WO2007013152A1

WO2007013152A1 - Wireless ic tag reader

Info

Publication number: WO2007013152A1
Application number: PCT/JP2005/013737
Authority: WO
Inventors: Mitsuo Usami
Original assignee: Hitachi, Ltd.
Priority date: 2005-07-27
Filing date: 2005-07-27
Publication date: 2007-02-01
Also published as: JPWO2007013152A1

Abstract

A wireless IC tag reader (100) is provided with a reader main body (101), a coaxial cable (102) lead out from the reader main body (101), and a ceramic reader antenna (103) attached to the leading end of the coaxial cable (102). As the reader antenna (103), a high dielectric ceramic antenna used for microwave communication with a distance 5m-10km or more away is used, and the size of the antenna is, for instance, 30mm square or smaller.

Description

Specification

Wireless IC tag reader

Technical field

TECHNICAL FIELD [0001] The present invention relates to a wireless IC tag (RFID) reader that performs wireless recognition, and more particularly, to a technique for realizing miniaturization of a wireless IC tag reader.

Background art

[0002] A wireless IC tag is a non-contact type tag in which desired data is written in a memory circuit in a semiconductor chip and this data is read using a wireless IC tag reader such as a microwave. is there. This wireless IC tag is attached to various products and used for product inventory management and product quality control by using ID numbers etc. written on semiconductor chips.

[0003] Japanese Patent Application Laid-Open No. 5-166018 (Patent Document 1) discloses a technique for improving the sensitivity of a transmission / reception antenna built in a wireless contactless IC card with a battery. The non-contact IC card described in this document is composed of a memory for storing data, non-contact input / output means for inputting / outputting data without contact with the outside, and a control means for controlling them. The card body The non-contact input / output means converts the data into a radio signal, demodulates the data from the received radio signal, transmits / receives the radio signal, and transmits / receives the radio signal. It has a planar antenna that radiates the output of the transmitter / receiver unit to the outside and takes in a radio signal of external force and outputs it to the transmitter / receiver unit. The planar antenna has a dielectric part, a ground conductor provided on one side of the dielectric part, and an antenna conductor provided on the other side. According to this configuration, for example, when data from the outside is output to the memory, an external force radio signal is captured by the planar antenna and output to the transmitting / receiving unit, and the data obtained by the modem unit is output to the memory by the control means. By doing so, data wireless communication between the memory and the outside can be efficiently performed via the non-contact input / output means.

[0004] Japanese Unexamined Patent Application Publication No. 2005-167813 (Patent Document 2) discloses a technique for reducing the size of an antenna attached to a wireless IC tag. The wireless IC tag described in this document is based on It consists of a board, an IC chip mounted on it, and an antenna formed on a part of this board. The antenna has a slit that separates two connection points to the IC chip. The length of this slit is approximately 3 mm, and the width is from 0.8 mm to 1.4 mm. The data written on the wireless IC tag is read by attaching a dipole antenna with a length of about 40mm to 60mm attached to the wireless IC tag reader to the wireless IC tag substrate.

Patent Document 1: JP-A-5-166018

Patent Document 2: JP 2005-167813 A

Disclosure of the invention

Problems to be solved by the invention

[0005] In recent years, wireless IC tags have been reduced in size in accordance with the variety of articles to be applied, and accordingly, IC tag readers that read data from wireless IC tags are also required to be reduced in size. Yes. In order to read wireless IC tag data using a reader, the reader must be close to the wireless IC tag to some extent. However, for example, when a small wireless IC tag is attached inside an article, the antenna cannot be brought close to the wireless IC tag unless the reader body and antenna are small.

[0006] In the case of Patent Document 2, the data written in the wireless IC tag is read by a 40mn length attached to the wireless IC tag reader! A dipole antenna of ~ 60mm had to be in close contact with the wireless IC tag, making it difficult to secure a communication distance between the wireless IC tag and the wireless IC tag reader. This is because when a dipole antenna is used, the electromagnetic energy radiated from the reader is uniformly distributed throughout the antenna, resulting in a decrease in reading sensitivity.

An object of the present invention is to provide a technology for promoting the miniaturization of a wireless IC tag reader.

Another object of the present invention is to provide a technique for improving the reading sensitivity of a small wireless IC tag reader.

[0009] The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings. Means for solving the problem

[0010] Among the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

[0011] The present invention includes a reader body and a reader antenna connected to the reader body, and for wireless IC tags that read data of a wireless IC tag using microwaves transmitted from the reader body force. A reader, wherein the reader antenna is a ceramic antenna.

The invention's effect

[0012] The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

[0013] A wireless IC tag reader can be reduced in size. In addition, the reading sensitivity of small wireless IC tag readers can be improved.

Brief Description of Drawings

FIG. 1 is a perspective view showing a wireless IC tag reader according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a reader antenna of a wireless IC tag reader according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a wireless IC tag reader provided with a dipole antenna.

FIG. 4 is a graph showing the relationship between the distance of the reader force and the electromagnetic field intensity.

FIG. 5 is an explanatory diagram showing that a dipole antenna is equivalent to an assembly of many small antennas.

FIG. 6 is a perspective view showing a method of reading data written in a wireless IC tag using a wireless IC tag reader according to an embodiment of the present invention.

FIG. 7 is a perspective view showing a reader for a wireless IC tag according to another embodiment of the present invention.

FIG. 8 is a perspective view showing a wireless IC tag reader according to another embodiment of the present invention.

FIG. 9 is a side view showing a wireless IC tag reader according to another embodiment of the present invention.

FIG. 10 is a side view showing a wireless IC tag reader according to another embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

[0016] (Embodiment 1)

FIG. 1 is a perspective view showing a wireless IC tag reader according to the present embodiment. The wireless IC tag reader 100 includes a reader body 101, a coaxial cable 102 drawn from the reader body 101, and a ceramic reader antenna 103 attached to the tip of the coaxial cable 102. The reader antenna 103 can be a high dielectric ceramic antenna used for microwave communication with a distance of 5 m to 10 km or more, such as a wireless LAN, Bluetooth, and a cellular phone, and is not particularly limited. The dimension is, for example, 30 mm square or less.

[0017] With IC tags, there is a demand for miniaturization of the reader antenna as well as the size of the IC tag. The IC tag size can be reduced by reducing the IC chip size and the antenna connected to it. However, if the antenna is downsized, the distance from the optimum length of resonance is shifted to the smaller one, so the communication distance with the reader antenna is reduced. However, there is a strong demand for smaller IC tag sizes in areas where privacy protection is not required for long communication distances. In addition, small antenna IC tags that have advantages over bar codes, such as high resistance to dirt on the surface even when the communication distance is short, are useful.

[0018] However, even if the antenna size of the IC tag is reduced, the communication distance cannot be secured in the vicinity of 30 mm unless the reader antenna is changed. Therefore, the reader antenna must be connected to a high-frequency transmission source to efficiently improve electromagnetic energy density and radiate electromagnetic waves in the air. If a large dipole antenna is simply reduced in size, it will not be able to radiate electromagnetic waves efficiently because it will deviate from the resonant length of the antenna. Therefore, by filling the space between the periphery of the dipole antenna and the ground with a material having a high relative dielectric constant, it is possible to form an antenna without reducing the efficiency even if the size of the dipole antenna is reduced. It becomes. For this reason, a ceramic material with a large relative dielectric constant has characteristics suitable for the material of the reader antenna in this case. By efficiently downsizing, per unit area The electromagnetic energy density can be increased, the communication distance can be extended, and a user-friendly small IC tag system can be formed. Ceramic antennas are industrial parts that are frequently used in wireless LAN and are economically available parts. In the present application, it is possible to use an antenna having such a good feature for an IC tag system for near-field communication purposes to demonstrate its effectiveness.

[0019] In a ceramic antenna, it is easy to make the relative dielectric constant of the ceramic substrate to be 4 or more. When used as an antenna material, the wavelength can be shortened by the square root of the relative permittivity. Therefore, if the relative permittivity is used, the antenna can be shortened by half. An antenna needs to be an integral number of wavelengths in order to form a resonant circuit. In general, it is efficient to use a half wavelength. Therefore, in an antenna using a frequency in the microwave band with a center frequency of 2.45 GHz, the light speed divided by a multiple of 2.45 GHz is a half wavelength, which is about 60 mm. In the case of relative permittivity, the square root of 4 is 2, so it is about 30 mm. Ceramic materials can have a relative dielectric constant of 4 or more depending on the composition. For example, when the relative permittivity is 36, the square root force is obtained, and a 10 mm antenna can be obtained with a short wavelength.

As shown in FIG. 2, a ground pattern 104 and a signal pattern 105 are formed on the surface of the reader antenna 103. When high-frequency energy is applied between the ground pattern and the signal pattern, a resonance phenomenon appears, and a strong line of electric force is generated between the ground pattern and the signal pattern. On the other hand, if either the ground pattern or the signal pattern is missing, strong lines of electric force cannot be present, and the radiation of electromagnetic waves becomes weaker or the effect of effectively radiating does not appear. The signal pattern 105 is a folded pattern in order to reduce the outer dimensions of the reader antenna 103 that resonates according to the thickness and dielectric constant of the ceramic.

Next, the principle of the reader antenna 103 will be described. FIG. 3 is a perspective view showing a wireless IC tag reader equipped with a dipole antenna. The wireless IC tag reader 200 includes a reader body 201, a coaxial cable 202 drawn from the reader body 201, and a dipole antenna 203 attached to the tip of the coaxial cable 202. The length of the dipole antenna 203 is about 60 mm depending on the surrounding dielectric constant. Normal Dipoles have a relative permittivity of 1 because they are surrounded by air. Therefore, in an antenna that uses a frequency in the microwave band with a center frequency of 2.45 GHz, the light speed divided by a multiple of 2.45 GHz is a half wavelength, which is about 60 mm. The coaxial cable used here is suitable for transmitting high-frequency transmission waves efficiently without generating electric lines of force around them, and serves as a line.

[0022] As shown in Equation 1, in general, the strength (H φ) of the electromagnetic field that also emits the reader force is expressed as the sum of the strength of the radiated electromagnetic field (jkZr) and the strength of the induction electromagnetic field (lZr ² ). Is done.

Formula 1

[0023]

Formula 1

In the distance

Dominant term

Nearly dominant term

[0024] There is a large characteristic difference between the radiated electromagnetic field (jkZr) and the induction electromagnetic field (lZr ² ). As shown in Fig. 4, the radiated electromagnetic field (jkZr) is a dominant term in the distance. The induction electromagnetic field (lZr ² ) is a dominant term in the near field. The intensity of the radiated electromagnetic field (jkZr) and the intensity of the induction electromagnetic field (lZr ² ) are the same when the distance from the reader is equal to the wavelength divided by 2π. For example, in the case of a high frequency of 2.45 GHz, the wavelength is about 122 mm. Therefore, when this wavelength is divided by 2π, it is about 19 mm, so that the induced electromagnetic field becomes dominant when the distance from the reader is 19 mm or less. On the other hand, when the distance of the leader force is 19mm or more, the induction electromagnetic field is attenuated and the radiated electromagnetic field becomes dominant.

The dipole antenna 203 having a length of 40 mm to 60 mm shown in FIG. 2 is considered to be an assembly of a large number of small antennas as shown in FIG. That is, the length is 4mm It can be considered that a small antenna 303 of ˜6 mm is connected to the coaxial cable 302 and exists in parallel. Therefore, when the energy supplied from the reader main body 201 to the dipole antenna 203 through the coaxial cable 202 is the same, the induction electromagnetic field, which is a dominant term in the near field, is uniformly dispersed in the dipole antenna 203. For these reasons, it is difficult for a conventional wireless IC tag reader equipped with the dipole antenna 203 to secure a communication distance between the wireless IC tag and the dipole antenna 203.

On the other hand, since the ceramic reader antenna 103 attached to the wireless IC tag reader 100 of the present embodiment has a size of, for example, 30 mm square or less, such energy dispersion is unlikely to occur. By setting the reader antenna to 30 mm or less, it is possible to supply electromagnetic waves with more than double the energy of the antenna unit area force to the IC tag compared to the conventional 60 mm reader antenna. For this reason, an IC tag with a small antenna in the vicinity of the reader antenna can obtain a spatial electromagnetic energy more than double that of a reader antenna of about 60 mm. The communication distance between the reader antenna and the IC tag can be increased by the square root of the electromagnetic energy. It is possible here to increase the communication distance by about 1.4 times the square root of 2 by the space electromagnetic energy that doubles the energy of the reader antenna.

FIG. 6 is a perspective view showing a method of reading data written on the wireless IC tag using the wireless IC tag reader 100 of the present embodiment. The wireless IC tag 400 includes a substrate 401, a small antenna 402 formed on one surface of the substrate 401, and an IC chip 403 mounted on the substrate 401.

[0028] If the reader antenna 103 of the wireless IC tag reader 100 has a size of 30 mm square or less, the wireless IC tag 400 can be read efficiently by making the dimension of the wireless IC tag 400 30 mm square or less. Become. The wireless IC tag 400 having a size of 30 mm square or less is small and resistant to reflection if dirty, so it can be used by attaching it to an article with a small external dimension such as a small bottle or straw.

[0029] (Embodiment 2)

FIG. 7 is a perspective view showing the wireless IC tag reader according to the present embodiment. The wireless IC tag reader 110 of this embodiment includes a ground pattern 111 made of copper foil and a signal pattern. A reader antenna 103 is attached to a substrate 113 having a turn 112. The reader antenna 103 is composed of a high dielectric ceramic antenna having the same dimension as that of the first embodiment, for example, 30 mm square or less.

[0030] The substrate 113 functions as an antenna together with the reader antenna 103, and the ground pattern 111 also serves as a resonance element for radiating electromagnetic waves. Since a high-speed current flows through the darling pattern 111 and the signal pattern 112 that play a role as a waveguide, it is necessary to make them both parallel patterns and a distributed constant line.

[0031] According to the present embodiment, since the induction electromagnetic field can be densified, the reading sensitivity of the wireless IC tag reader 110 can be improved.

[Embodiment 3]

FIG. 8 is a perspective view showing the wireless IC tag reader of the present embodiment. The wireless IC tag reader 120 of this embodiment is characterized by the structure of the coaxial cable 122 to which the reader antenna 103 is attached. The coaxial cable 122 has a dielectric 124 around a signal line 123 and an outer periphery thereof covered with a metal layer 125, and functions as an antenna together with the reader antenna 103. The reader antenna 103 is composed of a high dielectric ceramic antenna having the same dimension as that of the first embodiment, for example, 30 mm square or less.

The coaxial cable 122 itself generates an electromagnetic field only between the signal line 123 and the metal layer 125, and thus there is no direct resonance relationship with the reader antenna 103, but the reader body 101 and the reader antenna It is effective for expanding the distance to 103. As a result, even when the wireless IC tag reader 120 is mounted inside a narrow article, the reader antenna 103 can be brought close to a distance of about 19 mm.

[0034] In the coaxial cable 122, since a standing wave is generated between the end on the reader body 101 side and the end on the reader antenna 103 side, the length thereof is set to an integral multiple of one half of the wavelength. Then efficiency improves.

[Embodiment 4]

FIG. 9 is a side view showing the wireless IC tag reader of the present embodiment. The wireless IC tag reader 130 according to the present embodiment is characterized in that the reader main body 101 and the reader antenna 103 connected thereto are elongated and attached to the tip of the stick 131. Stick 131 The diameter and length can be changed depending on the article to which the wireless IC tag reader 120 is attached. The reader antenna 103 is formed of a high dielectric ceramic antenna having the same dimension as that of the first embodiment, for example, 30 mm square or less.

[0036] For example, when a small wireless IC tag is attached to each of plate-like articles having different plane sizes, and these plate-like articles are stacked in a plurality of stages, the wireless IC tag is deep in some articles. However, the wireless IC tag reader cannot be brought close to the wireless IC tag. In such a case, the data written in the wireless IC tag can be read by using the wireless IC tag reader 130 of the present embodiment in which the reader antenna 103 is attached to the tip of the elongated stick 131. It becomes.

[0037] (Embodiment 5)

FIG. 10 is a side view showing the wireless IC tag reader of the present embodiment. The wireless IC tag reader 140 of this embodiment is characterized in that the reader main body 101 and the reader antenna 103 connected thereto are attached to a part of the ring 141. The dimensions of the ring 141 are almost the same as the ring and can be fitted on the finger. The reader antenna 103 is composed of a high dielectric ceramic antenna having the same dimension as that of the first embodiment, for example, 30 mm square or less.

[0038] For example, when a wireless IC tag is attached to the surface of a small article, thin paper, or the like, the wireless IC tag reader 130 according to the present embodiment is simply brought close to the article or paper with the finger fitted. Thus, data can be easily read. Try to make the ring 141 a little larger so that it fits on your arm.

[0039] Further, the wireless IC tag reader 130 of the present embodiment may be attached with a small wireless device that wirelessly communicates with a nearby terminal, for example, by driving the wireless device with a battery attached to the surface of the ring 141. Good. In this case, by incorporating a sensor that detects when the reader antenna 103 approaches the wireless IC tag in the small wireless device, the wireless device can be operated only when necessary, thus reducing battery consumption. be able to.

[0040] While the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. There's something that's ugly! / ... Industrial applicability

The present invention can be applied to a wireless IC tag reader that reads data of a wireless IC tag using microwaves.

Claims

The scope of the claims

[1] A wireless IC tag reader that includes a reader main body and a reader antenna connected to the reader main body, and reads data of the wireless IC tag using microwaves transmitted from the reader main body. A reader for a wireless IC tag, wherein the reader antenna is a ceramic antenna.

2. The radio frequency IC tag reader according to claim 1, wherein the frequency of the microwave is 2.45 GHz.

[3] The wireless IC tag reader according to claim 1, wherein an outer dimension of the reader antenna is 30 mm square or less.

[4] The wireless IC tag reader according to claim 3, wherein the external dimension of the wireless IC tag is 30 mm square or less.

5. The wireless IC tag reader according to claim 1, wherein the reader antenna is attached to a substrate having a ground pattern and a signal pattern.

6. The wireless IC tag reader according to claim 1, wherein the reader antenna is connected to the reader body via a coaxial cable.

7. The wireless IC tag reader according to claim 1, wherein the reader body is attached to one end of a stick.

8. The wireless IC tag reader according to claim 1, wherein the reader body is attached to a ring.