JP2012118911A - Radio ic tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio IC tag which is durable and has high reliability.SOLUTION: There is provided the radio IC tag comprising a metal cylinder 1 having both ends made open, a radio IC chip 10, and a printed wiring board 2 where wiring of a matching loop circuit 5 having a terminal part electrically connected to the radio IC chip 10 is formed, the radio IC tag being characterized in that the printed wiring board 2 is installed in the metal cylinder 1, a part of the wiring of the matching loop circuit 5 is put close to an inner surface of the metal cylinder 1 to achieve electromagnetic coupling, and antenna impedance including the metal cylinder 1 is matched with the radio IC chip 10 by the matching loop circuit 5.

Description

  The present invention relates to a wireless IC tag, and is a wireless IC tag for long-distance communication in which a metal pattern layer electrically connected to a wireless IC chip is installed in a metal cylinder. For example, the frequency of the UHF band (953 MHz band (plus / minus) 2 MHz) is set as the operating frequency.

  As a robust wireless IC tag, a wireless IC chip part and an antenna molded with resin have been proposed as in Patent Document 1. This technology can reduce the impact on the wireless IC chip by completely covering the wireless IC chip with resin. Further, as in Patent Document 2, the circuit chip part in which the wireless IC chip and the loop circuit are packaged is separated from the antenna part in a direct current manner, and the circuit chip part and the antenna part are exchanged by electromagnetic coupling. What was combined was proposed. In this technique, since the circuit chip portion and the antenna portion are not electrically connected in a direct current manner, there is no problem that the connection between the circuit chip portion and the antenna portion is disconnected due to stress.

JP 2007-42087 A JP 2009-75687 A

  However, the technique of Patent Document 1 has a problem that the structure is complicated and the manufacturing cost is increased because the multilayer structure is formed by the resin mold, and the wireless IC chip is caused by the load applied to the wireless IC chip when resin molding is performed. There was a problem that was easily damaged. In addition, since the characteristics change due to variations in the dielectric constant of the resin to be molded, there is also a problem that the dielectric constant of the resin to be molded must be strictly controlled. Furthermore, there has been a problem that the radiation gain is lowered by the dielectric loss (tan δ) of the resin to be molded.

  Further, in the technique of Patent Document 2, the packaged wireless IC chip portion is hardened, but since the antenna portion is not hardened, the antenna portion may be damaged when a load is applied to the antenna portion from above. .

  An object of the present invention is to provide a wireless IC tag that solves the conventional problems and is robust and highly reliable.

  In order to solve the above-mentioned problem, the present invention provides a printed circuit board in which a matching tube circuit wiring having a metal tube having both ends opened, a wireless IC chip, and a terminal portion electrically connected to the wireless IC chip is formed. A wireless IC tag comprising a wiring board, wherein the printed wiring board is installed inside the metal cylinder, and a part of the wiring of the matching loop circuit is brought close to the inner surface of the metal cylinder to be electromagnetically coupled; The wireless IC tag is characterized in that an antenna impedance including the metal cylinder is matched to the wireless IC chip by a circuit.

  In addition, the present invention is the wireless IC tag according to the above-described wireless IC tag, wherein an IC tag antenna portion electromagnetically coupled to the matching loop circuit is formed on the printed wiring board.

  According to the present invention, printing is performed in which the wiring of the matching loop circuit 5 having the metal cylinder 1 having both ends open, the wireless IC chip 10, and the terminal portions 10 a and 10 b electrically connected to the wireless IC chip 10 is formed. A wireless IC tag composed of a wiring board 2 is installed in a printed wiring board 2 inside a metal cylinder 1 and a part of the wiring of the matching loop circuit 5 is brought close to the inner surface of the metal cylinder 1 to be electromagnetically coupled. The circuit 5 provides a wireless IC tag in which the impedance between the wireless IC chip 10 and the antenna system including the metal cylinder 1 is matched, and the printed wiring board 2 is protected by the metal cylinder 1 operating as an antenna. Thus, there is an effect that a highly reliable wireless IC tag can be obtained.

1 is a perspective view of an RFID according to a first embodiment of the present invention. It is sectional drawing which shows the structure of a cross section perpendicular | vertical to the cylinder axis | shaft of the metal cylinder of RFID which concerns on the 1st Embodiment of this invention. It is an enlarged view of the A section of FIG. 1 of the 1st Embodiment of this invention. It is an enlarged view of the part of the printed wiring board of the modification 1 of the 1st Embodiment of this invention. It is a perspective view of RFID which concerns on the 2nd Embodiment of this invention. It is an enlarged view of the A section of Drawing 5 explaining arrangement and an electromagnetic field of a metal surface of a metal cylinder and a matching loop circuit of a 2nd embodiment of the present invention.

<First Embodiment>
A first embodiment of the present invention will be described with reference to FIGS. 1 shows a perspective view of the present embodiment, FIG. 2 shows a cross-sectional view perpendicular to the central axis of the metal cylinder 1 of FIG. 1, and FIG. 3 is an enlarged view of a portion A of FIG.

(Configuration of wireless IC tag)
The wireless IC tag of the first embodiment uses a dipole wireless IC tag. As shown in FIG. 1, the wireless IC tag of the present embodiment uses a metal cylinder 1 having both ends open and a space inside. The metal cylinder 1 having both ends opened is a cylinder or square section cylinder having a length of a half wavelength (λ / 2) of an electromagnetic field having a frequency used by the wireless IC tag and an inner diameter of about 10 mm. The external space is connected to the internal space of the metal tube 1 at both open ends of the metal tube 1, and the internal space is filled with outside air. As shown in FIG. 2, an inlet (printed wiring board) 2 of an organic resin substrate such as an epoxy resin having a thickness of 1 mm to 1.6 mm is installed in the space inside the metal cylinder 1.

  The printed wiring board 2 has a dipole antenna type radio frequency IC tag antenna section 4 disposed on the surface or in the inner layer at the position of the central axis of the metal cylinder 1 by a metal pattern layer 3 such as copper as shown in FIG. Then, a loop-shaped matching loop circuit 5 inserted in series at the intermediate portion is formed. The wireless IC chip 10 is installed by electrically connecting the terminal portions of the wireless IC chip 10 to both ends of the wiring of the loop-shaped matching loop circuit 5. The metal pattern layer 3 other than the portion electrically connected to the terminal portions 10a and 10b of the wireless IC chip 10 is covered with a solder resist pattern to protect the metal pattern layer 3. Although the cylindrical metal cylinder 1 is shown in FIG. 1, the shape of the metal cylinder 1 is not limited to a cylinder, and a metal cylinder 1 having a square or arbitrary polygonal cross section can be used.

  FIG. 2 is a cross-sectional view perpendicular to the cylinder axis of the metal cylinder 1. An inlet (printed wiring board) 2 is inserted from the opening end of the metal tube 1 and the printed wiring board 2 is inserted into and held by a cut-in portion 1 a provided inside the metal tube 1 or the printed wiring board 2 is cut. Fit into 1a and bond and fix. A metal pattern layer 3 is formed on the surface of the inlet (printed wiring board) 2. The method of attaching the printed wiring board 2 to the metal cylinder 1 is not limited to the method of inserting the printed wiring board 2 from the opening end of the metal cylinder 1 and is formed by dividing the metal cylinder 1 into two parts vertically. The printed wiring board 2 may be sandwiched and fixed between the two portions of the metal cylinder 1. By housing the printed wiring board 2 with the wireless IC chip 10 mounted in the metal cylinder 1 in this way, a robust and highly reliable wireless IC tag in which the printed wiring board 2 is protected by the metal cylinder 1 can be obtained. effective.

  The metal cylinder 1 is formed of a metal such as copper, a copper alloy, aluminum, nickel, or an iron alloy having a thickness of 0.2 mm to 1 mm in a cylindrical shape such as a cylindrical shape or a square cross section. Since the current flowing through the metal tube 1 is biased to a thin surface layer due to the skin effect, the metal tube 1 has a thickness equal to or greater than the thickness of the skin effect (in the case of copper, about 2 μm at a frequency of 1 GHz). Thick enough to flow. The length of the metal cylinder 1 is set to the length of the half wavelength (λ / 2) of the electromagnetic field of the frequency used by the wireless IC tag ((λ / 2) = 157 mm when the frequency of the electromagnetic field used is 955 MHz). . When an aluminum tube is used as the metal cylinder 1, the weight can be reduced. When strong iron, steel, or the like is used as the metal cylinder 1, there is an effect that the strength of the metal cylinder 1 can be increased. The wiring of the loop-shaped matching loop circuit 5 of the metal pattern layer 3 formed on the surface of the printed wiring board 2 is brought closer to the inner surface of the metal tube 1, but the closer the metal tube 1 and the matching loop circuit 5 are, the stronger the both are. Electromagnetic coupling. The matching loop circuit 5, the IC tag antenna unit 4, and the metal cylinder 1 constitute an antenna system.

  The metal pattern layer 3 that forms the IC tag antenna portion 4 and the matching loop circuit 5 on the surface of the printed wiring board 2 is either rolled foil having a thickness of 20 μm or less, vapor deposition, or printing of conductive paint, or a combination thereof. Formed by. A matching loop circuit 5 is integrally connected to the IC tag antenna unit 4 at the center position of the dipole IC tag antenna unit 4. The matching loop circuit 5 is formed by a loop-shaped wiring, and the terminal portions 10 a and 10 b of the wireless IC chip 10 are electrically connected to both ends of the wiring of the loop-shaped matching loop circuit 5. By adjusting the dimensions of the loop matching loop circuit 5, the impedance Zi of the wireless IC chip 10 and the antenna impedance Za are matched.

  FIG. 3 shows an enlarged view of part A of FIG. The terminal portions 10a and 10b of the wireless IC chip 10 are electrically connected to both ends of the loop matching loop circuit 5 by ACP (Anisotropic Conductive Paste) or soldering. Then, as shown in FIG. 3, the matching loop circuit 5 is made by bringing the looped wiring of the matching loop circuit 5 connected to the IC tag antenna unit 4 near the central axis of the metal cylinder 1 close to the inner surface of the metal cylinder 1. Electromagnetically coupled with the metal cylinder 1.

(Modification 1)
As a configuration of the modified example 1, as shown in FIG. 4, the matching loop circuit 5 and the IC tag antenna unit 4 are separated from each other in a direct current manner. That is, in the above embodiment, the matching loop circuit 5 is directly electrically connected and coupled to the central portion of the IC tag antenna unit 4. In the first modification, the matching loop circuit 5 is not directly connected. By bringing 5 close to the IC tag antenna unit 4, both are electromagnetically coupled. Also in the structure of the first modification, the matching loop circuit 5 can be connected to the IC tag antenna unit 4 by electromagnetic coupling with the IC tag antenna unit 4 by being arranged close to the IC tag antenna unit 4.

(Operation of the wireless IC tag of the first embodiment)
The operating frequency f of the wireless IC tag using the UHF band frequency is 953 MHz (plus / minus) 2 MHz, which is a high frequency. For this reason, even if the metal surface of the metal tube 1 is not connected to the metal pattern layer 3 in a direct current manner as shown in FIG. The narrower the gap between the metal surface of the metal tube 1 and the metal pattern layer 3, the stronger the bond. When the metal surface of the metal tube 1 is coupled to the metal pattern layer 3 in an alternating manner, the resonance frequency is lowered by the following mechanism.

First, the resonance frequency of the IC tag antenna unit 4 alone is the resonance frequency of the LC resonance circuit of the self-inductance and the stray capacitance of the IC tag antenna unit 4. Here, the metal cylinder 1 is I
When approaching the C tag antenna unit 4, the effective inductance involved in the resonance of the IC tag antenna unit 4 is an inductance obtained by adding the mutual inductance M between the IC tag antenna unit 4 and the metal cylinder 1 to the self-inductance. The effective inductance of the tag antenna unit 4 is increased. Thereby, the resonance frequency of the IC tag antenna unit 4 is lowered. Similarly, when the IC tag antenna unit 4 approaches the metal cylinder 1 with respect to the resonance frequency of the metal cylinder 1, the effective inductance involved in the resonance of the metal cylinder 1 is similar to the self-inductance of the metal cylinder 1. The mutual inductance M with the antenna unit 4 is added, and the effective inductance of the metal tube 1 is increased. Thereby, the resonance frequency of the metal cylinder 1 is lowered. Thus, the resonance frequency of the overall antenna system is lowered.

Specifically, first, a standing wave current flows on the surface of the metal cylinder 1 manufactured according to the half wavelength (λ / 2) of the electromagnetic field to be used. As shown in FIG. 3, the wiring of the loop-shaped matching loop circuit 5 is arranged close to the inner surface of the metal cylinder 1, and the wiring of the dipole IC tag antenna unit 4 is arranged on the central axis of the metal cylinder 1. . The standing wave causes the current I ₁ to flow through the inner surface as well as the outer surface of the metal tube 1. The magnetic field H generated by the current I ₁ flowing on the inner surface of the metal cylinder 1 is combined with the loop-like wiring of the matching loop circuit 5 near the inner surface of the metal cylinder 1, and the induced current I ₂ is supplied to the matching loop circuit 5. Shed. Thus, the current I ₁ flowing through the inner surface of the metal cylinder 1 and the current I ₂ flowing through the matching loop circuit 5 are electromagnetically coupled by the standing wave.

Further, as shown in FIG. 3, the current I ₃ flowing through the dipole antenna type IC tag antenna portion 4 disposed at the position of the central axis of the metal cylinder 1 is the current I ₁ generated on the inner surface of the metal cylinder 1 by the standing wave. Flows in the opposite direction. Since the current I ₁ flowing in the current I ₃ and the metal cylinder 1 flows into the IC tag antenna unit 4 is canceled, IC tag antenna unit 4 itself does not emit radio waves. Further, the magnetic field generated by the current I ₁ of the metal tube 1 is electromagnetically coupled with the matching loop circuit 5 of the looped current I ₂ flows in the matching loop circuit 5, the current I and the current I ₂ is the IC tag antenna 4 ₃ is generated. The resonance frequency of the antenna system composed of the matching loop circuit 5 and the IC tag antenna unit 4 shifts to a lower frequency as the distance between the loop-shaped wiring of the matching loop circuit 5 and the inner surface of the metal tube 1 approaches. For this reason, it is necessary to adjust the resonance frequency, but it can be easily adjusted by adjusting the antenna length of the IC tag antenna unit 4.

Here, the impedance of the wireless IC chip 10 is defined as Zi, and the antenna impedance formed by the matching loop circuit 5, the IC tag antenna unit 4, and the metal cylinder 1 is defined as Za. That is, when the input impedance of the antenna system observed as the impedance between both ends of the wiring of the matching loop circuit 5 from the terminal portions 10a and 10b side of the wireless IC chip 10 is defined as Za, the impedance Zi of the wireless IC chip 10 is defined. The antenna impedance Za can be expressed by the following equation.
(Formula 1) Zi = Zi (re) + j × Zi (im)
(Formula 2) Za = Za (re) + j × Za (im)
By designing so that the following conditions are satisfied or close to the following conditions, the wireless IC chip 10 and the antenna impedance can be matched, and a signal can be transmitted between the wireless IC chip 10 and the antenna.
(Formula 3) Zi (re) = Za (re)
(Formula 4) Zi (im) = − Za (im)

The antenna system including the metal cylinder 1, the IC tag antenna unit 4, and the matching loop circuit 5 can adjust the imaginary component of the antenna impedance Za by adjusting the antenna length of the IC tag antenna unit 4. Here, the antenna impedance Za is an antenna impedance observed from the terminal portions 10a and 10b of the wireless IC chip 10 to which the matching loop circuit 5 is connected. When the antenna length of the IC tag antenna unit 4 is shortened, the inductance of the IC tag antenna unit 4 is reduced, and the imaginary component of the antenna impedance Za is reduced. Thus, the imaginary number component of the antenna impedance Za can be adjusted to match the imaginary number component of the impedance Zi of the wireless IC chip 10 so as to satisfy Equation 4. This adjustment changes the real number component of the antenna system, which causes a slight matching loss, but the loss is sufficiently smaller than the dielectric loss when the IC tag antenna portion 4 is embedded in the resin in the prior art.

  Further, by adjusting the distance between the metal surface of the metal tube 1 of the matching loop circuit 5 and the coupling coefficient of the electromagnetic coupling between the metal tube 1 and the matching loop circuit 5, the amount of electromagnetic field radiation from the metal tube 1 is adjusted. Can be adjusted. Thereby, the real component of the antenna impedance Za observed from the terminal portions 10a and 10b of the wireless IC chip 10 is adjusted. Here, the IC tag antenna unit 4 of the metal pattern layer 3 is inductively coupled with the metal tube 1 in an alternating manner, and mutual inductance is generated between the IC tag antenna unit 4 and the metal tube 1. The current flowing through 4 is canceled by the current flowing through the metal surface inside the metal cylinder 1. For this reason, an electromagnetic field is not directly radiated from the IC tag antenna unit 4, and the electromagnetic field is radiated by a current flowing on the metal surface outside the metal tube 1. In this way, the real component of the antenna impedance Za can be adjusted to match the real component of the impedance Zi of the wireless IC chip 10 so as to satisfy Equation 3. At that time, even if the coupling coefficient of electromagnetic coupling is changed, the imaginary component of the antenna impedance Za does not change so much, so the imaginary component and the real component of the antenna impedance Za can be adjusted independently, and the impedance can be easily adjusted. There is an effect.

  The complex impedance Zi of a certain wireless IC chip 10 used at 950 MHz was 20Ω−j × 183Ω (j is an imaginary unit). In this case, if the antenna impedance Za observed from the terminal portions 10a and 10b of the wireless IC chip 10 is set to 20Ω + j × 183Ω, the equations 3 and 4 are satisfied, and the impedances are matched. When the imaginary part of the impedance is 183Ω at 950 MHz, the imaginary component of this impedance of the antenna system mainly consists of the self-inductance of the matching loop circuit 5, and the value of the self-inductance is 31 nH.

  By adjusting the magnitude of the appropriate electrical coupling that matches the impedance by bringing the real component of the antenna impedance Za close to the real component of the impedance Zi of the wireless IC chip 10, the terminal portions 10a and 10b of the wireless IC chip 10 are adjusted. The real part of the antenna impedance Za observed from is adjusted to 20Ω, which is the value of the real part of the complex impedance of the wireless IC chip 10. The real part of the impedance can be operated as the antenna even if it is several times or a fraction of the ideal value. Therefore, the inside of the matching loop circuit 5 and the metal cylinder 1 can be operated. There is no practical problem even if the distance between the metal surface is not strictly adjusted for each metal cylinder 1.

  In this way, by adjusting the antenna length of the IC tag antenna portion 4 and adjusting the distance between the matching loop circuit 5 and the inner surface of the metal tube 1, the antenna is observed from the terminal portions 10a and 10b of the wireless IC chip 10. It is possible to match the antenna impedance Za to the impedance Zi of the wireless IC chip 10 to efficiently supply power from the wireless IC chip 10 to the metal cylinder 1 and to radiate electromagnetic waves from the metal cylinder 1. The communication distance of the wireless IC tag of this embodiment is proportional to the length of the metal cylinder 1, and when the length of the metal cylinder 1 is about 157 mm at half wavelength (λ / 2), the maximum communication distance is up to about 3 m. It is possible to communicate with the reader / writer of the wireless IC tag.

Since the wireless IC tag of the present embodiment is loaded with the wireless IC chip 10, the matching loop circuit 5 connected to the wireless IC chip 10, and the IC tag antenna unit 4, the wireless IC tag can be made robust. There is. In the wireless IC tag, the portion of the wireless IC chip 10 is easily affected by external force and is vulnerable to bending and impact. The wireless IC tag of this embodiment has an effect of eliminating the influence of external force by loading the wireless IC chip 10 into the metal tube 1. In addition, the wireless IC tag of this embodiment is configured such that the periphery of the printed wiring board 2 installed inside the metal cylinder 1 is composed of air, and the antenna wiring formed on the metal pattern layer 3 as in the conventional patent document 1 is provided. Is not covered with the mold resin, there is an effect that there is no influence of the dielectric loss of the mold resin in the case of Patent Document 1.

  As a use application of the wireless IC tag of the present embodiment, the wireless IC tag is incorporated into a metal building material, a transporting carriage (metal handle part) before assembly, and the wireless IC tag is communicated with a reader / writer. Therefore, it can be used for theft prevention and management of those products.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIGS. FIG. 5 shows a perspective view of the present embodiment, and FIG. 6 is an enlarged view of a portion A in FIG.

(Constitution)
The wireless IC tag according to the second embodiment uses a microstrip antenna type IC tag. As shown in FIG. 5, a microstrip antenna consisting only of a matching loop circuit 5 is formed by a metal pattern layer 3 on the surface of an organic resin or ceramic printed wiring board 2 in a metal tube 1 or on an inner layer. ing. The structure of the cross section perpendicular to the central axis of the metal cylinder 1 is formed in the same manner as in FIG. 2 of the first embodiment.

  FIG. 6 shows an enlarged view of part A of FIG. As shown in FIG. 6, the metal pattern layer 3 formed on the surface of the printed wiring board 2 is such that the wiring pattern of the loop-shaped matching loop circuit 5 is formed non-targeted with respect to the central axis of the metal tube 1. Yes. Specifically, a wiring pattern of a loop-shaped matching loop circuit 5 connected to the terminal portions 10 a and 10 b of the wireless IC chip 10 installed near the central axis of the metal cylinder 1 is formed on the metal pattern layer 3. . The wiring pattern of the matching loop circuit 5 is such that the narrow portion 5a connected to the terminal portions 10a and 10b of the wireless IC chip 10 near the central axis of the metal cylinder 1 and the middle of the wiring close to the inner wall of the metal cylinder 1 are used. It forms in the wide part 5b which is a part. In other words, the wiring pattern of the matching loop circuit 5 is asymmetrically arranged in the metal cylinder 1 with respect to the central axis.

  This loop-shaped matching loop circuit 5 can increase the inductance by narrowing the width of the narrow portion 5a or increasing the length thereof. The imaginary number component of the impedance due to the inductance is made substantially the same as the imaginary number component of the antenna impedance Za observed from the terminal portions 10a and 10b of the wireless IC chip 10 to which the matching loop circuit 5 is connected. Thus, the imaginary number component of the antenna impedance Za is adjusted by adjusting the length and line width of the narrow portion 5a of the wiring.

  Further, by adjusting the distance between the wide portion 5b of the matching loop circuit 5 and the inner surface of the metal tube 1, the degree of electrical coupling between the metal tube 1 and the matching loop circuit 5 can be adjusted, and thereby the metal The amount of electromagnetic field radiation from the cylinder 1 is determined, and the real component of the antenna impedance Za observed from the terminal portions 10a and 10b of the wireless IC chip 10 changes. Thereby, the real number component of the antenna impedance Za can be adjusted. By adjusting the distance between the wide portion 5b of the matching loop circuit 5 and the metal cylinder 1, the imaginary number component of the antenna impedance Za does not change so much, so that the imaginary number component and the real number component of the antenna impedance Za can be adjusted independently. There is an effect that adjustment of impedance is easy.

(Operation of the wireless IC tag of the second embodiment)
First, a standing wave current flows on the surface of the metal cylinder 1 manufactured in accordance with the half wavelength (λ / 2) of the electromagnetic field to be used. The standing wave causes the current I ₁ to flow through the inner surface as well as the outer surface of the metal tube 1. The magnetic field H generated by the current I ₁ flowing on the inner surface of the metal tube 1 is combined with the wide portion 5b, which is an intermediate portion of the loop-shaped wiring of the matching loop circuit 5 close to the inner surface of the metal tube 1, and the matching loop An induced current I _{2 is} passed through the circuit 5. Thus, the current I ₁ flowing through the inner surface of the metal cylinder 1 and the current I ₂ flowing through the matching loop circuit 5 are electromagnetically coupled by the standing wave. The narrow width portions 5 a at both ends of the wiring pattern of the matching loop circuit 5 are connected to the terminal portions 10 a and 10 b of the wireless IC chip 10.

  By adjusting these as follows, the imaginary number component and the real number component of the antenna impedance Za are adjusted to match the antenna impedance Za with the impedance Zi of the wireless IC chip 10. The imaginary component of the antenna impedance Za observed from the terminal portions 10 a and 10 b of the wireless IC chip 10 is mainly determined by the shape of the matching loop circuit 5. When the shape of the matching loop circuit 5 is reduced, the current path length is also shortened. Therefore, the inductance (L) of the matching loop circuit 5 and the imaginary component of the impedance (X = ωL) are reduced, and the terminal portion 10a of the wireless IC chip 10 The same applies to the imaginary component of the antenna impedance Za observed from 10b. Further, when the line width of the narrow portion 5a of the wiring of the matching loop circuit 5 is reduced, the imaginary component of the impedance can be increased.

  When the wireless IC chip 10 having a complex impedance Zi at 950 MHz of 20Ω−j × 183Ω (j is an imaginary unit) is used, the antenna impedance Za observed from the terminal portions 10a and 10b of the wireless IC chip 10 is set to 20Ω + j. Match impedance with x183Ω.

  When the line width of the narrow portion 5a of the matching loop circuit 5 formed of a 10 μm thick aluminum metal film pattern is 1 mm and the length of the width portion 13 is 200 mm, 160 mm, and 150 mm, the imaginary part of the impedance is measured. , 214Ω, 183Ω, and 150Ω, respectively. Therefore, the imaginary part of the impedance can be matched by using the matching loop circuit 5 having the narrow portion 5a having a line width of 1 mm and a length of 160 mm. The self-inductance of the matching loop circuit 5 in which the imaginary part of the impedance is 183Ω at 950 MHz is 31 nH. As another form of the matching loop circuit 5, it is also possible to use a one-loop matching loop circuit 5 having a length of 8 mm, a width of 32 mm, and a length of 80 mm. In this case, the length of the matching loop circuit 5 is half that of the previous example, but a narrow portion 5a having a line width of about 0.1 mm which is sufficiently thinner than 1 mm and having a large inductance per unit length is provided. Thus, a self-inductance of 31 nH can be obtained.

  Further, by adjusting the distance of the matching loop circuit 5 from the metal surface of the metal tube 1, the degree of electrical coupling between the metal tube 1 and the matching loop circuit 5 can be adjusted. The amount of field radiation is determined, and the real component of the antenna impedance Za observed from the terminal portions 10a and 10b of the wireless IC chip 10 changes. Thereby, the impedance is adjusted. The size of the appropriate electrical coupling for matching the impedance of the matching loop circuit 5 close to the impedance of the wireless IC chip 10 is adjusted in accordance with the radiation efficiency of the metal tube 1 as an antenna, so that the wireless IC chip 10 is adjusted. The real part of the antenna impedance Za observed from the terminal parts 10a and 10b is set to 20Ω, which is the value of the real part of the complex impedance of the wireless IC chip 10.

  In this way, the length and line width of the narrow portion 5a of the matching loop circuit 5 and the distance from the metal surface of the metal tube 1 of the matching loop circuit 5 are adjusted, and the terminal portion 10a of the wireless IC chip 10 is adjusted. By matching the antenna impedance Za observed from 10b with the impedance Zi of the wireless IC chip 10, it is possible to efficiently supply power from the wireless IC chip 10 to the metal cylinder 1 and to radiate electromagnetic waves from the metal cylinder 1. it can.

DESCRIPTION OF SYMBOLS 1 ... Metal cylinder 1a ... Cut part 2 ... Inlet (printed wiring board)
DESCRIPTION OF SYMBOLS 3 ... Metal pattern layer 4 ... IC tag antenna part 5 ... Matching loop circuit 5a ... Narrow part 5b ... Wide part 10 ... Wireless IC chip 10a, 10b ... Wireless current to the current _I 3 · · · IC tag antenna unit flowing through the current _I 2 · · · matching loop circuit 5 flowing through the inner surface of the terminal portion H · · · field _I 1 · · · thimble of use IC chip Za · ..Antenna impedance Zi: wireless IC chip impedance λ / 2: half wavelength of electromagnetic field

Claims (2)

  A wireless IC tag comprising a printed wiring board formed with a metal tube having both ends opened, a wireless IC chip, and a matching loop circuit wiring having a terminal portion electrically connected to the wireless IC chip. A wiring board is installed inside the metal tube, a part of the wiring of the matching loop circuit is brought close to the inner surface of the metal tube and electromagnetically coupled, and the antenna impedance including the metal tube is wirelessly transmitted by the matching loop circuit. A wireless IC tag characterized by being matched to an IC chip for use.   2. The wireless IC tag according to claim 1, wherein an IC tag antenna portion that electromagnetically couples to the matching loop circuit is formed on the printed wiring board.

Images