JP2008182438A - Radio tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio tag capable of preventing the deterioration in communication distance even when the radio tag using a dipole antenna is made to adhere onto objects with material quality variously different in permittivity, such as glass, plastic, or ceramics. <P>SOLUTION: The radio tag 6A includes: the dipole antenna part 3A having a center part and two wing parts, respectively extending from both the ends of the center part; and a conductive pattern part 2 for connecting the two wing parts. The wing parts are constituted, thereby increasing an antenna width toward the end parts from a part close to the connection part to the conductive pattern part 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless tag that has at least one IC chip and an antenna therein and can wirelessly communicate data.

  A wireless tag including an IC chip that stores information and an antenna can transmit and receive data to and from a wireless device called an interrogator or a reader via radio waves. In particular, wireless tags that use 300 MHz or higher as the frequency of radio waves and do not have an internal power source have a long communicable distance with the reader / writer and are relatively inexpensive. Use is being considered.

  In a general wireless tag, an antenna is formed of aluminum or silver paste on a thin base material such as polyethylene terephthalate (hereinafter also referred to as PET) or paper, and an IC chip is connected to a feeding pad of the antenna. As the shape of the antenna, a dipole antenna, a folded dipole antenna, a loop type or a meander antenna is used.

  FIG. 6 is a diagram for explaining a conventional wireless tag. The wireless tag 62 has a structure in which the IC chip 12 and the antenna 52 are mounted on the substrate 42. Here, the antenna 52 is a ½ wavelength dipole antenna.

  When the length of the antenna 52 is L, the frequency at which the length L is ½ wavelength is the resonance frequency of this antenna.

  When such a wireless tag is used in a radio wave system of 900 MHz band, 2.45 GHz band, etc., the material of the member used by attaching the wireless tag such as glass, plastic, ceramic, or the contents of the container made of the member Depending on the object, the resonance frequency of the antenna decreases and the impedance changes greatly due to the influence of the dielectric constant of the member and contents. In such a case, the impedance on the IC chip side and the antenna side are mismatched and the communication distance is shortened.

  It is also possible to adjust the impedance of the wireless tag itself according to the dielectric constant of the member and contents to paste the wireless tag, but in that case, because the member and material to paste the wireless tag are limited in advance, It becomes impossible to use the wireless tag alone or in other environments, and it lacks versatility.

  The above-mentioned problem is not solved directly, and there is an H-type antenna as a technique for avoiding the deterioration of the communication distance due to the miniaturization of the antenna, which is disclosed in Patent Document 1, for example.

  The H-type antenna is designed so that the antenna length is equal to or less than ¼ wavelength, for example, and the antenna width and the antenna length are designed to be almost equal, and the energy is efficiently concentrated around the IC chip to maintain a constant communication distance. It is intended to be attached to a small article that cannot use a half-wave dipole antenna having stable communication performance.

JP 2006-25390 A

  The technical problem of the present invention is that even if a wireless tag using a half-wave dipole antenna is attached to an article made of various materials having different dielectric constants such as glass, plastic, ceramic, etc. It is to provide a wireless tag that does not deteriorate.

  The present invention is a wireless tag configured by mounting an antenna and an IC chip on a substrate, and the antenna extends, for example, from a substantially rectangular or strip-shaped central portion and different directions from both ends of the central portion. The wireless tag is configured to include a dipole antenna portion having two wing portions as constituent elements and a conductive pattern portion (short stub portion) for coupling the two wing portions. The conductive pattern portion is substantially band-shaped and is arranged substantially in parallel with the central portion, and the two wing portions of the dipole antenna portion are connected to the conductive pattern portion from the vicinity of the end portion of the wing portion. It is configured to have a portion where the antenna width increases toward.

  Note that it is preferable in terms of communication characteristics and manufacturing that the increased portion of the antenna width is configured to increase at a constant rate.

  Furthermore, it is preferable in terms of communication characteristics and manufacturing that the two wing parts are configured to be a line object with respect to a line passing through the IC chip and perpendicular to the length direction of the dipole antenna part.

  The conductive pattern portion is provided for impedance adjustment. By forming the conductive pattern portion so as to connect the two wing portions, the impedance can be effectively adjusted and the manufacture is facilitated. In addition, it is preferable in terms of design and manufacturing to provide it in parallel with the central portion.

  By configuring the wing part shape of the dipole antenna part in this way, a plurality of antenna lengths can be set, so that the resonance frequency of the RFID tag antenna is in a range with a width centered on a half wavelength. Can be set. Therefore, whether the wireless tag is used alone or affixed to an article having a different dielectric constant, the impedance is matched and the communication state can be kept good as long as it is within a certain condition.

  According to the present invention, there is provided a wireless tag configured by mounting an antenna and an IC chip on a substrate, wherein the antenna extends from each of a central portion to which the IC chip is connected and both ends of the central portion. A wireless tag is obtained, comprising: a dipole antenna portion composed of two wing portions; and a conductive pattern portion that couples the two wing portions, wherein the antenna has a resonance frequency of at least ½ wavelength. It is done.

  According to the present invention, it is possible to obtain a wireless tag characterized in that the antenna width of the two wing parts increases toward the end of the wing part.

  According to the present invention, it is possible to obtain the wireless tag characterized in that the two wing portions have a portion where the antenna width increases at a constant rate toward the end portion of the wing portion.

  According to the present invention, it is possible to obtain a wireless tag characterized in that the two wing portions have a flat portion having a constant antenna width.

  According to the present invention, there is provided a wireless tag characterized in that the spread angle of the two wing portions is set in a range of 45 ° or more and 55 ° or less with respect to the length direction of the dipole antenna portion. It is done.

  According to the present invention, it is possible to obtain a wireless tag characterized in that the conductive pattern portion is in a band shape and is arranged in parallel with the central portion.

  According to the present invention, even when a wireless tag is attached to an article having a different dielectric constant such as glass, plastic, or ceramic, or even when a liquid or an article having a different dielectric constant is present near the wireless tag, the communication distance is deteriorated. Communication characteristics can be kept good.

  The wireless tag of the present invention includes a substrate made of a general dielectric such as glass epoxy, polyethylene terephthalate, polyimide, and the like, an antenna formed by an antenna pattern made of a metal such as copper, silver, and gold, and an IC chip. The power supply terminal and the ground terminal of the IC chip are each connected to the antenna.

  The antenna has a conductive pattern (short stub) part for impedance adjustment connected to a dipole antenna part, and the dipole antenna part has a central part on which an IC chip is mounted, and both ends of the central part, Each wing shape is formed by increasing the antenna width toward the open end direction of the antenna, that is, two wing portions. The rate of increase of the antenna width can be arbitrarily set, but a trapezoidal shape in which the antenna width increases at a constant rate is preferable in design and manufacture.

  In addition, when the wing portion of the dipole antenna portion is formed in a trapezoidal shape, it is resonant that the spread angle of the trapezoid is set in a range of 45 ° to 55 ° with respect to the length direction of the dipole antenna portion. This is preferable for widening the frequency range. That is, if the spread angle is less than 45 °, the resonance frequency range for the electromagnetic wave of the antenna is limited, and if the angle exceeds 55 °, the entire wireless tag becomes undesirably large.

  Further, it is preferable that the wing portion is configured to be thicker than the width of the central portion in order to maintain basic communication performance. Therefore, it is preferable to provide a step between the central portion and the wing portion.

  For miniaturization, it is preferable to provide a flat portion with a constant antenna width on the wing portion.

  In order to facilitate impedance adjustment, it is preferable to form a conduction pattern portion in parallel between the two wing portions.

  Hereinafter, embodiments of the present invention will be described in detail using examples. FIG. 1 is a diagram illustrating a wireless tag according to the present invention. In the wireless tag 6A, an antenna 5A made of an aluminum pattern is formed on a substrate 4A made of PET, and the antenna 5A is connected to a power supply terminal (not shown) and a ground terminal (not shown) of the IC chip 1, respectively. Has been. Here, the antenna 5A includes a half-wave dipole antenna portion 3A and a conductive pattern portion 2.

  Further, the dipole antenna portion 3A has a central portion connected to the IC chip 1 and two wing portions extending from both ends of the central portion, and the length X1 of the wing portion is 50 mm. Further, the conductive pattern portion 2 is formed in parallel with the central portion at a position about 4 mm away from the central portion.

  The wing portion of the dipole antenna portion 3A is formed to have a 45 ° spread angle with respect to the length direction of the antenna from the boundary portion between the conductive pattern portion 2 and the dipole antenna portion 3A. Further, the portion where the conductive pattern portion 2 is not formed also has a 45 ° spread angle as shown in the figure, and the wing portion is formed so as to be a target with respect to the length direction of the antenna. By adopting such a shape, the effective dimension of the antenna 5A with respect to the radio wave is a minimum length X1 from the open end to the open end of the wing, and a maximum from the apex of one wing to the center, and the other. It becomes the distance Y1 to the apex of the wing, and can resonate with respect to a radio wave having a ½ wavelength in the range from the length X1 to the distance Y1.

  FIG. 3 is a graph showing a VSWR measurement result of the wireless tag of the present invention. VSWR is an acronym for Voltage Standing Wave Ratio, which is the voltage standing wave ratio, that is, the peak and valley of the voltage amplitude distribution generated on the transmission line where the reflected wave is generated due to impedance mismatch. The ratio is shown.

  FIG. 3 shows a result of measuring VSWR using a frequency of 2 to 3 GHz. Data A is obtained when the wireless tag shown in FIG. 1 is attached to a foamed polystyrene plate having a dielectric constant of 1 and a thickness of 3 mm. When the wireless tag is attached to a plastic plate having a dielectric constant of 2.5 and a thickness of 3 mm, data C shows the measurement result when the wireless tag is attached to a ceramic plate having a dielectric constant of 6.5 and a thickness of 3 mm. It is shown.

  In both data A, data B, and data C, the VSWR at 2.4 to 2.5 GHz is 2.5 or less, and the IC chip 1 and the antenna 5A are attached to the article having different dielectric constants. It can be seen that the impedances are matched.

  FIG. 5 is a diagram illustrating a wireless tag of a comparative example. The wireless tag 61 is configured by mounting an IC chip 11, an antenna 51 including a dipole antenna portion 31 and a conductive pattern portion 21 on a substrate 41. The length of the antenna 51 is 50 mm.

  4 is a graph showing the VSWR measurement result of the wireless tag of the comparative example, and shows the result of measuring the VSWR under the same conditions as in FIG. 3 using the wireless tag shown in FIG. That is, when data D is pasted on a foamed polystyrene, data E is pasted on a plastic plate, and data F shows a VSWR measurement result when pasted on a ceramic plate.

  In data D, the VSWR of 2.4 to 2.5 GHz is 2.5 or less, but in data E and data F, VSWR is 6 to 7 and 7 to 9, and the impedance between the IC chip 11 and the antenna 51 is Not consistent.

  Further, when the communication distance was compared, the wireless tag of the comparative example shown in FIG. 5 was unable to communicate when pasted on a ceramic plate having a dielectric constant of 7 and a thickness of 3 mm, whereas the wireless tag of the present invention had a dielectric constant of 7. Even when pasted on a ceramic plate having a thickness of 3 mm, the communication distance hardly deteriorated compared to the case of pasting on a foamed polystyrene plate having a dielectric constant of 1 and thickness of 3 mm.

  FIG. 2 is a diagram illustrating a wireless tag according to the present invention. In the wireless tag 6B, an antenna 5B made of a silver pattern is formed on a substrate 4B made of PET, and the antenna 5B is connected to a power supply terminal (not shown) and a ground terminal (not shown) of the IC chip 1, respectively. Has been. Here, the antenna 5 </ b> B includes a ½ wavelength dipole antenna portion 3 </ b> B and the conduction pattern portion 2.

  Furthermore, the dipole antenna portion 3B has a central portion connected to the IC chip 1 and two wing portions extending from both ends of the central portion, and the length X2 of the wing portion is 55 mm. Further, the conductive pattern portion 2 is formed in parallel with the central portion at a position about 3 mm away from the central portion.

  The wing portion of the dipole antenna portion 3B is formed to have a spread angle of 55 ° with respect to the length direction of the antenna from the boundary portion between the conduction pattern portion 2 and the dipole antenna portion 3B. A portion having a length of 15 mm or more formed a flat portion in which the width of the wing portion was constant. Further, the portion where the conductive pattern portion 2 is not formed also has a 55 ° spread angle as shown in the figure, and the wing portion is formed so as to be a target with respect to the length direction of the antenna. That is, the wing portion has a shape in which a trapezoid with a spread angle of 55 ° and a rectangle are continuously formed.

  By adopting such a shape, the width of the entire wireless tag can be designed to be narrow. In addition, the effective dimension of the antenna 5A for radio waves is a minimum length X2 from the open end of the wing to the other open end, and a maximum from the top of one wing to the center and the top of the other wing. It becomes possible to resonate with respect to a radio wave having a half wavelength in the range of length X2 or more and distance Y2 or less.

  Note that the wireless tag having the configuration of FIG. 5 with the antenna length of 55 mm cannot be communicated when pasted on a ceramic having a dielectric constant of 20 and a thickness of 7 mm, whereas the wireless tag of the present invention has a dielectric constant of 20 Even when pasted on a ceramic plate having a thickness of 7 mm, the communication distance hardly deteriorated as compared with the case of pasting on a foamed polystyrene plate having a dielectric constant of 1 and thickness of 7 mm.

  The embodiments of the present invention have been described above using the embodiments. However, the present invention is not limited to these embodiments, and the present invention is not limited to the scope of the present invention. Included in the invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

  By using the wireless tag of the present invention, in the management of various articles represented by distribution management, sales management, inventory management, usage status management of goods, etc., a system suitable for the material and usage environment of the articles to be managed, etc. It can be constructed easily.

6A and 6B illustrate a wireless tag according to the present invention. 6A and 6B illustrate a wireless tag according to the present invention. The graph which shows the VSWR measurement result of the radio | wireless tag of this invention. The graph which shows the VSWR measurement result of the wireless tag of a comparative example. 6A and 6B illustrate a wireless tag of a comparative example. FIG. 10 illustrates a conventional wireless tag.

Explanation of symbols

1,11,12 IC chip 2,21 conductive pattern part
3A, 3B, 31 Dipole antennas 4A, 4B, 41, 42 Substrates 5A, 5B, 51, 52 Antennas 6A, 6B, 61, 62 Radio tag A data (when the radio tag of the present invention is attached to a foamed polystyrene)
B data (when the wireless tag of the present invention is attached to a plastic plate)
C data (when the wireless tag of the present invention is attached to a ceramic plate)
D data (when a conventional wireless tag is attached to a foamed polystyrene)
E data (when a conventional wireless tag is attached to a plastic plate)
F data (when a conventional wireless tag is attached to a ceramic board)
X1, X2, L Length Y1, Y2 Distance

Claims (6)

  A wireless tag comprising an antenna and an IC chip mounted on a substrate, wherein the antenna is composed of a central part to which an IC chip is connected and two wing parts extending from both ends of the central part. A wireless tag comprising: a dipole antenna portion to be connected; and a conductive pattern portion for coupling the two wing portions, wherein the antenna has a resonance frequency of at least ½ wavelength.   The wireless tag according to claim 1, wherein an antenna width of the two wing parts increases toward an end of the wing part.   The wireless tag according to claim 1, wherein the two wing parts have a portion in which an antenna width increases at a constant rate toward an end of the wing part.   The wireless tag according to claim 3, wherein the two wing parts have a flat part having a constant antenna width.   5. The spread angle of the two wing parts is set in a range of 45 ° or more and 55 ° or less with respect to the length direction of the dipole antenna part. Wireless tag.   The wireless tag according to claim 1, wherein the conductive pattern portion is arranged in parallel with the central portion.

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