JP2020038544A - Communication gate - Google Patents

Abstract

To provide technology for reducing an install area of a radio wave absorber without deteriorating the function of the radio wave absorber used in a communication gate system.SOLUTION: A pair of side wall parts (2, 3) are arranged to face each other across a passage, and formed of materials reflecting radio waves. An antenna (25) is provided on at least one of the pair of side wall parts. The side wall part comprises a first part (P1) of which at least a part is disposed opposite to the antenna, and a pair of second parts (P2) disposed on both sides in the passage direction, which is a direction along the passage, with the first part interposed therebetween, and of which the passage-side surface is covered with a radio wave absorber (24). Gate length that is length of the side wall part along the passage direction is L, and a first part width that is width of the first part along the passage direction is L1, setting L1≤L/2.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a communication gate installed at an entrance or the like of a facility to be monitored and used for wireless communication with a wireless device provided for a person or an object passing through the entrance.

2. Description of the Related Art A communication gate that performs wireless communication with a wireless device (for example, an RF tag) provided on a person or an object passing through the gate via an antenna is known.
Patent Literature 1 discloses that a plate member made of a radio wave absorber capable of absorbing radio waves and a reflector plate made of a conductor capable of reflecting radio waves are arranged on the side wall portion of the communication gate in an overlapping manner. I have. In addition, the radio wave absorber is disposed inside the gate, that is, on the passage side with respect to the reflection plate. This suppresses radio waves radiated from the antenna from leaking out of the gate and unnecessary radio waves from entering the gate from outside the gate.

JP 2008-234527 A

  By the way, as the radio wave absorber, one formed in a plate shape is generally used. In the communication gate, a gate length, which is a length along a passage (hereinafter, a passage direction), secures a time necessary for reliable reading from the RF tag when the communication target is the RF tag. Is set to

  In the conventional communication gate described in Patent Document 1, as the gate length increases, the installation area of the radio wave absorber disposed so as to cover the entire side wall increases. As a result, there is a problem that the plate-shaped radio wave absorber is difficult to handle, such as being easily distorted or broken, and a problem that the manufacturing cost of the device is increased due to an increase in the usage of the radio wave absorber. .

  An object of the present invention is to provide a technique for reducing the installation area of a radio wave absorber without deteriorating the function of the radio wave absorber used for a communication gate system.

  The invention according to claim 1 is a communication gate, which is provided on at least one of a pair of side walls formed of a material that reflects a radio wave, and is disposed to face each other with a passage therebetween. An antenna, wherein at least a part of the side wall portion has a first portion located opposite to the antenna, and a direction along the passage is defined as a passage direction, and the side wall portion has the passage direction sandwiching the first portion. And a pair of second portions whose surfaces facing the passage are covered with a radio wave absorber, and a gate length that is a length along the passage direction of the side wall portion is L. The width of the first portion, which is the width of the first portion along the direction of the passage, is set to L1, and L1 ≦ L / 2.

  According to a second aspect of the present invention, there is provided the communication gate according to the first aspect, wherein a surface facing the passage from a radiation center of the antenna at a side wall facing the antenna with the passage interposed therebetween. And the half width angle of the antenna is 2θ, and the first portion width L1 is set to L1 ≧ 2 · dc · tan θ.

  A third aspect of the present invention is the communication gate according to the first or second aspect, wherein the antenna is arranged such that the antenna is located in the side wall portion facing the front side of the antenna across the passage. It is characterized by having directivity satisfying an intensity condition that a radiation intensity in a direction where the end of the direction is located is equal to or less than a preset allowable leakage intensity.

  According to a fourth aspect of the present invention, in the communication gate according to the third aspect, the pair of side wall portions are configured such that an arrangement interval is variably set within a preset allowable range. The antenna satisfies the directivity in a state where the arrangement interval is at the upper limit of the allowable range.

  According to a fifth aspect of the present invention, there is provided the communication gate according to any one of the first to fourth aspects, wherein a surface of the first portion facing the passage is partially a radio wave. It is characterized by being covered with an absorber.

The invention according to claim 6 is the communication gate according to any one of claims 1 to 5, wherein the radio wave absorber is located at both ends of the side wall in the passage direction. A part is provided with a folded part projecting toward the passage.
The invention according to claim 7 is the communication gate according to any one of claims 1 to 6, wherein the antenna has a radiation center at a center of the side wall in the passage direction. The first portion is arranged such that a center of the first portion in the passage direction is opposed to the radiation center.

  According to the communication gate of the first aspect, of the radio waves radiated from the antenna and radiated toward the side wall (hereinafter referred to as the opposing side wall) opposed to the passage, the second part is irradiated. Radio waves are sufficiently attenuated by the radio wave absorber. Further, the radio wave applied to the first portion is reflected, and the reflected wave does not leak directly to the outside of the gate but goes to the side wall portion on which the antenna is provided. For this reason, the reflected wave leaking to the outside is reflected at least once at the second portion covered with the radio wave absorber, and thus is sufficiently attenuated.

  That is, according to the present invention, it is possible to obtain an effect similar to the case where the radio wave absorber is provided over the entire gate, although the installation of the radio wave absorber is omitted in the first portion. As a result, when the communication gate length is fixed, the usage amount of the radio wave absorber can be reduced, and when the usage amount of the radio wave absorber is fixed, the gate length can be further increased. In addition, since the divided wave absorber is used, the handling of the wave absorber can be facilitated.

  According to the communication gate of the present invention, an irradiation wave having a large power radiated toward the half-value angle of the antenna can be reliably multiple-reflected in the gate and can be effectively attenuated.

According to the communication gate according to the third aspect, the electromagnetic wave leaking directly to the outside of the gate can be reduced to the allowable leakage intensity or less.
According to the communication gate of the fourth aspect, the arrangement interval of the pair of side wall portions, that is, the passage width can be variably set within an allowable range, and any arrangement interval within the allowable range can be set. Even if it is set, the above effects can be obtained.

According to the communication gate of the fifth aspect, reflection at the first portion can be partially suppressed.
According to the communication gate according to the sixth aspect, the passage width can be kept wider while suppressing the intensity of the radio wave leaking from the gate, as compared with the case where there is no turn-back portion.
According to the communication gate of the present invention, it is possible to more effectively suppress the leakage of the radio wave to the outside of the gate.

It is a perspective view showing the appearance of the gate for RFID communication of an embodiment. It is a front view of the inner wall of the gate for RFID communication. It is a schematic diagram which shows the positional relationship of an antenna and a radio wave absorber, and the reflection state of a radio wave. It is a graph which shows the directivity of an antenna, and angle (alpha) w, (beta) w when passage width d is made into maximum value dw. It is a graph which shows the directivity of an antenna, and angles (alpha) n and (beta) n when the passage width | variety d is set to predetermined value dn smaller than maximum value dw. It is explanatory drawing which shows the relationship between the protrusion amount h of the folded part of the electromagnetic wave absorber, and the thickness w of an antenna.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[1. Constitution]
The communication gate 1 of the present embodiment is provided, for example, at an entrance of a facility to be monitored, and reads identification information from an RF tag attached to an article possessed by a passerby passing through the entrance. is there.

Therefore, as shown in FIGS. 1 and 2, the communication gate 1 has a pair of side walls 2 and 3 and a ceiling 4.
The pair of side walls 2 and 3 are arranged to face each other so as to sandwich the passage of the doorway. The ceiling part 4 connects the upper ends of the pair of side walls. The pair of side wall portions 2 and 3 and the ceiling portion 4 limit a region through which a person and an object can pass by surrounding the passage of the entrance from the left and right sides and from above.

Since the side wall 2 and the side wall 3 have the same structure, only the side wall 2 will be described below.
The side wall portion 2 includes a wall frame 21, a decorative plate 22, a reflector 23, a radio wave absorber 24, and an antenna 25.

  The wall frame 21 is composed of a plurality of rod-shaped hollow cylindrical pipes, and a pipe connector for connecting the pipes. The wall frame 21 has a structure in which partial frames each having a rectangular parallelepiped outer shape are stacked in a plurality of levels (three levels in the figure), and is assembled so that the overall shape becomes a rectangular parallelepiped. I have. However, the wall frame 21 has a structure in which pipes arranged in the horizontal direction are removed on the side facing the passage (hereinafter, the passage side) except for the upper end and the lower end. In the wall frame 21, a pair of columns 211 and 212 are provided on the surface on the side opposite to the passage side (hereinafter, outside) so as to vertically penetrate the stacked frame.

  Hereinafter, of the outer surface of the wall frame 21, a portion sandwiched between the pair of pillars 211 and 212 is defined as a first portion P1, and two portions located on both sides of the first portion with the first portion P1 defined as the first portion. It is called two site P2.

  The decorative plate 22 is fixed to the wall frame 21 so as to cover four surfaces (hereinafter referred to as attachment target surfaces) of the rectangular parallelepiped formed by the wall frame 21 except for the passage side surface and the lower surface facing the passage side. Is done. In addition, the decorative board 22 may be configured with a single member for each mounting target surface, or configured by combining a plurality of members divided according to the size of the surface formed by the partial frame body. May be done.

  The reflection plate 23 is a plate-like member formed of a metal material that reflects radio waves transmitted and received by the antenna 25. The reflection plate 23 is fixed to the wall frame 21 so as to cover the passage-side surface of the decorative plate 22 at the first portion P1.

  The radio wave absorber 24 is a plate-like member formed of a radio wave absorbing material that absorbs radio waves transmitted and received by the antenna 25, and an aluminum sheet that reflects radio waves is attached to one plate surface. The radio wave absorber 24 covers the passage-side surface of the decorative plate 22 at each of the two second portions P2, and the surface to which the aluminum sheet is attached faces outward, that is, the decorative plate 22 Is fixed to the wall frame 21 in a state where it faces. Note that the radio wave absorber 24 has a folded portion 24a on a side opposite to the side on the first portion P1 side. The folded portion 24a is a portion protruding toward the passage, and is formed such that the horizontal cross-sectional shape of the radio wave absorber 24 is L-shaped. In addition, as shown in FIG. 6, the protrusion amount h of the folded portion 24 a toward the passage is set to be equal to or less than the thickness w of the antenna 25. Further, in the radio wave absorber 24, the folded portion 24a may be formed integrally with another portion or may be formed separately.

  The radio wave absorber 24 is fixed to the wall frame 21 in a state where the surface to which the aluminum sheet is attached is in contact with the reflector 23. That is, the reflection plate 23 and the aluminum sheet of the radio wave absorber 24 form an electromagnetic wave reflection layer that covers the outer surface of the wall frame 21. The electromagnetic wave reflection layer prevents invasion of radio waves from outside the gate to the inside of the gate and leakage of radio waves from the inside of the gate to the outside of the gate.

  The radio wave absorber 24 that covers the second portion P2 may be formed of a single member as in the case of the decorative board 22, or may be formed by combining a plurality of members corresponding to the region divided by the partial frame. May be done. In the case where a plurality of members are combined, a metal plate that covers a gap generated at the boundary portion and that is in contact with the aluminum sheets of both members and conducts each other may be provided at a boundary portion between adjacent members.

  The antenna 25 is for performing wireless communication with an RF tag, and is configured by housing a planar antenna such as a patch antenna or the like in a rectangular antenna case.

The antenna 25 is fixed so that the radiation center C of the antenna 25 is located at the center position of the gate length that is the length along the passage direction of the side wall 2. However, the center position of the gate length of the side wall portion 2 and the radiation center C of the antenna 25 do not necessarily need to exactly coincide with each other, and there may be some deviation. Further, the antenna 25 may be mounted in a state where the longitudinal direction of the antenna case is slightly inclined with respect to the horizontal direction.
Note that a plurality of antennas 25 may be mounted at different heights of the side walls 2 and 3. The antenna 25 may be attached to only one of the pair of side walls 2 and 3.

  The ceiling portion 4 includes a plurality of pipes and a pipe connector similarly to the wall frame 21. The ceiling portion 4 has a shape in which a plurality of pipes are connected in a ladder shape, and connects the wall frame bodies 21 at the upper ends of the side wall portions 2 and 3 so as to straddle the passage.

  The ceiling 4 may be configured such that the arrangement interval of the side walls 2 and 3 and the width of the passage formed between the side walls 2 and 3 can be changed within a predetermined allowable range. Good.

[2. design]
Here, the section widths L1 and L2 of the first section P1 and the second section P2 along the passage direction will be described.

  FIG. 3 is a schematic diagram showing the positional relationship between the antenna 25, the first portion P1 where the reflector 23 is exposed, and the second portion P2 covered with the radio wave absorber 24, and the state of reflection of radio waves radiated from the antenna 25. FIG.

FIGS. 4 and 5 are graphs showing the directivity of the antenna 25 and the signal intensity at a plurality of reflection points in the gate.
First, the gate length L, which is the length of the side walls 2 and 3 along the passage direction, is set to a length that can secure a time during which the RF tag passing through the passage can be reliably read.

Next, the part widths L1 and L2 are set so as to satisfy the equations (1) and (2).
L1 ≦ L / 2 (1)
L2 = (L-L1) / 2 (2)
Here, the half-value angle of the antenna 25 is 2θ. The arrangement interval between the side wall portions 2 and 3 (that is, the passage width) is d. Here, as shown in FIG. 3, the distance between the passage-side ends of the folded portions 24a of the radio wave absorber 24 is defined as a passage width d. However, when comparing the passage side end of the folded portion of the radio wave absorber 24 provided on the same side wall portions 2 and 3 with the passage side end of the antenna 25, the antenna 25 protrudes toward the passage side. Therefore, when the antenna 25 is arranged only on one of the side walls 2 and 3, the actual passage width becomes smaller than d by the amount of the protrusion of the antenna 25. When the antennas 25 are provided on both the side walls 2 and 3, the actual passage width is the distance between the passage-side ends of the antennas 25, and is smaller than d by twice the protrusion of the antenna 25. Become.
The angle at which the boundary between the first portion P1 and the second portion P2 is viewed from the radiation center C of the antenna 25 is α. Similarly, let β be the angle from the radiation center C of the antenna 25 to the outer boundary end of the radio wave absorber 24 provided at the second portion P2 (however, a point visible from the radiation center C). Note that the outer boundary ends refer to both ends of the side wall portions 2 and 3 in the passage direction. Further, G is an upper limit of an allowable value of radio waves radiated from the antenna 25 and leaked from the communication gate 1 to the outside (hereinafter, a leak upper limit). The leakage upper limit G is expressed as a relative gain with respect to the maximum gain of the antenna 25 (here, the gain in the front direction).

The antenna 25 has directivity such that the gain in the azimuth equal to or more than the angle β is equal to or less than the leakage upper limit G.
Further, the region width L1 may be set so as to satisfy the condition (3) in addition to the condition (1). Here, dc is the distance from the radiation center C of the antenna 25 to the outer side surface of the side wall portion opposed across the passage. When the radiation center C of the antenna 25 is located on the outer side surface of the antenna 25, dc is expressed by Expression (4). h1 is the thickness of the radio wave absorber 24.

L1 ≧ 2 · dc · tanθ (3)
dc = d + 2 · h + h1 (4)
Equation (3) is an equation for obtaining the part width L1 such that α ≦ θ, and is a condition for efficiently using the power radiated from the antenna 25.

  Note that the radio wave absorber 24 has a radio wave absorption performance of attenuating the irradiated radio wave more than the leakage upper limit G. For example, when G = −10 dB, the electromagnetic wave absorber 24 having an absorption performance of −15 dB, for example, is used.

  When the passage width d can be variably set, the passage width d may be designed so as to satisfy the above conditions when the passage width d is the maximum width dw. Αw and βw shown in FIG. 4 indicate the above-mentioned angles α and β when the passage width d is the maximum width dw. Further, αn and βn shown in FIG. 5 indicate the above-mentioned angles α and β when the passage width d is a predetermined width dn smaller than the maximum value dw.

[3. motion]
In the communication gate 1, radio waves radiated from the antenna 25 and leaking directly to the outside of the gate, that is, radio waves going outside the angle range indicated by −βw to βw in FIG. The strength is equal to or less than the upper limit G.

  The radio wave radiated from the antenna 25 and irradiated toward the second portion P2 is sufficiently attenuated by the radio wave absorber 24. As a result, even if the reflected wave from the second portion P2 leaks to the outside of the gate as it is, it is attenuated to the leak upper limit G or less.

  The radio wave radiated from the antenna 25 and irradiated toward the first portion P1 is reflected by the reflector 23, and the reflected wave does not leak directly to the outside of the gate, and the side wall on the side where the antenna 25 is provided. It goes to parts 2 and 3 and makes multiple reflections in the gate. Then, due to the positional relationship between the first portion P1 and the second portion P2, the multiple reflection wave traveling to the outside of the gate is reflected at least once by the second portion P2 covered with the radio wave absorber 24. Therefore, the multiple reflected waves leaking to the outside of the gate are attenuated below the leakage upper limit G.

  When the passage width d is a predetermined width dn narrower than the maximum width dw, the angles α and β are αn and βn wider than those at the maximum width dw, as shown in FIG. As a result, the radio wave radiated from the antenna 25 and leaking directly to the outside of the gate, that is, the radio wave going out of the angle range indicated by −βn to βn in FIG.

  In each of FIGS. 4 and 5, a signal within a half-value angle at which the directivity has a signal strength within -3 dB is reflected by the reflecting plate 23. Used efficiently for reading.

[4. effect]
As described above, according to the communication gate 1, the radio wave absorber 24 is provided on the entire side walls 2 and 3 although the radio wave absorber 24 is not provided on the first portion P1. As in the conventional device, the leakage of the radio wave to the outside of the gate can be suppressed. As a result, when the gate length L is fixed, the amount of use of the radio wave absorber 24 can be reduced as compared with the conventional device, and when the use amount of the radio wave absorber 24 is fixed, a longer gate can be used. The length L can be realized.

  According to the communication gate 1, the radio wave absorber 24 is installed at each of the side walls 2 and 3 at two locations, so that the radio wave absorber 24 having a smaller size than the conventional device can be used. In addition, the transportation and installation of the radio wave absorber 24 can be easily performed. In particular, even if the radio wave absorber 24 is made of a material that is easily deformed by heat or shock, the stress is dispersed by the reduction in size, so that distortion and breakage after assembly to the communication gate 1 can be suppressed.

  According to the communication gate 1, when the passage width d can be variably set within the allowable range, the above formulas (1) to (3) should be satisfied when the passage width d is the maximum width dw within the allowable range. Is set. Therefore, no matter how the passage width d is set within the allowable range, the radio wave leaking to the outside of the gate can be made equal to or less than the leakage upper limit G.

  In the communication gate 1, a folded portion 24 a protruding toward the passage is provided at an outer boundary end of the radio wave absorber 24. This allows the passage width d to be kept wider than in the case where there is no folded portion 24a. That is, if the gate length L is constant, the angle β becomes larger when there is the folded portion 24a than when there is no folded portion 24a, and the angle β is not reflected by the side walls 2 and 3 and is outside the gate. The intensity of radio waves leaking directly to Therefore, the passage width d can be increased while suppressing the intensity of radio waves leaking directly to the outside of the gate.

[5. Other Embodiments]
As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and can take various forms without departing from the gist of the present invention.

  In the above embodiment, the installation of the radio wave absorber 24 at the first portion P1 is omitted, but the radio wave absorber may be provided at a part of the first portion P1. That is, the surface of the first portion P1 on the side facing the passage may be partially covered with the radio wave absorber. In this case, the radio wave absorber disposed at the first portion P1 may have a lower radio wave absorption performance than the radio wave absorber 24 disposed at the second portion P2, or may have a higher radio wave absorption performance. May be used. The radio wave absorber installed in the first portion P1 may be arranged so as to form a specific pattern, or may be arranged randomly. Further, a radio wave absorber having radio wave absorption performance different from that of the radio wave absorber 24 provided at the second portion P2 may be spread over the entire first portion P1.

  In the above-described embodiment, the wave absorber 24 is formed in a plate shape. However, the wave absorber 24 may be formed in a wave shape, or may be formed with a plurality of protrusions dispersed and uneven. Good.

In the above embodiment, the radio wave absorber 24 in which an aluminum sheet acting as a reflector is integrated is used, but these may be formed separately.
In the above embodiment, the case where the wireless device to be communicated by the communication gate 1 is the RF tag has been described, but the present invention is not limited to this. The wireless device to be communicated by the communication gate 1 may be, for example, a wireless terminal mounted on a moving body such as an automobile, a portable terminal carried by a person passing through the gate, and the like.

  Although the communication gate 1 of the above embodiment has been described as being assembled with the antenna 25, the antenna 25 is separate from the communication gate 1 and is arranged inside the gate using a dedicated support member. You may.

  DESCRIPTION OF SYMBOLS 1 ... Communication gate, 2, 3 ... Side wall part, 4 ... Ceiling part, 21 ... Wall frame, 22 ... Decorative plate, 23 ... Reflection plate, 24 ... Radio wave absorber, 24a ... Turnover part, 25 ... Antenna, 211, 212 ... pillar, P1 ... 1st part, P2 ... 2nd part.

Claims (7)

A pair of side walls that are arranged opposite to each other with the passage therebetween and formed of a material that reflects radio waves,
An antenna provided on at least one of the pair of side wall portions,
With
The side wall portion,
A first portion at least partially opposed to the antenna,
A pair of second portions, which are located on both sides in the passage direction with the first portion interposed therebetween with the direction along the passage as the passage direction, and whose surfaces facing the passage are covered with a radio wave absorber,
Has,
L1 ≦ L / 2, where L is a gate length that is the length of the side wall portion along the passage direction, and L1 is the first portion width that is the width of the first portion along the passage direction. Communication gate. The communication gate according to claim 1,
The distance from the radiation center of the antenna to the surface opposite to the surface facing the passage in the side wall portion facing the antenna with the passage interposed therebetween is dc, and the half value angle of the antenna is 2θ,
A communication gate wherein the first portion width L1 is set to L1 ≧ 2 · dc · tan θ. The communication gate according to claim 1 or 2, wherein:
The antenna has a directivity such that a radiation intensity from a radiation center of the antenna in a direction in which the end in the passage direction is located on the side wall facing the side of the passage is equal to or less than a preset leakage upper limit. Having a communication gate. The communication gate according to claim 3, wherein
The pair of side wall portions are configured such that the arrangement interval is variably set within a preset allowable range,
The communication gate, wherein the antenna is set to satisfy the directivity condition when the arrangement interval is the maximum width of the allowable range. A communication gate according to any one of claims 1 to 4, wherein:
A communication gate in which a surface of the first portion facing the passage is partially covered with a radio wave absorber. A communication gate according to any one of claims 1 to 5, wherein
A communication gate, wherein the radio wave absorber is provided with a folded portion protruding toward the passage at portions located at both ends of the side wall in the passage direction. A communication gate according to any one of claims 1 to 6, wherein:
The antenna is arranged such that a radiation center is located at a center of the side wall portion in the passage direction,
The communication gate, wherein the first portion is arranged such that a center of the first portion in the passage direction faces the radiation center.