JP2007249620A - Wireless tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless tag preventing a communication function from being degraded in close different communication frequency bands. <P>SOLUTION: A loop-like electrode part 104 is provided with a feed point 106 connected to an IC chip 103, a main radiation electrode part 105 is extended and connected from a position a specified distance away from the feed point 106, and the band of the wireless tag is widened. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless tag having an IC chip and an antenna and capable of communicating data wirelessly.

  A wireless tag including an IC and an antenna that can store information can transmit and receive data to and from a wireless device called a reader / writer by radio waves. In particular, wireless tags that use a radio frequency of 300 MHz or higher and do not have a power supply inside have a long communicable distance with the reader / writer and are relatively inexpensive, so they can be used for barcode replacement. It is considered.

  When the wireless tag does not have a power source, a method of obtaining a voltage by converting a radio wave from the reader / writer into a direct current using a diode or a capacitor inside the IC is employed. When the wireless tag has a power source, a button-type battery, a film-like battery, a large-capacity capacitor, or the like is used as an IC driving power source.

  The radio wave used for communication between the wireless tag and the reader / writer has a longer communication distance between the wireless tag and the reader / writer as the transmission power increases. 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 reader / writer is designed.

  Furthermore, even within the same country, a plurality of frequency bands are defined depending on the application. For example, in Japan, a plurality of frequency bands having completely different communication distances such as 2.45 GHz band and 950 MHz band are used.

  Accordingly, the wireless tag needs to be designed differently for each application, that is, for each frequency band to be used, and this has been a factor in increasing costs in terms of both design costs and manufacturing costs.

  In order to solve such a problem, a wireless tag in which an antenna pattern is configured so that the impedance of an antenna matches an IC chip having a circuit capable of transmitting and receiving in a plurality of frequency bands completely different from each other has been proposed. . Such a wireless tag is disclosed in Patent Document 1, for example.

  On the other hand, the regulated frequency band in the United States corresponding to the 950 MHz band (UHF band) in Japan is the 915 MHz band, and the 869 MHz band is standard in Europe.

  In general, a wireless tag is designed so that impedance matching is optimized in a specific frequency band. However, the impedance of an IC chip used for a wireless tag has a large imaginary number, it is difficult to achieve impedance matching with an antenna, and the bandwidth capable of matching is narrow.

  Therefore, even if the frequency bands are close, wireless tags designed for use in Japan, for example, in the United States and Europe generally have a poor communication distance even if they cannot be used or can be used. do not do.

  Furthermore, in order to enable transmission / reception in a plurality of frequency bands that are completely different from each other with only a single wireless tag, as described above, a plurality of IC chips or a complicated circuit configuration is used. It is necessary, and becomes a factor of cost increase in both the design cost and the manufacturing cost.

JP 2004-295297 A

  The technical problem of the present invention is to provide a wireless tag in which communication functions are not deteriorated in adjacent and different communication frequency bands.

  The present invention relates to a wireless tag that can communicate satisfactorily in a communication frequency band of several tens of MHz to several hundreds of MHz, and includes a loop electrode, that is, a feed point in which an IC chip is connected to a loop antenna, By extending and connecting the main radiation electrode from a position that is a specific distance from the wireless tag, a wide range of wireless tags is realized.

  According to the present invention, the inventor has found through experiments that the loop electrode and the main radiation electrode are appropriately arranged, that is, the main radiation is spaced apart from the feeding point of the IC chip provided on the loop electrode. By arranging and connecting the electrodes, the reactance of the impedance of the antenna is flat in a wide frequency band, that is, based on the knowledge that impedance can be matched in a wide frequency band.

  Furthermore, the main radiation electrode functions as a so-called dipole antenna by extending and connecting two main electrodes from a loop electrode.

  According to the present invention, there is provided a wireless tag having at least an IC chip and the antenna part, wherein the antenna part is stretched and connected from the loop electrode having a feeding point formed by connecting the IC chip. The main radiating electrode has an open end, and the main radiating electrode is stretched and connected from a position one-fourth to three-fourths of the entire length of the loop electrode from the feeding point. A wireless tag is obtained.

  According to the present invention, there is obtained a wireless tag characterized in that the main radiation electrode is formed in a straight line.

  According to the present invention, there is obtained a radio tag characterized in that the main radiation electrode is formed in a curved shape.

  According to the present invention, there is obtained a radio tag characterized in that the main radiation electrode has a wide portion at the open end.

  According to the present invention, there is obtained the wireless tag according to any one of claims 1 to 4, wherein two main radiation electrodes are formed.

  According to the present invention, it is possible to obtain a wireless tag characterized in that the loop electrode and the main radiation electrode are arranged to be line-symmetric.

  According to the present invention, in a close communication frequency band existing in a frequency band separated by several tens of MHz to several hundred MHz, there is little deterioration of the communication distance for each communication frequency, and wireless communication is possible at any communication frequency. A tag is obtained.

  That is, the wireless tag according to the present invention has improved antenna impedance characteristics, particularly reactance, and a wide communication frequency bandwidth for impedance matching with the IC chip. Therefore, even if different communication frequencies exist in a close region, a wireless tag capable of supporting a wideband frequency having a certain communication performance at each communication frequency can be obtained.

  The wireless tag according to the present invention has an IC chip and electrodes or antennas electrically connected to the IC chip at at least two locations, and one of the connection points between the IC chip and the antenna is a feeding point, The other location functions as a ground point. Further, a loop electrode, that is, a loop antenna is connected to the IC chip, and the main radiation is at any one of the positions from the feed point on the loop antenna to one-fourth to three-fourths of the total length of the loop antenna. Electrodes, that is, antennas that function as, for example, dipole antennas are stretched and connected to form the entire antenna.

  For example, the wireless tag uses a conductive material such as copper, aluminum, silver, etc. on a substrate made of a resin such as a glass epoxy substrate, PET (polyethylene terephthalate), polyimide, or paper, and a general method such as etching and printing. An antenna is formed by the antenna forming means, and the antenna and the IC chip are electrically connected and formed by a general mounting technique such as wire bonding or flip chip mounting.

  The shapes of the loop electrode and the main radiation electrode can be modified to suit various conditions. That is, the loop electrode may be any shape that forms a loop, such as a circle, an ellipse, or a quadrilateral, and may be appropriately selected depending on the shape of the wireless tag, the application, the nature of the substrate, and the like. The main radiation electrode may be appropriately selected depending on the shape of the wireless tag, the application, the nature of the substrate, etc., such as a straight line, a curved line, and a meander shape. In order to reduce the overall size of the wireless tag, a bent shape is preferable.

  Further, in order to flatten the impedance characteristics of the antenna in a wide frequency band, the loop electrode and the main radiation electrode are preferably formed so as to be line symmetric. In particular, it is particularly preferable that the entire antenna formed from the loop-shaped electrode and the main radiation electrode is formed with respect to the line including the feeding point.

  As a result of various experiments, it has been found that the reactance portion of the impedance characteristic, in particular, becomes flat in a wide frequency band as the connecting portion between the loop electrode and the main radiation electrode is moved away from the feeding point. In particular, this phenomenon becomes prominent when the main radiation electrode is connected beyond the vicinity of a quarter of the entire length of the loop electrode from the feeding point on the loop electrode. Therefore, the antenna is formed by arranging the connection portion of the loop electrode and the main radiation electrode at any one of the positions from one quarter to three quarters of the entire length of the loop electrode.

  It is particularly preferable that the connecting portion is disposed at a position farthest from the feeding point, that is, in the vicinity of one half of the entire length of the loop electrode.

  Even if the widths of the loop electrode and the main radiation electrode are uniform or a wide portion is provided, the same effect can be obtained. However, as a result of various experiments, it has been found that by providing a wide portion in the vicinity of the open end of the main radiation electrode, the impedance characteristics of the antenna, particularly the reactance, is flattened in a wider frequency band. Accordingly, the shape of the wide portion is preferably selected as appropriate depending on the shape of the wireless tag, the application, the properties of the base material, etc., and the impedance characteristics are preferably adjusted. In particular, providing a fan-shaped wide portion in the vicinity of the open end is particularly preferable because impedance characteristics can be flattened in a wider frequency band and contributes to miniaturization of the wireless tag.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
FIG. 1 is a diagram showing an embodiment of the present invention.

  The wireless tag 100 includes an antenna unit 101, a base material 102, and an IC chip 103. The antenna unit 101 includes a loop electrode unit 104 and a main radiation electrode unit 105. The external dimensions of the wireless tag 100 are 10 mm long and 100 mm wide.

  The antenna unit 101 is formed by printing a conductive paint mainly composed of silver on a base material 102 made of a glass epoxy substrate having a thickness of 0.4 mm, and further performing gold plating. The antenna unit 101 and the IC chip 103 are connected by wire bonding.

  The IC chip 103 is connected to the loop electrode unit 104. From the feeding point 106 of the IC chip 103 on the loop-shaped electrode portion 104, a point A that is 3/8 as the outer peripheral distance of the loop-shaped electrode portion 104, and a point B that is 5/8 as the outer peripheral distance. Are connected to each other, and these two main radiation electrode portions 105 function as a so-called dipole antenna.

  FIG. 3 is a diagram showing antenna impedance characteristics of the wireless tag according to the present invention, and shows the result of measurement using the wireless tag 100 described above. Reference numeral 701 denotes an impedance resistance, and reference numeral 702 denotes an impedance reactance.

  As a comparative example, antenna impedance characteristics were similarly measured using the wireless tag 200 shown in FIG.

  FIG. 2 is a diagram illustrating a wireless tag according to a comparative example.

  The wireless tag 200 is formed by joining an antenna portion 201 formed by etching aluminum and an IC chip 203 on a base material 202 made of PET by flip chip mounting. The antenna unit 201 includes two main radiation electrode units 205 and functions as a so-called dipole antenna.

  FIG. 4 is a diagram showing the antenna impedance characteristics of the wireless tag according to the comparative example, and shows the result of measurement using the wireless tag 200 described above. Reference numeral 703 denotes the impedance resistance, and reference numeral 704 denotes the impedance reactance.

  When the resistance of the antenna is Ra, the reactance is Xa, the resistance of the IC chip is Ri, and the reactance is Xi, the impedance matching conditions of the antenna and the IC chip are Ra = Ri, Xa = -Xi.

  The impedance (resistance component) 701 of the wireless tag 100 according to the present invention shown in FIG. 3 gradually increases as the frequency increases, but peaks at a certain point and gradually decreases again. Therefore, the difference between the resistance of the target IC chip and the resistance of the antenna can be reduced in a wide frequency band.

  The impedance (reactance) 702 maintains a value of 100 to 130Ω within the display band, and similarly, the difference between the target IC chip reactance and the antenna reactance can be reduced in a wide band. .

  In general, since the impedance of an IC chip has a small change depending on the frequency, it is possible to achieve impedance matching in a wide frequency band by a wireless tag having an antenna having such impedance characteristics.

  On the other hand, if the impedance of the antenna 703 and the impedance (reactance) 704 vary greatly depending on the frequency as in the comparative example shown in FIG. 4, the frequency bandwidth that can be matched is limited. .

  The effect and superiority of the present invention are clear when compared with the case where the impedance (reactance component) 704 of the comparative example changes with a value of less than 0Ω or more than 200Ω within the same frequency band.

  FIG. 5 is a diagram showing matching characteristics between the IC chip and the antenna according to the present invention and the comparative example.

  Reference numeral 801 denotes an antenna return loss viewed from an IC chip in the wireless tag 100 according to the present invention, and reference numeral 802 denotes an IC chip-antenna mismatch loss in the wireless tag 100. Similarly, reference numeral 803 denotes an antenna return loss viewed from the IC chip in the wireless tag 200 according to the comparative example, and reference numeral 804 denotes an IC chip-antenna mismatch loss in the wireless tag 200.

 Both the wireless tag 100 and the wireless tag 200 are designed to achieve impedance matching at 950 MHz, and the mismatch loss at 950 MHz is almost zero. However, at 850 MHz, for example, the mismatch loss 802 of the wireless tag 100 according to the present invention is 2.6 dB, whereas the mismatch loss 804 of the wireless tag 200 according to the comparative example is a difference between 7.8 dB and 5.2 dB. Has occurred.

  When this is converted into a communication distance, the wireless tag 100 of the present invention corresponds to 74% of the communication distance at the time of complete matching, whereas the wireless tag 200 of the comparative example reaches 40% of the communication distance at the time of complete matching. It means to deteriorate.

  When the communication distance was actually measured, in the case of the wireless tag 100 of the present invention, the communication distance at 950 MHz was 5 m, but the communication distance at 850 MHz was 4.2 m. On the other hand, in the wireless tag 200 of the comparative example, the communication distance at 950 MHz was also 5 m, but the communication distance at 850 MHz was remarkably deteriorated to 2.3 m.

(Example 2)
FIG. 6 is a diagram showing an embodiment of the present invention.

  The antenna portion 101 was formed on a substrate 102 made of PET by etching aluminum affixed on the base material 102, and the antenna portion 101 and the IC chip 103 were connected by flip chip mounting. The main radiation electrode portion 105 is connected so as to circumscribe the loop electrode portion 104 connected to the IC chip 103. Further, the main radiation electrode part 105 has a so-called folded structure with an open end curved, and has a folded part 107. A wireless tag 300 reduced in size with such a structure was manufactured.

  When the impedance characteristics of the antenna were measured using the wireless tag 300, characteristics similar to those of the wireless tag 100 according to the present invention shown in FIG. 3 were shown for resistance and reactance.

(Example 3)
FIG. 7 is a diagram showing an embodiment of the present invention.

  The wireless tag 400 has the same configuration as that of the second embodiment except for the shape of the main radiation electrode portion 105. The main radiation electrode portion 105 is provided with a fan-shaped wide portion 109 at the tip, that is, the open end.

  FIG. 8 is a diagram showing antenna impedance characteristics of the wireless tag according to the present invention, and shows the results of measurement using the wireless tag 300 and the wireless tag 400 described above. Reference numeral 901 represents the impedance resistance of the wireless tag 300, reference numeral 902 represents the impedance reactance of the wireless tag 300, reference numeral 903 represents the impedance resistance of the wireless tag 400, and reference numeral 904 represents the impedance reactance of the wireless tag 400.

  Compared with the wireless tag 300, the wireless tag 400 provided with the wide portion 109 in the main radiation electrode portion 105 has a flatter impedance characteristic, particularly a reactance component 904. Therefore, by forming such a wide portion, a wireless tag capable of impedance matching with the IC chip in a wider frequency band can be obtained.

Example 4
FIG. 9 is a diagram illustrating a wireless tag and antenna impedance characteristics of a comparative example. FIG. 9A is a diagram illustrating the wireless tag 500, and FIG. 9B is a diagram illustrating antenna impedance characteristics of the wireless tag 500. 10A and 10B are diagrams illustrating the wireless tag and the antenna impedance characteristics of the present invention. FIG. 10A is a diagram illustrating the wireless tag 600, and FIG. 10B is a diagram illustrating the antenna impedance characteristics of the wireless tag 600. 11A and 11B are diagrams showing the wireless tag and antenna impedance characteristics of the present invention. FIG. 11A shows the wireless tag 100 of the present invention shown in Example 1, and FIG. It is a figure which shows an antenna impedance characteristic.

  The wireless tag 500 and the wireless tag 600 have the same configuration as that of the first embodiment except for a position where the main radiation electrode unit 105 and the loop electrode unit 104 are connected (hereinafter referred to as a connection point). Reference numerals 701 and 901 denote resistances of the antenna impedance, and reference numerals 702 and 902 denote reactances of the antenna impedance.

  The connection point of the wireless tag 500 according to the comparative example is located at a distance of 1/8 and 7/8 of the entire length of the loop electrode portion 104 from the feeding point 106, and the impedance in the illustrated frequency band. The change in (reactance) 902 is large.

  The connection point of the wireless tag 600 according to the present invention is located at a distance of one-fourth and three-fourths of the total length of the loop electrode portion 104 from the feeding point 106, and the impedance in the frequency band shown in the figure. The change in (reactance) 702 is smaller than that of the wireless tag 500 and is starting to flatten.

  The connection point of the wireless tag 100 according to the present invention is located at a distance of 3/8 and 5/8 of the entire length of the loop electrode portion 104 from the feeding point 106, and the impedance in the frequency band shown in the figure. The change in (reactance) 702 is sufficiently smaller than that of the wireless tag 500 and is further flattened compared to the wireless tag 600.

  From the above comparison, when the connection point of the wireless tag is located at a distance of one-fourth to three-fourths of the entire length of the loop electrode portion from the feeding point, impedance characteristics, particularly reactance, in a certain frequency band are obtained. It became clear that the minute change was small, flattened, and easy to achieve impedance matching in a wide frequency band.

  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, it goes without saying that the present invention also includes various variations and modifications that would be obvious to those skilled in the art.

  By using the wireless tag of the present invention, the material and use of the articles to be managed in the management of various articles represented by distribution management, sales management, inventory management, usage status management, etc., especially for general goods that are compatible with import / export A system suitable for the environment can be easily constructed.

The figure which shows the Example of this invention. The figure which shows the wireless tag by a comparative example. The figure which shows the antenna impedance characteristic of the radio | wireless tag by this invention. The figure which shows the antenna impedance characteristic of the wireless tag by a comparative example. The figure which shows the matching characteristic of IC chip and an antenna by this invention and a comparative example. The figure which shows the Example of this invention. The figure which shows the Example of this invention. The figure which shows the antenna impedance characteristic of the radio | wireless tag by this invention. The figure which shows the radio | wireless tag and antenna impedance characteristic of a comparative example. FIG. 9A illustrates a wireless tag, and FIG. 9B illustrates antenna impedance characteristics of the wireless tag. The figure which shows the radio | wireless tag and antenna impedance characteristic of this invention. FIG. 10A illustrates a wireless tag, and FIG. 10B illustrates antenna impedance characteristics of the wireless tag. The figure which shows the radio | wireless tag and antenna impedance characteristic of this invention. FIG. 11A is a view showing the wireless tag of the present invention shown in Embodiment 1, and FIG. 11B is a view showing antenna impedance characteristics of the wireless tag.

Explanation of symbols

100, 200, 300, 400, 500, 600 Wireless tag 101, 201 Antenna portion 102, 202 Base material 103, 203 IC chip 104 Loop electrode portion
105, 205 Main radiation electrode parts 106, 206 Feed point 107 Folding part 109 Wide parts 701, 703, 901, 903 Impedance (resistance)
702, 704, 902, 904 Impedance (for reactance)
801, 803 Return loss 802, 804 Mismatch loss A Point that is 3/8 as the outer peripheral distance B Point that is 5/8 as the outer peripheral distance

Claims (6)

  A wireless tag having at least an IC chip and an antenna portion, wherein the antenna portion has a loop electrode having a feeding point formed by connecting the IC chip, and a main electrode having an open end extending from the loop electrode. A wireless tag comprising a radiation electrode, wherein the main radiation electrode is extended and connected from a position that is one-fourth to three-fourths of the total length of the loop electrode from the feeding point.   2. The wireless tag according to claim 1, wherein the main radiation electrode is formed in a linear shape.   The wireless tag according to claim 1, wherein the main radiation electrode is formed in a curved shape.   The wireless tag according to claim 1, wherein the main radiation electrode has a wide portion at the open end.   The wireless tag according to claim 1, wherein two main radiation electrodes are formed.   The wireless tag according to any one of claims 1 to 5, wherein the loop electrode and the main radiation electrode are arranged to be line-symmetric.

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