JP5913148B2 - Wireless tag system and wireless communication method - Google Patents

Description

  The present invention receives information (ID, collected data, etc.) transmitted from a radio tag installed in an underground facility such as a manhole by a ground reader, and easily and efficiently collects information on the underground facility from the ground. The present invention relates to a wireless tag system and a wireless communication method.

  In particular, a wireless tag system and a wireless communication method that can be applied to a passive wireless tag that does not have its own power supply, receives a radio wave transmitted from an antenna of a reader, operates with power obtained by an electromagnetic induction phenomenon, and transmits the radio wave. About.

FIG. 12 shows a configuration example of a conventional wireless tag system (Patent Document 1).
In FIG. 12, transmission / reception is performed between the wireless tag 100 installed in a manhole 500 and a reader 200 possessed by a worker on the ground. Of the radio waves transmitted from the wireless tag 100, only the direct wave directly directed to the ground has a low reception level at the reader 200, and transmission data may not be received reliably. Therefore, a radio wave reflection member 515 that reflects radio waves is disposed on the floor surface 510 of the manhole 500, the radio waves from the wireless tag 100 are reflected by the floor surface 510, and the reflected waves and direct waves are added together by the reader 200 on the ground. Enable reception.

JP 2011-243171 A

Nikkei BP "Wireless IC Tag Introduction Guide", "Part 3 UHF Band Capability", pp.142-143

  The conventional wireless tag system of FIG. 12 assumes an active wireless tag that incorporates a battery as the wireless tag 100 and periodically and autonomously transmits a wireless signal, and has moved to a position where the signal can be received. 200 receives the signal.

  On the other hand, when using a passive wireless tag that does not have a power supply instead of an active wireless tag, the passive wireless tag first receives the radio wave transmitted from the reader, and the reader receives the weak radio wave transmitted by the passive wireless tag. It needs to be possible. However, even if the radio wave reflecting member 515 shown in FIG. 12 is used, it is difficult to perform reliable communication between the reader 200 on the ground and the wireless tag 100 in the manhole 500.

  An object of the present invention is to provide a wireless tag system and a wireless communication method capable of reliably communicating between a wireless tag in an underground facility and a reader on the ground even when a passive wireless tag is used.

The first invention is provided with a wireless tag and the ground of the reader installed in the underground facilities, between the wireless tag and the reader, in a wireless tag system for transmitting and receiving information wirelessly, the wireless tag is, the back A first reflector that reflects radio waves in a shape that includes a part of a curved surface that is formed with the position of the wireless tag as a focal point is provided. The reader is different in size from the first reflector, and the reader In this configuration, a second reflector that reflects radio waves in the shape of a part of a curved surface formed with the position as a focal point is provided, and the reader is installed at a predetermined position facing the wireless tag .

In the wireless tag system of the first invention, the first reflector has a shape made of a part of the first paraboloid, and the second reflector has a distance between the focal point and the quasi-line of the first. It is the shape which consists of a part of 2nd paraboloid which is equal to a paraboloid . In addition, the first reflector has a shape made of a part of the first paraboloid, and the second reflector has a second distance in which the distance between the focal point and the quasi-line is different from that of the first paraboloid. It is the shape which consists of a part of paraboloid.

In the wireless tag system of the first invention, the first reflector has a shape made of a part of the first elliptic curved surface, and the second reflector has a distance between the two focal points of the first elliptic curved surface. And a shape composed of a part of a second elliptic curved surface different in size from the first elliptic curved surface . In addition, there are a plurality of sets of the first elliptic curved surface and the second elliptic curved surface, with one focus of each set as a common position, a wireless tag is disposed at the common position, and the other focus of each set is directed in a different direction. A reader is disposed at each of the focal points, the first reflector has a shape obtained by combining parts of the plurality of first elliptic curved surfaces, and the second reflector has each of the plurality of second elliptic curved surfaces. The shape consists of a part.

The second invention is provided with a wireless tag and the ground of the reader installed in the underground facilities, between the wireless tag and the reader, in a wireless tag system for transmitting and receiving information wirelessly, the distance between the two foci Two equal and different elliptical curved surfaces are defined as first and second elliptical curved surfaces, respectively, and the wireless tag is in contact with the first elliptical curved surface formed on the back surface with the position of the wireless tag as a focal point. A first wave that reflects a radio wave in a shape having a curvature radius intermediate between the curvature radius of the first elliptic curved surface and the curvature radius of the second elliptic curved surface, comprising a part of one curved surface of the egg-shaped curved surface having an asymmetric radius. The reader includes a reflector, and the reader is in contact with a second elliptic curved surface formed on the back surface with the position of the wireless tag as a focal point, and is composed of a part of the other curved surface of the egg-shaped curved surface, and has a curvature of the first elliptic curved surface. Between the radius and the radius of curvature of the second elliptical curved surface A second reflector that reflects radio waves in a shape having a radius of curvature is provided, and the reader is installed at a predetermined position facing the wireless tag .
.

A third invention is, between the wireless tag and the ground of the reader that is installed underground facility, the radio communication method of a wireless tag system for transmitting and receiving information wirelessly, the back of the radio tag, of the radio tag A first reflector that reflects radio waves in a shape formed of a part of a curved surface formed with a position as a focal point is arranged, and the size of the first reflector is different on the back surface of the reader, and the position of the reader is focused. by the second reflector is disposed for reflecting radio waves in a shape consisting of a part of the curved surfaces formed, placed in a predetermined position facing the reader to the wireless tag as a radio wave radiated from the radio tag first Then, the light is reflected by the second reflector and converged to the position of the reader.

In a third wireless communication method of the invention, the first and second reflectors, their respective a shape composed of a portion of a paraboloid, the radio waves radiated from the wireless tag first and second reflectors Are reflected at both sides and converged to the position of the reader.

In the wireless communication method of the third invention, the first reflector has a shape made of a part of the first elliptic curved surface, and the second reflector has a distance between the two focal points of the first elliptic curved surface. equally, and has a shape size and made of a portion of the second elliptic surface different from the first elliptic surface, is reflected by one of the radio waves radiated from the wireless tag first and second reflectors To converge to the reader position. In addition, there are a plurality of sets of the first elliptic curved surface and the second elliptic curved surface, with one focus of each set as a common position, a wireless tag is disposed at the common position, and the other focus of each set is directed in a different direction. A reader is disposed at each of the focal points , the first reflector has a shape obtained by combining parts of the plurality of first elliptic curved surfaces, and the second reflector has each of the plurality of second elliptic curved surfaces. a comprises a portion shaped, the radio waves radiated is reflected by either one first and second reflector to converge at the position of the reader from the radio tag.

A fourth invention is a wireless communication method of a wireless tag system in which information is transmitted and received wirelessly between a wireless tag installed in an underground facility and a reader on the ground , and the distance between two focal points is equal and large. Eggs having asymmetric radii of curvature with two elliptical curved surfaces having different curvatures as first and second elliptical curved surfaces, in contact with the first elliptic curved surface formed on the back surface of the wireless tag with the position of the wireless tag as a focal point A first reflector that reflects a radio wave in a shape that includes a part of one curved surface of the mold surface and has a curvature radius intermediate between the curvature radius of the first elliptic curved surface and the curvature radius of the second elliptic curved surface is disposed. , The back surface of the reader is in contact with the second elliptic curved surface formed with the position of the wireless tag as a focal point, and is composed of a part of the other curved surface of the egg-shaped curved surface, and the curvature radius of the first elliptic curved surface and the second Has a radius of curvature in the middle of the radius of curvature of the elliptical surface A second reflector for reflecting radio waves in the form of place, by placing the reader at a predetermined position opposed to the wireless tag, either the radio wave radiated from the wireless tag of the first and second reflectors On the other hand, it is reflected and converged to a position near the reader.

The present invention assumes a curved surface in which a wireless tag and a reader are disposed at two focal points, and a reflector that reflects radio waves in a shape that is a part of the curved surface is disposed on the back of the facing wireless tag and reader, By converging radio waves transmitted from one of the wireless tag and the reader to the other and receiving them, communication between them can be performed reliably.
In addition, by using two reflectors having different sizes (curvature radii), it is possible to make a reflector that matches the size of the wireless tag and the reader size correspond to each other.

It is a figure which shows the structural example of the radio | wireless tag system of this invention. It is a figure which shows the nature of a parabola and an ellipse. It is a figure which shows Example 1 of a parabolic reflector. It is a figure which shows Example 2 of a parabolic reflector. It is a figure which shows Example 3 of a parabolic reflector. It is a figure which shows Example 1 of an elliptical reflector. It is a figure which shows Example 2 of an elliptical reflector. It is a figure which shows Example 3 of an elliptical reflector. It is a figure which shows the definition of an egg type. It is a figure which shows the Example of an egg-shaped reflector. It is a figure which shows the communication area of a single dipole type UHF band IC tag. It is a figure which shows the structural example of the conventional wireless tag system.

  FIG. 1 shows a configuration example of a wireless tag system of the present invention. FIG. 1 (1) is a perspective view including a partial perspective, and FIGS. 1 (2) to 1 (4) are cross-sectional views perpendicular to the ground.

  In FIG. 1, 11 is the ground, 12 is the main body of the manhole in the basement, 13 is the ceiling of the manhole, 14 is the neck of the manhole (entrance / exit), 15 is the lid of the manhole, 21 is the wireless tag installed inside the manhole, 22 Shows schematically the readers deployed on the ground.

  The curved surface 23 is a parabolic curved surface (parabolic surface) or an elliptic curved surface focusing on the positions of the wireless tag 21 and the reader 22 and is set so as not to overlap the manhole cover 15. Here, an elliptical curved surface having two focal points at the positions of the wireless tag 21 and the reader 22 is illustrated as the curved surface 23, but two opposing paraboloids may be used. The distance between the wireless tag 21 and the reader 22 (the distance between the two focal points of the curved surface) is equal to or greater than the distance between the ceiling 13 of the manhole and the ground 11 or the distance between the wall surface of the manhole neck 14 and the ground 11.

  A feature of the present invention is that reflectors 24 and 25 that reflect radio waves in the shape of a part of the curved surface 23 are arranged on the back of the wireless tag 21 and the reader 22, and are transmitted and received between the wireless tag 21 and the reader 22. It is in the place where the radio wave is converged and reliable communication is possible.

  FIGS. 1A and 1B show an example in which the major axis of the elliptical curved surface is perpendicular to the ground 11 and the ceiling 13 of the manhole. FIG. 1 (3) shows an example in which the major axis of the elliptic curved surface is inclined with respect to the ground 11 and the ceiling 13 of the manhole. 1 (1) and 1 (4) show an example in which the major axis of an elliptical curved surface is inclined with respect to the ground 11 and the wall surface of the neck 14 of the manhole. In any case, the wireless tag 21 arranged at one focal point of the elliptical curved surface is located below the manhole ceiling 13 or inside the manhole neck 14, and the reader 22 arranged at the other focal point of the elliptical curved surface is Above the ground 11. Here, the opening surface of the reflector 24 on the back surface of the wireless tag 21 is in close contact with the cylindrical surface of the inner wall of the ceiling 13 of the manhole or the neck 14 of the manhole, and the opening surface of the reflector 25 on the back surface of the reader 22 is in close contact with the ground surface 11. However, each opening surface may be in a state separated from the ceiling or the ground.

  Here, the properties of the paraboloid and the elliptic curved surface will be described with reference to FIG. However, it is assumed that the x-axis and z-axis are two-dimensional, parabola and ellipse.

  In FIG. 2 (1), let the focal point of the parabola and one of the ellipses be a common F, let P be any point on the parabola and the ellipse, and let H be the point dropped from the point P to the quasi-line. When the ratio of the distance from the focal point F to the quasi-line is the eccentricity e (= PF / PH), e = 1 is defined as a parabola and e <1 is defined as an ellipse. The distance between one focal point F and the other focal point F ′ of the ellipse becomes smaller as the eccentricity e approaches zero.

In addition, the parabola has a focus F coordinate of (0, f).
z = (1 / 4f) x ²
It can be expressed as. In FIG. 2 (2), the parabola of the focal point F ₁ at coordinates (0, f ₁ ) and the parabola of the focal point F ₂ at coordinates (0, f ₂ ) are
F ₁ : z = (1/4 f ₁ ) x ²
F ₂ : z = (1/4 f ₂ ) x ²
When f ₁ <f ₂ , the opening of the parabola at the focal point F ₂ is wider.

Note that the three-dimensional paraboloid of the x, y, and z axes has the coordinates of the focal point F as (0, 0, f).
z = (1 / 4f) (x ² + y ² )
It can be expressed as.

  Based on the above relationship, the case where the reflectors 24 and 25 are part of a paraboloid or part of an elliptical curved surface will be described. In order to simplify the description, the parabolic reflectors A and B or the elliptical reflectors A and B will be described in association with a cross-sectional view perpendicular to the ground corresponding to FIG.

(Example of parabolic reflector)
FIG. 3 shows a first embodiment of the parabolic reflectors A and B.
In FIG. 3, the parabolic reflectors A and B of the first embodiment are configured by a part of two parabolas with the positions of the wireless tag 21 and the reader 22 as the focal points and the focal positions (distance f shown in the drawing) being equal. Is done. The radio wave radiated from the radio tag 21 arranged at the focal point of the parabolic reflector A is reflected by the parabolic reflector A and travels straight as a parallel line, and is reflected again by the opposing parabolic reflector B, and parabolically reflected. It converges at the position of the reader 22 arranged at the focal point of the device B. Although there are radio waves that reach the reader 22 directly from the wireless tag 21, most of the radio waves are reflected twice by the parabolic reflectors A and B and converge to the reader 22.

  Since the radio waves between the parabolic reflectors A and B are parallel lines, even if the vertical distance between the parabolic reflectors A and B changes slightly as shown in FIGS. The radio waves can be transmitted and received simply by directly facing the devices A and B. Further, as shown in FIGS. 3 (1) and 3 (3), if the parabolic reflectors A and B are overlapped even if they are slightly shifted in the horizontal direction, radio waves can be transmitted and received between the wireless tag 21 and the reader 22. It becomes possible. That is, the wireless tag system using the parabolic reflectors A and B has a degree of freedom with respect to the distance between the wireless tag 21 (manhole ceiling 13) and the reader 22 (ground 11), and also has some freedom with respect to lateral displacement. It can be said that it has a degree.

FIG. 4 shows a second embodiment of the parabolic reflectors A and B.
In FIG. 4, the parabolic reflectors A and B of the second embodiment have the same focal point position (distance f shown in the figure), and the radio tag 21 and the manhole ceiling 13 disposed at the focal point of the parabolic reflector A. Or the distance between the reader 22 arranged at the focal point of the parabolic reflector B and the ground 11 is shown.

  FIG. 4 (1) shows a state in which the reader 22 is separated from the ground 11 in order to enlarge the parabolic reflector B due to the ground space. In order to reduce the parabolic reflector A due to space restrictions in the manhole, the wireless tag 21 may be placed close to the ceiling 13 of the manhole. In any case, the opening width of the parabolic reflector B is relatively larger than that of the parabolic reflector A, and the degree of freedom with respect to the lateral shift of the parabolic reflectors A and B can be further increased. For example, as shown in FIG. 4 (2), if the parabolic reflector A is within the range of the parabolic reflector B, the parabolic reflector B allows almost 100% of the radio wave from the radio tag 21 reflected by the parabolic reflector A. It can be reflected and converged on the reader 22.

FIG. 5 shows a third embodiment of the parabolic reflectors A and B.
In FIG. 5, the parabolic reflectors A and B of the third embodiment are different in focal point positions (distances f _A and f _B shown in the figure), and the opening width of the parabolic reflector B is relatively larger than that of the parabolic reflector A. Therefore, an example in which f _A <f _B is shown. In addition, the distance between the radio tag 21 arranged at the focal point of the parabolic reflector A and the ceiling 13 of the manhole and the distance between the reader 22 arranged at the focal point of the parabolic reflector B and the ground 11 are substantially equal.

The basic functions shown in FIGS. 5 (1) and (2) are the same as those of the second embodiment shown in FIGS. 4 (1) and (2). Examples 2 and 3 have a relationship of f = f _A <f _B and are common in that the opening width of the parabolic reflector B is relatively larger than that of the parabolic reflector A. However, if the opening widths of the parabolic reflectors B of the second and third embodiments are made equal, the depth of the parabolic reflector B of the second embodiment becomes deeper. That is, in order to reduce the depth and increase the opening width, the position of the focal point (distance f _B shown in FIG. 5) of the parabolic reflector B on which the reader 22 is arranged may be adjusted as in the third embodiment.

  The parabolic reflectors A and B shown in FIGS. 3 to 5 may be opposed to the ground 11 and the ceiling 13 of the manhole in an oblique direction as shown in FIG. As shown in FIG. 4, the ground 11 and the neck 14 of the manhole may be opposed to each other in an oblique direction.

(Example of elliptical reflector)
FIG. 6 shows Example 1 of the elliptic reflectors A and B.
In FIG. 6, the elliptical reflectors A and B of the first embodiment are configured by a part of an ellipse having the positions of the wireless tag 21 and the reader 22 as two focal points. The radio wave a radiated from the wireless tag 21 arranged at one focal point of the ellipse is reflected by the elliptic reflector A and converges to the position of the reader 22 arranged at the other focal point of the ellipse. In addition, the radio wave b radiated from the wireless tag 21 arranged at one focal point of the ellipse is reflected by the opposing elliptic reflector B and converges to the position of the reader 22 arranged at the other focal point of the ellipse.

  When such elliptical reflectors A and B are used, the radio waves a and b radiated from the wireless tag 21 are reflected once by the elliptical reflector A or the elliptical reflector B and converge to the reader 22. The reflection loss can be reduced as compared with the case of using a parabolic reflector that performs round reflection.

  6 (1) and 6 (2) show an elliptic reflector A composed of a part of an ellipse with the eccentricity e changed according to the distance between the wireless tag 21 (manhole ceiling 13) and the reader 22 (ground 11). , B is shown. This utilizes the fact that, as shown in FIG. 2 (1), an ellipse sharing one focal point F expands and contracts in the major axis direction according to the eccentricity e. That is, if an interval is determined between the wireless tag 21 and the reader 22 according to the depth of the manhole, an ellipse having an eccentricity e corresponding to the interval is assumed, and a part of the ellipse is defined as an elliptic reflector A, B may be used.

FIG. 7 shows Example 2 of the elliptic reflectors A and B.
In FIG. 7, the elliptic reflectors A and B of the second embodiment use two large and small ellipses (hereinafter referred to as double ellipses) sharing two focal points, and a part of the small ellipse is defined as the elliptic reflector A. A part of the large ellipse is defined as an elliptic reflector B. The wireless tag 21 is disposed at the focal point of the elliptical reflector A, and the reader 22 is disposed at the focal point of the elliptical reflector B. The radio wave a radiated from the wireless tag 21 arranged at one focal point of the double ellipse is reflected by the ellipsoidal reflector A and converges to the position of the reader 22 arranged at the other focal point of the double ellipse. In addition, the radio wave b radiated from the wireless tag 21 arranged at one focus of the double ellipse is reflected by the opposing ellipsoidal reflector B, and at the position of the reader 22 arranged at the other focus of the double ellipse. Converge.

  When such elliptic reflectors A and B are used, the radio waves a and b radiated from the wireless tag 21 are reflected once by the elliptic reflector A or the elliptic reflector B and converge to the reader 22. Further, since the elliptic reflector B is larger by w than the smaller one of the double ellipse, the radio wave c radiated from the wireless tag 21 to the area w is also reflected by the elliptic reflector B and converges on the reader 22. To do. Thereby, the reception gain in the reader 22 can be increased.

  Similarly to the example shown in FIG. 6 (2), from a part of the double ellipse with the eccentricity e changed according to the distance between the wireless tag 21 (manhole ceiling 13) and the reader 22 (ground 11). It is also possible to adopt a configuration using elliptical reflectors A and B.

  The parabolic reflectors A and B shown in FIGS. 6 and 7 may be opposed to the ground 11 and the ceiling 13 of the manhole in an oblique direction as shown in FIG. As shown in FIG. 4, the ground 11 and the neck 14 of the manhole may be opposed to each other in an oblique direction.

FIG. 8 shows Example 3 of the elliptic reflectors A and B.
In FIG. 8, the elliptical reflectors A and B of the third embodiment are obtained by tilting two sets of elliptical reflectors A1 and B1 and elliptical reflectors A2 and B2 that are part of a double ellipse similar to the second embodiment in an oblique direction. In this configuration, the wireless tag 21 is arranged with one focus of two sets of double ellipses at a common position, and the readers 22-1 and 22-2 are arranged at the other focus, respectively. The radio wave radiated from the wireless tag 21 arranged at one common focal point of the two sets of double ellipses is reflected by the ellipsoidal reflectors A1 and A2, and the reader 22- arranged at the other focal point of the double ellipse. Converge to positions 1, 22-2, respectively. The radio waves radiated from the wireless tag 21 disposed at one common focal point of the two sets of double ellipses are reflected by the opposing ellipsoidal reflectors B1 and B2, respectively, and the other of the two sets of double ellipses is reflected. It converges at the position of the readers 22-1 and 22-2 arranged at the focal point.

  In this way, the wireless tag 21 is arranged with one focal point of the two pairs of double ellipses as a common position, and the two reflectors 22-1, 2-1, By receiving radio waves at 22-2, the reception gain can be increased.

  Although FIG. 8 is described as a combination of two sets of double ellipses in two dimensions, it can be described as a combination of four sets of double ellipses in three dimensions.

(Example of egg-shaped reflector)
As shown in FIG. 2, the ellipse changes its shape (curvature radius) according to the eccentricity e. On the other hand, in the case of a parabola and an ellipse sharing a focal point, a parabola is formed outside the ellipse.

  The feature of the parabola is that when radio waves radiated from the focal point of the parabola are reflected by the parabola reflector, the parabola goes straight as a parallel line. The feature of the ellipse is that the radio wave radiated from one focal point of the ellipse is reflected by the elliptical reflector and converges to the other focal point. In addition, as shown in FIG. 7, a double ellipse that shares two focal points can be formed. Therefore, even if an elliptic reflector is formed from each of a small ellipse and a large ellipse, the convergence characteristic is from one ellipse to an ellipse. It is not different from the case of forming a reflector.

  The characteristics of the egg-shaped reflector formed from a part of the egg shape will be described in consideration of the characteristics of the parabola and the ellipse. An egg shape generally has a shape in which the radius of curvature at both ends in the major axis direction is different and one end is rounded with respect to the other end, but is not defined as a quadratic curve such as a parabola, an ellipse, or a hyperbola.

As shown in FIG. 9, the egg shape has three fixed points on a straight line (referred to as a focal point for convenience, but different in nature from the focal point of the ellipse) F1, F2, F3 and distances r1, r2 from the egg shape line. , R3 satisfy the following relational expression. k, m, and n are arbitrary constants that satisfy k>m>n> 0.
mr1 ± nr2 = kc
-Kr2 + mr3 = ± n (k 2 -m 2) c / (m 2 -n 2)
± nr3 + kr1 = m (k 2 -n 2) c / (m 2 -n 2)
The double sign + represents an inner branch and-represents an outer branch. The focal distance is
The length of F1-F2 is c
The length of the F2 -F3 is ^{(k 2 -m 2) c /} (m 2 -n 2)
The length of the F1 -F3 are ^{(k 2 -n 2) c /} (m 2 -n 2)
It becomes.

FIG. 10 shows an embodiment of the egg-shaped reflectors A and B.
In FIG. 10, the egg-shaped reflectors A and B of the present embodiment are formed from a part of one egg shape, but a small ellipse 1 and a large ellipse 2 of a double ellipse sharing two focal points, and an ellipse. The relationship between the parabola 1 in contact with 1 and sharing the same focus and the parabola 2 in contact with the ellipse 2 and sharing the same focus is defined as follows based on the radius of curvature.
Parabola 1> egg reflector A> ellipse 1
Parabola 2> ellipse 2> egg reflector B
That is, the egg-shaped reflector A has a radius of curvature intermediate between the parabola 1 and the small ellipse 1, and the egg-shaped reflector B has a smaller radius of curvature than the large ellipse 2.

  The radio tag 21 is arranged at a common focal point of the parabola 1 and the double ellipse (ellipse 1) where the egg-shaped reflector A is formed, and the parabola 2 and the double ellipse (ellipse 2) where the egg-shaped reflector B is formed. The reader 22 is arranged at a common focus. The radio wave a1 radiated from the wireless tag 21 is reflected near the center of the egg-shaped reflector A and converges to the position of the point X slightly above the reader 22. The radio wave b1 radiated from the wireless tag 21 is reflected near the center of the opposing egg-shaped reflector B and converges to the position of the point X slightly above the reader 22. Similarly, the radio wave a2 radiated from the wireless tag 21 is reflected near the end of the egg-shaped reflector A and converges to the position of the point Y slightly above the X point. The radio wave b2 radiated from the wireless tag 21 is reflected near the end of the opposing egg-shaped reflector B and converges to a position of a point Y slightly above the point X.

  The points X and Y are continuously formed upward from the position of the reader 22 arranged at the focal point of the double ellipse according to the position where the radio wave is reflected. That is, the radio waves reflected by the egg-shaped reflectors A and B do not converge to one point like an elliptical focus, and have a certain width. Therefore, the reader 22 can be arranged at any position from the position of the focal point of the double ellipse shown in FIG. 10 to a position near the point Y according to the size of the radio wave receiving element. Alternatively, for example, the reader 22 may be arranged at each of the points X and Y, or the reader 22 including an area from the point X to the point Y may be configured, for example.

  Here, it will be described that the communication distance between the wireless tag 21 and the reader 22 is increased by using the reflectors 24 and 25 described as parabolic reflectors, elliptic reflectors, and egg-shaped reflectors.

  FIG. 11 shows a communication area of a single dipole UHF band IC tag (Non-Patent Document 1). Here, if it is inside the line indicating the communication area, it indicates that the wireless tag 21 and the reader 22 can communicate.

  FIG. 11A shows the communication area of the UHF band IC tag (center frequency 953 MHz) measured in the anechoic chamber, and the maximum communication distance is 9 m. The width of the communication area at 4.5m, which is half the maximum communication distance, is 2.4m. Fig. 11 (b) shows the communication area of the antenna in the 2.45 GHz band measured in the anechoic chamber. The maximum communication distance is 1.5 m, and the width of the communication area at the midpoint is 0.4 m. UHF band IC tag It can be seen that the communication area is overwhelmingly large.

  By disposing the reflector 24 on the back side of the single dipole type wireless tag 21 as described above, it is expected that the maximum communication distance is extended by narrowing the width of the communication area. At this time, according to the distance between the wireless tag 21 and the reader 22, the shape of the reflectors 24 and 25 and the size of the opening surface may be determined so that a required maximum communication distance can be secured.

  In each of the above embodiments, only the radio wave radiated from the wireless tag 21 to the reader 22 is shown. However, in the case of a passive radio tag, the electric power obtained by receiving the radio wave radiated from the reader 22 and electromagnetic induction phenomenon. The same applies to the radio waves radiated from the reader 22. That is, even when a passive wireless tag is used as the wireless tag 21, the radio tag 21 reliably receives the radio wave transmitted from the reader 22, and the reader 22 reliably receives the radio wave transmitted from the wireless tag 21, Information can be reliably transmitted from the wireless tag 21 in the manhole to the reader 22 on the ground.

11 Ground 12 Manhole body 13 Manhole ceiling 14 Manhole neck (entrance / exit)
15 Manhole cover 21 Wireless tag 22 Reader 23 Curved surface 24, 25 Reflector

Claims (11)

In a wireless tag system comprising a wireless tag installed in an underground facility and a reader on the ground, and wirelessly transmitting and receiving information between the wireless tag and the reader ,
The wireless tag includes a first reflector for reflecting radio waves in a shape consisting of a part of the curved surfaces formed a position of the wireless tag on the back as the focus,
The reader includes a second reflector that is different in size from the first reflector and reflects radio waves in a shape that includes a part of a curved surface formed on the back surface with the position of the reader as a focal point,
The wireless tag system, wherein the reader is installed at a predetermined position facing the wireless tag. The wireless tag system according to claim 1 ,
The first reflector has a shape composed of a part of a first paraboloid,
The wireless tag system, wherein the second reflector has a shape formed by a part of a second paraboloid in which a distance between a focal point and a quasi-line is equal to the first paraboloid . The wireless tag system according to claim 1 ,
The first reflector has a shape composed of a part of a first paraboloid,
The wireless tag system, wherein the second reflector has a shape formed by a part of a second paraboloid in which a distance between a focal point and a quasi-line is different from the first paraboloid . The wireless tag system according to claim 1,
The first reflector has a shape composed of a part of a first elliptic curved surface,
The second reflector has a shape composed of a part of a second elliptic curved surface in which the distance between two focal points is equal to the first elliptic curved surface and the size is different from that of the first elliptic curved surface. A wireless tag system characterized by The wireless tag system according to claim 4 ,
There are a plurality of sets of the first elliptic curved surface and the second elliptic curved surface, and the wireless tag is arranged at the common position with one focus of each set as a common position, and the other focus of each set in a different direction. the reader is arranged at the position of the focal point toward,
The first reflector has a shape obtained by combining parts of the plurality of first elliptic curved surfaces, and the second reflector has a shape formed by parts of the plurality of second elliptic curved surfaces. A wireless tag system characterized by that. In a wireless tag system comprising a wireless tag installed in an underground facility and a reader on the ground, and wirelessly transmitting and receiving information between the wireless tag and the reader ,
Two elliptical curved surfaces having the same distance between the two focal points and different sizes are defined as first and second elliptical curved surfaces, respectively.
The wireless tag is in contact with the first elliptical curved surface formed with the position of the wireless tag as a focal point on the back surface, and includes a part of one curved surface of an egg-shaped curved surface having an asymmetric radius of curvature. A first reflector that reflects radio waves in a shape having a radius of curvature intermediate between the radius of curvature of the elliptically curved surface and the radius of curvature of the second elliptically curved surface;
The reader is in contact with the second elliptic curved surface formed on the back surface with the position of the wireless tag as a focal point, and is composed of a part of the other curved surface of the egg-shaped curved surface, and the radius of curvature of the first elliptic curved surface And a second reflector that reflects radio waves in a shape having a curvature radius intermediate between the curvature radii of the second elliptic curved surface,
The wireless tag system, wherein the reader is installed at a predetermined position facing the wireless tag. In the wireless communication method of the wireless tag system that wirelessly transmits and receives information between the wireless tag installed in the underground facility and the reader on the ground,
On the back of the front Symbol wireless tag, placing the first reflector for reflecting radio waves in a shape consisting of a part of the curved surfaces formed a position of the wireless tag as the focus,
On the back surface of the reader, a second reflector that is different in size from the first reflector and reflects a radio wave in a shape formed of a part of a curved surface formed with the position of the reader as a focal point,
By installing the reader at a predetermined position facing the wireless tag, the radio wave radiated from the wireless tag is reflected by the first and second reflectors and converged to the position of the reader. Wireless communication method. The wireless communication method according to claim 7 , wherein
Said first and second reflector has a shape consisting of a part of their respective paraboloid,
The radio communication method, wherein the radio wave radiated from the radio tag is reflected by both the first and second reflectors and converged at the position of the reader. The wireless communication method according to claim 7 , wherein
The first reflector has a shape composed of a part of a first elliptic curved surface,
The second reflector has a shape composed of a part of a second elliptic curved surface having a distance between two focal points equal to that of the first elliptic curved surface and having a size different from that of the first elliptic curved surface;
The radio communication method, wherein the radio wave radiated from the radio tag is reflected by one of the first and second reflectors and converged to the position of the reader. The wireless communication method according to claim 9 , wherein
There are a plurality of sets of the first elliptic curved surface and the second elliptic curved surface, and the wireless tag is arranged at the common position with one focus of each set as a common position, and the other focus of each set in a different direction. the reader is arranged at the position of the focal point toward,
The first reflector has a shape obtained by combining parts of the plurality of first elliptic curved surfaces, and the second reflector has a shape formed by parts of the plurality of second elliptic curved surfaces. ,
The radio communication method, wherein the radio wave radiated from the radio tag is reflected by one of the first and second reflectors and converged to the position of the reader. In the wireless communication method of the wireless tag system that wirelessly transmits and receives information between the wireless tag installed in the underground facility and the reader on the ground ,
Two elliptical curved surfaces having the same distance between the two focal points and different sizes are defined as first and second elliptical curved surfaces, respectively.
The first ellipse is formed on a back surface of the wireless tag and is in contact with the first elliptical curved surface formed with the position of the wireless tag as a focal point, and is part of one curved surface of an egg-shaped curved surface having an asymmetric radius of curvature. A first reflector that reflects radio waves in a shape having a curvature radius intermediate between the curvature radius of the curved surface and the curvature radius of the second elliptic curved surface;
The back surface of the reader is in contact with the second elliptical curved surface formed with the position of the wireless tag as a focal point, and is composed of a part of the other curved surface of the egg-shaped curved surface. Arranging a second reflector that reflects radio waves in a shape having a radius of curvature intermediate to the radius of curvature of the second elliptic curved surface;
By setting the reader at a predetermined position facing the wireless tag, the radio wave radiated from the wireless tag is reflected by one of the first and second reflectors and converged to a position near the reader. A wireless communication method, characterized by:

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