JP5204043B2 - Booster antenna for RFID tag - Google Patents

Description

  The present invention relates to a booster antenna for an RFID tag for extending a communication distance between a reader of an interrogator and an RFID tag of a responder in an RFID (Radio Frequency Identification) tag system.

  In recent years, as means for automatically recognizing information on articles such as products and parts, an RFID tag is attached to a case containing the article or article, and the article information recorded on the RFID tag is supplied with electric power from a reader by radio waves. RFID tag systems for reading have been put into practical use. Compared with barcode systems that optically read article information from barcodes, this RFID tag system can record more information and can rewrite information, so it is widely used in a wide range of fields such as manufacturing and distribution service industries. I am doing.

  The RFID tag system communication system that supplies power by radio waves from the antenna of the reader includes an electromagnetic induction system that uses a long wave with a frequency of 135 kHz or less or a short wave such as 4.915 MHz or 13.56 MHz, and a frequency of several hundred MHz or more. And a radio wave system using microwaves such as 2.45 GHz. The radio wave radiated from the reader antenna by the radio wave method includes a rotating circularly polarized wave, a non-rotating linearly polarized wave, and an elliptically polarized wave obtained by combining these.

  An electromagnetic induction method using radio waves having a long wavelength has characteristics that the directivity of the antenna is wide and hardly affected by water, but the communication distance is usually several tens cm or less. On the other hand, a radio wave system using a radio wave having a short wavelength is easily affected by water, but has high antenna directivity, and the communication distance is usually about 0.2 to 5 m. These communication methods are selectively used depending on the usage environment and whether the article contains a liquid such as water.

  In the electromagnetic induction type RFID tag system, a booster antenna tuned to a carrier frequency of a radio wave from a reader is disposed in front of the RFID tag so as to face the reader, thereby extending a communication distance. (For example, refer to Patent Document 1). In the device described in Patent Document 1, a booster antenna is attached around the front door of a cabinet that houses a product to which an RFID tag is attached.

  In addition to the antenna elements connected to the semiconductor circuit, the RFID tags used in the radio frequency RFID tag system are arranged with waveguide and reflection antenna elements, and the lengths of these antenna elements are read out. In some cases, the communication distance is extended as an integral multiple of the half-wavelength λ / 2 of the radio wave from (for example, see Patent Document 2).

JP 2005-323019 A JP 2002-151947 A

  The RFID tag of the radio wave system described in Patent Document 2 needs to be arranged for an antenna element for waveguide or reflection in addition to an antenna element connected to a semiconductor circuit. There is a problem that the RFID tag used is expensive and has a large size. Further, since the number of waveguide and reflection antenna elements that can be arranged on the RFID tag is limited, the communication distance cannot be extended so much.

  Accordingly, an object of the present invention is to greatly extend the communication distance in a radio frequency RFID tag system.

In order to solve the above-described problems, the RFID tag booster antenna of the present invention is a radio frequency RFID tag IC chip that receives and responds to a radio wave having a rotating circularly polarized component from an interrogator reader antenna. Are arranged on one plane facing the reader antenna on the same side as the antenna of the RFID tag, with a length H and a center C spaced apart from an antenna defined as follows: It is composed of at least two straight lines, an open curve, a closed curve, or linear antenna elements obtained by intersecting these straight lines or curves. The length L, width W, and center of gravity G of these linear antenna elements are expressed as follows: When the ratio L / W between the length L and the width W of each antenna element is 2 or more, the points a1 and a2 at both ends in the length direction of the antenna element in the definition of the length L below are defined. There is only one set, and the length L with respect to the wavelength λ of the radio wave from the antenna of the reader is in the range of 0.2λ to 0.9λ. One of the points a1 and a2 at both ends of the other antenna element from the base end point, with the point at one end of the points a1 and a2 at the both ends of the element itself as the base end point and the point at the other end as the front end point Inclination angle φ in the direction of rotation of the radio wave of the direction of the line segment between itself extending from the base end point to the direction of the front end point with respect to the direction of the four line segments between the counterparts extending so as to connect However, a configuration is adopted in which the angle is 15 ° or more and 120 ° or less with respect to at least one of the four line segments of the other party.
(Definitions regarding RFID tag antennas)
Length H: The maximum value of the linear distance between any two points on the antenna connected to the IC chip is defined as length H.
Center C: The center C is the midpoint between two points where the straight line distance is the maximum in the definition of length H.
(Definitions regarding antenna elements)
Length L: Two arbitrary points i and j are selected on the linear antenna element, and the traveling direction of the path from point i to point j along the antenna element with respect to vector Vij from point i to point j Point i and point j are connected without returning when the angle formed by the direction of the vector Vij and the direction of the vector Vij is within ± 90 ° at all points in the path. Of the combination of two arbitrary points i and j, the two points having the longest linear distance between the two points i and j are the points a1 and a2 at both ends in the length direction, and the antenna element between these points a1 and a2 The length of the shortest path along the line is defined as a length L.
Width W: When there are a plurality of points of the antenna element on an arbitrary straight line parallel to the straight line (width direction) and the straight line connecting the points a1 and a2 at both ends in the definition of the length L, the plurality of points The two points having the longest distance in the width direction are the points b1 and b2 at both ends in the width direction, the length of the shortest path along the antenna element between these points b1 and b2, and the straight line between the points b1 and b2 The minimum value of the length π / 2 times the distance and the minimum length L is w1, and these two arbitrary straight lines intersecting the antenna element are parallel to the straight line connecting the points a1 and a2 at both ends. When the smaller value of the maximum distance between two straight lines and the length L is w2, the larger value of w1 and w2 is the width W.
Center of gravity G: The center of gravity of the strands existing in all the shortest paths between the points a1 and a2 at both ends in the definition of the length L is defined as the center of gravity G.

  8 (a) to 8 (f) show the definition and the center of gravity of the length L and the width W for various types of linear antenna elements having only one set of points a1 and a2 at both ends in the length direction. The position of G will be specifically described. FIG. 8 (a) shows the simplest straight antenna element, the points at both ends become the points a1 and a2 at both ends in the length direction, and the length of the straight line becomes the length L of the antenna element as it is. The distance between the points b1 and b2 at both ends in the direction, that is, the width of the linear element becomes the width W of the antenna element. Further, the position of the center of gravity G coincides with the center of gravity of all the strands forming one shortest path, and becomes a midpoint between the points a1 and a2.

  FIG. 8B shows an antenna element with an open circular arc. Both end points are points a1 and a2 at both ends in the length direction, and the length along the arc curve is the length L of the antenna element. Become. Also, since the distance between the points b1 and b2 at both ends in the width direction, that is, w1 of the arc antenna element is sufficiently small, a straight line m0 connecting the points a1 and a2 and a straight line m1 parallel to this and tangent to the arc curve The distance w2 between the two straight lines is the width W of the antenna element. Also in this case, the position of the center of gravity G coincides with the center of gravity of all the strands forming one shortest path, and is a position deviated from the midpoint between the points a1 and a2 toward the arc curve.

  FIG. 8C shows an antenna element with a wave-like open curve having a constant amplitude, and the points at both ends become the points a1 and a2 at both ends in the length direction, and the length along the wave-like curve is the length of the antenna element. Length L. Further, since the distance between the points b1 and b2 at both ends in the width direction, that is, w1 of the wavy antenna element is sufficiently small, the wave parallel to the straight line m0 connecting the points a1 and a2 passes through the vertices of the waves on both sides of the wavy curve. The distance w2 between the two straight lines m1 and m2 is the width W of the antenna element. Also in this case, the position of the center of gravity G matches the center of gravity of all the strands forming one shortest path.

  FIG. 8D shows an antenna element having an L-shaped open curve. Two points at both ends of the L-shape are points a1 and a2, and the length of the path from the point a1 to the point a2 along the L-shape. Becomes the length L of the antenna element. Also in this example, since the distance between the points b1 and b2 at both ends in the width direction, that is, w1 of the L-shaped antenna element is sufficiently small, a straight line m0 connecting the points a1 and a2 and an L-shaped corner parallel to the straight line m0. The distance w2 between two straight lines with the tangent line m1 passing through the point is the width W of the antenna element. Also in this case, the position of the center of gravity G coincides with the center of gravity of all the strands forming one shortest path, and is a position deviated from the vicinity of the middle point between the points a1 and a2 toward the L-shaped corner point.

  FIG. 8E shows a J-shaped open-curve antenna element, where the upper end point of the J shape is the point a1 and the lower point of the J shape is the point a2, and the path from the point a1 to the point a2. Is the length L of the antenna element. Regarding the width W, two points on the straight line n1 passing through the point at the lower end of the J character among the straight lines perpendicular to the straight line m0 connecting the points a1 and a2 are the points b1 and b2. The length of π / 2 times the linear distance between b2, that is, the length of the semicircular arc whose diameter is the line segment b1b2, becomes smaller than the length and the length L of the shortest path between the points b1 and b2. It becomes. Further, since the distance between the straight line m1 passing through the point b1 and the straight line m2 passing through the point b2 that is parallel to the straight line m0 is smaller than the length L, it becomes w2. In this case, w1 larger than w2 is the width W of the antenna element. The position of the center of gravity G coincides with the center of gravity of the strand between the points a1 and a2 forming one shortest path.

  FIG. 8F shows an antenna element having an elliptical closed curve, and two points on the major axis of the ellipse become points a1 and a2 at both ends of the antenna element, and two equal points from point a1 to point a2 are shown. The length of the path is the length L of the antenna element. Regarding the width W, two points on the straight line n1 passing through the parallel part of the ellipse among the arbitrary straight lines parallel to the straight line m0 connecting the points a1 and a2 are the points b1 and b2, and the point b1 , B2 is equal to or smaller than the length of the shortest path between the points b1 and b2 and is smaller than the length L to be w1. In addition, since the distance between the two straight lines m1 and m2 that are parallel to the straight line m0 and pass through the points b1 and b2 is smaller than the length L, it becomes w2, and w1 larger than w2 becomes the width W of the antenna element. The position of the center of gravity G coincides with the center of gravity of all the strands forming the two shortest paths and becomes the center of an ellipse.

  FIG. 9 shows an angle of inclination φ in the rotation direction of the radio wave in the direction of the line segment e between the counterparts of the two antenna elements, the line segment f between the counterparts, and the direction of the line segment f between the counterparts. An example in which two antenna elements have the same L-shape will be described. As shown in FIGS. 9 (a) to 9 (d), between one of the points a1 and a2 at both ends of one antenna element as a base end point and the other party connecting to either of the points a1 and a2 at both ends of the other antenna element There are four line segments e, and there is one line segment f between the lines connecting the points a1 and a2 at both ends of each antenna element. In each figure, the inclination angle when the rotation direction of the radio wave is counterclockwise is indicated as φ1, and the inclination angle when the rotation direction of the radio wave is clockwise is indicated as φ2. There are also four inclination angles φ1 and φ2 in the rotation direction of the radio wave in the direction of each inter-segment line segment f with respect to the direction for each antenna element.

  In the present invention, the inclination angle of the direction of the inter-segment line f of each antenna element in the rotation direction of the radio wave with respect to the direction of the specific inter-segment line segments e1 and e2 among the four inter-segment line segments e. The range is regulated so that φ1 and φ2 are 15 ° or more and 120 ° or less. The line segment e between the opponents becomes the specific line segments e1 and e2 as shown in FIGS. 9 (b) and 9 (d). When the radio waves are rotated in the counterclockwise direction relative to the extended straight line, when the direction of rotation of the radio wave is counterclockwise, the one shown in FIG. When the direction of rotation of the radio wave is clockwise, the line segment e1 is the specific partner line segment e2 whose inclination angle φ2 falls within the above range in FIG. 9D. That is, in the arrangement of FIG. 9, there are specific partner line segments e1 and e2 regardless of the rotation direction of the radio wave. Thus, if there is a specific partner line segment in the rotation direction of one radio wave, the specific partner line segment often exists also in the rotation direction of the other radio wave. The two antenna elements have only one set of points a1 and a2 at both ends in the length direction, and the ratio L / λ between the length L and the wavelength λ of the radio wave is 0.2 to 0.9. What is necessary is just to enter into a range, and the dimension and shape do not necessarily need to be the same.

  The present inventor separates the reader antenna that transmits radio waves having a circularly polarized component rotating from the antenna of the radio frequency RFID tag on one plane facing the antenna on the same side, The two linear antenna elements as described above are arranged, and a communication experiment is performed by changing the length L of each antenna element. When the inclination angle φ in the rotation direction is regulated to be 15 ° or more and 120 ° or less, the ratio L / λ of the length L of the antenna element to the wavelength λ of the radio wave becomes 0.2 to 0.9. It was found that the communication distance can be extended within the range. Conventionally, as described in Patent Document 2, the length L of the antenna element suitable for extending the communication distance is an integral multiple of the half wavelength λ / 2 of the radio wave, that is, the shortest suitable antenna element. Is considered to be 0.5λ.

  The reason why the communication distance can be extended even when the length L of the antenna element is changed in the range where the ratio L / λ is 0.2 to 0.9 is not clear, but is considered as follows. . When the booster antenna is arranged on the same side of the reader antenna as being separated from the RFID tag antenna, the primary radio wave directly reaching the RFID tag antenna from the reader antenna and the RFID via the booster antenna A phase shift δ occurs between the secondary radio wave reaching the tag antenna, and the primary radio wave and the secondary radio wave are within a range where the phase shift δ is an integer multiple of ± 0.2 times the period of the radio wave. If there is a large amount of overlap between the peaks, the radio wave is strengthened and the communication distance becomes long, and if the phase shift δ exceeds this range, the overlap between the peaks and valleys of the primary and secondary waves increases. Is weakened and the communication distance is shortened.

  As a cause of the phase shift δ generated between the primary radio wave and the secondary radio wave, in addition to the phase shift between the received wave and the transmitted wave of the booster antenna due to the length L of the antenna element, the phase shift due to the optical path difference of the radio wave, When the radio wave transmitted from the reader antenna has a circularly polarized component that rotates, a phase shift due to the inclination angle between the antenna direction of the RFID tag and the antenna element with respect to the rotation direction of the radio wave can be considered. For this reason, even when the length L of the antenna element is changed in a range away from 0.5λ when the inclination angle φ is regulated to be 15 ° or more and 120 ° or less, the above-described factors are included. The overall phase shift δ is in a range where the radio wave is strengthened as described above, and the communication distance seems to be extended.

  Based on the above-described knowledge, the ratio L / λ between the length L of the two antenna elements and the wavelength λ of the radio wave is in the range of 0.2 to 0.9, and the specific line segment is The inclination angle φ in the rotation direction of the radio wave in the direction of the line segment f between each antenna element is 15 ° or more and 120 ° or less, preferably 25 ° or more and 90 ° or less, more preferably 40 ° or more and 75 °. By making the following, the communication distance in the radio frequency RFID tag system can be extended.

  When using both counterclockwise and clockwise readers for the rotation direction of the radio wave, either one of the inclination angles φ1 and φ2 shown in FIG. 9 of the two antenna elements is within the range of the inclination angle φ. What is necessary is just to expand the freedom degree of arrangement | positioning etc. with respect to two antenna elements which can extend communication distance.

  When the length of the line segment of the specific partner is M, the difference MH between the length M of the line segment of the specific partner and the length H of the antenna of the RFID tag By making it fall within the range of −0.4λ to 0.7λ, preferably −0.3λ to 0.5λ, more preferably −0.2λ to 0.4λ with respect to the wavelength λ, The communication distance can be further extended.

  When the length H of the antenna of the RFID tag is less than 0.2λ with respect to the wavelength λ of the radio wave, the length L is 0.2λ to 0.4λ with respect to the wavelength λ of the radio wave. The length difference MH may be in the range of −0.2λ to 0.2λ. If the antenna has a length H shorter than 0.2λ, such as a small article or an article where the RFID tag is attached, such as a CD or DVD, such a booster antenna It is recommended to install the antenna element.

  The distance Z from the center C of the antenna of the RFID tag to the plane on which the antenna element is arranged is in the range of 0.3λ or less, preferably in the range of 0.2λ or less, more preferably in relation to the wavelength λ of the radio wave. The communication distance can be further extended by making the range of 0.1λ or less.

  The distance R from the center C of the antenna of the RFID tag to the midpoint of the line segment of the specific partner is in the range of 0.3λ or less, preferably in the range of 0.2λ or less with respect to the wavelength λ of the radio wave, The communication distance can be further extended by preferably setting the range to 0.1λ or less.

  When the antenna of the RFID tag has only one set of two points that determine the length H and has a longitudinal direction, the direction of the line segment of the specific partner and the plane on which the antenna element is arranged The communication distance can be further extended by setting the absolute value of the angle α formed with the antenna direction of the RFID tag projected onto the antenna to 70 ° or less, preferably 45 ° or less, more preferably 30 ° or less. Can do.

  When the antenna of the RFID tag has only one set of two points that determine the length H and has a longitudinal direction, the length of the antenna of the RFID tag projected on the plane on which the antenna element is arranged The inclination angle β in the direction of rotation of the radio wave of the direction of the line segment extending from the base end point to connect the tip end point to the direction of the direction is 10 ° or more and 130 ° or less, preferably 25 The communication distance can be further extended by setting the angle to be not less than 90 ° and not more than 90 °, more preferably not less than 40 ° and not more than 75 °.

  The center of gravity G of each of the two antenna elements is located on the opposite side of the line segment between the specific counterparts in a plane where each antenna element is arranged with respect to a straight line obtained by extending the line segment between the two antenna elements. Alternatively, it may be positioned on the line segment between itself.

  When the RFID tag is attached to an article housed in a case that transmits radio waves or the case, the two antenna elements may be attached to the case.

  A plurality of the RFID tags are attached to the article or case, and the center C of the antenna of at least one RFID tag is set to the wavelength λ of the radio wave from the midpoint of the line between specific counterparts of the two antenna elements. By providing a means for inhibiting radio wave communication from the reader antenna with respect to the antenna of another RFID tag that is located at a distance of 0.3λ or less relative to this position, a desired RFID tag is provided. Communication with can be specified. A means for blocking communication with respect to the antenna of another RFID tag is not particularly limited, but a plate-like conductor is disposed between the antenna of the other RFID tag and the antenna of the reader to block the primary radio wave. Method, a circular conductor having a length of about ½ of the wavelength of the radio wave, a circular conductor such as a cross, or a cross-shaped conductor such as a cross is disposed between the antenna of another RFID tag and the reader antenna. A method of weakening the radio wave received by the RFID tag due to interference between the radio wave and the primary radio wave, a method of arranging a conductor that emits a secondary radio wave that weakens the primary radio wave by other methods, and the like can be adopted.

  The case that transmits the radio wave may be a cardboard box.

  The antenna element is mounted on the surface of the corrugated sheet that overlaps the corrugated sheet of the flap part, joint part or joint extension part of the corrugated sheet forming the corrugated cardboard box, so that the antenna element is box-formed after box making. It can be arranged at a position sandwiched between the corrugated cardboard sheets, and can be prevented from coming off due to contact or friction with an article or the like.

  The antenna element can be attached to a secondary material such as a sealing tape for the case.

  The antenna element may be formed by applying conductive ink or conductive paste.

The RFID tag booster antenna of the present invention is connected to an IC chip of a radio frequency RFID tag that receives and responds to a radio wave having a rotating circularly polarized component from an antenna of a reader as an interrogator, and has a length H and a center. At least two straight lines, an open curve, a closed curve, or C arranged on one plane facing the reader antenna on the same side as the RFID tag antenna, separated from the antenna defined as follows: These linear antenna elements are formed by intersecting lines or curves, and when the length L, width W, and center of gravity G of these linear antenna elements are defined as follows, The ratio L / W of the length L to the width W is 2 or more, and there is only one set of points a1 and a2 at both ends in the length direction of the antenna element in the definition of the length L below. The length L of the radio wave with respect to the wavelength λ is in the range of 0.2λ to 0.9λ, and for any of the two antenna elements, one of the points a1 and a2 at both ends of one antenna element itself. The direction of the four line segments between the other ends extending from the base point to either of the points a1 and a2 at both ends of the other antenna element, with the point at one end as the base point and the point at the other end as the tip point The direction of the line segment between itself extending from the base end point to connect the tip point of itself to the rotation direction of the radio wave has an inclination angle φ in the direction of rotation of at least four different line segments With respect to the line segment, the communication distance is set to 15 ° or more and 120 ° or less, so that the communication distance in the radio frequency RFID tag system can be greatly extended.
(Definitions regarding RFID tag antennas)
Length H: The maximum value of the linear distance between any two points on the antenna connected to the IC chip is defined as length H.
Center C: The center C is the midpoint between two points where the straight line distance is the maximum in the definition of length H.
(Definitions regarding antenna elements)
Length L: Two arbitrary points i and j are selected on the linear antenna element, and the traveling direction of the path from point i to point j along the antenna element with respect to vector Vij from point i to point j Point i and point j are connected without returning when the angle formed by the direction of the vector Vij and the direction of the vector Vij is within ± 90 ° at all points in the path. Of the combination of two arbitrary points i and j, the two points having the longest linear distance between the two points i and j are the points a1 and a2 at both ends in the length direction, and the antenna element between these points a1 and a2 The length of the shortest path along the line is defined as a length L.
Width W: When there are a plurality of points of the antenna element on an arbitrary straight line parallel to the straight line (width direction) and the straight line connecting the points a1 and a2 at both ends in the definition of the length L, the plurality of points The two points having the longest distance in the width direction are the points b1 and b2 at both ends in the width direction, the length of the shortest path along the antenna element between these points b1 and b2, and the straight line between the points b1 and b2 The minimum value of the length π / 2 times the distance and the minimum length L is w1, and these two arbitrary straight lines intersecting the antenna element are parallel to the straight line connecting the points a1 and a2 at both ends. When the smaller value of the maximum distance between two straight lines and the length L is w2, the larger value of w1 and w2 is the width W.
Center of gravity G: The center of gravity of the strands existing in all the shortest paths between the points a1 and a2 at both ends in the definition of the length L is defined as the center of gravity G.

1 is a schematic perspective view of an RFID tag system in which a booster antenna for an RFID tag according to a first embodiment is arranged. a and b are enlarged plan views showing the arrangement of the booster antenna in FIG. The schematic diagram which shows the distance Z from the gravity center of the antenna of FIG. 1 to the front surface of the case which has arrange | positioned the antenna element a and b are plan views showing enlarged arrangements of the booster antennas of the second embodiment, respectively. a and b are enlarged plan views showing the arrangement of the booster antenna according to the third embodiment. The schematic plan view of the RFID tag system which has arrange | positioned the booster antenna for RFID tags of 4th Embodiment. FIGS. 4A to 4D are schematic views showing modifications of the mounting position of the booster antenna to the case of the cardboard box of FIG. a to f are plan views showing examples of linear antenna elements, respectively. a to d are plan views for explaining a line segment e between two antenna elements, a line segment f between the two antenna elements, and an inclination angle φ in the rotation direction of the radio wave.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 3 show a first embodiment. FIG. 1 is a schematic diagram of a radio wave type RFID tag system in which a RFID tag booster antenna 2 according to the present invention is arranged in a case 12 in which an article 11 to which an RFID tag 1 is attached is stored. This schematic diagram shows only one article 11 in the case 12 for easy understanding, and the antenna 1 a of the RFID tag 1 is connected to the IC chip 1 b and is connected to the antenna 3 a of the reader 3. The booster antenna 2 is mounted on the front surface 12a of the case 12 facing the radio wave radiation direction. The booster antenna 2 is mounted on the front surface 11a of the article 11 facing the radio wave radiation direction. From the antenna 3 a of the reader 3, a microwave having a rotating circular polarization component and having a frequency of 2.4 GHz or a very high frequency wave having a frequency of 900 MHz is transmitted toward the RFID tag 1.

  The case 12 is a corrugated cardboard box that transmits radio waves, and the booster antenna 2 is formed of a linear antenna element 2a formed by applying conductive ink or conductive paste on the inner surface or outer surface of the front surface 12a. The antenna element 2a may be formed of a conductive metal wire such as aluminum, and may be mounted and disposed on a flap portion, a joint portion, a joint extension portion, or the like of a cardboard box, as will be described later. .

  In this embodiment, as shown in an enlarged view in FIG. 2, the antenna element 2a arranged on the front surface 12a of the case 12 is formed by two linear antenna elements 2a having the same length L and width W, The linear antennas 1a connected to the IC chip 1b on the rear side are arranged in parallel to each other so as to be close to both sides. The length L defined as the length of the shortest path between the points a1 and a2 at both ends of the antenna element 2a is in the range of 0.2λ to 0.9λ with respect to the wavelength λ of the radio wave from the antenna 3a of the reader 3. The width W defined as described above is equal to the width of the strand, and the ratio L / W between the length L and the width W is sufficiently larger than 2.

  FIG. 2 (a) shows that the two parallel antenna elements 2a are inclined to the lower right and connect the point a1 at the upper end of the right antenna element 2a and the point a2 at the lower end of the left antenna element 2a. The state where the line segment e overlaps with the antenna 1a projected on the front surface 12a is shown. In this state, when the rotation direction of the radio wave is counterclockwise, the line segment e between the opponents becomes the specific partner line segment e1, and the line between itself connecting the points a1 and a2 at both ends of each antenna element 2a. The inclination angle φ1 in the direction of rotation of the radio wave with respect to the direction of the specific partner line segment e1 in the direction of the minute f is 15 ° or more and 120 ° or less. When the direction of rotation of the radio wave is clockwise, the partner line segment e2 connecting the lower end point a2 of the right antenna element 2a and the upper end point a1 of the left antenna element 2a becomes the specific partner line segment e2. Thus, the inclination angle φ2 of the radio wave in the rotation direction with respect to the direction of the specific partner line segment e2 in the direction of the line segment f between itself is 15 ° or more and 120 ° or less. Note that the center of gravity G of each straight antenna element 2a is located on the line segment f between itself.

  FIG. 2 (b) shows the two parallel antenna elements 2a slanting to the right and connecting the point a2 at the lower end of the right antenna element 2a and the point a1 at the upper end of the left antenna element 2a. The state where the line segment e overlaps with the antenna 1a projected on the front surface 12a is shown. In this state, when the direction of rotation of the radio wave is clockwise, this partner line segment e becomes the specific partner line segment e2 and the line segment between itself connecting the points a1 and a2 at both ends of each antenna element 2a. The inclination angle φ2 of the radio wave in the rotation direction with respect to the direction of the specific partner line segment e2 in the direction of f is 15 ° or more and 120 ° or less. When the direction of rotation of the radio wave is counterclockwise, the line segment e between the opponents connecting the upper point a1 of the right antenna element 2a and the lower point a2 of the left antenna element 2a is a specific partner line segment. e1, and the inclination angle φ1 of the direction of each inter-segment line f in the direction of rotation of the radio wave with respect to the direction of the specific inter-segment line segment e1 is 15 ° or more and 120 ° or less.

  2 (a) and 2 (b) show that the antenna 1a connected to the IC chip 1b extends in the vertical direction, and the antenna 1a projected on the front surface 12a overlaps the line segments e1 and e2 between the specific opponents. The state where the center C is at the reference rotational position that coincides with the midpoint of the line segments e1 and e2 between the specific partners is shown. In the state where the antenna 1a is at the reference rotational position, in the case of FIG. 2A, the angle α formed by the direction of the line segment e1 between the specific opponents and the longitudinal direction of the antenna 1a is 0 °, and the longitudinal direction of the antenna 1a The inclination angle β in the counterclockwise rotation direction of the radio wave with respect to the direction of each self line segment f is equal to the inclination angle φ1, and in the case of FIG. The angle α formed between the direction and the longitudinal direction of the antenna 1a is 0 °, and the inclination angle β of the direction of each intersegment f with respect to the longitudinal direction of the antenna 1a in the clockwise rotation direction of the radio wave is the inclination angle It becomes equal to φ2.

  FIG. 3 is a schematic diagram for explaining the distance Z from the center C of the antenna 1a to the front surface 12a of the case 12 in which the antenna element 2a is arranged. The antenna 1a has a distance Z = 0 mm, that is, a state in which the front surface 11a of the article 11 to which the antenna 1a is attached is superimposed on the front surface 12a of the case 12 as a reference front-rear position. In a state where the antenna 1a is in the reference rotation position and the reference back-and-forth position, the distance R from the center C of the antenna 1a to the midpoint of the specific opponent line segments e1 and e2 is also 0 mm.

  In the communication test of each embodiment described below, unless otherwise specified, the antenna 1a is set to the reference rotation position and the reference front-rear position, and the antenna 1a is moved around the center C from the reference rotation position only in some communication tests. It was rotated to the left or right, moved backward (Z> 0 mm) from the reference front / rear position, or moved forward (Z <0 mm). The width of the strand of the straight antenna element 2a used in each of the following communication tests was 0.5 mm.

  The radio wave from the antenna 3a of the reader 3 is a circularly polarized microwave rotating counterclockwise, and as shown in FIG. 2, two linear antenna elements 2a are arranged on the front surface 12a, and the reader A first communication test for investigating a communication distance between the RFID tag 3 and the RFID tag 1 was performed. As shown in FIG. 1, the antenna 3a of the reader 3 is moved to a position in the front direction of the case 12, a position of ± 45 ° in the vertical direction from the front direction, and a position of ± 45 ° in the horizontal direction from the front direction. Then, the average communication distance obtained by averaging the communication distances at each of these moving positions was obtained, and the degree of extension of the communication distance was evaluated with the magnification of the communication distance with 1 when there is no booster antenna. However, under some conditions where the communication distance is short, only the front communication distance when the antenna 3a of the reader 3 is set to the front direction position is measured, and the communication distance without the booster antenna is close to 0 cm. The communication distance magnification was omitted.

  First, a 1-1 communication test was performed in which the two antenna elements 2a were rotated to change the inclination angle φ1. Depending on the magnitude of the inclination angle φ1, the inclination of each antenna element 2a may be on the upper right. In the 1-1 communication test, the length H of the antenna 1a of the RFID tag 1 is changed to three stages of 56 mm, 34 mm, and 11 mm, and the length H is 56 mm. Was changed in three steps within a range of 0.2λ to 0.9λ with respect to the wavelength λ (= 125 mm) of the microwave. Further, according to the length H of each antenna 1a, the length M of the specific partner line segment e1 is set such that when the length H is 0.2λ or more, the length difference M−H is −0.4λ˜ When the length H is less than 0.2λ, the length difference M−H is set within the range of −0.2λ to 0.2λ.

  Tables 1 (a) to (c) show the results of the 1-1 communication test. Table 1 (a) shows H = 56 mm (0.45λ), M = 60 mm, M−H = 4 mm (0.03λ), and Table 1 (b) shows H = 34 mm (0.27λ), M = 40 mm. In the case of M−H = 6 mm (0.05λ), Table 1 (c) shows the case of H = 11 mm (0.09λ), M = 8 mm, and M−H = −3 mm (−0.02λ). For Table 1 (c) in which the length H of the antenna 1a was 11 mm, the communication distance was evaluated by the front communication distance, and the communication distance without the booster antenna was close to 0 cm, so the communication distance magnification was omitted. . For the length L and the length difference MH in the following tables, the length of the radio wave with respect to the wavelength λ is also shown in parentheses.

  From this test result, the communication distance is extended in any of the examples in which the inclination angle φ is 15 ° or more and 120 ° or less regardless of the length H of the antenna 1a. Among these, the inclination angle φ1 When the angle is 25 ° or more and 90 ° or less, the communication distance is remarkably extended, and when the angle is 40 ° or more and 75 ° or less, the communication distance is further extended. On the other hand, in the comparative example in which the inclination angle φ1 is out of the above range, the communication distance is not extended or the extension is small even when it is extended. In addition, in the 1-1 communication test, a test was performed in which the width of the wire of the antenna element 2a was changed to 0.1 to 0.2 mm and 5 mm or more, and the results are shown in Tables 1 (a) to (c). A communication result similar to that obtained when the wire width was 0.5 mm was obtained.

  Next, a 1-2 communication test was performed by changing the length L of the two linear antenna elements 2a while setting the inclination angle φ1 to 15 ° to 120 °. In the 1-2 communication test, when the length H of the antenna 1a is changed in four stages of 56 mm, 34 mm, 11 mm, and 5 mm, and the length H is 56 mm and 34 mm, the inclination angle φ1 is 45 ° and 63 °. In the case where the length H is 11 mm and 5 mm, the inclination angle φ1 is 45 °. Further, the difference MH between the length M of the specific partner line segment e1 and the length H of the antenna 1a is 56 mm (0.45λ) and 34 mm (0. 27λ) is in the range of −0.4λ to 0.7λ, and the length H is less than 0.2λ and is 11 mm (0.09λ) and 5 mm (0.04λ). It was made to fall within the range of 0.2λ to 0.2λ.

  Tables 2 (a) to (d) show the results of the 1-2 communication test. Table 2 (a) is H = 56 mm and M = 60 mm. Table 2 (b) is H = 34 mm and M = 40 mm. Table 2 (c) is H = 11 mm and M = 8 mm. (D) is a case where H = 5 mm and M = 4 mm. Tables 2 (c) and 2 (d) in which the length H of the antenna 1a was 11 mm and 5 mm were evaluated based on the front communication distance, and the communication distance magnification was omitted.

  From this test result, when the length H of the antenna 1a is 0.2λ or more, the communication distance is extended over a wide range where the length L of the antenna element 2a with respect to the wavelength λ of the microwave is 0.2λ to 0.9λ. I understand that. When the length H of the antenna 1a is less than 0.2λ, the communication distance is greatly extended in the range of 0.2λ to 0.4λ where the length L is outside 0.5λ.

  Next, the length L of the antenna element 2a is set to a range of 0.2λ to 0.9λ, and the difference MH between the length M of the specific partner line segment e1 and the length H of the antenna 1a is set. The changed 1-3 communication test was conducted. In the 1-3 communication test, the length H of the antenna 1a was changed to four stages of 56 mm, 34 mm, 11 mm, and 5 mm, and the length M of the specific partner line segment e1 was changed with respect to each length H. . Further, an inclination angle φ1 of 90 ° was added only for an inclination angle φ1 of 45 ° and a length H of the antenna 1a of 56 mm.

  Tables 3 (a) to (d) show the results of the 1-3 communication test. Table 3 (a) is H = 56 mm, L = 60 mm, Table 3 (b) is H = 34 mm, L = 60 mm, Table 3 (c) is H = 11 mm, L = 40 mm, and Table 3 (d) is H = In this case, 5 mm and L = 40 mm. For Tables 3 (c) and 3 (d) where the length H of the antenna 1a was 11 mm and 5 mm, the communication distance was evaluated by the front communication distance, and the magnification of the communication distance was omitted.

  From this test result, when the length H of the antenna 1a is 0.2λ or more, the communication distance is extended in the range where the length difference M−H is −0.4λ to 0.7λ, and the length of the antenna 1a is increased. When H is less than 0.2λ, it can be seen that the communication distance is extended when the length difference M−H is in the range of −0.2λ to 0.2λ.

  Next, the antenna 1a is moved from the reference front-rear position (Z = 0 mm) in the front-rear direction (the rearward direction is positive), and the distance Z from the center C to the front surface 12a of the case 12 where the antenna element 2a is disposed is changed. The first to fourth communication tests were performed. In the first to fourth communication tests, the length H of the antenna 1a is 56 mm, the length L of the antenna element 2a is 60 mm, the length M of the line segment e1 of the specific partner is 60 mm, and the inclination angle φ1 is 45 ° and 90 °. It was changed to two stages. The antenna 1a was also moved in the left and right X directions and the upper and lower Y directions shown in FIG.

  Table 4 shows the results of the 1-4 communication test. In the table, the movement position in the X direction (right direction is positive) and the Y direction (upward direction is positive) and the distance R from the center C of the antenna 1a to the midpoint of the specific partner line segment e1 are also shown. From this test result, the absolute value of the distance Z from the center C of the antenna 1a to the plane on which the antenna element 2a is arranged, and the distance R from the center C of the antenna 1a to the midpoint of the specific partner line segment e1 are 0. It can be seen that the communication distance is extended when it is 3λ (= 37.5 mm) or less.

  Next, the first to fifth communication tests were performed in which the antenna 1a was rotated about the center C from the reference rotation position, and the angle α formed by the direction of the antenna 1a and the specific partner line segment e1 was changed. . In the 1-5 communication test, the length H of the antenna 1a was 56 mm, the length L of the antenna element 2a was 60 mm, the length M of the line segment e1 between the specific opponents was 60 mm, and the inclination angle φ1 was 63 °.

  Table 5 shows the results of the 1-5 communication test. In the table, with respect to the longitudinal direction of the antenna 1a projected on the front surface 12a on which the antenna element 2a is disposed, the direction of the line segment f between itself extending so as to connect the tip point of the antenna 1a is connected. The inclination angle β in the direction of rotation of the radio wave is also shown. From this test result, the communication distance is extended when the absolute value of the angle α (positive when the antenna 1a is rotated counterclockwise) is 70 ° or less and the inclination angle β is 10 ° or more and 130 ° or less. You can see that.

  The radio wave from the antenna 3a of the reader 3 is a circularly polarized ultra high frequency wave (λ = 333 mm) rotating counterclockwise, and as shown in FIG. 2, two linear antenna elements 2a are placed on the front surface 12a. A second communication test was conducted in which the communication distance between the reader 3 and the RFID tag 1 was investigated. In the second communication test, the antenna 3a of the reader 3 is fixed at a position 20 cm away from the front surface 12a in the front direction of the case 12 shown in FIG. 1, and the strength of the radio wave received by the antenna 1a of the RFID tag 1 is set. Measurement was made to evaluate the degree of extension of the communication distance with the magnification of the radio wave intensity, which is 1 when there is no booster antenna.

  First, a 2-1 communication test was performed in which the two antenna elements 2a were rotated to change the inclination angle φ1. In the 2-1 communication test, the length H of the antenna 1a of the RFID tag 1 is 68 mm (0.20λ), the length L of the antenna element 2a is 160 mm (0.48λ), and the length of the specific partner line segment e1. M was 60 mm.

  Table 6 shows the results of the 2-1 communication test. From this test result, even when the radio wave from the antenna 3a of the reader 3 is an ultra-short wave, all of the examples in which the inclination angle φ1 is 15 ° or more and 120 ° or less are strong in the radio wave. The communication distance is extended. On the other hand, in the comparative example in which the inclination angle φ1 is outside the above range, the strength of the radio wave is not so strong.

  Next, a 2-2 communication test was performed in which the length L of the two straight antenna elements 2a was changed. In the 2-2 communication test, the length H of the antenna 1a was 68 mm, the inclination angle φ1 was 45 °, and the length M of the specific partner line segment e1 was 60 mm.

  Table 7 shows the results of the 2-2 communication test. From this test result, even when the radio wave from the antenna 3a of the reader 3 is an ultrashort wave, if the length H of the antenna 1a is 0.2λ or more, the length L of the antenna element 2a with respect to the wavelength λ of the ultrashort wave is The strength of the radio wave is strong within the range of 0.2λ to 0.9λ.

  Next, a 2-3 communication test was performed in which the length difference MH between the length M of the specific partner line segment e1 and the length H of the antenna 1a was changed. In the 2-3 communication test, the length H of the antenna 1a was 68 mm, the length L of the antenna element 2a was 160 mm, the inclination angle φ1 was 45 °, and the length M of the specific partner line segment e1 was changed.

  Table 8 shows the result of the 2-3 communication test. From this test result, even when the radio wave from the antenna 3a of the reader 3 is an ultra-short wave, when the length H of the antenna 1a is 0.2λ or more, the length difference MH is −0.4λ-0. The intensity of radio waves is strong in the range of 7λ.

  The radio wave from the antenna 3a of the reader 3 is a circularly polarized microwave rotating clockwise, and two linear antenna elements 2a are arranged on the front surface 12a as shown in FIG. And a third communication test was conducted to investigate the communication distance between the RFID tag 1 and the RFID tag 1. In the third communication test, the front communication distance is measured with the antenna 3a of the reader 3 as the position in the front direction of the case 12 shown in FIG. The extent of distance extension was evaluated.

  First, a 3-1 communication test was performed in which the two antenna elements 2a were rotated to change the inclination angle φ2. In the 3-1 communication test, the length H of the antenna 1a of the RFID tag 1 is 51 mm, the length L of the antenna element 2a is 60 mm (0.48λ), and the length M of the specific partner line segment e2 is 80 mm. .

  Table 9 shows the results of the 3-1 communication test. From this test result, even when the radio wave from the antenna 3a of the reader 3 is a microwave that rotates clockwise, all of the examples in which the inclination angle φ2 is 15 ° or more and 120 ° or less have a communication distance. In the comparative example which is extended and the inclination angle φ2 is out of the above range, the communication distance is not extended.

  Next, a 3-2 communication test was performed in which the length L of the two linear antenna elements 2a was changed. In the 3-2 communication test, the length H of the antenna 1a was 51 mm (0.41λ), the inclination angle φ2 was 45 °, and the length M of the specific partner line segment e2 was 60 mm.

  Table 10 shows the results of the 3-2 communication test. From this test result, even when the radio wave from the antenna 3a of the reader 3 is a microwave that rotates clockwise, when the length H of the antenna 1a is 0.2λ or more, the antenna element 2a with respect to the wavelength λ of the microwave The communication distance is extended within the range of the length L of 0.2λ to 0.9λ.

  Next, a third communication test 3-3 was performed by changing the length difference MH between the length M of the specific partner line segment e2 and the length H of the antenna 1a. In the third 3-3 communication test, the length H of the antenna 1a was 51 mm, the length L of the antenna element 2a was 60 mm, the inclination angle φ1 was 45 °, and the length M of the specific partner line segment e2 was changed.

  Table 11 shows the results of the 3-3 communication test. From this test result, even when the radio wave from the antenna 3a of the reader 3 is a microwave that rotates clockwise, if the length H of the antenna 1a is 0.2λ or more, the length difference MH is − The communication distance is extended in the range of 0.4λ to 0.7λ.

  FIG. 4 shows a second embodiment. In this embodiment, as shown in an enlarged view in FIGS. 4A and 4B, two antenna elements 2a arranged on the front surface 12a are L-shaped antennas having the same length L and width W. Longitudinal vertical sides formed by the element 2a and arranged symmetrically with respect to the center C of the linear antenna 1a connected to the IC chip 1b behind it, and one side of each L-shape is parallel to each other (Length L1), the other side is a horizontal side (length L2) parallel to each other. The length L (= L1 + L2) defined as the length of the shortest path between the points a1 and a2 at both ends of the antenna element 2a is 0.2λ to 0. 0 with respect to the wavelength λ of the radio wave from the antenna 3a of the reader 3. The ratio L / W with respect to the width W defined as described above in the range of 9λ is 2 or more.

  In FIG. 4A, the two L-shaped antenna elements 2a are arranged with respect to the antenna 1a such that the right side of the right antenna element 2a is located at the upper right and the left side of the left antenna element 2a is located at the lower left. The line segment e between the opposite ends of each antenna element 2a extending up and down from the far end with respect to the antenna 1a on the horizontal side and connecting the near end point a1 with respect to the antenna 1a on the horizontal side of each antenna element 2a is projected onto the front surface 12a In this state, the antenna 1a is overlapped. In this state, when the direction of rotation of the radio wave is counterclockwise, the line segment e between the opponents becomes the specific partner line segment e1, and the line between itself connecting the points a1 and a2 at both ends of each antenna element 2a. The inclination angle φ1 in the direction of rotation of the radio wave with respect to the direction of the specific partner line segment e1 in the direction of the minute f is 15 ° or more and 120 ° or less. When the direction of rotation of the radio wave is clockwise, the line segment e between the opponents connecting the point a2 at the vertical edge of the right antenna element 2a and the point a2 at the vertical edge of the left antenna element 2a is the specific partner. The inclination angle φ2 of the radio wave in the rotation direction with respect to the direction of the specific partner line segment e2 in the direction of the line segment f2 between the self lines is 15 ° or more and 120 ° or less. In any case, the center of gravity G of each antenna element 2a is defined by the line segments e1 and e2 between the specific opponents in the front surface 12a on which each antenna element 2a is arranged with respect to a straight line obtained by extending the line segment f between itself. Located on the opposite side.

  In FIG. 4B, the two L-shaped antenna elements 2a are arranged such that the horizontal side of the right antenna element 2a is at the lower right and the horizontal side of the left antenna element 2a is at the upper left with respect to the antenna 1a. A line segment e between the opposite ends of each antenna element 2a extending up and down from the far end with respect to the antenna 1a on the lateral side and connecting the point a1 at the near end with respect to the antenna 1a on the lateral side of each antenna element 2a is formed on the front surface 12a. In this state, the projected antenna 1a overlaps the projected antenna 1a. In this state, when the rotation direction of the radio wave is clockwise, the line segment e between the opponents becomes the specific partner line segment e2, and the line segment between itself connecting the points a1 and a2 at both ends of each antenna element 2a. The inclination angle φ2 of the radio wave in the rotation direction with respect to the direction of the specific partner line segment e2 in the direction of f is 15 ° or more and 120 ° or less. When the direction of rotation of the radio wave is counterclockwise, the line segment e between the other ends connecting the point a2 at the vertical side end of the right antenna element 2a and the point a2 at the vertical side end of the left antenna element 2a is specified. The angle line φ1 of the rotation direction of the radio wave with respect to the direction of the specific line segment e1 of each partner line segment f1 is 15 ° or more and 120 ° or less. Also in this modification, the center of gravity G of each antenna element 2a has a line segment e1 between specific opponents within the front surface 12a on which each antenna element 2a is arranged with respect to a straight line obtained by extending the line segment f between itself. Located on the opposite side of e2.

  4 (a) and 4 (b) show that the antenna 1a connected to the IC chip 1b extends in the vertical direction, and the antenna 1a projected on the front surface 12a overlaps the line segments e1 and e2 between the specific opponents. The state where the center C is at the reference rotational position that coincides with the midpoint of the line segments e1 and e2 between the specific partners is shown. In the state where the antenna 1a is at the reference rotational position, in the case of FIG. 4A, the angle α formed between the direction of the line segment e1 of the specific partner and the longitudinal direction of the antenna 1a is 0 °, and the longitudinal direction of the antenna 1a The inclination angle β of the direction of each inter-segment line f with respect to the direction of the radio wave in the counterclockwise rotation direction of the radio wave is equal to the inclination angle φ1, and in the case of FIG. The angle α formed between the direction and the longitudinal direction of the antenna 1a is 0 °, and the inclination angle β of the direction of each intersegment f with respect to the longitudinal direction of the antenna 1a in the clockwise rotation direction of the radio wave is the inclination angle It becomes equal to φ2. Although not shown, the reference front-rear position of the antenna 1a is a position where the distance Z from the center C to the front surface 12a of the case 12 where the antenna element 2a is disposed is 0 mm, as in the first embodiment. did.

  Also in this embodiment, in the communication test of each example described below, unless otherwise specified, the antenna 1a is set to the reference rotation position and the reference front / rear position, and the antenna 1a is moved from the reference rotation position only in a part of the communication tests. It was rotated around the center C to the left or right, or moved backward (Z> 0 mm) or moved forward (Z <0 mm) from the reference front / rear position. The width of the strand of the L-shaped antenna element 2a used in each of the following communication tests was 5 mm.

  The radio wave from the antenna 3a of the reader 3 is a circularly polarized microwave that rotates counterclockwise, and two L-shaped antenna elements 2a are placed on the front surface as shown in FIG. The 4th communication test which investigates the communication distance between the reader | leader 3 and RFID tag 1 was arrange | positioned at 12a. As shown in FIG. 1, the antenna 3a of the reader 3 is moved to a position in the front direction of the case 12, a position of ± 45 ° in the vertical direction from the front direction, and a position of ± 45 ° in the horizontal direction from the front direction. Then, the average communication distance obtained by averaging the communication distances at each of these moving positions was obtained, and the degree of extension of the communication distance was evaluated with the magnification of the communication distance with 1 when there is no booster antenna. However, under some conditions, only the front communication distance when the antenna 3a of the reader 3 is positioned in the front direction is measured, and the communication distance when the booster antenna is not present is close to 0 cm, the magnification of the communication distance Was omitted.

  First, a 4-1 communication test was performed in which the inclination angle φ1 of the two antenna elements 2a was changed. The inclination angle φ1 was varied by changing the combination of the L-shaped vertical and horizontal lengths L1 and L2 and the vertical extension direction of the vertical sides. In the 4-1 communication test, the length H of the antenna 1a of the RFID tag 1 is 56 mm (0.45λ), the length M of the line segment e1 of the specific partner is 60 mm, and the length L of the antenna element 2a is 56 mm ( 0.45λ) and 71 mm (0.57λ).

  Table 12 shows the results of the 4-1 communication test. In the table, the L-shaped vertical and horizontal lengths L1 and L2 of the antenna element 2a and the extending direction of the vertical sides are also shown. The extending direction of the vertical side is indicated by the sign L1, and the negative sign means extending in a direction away from the antenna 1a. From this test result, even in the case where the antenna element 2a is L-shaped, the examples in which the inclination angle φ1 is 15 ° or more and 120 ° or less are all extended in communication distance, and the inclination angle φ1 is In the comparative example outside the above range, the communication distance is not extended. In the 4-1 communication test, a test was performed in which the width of the strand of the antenna element 2a was changed to 0.1 to 0.2 mm, 0.5 mm, and 10 mm or more. Communication results similar to those obtained when the width was 5 mm were obtained.

  Next, a 4-2 communication test was performed in which the length L of the two linear antenna elements 2a was changed. The length L was changed by changing the combination of the lengths L1 and L2 of the vertical and horizontal sides of the L shape within the range where the inclination angle φ is 15 ° or more and 120 ° or less. In the 4-2 communication test, the length H of the antenna 1a was 56 mm (0.45λ), and the length M of the specific partner line segment e1 was 60 mm.

  Table 13 shows the results of the 4-2 communication test. From this test result, even when the antenna element 2a is L-shaped, the length L of the antenna element 2a with respect to the wavelength λ of the microwave is 0. The communication distance is extended over a wide range from 2λ to 0.9λ.

  Next, a 4-3 communication test was performed in which the length difference MH between the length M of the specific partner line segment e1 and the length H of the antenna 1a was changed. In the 4th-3 communication test, the length H of the antenna 1a was set to 56 mm (0.45λ) and 11 mm (0.09λ), and the length M of the specific partner line segment e1 was changed. When the length H of the antenna 1a is 56 mm, the length L of the antenna element 2a is 55 mm (0.44λ; L1 = 35 mm, L2 = 20 mm), the inclination angle φ1 is 42 °, and the length of the antenna 1a When H was 11 mm, the length L of the antenna element 2a was 37 mm (0.30λ; L1 = 16 mm, L2 = 21 mm), and the inclination angle φ1 was 51 °.

  Tables 14 (a) and 14 (b) show the results of the 4-3 communication test. Table 14 (a) shows the case where H = 56 mm and L = 55 mm. Table 14 (b) shows the case where H = 11 mm and L = 37 mm. For Table 14 (b), the communication distance is evaluated by the front communication distance. The communication distance magnification was omitted. From this test result, even when the antenna element 2a is L-shaped, when the length H of the antenna 1a is 0.2λ or more, the length difference MH is −0.4λ to 0.7λ. When the length H is less than 0.2λ, the communication distance is extended when the length difference MH is in the range of −0.2λ to 0.2λ.

  Next, the antenna 1a is moved from the reference front-rear position (Z = 0 mm) in the front-rear direction (the rearward direction is positive), and the distance Z from the center C to the front surface 12a of the case 12 where the antenna element 2a is disposed is changed. The 4th-4th communication test was performed. In the fourth 4-4 communication test, the length H of the antenna 1a is changed in two stages of 56 mm and 34 mm, the length L of the antenna element 2a is 56 mm (0.45λ; L1 = 21 mm, L2 = 35 mm), and the inclination angle φ1. Was set to 58 °. The length M of the specific partner line segment e1 was 60 mm and 40 mm. The antenna 1a was also moved in the left and right X directions and the upper and lower Y directions shown in FIG.

  Tables 15 (a) and 15 (b) show the results of the 4th-4th communication test. Table 15 (a) shows the case where H = 56 mm and M = 60 mm, and Table 15 (b) shows the case where H = 34 mm and M = 40 mm. The distance R from the center C of 1a to the midpoint of the specific partner line segment e1 is also shown. From this test result, even when the antenna element 2a is L-shaped, the absolute value of the distance Z from the center C of the antenna 1a to the plane on which the antenna element 2a is arranged, and the specific partner from the center C of the antenna 1a. The communication distance is extended when the distance R to the midpoint of the line segment e1 is 0.3λ (= 37.5 mm) or less.

  Next, a fourth to fifth communication test was performed in which the antenna 1a was rotated around the center C from the reference rotation position, and the angle α formed by the direction of the antenna 1a and the specific partner line segment e1 was changed. . In the 4-5th communication test, the length H of the antenna 1a is changed in two stages of 56 mm and 34 mm, the length L of the antenna element 2a is 56 mm (0.45λ; L1 = 21 mm, L2 = 35 mm), and the inclination angle φ1. Was set to 58 °. The length M of the specific partner line segment e1 was 60 mm and 40 mm.

  Tables 16 (a) and 16 (b) show the results of the 4-5th communication test. Table 16 (a) shows the case where H = 56 mm and M = 60 mm, and Table 16 (b) shows the case where H = 34 mm and M = 40 mm. In the table, the line segment f between itself with respect to the direction of the antenna 1a is shown. The inclination angle β in the direction of rotation of the radio wave is also shown. From this test result, even when the antenna element 2a is L-shaped, the communication distance is extended when the absolute value of the angle α is 70 ° or less and the inclination angle β is 10 ° or more and 130 ° or less. ing.

  The radio wave from the antenna 3a of the reader 3 is a circularly polarized ultra high frequency wave (λ = 333 mm) that rotates counterclockwise, and as shown in FIG. 4A, two L-shaped A fifth communication test was conducted in which the antenna element 2a was placed on the front surface 12a and the communication distance between the reader 3 and the RFID tag 1 was investigated. In the fifth communication test, the antenna 3a of the reader 3 is fixed at a position 300 mm away from the front surface 12a in the front direction of the case 12 shown in FIG. 1, and the strength of the radio wave received by the antenna 1a of the RFID tag 1 is set. Measurement was made to evaluate the degree of extension of the communication distance with the magnification of the radio wave intensity, which is 1 when there is no booster antenna.

  First, a 5-1 communication test was performed in which the length difference MH between the length M of the specific partner line segment e1 and the length H of the antenna 1a was changed. In the 5-1 communication test, the length H of the antenna 1a is changed in three stages of 140 mm (0.42λ), 120 mm (0.36λ), and 68 mm (0.20λ), and the length L of the antenna element 2a is 160 mm. (0.48λ; L1 = 70 mm, L2 = 90 mm), the inclination angle φ1 was 56 °, and the length M of the specific mating line segment e1 was changed.

  Table 17 shows the results of the 5-1 communication test. From this test result, even when the radio wave from the antenna 3a of the reader 3 is an ultra-short wave, when the length H of the antenna 1a is 0.2λ or more, the length difference MH is −0.4λ-0. The intensity of radio waves is strong in the range of 7λ.

  Next, the antenna 1a is moved backward from the reference front-rear position (Z = 0 mm) to change the distance Z from the center C to the front surface 12a of the case 12 on which the antenna element 2a is disposed. A communication test was conducted. In the 5-2 communication test, the length H of the antenna 1a is 68 mm, the length L of the antenna element 2a is 160 mm (0.48λ; L1 = 70 mm, L2 = 90 mm), the inclination angle φ1 is 56 °, and Z = In the case of 3 mm, the antenna 1a was also moved in the left and right X directions and the upper and lower Y directions shown in FIG. The length M of the specific partner line segment e1 was 60 mm.

  Table 18 shows the results of the 5-2 communication test. In the table, the movement position in the X direction and the Y direction and the distance R from the center C of the antenna 1a to the midpoint of the specific partner line segment e1 are also shown. From this test result, even when the radio wave from the antenna 3a of the reader 3 is an ultra-short wave, the distance Z from the center C of the antenna 1a to the plane on which the antenna element 2a is disposed and the distance between the center C of the antenna 1a and the specific partner The communication distance is extended when the distance R to the midpoint of the line segment e1 is 0.3λ (= 100 mm) or less.

  The radio wave from the antenna 3a of the reader 3 is a circularly polarized microwave that rotates clockwise. As shown in FIG. 4B, two L-shaped antenna elements 2a are connected to the front surface 12a. The sixth communication test was conducted in which the communication angle between the reader 3 and the RFID tag 1 was investigated by changing the inclination angle φ2 of the two antenna elements 2a. The inclination angle φ2 was changed by changing the combination of the L-shaped vertical side and the horizontal side lengths L1 and L2 of the antenna element 2a. In the sixth communication test, the front communication distance when the antenna 3a of the reader 3 is positioned in the front direction of the case 12 shown in FIG. 1 is measured, and the communication distance is set to 1 when there is no booster antenna. The extent of distance extension was evaluated.

  In the sixth communication test, the length H of the antenna 1a of the RFID tag 1 is 51 mm, the length L of the antenna element 2a is 56 mm (0.45λ), the length M of the specific partner line segment e2 is 80 mm, The inclination angle φ2 was changed by changing the combination of the lengths L1 and L2 of the vertical and horizontal sides.

  Table 19 shows the results of the sixth communication test. From this test result, even when the radio wave from the antenna 3a of the reader 3 is a microwave that rotates clockwise, all of the examples in which the inclination angle φ2 is 15 ° or more and 120 ° or less have a communication distance. In the comparative example which is extended and the inclination angle φ2 is out of the above range, the communication distance is not extended.

  FIGS. 5A and 5B show a third embodiment. 5 (a), as shown in FIG. 2 (a), one linear antenna element 2a is added to both sides of the original two linear antenna elements 2a arranged on the front surface 12a. These additional antenna elements 2a arranged in parallel with the antenna 1a, FIG. 5 (b) shows the original two L-shaped antennas arranged on the front surface 12a as shown in FIG. 4 (a). One linear antenna element 2a is added to both sides of the element 2a, and the added antenna element 2a is arranged in parallel with the antenna 1a.

The radio wave from the antenna 3a of the reader 3 is a circularly polarized microwave that rotates counterclockwise, and as shown in FIG. 5A, four linear antenna elements 2a are arranged on the front surface 12a. As shown in FIG. 5 (b), between the reader 3 and the RFID tag 1, there are two L-shaped antenna elements 2a and two linear antenna elements 2a arranged on the front surface 12a. A seventh communication test was conducted to investigate the communication distance. As shown in FIG. 1, the antenna 3a of the reader 3 is moved to a position in the front direction of the case 12, a position of ± 45 ° in the vertical direction from the front direction, and a position of ± 45 ° in the horizontal direction from the front direction. As for the average communication distance and the front communication distance at each of these moving positions, the degree of extension of the communication distance was evaluated by the communication distance magnification with 1 when there is no booster antenna.

  In FIGS. 5A and 5B, the length H of the antenna 1a is 56 mm, and each of the additional straight antenna elements 2a has a length L of 50 mm and a distance from the antenna 1a projected on the front surface 12a of 75 mm, The length M of the specific mating line segment e1 is 60 mm, and in the case of FIG. 5A, the length L of each antenna element 2a of the original straight line is 60 mm (0.48λ) and the inclination angle φ1 is 54. In the case of FIG. 5B, the length L of the original L-shaped antenna element 2a was 56 mm (0.45λ; L1 = 21 mm, L2 = 35 mm), and the inclination angle φ1 was 58 °.

  Table 20 shows the results of the seventh communication test. In the table, the communication distance and the magnification when the additional antenna element 2a is not arranged are also shown. From this test result, it can be seen that the communication distance is longer in the case where the additional antenna element 2a is disposed than in the case where the additional antenna element 2a is not provided, and in particular, the degree of extension of the front communication distance is larger. . The number of additional antenna elements 2a is preferably two or more.

  FIG. 6 shows a fourth embodiment. In this embodiment, a plurality of articles 11 with the RFID tag 1 in which the same information is partially recorded are stored in the case 12. Similar to the first embodiment, the two antenna elements 2a of the booster antenna 2 are mounted on the front surface 12a of the case 12 facing the radiation direction of the radio wave from the antenna 3a of the reader 3. On the inner side, these RFID tags are used as means for inhibiting radio wave communication from the antenna 3a of the reader 3 with respect to the RFID tags 1 attached to the other articles 11 except for the articles 11 immediately behind the booster antenna 2. A plate-like conductor 4 that blocks radio waves from the antenna 3a of the reader 3 to the first antenna 1a is disposed. As a means for inhibiting communication of radio waves from the antenna 3a of the reader 3, a circle having a length of about ½ of the wavelength of the radio wave is provided between the antenna 1a of another RFID tag 1 and the antenna 3a of the reader 3. A method of weakening the radio wave received by the antenna 1a of the RFID tag 1 due to the interference between the secondary radio wave and the primary radio wave by arranging a ring-shaped conductor such as a rectangle or a cross, etc. A method of arranging a conductor that emits a secondary radio wave that weakens the secondary radio wave can also be adopted.

  FIGS. 7A to 7D show modifications of the mounting position of the booster antenna 2 to the case 12 of the cardboard box shown in FIG. FIG. 7A shows an example in which the booster antenna 2 is attached to the flap portion 13a of the cardboard sheet 13 forming the cardboard box, and FIG. 7B shows an example in which the booster antenna 2 is attached to the joint portion 13b of the cardboard sheet 13. (C) is an example in which the corrugated cardboard sheet 13 is mounted on the joint extension 13c, both of which are mounted on the overlapping surface side when the cardboard box is formed. As shown by dotted lines in the corrugated cardboard sheet 13 of FIGS. 7B and 7C, the booster antenna 2 can be mounted on a portion where the joint portion 13 and the joint extension portion 13c are overlapped. FIG. 7D shows an example in which the sealing tape 12b as an auxiliary material of the case 12 of the cardboard box is attached to the back surface or the front surface side.

  In each of the embodiments described above, the two antenna elements of the booster antenna are linear or L-shaped and have the same size, but the shape of these antenna elements is only one set of points a1 and a2 at both ends. The two antenna elements may have different linear dimensions or shapes as long as they exist.

DESCRIPTION OF SYMBOLS 1 RFID tag 1a Antenna 1b IC chip 2 Booster antenna 2a Antenna element 3 Reader 3a Antenna 4 Conductor 11 Article 11a Front surface 12 Case 12a Front surface 12b Sealing tape 13 Corrugated cardboard sheet 13a Flap portion 13b Joint portion 13c Joint portion extension

Claims (14)

An antenna connected to an IC chip of a radio frequency RFID tag that receives and responds to a radio wave having a rotating circularly polarized wave component from an antenna of a reader which is an interrogator, and whose length H and center C are defined as follows: And at least two straight lines, open curves, closed curves, or these straight lines or curves arranged on one plane facing the antenna of the reader on the same side as the antenna of the RFID tag. When the length L, width W, and center of gravity G of these linear antenna elements are defined as follows, the ratio of the length L to the width W of each antenna element L / W is 2 or more, and there is only one set of points a1 and a2 at both ends in the length direction of the antenna element in the definition of length L below, and the length L with respect to the wavelength λ of the radio wave from the antenna of the reader In either of the two antenna elements so as to fall within the range of 0.2λ to 0.9λ, one of the two points a1 and a2 of the one antenna element itself is a base point, the other From the base end point with respect to the direction of the four line segments between the opposite ends that extend from the base end point so as to connect any of the points a1 and a2 at the both ends of the other antenna element with the end point as the front end point The inclination angle φ in the direction of rotation of the radio wave of the direction of the line segment between itself extending so as to connect the tip points of its own is at least one of the specific line segments between the four partner lines. On the other hand, a booster antenna for an RFID tag that is 15 ° or more and 120 ° or less.
(Definitions regarding RFID tag antennas)
Length H: The maximum value of the linear distance between any two points on the antenna connected to the IC chip is defined as length H.
Center C: The center C is the midpoint between two points where the straight line distance is the maximum in the definition of length H.
(Definitions regarding antenna elements)
Length L: Two arbitrary points i and j are selected on the linear antenna element, and the traveling direction of the path from point i to point j along the antenna element with respect to vector Vij from point i to point j Point i and point j are connected without returning when the angle formed by the direction of the vector Vij and the direction of the vector Vij is within ± 90 ° at all points in the path. Of the combination of two arbitrary points i and j, the two points having the longest linear distance between the two points i and j are the points a1 and a2 at both ends in the length direction, and the antenna element between these points a1 and a2 The length of the shortest path along the line is defined as a length L.
Width W: When there are a plurality of points of the antenna element on an arbitrary straight line parallel to the straight line (width direction) and the straight line connecting the points a1 and a2 at both ends in the definition of the length L, the plurality of points The two points having the longest distance in the width direction are the points b1 and b2 at both ends in the width direction, the length of the shortest path along the antenna element between these points b1 and b2, and the straight line between the points b1 and b2 The minimum value of the length π / 2 times the distance and the minimum length L is w1, and these two arbitrary straight lines intersecting the antenna element are parallel to the straight line connecting the points a1 and a2 at both ends. When the smaller value of the maximum distance between two straight lines and the length L is w2, the larger value of w1 and w2 is the width W.
Center of gravity G: The center of gravity of the strands existing in all the shortest paths between the points a1 and a2 at both ends in the definition of the length L is defined as the center of gravity G.   When the length of the line segment of the specific partner is M, the difference MH between the length M of the line segment of the specific partner and the length H of the antenna of the RFID tag The booster antenna for an RFID tag according to claim 1, wherein the booster antenna is in a range of -0.4λ to 0.7λ with respect to the wavelength λ.   When the length H of the antenna of the RFID tag is less than 0.2λ with respect to the wavelength λ of the radio wave, the length L is 0.2λ to 0.4λ with respect to the wavelength λ of the radio wave. The RFID tag booster antenna according to claim 2, wherein the length difference MH falls within a range of -0.2λ to 0.2λ.   The distance Z from the center C of the antenna of the RFID tag to the plane on which the antenna element is disposed is set to 0.3λ or less with respect to the wavelength λ of the radio wave. The booster antenna for RFID tags as described.   The distance R from the center C of the antenna of the RFID tag to the midpoint of the line segment of the specific partner is set to 0.3λ or less with respect to the wavelength λ of the radio wave. The booster antenna for RFID tags described in 1.   When the antenna of the RFID tag has only one set of two points that determine the length H and has a longitudinal direction, the direction of the line segment of the specific partner and the plane on which the antenna element is arranged The booster antenna for an RFID tag according to any one of claims 1 to 5, wherein an absolute value of an angle α formed with a direction of the antenna of the RFID tag projected onto the antenna is 70 ° or less.   When the antenna of the RFID tag has only one set of two points that determine the length H and has a longitudinal direction, the length of the antenna of the RFID tag projected on the plane on which the antenna element is arranged The inclination angle β of the direction of the line segment extending so as to connect the tip end point of the base line from the base end point to the direction of the direction in the rotation direction of the radio wave is set to be 10 ° or more and 130 ° or less. The booster antenna for RFID tags according to any one of 1 to 6.   The center of gravity G of each of the two antenna elements is positioned on the opposite side of the line segment between the specific opponents in a plane where each antenna element is arranged with respect to a straight line obtained by extending the line segment between the two antenna elements. Alternatively, the booster antenna for an RFID tag according to any one of claims 1 to 7, wherein the booster antenna is located on the line segment between itself.   The RFID tag is attached to an article stored in a case that transmits radio waves or the case, and the two antenna elements are attached to the case and disposed. Booster antenna for RFID tags.   A plurality of the RFID tags are attached to the article or case, and the center C of the antenna of at least one RFID tag is set to the wavelength λ of the radio wave from the midpoint of the line between specific counterparts of the two antenna elements. 10. The apparatus according to claim 9, further comprising means for inhibiting communication of radio waves from the antenna of the reader with respect to an antenna of another RFID tag that is located at a distance of 0.3λ or less with respect to the other RFID tag. Booster antenna for RFID tag.   The booster antenna for an RFID tag according to claim 9 or 10, wherein the case that transmits the radio wave is a cardboard box.   The booster antenna for an RFID tag according to claim 11, wherein the antenna element is mounted on a side of the flap surface, joint portion, or joint extension portion of the corrugated cardboard box forming the corrugated cardboard box that overlaps the corrugated cardboard sheet.   The booster antenna for an RFID tag according to claim 9, wherein the antenna element is attached to a secondary material of the case.   The booster antenna for an RFID tag according to any one of claims 1 to 13, wherein the antenna element is formed by applying a conductive ink or a conductive paste.

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