JP2004295297A - Radio tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio tag configured so as to be able to make communication in a plurality of frequency bands. <P>SOLUTION: In this radio tag 1 constituted of a substrate, an antenna 3 formed on the substrate and an IC chip 2, the antenna 3 is formed of a first conductor part shaped like a line which is almost 1/2 wavelength long and receives power supply at its central part and the second and third conductors projected to almost perpendicular directions in the middle of the first conductor parts. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless tag capable of holding at least one IC chip and an antenna therein and communicating data wirelessly.
[0002]
[Prior art]
A wireless tag including an IC capable of storing information and an antenna 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 more and do not have a power supply inside have a long communicable distance with the interrogator and are relatively inexpensive. It is considered. Such a wireless tag is disclosed in Patent Document 2.
[0003]
[Patent Document 1]
Japanese Patent No. 25535641 [Patent Document 2]
Japanese Patent Application 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 is used in which radio waves from the interrogator are converted to direct current by a diode or a capacitor inside the IC to obtain a voltage. When a power supply is provided inside the wireless tag, a button-type battery, a film battery, a large-capacity capacitor, or the like is used as the power supply.
[0005]
The communication distance between the wireless tag and the interrogator increases as the transmission power of the radio wave used for communication between the wireless tag and the interrogator increases. Further, the lower the communication frequency, the smaller the propagation loss in the air, and thus the longer the communication distance. However, there are regulated values for radio wave frequencies that can be used and their output levels, which are set in each country. Among the regulated values set in each country, the frequency and transmission power at which the maximum effect can be obtained 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 illustrating impedance characteristics of the antenna of the conventional wireless tag illustrated in FIG. As shown in FIG. 11, in a conventional wireless doug, matching is measured only in a certain frequency band of an IC chip and an 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 complies with the regulation value of each country, the radio wave used may differ from country to country. In that case, a situation may occur in which a wireless tag used in accordance with the regulations of one country cannot be used in another country due to a regulatory problem. 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 by another wireless communication device. 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, it is expected that wireless LANs and wireless tags will be used in similar environments, and there is 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. The IC chip includes a storage area for storing data and a circuit unit for controlling transmission and reception. In order to support different frequency bands, a main circuit of the circuit unit is a circuit that operates in different frequency bands.
[0011]
By designing the impedance of the antenna to match the impedance of the IC chip in a plurality of frequency bands to be used, a wireless tag operating in a plurality of frequency bands can be obtained. As a method of adjusting the impedance of the antenna, a method of adjusting an antenna pattern, combining a dielectric or a magnetic material, or the like is used.
[0012]
That is, the present invention is a wireless tag including a substrate, an antenna formed on the substrate, and an IC chip, wherein the impedance can be matched in a plurality of frequency bands.
[0013]
Further, the present invention is the wireless tag in which the antenna is formed on a dielectric or a magnetic material.
[0014]
Further, according to the present invention, in the wireless tag, 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.
[0015]
In the wireless tag according to the present invention, one of 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. is there.
[0016]
Further, according to the present invention, the antenna has a line shape having a length of approximately 波長 wavelength, and a first conductor portion to which power is supplied at a central portion thereof, and an electrical connection with the first conductor portion. , A wireless tag formed by a second conductor and a third conductor which are substantially perpendicular to each other.
[0017]
Also, the present invention is characterized in that the antenna has a loop shape having a length of approximately 波長 wavelength, a first conductor portion receiving power at a center of one side of the loop shape, And a substantially L-shaped second conductor electrically connected to the vicinity of a power supply point of the wireless tag.
[0018]
Also, the present invention is characterized in that the antenna has a loop shape having a length of about 波長 wavelength and having substantially parallel opposite sides, and a first conductor portion which receives power at a center of one side of the loop shape. , And a line-shaped second conductor disposed near the first conductor.
[0019]
BEST MODE FOR CARRYING OUT 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 having a length of approximately 波長 wavelength, a length of 160 mm, and a first conductor portion to which power is supplied at a central portion thereof, and a direction substantially perpendicular to the first conductor portion. And a second conductor and a third conductor. Further, 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 ohm. FIG. 2 is a diagram illustrating impedance characteristics of the antenna of the wireless tag illustrated in FIG. As shown in FIG. 2, it is 50 ohms at 915 MHz and 50 + j2 ohms at 2450 MHz (j2 indicates the imaginary part of the impedance). In other words, the impedances of the IC chip and the antenna are almost matched in the two bands of 915 MHz and 2450 MHz, and the wireless tag can communicate at the frequencies of these two bands.
[0022]
(Embodiment 2)
FIG. 3 is an explanatory diagram of the wireless tag according to the second embodiment of the present invention. In FIG. 3, the antenna 3 has a loop shape having a length of approximately 波長 wavelength and a length of 160 mm, and is supplied with power at the center of one long side of the loop shape having substantially parallel opposite sides. The wireless tag is formed by an L-shaped second conductor electrically connected to the vicinity of the feeding points 4a and 4b.
[0023]
FIG. 4 is a diagram showing the impedance characteristics of the wireless doug IC chip of FIG. As shown in FIG. 4, the impedance of the IC chip is 55 + j110 ohm at 915 MHz and 30 ohm 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 ohm at 915 MHz and 30-j2 ohm at 2450 MHz, and the impedance of the IC chip and the antenna is almost matched.
[0025]
(Embodiment 3)
FIG. 6 is an explanatory diagram of the wireless tag according to the third embodiment of the present invention. In FIG. 6, the antenna 3 has a rectangular shape having a length of about 波長 wavelength, a length of 50 mm, and a first conductor receiving power at the center of one long side of the rectangular shape. The wireless tag is formed by a second conductor portion, which is disposed in parallel with a long side of the first conductor portion and has a substantially linear shape of a half wavelength.
[0026]
FIG. 7 is a diagram showing impedance characteristics of the wireless doug IC chip of 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 ohm at 2450 MHz and 10-j32 ohm at 5800 MHz, and the impedance of the IC chip and the antenna are almost matched.
[0028]
(Embodiment 4)
FIG. 9 is an explanatory diagram of the wireless tag according to the fourth embodiment of the present invention. The wireless tag of FIG. 9 is a wireless tag including a substrate, an antenna formed in the shape of the substrate, and an IC chip, wherein the antenna has a rectangular shape having a length of about 波長 wavelength, A first conductor that receives power at the center of one of the long sides of the square, and an L-shaped second conductor that is electrically connected in the vicinity of the power supply point of the first conductor; This is a wireless tag formed by: The wireless 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 operating in the 900 MHz band and the 2450 MHz band, data written by a 900 MHz radio wave in one country can be transmitted by a 2450 MHz radio wave even when the use of the 900 MHz radio wave is not permitted in another country. Data can be read. If it is determined that there is much noise in the 900 MHz band, the frequency can be switched to the 2450 MHz band to read data. 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 a first embodiment of the present invention.
FIG. 2 is a diagram illustrating impedance characteristics of an antenna in the wireless tag illustrated in FIG. 1;
FIG. 3 is an explanatory diagram of a wireless tag according to a second embodiment of the present invention.
FIG. 4 is a diagram showing impedance characteristics of an IC chip in the wireless tag shown in FIG. 3;
FIG. 5 is a diagram illustrating impedance characteristics of an antenna in the wireless tag illustrated in FIG. 3;
FIG. 6 is an explanatory diagram of a wireless tag according to a third embodiment of the present invention.
FIG. 7 is a diagram illustrating impedance characteristics of an IC chip in the wireless tag illustrated in FIG. 6;
FIG. 8 is a diagram illustrating impedance characteristics of an antenna in the wireless tag illustrated 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 (7)

A wireless tag comprising a substrate, an antenna formed on the substrate, and an IC chip, wherein impedance matching is achieved in a plurality of frequency bands. The wireless tag according to claim 1, wherein the antenna is formed on a dielectric or a magnetic material. 3. 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. . 3. The wireless tag according to claim 1, wherein one of 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. . The antenna has a line shape having a length of about 波長 wavelength, and a first conductor portion to which power is supplied at a central portion thereof, and an electrical connection with the first conductor portion, and the antenna extends in a substantially right angle direction. The wireless tag according to any one of claims 1 to 4, wherein the wireless tag is formed of a second conductor and a third conductor. The antenna has a loop shape having a length of about ほ ぼ wavelength, a first conductor part to be supplied with power, and a substantially L-shaped part electrically connected in the vicinity of a feed point of the first conductor part. The wireless tag according to any one of claims 1 to 4, wherein the wireless tag is formed with the second conductor. The antenna has a loop shape having a substantially parallel opposite side having a length of about 波長 wavelength, and a first conductor portion receiving power supply at a center portion of the opposite side, and a first conductor portion near the first conductor portion. The wireless tag according to any one of claims 1 to 4, wherein the wireless tag is formed by a line-shaped second conductor portion arranged side by side with the opposite side.

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