JP4097139B2

JP4097139B2 - Wireless tag

Info

Publication number: JP4097139B2
Application number: JP2003084384A
Authority: JP
Inventors: 義則及川; 信一大友; 昌池田
Original assignee: Ｎｅｃトーキン株式会社
Priority date: 2003-03-26
Filing date: 2003-03-26
Publication date: 2008-06-11
Anticipated expiration: 2023-03-26
Also published as: JP2004295297A

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless tag that holds at least one IC chip and an antenna therein and can wirelessly communicate data.
[0002]
[Prior art]
A wireless tag including an IC and an antenna capable of storing information can transmit and receive data to and from a wireless device called an interrogator by radio waves. Such a wireless tag is disclosed in Patent Document 1, for example. In particular, wireless tags that use a radio frequency of 300 MHz or higher and do not have a power source inside have a long communicable distance with the interrogator and are relatively inexpensive, so they can be used for barcode replacement applications, etc. It is considered. Such a wireless tag is shown in Patent Document 2.
[0003]
[Patent Document 1]
Japanese Patent No. 2555361 [Patent Document 2]
Japanese Patent Laid-Open No. 2002-298106
As a power source for driving the IC of the wireless tag, when there is no power source inside the wireless tag, a method of obtaining a voltage by converting radio waves from the interrogator into direct current by a diode or a capacitor inside the IC is taken. When the wireless tag has a power supply, a button-type battery, a film battery, a large-capacity capacitor, or the like is used as the power supply.
[0005]
As the radio wave used for communication between the wireless tag and the interrogator increases in transmission power, the communication distance between the wireless tag and the interrogator becomes longer. Further, the lower the communication frequency, the smaller the propagation loss in the air, and the longer the communication distance. However, with regard to the frequency of radio waves that can be used and their output levels, there are regulatory values set for each country, and the frequency and transmission power that provide the maximum effect among the regulatory values set for each country. Is selected, and a communication system between the wireless tag and the interrogator is designed.
[0006]
FIG. 10 is an explanatory diagram of a conventional wireless tag. FIG. 11 is a diagram showing impedance characteristics of the antenna of the conventional wireless tag shown in FIG. As shown in FIG. 11, in the conventional wireless doug, matching is measured only in one frequency band between the IC chip and the antenna.
[0007]
[Problems to be solved by the invention]
Since the frequency of the radio wave used for communication between the wireless tag and the interrogator conforms to the regulation value of each country, the radio wave used may vary depending on the country. In that case, a situation occurs in which a wireless tag that is used in accordance with the regulations of a certain country cannot be used in another country due to regulatory problems. For example, as of January 2003, the 915 MHz band can be used in the United States, but cannot be used in Japan.
[0008]
There is also a problem of radio wave interference. The band that can be used for the wireless tag may be used for other wireless communication devices. In such a case, mutual communication may be affected. For example, the 2.45 GHz band can be used for wireless tags, but is also used in various devices such as wireless LANs and microwave ovens. In particular, a wireless LAN and a wireless tag are expected to be used in a similar environment and have a problem of mutual interference.
[0009]
An object of the present invention is to provide a wireless tag configured to enable communication in a plurality of frequency bands.
[0010]
[Means for Solving the Problems]
The wireless tag of the present invention includes one IC chip and an antenna for transmitting and receiving data. Of these, the IC chip includes a storage area for holding data and a circuit unit for controlling transmission and reception. In order to cope with different frequency bands, the main circuit of the circuit section is a circuit that operates in different frequency bands.
[0011]
By designing the antenna impedance to match the impedance of the IC chip in a plurality of frequency bands to be used, a wireless tag that operates in a plurality of frequency bands can be obtained. As means for adjusting the impedance of the antenna, methods such as adjustment of the antenna pattern and combination of a dielectric material and a magnetic material are used.
[0012]
According to the present invention, there is provided a wireless tag comprising a substrate, an antenna formed on the substrate, and an IC chip, wherein the antenna has a line shape with a length of approximately ½ wavelength, and a center thereof. A plurality of frequency bands formed by a first conductor portion that receives power at a portion, a second conductor and a third conductor that are electrically connected to the first conductor portion and project in a substantially perpendicular direction. Thus, a wireless tag characterized in that impedance matching can be obtained.
Note that the second conductor portion and the third conductor portion preferably extend in different directions across the power feeding portion provided in the first conductor portion.
[0013]
According to the present invention, there is provided a wireless tag comprising a substrate, an antenna formed on the substrate, and an IC chip, wherein the antenna is fed in a loop shape having a length of approximately ½ wavelength. It is formed by a first conductor portion to be received and a substantially L-shaped second conductor portion electrically connected to the first conductor portion, and impedance matching can be obtained in a plurality of frequency bands. A wireless tag is obtained.
Note that the second conductor portion is preferably electrically connected to the vicinity of the feeding point at the center of one side of the first conductor portion.
[0014]
According to the present invention, the wireless tag includes a substrate, an antenna formed on the substrate, and an IC chip. The antenna has a length of about ½ wavelength and a substantially parallel opposite side. A loop-shaped first conductor portion that receives power at the center of one opposite side of the loop shape, and a line-shaped second conductor arranged in line with the opposite side in the vicinity of the first conductor portion. The wireless tag is characterized in that it is formed of a conductor portion and can match impedance in a plurality of frequency bands.
The second conductor part is preferably provided in the vicinity of the feeding point of the first conductor part.
[0015]
According to the present invention, it is possible to obtain a wireless tag characterized in that the antenna is formed on a dielectric or magnetic material.
[0016]
According to the present invention, one of the frequency bands used for communication is a frequency band of 800 MHz to 1000 MHz, and one is a frequency band of 2400 MHz to 2500 MHz.
[0017]
One of the frequency bands used for communication is a frequency band of 2400 MHz to 2500 MHz, and one is a frequency band of 5000 MHz to 6000 MHz, thereby obtaining the wireless tag.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
A wireless tag according to an embodiment of the present invention will be described with reference to the drawings.
[0020]
(Embodiment 1)
FIG. 1 is an explanatory diagram of a wireless tag according to Embodiment 1 of the present invention. The antenna 3 has a linear shape with a length of approximately ½ wavelength, a length of 160 mm, a first conductor portion that receives power at the center thereof, and a substantially perpendicular direction from the first conductor portion. Formed by the second conductor and the third conductor. In the wireless tag, the antenna is formed on a dielectric or magnetic material.
[0021]
In the wireless tag 1 of FIG. 1, the IC chip 2 and the antenna 3 in the figure are electrically connected at feed points 4a and 4b. The impedance of the antenna is adjusted to match the impedance of the IC. In FIG. 1, the impedance of the IC chip is 50 ohms. FIG. 2 is a diagram showing impedance characteristics of the antenna of the wireless tag shown in FIG. As shown in FIG. 2, 50 ohms at 915 MHz and 50 + j2 ohms at 2450 MHz (j2 represents the imaginary part of the impedance). In other words, the impedances of the IC chip and the antenna are substantially matched in the two bands of 915 MHz and 2450 MHz, and the wireless tag can communicate at the frequencies of the two bands.
[0022]
(Embodiment 2)
FIG. 3 is an explanatory diagram of a wireless tag according to the second embodiment of the present invention. In FIG. 3, the antenna 3 has a loop shape with a length of approximately ½ wavelength, the length is 160 mm, and is fed at the center of one long side of the loop shape having substantially parallel opposite sides. The wireless tag is formed of an L-shaped second conductor portion electrically connected in the vicinity of the vicinity of the feeding points 4a and 4b.
[0023]
FIG. 4 is a diagram showing impedance characteristics of the IC chip of the wireless doug shown in FIG. As shown in FIG. 4, the impedance of the IC chip is 55 + j110 ohms at 915 MHz and 30 ohms at 2450 MHz.
[0024]
FIG. 5 is a diagram showing impedance characteristics of the antenna shown in FIG. The impedance of the antenna is 53-j107 ohms at 915 MHz and 30-j2 ohms at 2450 MHz, and the impedances of the IC chip and the antenna are substantially matched.
[0025]
(Embodiment 3)
FIG. 6 is an explanatory diagram of a wireless tag according to the third embodiment of the present invention. In FIG. 6, the antenna 3 has a quadrangular shape with a length of about ½ wavelength, the length is 50 mm, and the first conductor receives power at the center of one long side of the quadrangular shape. And a second conductor portion that is arranged in parallel with the long side of the first conductor portion and has a length that is approximately ½ wavelength linear.
[0026]
FIG. 7 is a diagram showing impedance characteristics of the IC chip of the wireless doug shown in FIG. As shown in FIG. 7, the impedance of the IC chip is 30 ohms at 2450 MHz and 11 + j28 ohms at 5800 MHz.
[0027]
FIG. 8 is a diagram showing impedance characteristics of the antenna shown in FIG. The impedance of the antenna is 30-j3 ohms at 2450 MHz and 10-j32 ohms at 5800 MHz, and the impedances of the IC chip and the antenna are substantially matched.
[0028]
(Embodiment 4)
FIG. 9 is an explanatory diagram of a wireless tag according to the fourth embodiment of the present invention. The wireless tag in FIG. 9 is a wireless tag including a substrate, an antenna formed in the shape of the substrate, and an IC chip, and the antenna has a square shape with a length of about ½ wavelength, A first conductor portion that receives power at the center of one of the long sides of the quadrilateral, and an L-shaped second conductor portion that is electrically connected in the vicinity of the power supply point of the first conductor portion; It is the radio tag formed by. The radio doug shown in FIG. 9 has an antenna formed on a dielectric substrate and is matched with an IC. The impedance of the antenna is adjusted using the dielectric constant of the substrate.
[0029]
【The invention's effect】
According to the present invention, it is possible to provide a wireless tag capable of data communication in a plurality of frequency bands. Thus, for example, in the case of a wireless tag that operates in the 900 MHz band and the 2450 MHz band, data written with 900 MHz radio waves in one country can be transmitted with 2450 MHz radio waves even if use of 900 MHz radio waves is not permitted in other countries. Data can be read out. When it is determined that there is a lot of noise in the 900 MHz band, it is possible to read data by switching the frequency to the 2450 MHz band. Therefore, according to the present invention, it is possible to provide a wireless tag configured to enable communication in a plurality of frequency bands.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a wireless tag according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing impedance characteristics of an antenna in the wireless tag shown in FIG.
FIG. 3 is an explanatory diagram of a wireless tag according to a second embodiment of the present invention.
4 is a graph showing impedance characteristics of an IC chip in the wireless tag shown in FIG. 3;
5 is a graph showing impedance characteristics of an antenna in the wireless tag shown in FIG. 3;
FIG. 6 is an explanatory diagram of a wireless tag according to a third embodiment of the present invention.
7 is a graph showing impedance characteristics of an IC chip in the wireless tag shown in FIG. 6;
8 is a graph showing impedance characteristics of an antenna in the wireless tag shown in FIG. 6;
FIG. 9 is an explanatory diagram of a wireless tag according to a fourth embodiment of the present invention.
FIG. 10 is an explanatory diagram of a conventional wireless tag.
11 is a diagram showing impedance characteristics of the antenna of the conventional wireless tag shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Wireless tag 2 IC chip 3 Antenna 4a, 4b Feeding point 5 Real part of impedance 6 Imaginary part of impedance 7 Substrate

Claims

A wireless tag comprising a substrate, an antenna formed on the substrate, and an IC chip, wherein the antenna has a line shape having a length of ½ wavelength and is fed with power at a central portion thereof. 1 conductor portion and the second conductor and the third conductor that are electrically connected to the first conductor portion and project in a right angle direction, and can achieve impedance matching in a plurality of frequency bands. A wireless tag characterized by that.
A wireless tag including a substrate, an antenna formed on the substrate, and an IC chip, wherein the antenna is a loop shape having a length of ½ wavelength, and a first conductor portion that receives power supply, A wireless tag formed of an L-shaped second conductor portion electrically connected to the first conductor portion and capable of matching impedances in a plurality of frequency bands.
A wireless tag comprising a substrate, an antenna formed on the substrate, and an IC chip, wherein the antenna is a loop shape having a length of ½ wavelength and parallel opposite sides, and a center of the opposite side Impedance matching in a plurality of frequency bands, formed by a first conductor portion that receives power at a portion, and a line-shaped second conductor portion arranged side by side with the opposite side of the first conductor portion A wireless tag characterized by being able to take.
The antenna, the wireless tag according to any one of claims 1 to 3, characterized in that formed in the dielectric or on magnetic material.
5. The wireless tag according to claim 1, wherein one of frequency bands used for communication is a frequency band of 800 MHz to 1000 MHz, and one is a frequency band of 2400 MHz to 2500 MHz. Wireless tag to do.
The wireless tag according to any one of claims 1 to 4, wherein one of the frequency bands used for communication is a frequency band of 2400 MHz to 2500 MHz, and one is a frequency band of 5000 MHz to 6000 MHz. Wireless tag to do.