tip of the transmission line 3); one or more transmission lines 3a, which are second transmission lines branching off from the transmission line 3; and an antenna element 2 arranged on the transmission line 3a (for example, at the tip of the transmission line 3a). In this way, providing antenna elements 2 on multiple transmission lines 3a branching off from one transmission line 3 is called a "branch-connected type." "Branching from the transmission line 3" includes simple branching (with impedance matching) and branching using a combiner or divider such as a Wilkinson coupler.

[0017] The branch-connection type allows multiple antenna elements 2 to be arranged around the transmission line 3 that is linearly wired on the strip-shaped member 1, thereby improving the degree of freedom in the layout of the antenna elements 2. Therefore, for example, by widening the width of the strip-shaped member 1 in the direction perpendicular to the extension direction of the strip-shaped member 1, multiple antenna elements 2 can be arranged in a planar manner using the widened portion. Therefore, the branch-connection type is particularly effective when expanding the coverage area in a planar manner.

[0018] Fig. 3 is a diagram showing an example of the arrangement of antenna elements 2 cascade-connected to a transmission line. The strip-shaped member 1 shown in Fig. 3 is provided with a transmission line 3 and two antenna elements 2 arranged on the transmission line 3 (for example, the tip and other parts of the transmission line 3). Providing multiple antenna elements 2 on one transmission line 3 in this way is called a "cascade connection type."

[0019] The cascade connection type simplifies the structure of the transmission line 3 and also makes it possible to narrow the width of the strip-shaped member 1 in the direction perpendicular to the extension direction of the transmission line 3. Therefore, it is particularly effective in expanding the coverage area linearly without making the distributed antenna 20 noticeable to the user of the mobile terminal.

[0020] Fig. 4 is a diagram showing an example of the arrangement of a signal processing circuit arranged on a transmission line. The strip-shaped member 1 shown in Fig. 4 is provided with a transmission line 3, an antenna element 2 arranged on the transmission line 3 (for example, at the tip of the transmission line 3), a transmission line 3a branching off from the transmission line 3, the antenna element 2 arranged, for example, on the transmission line 3a (for example, at the tip of the transmission line 3a), and a signal processing circuit 4 provided, for example, on the transmission line 3.

[0021] 4, one of the two signal processing circuits 4 is provided on the transmission line 3, and the other is provided at a location where the transmission line 3a branches off from the transmission line 3. The location of the signal processing circuit 4 is not limited to the location shown in the figure, and may be, for example, in the middle of the transmission line 3a, near the transmission line 3, or near the transmission line 3a. The number of signal processing circuits 4 is not limited to two, and can be changed as appropriate depending on the application and specifications of the distributed antenna 20.

[0022] 4 illustrates a plurality of branch-connected antenna elements 2. By providing a signal processing circuit 4 having, for example, an AMP (Amplifier), a switch, a mixer, a DAC (Digital to Analog Converter), an ADC (Analog to Digital Converter), etc. near these antenna elements 2, it is possible to compensate for millimeter waves and the like, which have a large signal transmission loss. Note that the same effect can be obtained when a signal processing circuit 4 having any (part of) an AMP, a switch, a mixer, a DAC, or an ADC is provided near the antenna elements 2. Details of the AMP, switch, mixer, DAC, ADC, etc. will be described later.

[0023] Next, with reference to FIGS. 5 and 6, a configuration example of the belt-shaped member 1 in which a flexible core member and a rigid core member are combined will be described.

[0024] FIG. 5 shows an example of the configuration of a strip-shaped member 1 in which a rigid portion 1B is fixed (laminated) to a flexible portion 1A, and FIG. 6 shows an example of the configuration of a strip-shaped member 1 in which the flexible portion 1A and a rigid portion 1B provided at a position away from the flexible portion 1A are connected by a connector 1C or the like. The flexible portion 1A has a core portion 1b, which is, for example, a plate-shaped dielectric layer, and conductive portions 1a, which are conductive members (e.g., copper foil) provided on the upper and lower surfaces of the core portion 1b. Of the two conductive portions 1a, one conductive portion 1a is provided on a first surface 1b1, which is one surface of the core portion 1b, and the other conductive portion 1a is provided on a second surface 1b2, opposite the first surface 1b1, of the core portion 1b. The transmission line 3 is provided on either the first surface 1b1 or the second surface 1b2, or is provided between the first surface 1b1 and the second surface 1b2. The antenna elements 2 are electrically connected to the transmission line 3 and are distributed on either the first surface 1b1 or the second surface 1b2. The configuration of the flexible portion 1A is not limited to this, and may be multi-layered, for example, using two or more dielectric layers and two or more conductive members.

[0025] These strip-shaped members 1 are made of, for example, rigid-flexible substrates, which combine the advantages of both rigid and flexible substrates, such as ease of component mounting and three-dimensional configuration by bending. Rigid-flexible substrates include, for example, a rigid portion 1B, which is a rigid core member on which components are mounted, and a flexible portion 1A, which is a flexible member (flexible core member) that has flexibility.

[0026] 5 has a structure in which a rigid portion 1B is laminated on a flexible portion 1A. In this case, it is preferable that the dimensions of the rigid portion 1B are large enough not to impair the flexibility of the flexible portion 1A.

[0027] 6 has a structure in which, for example, a rigid portion 1B is disposed between two separated flexible portions 1A, and the flexible portion 1A and the rigid portion 1B are electrically connected using a connector 1C and a jumper wire 1D. Note that part of the flexible portion 1A may also serve as the jumper wire 1D.

[0028] Next, an example of a distributed arrangement of multiple antenna elements 2 will be described with reference to Fig. 7. Fig. 7 is a diagram for explaining an example of a distributed arrangement of multiple antenna elements. Fig. 7 shows a cross section of a building wall 100 and distributed antennas 20 installed on the surface of the building wall 100. If the distributed antennas 20 have flexible strip-shaped members 1, even if there are protruding portions 201 on the surface of the building wall 100, the strip-shaped members 1 can be installed along the surface of the protruding portions 201. Furthermore, the distributed antennas 20 can also be installed at the boundary between the surface of the building wall 100 that does not have the protruding portions 201 (flat surface 202) and the protruding portions 201, with the gap minimized.

[0029] The distributed antennas 20 may be fixed to the wall 100 using, for example, adhesive or fastening members such as bolts and nuts. Alternatively, the distributed antennas 20 may be attached to the wall 100 by hooking them onto a hook-shaped member protruding from the wall 100. This allows for easy installation of the distributed antennas 20. For example, the distributed antennas 20 may be installed on the wall 100 of a building only during an irregular event and then removed after the event. Therefore, the distributed antennas 20 can be used on an on-demand basis without being permanently installed. Conventional distributed antennas require individual antennas to be individually installed on walls or other surfaces when installed at an event venue, which requires complicated installation work and requires the installation of separate transmission lines connected to the antennas. Therefore, when using millimeter wave radio waves, expanding the coverage area requires a significant amount of man-hours and effort, and also requires a significant amount of work time to remove the antennas after the event. In contrast, with the distributed antenna 20 according to this embodiment, multiple antenna elements 2, transmission lines 3, etc. are mounted on a strip-shaped dielectric material, so the coverage area can be easily expanded simply by attaching the strip-shaped member 1 to the wall 100 of a building and connecting it to the base station 10. In addition, the strip-shaped member 1 can be collected simply by removing it, which also makes it easy to restore the original state after the event is over.

[0030] Next, a configuration example of the signal processing circuit 4 will be described with reference to FIGS. 8 and 9. FIG. 8 is a diagram showing a configuration example of the signal processing circuit 4. In the diagram, "Digital" refers to a transmission line for a digital signal. "DC" refers to, for example, a wiring for supplying direct current power. The signal processing circuit 4 includes, for example, a DAC 401, which is a converter that converts a digital signal transmitted from the base station 10 into an analog signal and outputs the signal to a mixer 403, a local oscillator 402, which is a local signal source, and a mixer 403, which is an upconverter that upconverts the signal from the DAC 401 using the local signal from the local oscillator 402. The signal processing circuit 4 also includes a power amplifier 404, which is a signal amplifier that amplifies the signal output from the mixer 403 and inputs it to the antenna element 2 via a switch 405 and a directional coupler 406, a switch 405, and a directional coupler 406, which are means for selecting between transmission and reception of the signal processing circuit 4. The signal processing circuit 4 also includes a low-noise amplifier 407 that amplifies the signal received by the antenna element 2 and inputs it to a mixer 409 via a switch 408, and a switch 408 that is a means for selecting a path for monitoring and feeding back the received and transmitted signals and receiving a communication signal. The signal processing circuit 4 also includes a mixer 409 that is a down-converter that down-converts the signal from the low-noise amplifier 407, and an ADC 410 that is a converter that converts the analog signal transmitted from the mixer 409 into a digital signal and transmits it to, for example, the base station 10.

[0031] According to the signal processing circuit 4, by providing the DAC 401 and the ADC 410, communication by digital signals is possible between the base station 10 and the signal processing circuit 4, thereby suppressing signal degradation. Therefore, the communicable distance from the base station 10 to the signal processing circuit 4 can be relatively long, and multiple antenna elements 2 can be distributed and arranged in locations far from the base station 10.

[0032] Furthermore, signal processing circuit 4, for example, by including mixer 403 and mixer 409, can handle signals transmitted between base station 10 and signal processing circuit 4 at low frequencies, thereby reducing transmission loss between base station 10 and signal processing circuit 4. Therefore, the communicable distance from base station 10 to signal processing circuit 4 can be increased, and multiple antenna elements 2 can be distributed and arranged in locations remote from base station 10.

[0033] In this way, by combining DAC 401 and ADC 410 with mixer 403 and mixer 409, for example, base station 10 can be installed in an equipment room such as a stadium, and communication line 30 can be laid from there to the stadium's spectator seats over a distance of several tens to several hundred meters, allowing signals to be transmitted to distributed antennas 20 installed in the stadium's spectator seats. As a result, wireless communication using, for example, millimeter waves becomes possible between multiple mobile terminals present in the spectator seats. Furthermore, even if multiple mobile terminals are present scattered across a range of several tens of meters in the spectator seats of a stadium, for example, signal processing circuit 4 can be used to compensate for the wireless communication level and enable wireless communication over such a wide range.

[0034] The signal processing circuit 4 includes the mixer 403, the mixer 409, the DAC 401, the ADC 410, etc., but may include only the mixer 403 and the mixer 409, or may include only the DAC 401 and the ADC 410. Even in this case, the communicable distance from the base station 10 to the signal processing circuit 4 can be extended, and the configuration of the signal processing circuit 4 is simplified, resulting in improved reliability.

[0035] Next, with reference to FIGS. 9 and 10, an example in which a plurality of signal processing circuits 4 are provided for one strip-shaped member 1 will be described.

[0036] FIG. 9 is a diagram illustrating an example of a connection between an amplifier module including multiple signal processing circuits and multiple antenna elements connected to the amplifier module. The amplifier module 400 shown in FIG. 9 includes, for example, four signal processing circuits 4, each of which is connected to an antenna element 2 via a transmission line 3. The number of signal processing circuits 4 included in the amplifier module 400 is not limited to four. Furthermore, when the amplifier module 400 includes two or more signal processing circuits 4, the signal processing circuits 4 can be realized by arranging the signal processing circuits 4 in parallel, as shown in FIG. 9. Although the module including multiple signal processing circuits 4 is referred to as the amplifier module 400 in FIG. 9, the signal processing circuit 4 itself may also be referred to as the amplifier module 400. Therefore, one signal processing circuit 4 may also be referred to as the amplifier module 400.

[0037] 10 is a diagram showing an example in which an amplifier module is provided on a strip-shaped member. By providing the amplifier module 400 on the strip-shaped member 1, the low-noise amplifier 407 and power amplifier 404 of the signal processing circuit 4 compensate for signal transmission loss due to the transmission line 3. This allows the distance from the amplifier module 400 to the multiple antenna elements 2 to be significantly extended. Note that the amplifier module 400 shown in FIG. 10 may be configured to include, among the functions of the signal processing circuit 4, the low-noise amplifier 407, the power amplifier 404, the switch 405, the directional coupler 406, and the like.

[0038] Note that if the amplifier module 400 is provided in a location other than the strip-shaped member 1, the amplifier module 400 needs to be connected to the antenna element 2, but according to the configuration example shown in Fig. 10, this work is unnecessary, facilitating the installation of the distributed antenna 20 and preventing the occurrence of wiring connection errors by workers, thereby suppressing degradation of communication quality. Furthermore, according to the configuration example shown in Fig. 10, for example, the low-noise amplifier 407 can be placed near the antenna element 2, thereby suppressing signal degradation due to transmission loss from the antenna element 2 to the low-noise amplifier 407.

[0039] Furthermore, compared to when the amplifier module 400 is provided in a location other than the strip-shaped member 1, the design of the distributed antenna 20 itself is improved, and the number of locations where the distributed antenna 20 can be used is increased without impairing the design of buildings or the like.

[0040] Furthermore, by providing the amplifier module 400 on the strip-shaped member 1, heat generated by the low-noise amplifier 407, power amplifier 404, etc. is transferred to the transmission line 3 and strip-shaped member 1, so that the transmission line 3 and strip-shaped member 1 function as a heat sink. This prevents damage to the amplifier module 400 due to heat. Furthermore, by providing the amplifier module 400 on the strip-shaped member 1, even if a heat dissipation component (such as a fin) is installed in an inconspicuous location on a wall, the transmission line 3 and strip-shaped member 1 can be used as a heat conduction path for transferring heat generated by the power amplifier 404, etc. to the heat dissipation component.

[0041] Power wiring (e.g., wiring for supplying DC power) for supplying power for driving the amplifier modules 400 or the signal processing circuits 4 may be laid on the strip-shaped member 1. This eliminates the need to lay power wiring separately from the strip-shaped member 1, and can significantly reduce the installation time even when installing distributed antennas 20 over a wide area, while preventing deterioration in the appearance of the distributed antennas 20.

[0042] FIG. 11 is a diagram for explaining the communication distance when no low-noise amplifier is provided. FIG. 12 is a diagram for explaining the communication distance when a low-noise amplifier is provided. FIG. 13 is a diagram showing an example of a configuration in which the communication distance is extended by providing multiple low-noise amplifiers. The horizontal axis of FIG. 11, FIG. 12 and FIG. 13 represents the distance from the mobile terminal, and the vertical axis of FIG. 11, FIG. 12 and FIG. 13 represents the power output from each device. The dashed line represents the signal level, and the solid line represents the noise level. The conditions under which this data was obtained are as follows: (Conditions) LNA in Figures 11 and 12: Gain = 15 dB / NF = 4 dB First stage LNA in Figure 13: Gain = 45 dB / NF = 6 dB Second and subsequent LNAs in Figure 13: Gain = 30 dB / NF = 5 dB Mobile Power: 20dBm Antenna Gain: 12dBi Distance to Tx: 5m Feeder loss: 30dB / m Mixer: Gain = 10 dB / NF = 15 dB SN ratio after mixer: 10dB

[0043] As shown in FIG. 11, without low-noise amplifier 407, when the signal level is low and the distance from the mobile terminal to antenna element 2 is 5 m, the transmission distance from antenna element 2 to mixer 409 in the receiving system is only approximately 0.8 m. The same is true for the transmitting system. In contrast, when low-noise amplifier 407 is provided, as shown in FIG. 12, the signal level is high and when the distance from the mobile terminal to antenna element 2 is 5 m, the transmission distance from antenna element 2 to mixer 409 in the receiving system is approximately 1.35 m. This is also true for the transmitting system, so the transmission distance from mixer 403 to antenna element 2 can be extended. Furthermore, as shown in FIG. 13, the communication distance can be extended by providing multiple low-noise amplifiers. Note that signal processing circuit 4 may include only low-noise amplifier 407, or may include only low-noise amplifier 407 and power amplifier 404. Note that the communication circuit 30 may be configured to further ensure the transmission distance by using low-loss components such as a waveguide or optical fiber via an optical-electrical converter. In the case where only the low noise amplifier 407 and the power amplifier 404 are provided, it is preferable to use a low loss communication circuit, since this can further increase the communication distance.

[0044] Next, examples of the arrangement of antenna elements in the branch connection type and the cascade connection type will be described with reference to FIGS.

[0045] Figure 14 is a diagram showing a branch-connected distributed antenna. A branch-connected distributed antenna 20 has the advantage of high communication efficiency, since it can select the optimal antenna element 2 for communication with nearby mobile terminals by utilizing the switch function of the signal processing circuit 4. Note that if a combiner / divider such as a Wilkinson coupler is used, it is not possible to select the optimal antenna element 2, but the configuration can be simplified.

[0046] Fig. 15 is a diagram showing a cascade-connected distributed antenna. The cascade-connected distributed antenna 20 has the advantage of being simple in configuration and highly reliable, since it can communicate with nearby mobile terminals without using the switch function of the signal processing circuit 4.

[0047] Figure 16 is an enlarged view of a branch-connected distributed antenna. Figure 17 is a diagram illustrating an example of a branch-connected distributed antenna installed on the ceiling surface inside a station. As shown in Figure 17, by placing a branch-connected distributed antenna 20 on the wall surface that forms a recess in the ceiling of a station platform, for example, it is possible to provide antenna element 2 at the tip of transmission line 3 that branches off downward from strip-shaped member 1. This allows the distance between antenna element 2 and the mobile terminals held by passengers waiting for trains on the station platform to be as close as possible, increasing the electric field strength and improving communication quality.

[0048] Figure 18 is a diagram illustrating an example of installing a cascade-connected distributed antenna on the ceiling surface inside a station. As shown in Figure 18, by placing a cascade-connected distributed antenna 20 on the wall surface that forms a recess in the ceiling of a station platform, for example, the width of the strip-shaped member 1 in the direction perpendicular to the extension direction of the transmission line 3 can be narrowed, thereby expanding the coverage area without compromising the design of the station.

[0049] Next, a modified example of the signal processing circuit will be described with reference to Fig. 19. Fig. 19 is a diagram for explaining a modified example of the signal processing circuit. Fig. 19 shows an example in which the signal processing circuit 4 is configured with multiple circuit boards, and each circuit board is installed on the wall 100 of a building on or near the transmission line 3. The number of multiple circuit boards is not limited to the illustrated example (three), and may be two or more. In this way, by configuring the signal processing circuit 4 with multiple circuit boards, the signal processing circuit 4 can be installed according to the shape of the location where the distributed antenna 20 is to be installed, and therefore the number of places where the distributed antenna 20 can be used can be increased without impairing the design of the building or the like.

[0050] Next, a shielding member that covers the surface of the signal processing circuit 4, the strip-shaped member 1, and the like of the distributed antenna 20 will be described with reference to FIGS. 20 and 21. FIG. 20 is a diagram showing a first modified strip-shaped member. FIG. 20 shows a shielding member 40 that covers the entire surface of the strip-shaped member 1, which is formed, for example, from a flexible substrate. FIG. 21 is a diagram showing a second modified strip-shaped member. FIG. 21 shows a shielding member 40 that covers the entire surface of the strip-shaped member 1, which combines a flexible core member and a rigid core member. The shielding member 40 covers the entire surface of the strip-shaped member 1, including the signal processing circuit 4, and is made of a metallic or non-metallic material with excellent thermal conductivity. Examples of materials for the shielding member 40 include a highly thermally conductive resin compound, a carbon sheet, solder, and an Ag-Cu sintered compact, as shown in (1) to (4) below. However, the material for the shielding member 40 is not limited to these.

[0051] (1) A high thermal conductivity resin compound in which a thermally conductive filler is added to a polymer component. The polymer component is polysiloxane (silicone polymer), polyacrylic, polyolefin, etc. Note that the manufacturing method of the high thermal conductivity resin compound is publicly known, as disclosed in, for example, Japanese Patent No. 5089908 and Japanese Patent No. 5085050, and therefore a detailed description thereof will be omitted.

[0052] (2) Carbon sheets formed from carbon fiber or composite materials of carbon fiber and carbon. Carbon sheets have recently become popular due to the increasing production of products using carbon fiber. Because technologies for mass production in a short time are being established, carbon sheets can also be classified as a relatively low-thermal conductivity and inexpensive material. Furthermore, even though carbon sheets have a higher material cost than solder, Ag-Cu sintering, etc., they do not require a dedicated reflow oven and do not require the processes from heating to cooling, thereby significantly shortening the time required to manufacture distributed antenna 20.

[0053] (3) Solder (such as lead-free solder). Although solder requires the use of a reflow oven or the like, the material cost is low, and therefore when mass-producing distributed antennas 20, it is possible to suppress an increase in the manufacturing cost of each distributed antenna 20 while increasing the thermal conductivity compared to a carbon sheet.

[0054] (4) Ag—Cu sintered body (Ag—Cu alloy containing Cu) The Ag—Cu sintered body is an expensive material because it contains Ag, but has high thermal conductivity and is suitable for dissipating heat from the signal processing circuit 4.

[0055] The shielding member 40 is fixed to the belt-shaped member 1 so as to be in close contact with the surfaces of the signal processing circuit 4 and the belt-shaped member 1. It is desirable that the shielding member 40 be made of a material having a higher thermal conductivity than that of the signal processing circuit 4, for example.

[0056] By providing the shielding member 40, heat generated in the signal processing circuit 4 is transferred to the shielding member 40 and radiated into the air from the surface of the shielding member 40 (the surface opposite the signal processing circuit 4). By providing the shielding member 40 in this way, the number of conduction paths for heat generated in the signal processing circuit 4 is increased, thereby reducing the possibility that the temperature of the signal processing circuit 4 will exceed the allowable temperature. Furthermore, a shield structure is formed that covers the signal processing circuit 4, reducing unwanted radiation and minimizing the impact of noise on devices located around the distributed antenna 20, thereby improving EMC (ElectroMagnetic Compatibility) performance. Even when an electronic device is present near the distributed antenna 20, the shielding member 40 covers the conductive portion 1 a and the signal processing circuit 4, making it less likely for capacitive coupling to occur between the conductive portion 1 a and the electronic device, thereby reducing the impact on the antenna characteristics.

[0057] Next, an example of the configuration of a flexible module will be described with reference to FIG. 22 . FIG. 22 is a diagram illustrating an example of the configuration of a flexible module. The flexible module shown in FIG. 22 is a module combining the aforementioned rigid-flexible substrate with a shielding member 40. As shown in FIG. 22 , the rigid-flexible substrate includes a rigid portion 1B, which is a rigid core member on which components, for example, are mounted, and a flexible portion 1A, which is a bendable, flexible core member. A shielding member 40 is provided to entirely cover the rigid portion 1B and the flexible portion 1A. The rigid-flexible substrate can be provided with a power amplifier 404, a switch 405, and other components that constitute the signal processing circuit 4. By installing such a flexible module on a wall 100 of a building or the like, the signal processing circuit 4 is covered by the shielding member 40, improving EMC performance and increasing the number of locations where the distributed antenna 20 can be used without compromising the design of the building or the like. Note that, when the flexible module is permanently installed, adhesive 60 may be used to secure the flexible module to the wall 100 of a building or the like. When the flexible module is temporarily installed, a cable tie or the like may be used.

[0058] Next, referring to FIG. 23, a configuration example in which the distributed antenna 20 is used as a repeater antenna will be described. FIG. 23 is a diagram showing a configuration example of a distributed antenna for a repeater. The distributed antenna 20 shown in FIG. 23 includes a receiving antenna 51 that receives radio waves transmitted from a transmitting antenna 50 connected to a base station 10. An antenna element 2 installed on the surface of a wall 100 at a location different from the location where the receiving antenna 51 is installed relays (re-radiates) the radio waves received by the receiving antenna 51, for example, in a direction different from the direction from which the radio waves arrived at the receiving antenna 51. This configuration significantly reduces the cost required to build an entrance line from the base station 10 to the distributed antenna 20, even if the distance from the base station 10 to the distributed antenna 20 is long. Naturally, this also applies if the transmission and reception are swapped. The method of using 5G radio waves as an entrance line is standardized as IAB (Integrated Access and Backhaul).

[0059] As described above, the distributed antenna according to this embodiment includes a strip-shaped dielectric member, a transmission line provided on the strip-shaped member, and multiple antenna elements connected to the transmission line and distributed along the strip-shaped member. For example, to ensure good wireless communication among multiple mobile terminals located in spectator seats in a stadium or the like, it is desirable to shorten the distance between the multiple antennas connected to a wireless base station and the mobile terminals. However, in the past, multiple antennas had to be installed on specific structures within the stadium, such as the roof above the seats or the pillars supporting the roof, making it difficult to equalize the distances between the multiple mobile terminals and the multiple antennas. This resulted in issues such as unstable wireless communication quality. Another issue was the risk of reduced reliability in connecting the transmission line to the antenna. According to the distributed antenna according to this embodiment, for example, the strip-shaped member can be placed in the space above the seats in a stadium to bridge them or run along the slope of the seats, thereby expanding the coverage area without affecting the structure or construction of the building. Furthermore, the distributed antenna according to this embodiment includes a signal processing circuit including power amplifier 404, low noise amplifier 407, etc., so that the wireless communication level can be compensated for even if the distance from base station 10 is long.

[0060] (Effects of obstacles on radio wave propagation characteristics) Next, the influence of obstacles on the propagation characteristics of radio waves will be described with reference to Figures 24 to 28. As will be described below, the inventors of the present invention conducted tests to investigate the influence of obstacles on the propagation characteristics of radio waves using conventional antennas 80A and 80B.

[0061] FIG. 24 is a diagram showing the arrangement of antennas 80A, 80B, and a pole 70 in this test. As shown in FIG. 24, the inventors of the present invention arranged conventional antennas 80A and 80B facing each other. Here, the inventors of the present invention set the distance between antennas 80A and 80B to 500 mm. The inventors of the present invention also installed a cylindrical pole 70 as an example of an obstacle midway between antennas 80A and 80B. The inventors of the present invention then conducted a test to examine the effect of the presence or absence of the pole 70 and the diameter of the pole 70 on the propagation characteristics of radio waves transmitted from antenna 80A to antenna 80B.

[0062] FIG. 25 is a diagram showing the configuration of antennas 80A and 80B used in this test. In this test, 28 GHz band patch antennas were used as antennas 80A and 80B. As shown in FIG. 25, antennas 80A and 80B have a substrate 82 and an antenna element 84. As shown in FIG. 25, in this test, substrate 82 was square, and the length of one side of substrate 82 was 10.0 mm. Also, as shown in FIG. 25, in this test, antenna element 84 was square, and the length of one side of antenna element 84 was 2.6 mm.

[0063] Fig. 26 is a diagram showing the antenna characteristics (XY plane directivity) of antennas 80A and 80B used in this test. As shown in Fig. 26, antennas 80A and 80B have strong directivity in the X-axis direction (the direction perpendicular to the surface of antenna element 84). Furthermore, antennas 80A and 80B can obtain a maximum gain of 5.5 dBi in the X-axis direction in the 28 GHz band.

[0064] Fig. 27 is a table showing the measurement results (S21) from this test for each installation condition of the pillar 70. Fig. 28 is a graph showing the measurement results (S21) from this test for each installation condition of the pillar 70. As shown in Figs. 27 and 28, in this test, the transmission coefficient (S21) of radio waves propagating from antenna 80A to antenna 80B was measured for the case where no pillar 70 was installed and for the cases where the diameter of the pillar 70 was 50 mm, 100 mm, and 200 mm.

[0065] As shown in Figures 27 and 28, this test showed that when a pillar 70 was present, the transmission coefficient (S21) of radio waves in the 28 GHz band was -39.6 dB. On the other hand, when a pillar 70 with a diameter of 50 mm was present, the transmission coefficient (S21) of radio waves in the 28 GHz band was -44.4 dB. Furthermore, when a pillar 70 with a diameter of 100 mm was present, the transmission coefficient (S21) of radio waves in the 28 GHz band was -52.8 dB. Furthermore, when a pillar 70 with a diameter of 200 mm was present, the transmission coefficient (S21) of radio waves in the 28 GHz band was -73.7 dB. From these measurement results, this test revealed that the presence of a pillar 70 reduces the value of S21 (i.e., radio waves become more difficult to reach). This test also revealed that the value of S21 decreases (i.e., radio waves become more difficult to reach) as the diameter of the pillar 70 increases.

[0066] That is, this test revealed that when an obstacle such as a pillar is present on the propagation path of radio waves emitted from an antenna, the radio waves have difficulty reaching the area behind the obstacle (blind spot). In particular, millimeter wave radio waves used in 5G and the like have poor ability to penetrate obstacles, making it difficult for the radio waves to reach the area behind the obstacle (blind spot). Therefore, the inventors of the present invention invented the flexible antenna 20A described below with the aim of more reliably transmitting radio waves in each of multiple directions around an obstacle such as a pillar.

[0067] (Flexible Antenna 20A) 29 to 44, a flexible antenna 20A will be described as another example of the distributed antenna 20. The flexible antenna 20A can be installed on a pole 70 (an example of a "pole-shaped installation object") such as a traffic light, a street light, or a utility pole. The flexible antenna 20A can be used, for example, as a 5G antenna for a base station.

[0068] Fig. 29 is a plan view of a flexible antenna 20A according to an embodiment. As shown in Fig. 29, the flexible antenna 20A includes a flexible substrate 26 and a plurality of antennas ANT1 to ANT8.

[0069] The flexible substrate 26 is a flexible sheet-like member. In a plan view, the flexible substrate 26 has a horizontally long rectangular shape. The multiple antennas ANT1 to ANT8 are arranged at equal intervals in the horizontal direction HD on the surface of the flexible substrate 26. Each of the multiple antennas ANT1 to ANT8 has a vertically polarized wave antenna 22A and a horizontally polarized wave antenna 22B.

[0070] Vertically polarized wave antenna 22A has a plurality of antenna elements 2 (eight in the example shown in FIG. 29) arranged side by side in the vertical direction VD, and a transmission line 3 extending linearly in the vertical direction VD. A branch of transmission line 3 is connected at a right angle to the bottom side of each of the plurality of antenna elements 2 that vertically polarized wave antenna 22A has.

[0071] Horizontally polarized wave antenna 22B has a plurality of antenna elements 2 (eight in the example shown in FIG. 29) arranged side by side in the vertical direction VD. It also has a transmission line 3 that extends linearly in the vertical direction VD. A branch of transmission line 3 is connected at a right angle to the left side of each of the plurality of antenna elements 2 that horizontally polarized wave antenna 22B has.

[0072] Each of the plurality of vertically polarized wave antennas 22A and the plurality of horizontally polarized wave antennas 22B has an independent connection port at the lower end of the transmission line 3. This allows the signal processing circuit 4 connected to the flexible antenna 20A to independently use each of the plurality of vertically polarized wave antennas 22A and the plurality of horizontally polarized wave antennas 22B for emitting radio waves via the plurality of connection ports.

[0073] Furthermore, in vertically polarized wave antenna 22A and horizontally polarized wave antenna 22B, the straight portion extending in the vertical direction VD of transmission line 3 has a shape in which the bandwidth gradually narrows toward the tip. This allows vertically polarized wave antenna 22A and horizontally polarized wave antenna 22B to evenly distribute energy supplied from the connection port of transmission line 3 to each of the multiple antenna elements 2 connected to transmission line 3.

[0074] 30 is a diagram illustrating an example of a cross-sectional configuration of a flexible antenna 20A according to an embodiment. In the example illustrated in FIG. 30, the flexible antenna 20A includes a flexible substrate 26, an antenna element 24, a transmission line 25, and a ground layer 27.

[0075] Flexible substrate 26 is a flexible, thin, film-like member made of resin. For example, the thickness of flexible substrate 26 is 1 μm to 300 μm. For example, flexible substrate 26 may be made of a resin material such as fluorine, COP (Cyclo Olefin Polymer), PET (Polyethylene terephthalate), PEN (Polyethylene naphthalate), polyimide, Peek (Polyether ether ketone), LCP (Liquid Crystal Polymer), or other composite materials.

[0076] The antenna element 24 and the transmission line 25 are formed as thin films on the upper surface of the flexible substrate 26. For example, the thickness of the antenna element 24 and the transmission line 25 is 1 nm to 32 μm. Furthermore, for example, the antenna element 24 and the transmission line 25 are formed using a conductive material such as copper.

[0077] The ground layer 27 is formed as a thin film on the lower surface of the flexible substrate 26. For example, the thickness of the ground layer 27 is 1 nm to 32 μm. Furthermore, for example, the ground layer 27 is made of a conductive material such as copper.

[0078] Fig. 31 is a diagram illustrating another example of the cross-sectional configuration of the flexible antenna 20A according to the embodiment. In the example illustrated in Fig. 31, the flexible antenna 20A has a first flexible substrate 26A and a second flexible substrate 26B that overlap each other, instead of the flexible substrate 26 shown in Fig. 30.

[0079] In the example shown in Fig. 31, antenna element 24 is formed on the upper surface of first flexible substrate 26A. Also, in the example shown in Fig. 31, transmission line 25 is formed between first flexible substrate 26A and second flexible substrate 26B. Also, in the example shown in Fig. 31, ground layer 27 is formed on the lower surface of second flexible substrate 26B.

[0080] Fig. 32 is a diagram showing an example of installation of the flexible antenna 20A according to the embodiment on a pillar 70. Fig. 33 is a cross-sectional view of the flexible antenna 20A and the pillar 70 shown in Fig. 32 along the XY plane.

[0081] 32 and 33, flexible antenna 20A is flexible and can be installed by wrapping it around an outer circumferential surface 70A of pole 70. This allows flexible antenna 20A to radiate vertically polarized waves and horizontally polarized waves in each of a plurality of directions (eight directions in the case of the configuration shown in FIG. 29) centered on pole 70 using each of a plurality of antennas ANT1 to ANT8.

[0082] 32 and 33, the multiple antennas ANT1 to ANT8 are arranged at 45° intervals on the outer peripheral surface 70A of the pillar 70. Therefore, the flexible antenna 20A can radiate vertically polarized waves and horizontally polarized waves in eight directions at 45° intervals around the pillar 70 by each of the multiple antennas ANT1 to ANT8.

[0083] As a result, the flexible antenna 20A according to this embodiment can ensure that radio waves reach each of a plurality of directions around the pillar 70 more reliably.

[0084] Furthermore, in the flexible antenna 20A according to the embodiment, each of the multiple antennas ANT1 to ANT8 has an independent connection port, and therefore, the flexible antenna 20A according to the embodiment can radiate radio waves only in the required direction by driving (feeding power to) some of the multiple antennas ANT1 to ANT8 depending on the purpose of use, installation location, etc.

[0085] Furthermore, the flexible antenna 20A according to the embodiment is a thin, flexible sheet, and can be flexibly deformed along the installation surface. Therefore, the flexible antenna 20A according to the embodiment can be installed not only on a cylindrical pole but also on various other columnar installation objects (for example, a rectangular pole, a wall surface bent at a right angle, a wall surface having an uneven shape, etc.) without protruding from the installation surface of the structure.

[0086] The flexible antenna 20A is fixed to the outer peripheral surface 70A of the pillar 70 by any fixing method (for example, adhesive, double-sided tape, etc.). The flexible antenna 20A may also be fixed to the outer peripheral surface 70A of the pillar 70 by closing one end and the other end to form a ring shape.

[0087] In addition, the surface of the flexible antenna 20A may be protected from rainwater, ultraviolet rays, etc. by a protective film, protective cover, etc. before or after it is installed on the outer peripheral surface 70A of the pillar 70.

[0088] Furthermore, when the diameter of the pole 70 on which the flexible antenna 20A is to be installed is determined, it is preferable that the width of the flexible antenna 20A has a length corresponding to the circumferential length of the outer peripheral surface of the pole 70. In this case, when the flexible antenna 20A is installed on the pole 70, one end and the other end in the horizontal direction of the flexible antenna 20A may overlap each other or may be slightly spaced apart. Furthermore, when the flexible antenna 20A is installed on a pole 70 having a predetermined diameter, it is preferable that multiple antennas be arranged at intervals of a predetermined angle (360° ÷ number of antennas) around the pole 70.

[0089] Fig. 34 is a diagram showing a first modified example of the antenna pattern in the flexible antenna 20A according to the embodiment, and Fig. 35 is a diagram showing a second modified example of the antenna pattern in the flexible antenna 20A according to the embodiment.

[0090] 34 and 35, flexible antenna 20A has four antennas arranged side by side at equal intervals in horizontal direction HD on the surface of flexible substrate 26. Each of the four antennas has three antenna elements 2 arranged side by side in vertical direction VD. In each of the four antennas, the three antenna elements 2 are connected in series by a transmission line 3 that extends linearly in the vertical direction VD.

[0091] As a result, when the flexible antenna 20A shown in Figures 34 and 35 is installed on the outer peripheral surface 70A of a pillar 70, it can radiate vertically polarized waves from each of the four antennas in four directions centered around the pillar 70, with three antenna elements 2 per direction. In particular, when the flexible antenna 20A shown in Figures 34 and 35 is installed on the outer peripheral surface 70A of a pillar 70 having a predetermined diameter, it can arrange the four antennas at 90° intervals on the outer peripheral surface 70A. In this case, the flexible antenna 20A shown in Figures 34 and 35 can radiate vertically polarized waves from each of the four antennas in four directions at 90° intervals centered around the pillar 70.

[0092] In the flexible antenna 20A shown in Fig. 35, each of the four antennas has an independent connection port. Therefore, the flexible antenna 20A shown in Fig. 35 can drive each of the four antennas individually as needed, that is, can emit radio waves only in a specific direction. Furthermore, the flexible antenna 20A shown in Fig. 35 can transmit multiple different types of signals simultaneously or with a time lag using the four antennas. For example, the flexible antenna 20A shown in Fig. 35 can also be used for MIMO (multiple-input and multiple-output), beamforming, etc.

[0093] In addition, the flexible antenna 20A shown in Figures 34 and 35 can control the direction of the beam in the vertical direction VD (elevation / depression angle direction) by adjusting the spacing in the vertical direction VD of the antenna elements 2 arranged side by side in the vertical direction VD and adjusting the phase of the power supplied to the antenna elements 2.

[0094] For example, by arranging the antenna elements 2 so that the spacing in the vertical direction VD between them is approximately one wavelength in electrical length in the transmission line 3, i.e., so that they are in phase, the beam direction can be controlled to 0° in the elevation / depression angle direction.

[0095] Furthermore, for example, by arranging the antenna elements 2 so that the spacing in the vertical direction VD between the antenna elements 2 is longer than one wavelength in electrical length in the transmission line 3, that is, so that the phase is delayed, the beam direction can be controlled (uptilted) in the elevation direction.

[0096] Furthermore, for example, by arranging the antenna elements 2 so that the spacing in the vertical direction VD of the antenna elements 2 is shorter than one wavelength in electrical length in the transmission line 3, in other words, so that the phase is advanced, the beam direction can be controlled in the depression angle direction (downtilt).

[0097] This also applies to the flexible antennas 22A and 22B shown in FIGS. 29 and 32, and by adjusting the phase at which power is fed to each of the antenna elements 2, the beam direction in the vertical direction VD can be controlled.

[0098] When the beam direction is controlled to 0° in the elevation angle direction, it is preferable that the spacing in the vertical direction VD be set to 0.96 to 1.04 wavelengths in electrical length in the transmission line 3 .

[0099] Furthermore, when controlling the beam direction in the elevation angle direction (uptilt), it is preferable that the spacing in the vertical direction VD be set to an electrical length in the transmission line 3 of 1.05 wavelengths or more and 1.50 wavelengths or less.

[0100] Furthermore, when controlling the beam direction in the depression angle direction (downtilt), it is preferable that the spacing in the vertical direction VD be set to an electrical length in the transmission line 3 of 0.50 wavelengths or more and 0.95 wavelengths or less.

[0101] On the other hand, the flexible antenna 20A shown in Fig. 34 has one connection port connected to each of the four antennas. Therefore, the flexible antenna 20A shown in Fig. 34 can simultaneously drive each of the four antennas by supplying a drive signal from the signal processing circuit 4 to one connection port, and therefore can simultaneously emit radio waves in each of the four directions.

[0102] FIG. 36 is a diagram showing a third modified example of the antenna pattern of the flexible antenna 20A according to the embodiment.

[0103] In the example shown in Fig. 36, the flexible antenna 20A has four antenna elements 2 arranged side by side in the vertical direction VD at four positions in the horizontal direction HD on the surface of the flexible substrate 26. That is, the flexible antenna 20A shown in Fig. 36 has 16 antenna elements 2 arranged in a 4 × 4 matrix on the surface of the flexible substrate 26. Furthermore, the flexible antenna 20A shown in Fig. 36 has an independent transmission line 3 provided for each of the 16 antenna elements 2. An end of the transmission line 3 bent at a right angle to the horizontal direction HD is connected at a right angle to the left or right side of each of the 16 antenna elements 2.

[0104] As a result, when the flexible antenna 20A shown in Figure 36 is installed on the outer surface 70A of the pillar 70, it can radiate horizontally polarized waves in each of the four directions centered on the pillar 70 using some or all of the four antenna elements 2 in each direction.

[0105] In particular, when the flexible antenna 20A shown in Fig. 36 is installed on the outer peripheral surface 70A of a pillar 70 having a predetermined diameter, four antenna elements 2 can be arranged at 90° intervals on the outer peripheral surface 70A. In this case, the flexible antenna 20A shown in Fig. 36 can radiate horizontally polarized waves in each of four directions at 90° intervals around the pillar 70, using some or all of the four antenna elements 2 per direction.

[0106] In the flexible antenna 20A shown in FIG. 36, each of the 16 antenna elements 2 has an independent connection port. Therefore, the flexible antenna 20A shown in FIG. 36 can drive each of the 16 antenna elements 2 individually as needed. This allows, for example, the flexible antenna 20A shown in FIG. 36 to freely control the direction of beamforming in both the vertical and horizontal directions using any number of antenna elements 2. Furthermore, for example, the flexible antenna 20A shown in FIG. 36 can transmit multiple different types of signals simultaneously or with a time lag using any number of antenna elements 2.

[0107] Figure 37 is a diagram showing a first example of the antenna characteristics of the flexible antenna 20A according to the embodiment. Figure 37 shows the antenna characteristics in the 28 GHz band of each of eight antennas on the XY plane when the flexible antenna 20A (vertical width 100 mm, horizontal width 430 mm) according to the embodiment is installed on the outer peripheral surface 70A of a pillar 70 (diameter 140 mm) and eight antennas are provided on the flexible antenna 20A at 45° intervals. Note that Figure 37A shows the antenna characteristics of the vertically polarized antenna 22A. Also, Figure 37B shows the antenna characteristics of the horizontally polarized antenna 22B.

[0108] As shown in FIG. 37A, the flexible antenna 20A of the embodiment can radiate vertically polarized waves with sufficient gain (maximum gain 12.5 dBi) in each of eight directions spaced at 45° intervals around the pillar 70 using eight antennas.

[0109] Furthermore, as shown in FIG. 37B, the flexible antenna 20A according to the embodiment can radiate horizontally polarized waves with sufficient gain (maximum gain 10.4 dBi) in each of eight directions spaced at 45° intervals around the pillar 70 using eight antennas.

[0110] Figure 38 is a diagram showing a second example of the antenna characteristics of the flexible antenna 20A according to the embodiment. Figure 38 shows the antenna characteristics in the 28 GHz band of each of six antennas on the XY plane when the flexible antenna 20A (vertical width 100 mm, horizontal width 430 mm) according to the embodiment is installed on the outer peripheral surface 70A of a pillar 70 (diameter 140 mm) and six antennas are provided on the flexible antenna 20A at 60° intervals. Note that Figure 38A shows the antenna characteristics of the vertically polarized antenna 22A. Also, Figure 38B shows the antenna characteristics of the horizontally polarized antenna 22B.

[0111] As shown in FIG. 38A, the flexible antenna 20A according to the embodiment can radiate vertically polarized waves with sufficient gain (maximum gain 12.5 dBi) in each of six directions spaced at 60° intervals around the pillar 70 using six antennas.

[0112] Furthermore, as shown in FIG. 38B, the flexible antenna 20A according to the embodiment can radiate horizontally polarized waves with sufficient gain (maximum gain 10.4 dBi) in each of six directions spaced at 60° intervals around the pillar 70 using six antennas.

[0113] Figure 39 is a diagram showing a third example of the antenna characteristics of the flexible antenna 20A according to the embodiment. Figure 39 shows the antenna characteristics in the 28 GHz band of each of the four antennas on the XY plane when the flexible antenna 20A (vertical width 100 mm, horizontal width 430 mm) according to the embodiment is installed on the outer peripheral surface 70A of a pillar 70 (diameter 140 mm) and the four antennas are provided at 90° intervals on the flexible antenna 20A. Note that Figure 39A shows the antenna characteristics of the vertically polarized antenna 22A. Also, Figure 39B shows the antenna characteristics of the horizontally polarized antenna 22B.

[0114] As shown in FIG. 39A, the flexible antenna 20A of the embodiment can radiate vertically polarized waves with sufficient gain (maximum gain 12.5 dBi) in each of four directions spaced 90° apart from each other around the pillar 70 using four antennas.

[0115] Furthermore, as shown in FIG. 39B, the flexible antenna 20A according to the embodiment can radiate horizontally polarized waves with sufficient gain (maximum gain 10.4 dBi) in each of four directions spaced at 90° intervals around the pillar 70 using four antennas.

[0116] Fig. 40 is a diagram showing a fourth example of the antenna characteristics of the flexible antenna 20A according to the embodiment. Fig. 40 shows the antenna characteristics in the 28 GHz band of each of three antennas on the XY plane when the flexible antenna 20A (vertical width 100 mm, horizontal width 430 mm) according to the embodiment is installed on the outer peripheral surface 70A of a pillar 70 (diameter 140 mm) and the three antennas are provided on the flexible antenna 20A at 120° intervals. Fig. 40A shows the antenna characteristics of the vertically polarized antenna 22A. Fig. 40B shows the antenna characteristics of the horizontally polarized antenna 22B.

[0117] As shown in FIG. 40A, the flexible antenna 20A according to the embodiment can radiate vertically polarized waves with sufficient gain (maximum gain 12.5 dBi) in each of three directions spaced 120° apart from each other around the pillar 70 using three antennas.

[0118] Furthermore, as shown in FIG. 40B, the flexible antenna 20A according to the embodiment can radiate horizontally polarized waves with sufficient gain (maximum gain 10.4 dBi) in each of three directions spaced 120° apart from each other around the pillar 70 using three antennas.

[0119] Fig. 41 is a diagram showing a fifth example of the antenna characteristics of the flexible antenna 20A according to the embodiment. Fig. 41 shows the antenna characteristics in the 28 GHz band of each of two antennas on the XY plane when the flexible antenna 20A (vertical width 100 mm, horizontal width 430 mm) according to the embodiment is installed on the outer peripheral surface 70A of a pillar 70 (diameter 140 mm) and the two antennas are provided on the flexible antenna 20A at an interval of 180°. Fig. 41A shows the antenna characteristics of the vertically polarized antenna 22A. Fig. 41B shows the antenna characteristics of the horizontally polarized antenna 22B.

[0120] As shown in FIG. 41A, the flexible antenna 20A according to the embodiment can radiate vertically polarized waves with sufficient gain (maximum gain 12.5 dBi) in each of two directions spaced 180° apart from each other around the pillar 70 using two antennas.

[0121] Furthermore, as shown in FIG. 41B, according to the flexible antenna 20A of the embodiment, the two antennas can radiate horizontally polarized waves with sufficient gain (maximum gain 10.4 dBi) in each of two directions spaced 180° apart from each other around the pillar 70.

[0122] Due to the antenna characteristics shown in Figures 37 to 41, the flexible antenna 20A according to the embodiment preferably has at least two antennas, and more preferably has three or more antennas, in order to cover all directions around the pillar 70.

[0123] Fig. 42 is a diagram showing a fourth modified example of the antenna pattern of the flexible antenna 20A according to the embodiment. Fig. 43 is a diagram showing an example of installation of the flexible antenna 20A shown in Fig. 42 on a pole 70.

[0124] 42 and 43, the flexible antenna 20A has one antenna ANT1 extending in the horizontal direction HD on the surface of the flexible substrate 26. The antenna ANT1 has eight antenna elements 2 arranged side by side in the horizontal direction HD. In the antenna ANT1, the eight antenna elements 2 are connected in series by a transmission line 3 extending linearly in the horizontal direction HD.

[0125] As a result, when the flexible antenna 20A shown in Figures 42 and 43 is installed on the outer surface 70A of a pillar 70 as shown in Figure 43, each of the eight antenna elements 2 can radiate horizontally polarized waves in each of eight directions centered on the pillar 70.

[0126] In particular, the flexible antenna 20A shown in Figures 42 and 43 has one connection port connected to each of the eight antenna elements 2. Therefore, the flexible antenna 20A shown in Figures 42 and 43 can simultaneously drive each of the eight antenna elements 2 by supplying a drive signal from the signal processing circuit 4 to the one connection port, and therefore can simultaneously radiate horizontally polarized waves in each of the eight directions.

[0127] Figure 44 is a diagram showing an example of the antenna characteristics of the flexible antenna 20A shown in Figure 42. Figure 44A shows the antenna characteristics of antenna ANT1 in the 28 GHz band in the YX plane of the flexible antenna 20A (vertical width 15 mm, horizontal width 60 mm) shown in Figure 42 alone. Figure 44B shows the antenna characteristics of antenna ANT1 in the 28 GHz band in the YX plane when the flexible antenna 20A (vertical width 15 mm, horizontal width 60 mm) shown in Figure 42 is installed on the outer peripheral surface 70A of a pillar 70 (diameter 25 mm).

[0128] As shown in Figure 44B, according to the flexible antenna 20A shown in Figure 42, the antenna ANT1 having eight antenna elements 2 can radiate horizontally polarized waves with sufficient gain (maximum gain 1 dBi) in each of eight directions centered on the pillar 70.

[0129] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies, and parts of the configurations may be omitted or modified within the scope of the gist of the present disclosure.

[0130] This international application claims priority to Japanese Patent Application No. 2019-201844, filed November 6, 2019, Japanese Patent Application No. 2019-225319, filed December 13, 2019, and Japanese Patent Application No. 2020-007983, filed January 22, 2020, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0131] 1: Belt-shaped member 1b1 :1st side 1b2 :Second side 1A: Flexible section 1B: Rigid part 1a: Conductive part 1b: Core part 2: Antenna element 3, 3a: Transmission line 4: Signal processing circuit 10:Base station 11: Fin base 20: Distributed antenna 30: Communication line 40: Shielding material 50: Transmitting antenna 51: Receiving antenna 60: Adhesive part 100: Wall 201: Convex part 202 :Flat surface 300: Distributed Antenna System 400: Amplifier module 402: Local oscillator 403: Mixer 404: Power amplifier 405: Switch 406 :Directional coupler 407: Low noise amplifier 408: Switch 409: Mixer 20A: Flexible antenna ANT1~ANT8: Antennas 22A: Vertically polarized antenna 22B: Horizontally polarized antenna 24: Antenna element 25: Transmission line 26: Flexible substrate 26A: First flexible substrate 26B: Second flexible substrate 27: Ground layer 70: Pillar 70A: Outer surface 80A, 80B: Antenna 82: Circuit board 84: Antenna element

Claims

1. a strip-shaped member having a plate-shaped dielectric, a first surface which is one surface of the dielectric, and a second surface opposite to the first surface, the strip-shaped member extending in a strip shape; a transmission line provided on either the first surface or the second surface, or provided between the first surface and the second surface; a plurality of antenna elements electrically connected to the transmission line and distributed on either the first surface or the second surface, or electrically connected to the transmission line and distributed between the first surface and the second surface; a signal processing circuit provided on the belt-shaped member for processing a signal transmitted to the transmission line; a power wiring provided on the belt-shaped member for supplying power for driving the signal processing circuit; Equipped with The signal processing circuit includes an amplifier that amplifies a signal transmitted through the transmission line; a mixer that up-converts or down-converts a signal transmitted on the transmission line; and the amplifier is located between the mixer and the antenna element; a transmission distance from the antenna element to the mixer is greater than 0.8 m; The belt-shaped member has a flexible member having flexibility. Distributed antenna.

2. The transmission line is a first transmission line and a second transmission line branching from the first transmission line; The distributed antenna according to claim 1 , wherein the antenna elements are connected to the second transmission line.

3. The distributed antenna according to claim 1 , wherein the antenna elements are provided on the transmission line.

4. 4. The distributed antenna according to claim 1, wherein the strip-shaped member has a flexible member having flexibility and a rigid core member.

5. 5. The distributed antenna according to claim 4, wherein a signal processing circuit for processing signals transmitted through the transmission line is provided on the rigid core member and / or the flexible member.

6. the belt-shaped member has a flexible member having flexibility and a rigid core member, the core member is provided at a position spaced apart from the flexible member, The distributed antenna according to claim 1 , wherein the flexible member and the core member are connected by a connector.

7. 7. The distributed antenna according to claim 1, further comprising a signal processing circuit provided on the band-shaped member, the signal processing circuit having a DAC which is a converter that converts a digital signal transmitted from a base station into an analog signal and transmits the analog signal to the mixer, and an ADC which is a converter that converts an analog signal transmitted from the mixer into a digital signal and transmits the digital signal to the base station.

8. 8. The distributed antenna according to claim 1, wherein the signal processing circuit is provided on the strip-shaped member and has a local oscillator that is a local signal source for a mixer.

9. The distributed antenna according to claim 1 , further comprising: a member that covers at least the signal processing circuit.

10. 10. The distributed antenna according to claim 1, wherein the signal processing circuit has two or more functions for processing signals transmitted to the transmission line, and is configured by a plurality of circuit boards each having one of the two or more functions.

11. A receiving antenna is provided to receive radio waves transmitted from a base station, The distributed antenna according to claim 1 , wherein the antenna element relays the radio wave received by the receiving antenna to a location different from a location where the receiving antenna is located.

12. The distributed antenna according to claim 1 , further comprising a member covering the transmission line.

13. The plurality of antenna elements are arranged side by side in a horizontal direction on the surface of the strip-shaped member, and the transmission line is a single transmission line connected to each of the plurality of antenna elements.

2. The distributed antenna according to claim 1 .

14. The distributed antenna according to claim 13, wherein the plurality of antenna elements are arranged at equal intervals in the horizontal direction.

15. the plurality of antenna elements are arranged in a matrix on the surface of the strip-shaped member, aligned in both the horizontal and vertical directions; The transmission line is a plurality of transmission lines provided for each of the plurality of antenna elements.

2. The distributed antenna according to claim 1 .

16. A base station; A distributed antenna according to any one of claims 1 to 15; Communication lines and Equipped with The base station is connected to the distributed antenna via the communication line.

1. An antenna system comprising:

17. a plurality of amplifiers configured to amplify signals transmitted on the transmission line; The plurality of amplifiers are arranged in series between each of the plurality of antenna elements and the mixer. A distributed antenna according to any one of claims 1 to 15.

Images