JP7829176B2 - Unpowered relay device - Google Patents

Description

This invention relates to a powerless relay device that increases communication capacity and communication distance in communication between a terminal such as a mobile phone and a base station.

Generally, to increase communication capacity and range between mobile phone terminals and base stations, measures such as increasing the output power of base stations (including fiber optic networks) and denser installation (inside and outside buildings) have been implemented. Furthermore, in certain types of communication, unpowered reflectors or large unpowered relay devices are installed on mountain slopes or on top of transmission towers, etc., instead of base stations, considering installation costs.

In communication between terminals and base stations, increasing the output power of the base station, or increasing the facilities of the base station itself, presents challenges such as increased communication costs, energy waste, and unwanted electromagnetic radiation. Conventionally, unpowered relay devices using dipole antennas, loop antennas, patch antennas, and Yagi antennas have been proposed.

For example, Patent Document 1 describes a dual antenna device in which a receiving antenna has an aperture area perpendicular to the incident wave, a transmitting antenna with a reflector and an aperture area parallel to the reflection direction (transmission direction), and the transmitting and receiving antennas share some structural parts and are arranged in the same plane.

Japanese Patent Publication No. 2013-197758

However, the following challenges remain with the conventional technologies described above.
In recent years, with 5G millimeter waves, there has been a demand to improve communication quality in blind spots (radio dead zones) such as between buildings, due to increased free-space attenuation and narrower beams. In particular, as 5G millimeter waves spread, antennas (passive relay devices) for DAS (Distributed Antenna System), which relay radio waves from base stations via optical fiber and transmit and receive signals from multiple antennas installed on ceilings, etc., are being considered as a countermeasure against indoor dead zones. Therefore, two-directional radiation is required in T-junctions and crossroads such as corridors, which are prone to becoming indoor radio dead zones.
However, the technology described in Patent Document 1 only covers one direction, requiring the installation of two units to cover two directions, which increases the number of antennas to be installed. In addition, the patch antenna area and the Yagi antenna area are separated, resulting in the disadvantage of a larger overall antenna area.

This invention has been made in view of the aforementioned problems, and aims to provide a powerless relay device that can achieve specific directivity, suppress unwanted radiation, be miniaturized and low-profile, and can radiate in two directions with a single unit.

To solve the aforementioned problems, the present invention employs the following configuration. Specifically, the unpowered relay device according to the first invention comprises a rectangular cross-section antenna body formed of a conductive material, having a pair of openings at both ends, and comprising a top plate portion and a bottom plate portion facing each other vertically, and a pair of side wall portions facing each other horizontally. The top plate portion is characterized by having a slot-shaped through-hole extending along the opening direction of the openings.

In this unpowered relay device, the top plate has slot-shaped through-holes that extend along the direction of the opening. Therefore, when, for example, a vertically polarized incident wave is input from the front of the top plate through the slot-shaped through-holes, the pair of openings in the antenna body, which functions as a band-shaped loop antenna, can re-radiate horizontally polarized transmitted waves toward the openings on both sides. In this way, a receiving slot antenna is configured in the top plate of the antenna body, which is a band-shaped loop antenna for transmission, by means of slot-shaped through-holes. This allows the received electromagnetic waves to be transmitted in two other directions, and unwanted radiation can be suppressed. For example, by installing the unpowered relay device of the present invention, which has bidirectional directivity, in the center of a T-junction within a structure, it becomes possible to efficiently re-radiate from one passage direction to two other passage directions that constitute the T-junction.
Furthermore, in the passive repeater of the present invention, the antenna body has a rectangular cross-section, making it possible to miniaturize and reduce its height. In addition, because radiation efficiency and miniaturization are possible, the number of antennas to be installed as a passive repeater can be reduced, thus reducing costs.

The unpowered relay device according to the second invention is characterized in that, in the first invention, it includes a conductive patch plate portion installed at a distance above the top plate portion.
In other words, this unpowered relay device has a conductive patch plate section installed at a distance above the top plate section. As a result, the top plate section of the antenna body, which functions as a strip-shaped loop antenna, is shared with the ground plate of the conductive patch plate section, which functions as a patch antenna. This connects the two antenna configurations via slot-shaped through-holes, further suppressing unwanted radiation and enabling more efficient re-radiation.

The unpowered relay device according to the third invention is characterized in that, in the second invention, the top plate portion is rectangular in shape, and the conductive patch plate portion is rectangular in shape following the outer shape of the top plate portion, with a pair of opposing corners cut out.
In other words, in this unpowered relay device, the conductive patch plate section has a rectangular shape that follows the outer shape of the top plate section, with a pair of opposing corners cut out. This allows for circular polarization by the conductive patch plate section with its cut-out corners, making it possible to receive both vertical and horizontal polarizations.

The powerless relay device according to the fourth invention is characterized in that, in any of the first to third inventions, the side wall portion is composed of a plurality of wall conductive pins erected in a row along the edge of the top plate portion.
In other words, in this unpowered relay device, the side walls are composed of multiple conductive pins for walls that are erected in a row along the edge of the top plate, so that the conductive pins for walls can act as a substitute for the side plates of the side walls and form an antenna body with a rectangular cross-section.

The powerless relay device according to the fifth invention is characterized in that, in any of the first to fourth inventions, a plurality of unit antennas composed of the antenna body are installed with their openings facing the same direction.
In other words, in this unpowered relay device, multiple unit antennas, each composed of an antenna body, are installed with their apertures facing the same direction. Therefore, the gain can be improved by arraying the unit antennas, and the directivity in the direction of the aperture can be further amplified to obtain sharp directivity. Consequently, the directivity on the intended installation surface can be made very small, making it possible to install the device close to structures.
Furthermore, the more unit antenna arrays (number of units installed), the higher the gain can be.

The present invention provides the following effects.
According to the unpowered relay device of the present invention, since the top plate portion has slot-shaped through holes extending along the opening direction of the opening, when incident waves from the front of the top plate portion are input through the slot-shaped through holes, the transmitted waves can be efficiently and inexpensively re-radiated from the pair of openings of the antenna body, which functions as a band-shaped loop antenna, in two directions on both sides of the opening direction.
Therefore, the powerless relay device of the present invention is suitable as a relay device for communications such as mobile phones and wireless LANs, and can be miniaturized and reduced in height to the extent that it can be installed inconspicuously inside or near structures.

This is a perspective view showing a first embodiment of the unpowered relay device according to the present invention. This is a graph showing the directivity of the unpowered relay device in the first embodiment. These are a plan view (a) and a side view (b) showing a second embodiment of the unpowered relay device according to the present invention. This is a graph showing the directivity of the unpowered relay device in the second embodiment. This is a plan view showing a third embodiment of the unpowered relay device according to the present invention. This is a graph showing the directivity of the unpowered relay device in the third embodiment. This is a perspective view showing a fourth embodiment of the unpowered relay device according to the present invention. This is a graph showing the directivity of the unpowered relay device in the fourth embodiment. This is a perspective view showing a fifth embodiment of the unpowered relay device according to the present invention. This is a graph showing the directivity of the unpowered relay device in the fifth embodiment. This graph shows the frequency characteristics of the RCS (Radar Cross Section) of a passive relay device with one unit antenna and in the fifth embodiment. This is a perspective view showing another example of a fourth embodiment of the unpowered relay device according to the present invention. This is a perspective view showing another example of a fifth embodiment of the unpowered relay device according to the present invention.

The first embodiment of the unpowered relay device according to the present invention will be described below with reference to Figures 1 and 2.

The passive repeater 1 in this embodiment is a so-called passive repeater, and as shown in Figures 1 and 2, it comprises a rectangular cross-section antenna body 5 made of a conductive material such as metal, having a pair of openings 5a at both ends, and having an upper and lower opposing top plate portion 2 and a lower plate portion 3, and a pair of left and right opposing side wall portions 4.
The top plate portion 2 has a slot-shaped through hole S that extends along the opening direction of the opening 5a.
In other words, the slot-shaped through-hole S extends in a direction along the opening direction of the opening 5a, and in the direction connecting the pair of openings 5a (which is the extension direction of the pair of side wall portions 4, and is the x-direction in Figure 1).

The top plate portion 2 and the bottom plate portion 3 are formed in a rectangular shape of the same size.
Furthermore, the top plate portion 2, the base plate portion 3, and the side wall portion 4 are all made of sheet metal.
The slot-shaped through-hole S described above is a slit that extends parallel to one side 2a of the top plate portion 2, and is positioned towards that side 2a.
The slot-shaped through-hole S is formed at a position spaced apart from the center point or center line C of the top plate portion 2.
In this embodiment, the top plate portion 2 and the bottom plate portion 3 are square in shape when viewed from above, and the antenna body 5 has a horizontally elongated, low-profile, and thin vertical cross-sectional shape.

In this embodiment, the dimensions of each part are set as follows, for example.
The length of one side of the top plate 2 and the bottom plate 3 x 1: 4.9 mm
Opening width of opening 5a x 2: 0.5 mm
Width of slot-shaped through hole S x 3: 0.2 mm
Length of slot-shaped through hole S x 4: 4.1 mm
Distance x 5 from the center line C of the top plate portion 2 of the slot-shaped through hole S: 0.9 mm

Figure 2 shows the directivity of the unpowered relay device 1 of this embodiment.
The directivity graph shown in Figure 2 simulates the re-radiation of the transmitted wave λ2 (horizontally polarized) in response to the incident wave λ1 (vertically polarized incoming wave) from the z-axis direction in Figure 1. This directivity graph is the result of simulating only horizontal polarization. In each of the following embodiments, the simulation was performed at 27.5 GHz.
In the unpowered relay device 1 of this embodiment, as shown in Figure 3, it has two-directional directivity in the xy plane and is re-radiated at an equivalent level in two opposing directions (the opening directions of the pair of openings 5a).

In this embodiment of the unpowered relay device 1, since the top plate portion 2 has a slot-shaped through-hole S extending along the opening direction of the opening 5a, when, for example, a vertically polarized incident wave λ1 is input from the front of the top plate portion 2 through the slot-shaped through-hole S, a horizontally polarized transmitted wave λ2 can be re-radiated from the pair of openings 5a of the antenna body 5, which functions as a band-shaped loop antenna, toward the opening directions on both sides.

In other words, a receiving slot antenna is configured in the top plate portion 2 of the antenna body 5, which is a strip-shaped loop antenna for transmission, by means of a slot-shaped through hole S. This allows the received electromagnetic waves to be transmitted in two other directions, and unwanted radiation can also be suppressed. For example, by installing the passive relay device 1 of this embodiment, which has two-directional directivity, in the center of a T-junction within the premises of a structure, it becomes possible to efficiently re-radiate from one passage direction to the other two passage directions that make up the T-junction.
Furthermore, because the antenna body 5 has a rectangular cross-section, it can be miniaturized and made low-profile. In addition, because radiation efficiency and miniaturization can be improved, the number of antennas to be installed as a passive repeater can be reduced, thus reducing costs.

Next, the second to fifth embodiments of the unpowered relay device according to the present invention will be described below with reference to Figures 3 to 13. In the following descriptions of each embodiment, the same reference numerals are used for the same components described in the above embodiments, and their descriptions are omitted.

The difference between the second embodiment and the first embodiment is that, in the first embodiment, the incident wave λ1 is directly received through a slot-shaped through-hole S formed in the top plate portion 2 of the antenna body 2, whereas, in the second embodiment's unpowered relay device 21, as shown in Figure 3, a conductive patch plate portion 26 is provided above the top plate portion 2 at a distance, and the incident wave λ1 is received through the slot-shaped through-hole S via the conductive patch plate portion 26.

In the second embodiment, an insulating spacer 26a made of resin or the like is installed between the conductive patch plate portion 26 and the top plate portion 2, separating the top plate portion 2 and the conductive patch plate portion 26.
In this embodiment, the conductive patch plate portion 26 is formed from a rectangular metal plate, and the conductive patch plate portion 26 is supported on the top plate portion 2 by rod-shaped insulating spacers 26a provided at its four corners.
The conductive patch plate portion 26 is a square shape, slightly smaller than the top plate portion 2, and shares the same central axis. It is positioned to cover the area directly above the slot-shaped through-hole S.

Figure 4 shows the directivity of the unpowered relay device 21 of the second embodiment.
In the unpowered relay device 21 of the second embodiment, as shown in Figure 4, it has directivity in two directions in the xy plane and is re-radiated at an equivalent level in two opposing directions (the opening directions of the pair of openings 5a). This directivity graph is the result of simulating only horizontal polarization.
Furthermore, in the second embodiment, as shown in Figure 4(a), it can be seen that unwanted radiation in the 90° direction is suppressed and the gain is improved compared to the first embodiment.

In this embodiment, the dimensions of each part are set as follows, for example.
Length of one side of top plate 2 and bottom plate 3 x 1: 5.37 mm
Opening width of opening 5a x 2: 0.5 mm
Width of slot-shaped through hole S x 3: 0.2 mm
Length of slot-shaped through hole S x 4: 2.0 mm
Distance x 5 from the center line C of the top plate portion 2 of the slot-shaped through hole S: 2.0 mm
Length of one side of conductive patch plate portion 26 x 6: 4.7 mm
Distance between conductive patch plate section 26 and top plate section 2 x 7: 0.25 mm

In this unpowered relay device 21, a conductive patch plate section 26 is provided above the top plate section 2 at a distance. Therefore, the top plate section 2 of the antenna body 5, which functions as a strip-shaped loop antenna, shares a surface with the ground plate of the conductive patch plate section 26, which functions as a patch antenna. This connects the two antenna configurations via slot-shaped through-holes S, further suppressing unwanted radiation and enabling more efficient re-radiation.

Next, the difference between the third embodiment and the second embodiment is that, in the second embodiment, rectangular conductive patch plate portions 36 are installed on the top plate portion 2 at intervals, whereas in the unpowered relay device 31 of the third embodiment, as shown in Figure 5, the conductive patch plate portion 36 is rectangular in shape that follows the outer shape of the top plate portion 2, with a pair of opposing corners cut out.
In other words, the unpowered relay device 31 of the third embodiment includes a hexagonal conductive patch plate portion 26 having a notch portion 36b in which a pair of opposing corners are cut out. In this embodiment, the notch portion 36b of the corner cut out from the square conductive patch plate portion 26 is in the shape of a perpendicular isosceles triangle.

Figure 6 shows the directivity of the unpowered relay device 31 of the third embodiment.
In the unpowered relay device 31 of the third embodiment, as shown in Figure 6, both vertically polarized and horizontally polarized waves are received and re-radiated in two directions.

In this embodiment, the dimensions of each part are set as follows, for example.
The length of one side of the top plate 2 and the bottom plate 3 x 1: 5.3 mm
Opening width of opening 5a x 2: 0.5 mm
Width of slot-shaped through hole S x 3: 0.2 mm
Length of slot-shaped through hole S x 4: 2.5 mm
Distance x 5 from the center line C of the top plate portion 2 of the slot-shaped through hole S: 1.4 mm
Width x height x 6 of conductive patch plate section 26: 4.8 mm
Distance between conductive patch plate section 26 and top plate section 2 x 7: 0.25 mm
The length of one side of the isosceles of the notch 36b x 8: 2.0 mm

In this unpowered relay device 31, the conductive patch plate portion 26 has a rectangular shape that follows the outer shape of the top plate portion 2, with a pair of opposing corners cut out. Therefore, the conductive patch plate portion 26 with its cut-out corners allows for circular polarization, enabling reception of both vertical and horizontal polarizations.

Next, the difference between the fourth embodiment and the second embodiment is that in the second embodiment, the side wall portion 4 is formed from a metal side plate that is continuous with the top plate portion 2 and the bottom plate portion 3, whereas in the unpowered relay device 41 of the fourth embodiment, as shown in Figure 7, the side wall portion 44 is composed of a plurality of wall conductive pins P that are erected in a row along the edge of the top plate portion 2.
The above-mentioned conductive pin P for the wall is formed from a metal rod, such as copper.

Figure 7 shows the directivity of the unpowered relay device 41 of the fourth embodiment.
In the fourth embodiment of the unpowered relay device 41, as shown in Figure 7, similar to the second embodiment, it has two-directional directivity in the xy plane and is re-radiated at an equivalent level in two opposing directions (the opening directions of the pair of openings 5a). This directivity graph is the result of simulating only horizontal polarization.

In this embodiment, the dimensions of each part are set as follows, for example.
The length of one side of the top plate 2 and the bottom plate 3 x 1: 5.9 mm
Opening width of opening 5a x 2: 0.5 mm
Width of slot-shaped through hole S x 3: 0.2 mm
Length of slot-shaped through hole S x 4: 4.0 mm
Distance x 5 from the center line C of the top plate portion 2 of the slot-shaped through hole S: 1.5 mm
Length of one side of conductive patch plate portion 26 x 6: 4.7 mm
Distance between conductive patch plate section 26 and top plate section 2 x 7: 0.25 mm

In this unpowered relay device 41, the side wall portion 44 is composed of multiple wall-mounted conductive pins P erected in a row along the edge of the top plate portion 2. Therefore, the wall-mounted conductive pins P can serve as a substitute for the side plate of the side wall portion 4 in the first embodiment, forming a rectangular cross-section antenna body 45.

Next, the difference between the fifth embodiment and the second embodiment is that in the first embodiment there is only one passive relay device 1, whereas in the passive relay device 51 of the fifth embodiment, as shown in Figure 9, multiple unit antennas 51A, each composed of an antenna body 5, are installed with their openings 5a facing the same direction.
In the fifth embodiment, for example, the unit antennas 51A are arranged in a 4x4 matrix on the same plane with a spacing x9 of 10.8 mm between them.

Figure 10 shows the results of a simulation of the directivity of the unpowered relay device 51 of the fifth embodiment, similar to the first embodiment.
In the unpowered relay device 51 of the fifth embodiment, as shown in Figure 10, it has directivity in two directions in the zx plane and stronger directivity in two directions in the xy plane, and is re-radiated at an equivalent level and stronger in two opposing directions.

Furthermore, Figure 11 shows the frequency characteristics of the RCS (radar cross-section) for one unit antenna 51A and the unpowered relay device 51 of the fifth embodiment.
As can be seen from these, the passive relay device 51 of this embodiment, which has multiple unit antennas 51A arranged in a row (indicated as "4x4 elements" in the figure), has improved gain compared to the case of a single unit antenna 51A (indicated as "single element" in the figure).

In the fifth embodiment of the unpowered relay device 51, since multiple unit antennas 51A, each composed of an antenna body 5, are installed with their openings 5a facing the same direction, the gain can be improved by arraying the unit antennas 51A, and the directivity in the direction of the opening 5a can be further amplified to obtain sharp directivity. Therefore, the directivity on the assumed installation surface can be made very small, making it possible to install the device close to structures.

Furthermore, the more arrays (number of units installed) of unit antennas 51A there are, the higher the gain can be.
Furthermore, although the unit antennas 51A are arranged on the same plane in this embodiment, multiple unit antennas 51A may be installed on multiple different planes spaced apart in the vertical direction.
For example, multiple unit antennas 51A may be arranged in a 4x4 matrix on two planes spaced apart in the vertical direction.
In this case, by stacking unit antennas 51A with different operating frequencies on two planes, the gain is improved, relaying can be performed at different operating frequencies, and the waveband can be expanded.

Furthermore, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

For example, although the passive relay device 21 of the second embodiment described above is made using sheet metal, it may also be made by forming copper foil or the like on a multilayer rigid substrate such as PTFE, which uses a dielectric material such as fluororesin as an insulating material, instead of sheet metal. For example, as another example of the second embodiment, as shown in Figure 12, a passive relay device 21B may be constructed by stacking a lower rigid substrate 27 and an upper rigid substrate 28.

In this unpowered relay device 21B, a base plate portion 23B is formed on the lower surface of the lower rigid substrate 27 using a rectangular conductive film such as copper foil, and a top plate portion 22B is formed on the upper surface of the lower rigid substrate 27 using a rectangular copper foil. In addition, a conductive patch plate portion 26B is formed on the upper surface of the upper rigid substrate 28 using a rectangular conductive film such as copper foil.
The top plate portion 22B described above is formed by creating a pattern with slot-shaped through holes S.

Furthermore, the lower rigid substrate 27 is provided with a plurality of via holes P2 into which a conductive material such as metal is embedded, connecting the base plate portion 23B and the top plate portion 22B, thereby forming a pair of side wall portions 24B.
Thus, in the unpowered relay device 21B, which is another example of the second embodiment, conductive foil such as copper foil is used instead of sheet metal, and via holes P2 are used as conductive pins for the wall, so that a rectangular cylindrical structure can be constructed that has slot-shaped through holes S and conductive patch plate portions 26B and has openings at both ends, similar to the unpowered relay device 21 of the second embodiment.

Furthermore, as another example of the fifth embodiment, as shown in Figure 13, by installing multiple passive relay devices 21B as unit antennas with their openings 5a facing the same direction, a passive relay device 51B with a configuration similar to that of the passive relay device of the fifth embodiment can be obtained.
In this passive relay device 51B, by using a large lower rigid substrate 27 and an upper rigid substrate 28, multiple passive relay devices 21B can be formed as unit antennas within the lower rigid substrate 27 and the upper rigid substrate 28.

1, 21, 21B, 41, 51, 51B…Unpowered relay device; 2…Top plate; 3…Bottom plate; 4, 44…Side wall; 5, 45…Antenna body; 5a…Opening; 26, 36…Conductive patch plate; 51A…Unit antenna; P…Conductive pin for wall; S…Slot-shaped through hole

Claims (5)

The antenna body has a rectangular cross-section and is made of a conductive material, with a pair of openings at both ends.
The antenna body comprises a top plate portion and a bottom plate portion that face each other across the pair of openings,
It has a pair of side walls that are installed between the top plate and the bottom plate and face each other with respect to the pair of openings in between,
The unpowered relay device is characterized in that the top plate portion has a slot-shaped through hole that extends along the opening direction of the opening. In the unpowered relay device according to claim 1,
A non-powered relay device characterized by having a conductive patch plate portion installed at a distance from the top plate portion on the opposite side of the bottom plate portion. In the unpowered relay device according to claim 2,
The aforementioned top plate is rectangular in shape.
The unpowered relay device is characterized in that the conductive patch plate portion has a rectangular shape that follows the outer shape of the top plate portion, with a pair of opposing corners cut out. In the unpowered relay device according to any one of claims 1 to 3,
The unpowered relay device is characterized in that the side wall portion is composed of a plurality of wall-mounted conductive pins erected in a row along the edge of the top plate portion. In the unpowered relay device according to any one of claims 1 to 3 ,
A passive relay device characterized in that multiple unit antennas, each composed of the aforementioned antenna body, are installed with their openings facing the same direction.